August 2020 Monthly Permafrost Alert (PMA) Program

The U.S. Permafrost Association is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute, with support from the National Science Foundation, has "migrated" the previous Cold Regions Bibliography to a new platform. Included are the US Permafrost Association supported Monthly Permafrost Alerts dating back to 2011. The Bibliography is searchable at : www.coldregions.org.

Entries in each category are listed in chronological order starting with the most recent citation.

The August Alert contains 134 citations from the 2020 meeting of the European Geosciences Union General Assembly. Another 84 citations from this meeting appeared in the July Alert.

The individual Monthly Permafrost Alerts are found on the US Permafrost Association website : http://www.uspermafrost.org/monthly-alerts.shtml.

2020 Permafrost Alert Sponsors

Arctic Foundations, Inc.
GW Scientific
Campbell Scientific Inc.

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SERIAL REFERENCES

2020062966 Bowen, Jennifer C. (University of Michigan, Department of Earth and Environmental Sciences, Ann Arbor, MI); Ward, Collin P.; Kling, George W. and Cory, Rose M. Arctic amplification of global warming strengthened by sunlight oxidation of permafrost carbon to CO2: Geophysical Research Letters, 47(12), Paper no. e2020GL087085, illus. incl. 1 table, 39 ref., June 28, 2020.

Once thawed, up to 15% of the ~1,000 Pg of organic carbon (C) in arctic permafrost soils may be oxidized to carbon dioxide (CO2) by 2,100, amplifying climate change. However, predictions of this amplification strength ignore the oxidation of permafrost C to CO2 in surface waters (photomineralization). We characterized the wavelength dependence of permafrost dissolved organic carbon (DOC) photomineralization and demonstrate that iron catalyzes photomineralization of old DOC (4,000-6,300 a BP) derived from soil lignin and tannin. Rates of CO2 production from photomineralization of permafrost DOC are twofold higher than for modern DOC. Given that model predictions of future net loss of ecosystem C from thawing permafrost do not include the loss of CO2 to the atmosphere from DOC photomineralization, current predictions of an average of 208 Pg C loss by 2,299 may be too low by ~14%. Abstract Copyright (2020). The Authors.

DOI: 10.1029/2020GL087085

2020063318 Conaway, Christopher H. (U. S. Geological Survey, Menlo Park, CA); Johnson, Cordell D.; Lorenson, Thomas D.; Turetsky, Merritt; Euskirchen, Eugenie; Waldrop, Mark P. and Swarzenski, Peter W. Permafrost mapping with electrical resistivity tomography; a case study in two wetland systems in interior Alaska: Journal of Environmental & Engineering Geophysics, 25(2), p. 199-209, illus., 47 ref., June 1, 2020.

Surface-based 2D electrical resistivity tomography (ERT) surveys were used to characterize permafrost distribution at wetland sites on the alluvial plain north of the Tanana River, 20 km southwest of Fairbanks, Alaska, in June and September 2014. The sites were part of an ecologically-sensitive research area characterizing biogeochemical response of this region to warming and permafrost thaw, and the site contained landscape features characteristic of interior Alaska, including thermokarst bog, forested permafrost plateau, and a rich fen. The results show how vegetation reflects shallow (0-10 m depth) permafrost distribution. Additionally, we saw shallow (0-3 m depth) low resistivity areas in forested permafrost plateau potentially indicating the presence of increased unfrozen water content as a precursor to ground instability and thaw. Time-lapse study from June to September suggested a depth of seasonal influence extending several meters below the active layer, potentially as a result of changes in unfrozen water content. A comparison of several electrode geometries (dipole-dipole, extended dipole-dipole, Wenner-Schlumberger) showed that for depths of interest to our study (0-10 m) results were similar, but data acquisition time with dipole-dipole was the shortest, making it our preferred geometry. The results show the utility of ERT surveys to characterize permafrost distribution at these sites, and how vegetation reflects shallow permafrost distribution. These results are valuable information for ecologically sensitive areas where ground-truthing can cause excessive disturbance. ERT data can be used to characterize the exact subsurface geometry of permafrost such that over time an understanding of changing permafrost conditions can be made in great detail. Characterizing the depth of thaw and thermal influence from the surface in these areas also provides important information as an indication of the depth to which carbon storage and microbially-mediated carbon processing may be affected.

DOI: 10.2113/JEEG19-091

2020060576 Paquette, Michel (Queen's University, Department of Geography and Planning, Kingston, ON, Canada); Rudy, Ashley C. A.; Fortier, Daniel and Lamoureux, Scott F. Multi-scale site evaluation of a relict active layer detachment in a High Arctic landscape: Geomorphology, 359, Paper no. 107159, illus. incl. sects., 1 table, sketch maps, 62 ref., June 15, 2020.

Investigations into the susceptibility of permafrost landscapes response to thermokarst can be performed using various approaches, depending on the scale of investigation. In many cases, point-based field measurements are extrapolated to larger scales and vice versa. The integration of scales often requires some form of ground control in addition to remote sensing surveys, which are at times exclusively conducted. As upscaling from discrete field measurements can provide spatial coverage and landscape-scale significance, downscaling from remote sensing can offer insight into processes and serve as calibration or verification. Here we present a multiple-scale evaluation of an area initially interpreted as a relict active layer detachment slide (before 1950) on Melville Island in the High Arctic, where differential interferometric synthetic aperture radar (DInSAR) showed subsidence between 2013 and 2015. Ground-based, cryostratigraphy measurements were combined with ground-penetrating radar (GPR) to investigate permafrost ice-content. The results indicate greater subsidence within the relict active layer detachment as detected by DInSAR. GPR surveys and permafrost coring indicated the presence of an ice-rich or massive ice layer near the base of the active layer in this area. In addition, cryostratigraphic evidences of thaw unconformity and of massive ice depth helped validate the interpretations of the geomorphology in the active layer detachment. This combination of methods indicated a localized and inherited landform-subsidence association, which brought further insight into the interpretation of DInSAR subsidence data. The framework presented in this study demonstrates the importance of site-specific investigations of thermokarst signal in order to understand the processes behind the remote sensing results.

DOI: 10.1016/j.geomorph.2020.107159

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CONFERENCE REFERENCES

2020063121 Anderson, Leif (GFZ, German Research Centre For Geosciences, Potsdam, Germany) and Scherler, Dirk. Geomorphic feedbacks on the moraine record [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19935, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Glacial moraines represent one of the most spatially diverse climate archives on earth. Moraine dating and numerical modeling are used to effectively reconstruct past climate from mountain ranges at the global scale. But because moraines are often located downvalley from steep mountain headwalls, it is possible that debris-covered glaciers emplaced many moraines preserved in the landscape today. Before we can understand the effect of debris cover on the moraine recored we need to understand how debris modulates glacier response to climate change. To help address this need, we developed a numerical model that links feedbacks between mountain glaciers, climate change, hillslope erosion, and landscape evolution. Our model uses parameters meant to represent glaciers in the Khumbu region of Nepal, though the model physics are relevant for mountain glaciers elsewhere. We compare simulated debris-covered and debris-free glaciers and their length evolution. We explore the effect of climate-dependent hillslope erosion. We also allow temperature change to control frost cracking and permafrost in the headwall above simulated glaciers. Including these effects holds special implications for glacial evolution during deglaciation and the long-term evolution of mountain landscapes. Because debris cover suppresses melt, debris-covered glaciers can advance independent of climate change. When debris cover is present during cold periods, moraine emplacement can lag debris-free glacier moraine emplacement by hundreds of years. We develop a suite of tools to help determine whether individual moraines were formed by debris-covered glaciers. Our analyses also point to how we might interpret moraine ages and estimate past climate states from debris-perturbed settings. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19935

2020063091 Ardelean, Florina (West University of Timisoara, Timisoara, Romania); Chetan, Marinela; Dornik, Andrei; Onaca, Alexandru; Georgievski, Goran; Drozdov, Dmitry; Romanovsky, Vladimir; Hagemann, Stefan; Nicolsky, Dmitry and Sein, Dmitry. Recent landscape changes assessed by remotely sensed data in Pechora region [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17819, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Pechora Region, located in North-East European Russia, is a unique natural environment with high biodiversity and wilderness areas, such as coastal habitats, the Arctic tundra or the Ural Mountains. The area lies on different permafrost zones and faces considerable challenges such as the over-exploitation of natural resources or climate change related. Our objective is to analyze landscape changes in the last 30 years using free available satellite data and identify possible influences on the degradation of permafrost in the study area. We used Surface Reflectance images from Landsat archive between 1985 and 2019. For each year, normalized indices were derived, illustrating consistency of green vegetation, as Normalized Difference Vegetation Index (NDVI), and vegetation moisture, Normalized Difference Moisture Index (NDMI). From MODIS data archive we used land surface temperature (LST), between 2000 and 2019. Moreover, the Global Surface Water dataset which contains maps with the spatial and temporal distribution of permanent and seasonal surface water from 1984 to 2018 was used. These data were aggregated to yearly mean (i.e. NDVI, NDMI, LST) or yearly sum (surface water), for the entire Pechora region. The results reveal a significant increase in NDVI mean. This "greening" of the tundra landscape, especially the southern tundra, between 1985 and 2019 has also been highlighted in other studies in the Arctic. Similarly, NDMI shows a slight increase of vegetation moisture in this area in the last three decades. Vegetation dynamics in the last 20 years is in accordance with LST evolution, showing an increase especially in the August mean temperature, more significant after 2011. From the analysis of the spatio-temporal changes of the water surfaces, a significant increase in seasonal water can be observed after 1997, and a relatively stable trend of permanent waters, with minimum values in 1999, 2003 and 2012. In the same time, an increase in the active layer thickness in the last 20 years of measurements in a site located in the study area has been documented. We conclude that Pechora Region experienced significant landscape changes in the last 30 years, our results showed mostly positive changes on vegetation consistency and moisture, and a high spatial variability of surface water. Acknowledgement: This work is funded for WUT by a grant of the Romanian National Authority for Scientific Research and Innovation, CCDI-UEFISCDI, project number ERANET-RUS-PLUS-SODEEP, within PNCD III in the frame of ERA-Net plus Russia, TSU is supported by MOSC RF 4.587.21.0048(RFMEFI58718X0048), AWI and HZG are supported by BMBF (Grant no. 01DJ18016A and 01DJ18016B). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17819

2020063118 Aref, Mohammad M. (Potsdam University, Institute of Geosciences, Potsdam, Germany); Bookhagen, Bodo; Smith, Taylor T. and Strecker, Manfred R. Seasonal active landsliding and hillslope activity in the southern Central Andes of NW Argentina [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19679, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The eastern Central Andes of northwestern Argentina is characterized by a steep topographic gradient with elevations ranging from 1000 m in the foreland to more than 6000 m in the eastern Andean Cordillera. This setting furthermore shows high topographic relief with deeply incised river valleys that are frequently impacted by strong rainfall events driven by the South American monsoon. Additionally, a strong vegetation cover contrast from dense coverage in the low elevation foreland to sparse coverage at high elevation defines the environmental gradient in this area. This area is impacted by several types of hillslope instabilities and landsliding: at some high elevations above 5000 m hillslope instability are related to solifluction processes, whereas shallow and deep seated landsliding affect geologically preconditioned areas. Here we use a combination of different radar sensors and wavelengths to describe the 3D deformation signal of instable hillslopes: TerraSAR-X, Sentinel-1, and ALOS2. To mitigate the tropospheric delay from InSAR measurements, phase-based and weather model approaches are applied to improve the spatial and temporal variations of displacement signals. We use persistent and small baseline subsets (SBAS) category of distributed scatterer approaches to derive deformation fields and we invert for 3D deformation fields using several look angles in combination with GNSS data under different assumptions including that the horizontal component has a motion parallel to the downhill slope. We analyze Line-of-sight (LOS) time series and combine deformation fields with temperature and rainfall measurements to better understand driving forces of high-elevation hillslope instabilities We describe two deep-seated landslides with downslope velocities exceeding 5-10 cm/yr and we exploit image-cross correlation techniques of optical data to monitor seasonal and inter-annual changes. The periodic changes of InSAR deformation and temperature time series show freeze-thaw processes of the active layer thickness of the permafrost areas at elevations exceeding 5000 m. We document that deep-seated, fast moving landslides are related to geologic preconditioning. The combination of SAR and optical approaches helps to describe hillslope regimes in steep and difficult to access terrain. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19679

2020063007 Bartsch, Annett (Austrian Polar Research Institute, Vienna, Austria). Data collections of ESA due GlobPermafrost and ESA CCI+ permafrost [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9543, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

A Permafrost Information System (PerSys) based on satellite data has been setup as part of the ESA DUE GlobPermafrost project (2016-2019, www.globpermafrost.info). This includes a data catalogue as well as a WebGIS, both linked to the Pangaea repository for easy data access. The thematic products available include InSAR-based land surface deformation maps, rock glacier velocity fields, spatially distributed permafrost model outputs, land surface properties and changes, and ground-fast lake ice. Extended permafrost modelling (time series) is implemented in the new ESA CCI+ Permafrost project (2018-2021, URL: http://cci.esa.int/Permafrost), which will provide the key for our understanding of the changes of surface features over time. Special emphasis in CCI+ Permafrost is on the evaluation and development of land surface models to gain better understanding of the impact of climate change on permafrost and land-atmosphere exchange. Additional focus will be on documentation of kinematics from rock glaciers in several mountain regions across the world supporting the International Permafrost Association (IPA) action group "rock glacier kinematics as an essential climate variable". We will present the Permafrost Information System including the time series (2003-2017) of the first version of ground temperatures and active layer thickness for the entire Arctic from the ESA CCI+ Permafrost project. Further on, details on the user requirements collection process will be provided. Ground temperature is calculated for 0, 1m, 2m, 5m, and 10 m depth and has been assessed based on a range of borehole data. A survey regarding data repositories containing for validation relevant borehole data has been conducted. The records have been evaluated for the project purpose and harmonized. The resulting database will be eventually also made publicly available.

DOI: 10.5194/egusphere-egu2020-9543

2020062998 Beckebanze, Lutz (Universität Hamburg, Institute of Soil Science, Hamburg, Germany); Walz, Josefine; Runkle, Benjamin R. K.; Holl, David; Fedorova, Irina V.; Helbig, Manuel and Kutzbach, Lars. Lateral carbon export from polygonal tundra catchments on Samoylov Island, Lena River delta [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8991, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost-affected soils contain a large quantity of soil organic carbon (SOC). Two processes control the amount of carbon stored in soils. The photosynthetic activity of plants produces biomass that may accumulate in the soil, while microorganism's respiration leads to a depletion of the soil carbon stocks through decomposition. The carbon balance defines whether a soil acts as a source or sink of carbon. In recent decades, many researchers observed and analyzed the carbon balance of permafrost soils. In most cases, the focus lays on observations of the vertical carbon flux (CO2 and CH4) to estimate the carbon balance. However, there is lack of information regarding the lateral losses of carbon via dissolved organic carbon (DOC) or dissolved inorganic carbon (DIC) in ground- or rainwater. In this study, we estimate the lateral carbon fluxes from a permafrost-affected site in northeastern Siberia, Russia. Long-term measurements of vertical carbon fluxes have been conducted at this study site. By considering both, the vertical and the lateral carbon fluxes, we estimate the complete carbon balance for one growing season in 2014 and discuss the contribution of the lateral carbon flux to the overall carbon balance. The results show that the vertical CO2 fluxes dominate the carbon balance during the growing season from June 8th - September 8th (-19 ± 1.2 kg-C m-2). The lateral fluxes of DOC and DIC reached values of +0.1 ± 0.01 and +1.4 ± 0.09 kg-C m-2, respectively, whereas the vertical fluxes of CH4 had values of +0.7 ± 0.02 kg-C m-2 integrated over this time. By considering the lateral carbon export, the net ecosystem carbon balance of the study area was reduced by 8%. On shorter time scales of days, the relationship between lateral and vertical flux changes within the growing season. Early in the growing season, the lateral carbon flux outpaces the weak vertical CO2 uptake for a few days and converts the estimated carbon balance from a sink to a source. We conclude that lateral carbon fluxes have a larger influence on the carbon balance of our study site on time scales of days (early and late growing season) and that this influence decreases with annual time scales. Therefore, the vertical carbon flux can be seen as a good approximation for the carbon balance of this study site on annual time scales. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8991

2020063131 Bedington, Michael (Plymouth Marine Laboratory, Plymouth, United Kingdom); Torres, Ricardo; Polimene, Luca; Mann, Paul and Strauss, Jens. Modelling the impact of changing riverine permafrost input on an Arctic coastal ecosystem [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20689, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic ocean receives 11% of the global river discharge and the Arctic rivers drain large permafrost rich catchments. Where these rivers outflow into the marginal shelf seas of the Arctic ocean the terrestrial dissolved organic matter (tDOM) which they transport has an important role to play in the coastal ecosystem. This tDom is derived from inland permafrost and as it thaws under future climate scenarios there are expected to be changes to both the composition and quantity of riverine tDOM. At the same time there will be changes to the seasonality and magnitude of river discharge, due to increased precipitation and earlier snow melt, and to the light availability, due to reduced seasonal sea ice. To understand the possible impact of these changes on the coastal ecosystem it is important to understand the present role of permafrost derived tDOM and the possible changes to the nearshore circulation. We model the hydrodynamics of the extensive shallow shelf of the Laptev sea, into which drains the Lena river - the 13th largest in the world by discharge. The output from the hydrodynamic model is used to drive the ecosystem model ERSEM which has been adapted to explicitly include a permafrost tDOM input. This coupled model system allows us to investigate both the role of present day tDOM in an Arctic coastal ecosystem and to hypothesise on the impact of increases in future. In particular we attempt to quantify the efficacy of the microbial carbon pump under different tDOM inputs. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20689

2020063039 Bergstedt, Helena (University of Alaska Fairbanks, Institute of Northern Engineering, Water and Environmental Research Center, Fairbanks, AK); Jones, Benjamin; Walker, Donald; Farquharson, Louise; Breen, Amy and Hinkel, Kenneth. Mapping lake drainage and drained lake basins around Point Lay, Alaska using multi-source remote sensing data [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11919, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The North Slope of Alaska is a permafrost affected landscape dominated by lakes and drained lake basins of different sizes, depths and ages. Local communities across the North Slope region rely on lakes as a fresh water source and as locations for subsistence fishing, while industry relies on lakes as a source of water for winter transportation. Lake drainage events are often disruptive to both communities and industry that rely on being in close proximity to surface water sources in a region underlain by continuous permafrost. Drained lake basins of different ages can provide information on the past effects of climate change in the region. Studying past drainage events gives insight about the causes and mechanisms of these complex systems and benefits our understanding of lake evolution on the Arctic Coastal Plain in Alaska and the circumpolar Arctic as a whole. Lakes and drained lake basins can be identified using high to medium resolution multispectral imagery from a range of satellite-based sensors. We explore the history of lake drainage in the region around Point Lay, a community located on the northern Chukchi Coast of Alaska, using a multi-source remote sensing approach. We study the evolution of lake basins before and after drainage events, their transformation from fishing grounds and water sources to grazing grounds and the geomorphological changes in the surrounding permafrost-dominated landscapes associated with these transitions. We build a dense and long time series of satellite imagery of past lake drainage events by including a multitude of remote sensing acquisitions from different sources into our analysis. Incorporating imagery from different sensors that have different temporal and spatial resolutions allows us to assess past drainage events and current geomorphological states of lakes and drained lake basins at different temporal and spatial scales. Point Lay is known to be an area where drainage events occur frequently and are of high relevance to the community. In August of 2016, the village drinking water source drained during a period of intense rainfall causing the village to seek alternative sources for a freshwater supply. Our results from the analysis of the remotely sensed imagery were shared directly with the community as part of a public seminar series in the Spring of 2020. We hope that results from our study near Point Lay, Alaska can contribute towards the selection of a new freshwater source lake for the village. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11919

2020063115 Bolch, Tobias (University of Zurich, Department of Geography Department, Zurich, Switzerland); Rastner, Philipp; Pronk, Jan Bouke; Bhattacharya, Atanu; Liu Lin; Hu Yan; Zhang Guoqing and Yao Tandong. Occurrence and characteristics of ice-debris landforms in Poiqu Basin (central Himalaya) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19637, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rock glaciers and other ice-debris landforms (I-DLs) are an important part of the debris-transport system in high mountains and their internal ice could provide a relevant contribution to water supply especially in dry regions. Recent research has shown that I-DLs are abundant in High Mountain Asia, but knowledge about their occurrence and characteristics is still limited. We are therefore investigating I-DLs in the Poiqu basin (~28°17N, 85°58E) - central Himalaya/southern Tibetan Plateau using remote sensing aided by field observations. We use very high-resolution stereo Pleiades data from the contemporary period and stereo Corona and Hexagon data from the 1970s to generate digital elevation models, applied satellite radar interferometry based on ALOS-1 PALSAR and Sentinel-1 SAR data and feature tracking using Sentinel-2 and the Pleiades data. Generated DEMs allowed us to create a hillshade to support identification, to derive their topographical parameters and to investigate surface elevation changes. I-DLs were identified and classified based on their characteristic shape, their surface structure and surface movement. Field observationssupported the identification of the landforms. We found abundant occurrence of rock glaciers (with typical characteristics like lobate-shaped forms, ridges and furrows as well as steep fronts) but also significant movements of both former lateral moraines and debris-slopes in permafrost area. Preliminary results revealed the occurrence of more than 350 rock glaciers covering an area of about 21 km2. About 150 of them are active. The largest rock glacier has an area of 0.5 km2 and three have an area of more than 0.3 km2. The rock glaciers are located between ~3715 m and ~5850 m with a mean altitude of ~5075 m a.s.l.. The mean slope of all rock glaciers is close to 17.5° (min. 6.8°, max. 37.6°). Most of the rock glaciers face towards the Northeast (19%) and West (18.5%). Surface elevation changes between the 1970s and 2018 show no significant changes but indicate slight elevation gain at the front of active rock glaciers caused by their downward movements. Work will be continued to generate an inventory of all I-DLs in the study area including information about their activity and surface elevation changes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19637

2020063080 Cao, Zuonan (University of Tuebingen, Department of Geosciences, Soil Science and Geomorphology, Tubingen, Germany); Kühn, Peter and Scholten, Thomas. Soil and vegetation feedbacks on climate change in high mountain ranges of the Tibetan Plateau; using near and mid-infrared spectroscopy (FT-NMIRS) in soil properties, phosphorus (P) as example [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17087, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Tibetan Plateau is the third-largest glaciated area of the world and is one of the most sensitive regions due to climate warming, such as fast-melting permafrost, dust blow and overgrazing in recent decades. In the past 50 years, the warming rate on the Tibetan Plateau is higher than the global average warming rate with 0.40 ± 0.05 °C per decade. The climate warming is most distinct in the northeastern Tibetan Plateau, implying increasing air and surface temperatures as well as duration and depth of thawing. The main ecological consequences are a disturbed vegetation cover of the surface and a depletion of nutrient-rich topsoils (Baumann et al., 2009, 2014) coupled with an increase of greenhouse gas emissions, mainly CO2 (Bosch et al., 2017). Due to the extreme environmental conditions resulting from the intense and rapid tectonic uplift, highly adaptive and sensitive ecosystem have developed, and the Plateau is considered to be a key area for the environmental evolution of Earth on regional and global scales, which is particularly sensitive to global warming (Jin et al., 2007; Qiu, 2008). Climate warming and land-use change can reduce soil organic carbon (SOC) stocks as well as soil nitrogen (N) and phosphorus (P) contents and soil quality. Many species showed their distributions by climate-driven shifts towards higher elevation. In Tibetan Plateau, however, the elevational variations of the alpine grassland are rare (Huang et al., 2018) and it is largely unknown how the grass line will respond to global warming and whether soils play a major role. With this research, the hypothesis is tested that soil quality, given by SOC, N and P stocks and content, is a driving factor for the position and structure of the grass line and that soil quality is one of the major controls of biodiversity and biomass production in high-mountain grassland ecosystems. A Fourier transformation near and mid-infrared spectroscopy (FT-NMIRS) should be used to measure soil P fractions rapid and for large numbers of soil samples, and analyze environmental factors, including temperature, precipitation, soil development, soil fertility, and the ability of plants to adapt to the environmental impact of climate using FT-NMIRS. We explored first near-infrared spectroscopy (NIRS) in soils from grassland on the Tibetan Plateau, northwestern China and extracted P fractions of 196 samples from Haibei Alpine Meadow Ecosystem Research Station, Chinese Academy of Sciences, at four depths increments (0-10 cm 10-20 cm 20-40 cm and 40-70 cm) with different pre-nutrient additions of nitrogen (N) an P. The fractionation data were correlated with the corresponding NIRS soil spectra and showed significant differences for depth increments and fertilizer amendments. The R2 of NIRS calibrations to predict P in traditional Hedley fractions ranged between 0.12 and 0.90. The model prediction quality was higher for organic than for inorganic P fractions and changed with depth and fertilizer amendment. The results indicate that using NIRS to predict the P fractions can be a promising approach compared with traditional Hedley fractionation for soils in alpine grasslands on the Tibetan Plateau. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17087

2020063000 Chen, Liangzhi (University of Helsinki, Department of Geosciences and Geography, Helsinki, Finland); Aalto, Juha and Luoto, Miska. Recent ground thermal dynamics and variations in northern Eurasia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9106, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Ground thermal regime in cold environments is key to understanding the effects of climate change on surface-atmosphere feedbacks. The northern Eurasia, covering over half of terrestrial areas north of 40°N, is sensitive to the ongoing climate change due to underlain permafrost and seasonal frost. Here, we quantify the recent ground thermal dynamics and variations over northern Eurasia by compiling measurements of soil temperature data over 457 sites at multiple depths from 1975-2016. Our analysis shows that the mean annual ground temperature has significant warming trends by 0.30-0.31 °C/decade at depths of 0.8, 1.6, and 3.2 m. We found that the changes in annual maximum ground temperatures were more pronounced than mean annual ground temperatures with a weakened warming magnitude (0.40 to 0.31°C/decade) from upper to lower ground. Our results also suggest the substantial differences in warming magnitudes through parameters and depths over different frost-related areas. The ground over continuous permafrost area warmed faster than non-continuous permafrost and seasonal frost areas in shallow ground (0.8 and 1.6 m depth) but slower in deeper ground (3.2 m). Our study highlights the varied ground temperature evolutions at multiple depths and different frost-related ground, suggesting the importance of separated discussions on different frost-affected ground in application and future research. Noteworthy, the results indicate that the significant ground warming can promote greenhouse gas emissions from soil to atmosphere, further accelerating climate change. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9106

2020063097 Cherepanova, Elena (Institute for Scientific Research of Aerospace Monitoring (AEROCOSMOS), State Scientific Institution, Russian Federation); Bondur, Valery; Zamshin, Viktor and Feoktistova, Natalia. Satellite-derived spatiotemporal patterns of environmental changes caused by 2018-2019 wildfires in Arctic-boreal Russia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18080, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Forest fires affect environmental changes both directly, changing the type of land cover, causing local and regional air pollution through emissions of greenhouse gases and aerosols, and indirectly through a secondary effect on atmospheric, soil and hydrological processes. The increase in the number and area of uncontrolled wildfires, the degradation of permafrost in high latitude areas leads to a change in the balance of greenhouse gases in the atmosphere, and it results in the negative impact on the Earth's climatic system. This study examined the Arctic-Boreal territories of the Russian Federation, where huge forest fires were observed in 2018-2019. In most of these areas, forest fire detection is carried out only by means of the satellite monitoring without aviation support. The sparsely populated and inaccessible territories are a major factor of the rapid spread of fires over large areas. Most of the forest areas in the region are so-called control zones, where the authorities may decide not to extinguish the fires if they do not threaten settlements and economic facilities, and consider the salvation of forests economically unprofitable. However, there is no reliable data on the environmental consequences of large forest fires in the Arctic-Boreal territories. Satellite monitoring of wildfires provides the detection of fire locations, an assessment of their area and burning time. In our study, we used various indices calculated from remote sensing data for the pre-fire and post-fire periods to identify the spatiotemporal patterns of environmental change caused by large wildfires. The Sentinel 5 TROPOMI time series have been analyzed for the short-term and long-term atmospheric composition anomalies detection caused by forest fires in the region. In the process of comparing the methane concentrations time series for the 2018-2019 fire seasons the constantly high values anomaly zones were found. We believe that these anomalies are resulting from Sentinel-5 CH4 algorithm constrains, which requires additional work on data validation with relation to the local conditions. The reported study was funded by RFBR, MOST (China) and DST (India) according to the research project No. 19-55-80021 [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18080

2020063148 Chernykh, Denis (Russian Academy of Sciences, Pacific Oceanological Institute, Russian Federation); Shakhova, Natalia; Kosmach, Denis; Ananiev, Roman; Salomatin, Aleksander; Yusupov, Vladimir; Sergienko, Valentin; Gustafsson, Orjan; Jakobsson, Martin; Mayer, Larry; Saluk, Anatoly; Dmitrevsky, Nikolay; Kurilenko, Arcady; Gershelis, Elena; Silionov, Vyacheslav; Lobkovsky, Leopold; Mazurov, Alexey and Semiletov, Igor. First quantitative estimation of growing methane release from the east Siberian Arctic seas; from a single flare to vast seepage area [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-22402, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Sustained release of methane (CH4) to the atmosphere from thawing Arctic permafrost may be a positive and significant feedback to climate warming. Atmospheric venting of CH4 from the East Siberian Arctic Shelf (ESAS) was recently reported to be on par with flux from the Arctic tundra; however, the future scale of these releases remains unclear. Here, based on results of our 12 years observations, we show that CH4 emissions from this shelf to be determined by the state of subsea permafrost degradation. Below we consider dramatically growing release from the area located out of known fault zones. First time, we observed CH4 emissions from this single flare in 2007 in the ESAS mid-shelf. During 2014-2018 we revisited this area several times aiming to investigate quantitatively changing CH4 ebullition. The data show transformation of a single CH4 flare in a significant seepage area. CH4 emissions from this area emerge from largely thawed sediments via strong flare-like ebullition, producing fluxes that are orders of magnitude greater than fluxes observed in background areas underlain by largely frozen sediments. We suggest that progression of subsea permafrost thawing is much faster not only downward, but also laterally which could result in a significant increase in CH4 emissions from the ESAS. This work was supported in part by grants from Russian Scientific Foundation (15-17-20032, 18-77-10004, 19-77-00067), grant from Russian Government (Grant No. 14, Z50.31.0012/03.19.2014) and Tomsk Polytechnic University Competitiveness Enhancement Program grant, Project Number TPU CEP_SESE-299\2019. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-22402

2020063047 Christ, Andrew (University of Vermont, Department of Geology, Burlington, VT); Bierman, Paul; Dahl-Jensen, Dorthe; Steffensen, Jorgen; Peteet, Dorothy; Thomas, Elizabeth; Cowling, Owen; Steig, Eric; Corbett, Lee; Schaefer, Joerg; Hidy, Alan; Caffee, Marc; Rittenour, Tammy; Tison, Jean-Louis; Blard, Pierre-Henri; Protin, Marie and Southon, John. Camp Century ice core basal sediments record the absence of the Greenland ice sheet within the last million years [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12243, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Greenland Ice Sheet (GrIS) is melting in response to a rapidly warming climate. It is imperative to understand GrIS sensitivity to past climate, especially during periods when the ice sheet was smaller than present or possibly absent. The Camp Century ice core from NW Greenland, collected in 1966 and the first ice core to be drilled to the bed of the GrIS, revolutionized our understanding of global paleoclimate since 125 ka. However, basal sediment from the ice core was not fully explored and then sat in storage for decades - until it was re-discovered two years ago. We are now investigating these unique samples from the sub-glacial environment using modern analyses. Here, we present initial results from two samples, the upper and lower portions of >4 m of basal sediment. We applied an array of geochemical analyses to characterize paleoenvironment (lipid biomarkers, d13C, d15N), to infer past climatic conditions (d18O, dD) from frozen pore water, and to determine the exposure and burial history of the sediments below the ice sheet (optically stimulated luminescence [OSL], cosmogenic 10Be, 26Al, and 21Ne). The sub-glacial sediment consists of poorly sorted, reddish-brown, quartz-rich diamict, with paleo-permafrost features in some layers. This material contains woody macrofossils, fungal sclerotia (Cenococcum geophilum), and mosses (Tomenthypnum nitens, Polytrichum juniperinum) that yield a 14C age >55 ka. Woody tissue from the upper and lower samples yield stable d13C ratios of -26.7±0.1 ppm and -29.6±0.1 ppm and d15N ratios of 2.4±0.8 ppm and -2.3±0.8 ppm. Leaf wax (n-alkanoic acid) distributions are similar to modern Arctic shrubs. Frozen pore water yielded d18O ratios of -23.06±0.08 ppm and -21.49±0.08 ppm, enriched relative to all overlying ice (<-27 ppm). Deuterium-excess values are 4.3±0.8 ppm and 13.4±0.4 ppm, respectively. These stable isotope measurements of pore water suggest snowfall precipitation at temperatures similar to today if the site were ice-free. OSL measurements from the lower sediment suggest a minimum depositional age >600 ka. In situ 10Be concentrations in quartz decrease with depth from 7.7±0.1 x104 atoms/g (500-850 mm) and 6.6±0.2 x104 (250-500 mm) in the upper sediment to 1.6±0.1 x104 atoms/g (500-850 mm) and 1.8±0.1 x104 (250-500 mm) in the lower sediment. The 26Al/10Be ratio also decreases with depth. In the upper sediment, 26Al/10Be ratios range between 4.2 and 4.9 indicating > 900 ka of burial. In the lower sediment, 26Al/10Be ratios range from 1.4 to 2.0 indicating >2 Ma of burial. Measured 21 Ne/10Be ratios in quartz exceed 1000, which could indicate long-term burial and/or the presence of nucleogenic 21Ne. These results demonstrate that Camp Century basal sediment was exposed under ice-free conditions that supported vegetation similar to today. Cosmogenic data indicate the deeper sediment has been buried for most of the Pleistocene and the OSL date rules out surface exposure of the deeper material at MIS 11. Cosmogenic analysis indicates that the upper sample experienced less burial or more recent re-exposure. These data are consistent with a growing body of evidence indicating a dynamic Pleistocene GrIS, even under a pre-industrial climate system in which atmospheric CO2 concentrations did not exceed ~300 ppm. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12243

2020062996 Cohen, Denis (New Mexico Institute of Mining and Technology, Earth and Environmental Science, Socorro, NM); Zwinger, Thomas; Koskinen, Lasse and Karvonen, Tuomo. Long-term coupled permafrost-groundwater interactions at Olkiluoto, Finland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8972, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Understanding permafrost development and its effect on groundwater flow patterns and fluxes in the event of future ice-age conditions is important for the long-term safety of spent nuclear fuel repositories. To assess the evolution of permafrost thickness, talik development, and groundwater flow and salinity changes at Olkiluoto, Finland, during the next 100,000 years, we solve Darcy flow coupled to heat and solute transport in three dimensions in a rectangular block representing an area of 8.8 km by 6.8 km, and down to a depth of 10 km. The set of equations is based on continuum thermo-mechanic principles. Important and highly non-linear coupling processes such as the exponential decrease of permeability with ice content in soils and rocks, solute rejection during freezing, and variable-density Darcy flow are fully taken into account. Model equations are solved using the finite element method implemented in the open source software Elmer. High-resolution data of rock and soil permeability, thermal and physical properties, are mapped onto a 30-meter resolution grid resulting in a system of about 5 million nodes and 5 million elements. Soil layers at the surface are vertically resolved down to 0.1 meter. High contrast in permeability over short distances (from soil to granitic bedrock) make the system of equations challenging to solve numerically. Simulations are driven by RCP 4.5 climate scenario that predicts cold periods between AD 47,000 and AD 110,000. Surface boundary condition for temperature is calculated based on freezing and thawing n-factors that depend on monthly temperatures and the topographic wetness index that defines different zones of vegetation and ground cover. The thickness evolution of the six upper soil layers, including peat, above the granitic bedrock is also taken into account. Preliminary simulations are able to represent permafrost development at a high spatial resolution with evidence of important feedbacks due to permeable soil layers and faults in the bedrock that focus groundwater flow and solute transport. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8972

2020063134 Courtin, Jeremy (Alfred-Wegener-Institute Helmholtz-Center for Polar and Marine Research, Polar Terrestrial Environmental Systems, Potsdam, Germany); Perfumo, Amedea; Stoof-Leichsenring, Kathleen and Herzschuh, Ulrike. Characterisation of east Siberian paleodiversity based on ancient DNA analyses of the Batagay megaslump exposure [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21041, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With the ongoing Arctic warming, permafrost thaw accelerated during the last decade as much as it is now a global concern for biodiversity loss, food webs and biogeochemical cycling. This rapid permafrost degradation forms features such as massive retrogressive thaw slumps that give access to exceptional records for Quaternary biodiversity change investigations. The Batagay megaslump located in northern Yakutia, East Siberia, is the world's largest thawslump known to date, and along its ~55 m high headwall it gives access to Late and Mid Pleistocene permafrost deposits up to more than 500 kyrs in age. During an expedition to this unique site in 2017, sediment samples were collected with ages from more than 500 kyrs to modern time for the analysis of ancient DNA (aDNA). Our aim is to characterise the biodiversity and changes over geological timescales of this region in East Siberia. Using the aDNA extracted from these ancient environmental samples, we first performed a metabarcoding analysis (chloroplast trnL) to investigate past vegetation composition. We then performed a shotgun metagenomic analysis, which enabled a much higher depth of sequence data and allowed us to access the entire biodiversity, from Eukaryotes to Prokaryotes, Archaea and Viruses. This approach opened up new horizons, making it possible not only to investigate biodiversity composition and changes but also to infer on potential interactions across taxa and kingdoms. Both methods together allowed comparison and ensured robustness of the results obtained. We present here one of the very first studies done on the global, past and modern, biodiversity of permafrost regions which holds an enormous potential to reveal new insights into the evolution of this fragile ecosystem. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21041

2020063082 Dean, Joshua (University of Liverpool, School of Environmental Sciences, Liverpool, United Kingdom); Meisel, Ove; Roscoe, Melanie Martyn; Marchesini, Luca Belelli; Garnett, Mark; Lenderink, Henk; van Logtestijn, Richard; Borges, Alberto; Bouillon, Steven; Lambert, Thibault; Röckmann, Thomas; Maximov, Trofim; Petrov, Roman; Karsanaev, Sergei; Aerts, Rien; van Huissteden, Jacobus; Vonk, Jorien and Dolman, Han. Siberian Arctic inland waters emit mostly contemporary carbon [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17416, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Inland waters (rivers, lakes and ponds) are important conduits for the emission of terrestrial carbon in Arctic permafrost landscapes. These emissions are driven by turnover of contemporary terrestrial carbon and additional "pre-aged" (Holocene and late-Pleistocene) carbon released from thawing permafrost soils, but the magnitude of these source contributions to total inland water carbon fluxes remains unknown. Here we present unique simultaneous radiocarbon age measurements of inland water CO2, CH4 and dissolved and particulate organic carbon in northeast Siberia during summer. We show that >80% of total inland water carbon emissions were contemporary in age, but that pre-aged carbon contributed >50% at sites strongly affected by permafrost thaw. CO2 and CH4 were younger than dissolved and particulate organic carbon, suggesting emissions were primarily fuelled by contemporary carbon decomposition. The study region was a net carbon sink (-876.9 ± 136.4 Mg C for 25 July to 17 August), but inland waters were a source of contemporary (16.8 Mg C) and pre-aged (3.7 Mg C) emissions that respectively offset 1.9 ± 1.2% and 0.4 ± 0.3% of CO2 uptake by tundra (-897 ± 115 Mg C). Our findings reveal that inland water carbon emissions from permafrost landscapes may be more sensitive to changes in contemporary carbon turnover than the release of pre-aged carbon from thawing permafrost. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17416

2020063112 Dolman, Han (Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands); van Huissteden, Jacobus; Dean, Joshua; Maximov, Trofim; Petrov, Roman and Marchesini, Luca Belelli. The carbon budget of a tundra in the north-eastern Russian Arctic during the snow free season and its stability in the 2003-2016 period [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19337, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Large quantities of carbon are stored in the terrestrial permafrost of the Arctic region where the rate of climate warming is two to three times more than the global mean and the largest temperature anomalies observed in autumn and winter. The quantification of the impact of climate warming on the degradation of permafrost and the associated potential release to the atmosphere of carbon stocked in the soil in the form of greenhouse gases, thus further increasing the radiative forcing of the atmosphere, is a research priority in the field of biogeosciences. Land-atmosphere turbulent fluxes of CO2 and CH4 have been monitored at the tundra site of Kytalyk in north-eastern Siberia (70,82 N; 147.48 E) by means of eddy covariance since 2003 and 2008, respectively; regular measurement campaigns have been carried out since then. Here we present results of the seasonal CO2 budget of the tundra ecosystem for the 2003-2016 period based on observations encompassing the permafrost thawing season and analyze the inter-annual differences in the seasonal patterns of CO2 fluxes considering the separate the contribution of climatic drivers and ecosystem functional parameters relative to the processes of respiration and photosynthesis. The variability of the CO2 budget is also discussed in view of the impact of the timing and length of the snow free period. The Kytalyk tundra acted as an atmospheric carbon dioxide sink with relatively small inter-annual variability (-96.1±11.9 gC m-2) during the snow free season and the seasonal CO2 budget did not show any trend over time. The pronounced meteorological variability characterizing Arctic summers was a key factor in shaping the length of the carbon uptake period, which did not progressively increased despite its tendency to start earlier, and in determining the magnitude of CO2 fluxes. No clear evidence of inter-annual changes in the eco-physiological response parameters of CO2 fluxes to climatic drivers (global radiation and air temperature) was found along the course of the analysed period. Methane fluxes had a minor contribution to the carbon budget of the snow-free season representing on average an emission of 3.2 gC m-2 (2008-2016) with apparently small inter-annual variability. Similarly, the size of the carbon exported laterally from the ecosystem in the form of dissolved organic carbon flux amounted to 3.1 gC m-2 as determined experimentally. After including these last terms in the budget, the magnitude of the carbon sink associated with the net ecosystem productivity is reduced by 6%, while the GHG budget still denotes a sink of -60.4±11.9 gC-CO2eq (methane GWP over 100-year time horizon). The monitored tundra was to date exerting a steady climate warming mitigation effect as far as the snow free season is concerned, however the figure of its carbon sink could be potentially sensibly lower due to overlooked emissions in the autumn freeze-up and early winter periods. Also, nonlinear accelerations in the permafrost degradation could happen once tipping points in the Arctic climate are exceeded. Both aspects underline the relevance of long term and continuous biogeochemical monitoring in permafrost tundra environments. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19337

2020063026 Domine, Florent (Université Laval, Quebec, QC, Canada); Lackner, Georg; Belke-Brea, Maria; Sarrrazin, Denis and Nadeau, Daniel. Does shrubs growth in the High-Arctic lead to permafrost warming? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10837, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With climate warming shrubs can grow on high-Arctic tundra. This impacts many terms of the energy budget, resulting in a modification of the permafrost thermal regime. The summer surface albedo is decreased. The winter surface albedo is decreased because shrubs protrude above the snow. Winter conductive fluxes through the snow are reduced because shrubs trap snow, increasing snow depth. Shrubs also favor both snow melt in fall and spring and depth hoar formation in fall and winter, and both these factors affect snow thermal conductivity. Soil thermal properties may also be affected because of increased moisture. We have measured many terms of the energy budget at Bylot Island, 73°N, Canada, at a herb tundra site and in a nearby large willow shrub patch. Monitored variables include radiation, snow and soil thermal conductivity and standard atmospheric variables. We observe that soil temperature at 15 cm depth is 1.5°C warmer under shrubs on a yearly average. The energetics of both sites are simulated using SurfexV8 including the detailed snow model Crocus. Combining observations and simulations indicates that the increased soil moisture under shrubs, by delaying freezing by one month in fall, is an important factor in winter soil warming. Summer temperature is also markedly warmer under shrubs because of lower albedo and because the shrub understory is less insulating than on herb, which facilitates warming. These results show that investigating shrub impact using manipulations such as shrub removal is questionable because it does not restore pre-shrub understory and moisture. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10837

2020062995 Dudek, Justyna (University of Wroclaw, Institute of Geography and Regional Development, Wroclaw, Poland) and Strzelecki, Mateusz Czeslaw. Post-Little Ice Age retreat of glaciers triggered rapid paraglacial landscape transformation in Sorkapp Land (Spitsbergen) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8967, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Contemporary climate warming in the Arctic affects the dynamics of the entire environment, including components of the cryosphere: permafrost and glacier systems. The change in the structure of the polar landscape since the termination of the Little Ice Age (ca. 1900) was expressed by widespread retreat of glaciers, progressive exposure of glacial landforms at ice margins and opening ice marginal zones to increasing paraglacial and periglacial processes operating synchronously in adjacent areas. The main aim of the presented study was to determine the course and spatial diversity of landscape transformation in the Sorkapp Land peninsula (Spitsbergen) as a result of glacier recession in the periods 1961-1990-2010 based on existing remote sensing data. Using photogrammetric methods of data processing combined with GIS techniques, the rates of proglacial and ice-marginal terrain change following deglaciation have been determined. For the mentioned research period, the area of the marginal zones almost doubled from 53 km2 to 99 km2. The dynamics of landscape transformation in these zones manifested in rapid reduction in the surface elevation of ice-cored moraines (with mean decrease of 0,18-0,22 m per year) and the forms underlain by the dead-ice. This process was enhanced by mass movements and debris flows. Within marginal zones, the area of subglacial landforms and sediments increased by 31 km2 from 8 km2 in 1961 to 39 km2 in 2010. Larger volume of proglacial waters and associated intensification of denudation, transport and accumulation of sediments entailed area increase of sandurs and proglacial riverbeds (which almost tripled from 3,5 km2 to over 10 km2). Further redeposition and remobilization of material in some places also promoted enhanced sediment aggradation in coastal environment forming new beaches and spit systems. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8967

2020063136 Efimov, Vasilii (Lomonosov Moscow State University, Department of Land Hydrology, Moscow, Russian Federation); Chalov, Sergey; Magritsky, Dmitry; Tsyplenkov, Anatolii; Efimova, Liudmila and Kasimov, Nikolay. Trace metal and nutrient fluxes into Arctic ocean by largest Siberian rivers (ArcticFlux) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21193, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Trace metal and nutrient fluxes into Arctic ocean by largest Siberian rivers (ArcticFlux) Precise estimates of river runoff are one the most challenging fields of river hydrology. Quantitative assessment of the fluxes of suspended and, especially, bed load, as well as their correlation with the flow dissolved loads remains weekly studied with a crucial need of in-situ observations, especially in large rivers. The project is focused on semi-empirical and modeling study of flows, concentrations, modes and loads of trace metals and nutrients fluxes of the major rivers of Arctic. Monitoring stations were organized at the outlets of largest Siberian rivers: Ob, Yenisei, Lena, Kolyma, which transport more than 60% of the water flow from the Russian Arctic. Observations were made for high and low water regime periods on the regular basis, and the total number of samples today exceeds 210. For each sample analyses were made for trace metals (68 elements), nutrients and dissolved and suspended organic carbon matter content both in dissolved and particulate (suspended and bed loads) forms. These samples can determine annual and seasonal distribution to 70% of the chemical elements and substances, carried by large rivers of the Russian Arctic into the Arctic Ocean. For more accurate flux assessment, a new sampling technique was used. It allows to determine all components of the dissolved, suspended and, especially, bed load along the river section and includes sampling at 3-5 verticals on different depth. As a result, it is possible to determine the variability of the fluxes along the width of the section. As an example, concentrations of suspended sediments on the left and right banks of the Kolyma River differ in 6-7 times (up to 70 mg/dm3) and there are significant differences in Ni, Fe, Al, Cu, and Pb fluxes. Heterogeneity in the distribution of sediment and chemical flow across the width of the rivers arise due to the inflow of tributaries and as a result of permafrost melting and wave erosion of the banks. The study of the intensity of bank erosion and sedimentation at the outlets of Arctic rivers both in the field and according to remote sensing data is a significant part of the project. Based on the modeling techniques and application of erosion models for all four Arctic catchments it will also focus on the novel quantitative assessment of bank and catchment erosion contribution into chemical and sediment loads. The project concept is considered as a part of Marine component of Pan-Eurasian program (PEEX) and builds a bridge to integrate PEEX marine components with the existing terrestrial/atmospheric PEEX The reported study was funded by RFBR according to the research project 18-05-60219 [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21193

2020063048 Eicken, Hajo (University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, AK); Danielsen, Finn; Druckenmiller, Matthew; Fidel, Maryann; Hauser, Donna; Iversen, Lisbeth; Johnson, Noor; Jones, Joshua; Kaufman, Mette; Lee, Olivia; Pulsifer, Peter and Sam, Josephine-Mary. Community-based observations help interface indigenous and local knowledge, scientific research, and education in response to rapid Arctic coastal change [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12248, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic coastal sea-ice environments are undergoing some of the most rapid changes anywhere in the Arctic, with implications for coastal communities' food security and infrastructure, marine ecosystems, and permafrost. We argue that responses to such rapid change are most effective when informed by Indigenous and local knowledge and local observations to provide understanding of relevant processes, their impacts, and potential adaptation options. Community-based observations in particular can help create an interface across which different forms of knowledge, scientific research, and formal and informal education can co-develop meaningful responses. Through a broader literature review and a series of workshops, we have identified principles that can aid in this process, which include matching observing program and community priorities, creating sufficient organizational support structures, and ensuring sustained community members' commitment. Drawing on a set of interconnected examples from Arctic Alaska focused on changing sea-ice environments and their impacts on coastal communities, we illustrate how these approaches can be implemented to provide knowledge sharing resources and tools. Specifically, in the context of the Alaska Arctic Observatory and Knowledge Hub (A-OK), a group of Inupiat ice and coastal marine ecosystem experts is working with sea-ice geophysicists, marine biologists, and others to track changes in coastal environments as well as the services that the ice cover provides to coastal communities. The co-development of an observing framework and a web-based searchable database of observations has provided an interface for exchange and an education resource. An annual survey of hunting trails across the shorefast ice cover in the community of Utqiagvik serves to further illustrate how different, response-focused activities such as the tracking of ice hazards - increasingly a concern with loss of ice stability and shortening of the ice season - can be embedded within a community-based monitoring framework. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12248

2020063050 El-Amine, Mariam (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Roy, Alexandre; Legendre, Pierre and Sonnentag, Oliver. The relative importance of environmental factors on the interannual variability of carbon fluxes in the boreal forest [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12470, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

As climate change will cause a more pronounced rise of air temperature in northern high latitudes than in other parts of the world, it is expected that the strength of the boreal forest carbon sink will be altered. To better understand and quantify these changes, we studied the influence of different environmental controls (e.g., air and soil temperatures, soil water content, photosynthetically active radiation, normalized difference vegetation index) on the timing of the start and end of the boreal forest growing season and the net carbon uptake period in Canada. The influence of these factors on the growing season carbon exchanges between the atmosphere and the boreal forest were also evaluated. There is a need to improve the understanding of the role of the length of the growing season and the net carbon uptake period on the strength of the boreal forest carbon sink, as an extension of these periods might not necessarily result in a stronger carbon sink if other environmental factors are not optimal for carbon sequestration or enhance respiration. Here, we used 31 site-years of observation over three Canadian boreal forest stands: Eastern, Northern and Southern Old Black Spruce in Québec, Manitoba and Saskatchewan, respectively. Redundancy analyses were used to highlight the environmental controls that correlate the most with the annual net ecosystem productivity and the start and end of the growing season and the net carbon uptake period. Preliminary results show that the timing at which the air temperature becomes positive correlates the most strongly with the start of the net carbon uptake period (r = 0.70, p < 0.001) and the start of the growing season (r = 0.55, p < 0.01). Although the increase of the normalized difference vegetation index also correlates with the start of these periods, a thorough examination of this result shows that the latter happens well before the former. No dependency between any environmental control and the end of the net carbon uptake period was identified. Also, the annual net ecosystem productivity is highly correlated with the length of the net carbon uptake period (r = 0.54, p < 0.01). Other environmental controls such as annual precipitations, the mean annual soil temperature or the maximum yearly normalized difference vegetation index have a smaller impact on the annual net ecosystem productivity. By extending the dataset to include forest stands that represent a wider climate and permafrost variability, we will examine the generalizability of these results. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12470

2020063081 Ewald, Andreas (University of Salzburg, Department of Geography and Geology, Salzburg, Austria) and Otto, Jan-Christoph. Paraglacial cirque headwall instability; regional scale assessment of preconditioning factors [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17195, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Cirques are characteristic landforms in high alpine environments with flat cirque floors flanked by steep headwalls. From a rock-mechanical perspective, rock walls are assumed to adjust over time according to their internal rock mass strength, which is determined by a number of factors including e. g. intact rock strength and fracture system characteristics. However, temperatures permanently below freezing as well as glacier coverage keep cirque headwalls stabilised so that slope inclination can evolve during glaciation that is far beyond strength equilibrium. When cirque headwalls deglaciate, the relative importance of rock mass properties increases drastically as they precondition rock slope instability. Cataclinal headwalls, where major fracture sets dip out of the slope, are rated as unstable and usually respond rapidly to glacier retreat. Anaclinal headwalls with in-dipping fracture sets in contrast respond delayed and probably less drastically. To date, a systematic assessment of the predisposition of cirque headwalls for rock slope instability following deglaciation is lacking. We aim to tackle this lacking by a systematic regional analysis of predisposition factors using GIS tools. For the central Hohe Tauern Range, Austria, regional datasets are available for the most important preconditioning factors including topography (digital elevation model), geology (digital geological map), glacier extent (digital glacier inventory), and permafrost distribution (PERMAKART 3.0). We combined geomorphometric analyses with geotechnical data to locate and evaluate the sensitivity of glacier headwalls to rock slope instability using GIS and object-based analysis techniques. Our results show that a vast majority of the headwalls identified can be divided by a significant convexity in the slope profile curvature into a larger, upper and a lower, steeper headwall section (> 60°). The lower limit of the steeper section is marked by a significant concavity in the slope profile curvature, which is commonly known as the schrundline. Assuming that the convex transition between steeper and flatter headwall section constitutes the upper limit of enhanced headwall retreat e.g. by periglacial weathering inside the bergschrund, we further address this headwall section as the schrundwall. Geotechnical data (foliation dip and direction) has been digitalised and interpolated in a yet oversimplified manner, to distinguish headwalls into cataclinal, anaclinal and orthoclinal slopes. Slope inclination and foliation dip has been interrelated to identify e.g. particularly sensitive overdip slopes. First results show that anaclinal and orthoclinal as well as cataclinal headwalls are quite common features in the study area. However, overdip slopes with steeply (30°-60°) outdipping foliation are almost exclusively found in schrundwall sections. The persistence of steep overdip schrundwalls may be related to permafrost occurrence, which is subject to further analysis. Our approach, applied to modeled subglacial topography, may be of great value to anticipate future paraglacial instabilities in glacier headwalls. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17195

2020063014 Ezhova, Ekaterina (University of Helsinki, INAR/Physics, Helsinki, Finland); Kukkonen, Ilmo; Suhonen, Elli; Ponomareva, Olga; Gravis, Andrey; Gennadinik, Viktor; Miles, Victoria; Drozdov, Dmitry; Lappalainen, Hanna; Melnikov, Vladimir and Kulmala, Markku. Modelling of long-term permafrost evolution in the discontinuous permafrost zone of north-west Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10325, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The rate of climate warming in North-West Siberia is among the highest in the world and this trend is especially pronounced in summer [1]. Analysis of permafrost thermal conditions in this area provides plausible scenarios of permafrost degradation also elsewhere. An increase in the summer mean temperature together with the prolongation of the warm season results in the increase of the thawing degree-days enhancing thawing of permafrost. Here we present the results of decadal temperature observations from three boreholes near Nadym, North-West Siberia. We further use the results and the observed cryolithological structure of soils in two boreholes to model the long-term evolution of the deep permafrost under two climate scenarios, RCP2.6 (climate action, fast reduction of CO2 emissions) and RCP8.5 ("business as usual"). Both borehole sites have a topmost high-porosity, high-ice content layer of peat which helps prolonging the degradation. The main difference between the boreholes is snow cover resulting from the difference of borehole positions (one is located on the top of the hill). Our results suggest that under RCP8.5 scenario permafrost will degrade in both boreholes. On the contrary, under RCP2.6 scenario permafrost will degrade in one borehole with the deeper snow cover, where it already shows the signs of degradation. For the other borehole, the model predicts that permafrost will not degrade within the next 300 years, although the permafrost temperatures are eventually above -1°C. [1] Frey K.E. & Smith L.C. Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation. Polar Research 22(2), 287-300 (2003). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10325

2020063017 Ezhova, Ekaterina (University of Helsinki, INAR/Physics, Helsinki, Finland); Orlov, Dmitry; Suhonen, Elli; Kaverin, Dmitry; Mahura, Alexander; Gennadinik, Victor; Kukkonen, Ilmo; Drozdov, Dmitry; Lappalainen, Hanna; Melnikov, Vladimir; Petaja, Tuukka; Kerminen, Veli-Matti; Zilitinkevich, Sergey; Malkhazova, Svetlana; Christensen, Torben and Kulmala, Markku. The link between precipitation and recent outbreak of anthrax in north-west Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10449, 2 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Anthrax is a bacterial disease affecting mainly livestock but also posing a risk for humans. During the outbreak of anthrax on Yamal peninsula in 2016, 36 humans were infected and more than 2.5 thousand reindeer died or were killed to prevent further contamination [1]. Anthrax is a natural focal disease, which means that its agents depend on climatic conditions. The revival of bacteria in previously epidemiologically stable region was attributed to thawing permafrost, intensified during the heat wave of 2016. We studied recent dynamics of air temperature as well as summer and winter precipitation in the region. In addition, we analysed the effect of winter precipitation and air temperature on the dynamics of active layer thickness using data from Circumpolar Active Layer Monitoring sites [2]. Our analysis suggests that permafrost was thawing intensively during several years before the outbreak, when snowy cold winters followed warmer winters. Thick snow prevented soil from freezing and enhanced permafrost thawing. In addition, we showed that summer precipitation drastically decreased in the region of outbreak during recent years, likely contributing to the spread of disease. [1] Popova, A.Yu. et al. Outbreak of Anthrax in the Yamalo-Nenets Autonomous District in 2016, Epidemiological Peculiarities. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. 4, 42-46 (2016). [2] Circumpolar Active Layer Monitoring site: URL: https://www2.gwu.edu/~calm/ [2/08/2019]. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10449

2020063088 Fazel, Nasim (University of Oulu, Water, Energy and Environmental Engineering Research Unit, Oulu, Finland); Haghighi, Ali Torabi; Rasouli, Kabir and Klove, Bjorn. Flow regime variation in Arctic rivers [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17701, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic rivers' flow regime has changed under climate change and its consequences on melting glaciers, thawing permafrost, and precipitation patterns. Reservoirs, hydro-power sites, and water diversions have also changed flow regimes in the Arctic. The flow regime alteration in the Arctic rivers has a strong influence on the conservation and sustainability of the native biodiversity of the riverine ecosystem. The main objective of this paper is to evaluate changes in the (1) magnitude of monthly stream flows, (2) magnitude and duration of annual maxima and minima flows, (3) timing of annual maxima and minima, (4) frequency and duration of high and low pulses, and (5) rate and frequency of daily flows in seven major Arctic Rivers. The analyses provide an important basis to characterize and understand the influence of climate change and anthropogenic activities on the flow regimes in the Arctic. Streamflow observations were obtained from the outlet of the Lena, Yenisei, Kolyma, Ob (Russia), Yukon (USA and Canada), Mackenzie (Canada), and Tana (Norway and Finland) rivers in this study. These rivers are main freshwater suppliers for Arctic Ocean. Of these, five have been regulated and two are considered pristine rivers. In addition, the impact of 16 reservoirs on flow regime in the headwaters and tributaries of Lena, Yenisei, Mackenzie, and Kolyma were evaluated. The annual flow showed an increasing trend in all rivers and with a statistically significant level in Yenisei, Lena, and Mackenzie. Our results also indicated that changes in the observed flow regimes at the outlet stations vary from low to incipient level. Out of 16 reservoirs that were analyzed for flow regimes changes, construction of Krasnoyarsk and Shushenskaya dams on the Yenisei River showed the highest impact on flow regime and flow regime alteration was classified as severe in this river. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17701

2020063018 Fey, Christine (University of Natural Resources and Life Sciences Vienna, Institute of Applied Geology, Vienna, Austria); Kuschel, Erik; Amabile, Anna Sara; Straka, Wolfgang and Zangerl, Christian. Monitoring of rock glacier flow velocity variations using imagery, laser scan data and ground-based interferometric synthetic aperture radar (GBInSAR) at the Finstertal Reservoir (Austria) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10451, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rock glaciers are geomorphological phenomena of mountain permafrost which slowly move downslope as a consequence of the ice deformation. During the last few decades, many rock glaciers in the Alps are showing an increase of flow velocities which is most probably caused by climate change. However, the factors influencing the flow velocities (e.g. air temperature, meltwater infiltration, internal rock glacier characteristics) are not fully understood. Data about the annual, inter-annual and diurnal rock glacier flow velocities are essential to understand the influence of climatic factors on rock glaciers. This study focused on the Finstertal rock glacier, located in the Eastern Alps, where flow velocities are reconstructed since the 1970s based on aerial imagery, airborne and terrestrial laser scan data. Since 2014, a terrestrial laser scanning (TLS) based monitoring is implemented. The maximum flow velocities of the Finstertal rock glacier increased from 0.1 m/year (time period 1970-1997) to 1.4 m/year (time period 2015-2016) and is currently about 1.3 m/ year (time period 2018-2019). The accuracy of aerial imagery and laser scan data is in the range of centimetres and well suited to analyse the annual variability of rock glaciers. Imagery and laser scan data are not suited for shorter time intervals, where the absolute displacement of a rock glacier is smaller than the measurement accuracy. Consequently, for the understanding of interannual and diurnal variations in rock glacier flow velocities, other measurement methods are needed. Ground-based interferometric synthetic aperture radar (GBInSAR) is able to detect spatial deformations in the range of sub-centimeters. Therefore, to get a more detailed understanding of the rock glacier flow velocity variations, a GBInSAR was installed on Finstertal hydroelectric dam to measure the rock glacier flow velocities between October to November 2019. In this study, preliminary results on diurnal flow velocity variations of Finstertal rock glacier, based on GBInSAR, are presented, and compared to annual variations derived from aerial imagery and laser scan data. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10451

2020063009 Fouche, Julien (SupAgro Montpellier, Laboratoire d'étude des Interactions Sol-Agrosystème-Hydrosystème, Montpellier, France); Hirst, Catherine; Opfergelt, Sophie; Vonk, Jorien; Bonneville, Steeve; Haghipour, Negar; Eglinton, Timothy and Bröder, Lisa. Characterization of dissolved and particulate organic matter exported during late summer from a glacio-nival river, Zackenberg, Greenland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9776, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With Arctic warming, both gradual and abrupt thaw of permafrost may trigger a positive feedback loop, since large amounts of organic matter (OM) are released into rivers and thus exposed to mineralization along the fluvial continuum. Both dissolved (DOM) and particulate organic matter (POM) mineralization during lateral transport generates greenhouse gases that may fuel further global warming. In addition to glacier retreat, the extent of permafrost thaw is predicted to increase across the Arctic, which will change the release of DOM and POM to aquatic environments. However, the fate of DOM and POM will likely differ during transport in surface waters due to POM-DOM exchange and biodegradation control from organo-mineral interactions. The contrasting behavior between POM and DOM may affect the strength of the permafrost-carbon feedback to climate but is currently afflicted with high uncertainties. This study characterizes the export of DOM and POM along the fluvial continuum at time of maximum thaw depth and investigates the impacts of permafrost thaw on OM composition and age in the Zackenberg watershed (Northeastern Greenland). In August 2019, streams were sampled twice, before and after a rain event. We collected water and suspended sediments from rivers, the river delta, snow patches and permafrost ice from thermokarst features. Besides in situ river chemistry, we analyzed stable water isotopes (d18O, d2H) and dissolved organic carbon (DOC) concentrations. The composition of DOM was characterized using absorbance and fluorescence spectroscopy and both DOM and POM were analyzed for radiocarbon (D14C). DOC concentrations increase from 3.1 mg L-1 upstream to 15.6 mg L-1 after the confluence with the main tributaries, which are characterized by a nival river regime, and decreased to 4.3 mg L-1 at the outlet. Optical properties of DOM highlight that low molecular weight microbial-derived organic compounds contribute most to the fluorescent DOM (fDOM) in the upstream part of the river, likely originating from glacial waters. The contribution of soil and plant derived fDOM increases downstream, and corresponding D14CDOC values increase from upstream (-240 ppm, i.e. ~2200 yr) to downstream (-30 ppm, i.e. ~200 yr) resulting from the increasing tributary inputs. Interestingly, POM displays more depleted D14C (older ages) than DOC. We observed contrasting patterns in river chemistry before and after the rain event with temperature decreasing and pH and EC increasing. d18O and d2H compositions were less depleted after the rain event, DOC concentrations were lower and DOM displayed a greater contribution of soil and plant derived fDOM. This evidence illustrates the increasing contribution of rain fed streams draining organic-rich top soil and the dilution of the glacial inputs after the rain event. We conclude that, in this glacio-nival Arctic watershed, affected by both permafrost degradation and glacier retreat, old DOM and POM is released and evolves differently in the fluvial continuum. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9776

2020063045 Frappier, Roxanne (University of Ottawa, Department of Geography, Environment and Geomatics, Ottawa, ON, Canada) and Lacelle, Denis. Ice-wedge polygons distribution, morphometry and state in the Tombstone Territorial Park, central Yukon, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12044, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Ice wedge (IW) polygons form through thermal contraction induced by winter cooling of ice-rich permafrost which results in the formation of cracks. Hoar frost develops in the cracks in winter and meltwater infills the cracks during spring and freezes. As the cracking and infilling occurs repeatedly, IWs grow, leading to characteristic surface morphology with depressions or troughs aligned on the axis of the IW and raised rims or ridges on either side. Surface expression of IW is either characterized as low-centered polygons or high-centered polygons, the former being associated with the first stages of IW development, and the latter with IW degradation. Because IWs represent important excess ice close to the surface, considerable local subsidence and related effects on landscape parameters, such as vegetation and moisture, are likely to occur upon degradation. IW polygons distribution, morphometry and state were characterized in the Tombstone Territorial Park (Central Yukon, Canada) using semi-automated remote sensing techniques, field observations and laboratory analyses. The data is used to define determining landscape factors for IW polygons occurrence, to characterise the stages of the IWs development and/or degradation and to estimate the volume of buried ice in the region. Results show that elevation, slope and material are important elements defining IW polygons distribution. The relationship between landscape factors and stages of development is not as clear, and, despite climate changes being homogenous in the area, IW development and degradation is very heterogenous, as shown by the differing moisture, greenness and brightness signals across the polygonal terrain. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12044

2020063099 Frimberger, Theresa (Technichal University of Munich, Chair of Landslide Research, Munich, Germany); Petry, Franziska and Krautblatter, Michael. Assessing lahar hazards at Cotopaxi Volcano (Ecuador) controlled by volcanic eruptions and glacier retreat [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18219, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Lahars rank as one of the most destructive hazards at Cotopaxi volcano (5897 m asl) due to the presence of a massive glacier cap, the frequency of eruptions and the high population density in the surrounding, potentially inundated valleys. In 1877, Cotopaxi experienced the last major VEI 3-4 eruption, producing syneruptive lahars of 60-100 million m3 that travelled hundreds of km downstream. Few lahar simulations based on empirical or fluid dynamic approaches exist for Cotopaxi, but here we introduce a calibrated numerical debris flow model capable of reproducing confluence and erosivity of flows. In this study, we back-calculate the well documented 1877 lahar event using the 2D debris flow model RAMMS, which is based on the Voellmy-Salm friction approach and includes an entrainment algorithm. We first evaluate the sensitivity and range of possible model input parameters by systematically varying model inputs for release volume, density and frictional resistance (Coulomb type friction m [-] and turbulent friction m [ms-2]). Supported by a probabilistic analysis, we find that a choice of historical and field-derived calibration metrics of the 1877 lahar event along the northern lahar trajectory can well constrain most likely input parameters for frictional resistance. Our results show that modelling large-scale primary lahars at Cotopaxi is strongly controlled by very small values for Coulomb friction m (0.005-0.015). Finally, we apply the calibrated model to typical eruption scenarios of Cotopaxi (VEI 1 to >4) in order to enable a realistic lahar hazard representation. Considering the rapid rise of the equilibrium-line altitude of tropical Andean glaciers together with reports on secondary lahars at the eastern flank of Cotopaxi without any clear trigger, we hypothesize a process-based link between the two phenomena. Geoelectrical and refraction seismic field surveys near the glacier margin (5000- 5300 m asl) have been conducted in order to gain a better understanding of the structure, conditions and degree of freezing of the subsurface, which is dominated by loose pyroclastic material and interbedded lava layers. The tomography results are highlighted within the concept of permafrost degradation and accompanied material weakening as potential triggering mechanism for secondary lahars. Here we show 1) a carefully calibrated numerical lahar model at Cotopaxi capable of reproducing previously non-respected effects such as confluence, erosion reach and propagation speed, and 2) first measurements addressing the role of glacier retreat on the formation of secondary lahars. Our results contribute to the multi-hazard risk assessment in the RIESGOS project funded by the German Ministry of Education and Research. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18219

2020063116 Galloway, Jennifer (Geological Survey of Canada, Calgary, AB, Canada); Galka, Mariusz; Swindles, Graeme; Amesbury, Matt; Wolfe, Stephen; Morse, Peter; Patterson, Tim and Falck, Hendrik. Ecohydrological dynamics of a degrading subarctic peatland; implications for arsenic mobility [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19666, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

A peatland from subarctic Canada (Handle Lake 62°29'26.44"N, 114°23'18.23"W) is a degrading permafrost peatland chosen for detailed study due to a legacy of regional arsenic (As) contamination as a result of almost 8 decades of gold mining. The fate of permafrost peatlands and their element stores is unknown due to complex feedbacks between peat accumulation, hydrology, and vegetation that affect redox state and element mobility. We combine palynology with study of plant macrofossils, testate amoebae, organic matter composition, and bulk geochemistry preserved in a ca. 4180-4972 cal year old peat monolith retrieved from the Handle Lake peatland to reconstruct the ecohydrological dynamics to assess future trajectories of permafrost peat, and contaminant storage or release, in response to current and future warming. Sphagnum riparium macrofossils are rare in modern peat habitats and sub-fossils are rare in paleoecological records. Plant macrofossils of this taxon occur in an 11-cm thick layer together with Sphagnum angustifolium between 43 cm (ca. 3390-3239 cal BP) and 25 cm depth (ca. 2755-2378 cal BP) in the monolith. The S. riparium sub-fossils are present with the hydrophilous testate amoebae species Archerella flavum, Hyalosphenia papilio and Difflugia globulosa that are used to quantitatively reconstruct a water table depth of 0-4 cm below the peat surface. Sub-fossils of S. riparium disappear at ca. 2755-2378 cal BP, likely due to an autogenic trophic shift and succession towards more acidophilic conditions favourable to species such as Sphagnum fuscum and Sphagnum russowii. We interpret the occurrence of S. riparium as an indicator of wet and minerotrophic conditions linked to peatland development form rich fen to oligotrophic bog. Because S. riparium is a key pioneer species of disturbed peatlands that have experienced permafrost degradation it will likely be favoured in northern regions experiencing rapid climate warming. In the palynological record the proportion of Sphagnum-type A spores increases (up to 80%) between ca. 3390-3239 cal BP and ca. 2755-2378 cal BP concurrent with a decline in other Sphagnum-type spores. A peak in micro- and macroscopic charcoal occurs between ca. 3557-3286 cal BP and ca. 3275-2771 cal BP, concurrent with a decline in Picea pollen and an increase in Alnus pollen. Regionally, between ca. 3500 and ca. 2500 cal BP Neoglacial climate prevailed with post-Neoglacial warming at ca. 2500 cal BP. It is therefore possible that regional fire occurrence stimulated permafrost degradation at ca. 3500 cal BP. Background As in the active layer monotlith is ~20-30 ppm. The upper 10 cm of the peat are impacted by aerial deposition of As from ore processing and concentrations range up to ~360 ppm. An increase in the concentration of As in the monolith from ~15-20 ppm at the base of the monolith to ~30-40 ppm during this interval may reflect water table depth dynamics that affected the mobility and fate of this redox sensitive element and/or downward mobility from layers impacted by contamination from mineral processing. Degradation of this permafrost within the Handle Lake peatland will release the currently stored As and other contaminants to the regional environment. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19666

2020063077 Georgievski, Goran (Helmholtz-Zentrum Geesthacht, Institute of Coastal Research, Geesthacht, Germany); Hagemann, Stefan; Sein, Dmitry; Drozdov, Dmitry; Gravis, Andrew; Romanovsky, Vladimir; Nicolsky, Dmitry; Onaca, Alexandru; Ardelean, Florina; Chetan, Marinela and Dornik, Andrei. Climate extremes relevant for permafrost degradation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-16115, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

During the past several decades, Arctic regions warmed almost twice as much as the global average temperature. Simultaneously in the high northern latitudes, observations indicate a decline in permafrost extend and landscape modifications due to permafrost degradation. Climate projections suggest an accelerated soil warming, and consequently deepening of the active layer thickness in the near future. Except air temperature, two other parameters i.e. precipitation and snow depth are the most important climatic parameters affecting the thermal state and extend of the permafrost. The key research question of this study is whether or not certain climatic conditions can be identified that can be considered as an extreme event relevant for permafrost degradation. Here we apply data mining techniques on meteorological re-analysis to develop a coherent framework for the identification of extreme climate conditions relevant for active soil layer deepening and a decline of permafrost extend. Several key types of events have been classified based on various combinations of temperature, precipitation and snow depth statistics. Then, the respective events have been identified in ERA-Interim reanalysis and evaluated against in situ observations in West Siberia region. The evaluation proved that the developed algorithm could successfully detect relevant extreme climate conditions in meteorological re-analysis dataset. It also indicated possibilities to improve the algorithm by refining definitions of extreme events. Refinement of algorithm is currently work in progress as well as the evaluation against satellite observations and a hierarchy of numerical models. Nevertheless, the method is applicable for all kinds of gridded climatological datasets that contain air temperature, precipitation and snow depth. Acknowledgement: This work is funded in the frame of ERA-Net plus Russia. TSU is supported by MOSC RF # 14.587.21.0048 (RFMEFI58718X0048), AWI and HZG are supported by BMBF (Grant no. 01DJ18016A and 01DJ18016B), and WUT by a grant of the Romanian National Authority for Scientific Research and Innovation, CCDI-UEFISCDI, project number ERANET-RUS-PLUS-SODEEP, within PNCD III [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-16115

2020063129 Giardino, Marco (University of Torino, NatRisk, Earth Sciences, Turin, Italy); Montani, Antonio; Tamburini, Andrea; Calvetti, Francesco; Borghi, Alessandro; Alberto, Walter; Villa, Fabio; Martelli, Davide; Salvalai, Graziano and Perotti, Luigi. Climate change and cryosphere in high mountains; preliminary results of field monitoring at Capanna Margherita Hut, Punta Gnifetti (Monte Rosa, Pennine Alps) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20375, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In the last decades, climate change effects are spreading on cryosphere of mid latitude high mountains, affecting all environmental and territorial components. The Italian Alpine Club (CAI) is a privileged institution for observing climate change effects on cryosphere in high mountains, as well as for supporting scientists to proper assessment studies of related natural hazards, exposure, vulnerability effects, particularly those around alpine refuges and access routes. CAI has started a cooperative research with University of Torino (UniTO), Politecnico of Milano (PoliMI) and IMAGEO srl, focused in deglaciation, permafrost degradation and slope instabilities at the Punta Gnifetti peak ("Signal Kuppe, 4554 m a.s.l.), Monte Rosa (Pennine Alps, border between Italy and Switzerland). Here is the Margherita Hut, the highest refuge in Europe and a physical-meteorological observatory, as well as home to medical and scientific UniTO laboratories. Activities started on May 2019 with a retrospective collection and interpretation of photos and archival news on the Punta Gnifetti environment. Multi-temporal geomorphological settings are compared to meteorological historical series for creating a morphoclimatic "timeline". Instrumental monitoring and in situ field work began on August 2019, including: 1) determination of the ice thickness of the glacial cover by using georadar; 2) characterization of the geomechanical structure of the rock mass by means of terrestrial laser scanner; 3) establishment of a topographical reference point and georeferencing of all measuring points; 4) collection of litho-structural and geomorphological data for a reference geological model of the Punta Gnifetti; 5) photogrammetric helicopter flight for the 3D reconstruction of the site; 6) direct measurements of internal areas in order to obtain as-built building plans; 7) assessment of building services. Preliminary results are presented here, together with directions for an effective data collection to be continued on 2020, including comparative analyses designated to: a) identify the relevant geomechanical features for rock mass stability; b) verify presence of ice inside fractures; c) reconstruct the ice-covered morphology of the Punta Gnifetti peak. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20375

2020063056 Glade, Rachel (Los Alamos National Laboratory, Los Alamos, NM); Fratkin, Mulu; Rowland, Joel and Nutt, Mara. Solifluction patterns arising from competition between gravity and cohesion [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12698, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic soil movement, accumulation and stability exert a first order control on the fate of permafrost carbon in the shallow subsurface and landscape response to climate change. A major component of periglacial soil motion is solifluction, in which soil moves as a result of frost heave and flow-like "gelifluction". Because soliflucting soil is a complex granular-fluid-ice mixture, its rheology and other material properties are largely unknown. However, solifluction commonly produces distinctive spatial patterns of terraces and lobes that have yet to be explained, but may help constrain solifluction processes. Here we take a closer look at these patterns in an effort to better understand material and climatic controls on solifluction. We find that the patterns are analogous to classic instabilities found at the interface between fluids and air-for example, paint dripping down a wall or icing flowing down a cake. Inspired by classic fluid mechanics theory, we hypothesize that solifluction patterns develop due to competition between gravitational and cohesive forces, where grain-scale soil cohesion and vegetation result in a bulk effective surface tension of the soil. We show that, to first order, calculations of lobe wavelengths based on these assumptions accurately predict solifluction wavelengths in the field. We also present high resolution DEM-derived data of solifluction wavelengths and morphology from dozens of highly patterned hillslopes in Norway to explore similarities and differences between solifluction lobes and their simpler fluid counterparts. This work leads us toward quantitative predictions of the presence or absence of solifluction patterns and their response to variation in material properties (e.g., vegetation, rock type, grain size) and climatic conditions (e.g., water content, active layer depth, variability in snow cover). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12698

2020063025 Goeckede, Mathias (Max Planck Institute for Biogeochemistry, Jena, Germany); de Vrese, Philipp; Brovkin, Victor; Koch, Frank-Thomas and Roedenbeck, Christian. Coupling bottom-up process modeling to atmospheric inversions to constrain the Siberian methane budget [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10833, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Methane (CH4) is one of the most important greenhouse gases, but unexpected changes in atmospheric CH4 budgets over the past decades emphasize that many aspects regarding the role of this gas in the global climate system remain unexplained to date. With emissions and concentrations likely to continue increasing in the future, quantitative and qualitative insights into processes governing CH4 sources and sinks need to be improved in order to better predict feedbacks with a changing climate. Particularly the high northern latitudes have been identified as a potential future hotspot for global CH4 emissions, but the effective impact of rapid climate change on the mobilization of the enormous carbon reservoir currently stored in northern soils remains unclear. Process-based modelling frameworks are the most promising tool for predicting CH4 emission trajectories under future climate scenarios. In order to improve the insights into CH4 emissions and their controls, the land-surface component of the Max Planck Earth System model, JSBACH, has been upgraded in recent years. In this context, a particular focus has been placed on refining important processes in permafrost landscapes, including freeze-thaw processes, high-resolution vertical gradients in transport and transformation of carbon in soils, and a dynamic coupling between carbon, water and energy cycles. Evaluating the performance of this model, however, remains a challenge because of the limited observational database for high Northern latitude regions. In the presented study, we couple methane flux fields simulated by JSBACH to an atmospheric inversion scheme to evaluate model performance within the Siberian domain. Optimization of the surface-atmosphere exchange processes against an atmospheric methane mixing-ratio database will allow to identify the large-scale representativeness of JSBACH simulations, including its spatio-temporal variability in the chosen domain. We will test the impact of selected model parameter settings on the agreement between bottom-up and top-down techniques, therefore highlighting how sensitive regional scale methane budgets are to dominant processes and controls within this region. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10833

2020063093 Grebenets, Valery (Moscow State University, Department of Cryolithology and Glaciology, Moscow, Russian Federation); Tolmanov, Vasily; Fedin, Vladimir and Sinitskiy, Anton. Using the results of dangerous cryogenic processes investigations in student education [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17896, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The department traditionally holds specialized practices of cryolithology and glaciology. Recently, specialized field course (sometimes international) have been concentrated in the Arctic region of Russia in the south of Yamal. The studies were focused on the investigation of the permafrost features in the regions, on assessing the permafrost dynamics and processes, affected by the various number of factors. Here, the results of studies dedicated to the assessment of dangerous cryogenic processes impact on the infrastructure of the far north are widely introduced. Unique studies of the level of deformation of the infrastructure of the northern settlements are carried out during the establishment and development of an unfavorable geocryological situation. Monitoring observations are carried out both in natural and in urbanized conditions, allow us to compare the intensity of the processes, evaluate the contribution of technogenesis and climatic changes. Based on the research results, students and researchers receive the necessary data and field results for analyzing the dynamics and changes in geotechnical systems in the context of an increase in the technogenic press and temperature increase in the region. Investigation is supported by the RFBR project 18-05-60080 "Dangerous nival-glacial and cryogenic processes and their influence on infrastructure in the Arctic" [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17896

2020063086 Groeneveld, Marloes (Uppsala University, Department of Ecology and Genetics, Uppsala, Sweden); Jakobsson, Elizabeth; Hawkes, Jeffrey; Tittel, Jörg; Kothawala, Dolly and Tranvik, Lars. When mobilized organic matter and glacial suspended sediment meet; effects of adsorption, photo- and biodegradation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17679, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The thawing of permafrost is leading to increased export of organic matter into aquatic ecosystems that was previously stored within frozen peatland soils. This organic matter has been found to be reactive to microbial and photochemical processes, so that permafrost thaw is expected to lead to an increased production of greenhouse gases. Being able to predict the fate of these increased loads of terrestrial organic carbon in aquatic systems is therefore important from a climate change perspective. In a previous study we suggest that terrestrial organic compounds susceptible to photodegradation are also prone to adsorb to mineral particles. Whereas photodegradation stimulates CO2 production, adsorption has the potential to remove organic matter from the water column and store it in the sediment. Warming at high latitudes involves both permafrost thaw and glacial melt. Glacial runoff streams often contain high loads of suspended sediment. As these minerogenic particles are transported downstream the aquatic continuum, they can eventually mix with water containing high concentrations of freshly released organic matter, and act as an adsorbent. In order to predict CO2 production from mobilized permafrost organic matter, we need to study the bioavailability of this material before and after alteration by physical and chemical processes such as photodegradation and adsorption to mineral particles. In this study, we compared the effect of adsorption to glacial suspended sediment to that of photodegradation on the dissolved organic matter composition of surface water collected from a thawing peat plateau in northern Sweden. We used optical measurements and mass spectrometry to evaluate changes in the composition of the organic matter and employed a three-month incubation to determine its bioavailability. Initial results from optical measurements indicate that while chromophoric compounds in general were removed by both photodegradation and adsorption, humic-like fluorescent compounds were more susceptible to photodegradation than adsorption. UV-irradiation increased bioavailability of the organic matter, whereas pre-treatment by adsorption to mineral particles slightly decreased bioavailability compared to the control. Results from this study will help advance our understanding of interactive effects between physico-chemical processes and microbial degradation at an increasingly relevant interface where melting permafrost meets glacial meltwaters. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17679

2020063035 Grosse, Guido (Alfred Wegener Institute for Polar and Marine Research, Permafrost Research, Potsdam, Germany); Boike, Julia; Farquharson, Louise; Jones, Benjamin M.; Langer, Moritz; Lantuit, Hugues; Liljedahl, Anna; Nitze, Ingmar; Runge, Alexandra; Romanovsky, Vladimir E.; von Deimling, Thomas Schneider; Vincent, Warwick F. and Walker, Donald A. Gradual and abrupt permafrost thaw as drivers of rapid geomorphic change in Arctic permafrost regions [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11772, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In this presentation, we will highlight some of the overarching geomorphic dynamics of gradual and abrupt permafrost thaw using examples from Siberia, Alaska, and Canada, their role in Arctic landscapes transitioning to a warmer world, and implications for the Earth System. Northern high latitude regions are particularly vulnerable to warming and changes in climatic patterns, which leads to the thaw of ice-rich permafrost across vast Arctic and sub-Arctic landscapes. Permafrost thaw and subsequent geomorphological change directly interact with hydrology, biogeochemistry, and biology and thus have been major agents of Arctic ecosystem change since the last deglaciation. The changes are also important contributors to cumulative impacts associated with historic and current development of the Arctic, including in association with infrastructure. Today, in a rapidly warming Arctic, permafrost thaw processes, both gradual and abrupt, are accelerating in a manner comparable to the Holocene Thermal Maximum. At the same time, other environmental forcing factors, such as wildfires, precipitation, and hydrological processes, are also changing, either further reinforcing thaw dynamics or enhancing drainage and stabilizing the ground. Many of the resulting gradual and abrupt thaw processes are non-linear. Their dynamics are still poorly understood and insufficiently quantified in large-scale models due to lacking or limited representation of water-ice phase transitions during freeze-thaw cycles, ground ice distribution and loss, and challenging implementation of sub-grid cell scale interactions between frozen ground and hydrology. Gradual thaw impacts are especially pronounced in regions with an abundance of ice wedge polygons, and include changes in microtopography and extensive ponding in natural landscapes and those adjacent to infrastructure, where soils are warmed due to increased dust, flooding, snowdrifts, and altered vegetation. Abrupt thaw processes such as thermokarst and thermo-erosion represent rapid dynamics that are widespread in Arctic lowlands but poorly represented in observations and models. Characteristic landforms that result from abrupt thaw include thermokarst lakes and basins, retrogressive thaw slumps, and steep coastal bluffs. These landscape changes may be triggered by climate-driven press disturbances such as sea ice loss or increases in precipitation, pulse disturbances such as wildfires, or by anthropogenic disturbances such as road construction. When loss of excess ground ice is involved, positive feedbacks can result in a decoupling of further geomorphological change from climate. Once initiated, this may lead to continued or even accelerated growth of such features under a wide range of climate conditions, including in the high Arctic. Most abrupt thaw processes produce lasting impacts on northern permafrost landscapes that are irreversible over millennial timescales and result in the short-term mobilization of large amounts of permafrost carbon that may further contribute to climate warming. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11772

2020063084 Gustafsson, Orjan (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Semiletov, Igor; Shakhova, Natalia; Dudarev, Oleg; Vonk, Jorien; Van Dongen, Bart; Eglinton, Tim; Tesi, Tommaso; Bröder, Lisa; Andersson, August; Wild, Birgit; Matsubara, Felipe and Martens, Jannik. Transport and fate of different components of terrestrial organic matter across the Siberian-Arctic shelves [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17595, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

About one-third to half of the global soil carbon is held in the top 1-3 m of tundra+taiga permafrost PF (~1000 Pg-C) with deeper layers below as Deep-PF (~400 Pg-C) and in Pleistocene Ice Complex Deposit permafrost (ICD-PF, ~400 Pg-C), lining 4000 km of the East Siberian Arctic coast. In order to overcome the landscape heterogeneity and the stochastic nature of e.g. erosional release processes, we use the East Siberian Arctic Shelf (ESAS) in an inverse approach - as a natural integrator of the TerrOM releases from both the river drainage basins and from the erosion of ICD-containing bluffs. We are exploring how source-dependent transport and translocated degradation affect the released TerrOM. The sources of released TerrOM have been increasingly constrained using great rivers and the ESAS as natural integrators through a combination of biomarkers and d13C/D14C on bulk-C and on compound level. There are significant gradients in sources both E-W and S-N across each shelf sea and between water column DOM, POM and sedimentary OM. The largest source of OC to ESAS sediments is not rivers or marine plankton - it is coastal erosion of old ICD. Our initial limited dataset has now been much expanded, as has the end-member database while the statistical source apportionment method has been refined. They combine to show more efficient cross-shelf transport of river-borne "topsoil-PF" compared to ICD-PF and a clear distinction in sources of TerrOM between western and eastern ESAS regimes separated roughly along 165E, consistent with the local oceanography. There have been good strides also in understanding degradation of TerrOM exported to ESAS. Studies are demonstrating continuous offshoreward degradation of all TerrOM, yet with large differences between compound classes. Physical association of TerrOM with different sediment components, and sorting of the sediments exert first-order control on TerrOM distribution and degradation. An expanded dataset on specific surface area (SSA) and CuO oxidation products reveals spatial patterns across ESAS. The combination of compound-specific radiocarbon analysis of terrestrial biomarkers with SSA-normalized TerrOM signals constrains the ambient degradation rates and fluxes during the 3-4000 year timescale of cross-shelf transport. The degradation of TerrOM also causes severe ocean acidification of the ESAS. Investigations of sources and fate of TerrOM on the ESAS - the World's largest shelf sea- provides a window to constrain permafrost-C remobilization and to study mechanisms of transport and degradability of different components of released terrestrial organic matter. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17595

2020062990 Hajnsek, Irena (German Aerospace Center, Mircowaves and Radar Institute, Wessling, Germany); Fischer, Georg; Parrella, Giuseppe; Bernhard, Philipp and Leinss, Silvan. TanDEM-X for cryosphere applications [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8458, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In this presentation the focus is laid on cryospheric applications served by the single-pass interferometer TanDEM-X. The German Radar mission TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is already successfully in operation since 2010 and is delivering continuously data over the Earth surfaces. The main mission objective was the generation of a global and consistent digital elevation model (DEM) with a spatial resolution of 12m and a relative vertical height accuracy of 2 m. For this at least two global acquisitions where needed and innovative algorithms where developed to process the data into a global high resolution DEM. In addition to the high resolution DEM also a 90-m DEM was generated to facilitate the comparability with the former SRTM DEM. Beyond the generation of DEMs super-test sites have been establish to collect continuously data over a limited area of interest and to demonstrate and develop new algorithms to support application development. In addition TanDEM-X supports the demonstration and application of new SAR techniques, with focus on multi-static SAR, polarimetric SAR interferometry, digital beam forming and super resolution. Today it is known through observations, delivered by satellites and conventional observing systems that the Cryosphere reacts very sensitively to climate change. However, the feedbacks to the global climate system are not well understood, impairing predictions of the impact of future climate change. Improved observational data have been provided to better quantify the main cryospheric processes and improve the representation of the Cryosphere in climate models. TanDEM-X data (product but also interferometric data) have been used from an international science team for a diversity of cryosphere applications. The presentation will provide an overview of the operation status of TanDEM-X and will focus on the applied cryospheric applications so far applied. Examples of the detection of permafrost features, the estimation of the firn-line zone, derivation of vertical ice structure, the mass loses of over ice sheets and sea ice height estimation will be presented. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8458

2020063076 Hansche, Iris (University of Graz, Department of Geography and Regional Science, Graz, Austria); Abermann, Jakob; Shahi, Sonika and Schöner, Wolfgang. Spatial and temporal variations of air temperature inversions over different surface types on Ammassalik Island (East Greenland) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-15597, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Air temperature inversion, a situation in which atmospheric temperature increases with height, is a common feature in the Arctic planetary boundary layer. This stable layer has multiple consequences for the Arctic environment. While vertical gradients of flora and fauna are impacted by them, they also have a direct consequence on physical characteristics such as permafrost thaw depths and snow cover. Therefore, a comprehensive knowledge about the spatial and temporal variability of temperature inversion parameters such as thickness, intensity, magnitude and frequency is crucial for the surface impact of Arctic climate change. Here, we investigate the spatial and temporal variations of temperature inversions over different surface types on Ammassalik Island in East Greenland. During a field campaign in summer 2019, high temporal resolution profiles of atmospheric variables such as air temperature, humidity and pressure were collected using UAVs. We acquired 147 profiles in a period of 13 days (06/07/2019-18/07-2019) over different surface types (rock, gravel, snow, ice) and with varying distance to the ocean (between 0 and 6 km). We found a distinct air temperature inversion present in most of the profiles whereby height and thickness differ considerably. Both ocean and ice surface act as near-surface cooling agents, which favours the development of surface inversions. The ice-free area between ocean and glacier tends to warm up strongly during Arctic summer and those different drivers manifest in an intricate pattern of air temperature stratification along a valley axis. Our high-frequency and high-resolution profiles are compared with longer time series from the nearby Tassiilaq radiosonde and with ERA-5 reanalysis data in order to bring our campaign data into a larger spatio-temporal context. We conclude that the radiosonde is able to resolve the general pattern well but it fails in adequately representing the stratification relevant for glacio-meteorological processes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-15597

2020063043 Hartmeyer, Ingo (GEORESEARCH, Salzburg, Austria); Delleske, Robert; Keuschnig, Markus; Krautblatter, Michael; Lang, Andreas; Schrott, Lothar and Otto, Jan-Christoph. Paraglacial responses in deglaciating cirque walls; implications for rockfall magnitudes/frequencies and rockwall retreat [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11955, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Over the past 150 years almost half of the glacier volume disappeared in the European Alps. Besides glacier retreat, ice surface lowering reflects much of the volume loss and uncovers the adjacent rockwalls. In steep glacial cirques, this process exposes rock to atmospheric conditions for the very first time in many millennia. Instability of rockwalls has long been identified as one of the direct consequences of deglaciation, but so far cirque-wide quantification of rockfall at high-resolution is missing and the proportional contributions of low-, mid- and high magnitude rockfalls have remained poorly constrained. We use terrestrial LiDAR to establish a rockfall inventory for the permafrost-affected rockwalls of two rapidly deglaciating cirques in the Central Alps of Austria (Kitzsteinhorn). During six-year monitoring (2011-2017) 78 rockwall scans were acquired. Overall, we registered 632 rockfalls ranging from 0.003 to 879.4 m3, which concentrate along pre-existing structural weaknesses. 60% of the rockfall volume detached from less than ten vertical meters above the glacier surface, indicating enhanced rockfall over tens of years following deglaciation. Antecedent rockfall preparation is assumed to start when the rockwall is still ice-covered: Inside the Randkluft (gap between cirque wall and glacier) sustained freezing and sufficient water supply likely cause enhanced weathering and high plucking stresses. Following deglaciation, pronounced thermomechanical strain is induced and an active layer penetrates into perennially frozen bedrock, likely contributing to the observed paraglacial rockfall increase close to the glacier surface. Observed mean cirque wall retreat of 1.9 mm a-1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the lowermost, freshly deglaciated sections of the investigated rockwalls. Rockfall magnitude-frequency distribution, which has never been quantified before for deglaciating cirques, follows a distinct negative power law distribution over four orders of magnitude. Magnitude-frequency distributions in glacier-proximal and glacier-distal rockwall sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. The present study thus demonstrates how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates an exhaustion law over decades for rockfall activity immediately following deglaciation crucial for future hazard assessments. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11955

2020063070 Hauck, Christian (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Hilbich, Christin; Mollaret, Coline and Pellet, Cécile. Permafrost monitoring by reprocessing and repeating historical geoelectrical measurements [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14047, 1 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Geophysical methods and especially electrical techniques have been used for permafrost detection and monitoring since more than 50 years. In the beginning, the use of Vertical Electrical Soundings (VES) allowed the detection of ice-rich permafrost due to the clear contrast between the comparatively low-resistive active layer and the high-resistive permafrost layer below. Only after the development of 2-dimensional tomographic measurement and processing techniques (Electrical Resistivity Tomography, ERT), in the late 1990's, electrical imaging was widely applied for a large range of different permafrost applications, including ice content quantification and permafrost monitoring over different spatial scales. Regarding ERT monitoring, the comparatively large efforts needed for continuous and long-term measurements implies that there are still only few continuous ERT monitoring installations in permafrost terrain worldwide. One of the exceptions is a network of six permafrost sites in the Swiss Alps that have been constantly monitored in the context of the Swiss Permafrost Monitoring Network (PERMOS) since 2005, enabling the analysis of the long-term change in the ground ice content and associated thawing and freezing processes (Mollaret et al. 2019). On the contrary, a much larger number (estimated to be > 500) of permafrost sites exist worldwide, where singular ERT (or VES) measurements have been performed in the past - many of them published in the scientific literature. These data sets are neither included in a joint database nor have they been analysed in an integrated way. Within a newly GCOS Switzerland-funded project we address this important historical data source. Whereas singular ERT data from different permafrost occurrences are not easily comparable due to the local influence of the geologic material on the obtained electrical resistivities, their use as baseline for repeated measurements and subsequent processing and interpretation in a climatic context is highly promising and can be effectuated with low efforts. In this presentation we will show evidence that singular ERT surveys in permafrost terrain can indeed be repeated and jointly processed after long time spans of up to 20 years, yielding a climate signal of permafrost change at various sites and on different landforms. Examples are given from various field sites in Europe and Antarctica, and the results are validated with borehole data, where available. We believe that a joint international data base of historical ERT surveys and their repetitions would add an important data source available for permafrost studies in the context of climate change. Mollaret, C., Hilbich, C., Pellet, C., Flores-Orozco, A., Delaloye, R. and Hauck, C. (2019): Mountain permafrost degradation documented through a network of permanent electrical resistivity tomography sites. The Cryosphere, 13 (10), 2557-2578. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14047

2020063137 Hiller, Clemens (Austrian Academy of Sciences, Institute for Interdisciplinary Mountain Research, Innsbruck, Austria); Helfricht, Kay; Schwaizer, Gabriele; Hohensinner, Severin; Wegner, Kerstin; Haas, Florian and Achleitner, Stefan. Bedload dynamics in the rapidly changing paraglacial zone of a high alpine catchment [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21253, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

High mountain environments have been confronted with rising temperatures and geomorphological changes over the past 150 years, with the considerable retreat of glaciers constituting one of the most pronounced impacts in the Alps. Concurrent degradation of permafrost in headwalls exposed from the downwasting ice and in periglacial hillslopes alongside glaciers causes increasing sediment flux onto glacier surfaces. The accumulation of supraglacial debris at the current glacier tongue promotes water-storage in debris-covered ice bodies and is assessed as an important source of sediment in the proglacial zone, since a close connection to the fluvial channel network can be assumed. The evolution of mountain streams, the degree of connectivity and conditional sedimentation-erosion effects significantly determine the dynamics in a generally unstable paraglacial landscape in which retreating glaciers provide high stream discharges while sediment is widely unconsolidated. In the recent scientific debate, the anticipated progressive shift from supply-limitation (fluvial transport overcapacity) to transport-limitation (abundance of sediment) in high alpine catchment areas is discussed. Thus, this study intends to contribute by investigating the connection of coarse sediment including supraglacial debris from the proglacial transition zone to downstream fluvial transport. Key aspect is the feedback between increasing debris cover and a shifting runoff regime due to a changing composition of glacier melt, snow melt and heavy rainfall events. In that respect, the focus will be on the dynamics of bedload transport and the proglacial coarse sediment budget. This study is part of the Hidden.Ice project and conducts in-depth monitoring of the connectivity, runoff measurements and geomorphological surveys at the LTER site Jamtalferner, Silvretta Range, Austria. Hydraulic modelling of the potential transport capacity supported by bedload trap measurements, the analysis of grain size distribution in the proglacial area and sediment volume changes calculated from UAV-based photogrammetry are aimed at raising knowledge on hydrological and geomorphological dynamics. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21253

2020063011 Hinzman, Alexa (Vrije Universiteit Amsterdam, Earth and Climate Department, Amstelveen, Netherlands); Sjoberg, Ylva; Lyon, Steve; Ploum, Stefan and van der Velde, Ype. Strong changes in the relationship between storage and discharge during a period of thawing soils and climate warming in northern Sweden [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10113, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is warming at an unprecedented rate. This warming affects not just ecosystems, but also permafrost, landscape configuration, and water availability in watersheds. One relatively under researched process is how seasonally frozen soils and changes thereof affect the water cycle. As frozen soils thaw, flow pathways within a catchment open, allowing for enhanced hydrologic connectivity between groundwater and rivers. As the connectivity of flow paths increase, the storage-discharge relationship of a watershed changes, which can be perceived within a hydrograph. More specifically, previous studies hypothesized that storage-discharge relationships are relatively linear when soils are frozen and become increasingly non-linear as the landscape thaws. The objective of our research is to expand on the assumption that soil thaw leads to increasingly non-linear storage-discharge relationships by quantifying trends and spatio-temporal differences of this relationship. We will present our analysis of sixteen watersheds within Northern Sweden throughout the years of 1951 and 2018. We focus on spring and summer storage-discharge relationships and show how they are affected by preceding winter conditions. We found a clear increase in non-linearity of the storage-discharge relationship over time for all catchments with twelve out of sixteen watersheds (75%) having a statistically significant increase in non-linearity. For twelve watersheds, spring relationships were significantly more linear compared to summer, which supports the hypothesis that seasonally frozen soils have less hydrological connectivity leading to more linear storage-discharge relationships. Winter conditions that allow deep soil frost lead to more linear storage-discharge relationships for ten watersheds. Overall, we show that thawing soil leads to a more non-linear storage-discharge relationship which implies river runoff in the Arctic becomes more unpredictable. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10113

2020063079 Hirschberg, Jacob (Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland); Fatichi, Simone; Bennett, Georgie; McArdell, Brian; Lane, Stuart and Molnar, Peter. Climate change impacts on sediment yield and debris-flow activity at the Illgraben, Switzerland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17017, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Debris flows are rapid mass movements composed of a mixture of water and sediments and often pose a danger to humans and infrastructure. In the Alpine environment, they are mostly triggered by intense rainfall, snowmelt or a combination thereof, and conditioned by sediment availability. Their occurrence is expected to increase in a warmer climate due to changes in the hydrological regime (e.g. higher rainfall intensity, lower duration of snow cover). Furthermore, sediment production is likely to accelerate due to permafrost thawing and changes in freeze-thaw cycles, resulting in increased sediment availability. For the purpose of climate change impact assessment on sediment yield and debris-flow activity, interactions and feedbacks of climate and the aforementioned processes need to be considered jointly. In the study presented here, we address this challenge by forcing a sediment cascade model (SedCas) with precipitation and temperature from a stochastic weather generator (AWE-GEN) producing ensembles of possible climate in the present and for the future. The chosen study site is the Illgraben, a debris-flow prone catchment in the Swiss Alps which currently produces 3-4 debris flows yearly on average. SedCas conceptualizes a geomorphic system in which hillslopes produce and store sediments from landslides and eventually deliver them to the channels. From there, sediments can be mobilized by concentrated surface runoff and transferred out of the catchment in form of bedload, hypreconcentrated flow, or debris flows, depending on the surface runoff magnitude and the sediment availability. AWE-GEN operates at the hourly scale and is trained for the current climate with observed data and for the future climate using the newest climate change projections for Switzerland CH2018 developed by the National Center for Climate Services. Preliminary results reveal a likely increase in debris-flow occurrence in the Illgraben in the future. Such an increase can be attributed to an extension in the debris-flow seasonal changes in the discharge regime. Furthermore, the number of landslides filling the sediment storage increases because they are affected by a shorter duration of snow cover and thus greater exposure to freeze-thaw weathering. However, projections are subject to large uncertainties, stemming not only from uncertainty in climate scenarios, but also from internal climate variability. Furthermore, the simplified hillslope weathering and debris-flow triggering mechanisms contribute to the overall uncertainty. Nevertheless, the methodology is thought to be transferable to any sediment-cascade-like catchment where dominant processes are driven by climate. Lastly, this work highlights the importance of considering stochasticity in climate and sediment history for projections of magnitudes and frequencies of relative rare events as debris flows. This allows us to explicitly separate climate change signals in geomorphic processes from fluctuations induced by internal natural variability. REFERENCES: Bennett, G. L., et al. "A probabilistic sediment cascade model of sediment transfer in the Illgraben." Water Resources Research 50.2 (2014): 1225-1244. doi: 10.1002/2013WR013806. Fatichi, S., et al. "Simulation of future climate scenarios with a weather generator." Advances in Water Resources 34.4 (2011): 448-467. doi: 10.1016/j.advwatres.2010.12.013. CH2018 - Climate Scenarios for Switzerland. National Centre for Climate Services (2018): doi: 10.18751/Climate/Scenarios/CH2018/1.0 [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17017

2020063062 Hölbling, Daniel (University of Salzburg, Department of Geoinformatics, Salzburg, Austria); Hennig, Sabine; Abad, Lorena; Ecke, Simon and Tiede, Dirk. Observation and reporting of landforms and landscape dynamics by citizens [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13593, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The observation and reporting of flora and fauna with the help of citizen scientists has a long tradition. However, citizen science projects have also a high potential for the reporting and mapping of landforms, as well as for observing landscape dynamics. While remote sensing has opened up new mapping and monitoring possibilities at high spatial and temporal resolutions, there is still a growing demand for gathering (spatial) data directly in the field (reporting on actual events, landform characteristics, and landscape changes, provision of reference data and photos). This becomes even more relevant since climate change effects (e.g. glacier retreat, shift of precipitation regime, melting of permafrost) will likely result in more significant morphological changes with an impact on the landscape. In the project citizenMorph (Observation and Reporting of Landscape Dynamics by Citizens; URL: http://citizenmorph.sbg.ac.at) we developed a pilot web-based interactive application that allows and supports citizens to map and contribute field data (spatial data, in-situ information, geotagged photos) on landforms. Such features are, for example, mass movements (e.g. rockfall, landslide, debris flow), glacial features (e.g. rock glacier, moraine, drumlin), volcanic features (e.g. lava flow, lahar, mudpot), or coastal features (e.g. cliff, coastal erosion, skerry). To design and implement a system that fully matches experts' and citizens' requirements, that ensures that citizens benefit from participating in citizenMorph, and that provides extensive, high-quality data, citizen representatives (mainly high school students, students, and seniors) actively and directly took part in the development process. These users are considered as particularly critical, sensitive to usability and accessibility issues, and demanding when it comes to using information and communication technology (ICT). In line with the concept of participatory design, citizen representatives were involved in all steps of the development process: specification of requirements, design, implementation, and testing of the system. The generation of a pilot was done using Survey123 for ArcGIS, a survey to collect data in the field, i.e. type and location of the landform, overview image and image series of the landform, and the content management system WordPress to create a website to inform, guide and support the participants. Throughout the survey (URL: https://arcg.is/15WPKv0) and the website, different kinds of information (e.g. project information, guidelines for data collection and reporting, data protection information) are given to the participants. The final citizenMorph system was tested and discussed on several events with citizen representatives in Austria, Germany, and Iceland. Feedback from the tests was gathered using techniques such as observation, focus groups, and interviews/questionnaires. This allowed us to evaluate and improve the system as a whole. The collected data, particularly the image series, are used for 3D reconstruction of the surface using Structure from Motion (SfM) and dense image matching (DIM) methods. Moreover, the collected data can be helpful for enriching and validating remote sensing based mapping results and increasing their detail and information content. Having a comprehensive database, holding field data and remote sensing data together, is of importance for any subsequent analysis and for broadening our knowledge about geomorphological landscape dynamics and the prevalence of landforms. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13593

2020063140 Holmstrand, Henry (Stockholm University, Stockholm, Sweden); Shakhova, Natalia; Semiletov, Igor; Steinbach, Julia; Kurilenko, Arkadiy; Salyuk, Anatoly; Kosmach, Denis; Chernykh, Denis; Koshurnikov, Andrey; Tumskoy, Vladimir; Lobkovsky, Leopold and Gustafsson, Orjan. Siberian-Arctic subsea permafrost and methane; spatial variability and isotope-based source apportionment [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21660, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

There are only a few Earth System processes that can cause a net transfer of carbon from land/ocean to the atmosphere (as CO2 and CH4) on the century timescale- top candidates are thawing permafrost and collapsing CH4 hydrates in the Arctic. Nevertheless, there are huge uncertainties regarding the composition, inventories and functioning of these different Cryosphere-Carbon pools. Most investigations of Arctic CH4/CO2 releases have studied inland permafrost (PF), yet there is increasing attention towards coastal and subsea permafrost and hydrates. The East Siberian Arctic Ocean (ESAO) is the target area as it is experiencing among the highest climate warming and because of its vast, yet poorly constrained stores of vulnerable carbon. The ESAO is the largest yet shallowest shelf of the World Ocean, being a seaward extension of the Siberian tundra that was flooded during the Holocene transgression 7-15 kyr ago. Recent drilling campaigns of the Laptev Sea subsea permafrost have provided the opportunity for progress in understanding its current state, composition and functioning. The temperature profiles of the PF underneath the coastal waters were in general much higher and close to zero, compared to nearby still on-land permafrost. Several sites that were drilled 30 years ago were recently re-drilled, which revealed that the thaw horizon has been moving down by several meters in just a few decades. There is thus both a potential for degradation of the organic matter (including to methane) in this subsea PF as well as an increasing permeability for pre-formed methane to penetrate toward the surface. Methane in the ESAS water column is over extensive scales present at concentrations much above what would be predicted from equilibrium with overlying atmospheric mixing ratios. The spatial patterns can now start to be compared with geophysical data on the composition of the sediments. The water column to atmosphere transfer of methane is affected both by the relative importance of diffusive exchange of dissolved methane and through ebullition. Storm-induced ventilation of the water column is shown to be an important process. The relative contributions of different subsea compartments to the methane fluxes is also approached through isotopes. We are exploring triple isotope fingerprinting of bottom water methane to apportion its sources (i.e. d13C/dD/D14C-CH4.). Preliminary results from two active seep regions, one in Laptev Sea and one in the East Siberian Sea will be presented. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21660

2020063059 Johansson, Margareta (Lund University, Lund, Sweden); Akerman, Jonas; Blume-Werry, Gesche; Callaghan, Terry V.; Christensen, Torben R.; Monteux, Sylvain and Dorrepaal, Ellen. 15 years of snow manipulation reveals huge impact on lowland permafrost and vegetation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13137, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Snow depth increases observed and predicted in the sub-arctic are of critical importance for the dynamics of lowland permafrost and vegetation. Snow acts as an insulator that protects vegetation but may lead to permafrost degradation. In the Abisko area, in northernmost Sweden, there has been an increasing trend in snow depth during the last Century. Downscaled climate scenarios predict an increase in precipitation by 1.5-2% per decade for the coming 60 years. The observed changes in snow cover have affected peat mires in this area as thawing of permafrost, increases in active layer thickness and associated vegetation changes have been reported during the last decades. An experimental manipulation was set up at one of these lowland permafrost sites in the Abisko area (68°20'48"N, 18°58'16"E) 15 years ago, to simulate projected future increases in winter precipitation and to study their effect on permafrost and vegetation. The snow cover has been more than twice as thick in manipulated plots compared to control plots and it has had a large impact on permafrost and vegetation. It resulted in statistically significant differences in mean winter and minimum ground temperatures between the control and the manipulated plots. Already after three years there was a statistically significant difference between active layer thickness in the manipulated plots compared to the control plots. In 2019, the active layer thickness in the control plots were around 70 cm whereas in the manipulated plots it was 110 cm. The increased active layer thickness has led to surface subsidence due to melting of ground ice in all the manipulated plots. The increased snow thickness has prolonged the duration of the snow cover in spring with up to 22 days. However, this loss in early season photosynthesis was well compensated for by the increased absorption of PAR and higher light use efficiency throughout the whole growing seasons in the manipulated plots. Eriophorum vaginatum is a species that has been especially favored in the manipulated plots. It has increased both in number and in size. Underneath the soil surface, the roots have also been affected. There has been a strong increase in total root length and growth in the active layer, and deep roots has invaded the newly thawed permafrost in the manipulated plots. The increased active layer thickness has also had an effect on the bacterial community composition in the newly thawed areas. According to past, century-long patterns of increasing snow depth and projections of continuing increases, it is very likely that the changes in permafrost and vegetation that have been demonstrated by this experimental treatment will occur in the future under natural conditions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13137

2020063041 Jones, Benjamin (University of Alaska Fairbanks, Institute of Northern Engineering, Water and Environmental Research Center, Fairbanks, AK). Strengthening connections across disciplines and borders through an international permafrost coastal systems network (PerCS-Net) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11935, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Changes in the Arctic system have increased the vulnerability of permafrost coasts to erosion and altered coastal morphologies, ecosystems, biogeochemical cycling, infrastructure, cultural and heritage sites, community well-being, and human subsistence lifestyles. Better understanding the pace and nature of rapid changes occurring along permafrost coastlines is urgent, since a high proportion of Arctic residents live on or near coastlines, and many derive their livelihood from terrestrial and nearshore marine resources The US National Science Foundation's AccelNet and Arctic System Sciences Programs, recently awarded a collaborative grant funding the Permafrost Coastal Systems Network (PerCS-Net). PerCS-Net focuses on leveraging resources from existing national and international networks that have a common vision of better understanding permafrost coastal system dynamics and emerging transdisciplinary science, engineering, and societal issues in order to amplify the broader impacts by each individual network. PerCS-Net strengthens linkages between existing networks based in Germany, Russia, Norway, Denmark, Poland, and Canada with the activities of several active US NSF-funded networks as well as several local, state, and federally funded US-based networks. PerCS-Net will benefit the US and international research communities by (1) developing internationally recognized protocols for quantifying the multitude of changes and impacts occurring in Arctic coastal permafrost systems, (2) sustaining long-term observations from representative coastal key sites, (3) unifying annual and decadal-scale observations of circum-arctic permafrost-influenced coasts, (4) refining a circum-arctic coastal mapping classification system and web-based delivery of geospatial information for management planning purposes and readily accessible information exchange for vulnerability assessments, (5) engaging local communities and observers to capture impacts on subsistence and traditional livelihoods, and (6) promoting synergy across networks to foster the next generation of students, postdoctoral scholars, and early-career researchers faced with the known and unknown challenges of the future Arctic System. Ultimately, PerCS-Net will develop a circumpolar alliance for Arctic coastal community information exchange between stake-, rights- and knowledge holders, scientists, and land managers. There is increasingly diverse interest in permafrost coastal system issues and currently no unified source of information on the past, present, and potential future state of permafrost coastal systems that provide the level of detail needed to make decisions at scales relevant for indigenous communities across the Arctic. Such new engagement will inform intergovernmental agencies and international research and outreach programs in making science-based decisions and policies to adapt to changing permafrost coastal system dynamics. PerCS-Net will build a network of networks to assess risks posed by permafrost coastal system changes to local and global economies and well-being and facilitate knowledge transfer that will lead to circum-arctic adaptation strategies. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11935

2020063098 Jonsson, Elisie (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Ghajarnia, Navid; Hugelius, Gustaf and Kalantari, Zahra. Mapping of Arctic wetlands with threats of future permafrost thaw [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18208, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is warming twice as fast as the rest of the globe, causing changes to Arctic ecosystems. While wetlands in the Arctic provide many ecosystem services with both local and global importance, still more knowledge is needed on the location and state of Arctic wetlands to successfully focus adaptation and mitigation efforts. To understand the links between temperature changes and changes to Arctic wetlands, this study includes the use of spatial tools to map existing wetlands and model permafrost response to temperature changes, highlighting wetland areas with risks of future changes. Using available high-resolution wetland databases together with soil wetness and soil type data, a wetland map covering the Arctic was created. Based on existing relationships between climate and observed permafrost, future changes in permafrost were modeled using projected mean annual temperature from the HadGEM2-ES climate model outputs for the RCP2.6, 4.5 and 8.5 scenarios and for years 2050, 2075 and 2100. We found that the Arctic contains a large number of wetlands and a very significant number of these exist on permafrost. As substantial permafrost thaw is projected, the extent and properties of wetlands will shift, and local/regional increases or decreases in wetland extent will depend on variables such as soil type. These changes could lead to serious local consequences, such as threats to food and water security, changes in distribution and demographics of animal and plant species, and losses and disruptions of infrastructure. The findings of this study highlight vulnerable areas that need extra attention in terms of adaptation and mitigation efforts to limit the likely impacts of projected changes, given the current trends. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18208

2020063052 Kashi, Natalie N. (University of New Hampshire, Institute for the Study of Earth, Ocean, and Space, Earth Systems Research Center, Durham, NH); Varner, Ruth K.; Thorp, Nathan R.; Knorr, Melissa A.; Wymore, Adam S.; Ernakovich, Jessica G.; Hobbie, Erik A. and Giesler, Reiner. Nutrients unlocked from permafrost thaw affect microbial methane metabolism [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12521, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The biological conversion of frozen carbon-rich soil (permafrost) into greenhouse gases such as carbon dioxide could cause a positive feedback to climate change. Another significant consequence of permafrost thaw is the collapse of soil structure and subsequent higher water table that can shift vegetation toward water-adapted plant communities that emit high concentrations of methane (CH4). Plants and microbes respond rapidly to labile carbon (C) and nitrogen (N) released from permafrost thaw, however, the microbial response to phosphorus (P) is unknown. Here we investigated how the nutrient status of permafrost and peat affect microbial activities in four minerotrophic communities in a peatland undergoing permafrost thaw. We experimentally fertilized soils in vitro with a permafrost soil slurry, inorganic P, organic N, or organic N and P. This method isolated the effect of permafrost thaw on microbial processes by removing the confounding effect of plant-soil interactions. The four peatland communities include 1. palsas (intact permafrost mounds rising above the surrounding peatlands), 2. pockets of collapsed palsas dominated by Sphagnum fuscum, 3. adjacent eutrophic Sphagnum-dominated lawns with thawing permafrost and 4. inundated, sedge-dominated minerotrophic fens with no permafrost remaining. Permafrost had high extractable inorganic N concentrations, averaging 30 mg N g-1 soil dry weight (dw), whereas extractable P concentrations were low, averaging 1.4 mg P g-1 soil dw. While N concentrations in the permafrost were over four times the concentration in adjacent peatland communities, extractable P concentrations were relatively lower. Sphagnum lawns positioned at the base of palsas, had nine times the extractable P concentrations averaging 12.6 mg P g-1 soil dw compared to the permafrost, suggesting that P availability increases as permafrost thaws. However, in the fen where no permafrost remains, extractable P concentrations were again low, 2.4 mg P g-1 soil dw, despite high total P. These fen communities are also marked by higher iron concentrations, likely resulting in P immobilization by higher concentrations of metals. The addition of inorganic P and the combination of organic N and P in these fen sites strongly enhanced CH4 oxidation rates while organic N did not, indicating the importance of P for these energy intensive transformations. Nutrient amendments did not have a significant effect on CH4 production rates, however, permafrost slurries significantly decreased CH4 production in Sphagnum lawn communities, suggesting an unknown inhibitory effect of permafrost chemistry on CH4 production. The results of our study highlight the effects of permafrost degradation on nutrient release and provide new insight into how nutrients unlocked from permafrost affects greenhouse gases. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12521

2020063130 Kienast, Frank (Senckenberg Research Institute and Natural History Museum, Weimar, Germany); Ashastina, Kseniia; Kuzmina, Svetlana and Rudaya, Natalya. Vegetation at the northern pole of cold during the climate extremes of the late Pleistocene; fossil records from the Batagay mega thaw slump, Yakutia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20513, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Batagay mega slump is the largest active thaw slump on the planet. Enormously rapid thermal erosion gave access to permafrost sediments that deposited since the Middle Pleistocene. Permafrost is an excellent medium for the preservation of ancient organic matter. The Batagay exposure is well known for some spectacular findings of Pleistocene megaherbivore carcasses including the youngest steppe bison found in Eurasia so far, dated to 8.2 ka BP. The extraordinarily long sequence of Pleistocene deposits in Batagay is therefore an excellent archive of the palaeoenvironmental history in the Yana highlands - a region with uniquely stable cold-continental climate known as the pole of cold in the northern hemisphere. This region is regarded as refugial area for extrazonal steppe plants and now extinct large grazers together constituting the Pleistocene mammoth steppe, which covered vast areas in high and mid latitudes of the northern hemisphere during cold stages. Modern vegetation around the study site consists of light taiga mainly composed of larch, shrub alder, shrub birches and stone pine. To understand the processes that resulted in the demise of Pleistocene megafauna and in the biological turnover during the late Quaternary, we reconstructed vegetation and environmental conditions during the two climate extremes of the late Pleistocene, the onset of the last glacial maximum and the last interglacial using remains of plants and insects preserved in organic-rich material. The results from studies of plant material gathered in a fossil ground squirrel nest suggest that grassland vegetation corresponding to modern meadow steppes in Central Yakutia and northern Mongolia existed in the study area during the last cold stage. During the last interglacial, open coniferous woodland similar to modern larch taiga was the primary vegetation at the site. Abundant charcoal indicates wildfire events during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially by the abundant nitrophytic Urtica dioica, suggesting that the area was an interglacial refugium for large herbivores. Meadow steppes, which formed the primary vegetation during cold stages and provided potentially suitable pastures for herbivores, were a significant constituent of the plant cover in the Yana Highlands also under the full warm stage conditions of the last interglacial. Consequently, meadow steppes occurred in the Yana Highlands during the entire investigated timespan of the Pleistocene documenting a remarkable environmental stability. The documented fossil record also proves that modern steppe occurrences in the Yana Highlands did not establish as late as in the Holocene, as suggested by some scholars, but instead are relicts of a formerly continuous steppe belt extending from Central Siberia to Northeast Yakutia during the Pleistocene. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20513

2020063060 Kikstra, Jarmo (International Institute for Applied Systems Analysis, Laxenburg, Austria); Waidelich, Paul; Rising, James; Yumashev, Dmitry; Hope, Chris and Brierley, Chris. Climate-economy feedbacks, temperature variability, and the social cost of carbon [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13230, 9 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

A key statistic describing climate change impacts is the "social cost of carbon" (SCC), the total market and non-market costs to society incurred by releasing a ton of CO2. Estimates of the SCC have risen in recent years, with improved understanding of the risk of climate change to various sectors, including agriculture [1], mortality [2], and economic growth [3]. The total risks of climate impacts also depend on the representation of human-climate feedbacks such as the effect of climate impacts on GDP growth and extremes (rather than a focus only on means), but this relationship has not been extensively studied [4-7]. In this paper, we update the widely used PAGE IAM to investigate how SCC distributions change with the inclusion of climate-economy feedbacks and temperature variability. The PAGE model has recently been improved with representations of permafrost thawing and surface albedo feedback, CMIP6 scenarios, and empirical market damage estimates [8]. We study how changes from PAGE09 to PAGE-ICE affected the SCC, increasing it up to 75%, with a SCC distribution with a mean around $300 for the central SSP2-4.5 scenario. Then we model the effects of different levels of the persistence of damages, for which the persistence parameter is shown to have enormous effects. Adding stochastic interannual regional temperature variations based on an analysis of observational temperature data [9] can increase the hazard rate of economic catastrophes changes the form of the distribution of SCC values. Both the effects of temperature variability and climate-economy feedbacks are region-dependent. Our results highlight the importance of feedbacks and extremes for the understanding of the expected value, distribution, and heterogeneity of climate impacts.

DOI: 10.5194/egusphere-egu2020-13230

2020063138 Kirdyanov, Alexander (Russian Academy of Sciences, Siberian Branch, V. N. Sukachev Institute of Forest, Krasnoyarsk, Russian Federation); Prokushkin, Anatoly; Knorre, Anastasia; Churakova, Olga Sidorova; Fonti, Marina; Saurer, Matthias; Siegwolf, Rolf; Reinig, Frederick; Nikolaev, Anatoly; Kolmogorov, Alexey; Shishov, Vladimir; Piermattei, Alma; Krusic, Paul and Büntgen, Ulf. Does permafrost matter? Permafrost related studies of conifer tree-ring growth in northern Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21434, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The world's largest terrestrial biome, Boreal forest, is prone to the greatest rates of recent and predicted warming. Much of this circumpolar vegetation belt is underlain by permafrost, which further challenges our understanding of the direct and indirect consequences of increasing temperature on the functioning and productivity of these northern latitudinal forests. Here, we present the results of an on-going study of tree-ring growth of conifers in Russia's continuous permafrost zone in northern Siberia, from 61-72°N and 90-148°E. Tree-ring data from a variety of habitats between 20 and 600 m asl with different climate and thermo-hydrological regimes of soils are analyzed. While in some cases up to 60-70% of the year-to-year tree-ring width and maximum latewood density variability can be explained by summer temperature variations alone, we find that the seasonal dynamics of permafrost also plays an important role in defining the overall rate of radial tree growth. Wider rings are generally formed on sites with a deeper active soil layer, which itself depends on the geographical location of a site, as well as its ground vegetation, stand parameters and fire history. Waterlogged permafrost may further act as a source of water for trees under exceptionally dry summer seasons. Our study indicates that the growth response of conifers to temperature and precipitation across the continuous permafrost zone of Siberia is both, site- and species-specific. This implies a range of possible scenarios of further development of northern forests under projected climate change. Seasonal dynamics of the active soil layer and possible permafrost degradation must be taken into account when modelling tree growth variability and forest productivity. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21434

2020063051 Kokelj, Steve (Northwest Territories Geological Survey, Yellowknife, NT, Canada); Kokoszka, Justin; Van der Sluijs, Jurjen; Rudy, Ashley; Tunnicliffe, Jon; Shakil, Sarah; Tank, Suzanne and Zolkos, Scott. Slope thermokarst transforms permafrost preserved glacial landscapes and effects propagate through Arctic drainage networks [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12498, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Recent intensification of slope thermokarst is transforming permafrost preserved glaciated landscapes and causing significant downstream effects. In this paper we: A) Describe the thaw-related mechanisms driving the evolution of slope to stream connectivity; B) define the watershed patterns of thermokarst intensification; and C) project the cascade of effects through the Arctic drainage networks of northwestern Canada. The power-law relationships between disturbance area and volume, and thickness of permafrost thawed, in conjunction with a time-series of disturbance mapping show that the non-linear intensification of slope thermokarst is mobilizing vast stores of previously frozen glacial sediments linking slopes to downstream systems. Mapping across a range of catchment scales indicates that slope thermokarst predominantly affects first and second order streams. Slope sediment delivery now frequently exceeds fluvial transport capacity of these streams by several orders of magnitude indicating long-term perturbation. Mapping shows slope thermokarst is directly affecting over 6760 km of stream segments, over 890 km of coastline and over 1370 lakes across the 1,000,000 km2 Arctic drainage basin from continuous permafrost of northwestern Canada. The downstream projection of thermokarst disturbance increases affected lakes by a factor of 4 and stream length by a factor of 7, and suggests that fluvial transfer has the potential to yield numerous thermokarst impact zones across coastal areas of western Arctic Canada. The Prince of Wales Strait between Banks and Victoria Islands is identified as a hotspot of downstream thermokarst effects, and the Peel and Mackenzie rivers stand out as principle conveyors of slope thermokarst effects to North America's largest Delta and to the Beaufort Sea. The distribution of slope thermokarst and the fluvial pattern of sediment mobilization signal the climate-driven rejuvenation of post-glacial landscape change and the triggering of a time-transient cascade of downstream effects. Geological legacy and the patterns of continental drainage dictate that terrestrial, freshwater and marine environments of western Arctic Canada will be a hotspot of climate-driven change through the coming centuries. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12498

2020062992 Kostrova, Svetlana (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Meyer, Hanno; Pestryakova, Luidmila; Biskaborn, Boris; Fernandoy, Francisco and Baumer, Marlene. Environmental and climate dynamics in northeastern Siberia according to diatom oxygen isotopes [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8574, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The sedimentary sequence from Lake Emanda (65°17'N; 135°45'E; 675 m a.s.l), one large freshwater body (33.1 km2) in the continuous permafrost of the Verkhoyansk Mountains, has been investigated within the German-Russian "Paleolimnological Transect" (PLOT) project. It provided important insight into the environmental and climate dynamics in northeastern Siberia. Well preserved diatoms occur only in the upper 125-cm interval of a 6.1-m sediment core (Co1412) covering the last ca. 13.4 cal. ka BP, and are mostly dominated by Cyclotella iris (up to 84%). The diatom succession is enriched by fragilarioid assemblages in the interval from ca. 11.0 to 13.0 cal. ka BP, while Aulacoseira ambigua is more frequent between 8.5 and 6.5 cal. ka BP. Diatoms were purified to > 98% SiO2 and < 0.8% Al2O3 suitable for oxygen isotope (d18Odiatom) analysis. The d18Odiatom values were corrected for contamination and range between +22.5 ppm and +27.3 ppm. Maximum d18Odiatom values (+26.7 to +27.3 ppm) are registered between 9.0 and 9.9 cal. ka BP and probably reflect a thermal maximum and/or very dry conditions in Early Holocene. The absolute minimum (+22.5 ppm) in the d18Odiatom record is marked at 0.4 cal. ka BP and likely corresponds to the Little Ice Age. In general, a gradual depletion of 4.8 ppm in d18Odiatom is observed within the last 10 cal. ka, in line with an overall Holocene temperature decrease. Our conclusions are based on a comprehensive investigation of both the modern hydrological system and diatom species analyses. The most recent d18Odiatom = +24.2 ppm combined with the present day lake water isotope composition (mean d18Olake = -16.5 ppm), indicates a reasonable water-silica isotope fractionation (a = 1.0414) yielding a water temperature of 12 °C. The data demonstrate that the d18Odiatom variability is associated with changes in the lake water isotopic composition rather than with lake temperature. The present water isotopic composition of Lake Emanda displays substantial evaporation effects, likely further influenced by air temperature and atmospheric circulation. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8574

2020063054 Koutnik, Michelle (University of Washington, Earth and Space Sciences Department, Seattle, WA); Fabbi, Nadine; Wessells, Elizabeth; Ahlness, Ellen; Showalter, Max; Mandeville, Dan; Young, Jason and Steen-Larsen, Hans Christian. Arctic ice in cross-disciplinary undergraduate education; experiences across natural science, social science, international policy, and public writing [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12600, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With the Arctic currently warming at a rate at least twice that of the global average, the coupled Arctic ecosystem is losing ice. This includes significant land-ice loss from the Greenland Ice Sheet and Arctic ice caps and glaciers, reduction in extent and thickness of Arctic sea ice, and thawing permafrost. This scale of environmental change significantly affects Arctic people, wildlife, infrastructure, transportation, and access. Societal response to these changes relies on advances in and application of research spanning multiple scientific disciplines, with policy-making done in partnership with Indigenous people, governments, private agencies, multinational corporations, and other interested groups. Everyone will interface with outcomes due to a changing climate and the challenge is mounting for the next generation of leaders. The cross-disciplinary nature of the challenge of Arctic ice loss and climate change must be met by cross-disciplinary undergraduate education. While higher education aims for disciplinary training in natural sciences and social sciences, there is an increasing responsibility to integrate topics and immerse students in real-world issues. And, in our experience the undergraduates we teach are eager for courses that can do this well. What is immersive undergraduate education? We consider this as either immersing students in a focused topic in the classroom, immersing students in a place (especially while abroad), or combining the two through targeted lectures, informed discussions, travel, and writing. With regard to the Arctic, it is necessary to bring scientific understanding to learning activities otherwise focused on societal impacts, policy making, and knowledge exchange through public writing. We share from our practical experience teaching Arctic-focused courses to classes each with 10-30 students with majors from across the University of Washington (UW) campus (total undergraduate student body of 32,000). Three recent activities that integrate the state of science with impacts on society in undergraduate courses include: 1) a four-week study abroad course to Greenland and Denmark focusing on changes in the Greenland Ice Sheet and sea-level rise, 2) a 10-week Task Force course in Arctic Sea Ice and International Policy in partnership with the UW International Policy Institute at the Henry M. Jackson School of International Studies that includes one-week in Ottawa where students develop a mock Arctic sea ice policy for Canada consistent with Inuit priorities, and 3) a 10-week seminar in public writing where students write mock newspaper articles, book reviews, and policy summaries about ice in a changing climate. These courses were designed to include a similar subset of earth science, atmospheric science, and oceanography, but the distinct structure and application of the science in these three separate courses led to distinct learning outcomes. In addition, we present how the academic minor in Arctic Studies at the University of Washington has allowed students to design their own integrated understanding of Indigenous and nation-state Arctic geopolitics, Arctic environmental change, and policy by taking a selection of courses and engaging in research and report writing. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12600

2020063085 Krautblatter, Michael (Technical University of Munich, Landslide Research, Munich, Germany); Jacobs, Benjamin; Mamot, Philipp; Pläsken, Regina; Scandroglio, Riccardo; Gross, Julian and Schröder, Tanja. Towards a benchmark mechanical model for warming permafrost rock slopes [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17616, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

This paper discusses mechanical modelling strategies for instable permafrost bedrock. Modelling instable permafrost bedrock is a key requirement to anticipate magnitudes and frequency of rock slope failures in a changing climate but also to forecast the stability of high-alpine infrastructure throughout its lifetime. High-alpine rock faces witness the past and present mechanical limit equilibrium. Rock segments where driving forces exceed resisting forces fall of the cliff often leaving a rock face behind which is just above the limit equilibrium. All significant changes in rock mechanical properties or significant changes in the state of stress will evoke rock instability which often occurs with response times of years to 1000 years. Degrading permafrost will act to alter (i) rock mechanical properties such as compressive and tensile strength, fracture toughness and most likely rock friction, (ii) warming sub zero conditions will weaken ice and rock-ice interfaces and (iii) increased cryo- and (iv) hydrostatic pressures are expected. We have performed hundreds of laboratory experiments on different types of rock that show that thawing and warming significantly decreases both, rock and ice-mechanical strength between -5°C and -0.0°C. Approaches to calculate cryostatic pressure (ad iii) have been published and are experimentally confirmed. However, the importance and dimension of extreme hydrostatic forces (ad iv) due to perched water above permafrost-affected rocks has been assumed but has not yet been quantitatively recorded. This paper presents data and strategies how to obtain relevant (i) rock mechanical parameters (compressive and tensile strength and fracture toughness, lab), (ii) ice- and rock-ice interface mechanical parameters (lab), (iii) cryostatic forces in low-porosity alpine bedrock (lab and field) and (iv) hydrostatic forces in perched water-filled fractures above permafrost (field). We demonstrate mechanical models that base on the conceptual assumption of the rock ice mechanical model (Krautblatter et al. 2013) and rely on frozen/unfrozen parameter testing in the lab and field. Continuum mechanical models (no discontinuities) can be used to demonstrate permafrost rock wall destabilization on a valley scale over longer time scales, as exemplified by progressive fjord rock slope failure in the Lateglacial and Holocene. Discontinuum mechanical models including rock fracture patterns can display rock instability induced by permafrost degradation on a singular slope scale, as exemplified for recent a recent ice-supported 10.000 m3 preparing rock at the Zugspitze (D). Discontinuum mechanical models also have capabilities to link permafrost slope stability to structural loading induced by high-alpine infrastructure such as cable cars and mountains huts, as exemplified for the Kitzsteinhorn Cable Car and its anchoring in permafrost rocks (A). Over longer time scales, the polycyclicity of hydro- and cryostatic forcing as well as material fatigue play an important role. We also introduce a mechanical approach to quantify cryo-forcing related rock-fatigue. This paper shows benchmark approaches to develop mechanical models based on a rock-ice mechanical model for degrading permafrost rock slopes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17616

2020063075 Kroisleitner, Christine (b.geos, Korneuburg, Austria); Bartsch, Annett; Heim, Birgit and Wiezorek, Mareike. The potential of satellite derived surface state to empirically estimate pan-Arctic ground temperature at specific depths and the essential role of in-situ data [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-15162, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Surface state information, derived from ASCAT microwave sensors (C-band scatterometer), were empirically linked to in-situ arctic ground temperature measurements. The resulting FT2T-regression model was established using the sum of days of year frozen and in-situ mean annual ground temperatures, both at specific depths and years. Regionally, the model showed the best results in Scandinavia and northern Russia with less than 1°C difference to the in-situ data. Overall, the results were valid for most depths and regions, with a slight tendency for underestimation of the ground temperatures on the Eurasian continent (about -1°C) and an overestimation on the American continent up to 2 °C. The most northern parts of Greenland, the Canadian High Arctic Islands and Alaska, however, showed a high positive bias of more than 10°C. Reasons for this overshooting include the limited amount of measurements in those regions, the oceanic influence and possibly snow cover effects. Due to the inaccessibility of many arctic regions, in-situ data availability is still sparse and if available not harmonized. We used the currently revised annual ground temperature dataset from CCI+ Permafrost, which combines in-situ data from the GTNP-database, RosHydroMet and additional regional arctic ground temperature datasets (e.g. Nordicana). The resulting determination coefficients of the FT2T-model showed 55% explained variance at shallow borehole-depths below 80 cm and decrease with depth to around 25% at 20 meters. This suggests that the sum of frozen days of year delivers better result at shallow depths in the active layer than at the actual permafrost table. The RMSE showed a dependency on the spread of measurement stations considered in the model calibration step. The more input regions we could use, the larger the RMSE got due to the increase of variability in the input data. Inevitably, it's the in-situ information which enables the translation between ground temperatures and microwave backscatter and thus it fundamentally affects the accuracy of the result. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-15162

2020063068 Kumpula, Timo (University of Eastern Finland, Geography Department, Joensuu, Finland); Laptander, Roza and Forbes, Bruce C. Impacts of infrastructure and climate changes on reindeer herding in the Yamal, West Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13995, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The traditional landuse in the Yamal is reindeer herding practiced by nomadic Nenets herders. The hydrocarbon industry is presently the source of most ecological changes in the Yamal peninsula and socio-economic impacts experienced by migratory Nenets herders who move annually between winter pastures at treeline and the coastal summer pastures by the Kara Sea. In central Yamal peninsula which is permafrost area both natural and anthropogenic changes have occurred during the past 40 years. Mega size Bovanenkovo Gas Field was discovered in 1972 and it was opened in production and in 2012. We have studied gas field development and natural changes like increases in shrub growth, cryogenic landslides, drying lakes in the region and these impacts to Nenets reindeer herding. Nenets managing collective and privately owned herds of reindeer have proven adapt in responding to a broad range of intensifying industrial impacts at the same time as they have been dealing with symptoms of a warming climate and thawing permafrost phenomena. The results of climate change together with the industrial development of the Yamal Peninsula have a serious impact to the Nenets nomadic reindeer husbandry. Their consequences make Nenets reindeer herders to change their migration routes and the way of working with reindeer. During several years, we were making interviews with Nenets reindeer herders about the influence of climate change and industrialization of the tundra on the quality of Nenets nomads' life and their work with reindeer. Reindeer herders said that impacts of industrial development have reduced their migration opportunities, as well as the quality of pastures for grazing, which has fatal the effects during icing on the tundra in the winter. At the same time, in the summer reindeer have more food because increasing of the green vegetation. Here we detail both the climate change impacts and spatial extent of gas field growth, landslides drying lakes, shrub increase and the dynamic relationship between Nenets nomads and their rapidly evolving social-ecological system. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13995

2020063071 Kunz, Julius (University of Wuerzburg, Institute for Geography and Geology, Wuerzburg, Germany); Kneisel, Christof; Ullmann, Tobias and Baumhauer, Roland. Multi-methodological investigation of a retrogressive thaw slump in the Richardson Mountains, Northwest Territories, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14201, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Mackenzie-Delta Region is known for strong morphological activity in context of global warming and permafrost degradation, which reveals in a large number of retrogressive thaw slumps. These are frequently found along the shorelines of inland lakes and the coast; however, this geomorphological phenomenon also occurs at inland streams and creeks of the Peel Plateau and the Richardson Mountains, located in the southwest of the delta. Here several active retrogressive thaw slumps are found of which some have reached an extent of several hectares, e.g. the mega slump at the Dempster Creek. In this study we investigated a recent retrogressive thaw slump at the edge of the Richardson Mountains close to the Dempster Highway to determine the subsurface properties using non-invasive geophysical methods. We performed three-dimensional Ground Penetrating Radar (GPR) surveys, as well as quasi-three-dimensional Electrical Resistivity Tomography (ERT) surveys in order to investigate the subsurface characteristics adjacent to the retreating headwall of the slump. These measurements provide information on the topography of the permafrost table, ice content and/or water pathways on top, within or under the permafrost layer. Additionally, we performed manual measurements of the active layer thickness for validation of the geophysical models. The approach was complemented by the analysis of high-resolution photogrammetric digital elevation models (DEM) that were generated using in situ drone acquisitions. The measured active layer depths show a strong influence of the relief and especially of small creeks on the permafrost table topography. Likely, this influence also is the primary trigger for the initial slump activity. In addition, the ERT measurements show strong variations of the electrical resistivity values in the upper few meters, which are indicative for heterogeneities, also within the ice-rich permafrost body. Especially noticeable is a layer of low resistivity values in an area adjacent to the slump headwall. This layer is found at depths between 4m to 7m, which approximately corresponds to the base of the headwall. Here, the low resistivity values could be indicative for an unfrozen or water-rich layer below the ice-rich permafrost. Consequently, this layer may have contributed to the initial formation of the slump and is important for the spatial extension of the slump. These results present new insights into the subsurface of an area adjacent to an active retrogressive thaw slump and may contribute to a better understanding of slump development. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14201

2020063095 Kutzbach, Lars (Universität Hamburg, Institute of Soil Science, Hamburg, Germany); Rössger, Norman; Eckhardt, Tim; Knoblauch, Christian; Sachs, Torsten; Wille, Christian; Boike, Julia and Pfeiffer, Eva-Maria. Spatiotemporal variability of methane emissions of tundra landscapes in the Lena River delta, Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17937, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Increased methane (CH4) release from a warming Arctic is expected to be a major feedback on the global climate. However, due to the complex effects of climate change on arctic geoecosystems, projections of future CH4 emissions are highly uncertain. CH4 emissions from complex tundra landscapes will be controlled not only by direct climatic effects on production, oxidation and transport of CH4 but, importantly, also by geomorphology and hydrology changes caused by gradual or abrupt permafrost degradation. Therefore, improving our understanding of both the temporal dynamics and the spatial heterogeneity of CH4 fluxes on multiple scales is still necessary. Here, we present pedon- and landscape-scale CH4 flux measurements at two widespread tundra landscapes (active floodplains and late-holocene river terraces) of the Lena River Delta in the Siberian Arctic (72.4°N, 126.5°E). The dominating scales of spatial variability of soil, vegetation and CH4 fluxes differ between the two landscapes of different geological development stage. The active floodplains are characterized by sandy beaches and ridges, and backswamp depressions, forming a mesorelief with height differences of several meters on horizontal scales of 10-1000 m. On the other hand, the river terraces are characterized by the formation of ice-wedge polygons, which lead to a regular microrelief with height differences of several decimeters on horizontal scales of 1 to 10 meters. CH4 fluxes were investigated on the landscape scale with the eddy covariance method (15 campaigns during 2002-2018 at the river terrace, 2 campaigns 2014-2015 at the floodplain) and on the pedon scale with chamber methods (campaigns at different sites in 2002, 2006, 2013, 2014, 2015). Average growing season (June-September) CH4 flux for the floodplain was 166±4 mmol m-2 (n=2) and for the river terrace 100±25 mmol m-2 (n=15). There was pronounced spatial variability of CH4 fluxes within both tundra landscapes types. On the river terrace, growing season CH4 flux was only 20-40 mmol m-2 at elevated polygon rims and polygon high centers, respectively, and up to 300 mmol m-2 at polygon low centers. On the floodplain, CH4 flux was as low as 5 mmol m-2 at sandy ridges and above 400 mmol m-2 in backswamp depressions. Mean growing season CH4 fluxes at the river terrace were positively linearly correlated (r2=0.9, n=15) to growing-degree- days (base temperature of 5°C). Our findings suggest that a warmer climate stimulates the production of CH4, which is directly reflected in increased CH4 emissions. On the other hand, warming effects on CH4 oxidation appear limited because transport processes that bypass the soil oxidation zone, i.e. plant-mediated transport and ebullition, dominate CH4 emission from wet tundra landscapes. However, since CH4 emissions strongly vary with (micro-)topographical situation within tundra landscapes, the changes of geomorphology and hydrology due to permafrost degradation will probably be the dominating driver of future CH4 emissions from arctic tundra landscapes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17937

2020063034 Lhosmot, Alexandre (Université Savoie Mont Blanc, Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Montagne, France); Ravanel, Ludovic; Preunkert, Suzanne; Magnin, Florence; Guillet, Grégoire; Rabatel, Antoine and Deline, Philip. 14 years of LiDAR monitoring and insights into ice of rockwall permafrost; the east face of the Tour Ronde (3792 m, Mont Blanc Massif) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11374, 4 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The increasing rockfall frequency in high mountain rockwalls is generally associated with global warming via the permafrost warming but long series of high resolution data on rockfall are still necessary to better appreciate the evolution of their frequencies and volumes, and to better understand their triggering factors. Here we present an inventory of rockfalls surveyed by terrestrial laser scanning (LiDAR) since 2005 in the east face of the Tour Ronde (3792 m a.s.l.) in the Géant glacial basin (Mont Blanc massif). Between 2005 and 2018, the rockwall was scanned 12 times, giving 11 comparisons of 3D models [1]. These highlighted a very intense morphodynamics with 91 destabilizations with volumes between 1 and 15,578 m3 for a total volume of 31,610 m3 (mean erosion rate: 29,8 mm.yr-1). In the first year of measurement, the Bernezat spur was affected by a collapse of more than 700 m3 [2]. Then, it was affected by rockfalls not exceeding a few tens of m3. On the other hand, in the rest of the face, there is a very strong increase in rockfall activity, especially during the hot summer 2015 at the end of which (August 27) the most voluminous collapse of the whole period occurred. The modelled surface temperature distribution at the scale of the Mont Blanc massif [3] attests to the presence of permafrost throughout the rockslope, confirmed by temperature measurements carried out at 3, 30 and 55 cm deep in the rock at the base of the Bernezat spur between October 2006 and May 2009. In addition, the main collapses left massive ice, at the level of their scar, more or less mixed with rock debris. These different elements, associated with the fact that collapses occur essentially during and following the highest summer heat, point to the role of degradation of permafrost [4]. A collapse on December 4, 2018 at the level of the small spur located at the foot of the Bernezat and whose volume is estimated at 7000 m3 reinforces this hypothesis since the detachment surface was covered - except for its margins - by massive ice. This has been sampled and its dating will perhaps confirm the age of the ice present in the cracks of the permafrost-affected rockwalls of the Mont Blanc massif. In 2017, a collapse of 44,000 m3 in the north face of the Aiguille du Midi (3842 m a.s.l.) had exposed 4060 calBP ice. In the Tour Ronde case, ice/snow cover changes and glacial debutressing could also partly explain the rockfall activity. Ravanel L. et al. (2010). Revue Française de Photogrammétrie et de Télédétection, 192 : 58-65. Rabatel A. et al. (2008). Geophysical Research Letters, 35: L10502. Magnin F. et al. (2015). Geomorphologie, 21: 145-162. Ravanel L. et al. (2017). Science of the Total Environment, 609: 132-143. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11374

2020063126 Limbrock, Jonas K. (Universtiy of Bonn, Institute of Geosciences, Bonn, Germany); Weigand, Maximilian and Kemna, Andreas. Improved thermal characterization of alpine permafrost sites by broadband SIP measurements [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20081, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Geoelectrical methods are increasingly used for non-invasive characterization and monitoring of permafrost sites, since the electrical properties of the subsoil are sensitive to the phase change of liquid to frozen water. In this context, electrical subsurface parameters act as proxies for temperature and ice content. However, it is still challenging to distinguish between air and ice in the pore space of the rock based on the resistivity method alone due to their similarly low electrical conductivity. This ambiguity in the subsurface conduction properties can be reduced by considering the spectral electrical polarization signature of ice using the Spectral Induced Polarization (SIP) method, in which the complex, frequency-dependent impedance is measured. These measurements are hypothesized to allowing for the quantification of ice content (and thus differentiation of ice and air), and for the improved thermal characterization of alpine permafrost sites. In the present study, vertical SIP sounding measurements have been made at different alpine permafrost sites in a frequency range from 100 mHz to 45 kHz. From borehole temperature measurements, we know the thermal state of these sites during our SIP soundings, i.e., an active layer thickness of about 4 m at the Schilthorn field site. In order to understand and to calibrate ice and temperature relationships, the electrical impedance was likewise measured on water-saturated soil and rock samples from these field sites in a frequency range from 10 mHz to 45 kHz during controlled freeze-thaw cycles (+20°C to -40°C) in the laboratory. For field and laboratory measurements, the resistance (impedance magnitude) shows a similar temperature dependence, with increasing resistance for decreasing temperatures. For each sample, the impedance phase spectra exhibit the well-known temperature-dependent relaxation behavior of ice at higher frequencies (1 kHz-45 kHz), with an increasing polarization magnitude for lower temperatures or larger depths of investigation, respectively. At lower frequencies (1 Hz-1 kHz), a polarization with a low frequency dependence is observed in the unfrozen state of the samples. We interpret this response as membrane polarization, considering that it decreases in magnitude with decreasing temperature (i.e., with ongoing freezing). Using the independently measured borehole temperature data, a systematic comparison of the SIP laboratory and field measurements indicates the possibility of a thermal characterization of an alpine permafrost site using SIP. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20081

2020063042 Lizotte, Martine (Université Laval, Quebec, QC, Canada). From pre-freshet to pre-freeze; a field survey of the fate of organic matter remobilized from the thawing permafrost to the coastal waters of the Mackenzie Delta region [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11944, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Thawing of permafrost in the Mackenzie Delta region of northern Canada, coupled with an increase in river discharge, prompts the release of particulate and dissolved organic matter from the largest Arctic drainage basin in North America into the Arctic Ocean. While this ongoing process is well-recognized and its rate is accelerating, the fate of the newly-mobilized organic matter as it transits from the watershed through the delta and into the marine system remains poorly understood. In the framework of the H2020 Nunataryuk project, and in partnership with ArcticNet and Sentinel North, we conducted intensive field expeditions in the Mackenzie Delta from April to September 2019. The temporal sampling scheme of this project allowed the investigation of ambient conditions in the coastal waters under a full ice cover prior to the spring freshet, during the ice break-up, in summer, as well as in fall prior to the freeze-up period. In order to capture the fluvial-marine transition zone and with specific challenges related to shallow waters and changing seasons, the field sampling was conducted using several platforms: helicopters, snowmobiles and small boats. Water column profiles of physical and optical variables were measured on site, and water and sediment samples were collected and preserved for the determination of the composition and sources of particulate and dissolved organic matter, as well as its biogeochemical cycling in the coastal environment. Beyond improving our understanding of the origin and fate of this re-mobilized organic matter, the data gathered will serve as a new basis for the ground truthing of remotely sensed images in a changing arctic environment. Finally, the tuned satellite data will be incorporated into numerical models, providing better predictions of the impacts of permafrost thaw on local biogeochemical cycling and ultimately on sea-air fluxes of carbon dioxide and global climate. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11944

2020063132 Loskutova, Marina (Arctic and Antarctic Research Institute, Saint Petersburg, Russian Federation); Makshtas, Alexander; Laurila, Tuomas and Asmi, Eija. Carbon dioxide variability at research station "ice base Cape Baranova" during 2015-2019 [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20807, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic region is one of the main areas of greenhouse gases sources due to large amount of biomass, carbon stocks in the soil and extensive wetlands. Large resources of previously inactive organic carbon may take part in atmospheric chemical reactions under melting permafrost conditions. In this case, carbon dioxide concentrations will increase in the atmosphere. Since 2015 Arctic and Antarctic Research Institute in cooperation with Finnish Meteorological Institute have been measuring the continuous concentrations of water vapor, methane, carbon dioxide and carbon monoxide at Research Station "Ice Base Cape Baranova" (79°18'N, 101°48'E, 30 m asl.) using cavity ringdown spectroscopy (CRDS) analyzer Picarro G2401. The sampling inlet is located at 10 m height. Data preprocessing consists of deleting values obtained during power failures and 2 minutes after calibration. The values for wind directions corresponding to the transfer from diesel power station (90-145°) and for wind speeds less than 3 m/s were also discarded because in this case polluted air may be distributed over the station homogeneously. After that data were adjusted taking into account the nearest calibration values by linear interpolation. The archive of carbon dioxide concentrations data averaged over each hour from October 2015 to December 2019 was used for further analysis. CO2 time series are characterized by a pronounced annual variation with concentration decreasing in summer months. The absorption by sea phytoplankton in the absence of sea ice cover causes the annual variability of carbon dioxide. Besides, the predominant presence of stable stratification of the atmospheric surface layer throughout the polar night contributes to accumulation of the gas in the surface layer in winter. The annual amplitude is 18-20 ppm approximately, which is consistent with the data of Alert and Barrow polar stations. The analysis of the dependence of registered concentration distribution on the wind direction shows that the highest values are observed during the air-mass transfer from the south-western and northern directions. If the first case can be explained by the anthropogenic impact and presence of extensive wetlands in the summer, the reason for the second one requires a more detailed analysis. Applying the HYSPLIT trajectory model for cases of elevated values of greenhouse gas concentrations did not allow us to obtain an unambiguous answer. Although elevated values were observed, as a rule, when air masses transferred from the regions of Norilsk, Yamal, the Kola Peninsula, and Lena estuary, however, there were cases of elevated concentrations during the transfer of air masses from the Arctic Ocean. This may be due to the action of any local sources, but their detection requires additional data analysis. The work had been executed in frame of CNTP Roshydromet 1.5.3.3. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20807

2020063015 Lyu, Chuangxin (Norwegian University of Science and Technology, Department of Civil and Environmental Engineering, Norway); Ingeman-Nielsen, Thomas; Amiri, Seyed Ali Ghoreishian; Eiksund, Gudmund Reidar and Grimstad, Gustav. Joint acoustic and electrical measurements for unfrozen water saturation of frozen saline soil [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10334, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The climate change has aroused great concern on the stability and durability of the infrastructure installed on permafrost, especially for frozen saline clay with a large amount of unfrozen water content at subzero temperature. The joint electrical resistivity and acoustic velocity measurements are conducted for frozen saline sand and onsoy clay with 50% clay content and 20~40 g/L salinity in order to determine the unfrozen water content. A systematic program of tests involves the saline sand with different salinity, natural onsoy clay with the variable of temperature and freezing-thawing cycles and reconstituted onsoy clay with distinctive density and salinity. The data analysis of measurement results in combination with previous joint measurements for frozen soil resolves the effect of temperature, salinity, soil type and freezing-thawing cycles on the acoustic and electrical properties. An increase of temperature, fine content and salinity results in a decrease of both acoustic velocity and electrical resistivity. Electrical resistivity is sensitive to salinity, while acoustic velocity changes substantially near thawing temperature. We also find that both natural and reconstituted clay with similar water content and salinity show quite different acoustic velocity and electrical resistivity, which indicates that ice crystal structures are distinctive between natural and reconstituted samples. Besides, P-wave velocity is much more sensitive to the fabric change or induced cracks than electrical resistance during freezing-thawing cycles. In the end, acoustic models like the weighted equation (Lee et al., 1996), Zimmerman and King's model (King et al., 1988) and BGTL (Lee, 2002) are applied to the UWS estimates based on P-wave velocity and electrical models like Archine's law are adopted based on electrical resistance. Both estimated UWS from different methods is not always consistent. The difference can be up to 20%. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10334

2020063127 Ma, Deying (German Research Centre For Geosciences, Germany); Motagh, Mahdi and Liu, Guoxiang. Permafrost degradation monitoring by InSAR at different spatial resolution in Sanjiangyuan region, China [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20173, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Sanjiangyuan, as the Chinese 'water tank', is located in Qinghai province, China. It is the fountainhead of yellow river, Yangzi river and Lancang river. Therefore, it's extraordinary valuable to the environment of China and Asia. The continuous permafrost spreads widely in this area. With the global warming process, the degradation of permafrost becomes faster and consequently changes the distribution of vegetation and hydrological cycle. In this study, we use Persistent Scatterer InSAR (PSI) technique to efficiently detect the seasonal settlement around Elin lake and Zhaling lake, which are the main parts of Sanjiangyuan region. The subsidence was analyzed by processing 56 Sentinel-1 SAR images from 2015 to 2019 using SNAP and StaMPS. The results were then inverted to derive the corresponding active layer thickness over this region. Moreover, in order to investigate the detailed influence of degradation on infrastructures, we analyzed 3m resolution TerraSAR-X images in StripMap mode from May to October 2015 to get the heterogeneous subsidence along the Gonghe-Yushu road. Results indicate mean subsidence rates exceeding 4 cm/yr along the Gonghe-Yushu road. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20173

2020063114 Magnin, Florence (CNRS, EDYTEM Laboratory, Le Bourget de Lac, France); Josnin, Jean-Yves; Ravanel, Ludovic and Deline, Philip. Modelling water-related processes in rock wall permafrost [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19575, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rock wall permafrost has been increasingly regarded since the early 2000s in reason of the growing frequency and magnitude of bedrock failures from mountain permafrost areas. One of the main current challenges to better assess its degradation and the failure mechanisms is the understanding of hydraulic processes, i.e. water infiltration and circulation in the fractures. Indeed, recent thermal and mechanical models have considered a homogeneous and ice-saturated rock medium, overlooking water-related processes which may act along fractures when water percolates. But observations of water stains alongside ice bodies in several rock fall scars point out the need to gain knowledge about such processes. Recent development in numerical codes allow to fully couple thermal and hydraulic processes, and have so far mostly been used to investigate polar permafrost terrains. In this communication, we will present a first attempt to couple thermal and hydraulic processes in a numerical model of high-alpine bedrock permafrost. This entails designing a new modelling approach accounting for heterogeneous (fractured) and non-saturated areas in the rock medium, as well as water outlets and fracture intersections to permit water circulation. We implement Richards equations in the Finite Element simulation system Feflow (DHI-WASY) to model variably saturated flow and advective-conductive heat transports combined with phase change processes. We simulate heat and mass transports in a 2D geometry (vertical cross-section) reflecting the Aiguille du Midi settings (3842 m a.s.l., Mont Blanc massif, European Alps). The model is forced with climate time series partially constructed out of measured air temperature and assumptions about previous climate period. Steady freezing occurring between 1550 and 1850 AD (Little Ice Age) points out the role of fractures in the freezing rate, as fractures favor infiltration of cold water from the surface, acting as freezing corridors. Under thawing, water movements are enabled in the unfrozen upper parts of the model geometry through a partially saturated domain, whereas the lower part remains saturated. In the thawed zones, fractures that are not completely filled by ice can accelerate water circulation and create thawing corridors. In this communication, we will present the modelling approach and the preliminary results. We will show that our numerical investigations bear strong potential to address thermal and mechanical effects of water infiltration (from snow melting and rain) and circulation in the frozen bedrock. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19575

2020063012 Maierhofer, Theresa (University of Fribourg, Fribourg, Switzerland); Katona, Timea; Hilbich, Christin; Hauck, Christian and Flores-Orozco, Adrian. Prospecting alpine permafrost with spectral induced polarization in different geomorphological landforms [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10131, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost regions are highly sensitive to climate changes, which has significant implications for the hydrological regimes and the mechanical state of the subsurface leading to natural hazards such as rock slope failures. Therefore, a better understanding of the future evolution and dynamics of mountain permafrost is highly relevant and monitoring of the thermal state of permafrost has become an essential task in the European Alps. Geophysical methods have emerged as well-suited to support borehole data and investigate the spatial distribution and temporal changes of temperature and the degradation of permafrost. In particular, electrical resistivity tomography (ERT) has developed into a routine imaging tool for the quantification of ice-rich permafrost, commonly associated with a significant increase in the electrical resistivity. However, in many cases, the interpretation of the subsurface electrical resistivity is ambiguous and additional information would improve the quantification of the ice content within the subsurface. Theoretical and laboratory studies have suggested that ice exhibits a characteristic induced electrical polarization response. Our results from an extensive field programme including many morphologically different mountain permafrost sites now indicate that this IP response may indeed be detected in the field suggesting the potential of the Induced Polarization (IP) method to overcome such ambiguities. We present here Spectral IP (SIP) mapping results conducted over a broad range of frequencies (0.1-225 Hz) at four representative permafrost sites of the Swiss-, Italian- and Austrian Alps. The mapping results have been used to install long-term permafrost monitoring arrays for a better understanding of subsurface variations associated to climate change. All SIP study sites are located at elevations around 2600 - 3000 m and include comprehensive geophysical and temperature data for validation. We focus on the spatial characterization of each site to address different research questions: to (i) reproduce and improve the mapping of the spatial permafrost extent inferred from previous investigations in the Lapires talus slope,Western Swiss Alps, to (ii) improve the geophysical characterization of the Sonnblick monitoring site located in the Austrian Central Alps, to (iii) determine the transition between permafrost and non-permafrost at the Schilthorn site, Bernese Alps, Switzerland, and to (iv) find the best-suited location for a SIP monitoring profile and conduct year-round measurements at the Cime Bianche site, Western Italian Alps. Our various field applications demonstrate the potential of the IP method for characterizing and monitoring permafrost systems in high-mountain environments. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10131

2020063105 Martens, Jannik (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Wild, Birgit; Tesi, Tommaso; Muschitiello, Francesco; O'Regan, Matt; Jakobsson, Martin; Semiletov, Igor; Dudarev, Oleg V. and Gustafsson, Orjan. Sediment archives from the Arctic Ocean provide evidence for massive remobilization of permafrost carbon in Siberia during the last glacial termination [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18643, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Environmental archives and carbon cycle models suggest that climate warming during the last deglaciation (the transition from the last glacial to the Holocene) caused large-scale thaw of Arctic permafrost, followed by the release of previously freeze-locked carbon. In addition to changing oceanic circulation and outgassing of CO2 trapped in the deep glacial ocean, organic carbon (OC) release from thawing permafrost might have contributed to the rise in atmospheric CO2 by 80 ppmv or ~200 Pg C between 17.5 and 11.7 kyr before present (BP). The few Arctic sediment cores to date, however, lack either temporal resolution or reflect only regional catchments, leaving most of the permafrost OC remobilization of the deglaciation unconstrained. Our study explores the flux and fate of OC released from permafrost to the Siberian Arctic Seas during the last deglaciation. The Arctic Ocean is the main recipient of permafrost material delivered by river transport or collapse of coastal permafrost, providing an archive for current and past release of OC from thawing permafrost. We studied isotopes (D14C-OC, d13C-OC) and terrestrial biomarkers (CuO-derived lignin phenols, n-alkanes, n-alkanoic acids) in a number of sediment cores from the Siberian Shelf and Central Arctic Ocean to reconstruct source and fate of OC previously locked in permafrost. The composite record of three cores from the Laptev, East Siberian and Chukchi Seas suggest a combination of OC released by deepening of permafrost active layer in inland Siberia and by thermal collapse of coastal permafrost during the deglaciation. Coastal erosion of permafrost during the deglaciation suggests that sea-level rise and flooding of the Siberian shelf remobilized OC from permafrost deposits that covered the dry shelf areas during the last glacial. A sediment core from the Central Arctic Ocean demonstrates that this occurred in two major pulses; i) during the Bolling-Allerod (14.7-12.9 kyr BP), but most strongly ii) during the early Holocene (11-7.6 kyr BP). In the early Holocene, flooding of 80% of the Siberian shelf amplified permafrost OC release to the Arctic Ocean, with peak fluxes 10-9 kyr BP one order of magnitude higher than at other times in the Holocene. It is likely that the remobilization of permafrost OC by flooding of the Siberian shelf released climate-significant amounts of dormant OC into active biogeochemical cycling and the atmosphere. Previous studies estimated that a pool of 300-600 Pg OC was held in permafrost covering Arctic Ocean shelves during the last glacial maximum; one can only speculate about its whereabouts after the deglaciation. Present and future reconstructions of historical remobilization of permafrost OC will help to understand how important permafrost thawing is to large-scale carbon cycling. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18643

2020063061 Martin, Victoria (University of Vienna, Department of Microbiology and Ecosystem Science, Vienna, Austria); Wagner, Julia; Speetjens, Niek; Lodi, Rachele; Horak, Julia; Urbina-Malo, Carolina; Mohrlok, Moritz; Rottensteiner, Cornelia; A'Campo, Willeke; Durstewitz, Luca; Tanski, George; Fritz, Michael; Lantuit, Hugues; Hugelius, Gustaf and Richter, Andreas. How do microorganisms from permafrost soils respond to short-term warming? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13452, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic ecosystems outpace the global rate of temperature increases and are exceptionally susceptible to global warming. Concerns are raising that CO2 and CH4 released from thawing permafrost upon warming may induce a positive feedback to climate change. This is based on the assumption, that microbial activity increases with warming and does not acclimate over time. However, we lack a mechanistic understanding of carbon and nutrient fluxes including their spatial control in the very heterogeneous Arctic landscape. The objective of this study therefore was to elucidate the microbial controls over soil organic matter decomposition in different horizons of the active layer and upper permafrost. We investigated different landscape units (high-centre polygons, low-centre polygons and flat polygon tundra) in two small catchments that differ in glacial history, at the Yukon coast, Northwestern Canada. In total, 81 soil samples were subjected to short-term (eight weeks) incubation experiments at controlled temperature (4 °C and 14 °C) and moisture conditions. Heterotrophic respiration was assessed weekly, whereas physiological parameters of soil microbes and their temperature response (Q10) were determined at the end of the incubation period. Microbial growth was estimated by measuring the incorporation of 18O from labelled water into DNA and used to calculate microbial carbon use efficiencies (CUE). Microbial biomass was determined via chloroform fumigation extraction. Potential activities of extracellular enzymes involved in C, N, P and S cycling were measured using microplate fluorimetric assays. Cumulative heterotrophic respiration of investigated soil layers followed the pattern organic layers > upper frozen permafrost > cryoturbated material > mineral layers in both catchments. Microbial respiration responded strongly in all soils to warming in all soils, but the observed response was highest for organic layers and cryoturbated material at the beginning and end of the experiment. Average Q10 values at the beginning of the experiment varied between 1.7 to 4.3 with differences between horizons but converged towards Q10 values between 2.0min to 2.9max after eight weeks of incubation. Even though microbial biomass C did not change with warming, microbial mass specific growth was enhanced in organic, cryoturbated and permafrost soils. Overall, warming resulted in a 65% reduced CUE in organic horizons. Our results show no indication for physiological acclimatization of permafrost soil microbes when subjected to 8-weeks of experimental warming. Given that the duration of the season in which most horizons are unfrozen is rarely longer than 2 months, our results do not support an acclimation of microbial activity under natural conditions. Instead, our data supports the current view of a high potential for prolonged carbon losses from tundra soils with warming by enhanced microbial activity. This work is part of the EU H2020 project "Nunataryuk". [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13452

2020063124 Martyn, Melanie (Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands); Dean, Joshua; Dolman, Han and Vonk, Jorien. The role of inland freshwaters in summer CO2, CH4 and N2O emissions from northeast Siberian Arctic tundra [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20028, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Inland waters can be significant sources of greenhouse gases (GHGs; CO2, CH4 and N2O) to the atmosphere, yet they are often excluded from terrestrial GHG balances. Vast stocks of carbon stored in Arctic tundra permafrost soils are vulnerable to mobilisation due to permafrost thawing accelerated by the amplified effects of climate warming at high latitudes. The carbon that is released becomes available to (partial) degradation producing GHGs which inland waters emit to the atmosphere, thus forming a positive feedback to climate warming. Rising temperatures, longer summers and increased precipitation in the Arctic tundra are expected to increase permafrost thaw and degradation rates, therefore the contribution of inland waters to the tundra terrestrial GHG budgets needs to be better understood to assess the strength and timing of the feedback effect in the future. Field data from lakes, ponds and streams throughout the summer season of three years and from floodplain water present in one of the years was collected. This data was used to calculate CO2 equivalent diffusive fluxes from inland freshwaters, and combined with eddy covariance flux tower measurements and with satellite remote sensing to calculate total GHG emissions of the study area. The results indicate that ponds are the largest contributors to upscaled inland water GHG emissions (around 50%) followed by streams and finally lakes. Streams had the highest emission rates followed by lakes and ponds the lowest, however due to the large surface area coverage of ponds (15% of the study area) they become the largest contributor to the upscaled freshwater GHG emissions. Upscaling of CH4 and CO2 fluxes shows that while the study region remains a GHG sink, inclusion of freshwater emissions reduces its sink capacity by 28% during our reference month July. Assuming that 10% of the study area is flooded in this month, it reduces the terrestrial GHG sink estimate to 45% instead of 28%, partially due to N2O oversaturation in the flood water in relation to the atmosphere whereas N2O concentrations in lakes, streams and ponds are close to zero. Overall the results show that if the Siberian Arctic tundra becomes wetter or more frequently flooded due to climate warming it will significantly affect the total terrestrial GHG balance. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20028

2020063101 Mathys, Tamara (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Hilbich, Christin; Koenig, Cassandra E. M.; Arenson, Lukas and Hauck, Christian. Upscaling of geophysical measurements; a methodology for the estimation of the total ground ice content at two study sites in the dry Andes of Chile and Argentina [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18397, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With climate change and the associated continuing recession of glaciers, water security, especially in regions depending on the water supply from glaciers, is threatened. In this context, the understanding of permafrost distribution and its degradation is of increasing importance as it is currently debated whether ground ice can be considered as a significant water reservoir and as an alternative resource of fresh water that could potentially moderate water scarcity during dry seasons in the future. Thus, there is a pressing need to better understand how much water is stored as ground ice in areas with extensive permafrost occurrence and how meltwater from permafrost degradation may contribute to the hydrological cycle in the region. Although permafrost and permafrost landforms in the Central Andes are considered to be abundant and well developed, the data is scarce and understanding of the Andean cryosphere lacking, especially in areas devoid of glaciers and rock glaciers. In the absence of boreholes and test pits, geophysical investigations are a feasible and cost-effective technique to detect ground ice occurrences within a variety of landforms and substrates. In addition to the geophysical surveys themselves, upscaling techniques are needed to estimate ground ice content, and thereby future water resources, on larger spatial scales. To contribute to reducing the data scarcity regarding ground ice content in the Central Andes, this study focuses on the permafrost distribution and the ground ice content (and its water equivalent) of two catchments in the semi-arid Andes of Chile and Argentina. Geophysical methods (Electrical Resistivity Tomography, ERT and Refraction Seismic Tomography, RST) were used to detect and quantify ground ice in the study regions in the framework of environmental impact assessments in mining areas. Where available, ERT and RST measurements were quantitatively combined to estimate the volumetric ground ice content using the Four Phase Model (Hauck et al., 2011). Furthermore, we developed one of the first methodologies for the upscaling of these geophysical-based ground ice quantifications to an entire catchment in order to estimate the total ground ice volume in the study areas. In this contribution we will present the geophysical data, the upscaling methodology used to estimate total ground ice content (and water equivalent) of permafrost areas, and some first estimates of total ground ice content in rock glacier and rock glacier free areas and compare them to conventional estimates using remotely sensed data. Hauck, C., Bottcher, M., and Maurer, H. (2011). A new model for estimating subsurface ice content based on combined electrical and seismic datasets, The Cryosphere, 5: 453-468. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18397

2020063117 Matsubara, Felipe (Stockholm Univeristy, Department of Environmental Science, Stockholm, Sweden); Wild, Birgit; Martens, Jannik; Wennström, Rickard; Tesi, Tommaso; Dudarev, Oleg; Shakhova, Natalia; Semiletov, Igor and Gustafsson, Orjan. Degradation of terrigenous organic matter on the east Siberian Arctic shelf assessed by lipid and lignin oxidation products [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19668, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Warming-induced permafrost thawing is expected to intensify the remobilization of terrigenous organic matter (terrOM) to the East Siberian Arctic Shelf (ESAS) via increasing river discharge and coastal erosion. Earlier studies have focused on source apportionment and transport of terrOM, with less emphasis on its degradation state during cross-shelf transport. Since degradation of terrOM is the link between permafrost thawing and release of GHGs such as CO2, this study focuses on the degradation characteristics. Hence, the main objective of this study is to assess the patterns of terrOM degradation across the East Siberian Arctic Shelf using molecular proxies that are specific to terrOM. Lignin phenols and high molecular weight (HMW) n-alkanes and n-alkanoic acids are only produced by terrestrial plants which make them suitable biomarkers to assess degradation of terrestrial material throughout the ESAS. The lignin-based proxies acid to aldehyde ratios of vanillyl (Vd/Vl) and syringyl (Sd/Sl) structural units, as well as the ratio of 3,5-dihydroxybenzoic acid over vanillin (3,5-Bd/V) are expected to increase during degradation under oxic conditions. Fresh terrestrial plant material is predominated by long odd-numbered (>C25) and even-numbered (>C24) carbon chain length of n-alkanes and n-alkanoic acids, respectively. This dominance is described in the Carbon Preference Index (CPI). When degradation takes place, CPI values decrease accordingly, describing how much of the original material was preserved. Ratios of HMW n-alkanoic acids to HMW n-alkanes are also expected to decrease during microbial degradation owing to preferential loss of functional groups. The data show increasing Vd/Vl, Sd/Sl and 3,5-Bd/V ratios, and decreasing HMW n-alkanes CPI values toward the outer shelf, consistent with continuous degradation of terrOM across the ESAS. While Vd/Vl and HMW n-alkane CPI did not show strong differences between east and west, Sd/Sl ratios were highest in the outer western ESAS, and 3,5-Bd/V ratios were highest in the outer east. These differences may reflect different terrOM pools along the ESAS due to differences in vegetation zones releasing the input material through river discharge and coastal erosion. In contrast, HMW n-alkanoic acid to HMW n-alkane ratio and HMW n-alkanoic acid CPI showed inconsistent patterns across the ESAS; reasons for it are currently being investigated. These results will also be complemented by additional biomarkers to better understand the degradation of terrOM during cross-shelf transport. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19668

2020063038 Meyer, Gesa (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Humphreys, Elyn; Melton, Joe; Lafleur, Peter; Marsh, Philip; Detto, Matteo; Helbig, Manuel; Boike, Julia; Voigt, Carolina and Sonnentag, Oliver. The role of soil characteristics on measured and modelled carbon dioxide and energy fluxes for Arctic dwarf shrub tundra sites [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11913, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Four years of growing season eddy covariance measurements of net carbon dioxide (CO2) and energy fluxes were used to examine the similarities/differences in surface-atmosphere interactions at two dwarf shrub tundra sites within Canada's Southern Arctic ecozone, separated by approximately 1000 km. Both sites, Trail Valley Creek (TVC) and Daring Lake (DL1), are characterised by similar climate (with some differences in radiation due to latitudinal differences), vegetation composition and structure, and are underlain by continuous permafrost, but differ in their soil characteristics. Total atmospheric heating (the sum of latent and sensible heat fluxes) was similar at the two sites. However, at DL1, where the surface organic layer was thinner and mineral soil coarser in texture, latent heat fluxes were greater, sensible heat fluxes were lower, soils were warmer and the active layer thicker. At TVC, cooler soils likely kept ecosystem respiration relatively low despite similar total growing season productivity. As a result, the 4-year mean net growing season ecosystem CO2 uptake (May 1 - September 30) was almost twice as large at TVC (64 ± 19 g C m-2) compared to DL1 (33 ± 11 g C m-2). These results highlight that soil and thaw characteristics are important to understand variability in surface-atmosphere interactions among tundra ecosystems. As recent studies have shown, winter fluxes play an important role in the annual CO2 balance of Arctic tundra ecosystems. However, flux measurements were not available at TVC and DL1 during the cold season. Thus, the process-based ecosystem model CLASSIC (the Canadian Land Surface Scheme including biogeochemical Cycles, formerly CLASS-CTEM) was used to simulate year-round fluxes. In order to represent the Arctic shrub tundra better, shrub and sedge plant functional types were included in CLASSIC and results were evaluated using measurements at DL1. Preliminary results indicate that cold season CO2 losses are substantial and may exceed the growing season CO2 uptake at DL1 during 2010-2017. The joint use of observations and models is valuable in order to better constrain the Arctic CO2 balance. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11913

2020063032 Moorman, Brian (University of Calgary, Geography Department, Calgary, AB, Canada). Submarine preservation of massive tabular ground ice by coastal retrogressive thaw slumps [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11343, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Around the Arctic Ocean there are many stretches of coastline composed of ice-rich sediments. With the dramatic climatic, oceanic and terrestrial changes that are currently occurring, there is considerable concern over the stability of these coasts and how they are being altered. With the complexity that permafrost conditions add to the coastal setting, modelling erosion involves a more detailed understanding of the physical and thermal conditions as well as the sedimentological and wave action processes. This research examines the role that the shallow water energy balance plays in preserving sub-bottom massive ice as the coastline retreats and the implications it has for secondary subsea disturbance once the water depth increases. The study area was Peninsula Point which is approximately 10 km west of Tuktoyaktuk, NWT, Canada. The massive ice and retrogressive thaw slumps at this location are some of the more dramatic examples of the impact of ice-rich permafrost on coastal processes in the Arctic. By mapping the area with satellite and aerial imagery and conducting repeat ground penetrating radar surveys (GPR) over a 30 year period, the long-term character of coastal retreat above, and below, the water line is revealed. In winter, the GPR was pulled behind a snowmobile along transects on land, across the shoreline and out onto the near shore area of the Beaufort Sea. This provided the stratigraphic continuity between the terrestrial and sub-sea settings. The GPR revealed the massive ice and sedimentary architecture, from which vertical and lateral relationships to the coastline were determined. The roles of erosion, re-sedimentation and shallow-water thermodynamics in the degradation and preservation of massive ground ice were revealed. Using this new information, modeling of the coastal retreat and sediment contributions to the ocean demonstrated a much more complex system than previously assumed. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11343

2020063053 Morse, Peter (Natural Resources Canada, Geological Survey of Canada, Ottawa, ON, Canada); Wolfe, Stephen and Kokelj, Steve. A landsystems approach to understanding the evolution of ice-cored topography and distribution of retrogressive thaw slumps, western Canadian Arctic [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12571, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The landscape of the Tuktoyaktuk Coastlands, western Canadian Arctic is dominated by glacial and geocryological processes that have modified, imprinted and sculpted the surface, depositing surficial materials upon underlying bedrock. Climate warming continues in this region at a rate that is twice the global average, and retrogressive thaw slump (RTS) activity is increasing. Recently, RTS distribution was associated with glacial limits reached by the Laurentide Ice Sheet and corresponding morainal deposits, but RTS are common in other local terrain units. In this glacial-marginal region, permafrost existed pre-glacially, and non-glacial geomorphic processes occurred throughout the Late Quaternary. Superimposed on these conditions are the effects of thermokarst during the Holocene climatic optimum, followed by a period of cooling. Collectively, these processes and associated forms and deposits have contributed variously to preservation, development, or degradation of permafrost and ground ice. The multifaceted Late Quaternary history in this region has impeded understanding of the distributions of ice-cored topography and RTS. For example, rather than glaciogenic ice, the long reigning regional model for ice-cored topography is according to post-glacial development of intrasedimental segregation-intrusion ice. Toward better understanding the evolution of the whole landscape and the distribution of climate-sensitive terrain, we use a landsystems approach as a means to understand how the ice-cored topography developed where RTS form, through analysing the cryostratigraphy. To this end, we identify 6 RTS representing a suite of ice-cored topographic settings, including: (i) preserved basal glacial ice facies within clayey diamict that has been thrusted and folded by glacial push representing morainal deposits of the Sitidgi Stade; (ii) ice contact outwash sediments associated with the Sitidgi Stade, overlying a thermo-erosional contact with underlying basal glacial icy diamict of the Toker Point Stade; (iii) deformed basal glacial ice, eroded down by meltwater-deposited outwash sands some time between the Toker Point and Sitidgi Stades (could be ca. 12.9 kyr BP); (iv) massive, undeformed segregation-intrusion basal ice, likely formed subglacially by freezing of intrasedimental water in pre-existing Pleistocene sands into the base of the glacier, overlain by glacial diamicton; (v) deformed basal ice facies of intermediate Toker Point - Sitidgi Stades, with an upper layer that may be supra-glacial melt-out till into which segregated ice formed; and (vi) segregation ice that formed as permafrost aggraded into glaciolacustrine clays deposited in proglacial or glacially dammed basins, that was subsequently eroded down by glaciofluvial outwash (Sitidgi Stade). To summarize, the distribution of RTS reflects primarily the distribution of icy basal glacial diamict preserved in moraines, but also basal ice and icy basal diamict that are preserved beneath glaciofluvial deposits, segregation ice in glaciolacustrine deposits, and massive segregation-intrusion ice in Pleistocene sands beneath a till plain. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12571

2020063147 Moseley, Gina (Univeristy of Innsbruck, Institute of Geology, Innsbruck, Austria); Edwards, R. Lawrence; Spötl, Christoph and Cheng, Hai. Speleothem record of enhanced hydroclimate during MIS15a in northeast Greenland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-22391, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic region is predicted to be one of the most sensitive areas of the world to future anthropogenically-forced climate change, the consequences of which will affect vast numbers of people worldwide, for instance through changes to mid-latitude weather systems and rising eustatic sea levels. Recent changes in temperature and precipitation, and those projected for the future, indicate that some of the greatest changes will occur in Northeast Greenland. Essential knowledge on the climate history of this region, which can be used to validate models and understand forcing mechanisms and teleconnections, is however absent. Here, we present a speleothem palaeoclimate record for Northeast Greenland (80°N) that formed during Marine Isotopes Stage 15a between 588 ka to 537 ka. The record indicates that at that time, Northeast Greenland was warmer and wetter than at present associated with a reduction in Arctic sea ice, thawing of permafrost in eastern Siberia (55°N and 60°N), and elevated warm conditions at Lake El'gygytgyn (67.5°N), Russia. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-22391

2020063133 Mudryk, Lawrence (Environment and Climate Change Canada, Canada); Krinner, Gerhard; Derksen, Chris; Santolaria-Otin, Maria; Menegoz, Martin; Brutel-Vuilmet, Claire; Vuyovich, Carrie; Kumar, Sujay and Kim, Rhae Sung. The importance of modelled processes in the evolution of snow cover versus snow mass [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20859, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Conventional wisdom holds that confidence in future projections of snow cover extent and snow mass requires an understanding of the expected changes in future snow characteristics as a function of modelled snow processes. We will highlight contrasting results which suggest differing importance in the role of sub-grid scale processes on simulations of seasonal snow. The first study is an evaluation of simulated snow cover extent projections from models participating in the 6th phase of the World Climate Research Programme Coupled Model Inter-comparison Project (CMIP-6). We demonstrate a single linear relationship between projected spring snow extent and global surface air temperature (GSAT) changes, which is valid across all future climate scenarios. This finding suggests that Northern Hemisphere spring snow extent will decrease by about 8% relative to the 1995-2014 level per °C of GSAT increase. The sensitivity of snow to temperature forcing largely explains the absence of any climate change pathway dependency, similar to other fast response components of the cryosphere such as sea ice and near surface permafrost. The second study makes use of an ensemble of land surface models, downscaled to 5 km resolution across North America over the 2009-2017 period. In this case, uncertainty in total North American snow mass is dominated by differences among land surface model configurations. While the largest absolute spread in snow mass is found in mountainous regions, heavily vegetated boreal regions have the largest fractional spread compared to climatological values. In particular, differences in rain-snow partitioning and sublimation rates control the largest portions of the total uncertainty. These results suggest that projections of future snow mass depend specifically on how such processes are modelled and parameterized. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20859

2020063109 Müller, Svenja (University of Innsbruck, Institute of Geography, Innsbruck, Austria); Ramskogler, Katharina; Knoflach, Bettina; Stötter, Johann; Erschbamer, Brigitta; Illmer, Paul and Geitner, Clemens. Development of soil in heterogeneous landscapes of a high alpine catchment in the central European Alps [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18826, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In high mountain environments with harsh weather conditions, soil development and its limitations strongly depend on topography and morphodynamics, both leading to heterogeneous landscape patterns of different geological substrate, vegetation, (micro)relief, and (micro)climate. In addition, as glaciers currently are retreating disproportionately strong, a large area is exposed to initial soil development, enabling to study time related issues of soil formation. These mosaic-like patterns are particularly intensified within the high-alpine and nival zone, due to the dominating influence of cryospheric elements, such as ice (e.g. retreating glaciers), snow (e.g. snowbeds; shallow self-deepening sinks with snow accumulation at altitudes above 2500 m a.s.l.), and frost (e.g. causing solifluction, controlling physical weathering, changing permafrost dynamics, increasing the probability mass movements and sediment transport). The high-alpine environment with its site diversity therefore represents a perfect study area to analyze soil-vegetation-interactions at various microsites within a single catchment. To study the influence of time, the glacier foreland of Zufall- and Furkeleferner (Martelltal, South Tyrol) was found to be excellent for an interdisciplinary chronosequence study. Large amounts of historical maps, aerial orthophotos, and remote sensing data are available, enabling reconstructed glacier retreat with a high spatial and temporal accuracy. Study sites of different soil age were chosen for the analysis of various soil and vegetation parameters. The influence of temperature and soil water availability were determined by installing temperature and soil matric potential data loggers. Furthermore, to study soil development as a function of geological substrate, microrelief, altitude, slope, and microclimate, an additional transect along an altitudinal gradient (Martelltal, South Tyrol, within the maximum extent of Egesen) was sampled and analyzed regarding central soil properties, vegetation, and microclimate. Directly bordering to those sites, heterogeneous and morphodynamically active microsites were investigated. These special sites were characterized by different morphological features, in particularly: soil sinks of different genesis, hilltops, and scree-dominated sites with initial soil development after primary plant succession. As expected, we found clear trends of soil development with changing altitude and/or time. However, the small-scaled special sites differed distinctly from the reference sites regarding basic soil properties such as soil pH or soil organic matter content, and also remarkably in plant-available NH4-N, microbial activity, and microbial biomass. This was especially true where the water regime was strongly affected by the microrelief. The observed distinct changes in soil properties within small scales of sometimes only several meters help to better understand and predict soil formation and diversity as well as soil-plant-interactions in high alpine environments of the European Alps. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18826

2020063064 Nguyen, Van Liem (Stockholm Univesity, Department of Environmental Science, Stockholm, Sweden); Wild, Birgit; Gustafsson, Orjan; Semiletov, Igor; Dudarev, Oleg and Jonsson, Sofi. Mercury and methylmercury along a transect from the Lena River estuary across the Laptev Sea shelf [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13727, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Widespread accelerated permafrost thawing is predicted for this century and beyond. This threatens to remobilize the large amounts of Mercury (Hg) currently "locked" in Arctic permafrost soils to the Arctic Ocean and thus potentially lead to severe consequences for human and wildlife health. Future risks of Arctic Hg in a warmer climate are, however, poorly understood. One crucial knowledge gap to fill is the fate of Hg once it enters the marine environment on the continental shelves. Arctic rivers are already today suggested to be the main source of Hg into the Arctic Ocean, with dissolved and particulate organic matter (DOM and POM, respectively) identified as important vectors for the land to sea transport. In this study, we have investigated total Hg (HgT) and monomethylmercury (MeHg) concentrations in surface sediments from the East Siberian Arctic Shelf (ESAS) along a transect from the Lena river delta to the Laptev Sea continental slope. The ESAS is the world's largest continental shelf and receives large amounts of organic carbon by the great Arctic Russian rivers (e.g., Lena, Indigirka and Kolyma), remobilized from continuous and discontinuous permafrost regions in the river catchments, and from coastal erosion. Data on HgT and MeHg levels in ESAS sediments is however limited. Here, we observed concentrations of Hg ranging from 30 to 96 ng Hg g-1 d.w. of HgT, and 0.03 to 9.5 ng Hg g-1 d.w. of MeHg. Similar concentrations of HgT were observed close to the river delta (54 ± 19 ng Hg g-1 d.w.), where >95% of the organic matter is of terrestrial origin, and the other section of the transect (42 ± 7 ng Hg g-1 d.w.) where the terrestrial organic matter is diluted with carbon from marine sources. In contrast, we observed higher concentrations of MeHg close to the river delta (0.72 ± 0.71 ng Hg g-1 d.w. as MeHg) than further out on the continental shelf (0.031 ± 0.71 ng Hg g-1 d.w. as MeHg). We also observed a positive correlation between the MeHg:Hg ratio and previously characterized molecular markers of terrestrial organic matter (Bröder et al. Biogeosciences (2016) & Nature Com. (2018)). We thus suggest riverine inputs, rather than in situ MeHg formation, to explain observed MeHg trends. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13727

2020063057 Nickus, Ulrike (University of Innsbruck, Department of Atmospheric and Cryospheric Sciences, Innsbruck, Austria); Thies, Hansjoerg; Krainer, Karl and Tessadri, Richard. Rock glacier impact on high-alpine freshwater chemistry [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12707, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Borehole soundings have revealed a warming of mountain permafrost of up to 1°C during recent decades. There is evidence that the increase in air temperature has favored the solute release from active rock glaciers, and pronounced changes in water quality of headwaters in the Alps have been described. Here, we report on solute concentrations of selected streams and springs in the vicinity of an active rock glacier in the Central European Alps (Lazaun, Italy). Stream water sampling started in 2007, and samples were analysed for major ions and heavy metals. We compare surface freshwaters of different origin and chemical characteristics, i.e. outflows of active and fossil rock glaciers, a spring emerging from a moraine and an ice glacier fed stream. Substance concentrations were highest in springs impacted by active rock glaciers, and dissolved ions increased up to a factor of 3 through the summer season. This pattern reflects a seasonally varying contribution to runoff by the melting winter snow pack, summer precipitation, baseflow and ice melt. Intense geochemical bedrock weathering of freshly exposed mineral surfaces, which are due to the downhill movement of the active rock glacier, is considered as a major reason for the high ion and metal concentrations in late summer runoff. In addition, solutes contained in the ice matrix of the rock glacier are released due to enhanced melting of rock glacier ice. On the contrary, minimum substance concentrations without any seasonal variability were found in the moraine spring. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12707

2020063019 Nielsen, David Marcolino (Universität Hamburg, Institute of Oceanography, Hamburg, Germany); Baehr, Johanna; Brovkin, Victor and Dobrynin, Mikhail. Representing Arctic coastal erosion in the Max Planck Institute Earth System Model (MPI-ESM) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10477, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic has warmed twice as fast as the globe and sea-ice extent has decreased, causing permafrost to thaw and the duration of the open-water period to extend. This combined effect increases the vulnerability of the Arctic coast to erosion, which in turn releases substantial amounts of carbon to both the ocean and the atmosphere, potentially contributing to further warming due to a positive climate-carbon cycle feedback. Therefore, Arctic coastal erosion is an important process of the global carbon cycle. Comprehensive modelling studies exploring Arctic coastal erosion within the Earth system are still in their infancy. Here, we describe the development of a semi-empirical Arctic coastal erosion model and its coupling with the Max Planck Institute Earth System Model (MPI-ESM). We also present preliminary results for historical and future climate projections of coastal erosion rates in the Arctic. The coupling consists on the exchange of a combination of driving forcings from the atmosphere and the ocean, such as surface air temperature, winds and sea-ice concentration, which result in annual coastal erosion rates. In a further step, organic matter from the eroded permafrost is provided to the ocean biogeochemistry model and, consequently, to the global carbon cycle including atmospheric CO2. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10477

2020063027 Noetzli, Jeannette (WSL Institute for Snow and Avalanche Research, Davos Dorf, Switzerland) and Pellet, Cécile. 20 years of mountain permafrost monitoring in the Swiss Alps; key results and major challenges [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10903, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost is a widespread thermal subsurface phenomenon in polar and high mountain regions and was defined as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS). The Swiss Permafrost Monitoring Network was started in the year 2000 as an unconsolidated network of sites from research projects and as the first national long-term observation network for permafrost it is an early component of the Global Terrestrial Network for Permafrost (GTN-P). After 20 years of operation, development and evaluation, PERMOS holds the largest and most diverse collection of mountain permafrost data worldwide and has a role model regarding its structure and organization. PERMOS aims at the systematic long-term documentation of the state and changes of mountain permafrost in the Swiss Alps. The scientific monitoring strategy is now based on three observation elements: ground-surface and subsurface temperatures, changes in subsurface ice content, and permafrost creep velocities. These three elements complement each other in a landform-based approach to capture the influence of the topography as well as the surface and subsurface conditions of different landforms on the ground thermal regime. These influences are considered to be more relevant than regional climatic conditions in the small country. Over the past 20 years, all observation elements indicate a clear warming trend of mountain permafrost in the Swiss Alps. Borehole temperatures generally increase at 10 and 20 m depth. This warming trend was intensified after 2009 and temporarily interrupted following winters with a thin and late snow cover, particularly winter 2016. Further, the trend is more pronounced at cold permafrost sites like rock glacier Murtèl-Corvatsch, where an increase of +0.5°C has been observed at 20 m over the past 30 years. For permafrost temperatures close to 0 °C, climate warming does not result in significant temperature increase but is masked by phase changes and latent heat effects. These result in significant changes in ice content, which can be registered by electrical resistivity tomography (ERT). Further, the warming trend of mountain permafrost in the Swiss Alps is corroborated by increasing creep rates of rock glaciers, which follow an exponential relationship with ground temperatures. In this contribution, we present and discuss the key results from two decades of mountain permafrost monitoring within the PERMOS network. In addition to the measurement data, we identified considerable challenges for long-term monitoring network of mountain permafrost based on experience collected over two decades. The acquisition of reliable data at a limited number of stations in extreme environments with difficult access requires robust strategies, standards and traceability for the entire data acquisition chain: installation > measurement > raw data > processing > archiving and, finally, reporting. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10903

2020063142 Olid, Carolina (Umea University, Department of Ecology and Environmental Science, Umea, Sweden); Klaminder, Jonatan; Monteux, Sylvain; Johansson, Margareta and Dorrepaal, Ellen. Decade of permafrost thaw in a subarctic palsa mire alters carbon fluxes without affecting net carbon balance [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21805, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Snow depth increases observed in some arctic regions and its insulations effects have led to a winter-warming of permafrost-containing peatlands. Permafrost thaw and the temperature-dependent decomposition of previously frozen carbon (C) is currently considered as one of the most important feedbacks between the arctic and the global climate system. However, the magnitude of this feedback remains uncertain because winter effects are rarely integrated and predicted from mechanisms active in both surface (young) and thawing deep (old) peat layers. Laboratory incubation studies of permafrost soils, in situ carbon flux measurements in ecosystem-scale permafrost thaw experiments, or measurements made across naturally degrading permafrost gradients have been used to improve our knowledge about the net effects of winter-warming in permafrost C storage. The results from these studies, however, are biased by imprecision in long-term (decadal to millennial) effects due to the short time scale of the experiments. Gradient studies may show longer-term responses but suffer from uncertainties because measurements are usually taken during the summer, thus ignoring the long cold season. The need for robust estimates of the long-term effect of permafrost thaw on the net C balance, which integrates year-round C fluxes sets the basis of this study. Here, we quantified the effects of long-term in situ permafrost thaw in the net C balance of a permafrost-containing peatland subjected to a 10-years snow manipulation experiment. In short, we used a peat age modelling approach to quantify the effect of winter-warming on net ecosystem production as well as on the underlying changes in surface C inputs and losses along the whole peat continuum. Contrary to our hypothesis, winter-warming did not affect the net ecosystem production regardless of the increased old C losses. This minimum overall effect is due to the strong reduction on the young C losses from the upper active layer associated to the new water saturated conditions and the decline in bryophytes. Our findings highlight the need to incorporate long-term year-round responses in C fluxes when estimating the net effect of winter-warming on permafrost C storage. We also demonstrate that thaw-induced changes in moisture conditions and plant communities are key factors to predicting future climate change feedbacks between the arctic soil C pool and the global climate system. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21805

2020063123 O'Neill, H. Brendan (Geological Survey of Canada, Ottawa, ON, Canada) and Zhang, Yu. Simulation and validation of long-term ground surface subsidence in continuous permafrost, western Arctic Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20012, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Ground surface subsidence caused by the melt of excess ice is a key geomorphic process in permafrost regions. Subsidence can damage infrastructure, alter ecology and hydrology, and influence carbon cycling. The Geological Survey of Canada maintains a network of thaw tubes in northwestern Canada, which records annual thaw penetration, active-layer thickness, and ground surface elevation changes at numerous sites. Measurements from the early 1990s from 17 sites in the Mackenzie Delta area have highlighted persistent increases in thaw penetration in response to rising air temperatures. These increases in thaw penetration have been accompanied by significant ground surface subsidence (~5 to 20 cm) at 10 ice rich sites, with a median subsidence rate of 0.4 cm a-1 (min: 0.2, max: 0.8 cm a-1). Here we present preliminary results comparing these long-term field data to simulations for two observation sites using the Northern Ecosystem Soil Temperature (NEST) model. NEST has been modified to include a routine that accounts for ground surface subsidence caused by the melt of excess ground ice. The excess ice content of upper permafrost in the simulations was estimated based on ratios between thaw penetration and subsidence measured at each thaw tube. The NEST simulations begin in 1901, and there is little ground surface subsidence until the 1980s. The simulated rate of ground surface subsidence increases in the 1990s. The modelled ground surface subsidence is in good agreement with the measured annual magnitudes and longer-term patterns over the measurement period from 1992 to 2017. This preliminary assessment indicates that the modified NEST model is capable of predicting gradual thaw subsidence in ice-rich permafrost environments over decadal timescales. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20012

2020063113 Opfergelt, Sophie (Université Catholique de Louvain, Earth and Life Institute, Louvain-la-Neuve, Belgium); Hirst, Catherine; Monhonval, Arthur; Mauclet, Elisabeth and Thomas, Maxime. Integrating mineral interactions with organic carbon in thawing permafrost to assess climate feedbacks [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19501, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost contains 1400-1660 Gt of organic carbon (OC), from which 5-15% will likely be emitted as greenhouse gases (GHG) by 2100. The soil organic carbon stock is distributed between a pool of particulate organic matter (POM), and a pool of mineral-associated OM (MOM). POM can be free, i.e., more readily available for microbial decomposition, or occluded within soil aggregates (involving clay minerals or Fe-Al (hydr)oxides), i.e., spatially inaccessible for microorganisms. MOM includes OC sorbed onto mineral surfaces (such as clay minerals or Fe-oxides) and OC complexed with metal cations (e.g., Al, Fe, Ca), i.e., stabilized OC. The interactions between OC and minerals influence the accessibility of OC for microbial decomposition and OC stability and are therefore a factor in controlling the C emissions rate upon thawing permafrost. In the warming Arctic, there is growing evidence for soil disturbance such as coastal erosion, thermokarst and soil drainage as a consequence of abrupt and gradual permafrost thaw. These disturbances induce changes in the physico-chemical conditions controlling mineral solubility in permafrost soils which directly affect the stability of the MOM and of the occluded POM. As a consequence, a portion of OC can be unlocked and transferred into the free POM. This additional pool of freely available OC may be degraded and amplify C emissions from permafrost to the atmosphere. Conversely, the concomitant release of metal cations upon permafrost thaw may partly mitigate permafrost C emissions by stabilization of OC via complexation or sorption onto mineral surfaces and return a portion of freely available OC to the MOM. The majority of C is emitted as CO2 but 1.5 and 3.5% of the total permafrost C emissions will be released as CH4, with implications for the atmospheric radiative forcing balance. Importantly, the proportion CH4 emitted relative to CO2 is likely to increase with increasing abrupt thaw and associated anoxic conditions, but a portion of CH4 emissions could be mitigated by the anoxic oxidation of methane mediated by the presence of Fe-oxides exposed by abrupt thaw of deep permafrost. This contribution aims at assessing how changing soil physico-chemical conditions affect interactions between mineral surfaces and OC in thawing permafrost. Scenarios of mineral-organic interactions during gradual thaw, including changes in water drainage and talik formation, and abrupt thaw including shifting redox conditions associated with thermokarst will be presented. Approaches to quantify changes in mineral-organic interactions will be discussed. By integrating the most recent studies from the permafrost carbon community with soil mineralogy, soil chemistry and soil hydrology, this contribution demonstrates that the fate of mineral-organic interactions upon thawing must be considered given their potential implications for GHG emissions. If we do not include the role of mineral-organic interactions in this puzzle, the complexities involved in soil carbon decomposition may propagate large uncertainties into coupled soil carbon-climate feedback predictions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19501

2020063135 Park, Hotaek (JAMSTEC, Yokosuka, Japan) and Kim, Youngwook. Heterogenous snow cover derived uncertainty in Arctic carbon budget [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21045, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The winter of northern Arctic regions is characterized by strong winds that lead to frequent blowing snow and thus heterogeneous snow cover, which critically affects permafrost hydrothermal processes and the associated feedbacks across the northern regions. However until now, observations and models have not documented the blowing snow impacts. The blowing snow process has coupled into a land surface model CHANGE, and the improved model was applied to observational sites in the northeastern Siberia for 1979-2016. The simulated snow depth and soil temperature showed general agreements with the observations. To quantify the impacts of blowing snow on permafrost temperatures and the associated greenhouse gases, two decadal experiments that included or excluded blowing snow, were conducted for the observational sites and over the pan-Arctic scale. The differences between the two experiments represent impacts of the blowing snow on the analytical components. The blowing snow-induced thinner snow depth resulted in cooler permafrost temperature and lower active layer thickness; this lower temperature limited the vegetation photosynthetic activity due to the increased soil moisture stress in terms of larger soil ice portion and hence lower ecosystem productivity. The cooler permafrost temperature is also linked to less decomposition of soil organic matter and lower releases of CO2 and CH4 to the atmosphere. These results suggest that the most land models without a blowing snow component likely overestimate the release of greenhouse gases from the tundra regions. There is a strong need to improve land surface models for better simulations and future projections of the northern environmental changes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21045

2020063001 Peplau, Tino (Thünen Institute of Climate-Smart Agriculture, Brunswick, Germany); Gregorich, Edward and Poeplau, Christopher. Soil organic carbon along a geothermal gradient in North-West Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9182, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Global warming will increase soil microbial activity and thus catalyse the mineralisation of soil organic carbon (SOC). Predicting the dynamics of soil organic carbon in response to warming is crucial but associated with large uncertainties, owing to experimental limitations. Most studies use in-vitro incubation experiments or relatively short-term in-situ soil warming experiments. Long-term observations on the consequences of soil warming on whole-profile SOC are still rare. Here, we used a long-term geothermal gradient in North-West Canada to study effects of warming on quantity and quality of SOC in an aspen forest ecosystem. The Takhini hot springs are located within the region of discontinuous permafrost in the southern Yukon Territory, Canada. The springs warm the surrounding soil constantly and lead to a horizontal temperature gradient of approximately 10°C within a radius of 100 meters. As these natural springs heat the ground for centuries and the forest ecosystem surrounding the springs is relatively homogenous, the site provides ideal conditions for observing long-term effects of soil warming on ecosystem properties. Soils were sampled at four different warming intensities to a depth of 80 cm and analysed for their SOC content and further soil properties in different depths. For the bulk soil, we found a significant negative relationship between soil temperature and SOC stocks. This confirms that climate change will most likely induce SOC loss and thus a positive climate-carbon cycle feedback loop. The response of five different SOC fractions to warming will also be presented. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9182

2020063049 Perron, Nia (Université de Montréal, Departement de Géographie, Montreal, QC, Canada); Pappas, Christoforos; Baltzer, Jennifer; Dearborn, Katherine and Sonnentag, Oliver. Environmental controls of Picea mariana water use in a boreal subarctic peatland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12443, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Black spruce (Picea mariana) dominated peat plateaus are an important component of northwestern Canada's heterogeneousboreal landscape. Threats to these ecosystems, including permafrost thaw and wetland expansion, could impact hydrological fluxes therefore, it is essential to understand the factors affecting the hydraulic function of black spruce in these rapidly changing landscapes. Sap velocity (Vs, cm·hr-1) is the movement of water and minerals through tree stems during the growth period and can be used as an indicator for plant water use and the quantification of tree transpiration. Here, we identified the meteorological variables driving daytime and nighttime Vs in Picea mariana (black spruce) trees growing across a 21 hectare (20 m2 grid) subarctic boreal peatland complex underlain with discontinuous permafrost, ~630 km west of Yellowknife, Northwest Territories (61°18'N, 121°18'W; ForestGEO Plot). For two consecutive growing seasons (2017 and 2018), eighteen black spruce trees were instrumented with sap flow sensors using the heat-ratio method to measure Vs. Meteorological variables including vapor pressure deficit (VPD) and photosynthetically active radiation (PAR) accounted for 57 and 73% of the variance in daytime mean Vs in 2017 and 2018, respectively, while VPD, PAR and air temperature accounted for 26 and 40% of Vs variance at night. VPD and PAR were the strongest meteorological drivers of black spruce Vs in the ForestGEO Plot. An increase in either variable corresponded to an increase in Vs across various time periods (day/nighttime). In addition, we investigated how daytime seasonal mean/maximum Vs for black spruce was affected by local environmental factors including fibric layer depth, organic matter decomposition, black spruce density, black spruce basal area, phosphorus supply rate (P) and soil water content (SWC) when physiological traits of black spruce, including diameter at breast height and crown area, were considered as covariables. It was hypothesised that stand density and basal area would affect Vs, but results indicated that only P and SWC had a (weak) influence on black spruce Vs. The variables P and SWC had a greater influence on the amplitude (seasonal daily maximum) of Vs over the sampling period. Overstory vegetation in Canada's Northwestern boreal forest is important for the terrestrial water cycle through tree water storage, and transpiration, therefore the quantification of black spruce transpiration and an improved understanding of the environmental controls of black spruce Vs in boreal peatlands would be a natural next step for this research. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12443

2020063107 Pläsken, Regina (Technical University of Munich, Germany, Department of Civil, Geology and Environmental Engineering, Munich, Germany); Gross, Julian; Krautblatter, Michael and Mamot, Philipp. Stress- and temperature dependent application of joint-constitutive-models for rock-ice mechanical systems and its implementation in a comprehensive distinct element code [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18754, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rock mechanics and its numerical representation alone are challenging tasks - if you add ice to that equation, it becomes an even more complex thing to do. Nevertheless, aiming for a better understanding of rock slopes in permafrost conditions and their mechanical behaviour depending on the scale and mechanisms of interest, integrating rock and joint characteristics, also including ice can become relevant. Krautblatter et al. (2013) suggests a rock-ice mechanical model, that describes the dominating effects for the stability of high-alpine rock slopes in permafrost conditions. This study aims to select ice filled rock joints as one of the relevant effects of Krautblatter et al. (2013) and combines it with findings of the laboratory test and derived temperature dependent failure criteria of Mamot et al. (2018). We present data and strategies for implementing temperature-dependent failure criteria for ice-filled rock interfaces into numerical distinct element code and their calibration by a comparison with preceding laboratory tests. Additionally, methods for temperature transfer within the model are suggested as well as for integrating stress-dependent application of different failure criteria in the numerical formulation. Here we show a benchmark joint-constitutive-model for rock-ice mechanical systems and its implementation in a comprehensive distinct element code. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18754

2020062997 Pointner, Georg (b.geos, Korneuburg, Austria); Bartsch, Annett and Ingeman-Nielsen, Thomas. Large-scale mapping of Arctic coastal infrastructure using Copernicus Sentinel data and machine learning and deep learning methods [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8978, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The climate change induced increased warming of the Arctic is leading to an accelerated thawing of permafrost, which can cause ground subsidence. In consequence, buildings and other infrastructure of local settlements are endangered from destabilization and collapsing in many Arctic regions. The increase of the exploitation of Arctic natural resources has led to the establishment of large industrial infrastructures that are at risk likewise. Most of the human activity in the Arctic is located near permafrost coasts. The thawing of coastal permafrost additionally leads to coastal erosion, which makes Arctic coastal settlements even more vulnerable. The European Union (EU) Horizon2020 project "Nunataryuk" aims to assess the impacts of thawing land, coast and subsea permafrost on the climate and on local communities in the Arctic. One task of the project is to determine the impacts of permafrost thaw on coastal Arctic infrastructures and to provide appropriate adaptation and mitigation strategies. For that purpose, a circumpolar account of infrastructure is needed. During recent years, the two polar-orbiting Sentinel-2 satellites of the Copernicus program of the EU have been acquiring multi-spectral imagery at high spatial and temporal resolution. Sentinel-2 data is a common choice for land cover mapping. Most land cover products only include one class for built-up areas, however. The fusion of optical and Synthetic Aperture Radar (SAR) data for land cover mapping has gained more and more attention over the last years. By combining Sentinel-2 and Sentinel-1 SAR data, the classification of multiple types of infrastructure can be anticipated. Another emerging trend is the application machine learning and deep learning methods for land cover mapping. We present an automated workflow for downloading, processing and classifying Sentinel-2 and Sentinel-1 data in order to map coastal infrastructure with circum-Arctic extent, developed on a highly performant virtual machine (VM) provided by the Copernicus Research and User Support (RUS). We further assess the first classification results mapped with two different methods, one being a pixel-based classification using a Gradient Boosting Machine and the other being a windowed semantic segmentation approach using the deep-learning framework keras. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8978

2020063046 Porter, Trevor (University Of Toronto Mississauga, Geography Department, Mississauga, ON, Canada); Holland, Kira; Froese, Duane and Kokelj, Steven. Long-term warming of Holocene winter temperatures in the Canadian Arctic recorded in stable water isotope ratios of ice wedges [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12181, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rapid and sustained warming of the northern high latitudes has led to increased permafrost thaw and retrogressive thaw slump (RTS) activity in some areas of the Arctic. Thaw slumps are common in the Tuktoyaktuk Coastlands (Northwest Territories, Canada) and expose relict ice wedge polygon networks that contain a long-term record of winter precipitation isotopes. Notably, the stable isotope geochemistry of ice wedges can be used as a paleotemperature proxy for the winter season, a seasonality that is largely missing from current understandings of Holocene paleoclimate change in the Arctic. In this study, we sampled lateral cross-sections of four relict ice wedges from RTS exposures at coastal sites on Hooper Island, Pelly Island, Richards Island and near Tuktoyaktuk. Ice blocks capturing the entire growth sequences of the ice wedges (i.e., ice wedge center to ice-sediment contact) were collected by chainsaw and kept frozen in field coolers, and later sub-sampled at high-resolution in a cold lab. The ice wedges were sub-sampled at 1-1.5 cm horizontal resolution, integrating ~1-3 ice veins per sample on average. We analysed the stable hydrogen- and oxygen-isotope ratios (d2H and d18O) of each sample (N = 803). The age of the ice was estimated by AMS-DO14C dating of 6 to 10 samples per ice wedge, evenly distributed across each wedge to capture the full range of ages. A composite d18O record spanning the period 7,400-600 cal yr BP was also constructed using the dated samples only (N = 36). The all-sample co-isotope (d2H-d18O) data are defined by regression line that is remarkably similar to the Local Meteoric Water Line, suggesting the ice wedges reliably preserve the isotopic composition of local precipitation, which is strongly influenced by mean air temperatures. The composite record shows an increase in d18O over the last 7,400 years which we interpret as a long-term warming trend of the mean winter climate. This warming trend is largely explained by increasing November-April insolation at 69°N, a result that is corroborated by two independent high-resolution ice wedge records from the Siberian Arctic and is also in agreement with model-based simulations of the winter climate. This record, the first of its kind in the North American Arctic, provides a more seasonally holistic perspective on Holocene climate change and highlights the potential to use permafrost isotope records to fill paleoclimate knowledge gaps in Arctic regions were more traditional precipitation isotope archives (e.g., ice cores) do not exist. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12181

2020063030 Ravanel, Ludovic (Université Savoie Mont Blanc, Environnements, Dynamiques et Territoires de la Montagne (EDYTEM), Montagne, France); Preunkert, Suzanne; Guillet, Grégoire; Kaushik, Suvrat; Magnin, Florence and Deline, Philip. Ice aprons on steep north faces; oldest surface ice in the Alps? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11062, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Ice aprons are small but ubiquitous ice masses in high alpine ranges such as the Mont Blanc massif. Mainly present on its north faces above 3200 m a.s.l., they are a condition for practice of the so-called "traditional" mountaineering (now on the Intangible Cultural Heritage UNESCO list) and an indicator of the presence of permafrost in the bedrock. Most often thin (<10 m), these ice aprons are very sensitive to increasing air temperatures while their evolution during the recent decades suggests many coming disappearances in the short term and, consequently, a change in the permafrost thermal regime and a related increase in the rockfall occurrence. Very few studied, ice aprons however represent an important glacial inheritance. We suggest that ice aprons are made up of very old ice, likely the oldest surface one in the Alps. In the north face of the Mont Blanc du Tacul (4248 m a.s.l.) for example, following the disappearance of the upper layers due to the increased occurrence of summer heatwaves, the ice on the present surface formed c. 2700 ago years (cold phase of Göschener I), against probably 200-300 years for the ice at the front of the Mer de Glace, the largest glacier in the French Alps. We present the ice ages acquired from five ice aprons on rock walls of the Mont Blanc massif together with ice ages from two glacier tongues of the massif (Mer de Glace and Miage Glacier). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11062

2020063008 Rehder, Zoé (Max Planck Institute for Meteorology, Hamburg, Germany); Zaplavnova, Anna and Kutzbach, Lars. Drivers of methane variability in Arctic ponds [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9670, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic ponds are significant sources of methane, but their overall contribution to pan-Arctic methane emissions is still uncertain. Ponds come in different sizes and shapes, which are associated with different stages of permafrost degradation. Methane concentrations and fluxes show large spatiotemporal variability. To better understand this variability, as a first step towards upscaling pond methane emissions, we studied 41 ponds in the Lena River Delta, northeast Siberia. We collected water samples at different locations and depths in each pond and determined methane concentrations using gas chromatography. Additionally, we collected information on the geomorphology, vegetation cover as well as on key physical and chemical properties of the ponds and combined them with meteorological data. The ponds are divided into three geomorphological types with distinct differences in methane concentrations: water-filled degraded polygon centers, water-filled interpolygonal troughs and larger collapsed and merged polygons. These ponds exhibit mean surface methane concentrations (with standard deviation) of 1.2 ± 1.3 mmol L-1, 4.3 ± 4.9 mmol L-1 and 0.9 ± 0.7 mmol L-1 respectively, while mean bottom methane concentrations amount to 102.6 ± 145.4 mmol L-1, 263.3 ± 275.6 mmol L-1 and 17.0 ± 34.1 mmol L-1. Using principle components and multiple linear regressions, we show that a large portion of spatial variability can be explained by the ponds' shape and vegetation. Merged ponds have the least relative vegetation cover, and they also tend to be better mixed, both of which explains the lowest methane concentrations and the lowest variability in these ponds. Vegetation covers larger fractions in polygon centers and troughs, leading to a larger methane variability. Finally, troughs, as they are underlain by ice wedges, exhibit more pronounced stratification and the highest methane concentrations. More results will be presented at the conference. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9670

2020063083 Reid, Lucas (Karlsruhe Institute of Technology, Institute of Water and River Basin Management, Karlsruhe, Germany); Scherer, Ulrike and Zehe, Erwin. Seasonal melting simulation of permafrost rock glaciers and their potential contribution to sediment loads in alpine catchments [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17504, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

A common issue with large scale erosion modelling is that local processes are often unaccounted for, either because they haven't been included in the model conceptually, or because they are undetected yet. On the other hand, significant deviations from such a general soil erosion model to the measurements can reveal those local processes. We compared the average yearly sediment amounts of a network of turbidity measurement stations in the catchment of the alpine River Inn to the results of the large scale erosion model RUSLE2015 (Panagos et. al.) for long term yearly erosion amounts and found a significant underestimation of sediment loads in three sub catchments. An important source of sediments in alpine rivers comes from glaciers, which explains the high loads in one of the stations, but two of the three high sediment load sub catchments are too low to have substantial valley glaciers. But another potential source of glacial sediment exists in the form of permafrost soils and in this case a specific permafrost form: rock glaciers. Rock glaciers in particular have been spotted in those two high sediment load catchments, but since they are hard to detect from remote sensing due to the surface being covered with rocks, the existence or the exact spatial extent is often unknown. But with rising temperatures in the Alps, the areas in which permafrost rock glaciers can exist decreases every year and the depth of the seasonal melting layer increases. We propose the hypothesis that the high sediment loads in those sub catchments are caused by increasingly deeper melting of permafrost rock glaciers. This process releases fine materials which have been trapped frozen since the glacial period and are now being eroded and transported to the alpine streams. To get an estimation of potential erodible material from rock glacier melting in the respective sub catchments, we developed a model to simulate the heat diffusion from the air into the frozen ground, while accommodating for the change in specific thermal capacity. The model (developed in Python) takes air temperature time series data as input and can be configured for varying ground stratification setups with different thermal diffusivity values depending on the ground properties. From the simulated melting depth of an average square meter of rock glacier we extrapolate the mass of melted material to the potential permafrost erosion material available in the River Inn sub catchments. We show that this source of sediments can be significant and needs to be factored in should an erosion model be used to calculate sediment input into the rivers. But, with the estimation of sediment load from permafrost origins narrowed down, improving a large-scale erosion model like the RUSLE2015 for this alpine mountain region by accounting for local processes like this one is possible. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17504

2020063002 Robson, Benjamin Aubrey (University of Bergen, Department of Geography, Bergen, Norway); Bolch, Tobias; MacDonell, Shelley; Hölbling, Daniel; Rastner, Philip and Schaffer, Nicole. Use of convolution neural networks and object based image analysis for automated rock glacier mapping [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9201, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rock glaciers are an important, but often overlooked, component of the cryosphere and are one of the few visible manifestations of permafrost. In certain parts of the world, rock glaciers can contribute up to 30% of catchment streamflow. Remote sensing has permitted the creation of rock glacier inventories for large regions, however, due to the spectral similarity between rock glaciers and the surrounding material, the creation of such inventories is typically conducted based on manual interpretation of remote sensing data which is both time consuming and subjective. Here, we present a method that combines deep learning (convolutional neural networks or CNNs) and object-based image analysis (OBIA) into one workflow based on freely available Sentinel-2 imagery, Sentinel-1 interferometric coherence, and a Digital Elevation Model. CNNs work by identifying recurring patterns and textures and produce a heatmap where each pixel indicates the probability that it belongs to a rock glacier or not. By using OBIA we can segment the datasets and classify objects based on their heatmap value as well as morphological and spatial characteristics and convert the raw probability heatmap generated by the deep learning into rock glacier polygons. We analysed two distinct catchments, the La Laguna catchment in the Chilean semi-arid Andes and the Poiqu catchment on the Tibetan Plateau. In total, our method mapped 72% of the rock glaciers across both catchments, although many of the individual rock glacier polygons contained false positives that are texturally similar, such as debris-flows, avalanche deposits, or fluvial material causing the user's accuracy to be moderate (64-69%) even if the producer's accuracy was higher (75%). We repeated our method on very-high resolution Pléiades satellite imagery (resampled to 2 m resolution) for a subset of the Poiqu catchment to ascertain what difference the image resolution makes. We found that working at a higher spatial resolution has little influence on the user's accuracy (an increase of 3%) yet as smaller landforms were mapped, the producer's accuracy rose by 13% to 88%. By running all the processing within an object-based analysis it was possible to both generate the deep learning heatmap and automate some of the post-processing through image segmentation and object reshaping. Given the difficulties in differentiating rock glaciers using image spectra, deep learning offers a feasible method for automated mapping of rock glaciers over large regional scales. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9201

2020063055 Rudy, Ashley (Northwest Territories Geological Survey, Yellowknife, NT, Canada); Kokelj, Steve; Wilson, Alice; Ensom, Tim; Morse, Peter and Klengenberg, Charles. Developing a collaborative permafrost research program; the Dempster -Inuvik to Tuktoyaktuk highway research corridor, Northwest Territories, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12610, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Beaufort Delta region in Northwest Territories, Canada is one of the most rapidly warming areas on Earth. Permafrost thaw and climate change are major stressors on northern infrastructure, particularly in this region which hosts the highest density of Arctic communities and the longest road network constructed on ice-rich permafrost in Canada. The Dempster and Inuvik to Tuktoyaktuk Highways (ITH) comprise a 400-km corridor connecting the region with southern Canada. The corridor delivers a unique opportunity to develop a societally-relevant, northern-driven permafrost research network to encourage collaboration, and support pure and applied studies that engage stakeholders, encourage community participation, and acknowledge northern interests. Successful implementation requires leadership and institutional support from the Government of the Northwest Territories (GNWT) and Inuvialuit and Gwich'in Boards and landowners, and coordination between research organizations including NWT Geological Survey, Aurora Research Institute, Geological Survey of Canada, and universities to define key research priorities, human and financial resources to undertake studies, and protocols to manage data collection and reporting. In 2017, a state of the art ground temperature monitoring network was established along the Dempster-ITH corridor by the GNWT in collaboration with Federal and Academic partners. This network in combination with the maintenance of the Dempster Highway and recent design and construction of the ITH, has created a national legacy of permafrost geotechnical, terrain and geohazard information in this region. The objectives of this program are to integrate old and new data to synthesize physiographic, hydrological, thermal, and geotechnical conditions along the corridor, and to develop applied permafrost research projects that support planning and maintenance of this critical northern infrastructure. In this presentation, we highlight: 1) a collaborative research framework that builds northern capacity and involves northerners in the generation of knowledge and its application to increase community based permafrost monitoring; 2) summaries of existing infrastructure datasets and their foundation for research; and 3) new projects that address emerging climate-driven infrastructure stressors. As the effects of climate change on permafrost environments, infrastructure and communities continue to increase, the need for northern scientific capacity and applied research to support informed decision-making, climate change adaptation and risk management will become increasingly critical. The development of resilient researcher-stakeholder-community relationships is also necessary for the scientific and research initiatives to reach their potential. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12610

2020062993 Sannel, A. Britta K. (Stockholm University, Department of Physical Geography, Stockholm, Sweden). Ground thermal variability and landscape dynamics in a northern Swedish permafrost peatland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8790, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost peatlands cover extensive areas in subarctic regions, and store large amounts of soil organic carbon that can be remobilized as active layer deepening and thermokarst formation is expected to increase in a future warmer climate. In northern Fennoscandia peatland initiation started soon after the last deglaciation, and throughout most of the Holocene the peatlands were permafrost-free fens. Colder conditions during the Little Ice Age resulted in epigenetic permafrost aggradation (Kjellman et al., 2018; Sannel et al., 2018). Today, these ecosystems are characterized by a complex mosaic of different landscape units including elevated peat plateaus and palsas uplifted above the surrounding wetlands by frost heave, and collapse features such as fens and thermokarst lakes formed as a result of ground-ice melt. This small-scale topographic variability makes the local hydrology, and possibly also the ground thermal regime very variable. In a peat plateau complex in Tavvavuoma, northern Sweden, ground temperatures and snow depth have been monitored within six different landscape units; on a peat plateau, in a depression within a peat plateau, along a peat plateau edge (close to a thermokarst lake), at a thermokarst lake shoreline, in lake sediments and in a fen. A thermal snapshot from 2007/08 shows that permafrost is present in all three peat plateau landscape units, and the mean annual ground temperature (MAGT) at 2 m depth is around -0.3 °C. In the three low-lying and saturated landscape units taliks are present and the MAGT at 1 m depth is 1.0-2.7 °C. Small-scale topographic variability is a key parameter for ground thermal patterns in this landscape affecting both local snow depth and soil moisture. Wind redistribution of snow creates a distinctive pattern with thin snow cover on elevated landforms and thicker cover in low-lying landscape units. Permafrost is present in peat plateaus where the mean December-April snow cover is shallow (<20 cm). In a small depression on the peat plateau permafrost exists despite a 60-80 cm mean December-April snow cover, but here the maximum annual ground temperature at 0.5 m depth is 8-9 °C warmer than in the surrounding peat plateau and the active layer is deeper (100-150 cm compared to 50-55 cm). In recent years, 2006-2019, the depression has experienced continued ground subsidence as a result of permafrost thaw, and the dominant vegetation has shifted from Sphagnum sp. to Cyperaceae. This transition could be the initial stage in collapse fen or thermokarst pond formation. In the same time period extensive block erosion and shoreline retreat has occurred along sections of the peat plateau edge where the mean December-April snow cover is deep (>80 cm). In a future warmer climate, permafrost thaw will have a continued impact on landscape changes, shifts in hydrology, vegetation and carbon exchange in this dynamic and climate-sensitive environment. References Kjellman, S.E. et al., 2018: Holocene development of subarctic permafrost peatlands in Finnmark, northern Norway. The Holocene 28, 1855-1869, doi:10.1177/0959683618798126. Sannel, A.B.K. et al., 2018: Holocene development and permafrost history in sub-arctic peatlands in Tavvavuoma, northern Sweden. Boreas 47, 454-468, doi:10.1111/bor.12276. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8790

2020063108 Scandroglio, Riccardo (Technical University of Munich, Munich, Germany) and Krautblatter, Michael. Climate-change-induced changes in steep alpine permafrost bedrock; 13 years of 3D-ERT at the Steintälli Ridge, Switzerland. [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18808, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Warming of mountain permafrost leads to growth of active layer thickness and reduction of rock wall stability. The subsequent increase of instable rock volumes can have disastrous or even fatal consequences, especially when cascading events are simultaneously triggered. This growth of climate-change-connected hazard, together with the recent increase of exposition of infrastructure and people, poses the alpine environments at a high risk, which needs to be monitored. Laboratory-calibrated Electrical Resistivity Tomography (ERT) has shown to provide a sensitive record for frozen vs. unfrozen conditions, presumably being the most accurate quantitative permafrost monitoring technique in permafrost areas where boreholes are not available. The data presented here are obtained at the Steintalli ridge in Switzerland, which presents highly vulnerable permafrost conditions. A consistent 3D field set-up, the robust temperature calibration and the quantitative inversion scheme allow to compare measurements from the longest time series (2006-2019) of ERT in steep bedrock. A direct link to mechanical changes measured with tape extensometer is provided. Comparison of repeated hourly measurements as well as Wenner and Schlumberger arrays are also shown here, in order to increase the robustness of the delivered results. Confirming the long-term observation from air temperatures, results from multiple parallel transects show an average resistivity reduction of 22%, concentrated at deeper layers of the permafrost lens. The permafrost area in the 3D cross sections also decreased from 30 to 10% (about 500 to 150 m2 in our transects), with losses mainly localized on the south-east part of the study site, but in some cases also extending to the north face. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18808

2020063087 Scheel, Maria (Aarhus University, Arctic Research Centre, Aarhus, Denmark); Christensen, Torben R.; Rundgren, Mats; Jacobsen, Carsten Suhr and Zervas, Athanasios. Microbial life in collapsing permafrost in NE Greenland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17683, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In recent years, permafrost-affected soils have been shown to be gradually subject of thawing (IPCC, 2019). Formerly frozen soil organic carbon stocks hence become increasingly susceptible to microbial decomposition and transformation into greenhouse gases (Schuur et al., 2015). An estimated 20% of Arctic permafrost areas are subject of melting of belowground ice and consequent collapse (Olefeldt et al. 2016), but these thermokarst landscapes are often difficult to assess. In 2018, a thermokarst developed into a thermal erosion gully in close vicinity to the Zackenberg Research Station. As one of the main stations of the Greenland Ecosystem Monitoring (GEM) program, the monitoring of various ecosystem parameters at this site during the past 25 years, including hydrology, soil temperature and active layer depth, enables a spatiotemporally precise description of the thermokarst's physical progression. In order to characterize the development of a thermokarst soil microbial community and understand its spatial distribution and taxonomic biodiversity, soil cores of 30 cm above and below an ice lens were extracted in August 2018, as well as after a dry and warm summer season in September 2019, until 90 cm depth to also sample still frozen permafrost soils. Soil characterization included loss on ignition, radiocarbon dating and microbial viability assays for both years. Bacterial 16S rDNA V3-V4 and fungal ITS1 gene region amplicons of extracted DNA were sequenced and analyzed. With the microbiome involved in biochemical processes such as nitrogen fixation, methane production and oxidation as well as CO2 respiration, knowledge about abundance, genetic and adaptation potential of bacteria, archaea and microeukaryotes in fast changing permafrost soils affects several ecosystem carbon fluxes significantly. This work is part of a project, describing both the taxonomic and functional composition of this thermokarst microbiome, including the use of multi-omics to reveal the carbon cycling gene potential and expression in combination with in situ and laboratory incubation gas fluxes of CO2, N2O and CH4. These biological and biogeochemical insights from this event are put into perspective with long-term, maintained data supplied by the GEM. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17683

2020063122 Schroeder, Tanja (Technical University of Munich, Munich, Germany); Scandroglio, Riccardo; Stammberger, Verena; Wittmann, Maximilian and Krautblatter, Michael. New multi-phase thermo-geophysical model; validate ERT-monitoring & assess permafrost evolution in alpine rock walls (Zugspitze, German/Austrian Alps) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19984, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed. Electrical Resistivity Tomography (ERT) is the predominant permafrost monitoring technique in high mountain areas. Its high temperature sensitivity for frozen vs. unfrozen conditions, combined with the resistivity-temperature laboratory calibration on Wettersteinkalk (Zugspitze) (Krautblatter et al. 2010) gives us quantitative information on site-specific rock wall temperatures (Magnin et al. 2015). Long-term ERT-Measurements (2007/2014 - now) were taken at the Kammstollen along the northern Zugspitze rock face. Two high-resistivity bodies along the investigation area reach resistivity values =104.5O m (~-0.5°C), indicating frozen rock, displaying a core section with resistivities =104.7O m (~-2°C) (Krautblatter et al., 2010). We can differentiate seasonal variability, seen by laterally aggrading and degrading marginal sections (Krautblatter et al., 2010) and singular effects due to environmental factors and extreme weather events. Here, we present a new local high-resolution numerical, process-orientated thermo-geophysical model (TGM) for steep permafrost rock walls. The model links apparent resistivities, the ground thermal regime and meteorological forcings as seasonality and long-term climate change to validate the ERT and project future conditions. The TGM comprises a surface energy balance model, conductive energy transport, turbulent and seasonal heat fluxes (sensible, latent, melt and rain heat fluxes) including phase-change, as well as a multi-phase rock wall composition. Finally, we can reproduce the natural temperature field in the rock wall, assess the spatial-temporal permafrost evolution in alpine rock walls, validate the ERT measurements via the new TGM and the applicability of the laboratory derived resistivity-temperature relationship by Krautblatter et al. (2010) for natural rock-wall conditions. Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. & Kemna, A. (2010): Temperature- calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps). J. Geophys. Res. 115: F02003. Magnin, F., Krautblatter, M., Deline, P., Ravanel, L., Malet, E., Bevington, A. (2015): Determination of warm, sensitive permafrost areas in near-vertical rockwalls and evaluation of distributed models by electrical resistivity tomography. J. Geophys. Res. Earth Surf., 120, 745-762. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19984

2020062999 Seco, Roger (University of Copenhagen, Department of Biology, Copenhagen, Denmark); Holst, Thomas; Westergaard-Nielsen, Andreas; Li, Tao; Simin, Tihomir; Jansen, Joachim; Crill, Patrick; Friborg, Thomas; Holst, Jutta; Rinne, Janne and Rinnan, Riikka. Volatile organic compound fluxes in a subarctic peatland and lake [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9007, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic climate is warming twice as much as the global average, due to a number of climate system feedbacks, including albedo change due to retreating snow cover and sea ice, and the forest cover expansion across the open tundra. Northern ecosystems are known to emit trace gases (e.g., methane and volatile organic compounds, VOCs) to the atmosphere, from sources as diverse as soils, vegetation and lakes. These trace gas fluxes are likely to show a trend towards greater emissions with climate warming. Here we report ecosystem-level VOC fluxes from Stordalen Mire, a subarctic peatland complex with a high fraction of open pond and lake surfaces, underlain by discontinuous permafrost and located in the Subarctic Sweden (68°20' N, 19°03' E). In 2018, we deployed two online mass spectrometers (PTR-TOF-MS) to measure rapid fluctuations in VOC mixing ratios and to quantify ecosystem-level fluxes with the eddy covariance technique. One of the instruments obtained a growing-season-long dataset of biogenic emissions from palsa mire vegetation dominated by mosses (e.g., Sphagnum spp.), graminoids (such as Eriophorum spp. and Carex spp.), dwarf shrubs (e.g. Empetrum spp. and Betula nana) surrounding the ICOS Sweden Abisko-Stordalen long-term measurement station. The second instrument measured VOC fluxes during two contrasting periods (the peak and the end of the growing season) from a subarctic lake and its adjacent fen, permafrost-free, minerotrophic wetland with vegetation dominated by tall graminoids, mainly Carex rostrata and Eriophorum angustifolium. At both sites, isoprene was the dominant VOC emitted by vegetation, showing clear diurnal patterns along the season and especially during the peak of the growing season in July. At the ICOS Sweden station, isoprene fluxes exceeded 2 nmol m-2 s-1 on several days in July, with a July monthly average midday emission of 1 nmol m-2 s-1. The fen site showed average midday emissions of 2 nmol m-2 s-1 during the peak growing season. Other VOCs emitted by vegetation at both sites in July were, with decreasing magnitude, methanol, acetone, acetaldehyde and monoterpenes. In contrast, acetaldehyde and acetone were not emitted but mostly deposited to the fen at the end of the season. In contrast to the wetland, the lake was a sink for acetaldehyde and acetone during all measurement periods. Thermal imaging and spectral analysis of vegetation will be used to assess relationships between VOC fluxes, vegetation surface temperatures and phenology under varying environmental conditions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9007

2020063090 Semochkina, Anna (Lomonosov Moscow State University, Faculty of Geography, Geomorphology and Paleogeography, Moscow, Russian Federation); Streletskaya, Irina; Belayaev, Vladimir; Kharchenko, Sergey; Kuznetsova, Julia and Lugovoy, Nicolai. Impact of the late Pleistocene permafrost relics on spatial patterns of linear erosion in agricultural landscapes of central European Russia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17788, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

More than 90% territory of Russia influenced by modern and relict cryolithogenesis (Velichko, 1996). Many relict periglacial features bear witness of Late Pleistocene climate oscillation events and nowadays they are widespread in Mid-Latitude Western Europe including Russian territory. It is known, paleocryogenic factor influence on soil cover's structure on the different geomorphological position. However interrelation problem between various type of relict cryogenic features (RCF) and modern geomorphological processes, especially erosion and sedimentation, and soil degradation stays unsearched. The goal of research - to estimate, how RCF affects modern processes and soil cover structure within the agricultural areas (Yaroslavl and Kursk regions). The research also is concentrated on evaluation relationship between different types of the relic cryogenic features and intensity and spatial distribution of soil erosion and deposition processes on cultivated slopes. Materials and Methods This study is based on the analysis of aerial photographs (Sentinel, BingSat, Google, Yaundex), including DEMs and aero photos from air drone, and new field surveys. Also we used a group of methods to estimate erosion rates within the small catchments areas (soil profile morphology, analysis of Cesium-137 supply in soil, empirical-mathematical models USLE/GGN and WaTEM/SEDEM). It is supposed to test modern methods (neuron net) for automatic decoding of paleocryogenic relief and creating an appropriate data set - contours or at least positions (centroids) of these forms. Results The relict permafrost-thermokarst relief prevails in the Yaroslavl Region; a polygonal relief with a block length of 40-50 m is visible almost everywhere. In new-ploughed fields inside the polygons, a second generation of blocks with a side length of 10-20 m is visible. To the south, on the territory covered with loess-loam soil stripes or trenches can be also detected. But on this southern territories relict cryogenic network are smaller, the relief of small knolls and depressions are widespread. They appeared due to ice-wedges melting. An analysis of the structure of the erosion-channel network in the Kursk region showed that numerous small ravines and washed-out troughs, widespread on agricultural fields, largely inherit or developed due to the RCM forms. Conclusions The period of transition of active cryogenic forms to the relict state is associated with numerous processes of burial, redeposition and destruction of material and microrelief alignment. RCF affects the structure and dynamics of modern erosion processes: shape and density of the erosion network; the direction, extent and complexity of the slope flows structure, the presence and alternation of redeposition and transit zones; sediment budget structure of elementary slope, gullys and small river catchment areas. *This research is supported by the Russian Foundation for Basic Research (Project No. 18-05-01118a). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17788

2020063141 Sergeant, Flore (Université Laval, Géologie et Génie Géologique, Quebec City, QC, Canada); Therrien, Rene; Oudin, Ludovic; Jost, Anne and Anctil, François. Comparing streamflow analysis and remote sensing observations to assess climate change impact on permafrost degradation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21789, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Due to polar amplification of climate change, high latitudes are warming up twice as fast as the rest of the world. This warming leads to permafrost thawing, which induces greenhouse gases release, ground subsidence, and modifies surface and subsurface hydrologic regimes. Ground subsidence in turn affects local infrastructure stability. In this context and to better manage future infrastructures and water resources of northern regions, it is crucial to be able to evaluate the thawing rate of permafrost. In many Arctic zones, the frequency of environmental disturbances caused by permafrost thawing increases so rapidly that maintaining an accurate inventory of the state of permafrost at a regional scale represents a great challenge. Moreover, depending on the study area and the permafrost ice content, the thawing rate can vary from millimetres to decimeters per year. Another current challenge is the limited availability of temporal and spatial data on permafrost thawing rates. To address the above challenges, two indirect methods are used: (1) Arctic river streamflow analysis method and (2) Ground settlement analysis method via satellite image observation. Both methods use free-access data that have an exceptionally large temporal and spatial coverage capacity for such a poorly instrumented region. The first method analyses the recession events' behavior of Arctic streams and relates those behaviors to changes in catchment-scale depth to permafrost that influences storage-discharge dynamics. This work differs from previous hydrological system analysis in northern systems in that it looks at long-term trends (>10 years) in recession intercept to assess permafrost dynamics, while other studies looked at recession characteristics within a season to assess active-layer dynamics. The second method analyses satellite images of the Arctic ground and associates surface elevation change to long-term permafrost degradation due to climate change. Both methods have already been tested through multiple local investigations and gave promising results. The recession flow analysis method has been applied to Yukon river basin, northern Sweden basins and Lena basin in Siberia, while the remote sensing analysis method has been tested on Baffin Island, Herschel Island in Canada, North Slope of Alaska and the Tibetan Plateau. However, no comparative study and no large-scale application have been conducted so far. Extending the analysis to hundreds of Arctic basins and comparing the resulting permafrost-thawing rate values from both methods constitute the innovative aspect of this project. KEY WORDS: climate change, permafrost thawing, storage-discharge dynamics, ground subsidence, satellite images [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21789

2020063143 Serov, Pavel (Arctic University of Norway, Centre for Arctic Gas Hydrate, Environment and Climate, Tromso, Norway); Patton, Henry; Waage, Malin; Shackleton, Calvin; Mienert, Jurgen; Andreassen, Karin and Hubbard, Alun. Methane hydrate mobilization by ice stream erosion during the last glacial [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21868, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

During the past ~2.6 Ma, some 30 glaciations have caused episodic high pressure and low temperature conditions and forced growth and decay of extensive subglacial methane hydrate accumulations globally. Research on Arctic methane release has primarily focused on warm, interglacial episodes when hydrates became unstable across territories either abandoned by former ice sheets or affected by permafrost degradation. Here we present a new mechanism--the subglacial erosion of gas hydrate-bearing sediments--that actively mobilizes methane in hydrate and dissolved form and delivers it to the ice sheet margin. We investigate this mechanism using geophysical imaging and ice sheet/gas hydrate modeling focused on a study site in Storfjordrenna, that hosted large ice stream draining the Barents Sea ice sheet. During the last glacial, we find that this ice stream overrode an extensive cluster of conduits that supplied a continuous methane flux from a deep, thermogenic source and delivered it to the subglacial environment. Our analysis reveals that 15,000 to 44,000 m3 of gas hydrates were subglacially eroded from the 17 km2 study site and transported to the shelf-edge. Given the abundance of natural gas reservoirs across the Barents Sea and marine-based glaciated petroleum provinces elsewhere, we propose that this mechanism had the potential to mobilize a substantial flux of subglacial methane throughout multiple Quaternary glacial episodes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21868

2020063020 Shakil, Sarah (University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada); Tank, Suzanne; Kokelj, Steve and Vonk, Jorien. Downstream persistence of particulate organic carbon released from thaw slumps on the Peel Plateau, NT, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10567, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Underlain by ice-rich permafrost, the Peel Plateau in western Canada is highly susceptible to rapid permafrost degradation in the form of retrogressive thaw slumps and has experienced a nonlinear intensification in the area, volume, and thickness of permafrost thawed since 2002. These slumps tend to occur along stream networks, which flow directly into the Peel River, through the Mackenzie Delta, and into the Beaufort Sea. Thus, lateral transport of previously sequestered organic carbon from these features has the potential to propagate far downstream. Upstream-downstream comparisons have shown that thaw slumps mobilize material to stream systems primarily in the form of particulate organic carbon (POC), increasing organic carbon yields by orders of magnitude, and switching stream networks to particle-dominated systems. Furthermore, the bulk POC released from slumps can be upwards of 10,000 14C years old, and base-extracted fluorescence measurements suggest material is more reworked since terrestrial production compared to upstream material. To determine how far this effect propagates downstream we measured particulate and dissolved organic carbon (DOC) fluxes across stream transects extending 0.4 to 1 km downstream of thaw slumps in 1st to 2nd order streams and found no consistent decrease in TSS or POC fluxes with transit downstream. In addition, we measured the composition (%POC, C:N, fluorescence, D14C) and flux of DOC and POC within the ~1100 km2 Stony Creek watershed, examining tributary streams representing different vegetative, slump-density, and geological units in addition to the Stony Creek mainstem, to determine contributions to downstream flux. We found organic carbon fluxes were dominated by slump-mobilized POC at all points downstream of disturbance, and that these organic carbon fluxes were greater than any non-disturbed tributary stream. The 14C age of POC along the Stony Creek mainstem increased by thousands of years with the introduction of slump inputs and remained similarly depleted in 14C at the watershed outlet. Using historical suspended sediment, POC, and discharge data for the 75,000 km2 Peel River drainage basin containing the Stony Creek watershed, we will examine whether there have been increases in instantaneous sediment and POC fluxes during the thaw season to track the trends of intensifying slump activity that have been documented on the Peel Plateau. Constraining the downstream effect of these abrupt, localized disturbances may improve detection and prediction of change that will likely cascade through the region over the coming decades. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10567

2020063125 Sirbu, Flavius (West University of Timisoara, Department of Geography, Timisoara, Romania); Onaca, Alexandru; Ardelean, Florina; Magori, Brigitte and Urdea, Petru. Present state of marginal mountain permafrost in south eastern Europe [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-20066, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost exists in the highest mountains of SE Europe (South Carpathians, Rila, Pirin) in small isolated patches, where local topography and landforms provide conditions for winter ground cooling and for shading and ground thermal isolation during summer. We present a summary of the present state of mountain permafrost in the study area by analyzing the results of ERT (electrical resistivity tomography) and GPR (ground penetrating radar) profiles together with thermal measurements of ground surface and air performed at the sites of documented permafrost occurrence. The results are put in context with recent climate evolution by a decade of thermal measurements in the South Carpathians and three years in the Rila and Pirin Mountains. Despite differences in air temperature and snow cover timing and thickness the permafrost extent remains constant at the study sites. The active layer is thick (between 5-10 m), whereas the permanently frozen layers vary in thickness even for the same study site, and are relatively thin compared to sites located in the Alps or the Andes, indicating that the existing permafrost is in imbalance with the current climate. Snow cover is probably the most important factor in seasonal evolution, controlling both the winter cooling and the summer thermal decoupling of ground and air temperature. Recent evolution shows a tendency of shifting the snow cover period with later deposit and later thaw which favors permafrost conditions. We also observe a significant difference between Southern Carpathians and Rila and Pirin mountains, with snow patches lasting until late summer, August or September, in the later. However snow cover present strong local variations in terms of thickness and isolating properties which makes it the least study and least understood factor in mountain permafrost dynamics in SE Europe. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-20066

2020063144 Speetjens, Niek (Vrije Universiteit Amsterdam, Department of Earth Sciences, Earth and Climate Cluster, Amsterdam, Netherlands); Tanski, George; Martin, Victoria; Wagner, Julia; Richter, Andreas; Hugelius, Gustaf; Lodi, Rachele; Knoblauch, Christian; Koch, Boris; Stedmon, Colin and Vonk, Jorien. Landscape-driven carbon export from small coastal permafrost watersheds [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-21915, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Ongoing climate warming in the western Canadian Arctic is leading to thawing of permafrost soils and subsequent mobilization of its organic matter (OM) pool. Part of this mobilized terrestrial OM enters the aquatic system as dissolved organic matter (DOM) and is laterally transported from land to sea. Mobilized DOM is an important source of nutrients for ecosystems as it is available for microbial breakdown, the consequent turnover of the dissolved organic carbon (DOC) fraction of DOM serving as a potential source of greenhouse gases. We are beginning to understand spatial controls on the release of DOM as well as the quantities and fate of this material in large arctic rivers, but these processes remain systematically understudied in small, high-arctic watersheds, despite the fact that these particular watersheds experience strongest warming. We sampled soil (active layer and permafrost) and water (porewater and stream water) from two small catchments along the Yukon coast, Canada, during the summers of 2018 and 2019. We assessed the organic carbon quantity (using DOC and soil OC content), quality (d13C-DOC, C/N ratios and optical properties including components modelled with EEMs-PARAFAC), the turnover of DOM through incubation experiments as well as nutrients and stable water isotopes. We classify and compare different landscape units by quantitative and qualitative change across gradients from soil stocks down to the catchment outflow. Our results show that substantial variation in DOC concentrations exists among various landscape units as well as between active layer and permafrost. We find high soil carbon stocks and leaching potentials from these coastal tundra soils. Moreover, we find that permafrost DOM is utilized rapidly upon thaw. Using remote sensing-based landscape classification, we are planning to upscale carbon and nutrient fluxes for the panarctic coastal zone to account for small yet numerous high-arctic watersheds in lateral terrestrial OM transfer from land to sea Under current climate projections and with continued permafrost thaw altered lateral fluxes may have profound impacts on the arctic aquatic ecosystem and arctic carbon cycling. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-21915

2020063111 Steinert, Norman (Complutense University of Madrid, Department of Earth Sciences and Astrophysics, Madrid, Spain); González-Rouco, Fidel; Hagemann, Stefan; de Vrese, Philipp; Garcia-Bustamante, Elena; Jungclaus, Johann; Lorenz, Stephan; Melo-Aguilar, Camilo and Navarro, Jorge. Impact of improved land model depth and hydrology on climate change projections [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19277, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The representation of the thermal and hydrological state in the land model component of Earth System Models is crucial to have a realistic simulation of subsurface processes and the coupling between the atmo-, litho- and biosphere. There is evidence suggesting an inaccurate simulation of subsurface thermodynamics in current-generation Earth System Models, which have Land Surface Models that are too shallow. In simulations with a bottom boundary too close to the surface, the energy propagation and spatio-temporal variability of subsurface temperatures are affected. This potentially restrains the simulation of land-air interactions and subsurface phenomena, e.g. energy/moisture balance and storage capacity, freeze/thaw cycles and permafrost evolution. We introduce modifications for a deeper soil into the JSBACH soil model component of the MPI-ESM for climate projections of the 21st century. Subsurface layers are added progressively to increase the bottom boundary depth from 10 m to 1400 m. This leads to near-surface cooling of the soil and encourages regional terrestrial energy uptake by one order of magnitude and more. The depth-changes in the soil also have implications for the hydrological regime, in which the moisture between the surface and the bedrock is sensitive to variations in the thermal regime. Additionally, we compare two different global soil parameter datasets that have major implications for the vertical distribution and availability of soil moisture and its exchange with the land surface. The implementation of supercool water and water phase changes in the soil creates a coupling between the soil thermal and hydrological regimes. In both cases of bottom boundary and water depth changes, we explore the sensitivity of JSBACH from the perspective of changes in the soil thermodynamics, energy balance and storage, as well as the effect of including freezing and thawing processes and their influence on the simulation of permafrost areas in the Northern Hemisphere high latitudes. The latter is of particular interest due to their vulnerability to long-term climate change. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19277

2020063072 Stoll, Verena (Technical University Munich, Department of Landslide Research, Munich, Germany); Scandroglio, Riccardo and Krautblatter, Michael. Modelling rock walls destabilization caused by hydrostatic pressure in frozen/unfrozen bedrock (Hochvogel & Zugspitze, Germany) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14338, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

One of the most important but still unknown destabilizing factors of rock faces in periglacial environments is the contribution of water in terms of hydrostatic pressure (e.g. Piz Cengalo in 2017). Its presence has often been registered in major rock failures, but it has never been quantified. Perched water table >>20m above virtually impermeable permafrost bedrock can cause excessive hydrostatic stress on affected rockwalls. Climate change related intensification of rainstorms as well as permafrost degradation promote water accumulation. An increase in rockfall activity due to higher water pressure peaks is therefore expected, thus intensifying the risk for humans and infrastructures. Here we conduct a hydromechanical stability analysis at two study sites in the Northern Calcareous Alps where this effect has been observed. We use the distinct element method developed in the software UDEC (Itasca); the required geometric and mechanical model input parameters were obtained from previous studies with direct investigations and laboratory tests in frozen/unfrozen conditions. Infiltration from rainfall or snow/ice melting is expected to create extreme pressure peaks, especially when permafrost seals fractured rock. Here we present results from: the permafrost affected Zugspitze summit (Wetterstein Range), where sealing permafrost allows the meltwater to accumulate in the active layer. This causes high hydrostatic pressure, evaluated by relative gravimetry methods and with the help of a fracture mapping. a preparing high-magnitude rock fall at the Hochvogel (Allgäu Alps), where perched water could destabilize up to 260'000 m3. Displacement measurements on the summit showed acceleration following intense precipitation. Our model proves that a column of water can bring the Zugspitze north face to instable equilibrium. This happens with different intensities according to frozen/unfrozen conditions and various depth of the active layer, if the hydrostatic pressure is adequate (0.2-0.4 MPa = 20-40 m water column). Water could also increase the destabilization rates of the south-east face of Hochvogel by adding hydrostatic pressure. A Factor of Safety < 1 is reached when other water-related factors are considered, like: (i) reduction of cohesion in saturated joints, (ii) decrease of the interface friction angle in fractures and (iii) accelerates weathering along the shear plane [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14338

2020063016 Streletskiy, Dmitry (George Washington University, Washington, DC); Grebenets, Valery and Zamyatina, Nadezhda. Assessment of dangerous permafrost processes in urban settlements of the Russian Arctic [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10350, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Russian Arctic is characterized by developed infrastructure and high percentage of urban population on permafrost. The settlements on permafrost represent hot spots of permafrost transformations as rapidly changing climatic conditions are exacerbated by various types of human activities. To evaluate the exposure and risks of settlements to permafrost related dangerous processes, we selected several criteria, including geographic extent, duration, probability of occurrence, and total risk of damages associated with each permafrost process in 37 settlements located in various parts of the Russian Arctic. The following six types of potentially dangerous permafrost processes were considered: a) thermokarst, b) thermal erosion and thermal abrasion, c) frost heave, d) frost cracking, e) formation of icings, f) human-induced slope processes on permafrost. While risk from particular process was rather location specific, the integral assessment of all selected categories allowed to classify the overall exposure of settlements to permafrost processes. Results show that cities of Anadyr, Nadym and Kharp have rather small risk exposure, while cities of Igarka and Vorkuta have relatively high exposure. Bilibino and Norislk were among the cities having the highest overall exposure and potential risk associated with permafrost related processes considered in this study. The research is supported by Russian Foundation for Basic Research project 18-05-600888 "Urban Arctic resilience in the context of climate change and socio-economic transformations". [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10350

2020063074 Stünzi, Simone (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany); Kruse, Stefan; Boike, Julia; Herzschuh, Ulrike and Langer, Moritz. Coupling an individual-based boreal forest model with a permafrost land-surface model to forecast biomass development in boreal larch forests at the Siberian treeline [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14992, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The fate of boreal forests under global warming and forced rapid environmental changes is still highly uncertain, in terms of remaining a carbon sink or becoming a future carbon source. Forest dynamics and resulting ecosystem services are strongly interlinked in the vast permafrost-covered regions of the Siberian treeline ecotone. Consequently, understanding the role of current and future active layer dynamics is crucial for the prediction of aboveground biomass and thus carbon stock developments. We present a coupled model version combining CryoGrid, a sophisticated one-dimensional permafrost land surface model adapted for the use in forest ecosystems, with LAVESI, a detailed, individual-based and spatially explicit larch forest model. Subsequently, parameterizing against an extensive field data set of >100 forest inventories conducted along the treeline of larch-dominated boreal forests in Siberia (97-169° E), we run simulations covering the upcoming decades under contrasting climatic change scenarios. The model setup can reproduce the energy transfer and thermal regime in permafrost ground as well as the radiation budget, nitrogen and photosynthetic profiles, canopy turbulence and leaf fluxes and predict the expected establishment, die-off and treeline movements of larch forests. Our results will show vegetation and permafrost dynamics, quantify the magnitudes of different feedback processes between permafrost, vegetation, and climate and reveal their impact on carbon stocks in Northern Siberia. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14992

2020063065 Su, Zhongbo (University of Twente, Department of Water Resources, Twente, Netherlands); Yu, Lianyu; Wang, Yunfei and Zeng, Yijian. Impacts of enhanced soil water and heat dynamics on ecosystem functioning [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13774, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In the current Earth System Model (ESM), the soil water and heat transport in the land surface model (LSM) is not strongly coupled. As such, the discrepancy between the modelled land surface states and fluxes and the observed ones was mainly remedied by revising relevant simplified parameters, while the detailed physics (and/or physiography) was not necessarily consistent. While zooming in those studies over the cold region, the current ESMs do not consider the hydro-permafrost-carbon coupling. For example, the strong impact of soil moisture on spatial patterns of soil carbon stocks has been observed at sites, while the current ESMs cannot show this impact. On the other hand, soil moisture can affect the temperature sensitivity of decomposition rate and alter soil thermal dynamics significantly. To address the foregoing issues, it calls for an interdisciplinary approach to investigate soil-water-energy-plant interactions. Such approach is even more so desired for cold regions, where permafrost and seasonal frozen ground widely spread. This pressing need is mainly due to the carbon release from climate-induced permafrost thawing into the atmosphere, called as permafrost carbon feedback (PCF). It is also due to the tight coupling between hydrological processes and carbon dynamics, which, if ignored, will lead to the underestimation of global carbon turnover time by 36%. As a trial, this research coupled the detailed soil water and heat model with the biogeochemical model to investigate the mechanisms behind the impacts of enhanced soil water and heat dynamics on ecosystem functioning. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13774

2020062994 Tanski, George (Vrije Universiteit Amsterdam, Department of Geosciences, Amsterdam, Netherlands); Lantuit, Hugues; Wagner, Dirk; Knoblauch, Christian; Ruttor, Saskia; Radosavljevic, Boris; Wolter, Juliane; Fritz, Michael; Strauss, Jens; Irrgang, Anna M.; Ramage, Justine; Sachs, Torsten and Vonk, Jorien E. Retrogressive thaw slumps along permafrost coasts transform organic matter before release into the Arctic Ocean [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8806, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Changing environmental conditions in the Arctic have profound impacts on permafrost coasts, which erode at great pace. Although numbers exist on annual carbon and sediment fluxes from coastal erosion, little is known on how terrestrial organic matter (OM) is transformed by thermokarst and -erosional processes on transit from land to sea. Here, we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island in the western Canadian Arctic. The RTS was classified into an undisturbed, disturbed and nearshore zone and systematically sampled along transects. Collected sediments were analyzed for organic carbon (OC), nitrogen (N), stable carbon isotopes (d13C-OC) and ammonium. C/N-ratios, d13C-signatures and ammonium concentrations were used as general indicator for OM degradation. Permafrost sediments from the RTS headwall and mud lobe sediments from the thaw stream outlet were incubated to further assess OM degradation and potential greenhouse gas formation during slumping and upon release into the nearshore zone. Our results show that OM concentrations significantly decrease upon slumping in the disturbed zone with OC and N decreasing by >70% and >50%, respectively. Whereas d13C-signatures remain fairly stable, C/N-ratios decrease significantly and ammonium concentrations increase slightly in fresh slumping material. Nearshore sediments have low OM contents and a terrestrial signature comparable to disturbed sites on land. The incubations show that carbon dioxide (CO2) forms quickly from thawing permafrost deposits and mud debris with ~2-3 mg CO2 per gram dry weight being cumulatively produced within two months. We suggest that the initial strong decrease in OM concentration after slumping is caused by a combination of OC degradation, dilution with melted massive ice and immediate offshore transport via the thaw stream. After stabilization in the slump floor, recolonizing vegetation takes up N from the disturbed sediment. Upon release into the nearshore zone, larger portions of OM are directly deposited in marine sediments, where they further degrade or being buried. The incubations indicate that CO2 is rapidly produced upon slumping and potentially continues to form within the nearshore zone that receives eroded material. We conclude that coastal RTS systems profoundly change the characteristic of modern and ancient permafrost terrestrial OM during transit from land to sea - a process which is likely linked to the production of greenhouse gases. Our study provides valuable information on the potential fate of terrestrial OM along eroding permafrost coasts under the trajectory of a warming Arctic. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8806

2020063103 Tarbier, Brittany (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Jonsson, Sofi; Baptista-Salazar, Carluvy; Sannel, A. Britta K. and Hugelius, Gustaf. Permafrost thaw increases methylmercury formation in sub-arctic Fennoscandia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18536, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

With ongoing climate change, temperatures in the northern latitudes are increasing more than twice as fast as the global mean. This causes thawing of permafrost and the release of carbon and contaminants, including mercury (Hg), which have thus far been immobilized in the frozen soil. The potential release of Hg, and microbial transformation of mobilized inorganic Hg to monomethylmercury (MeHg), presents a risk to ecosystems and human health. MeHg is a neurotoxic substance that is readily taken up and biomagnified in aquatic food webs to dangerous concentrations. Arctic communities are particularly vulnerable to Hg pollution as a result of a diet that often includes high trophic level fish and marine mammals. Despite the ecological and societal consequences of elevated Hg levels and the potential for increased Hg conversion to MeHg in post-thaw wetland environments, much of the Hg cycle in the high North is poorly understood. While global and northern latitude Hg budgets have been estimated, the effect of permafrost thaw on MeHg formation has not yet been fully investigated. Here, we compared concentrations of total Hg (HgT) and MeHg in intact permafrost samples from palsas and peat plateaus with samples from recently thawed collapse fens and from peatlands unaffected by permafrost dynamics in order to investigate whether permafrost thaw impacts net MeHg formation in peatlands. Our study includes five subarctic permafrost peatland sites located in northern Sweden and Norway. Concentrations of HgT and MeHg in the soil cores ranges from 1.1 to 210 and 0.005 to 28 ng g-1 dry weight, respectively, with higher concentrations in the upper soil horizons. No differences were observed in average HgT and MeHg concentrations between the five sites, including both coastal and inland locations. Interestingly, we observe higher concentrations of MeHg and MeHg:HgT ratios in the collapse fens as compared to the permafrost cores, showing increased net methylation of Hg upon permafrost thaw. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18536

2020063036 Tran, Tuong Vi (Leibniz Universität Hannover, Institute of Fluid Mechanics and Environmental Physics, Hanover, Germany); Buckel, Johannes; Maurischat, Philipp; Tang Handuo; Yu Zhengliang; Graf, Thomas; Hördt, Andreas; Zhang Fan; Guggenberger, Georg and Schwalb, Antje. Aquifer parameter estimation for the Zhagu Subcatchment (Tibetan Plateau) based on geophysical methods [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-11854, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The aquifers on the Tibetan Plateau (TP) constitute as origin for major river systems, which are supplying millions of people all over Asia. Increasing population and tourism activities leading to larger water consumption. Hence, water supply is getting increasingly important. The TP is a sensitive system and is noticeable reacting climate change. Past decades are marked with, increasing trends of precipitation, melting of glaciers and degradation of permafrost and have generally lead to rising water levels in lakes on the TP. To ensure future water supply, aquifer characterisation and future prognosis on groundwater behavior are therefore necessary. However, due to the remote character of the TP, knowledge according to hydrogeological parameter is scarce. The aim of this study is therefore to estimate a range for aquifer parameter based on geophysical methods. The Zhagu basin, situated in the Nam Co Lake basin (second largest lake on the TP), is used as a case study. This project is part of the International Research Training Group "Geoecosystems in transition on the Tibetan Plateau" (TransTiP), funded by the DFG. During several field work campaign in July 2018, May 2019 and September 2019 disturbed sediment samples were taken and were analyzed for grain size distribution. Selected sediment layer in the laboratory were tested. Outcome of this analysis is the porosity for each selected sediment layer. Another measurement during field work has been conducted, namely electrical resistivity tomography measurements (ERT). To get better approximation of porosity and sediment characteristics, Archie's Law is used as model to estimate those properties and later on to compare it to field and laboratory results. Two approaches are implemented (i) calculates the bulk resistivity based on known porosity from the laboratory and known conductivity of pore water measured during field work (ii) calculates the porosity with known conductivity of pore water and the bulk conductivity. For analysis saturated sediment layers were chosen. The investigation shows that both approaches are largely applicable and leading to almost same results and trends of each sediment layer. The best percentage deviation of the modeled bulk resistivity results to the measurement in the field could be achieved by position D11 which is situated near the Nam Co Lake showing a deviation of around 7%. Inside the catchment the percentage deviation is largely increasing. However, the application of Archie's Law in combination with field and laboratory measurements allows to construct a porosity ranges for future groundwater flow calibration. In addition, the results emphasising the zonation of the subsurface in (un)saturated zones due to the small amount of resistivity. Sediment profiles, ERT measurements, observations, interpretation and conclusion including the comparison of simulated resistivity and simulated porosity to field resistivity and porosity based on laboratory analysis will be shown and discussed in the contribution. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-11854

2020063146 Turetsky, Merritt (University of Colorado Boulder, Institute of Arctic and Alpine Research, Boulder, CO); Gibson, Carolyn and Dieleman, Catherine. Impacts of thermokarst on permafrost carbon losses and ecosystem services [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-22219, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost thaw is altering northern ecosystems and the services they provide at scales ranging from local subsidence to global climate feedbacks. In organic-rich peatlands, thermokarst initiation and spread rates are increasing with rising mean annual air temperatures, changes in wildfire, and human land use. This presentation will outline empirical and modeling approaches to better understand the consequences of thermokarst in peatlands as well as other types of northern terrains on carbon cycling, wildlife, and other aspects of ecosystem services. We are using fine scale datasets and remote sensing to map thermokarst coverage and expansion in both the Northwest Territories, Canada and interior Alaska. Using chronosequences and regional gradients, we are studying thermokarst impacts along gradients of time-since-thaw. Through a Permafrost Carbon Network synthesis, we developed conceptual and numerical models to understand how thermokarst development (formation, stabilization, re-accumulation of permafrost in some conditions) affects carbon storage and release. We are using a combination of empirical and modelled data to test hypotheses about climatic, ecological, and Quaternary controls on thermokarst rates and subsequent impacts on ecosystem services. We demonstrate that thermokarst in peat-rich landscapes are hotspots for permafrost carbon release primarily through methane emissions, have the potential to impact hunter movement and safety, and affect caribou habitat quality. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-22219

2020063073 Van Delden, Lona (University of Eastern Finland, Kuopio, Finland); Marushchak, Maija; Voigt, Carolina; Grosse, Guido; Faguet, Alexey; Lashchinskiy, Nikolay; Kerttula, Johanna and Biasi, Christina. Towards the first circumarctic N2O budget; extrapolating to the landscape scale [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14347, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is warming at twice the rate of the rest of the globe. While it has been increasingly highlighted that thawing permafrost accelerates soil organic matter decomposition, research on biogeochemical N cycling is still underrepresented. Arctic nitrous oxide (N2O) emissions have long been assumed to have a negligible climatic impact but recently increasing evidence has emerged of N2O hotspots in the Arctic. Even in small amounts, N2O has the potential to contribute to climate change due to it being nearly 300 times more potent at radiative forcing than CO2. Therefore, the "NOCA" project aims to establish the first circumarctic N2O budget. Following intensive N2O flux sampling campaigns at primary sites within Northern Russia and soil N2O concentration measurements from secondary sites across the Arctic, we are now entering the phase of spatial extrapolation. Challenges to overcome are the small-scale heterogeneity of the landscape and incorporating small features that can function as N2O hotspots. Therefore, as a first step in upscaling the N2O fluxes, high resolution imagery is needed. We show here novel high-resolution 3D imagery from an unmanned aerial vehicle (UAV), which will be used to upscale N2O fluxes from plot to landscape scale by linking ground-truth N2O measurements to vegetation maps. This approach will first be applied to the East cliff of Kurungnakh Island in the Lena River Delta of North Siberia and is based on 2019 sampling campaign data. Kurungnakh Island is characterized by ice- and organic-rich Yedoma permafrost that is thawed by fluvial thermo-erosion forming retrogressive thaw slumps in various stages of activity. Overall, 20 sites were sampled along the cliff and inland, covering the significant topographic and vegetative characteristics of the landscape. The data from this scale will provide the basis for extrapolating, by using a stepwise upscaling approach, to the regional and finally circumarctic scale, allowing a first rough estimate of the current climate impact of N2O emissions from permafrost affected soils. Available international circumarctic data from this and past projects will be synthesized with an Arctic N2O database under development for use in future ecosystem and process-based climate model simulations. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14347

2020063104 Vasilevich, Roman (Russian Academy of Science, Institute of Biology, Syktyvkar, Russian Federation). Assessment of the trace element composition of peat soils from the European Arctic in a changing climate conditions [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18613, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The trace element composition of stratified peat soils is interesting for the reconstruction of the geochemical background of atmospheric aerosol. The monitoring of trace element contents in peat deposits is often used for the identification of pollution around large industrial centers. The destabilization of the peatlands of the cryolithozone presents a global environmental hazard of the input of inorganic pollutants into the hydrologic network and their subsequent transport into the Arctic Ocean. Climate warming and permafrost degradation enhance the influence of deep peat layers on the trace element composition of groundwater and rivers. The purpose of the work is to assess the accumulation of trace elements in peat soils as a result of the aerogenic pollution of the territory and to identify their internal profile migration and accumulative characteristics. The peatlands investigated are in the far north taiga (Northeastern European Russia, 65°54'N, 60°26'E), ecoton south tundra - forest-tundra (67°03'N, 62°56'E) and ecoton north tundra - south tundra (68°02'N, 62°43'E). The upper level of trace element accumulation was confined to the active (seasonally thawed) layer owing to airborne contamination over a long time span and related to the bioaccumulation of Hg, Cd, Pb, Cu, and other heavy metals (HMs) by plants and humus materials. The character of element accumulation and migration in the active layer is controlled by the stability of HM humates. Under high-acidity conditions, HMs are highly mobile and migrate to the lower boundary of the active layer, which is indicated by an increase in the fraction of water-soluble forms of a number of elements. Analysis with a scanning electron microscope revealed the presence of spherical and semispherical particles up to 1 mm in size containing Pb, Zn, Cr, and Ni in the upper peat levels, which indicates an anthropogenic source of their input owing to long-distance and local transport of air masses. The central level of element accumulation was confined to peat layers in the permafrost zone (60-120 cm), where enrichment in As and Cd relative to the mean contents in the Earth's crust (and approximate permissible concentrations, APC, for soils) and accumulation of Fe, Al, S, and siderophile elements were observed. The source rocks of the peatlands are loams enriched in Cd, Zn, and As. The statistical analysis of relations of the contents of major and trace elements in the stratified peat horizons with the composition of peat-forming materials showed a significant contribution of the biogenic accumulation of elements. The reported study was funded by the RFBR No 18-05-60195 (No AAAA-A18-118062090029-0). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18613

2020063120 Voigt, Carolina (University of Montreal, Montreal, QC, Canada); Gosselin, Gabriel Hould; Black, Andrew; Chevrier-Dion, Charles; Marquis, Charlotte; Nesic, Zoran; Saarela, Taija; Wilcox, Evan; Marsh, Philip and Sonnentag, Oliver. Towards resolving spatial and temporal greenhouse gas dynamics across a heterogeneous Arctic tundra landscape in the Western Canadian Arctic [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-19864, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is currently warming faster than the rest of the world. Warming and associated permafrost thaw in Arctic landscapes may mobilize large pools of carbon (C) and nitrogen (N) and ultimately increase the atmospheric burden of the greenhouse gases (GHGs) carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Arctic GHG dynamics and their environmental and hydrological controls are poorly understood. Whether Arctic landscapes act as a net GHG source or sink depends on the complex and spatially varying interactions between hydrology, active layer thickness, topography, temperature, vegetation, substrate availability and microbial dynamics. Our study site, Trail Valley Creek (68°44'N, 133°29'W), is an upland tundra site characterized by small-scale (<10 m) land cover and soil type (mineral and organic) heterogeneity consisting of different land cover types: shrub, tussock and lichen patches, polygonal tundra and thermokarst-affected areas, wetlands, lakes, and streams. To understand the large spatial and temporal variability of GHG dynamics across these terrestrial and aquatic landcover types we use a nested observational approach at plot- (<1 m2), ecosystem- (~10 m2), landscape- (~100 m2) and regional (~50 km2) scale. Existing (since 2013) ecosystem-scale eddy covariance (EC) measurements of net CO2 and CH4 exchanges are complemented with landscape-scale EC measurements and plot-scale automated and manual chamber measurements within the EC tower footprint and beyond. To increase process-based understanding we complement these multi-scale GHG flux observations with a wide array of auxiliary measurements including soil profile dynamics of CO2, CH4, N2O, and oxygen, lake and soil pore nutrient concentrations, soil temperature and moisture profiles, thaw depth, leaf area index (LAI), normalized difference vegetation index (NDVI), lake catchment characteristics, and quality and microbial degradability of aquatic dissolved organic matter. Preliminary results from manual chamber measurements show that tussocks were the largest net CO2 sink during the growing season. While the majority of terrestrial landcover types showed small but consistent and seasonally varying CH4 uptake, lake shore and thermokarst-affected areas displayed high nutrient loads and were hotspots of CH4 emissions. Therefore, capturing the landscape heterogeneity, areal coverage and hydrological connectivity of terrestrial and aquatic landcover types is important and our study highlights the need to combine belowground, plot-, ecosystem- and landscape-scale measurements to understand biosphere-atmosphere interactions in the Arctic. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-19864

2020063102 Wan Chengwei (Hohai University, Hydrology and Water Resources, China) and Zhou Zhou. Isotopic constraints on water balance of tundra lakes and watersheds affected by permafrost degradation, Mackenzie Delta region, Northwest Territories, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18415, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Widespread permafrost thaw in Canada's western Arctic has led to formation of shoreline retrogressive thaw slumps (SRTS), a process influential in modifying water and biogeochemical balances of tundra lakes. To investigate hydrological effects of SRTS, water sampling campaigns were conducted in 2004, 2005 and 2008 for paired lakes (pristine vs catchments disturbed by SRTS) in the upland region adjacent to the Mackenzie Delta, Northwest Territories, Canada. An isotope balance model to estimate evaporation/inflow, precipitation/inflow, water yield and runoff ratio was developed incorporating seasonal evaporative drawdown effects and a vapour mixing model to simulate gradients in Beaufort Sea marine air versus continental moisture sources. Site-specific water balance results reveal systematically higher evaporation/inflow and precipitation/inflow for lakes with active SRTS compared to undisturbed lakes, and typically higher ratios for lakes with stabilized versus active SRTS. For lake catchments, water yield is found to be higher for active SRTS sites compared to undisturbed and stabilized SRTS sites, suggesting that slumping is an initial but not a sustained source of water delivery to lakes. Catchments with history of wildfire are found to have lower water yields, attributed to reduced permafrost influence. Conceptually, we define a thaw trajectory whereby undisturbed sites, active SRTS, stabilized SRTS, and ancient-SRTS define progressive stages of permafrost thaw. We postulate that release of additional runoff is mainly due to permafrost thaw in active SRTS which also promotes lake expansion, talik formation, and subsurface connectivity. Eventual stabilization of slumps and reduced runoff is expected once permafrost thaw sources are exhausted, at which time lakes may become more reliant on replenishment by direct precipitation. The effect of snow catch in slumps appears to be subordinate to thawing based on eventual decline in runoff once thaw slumps stabilize. Improved, site-specific hydrologic understanding will assist ongoing research into carbon cycling and biogeochemical feedbacks. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18415

2020063067 Wang Lingxiao (Nanjing University of Information Science and Technology, Department of Geographic Information Science, Nanjing, China); Zhao Lin; Zhou Huayun; Liu Shibo; Huang Xiaodong and Wang Chong. Monitoring permafrost changes in the Yangtze River source region of the Qinghai-Tibetan Plateau using differential SAR interferometry [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-13906, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Qinghai-Tibet Plateau (QTP) has the largest high-altitude permafrost zone in the middle and low latitudes. Substantial hydrologic changes have been observed in the Yangtze River source region and adjacent areas in the early 21st century. Permafrost on the QTP has undergone degradation under global warming. The ground leveling observation site near Tangula (33°04'N, 91°56'E) located in the degraded alpine meadow indicates that the ground has subsided 50mm since 2011. The contribution of permafrost degradation and loss of ground ice to the hydrologic changes is however still lacking. This study monitors the permafrost changes by applying the Small BAseline Subset InSAR (SBAS-InSAR) technique using C-band Sentinel-1 datasets during 2014-2019. The ground deformation over permafrost terrain is derived in spatial and temporal scale, which reflects the seasonal freeze-thaw cycle in the active layer and long-term thawing of ground ice beneath the active layer. Results show the seasonal thaw displacement exhibits a strong correlation with surficial geology contacts. The ground leveling data is used to validate the ground deformation monitoring results. Then, the ground deformation characteristics are analyzed against the landscape units. Last, the long-term inter-annual displacement value is used to estimate the water equivalent of ground ice melting. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-13906

2020063044 Wang Shiping (Chinese Academy of Sciences, Institute of Tibetan Plateau, China); Wang Qi; Lv Wangwang; Zhou Yang and Jiang Lili. Asynchrony of winter soil freeze-thaw phenology induced by warming reduces ecosystem respiration of alpine meadow during the freeze-thaw period [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-12031, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Changes in winter soil freeze-thaw (F-T) phenology not only affect nature, but also affect social-economy in permafrost regions. However, a lack of understanding of its response to global warming is a critical gap in knowledge to preclude adaptation to climate change. Here we explored effects of warming gradient (0, 1, 2 and 4°C) combined with precipitation addition on it by which further on CO2 emission on the Tibetan Plateau. We find that only warming delays start and end dates of soil F-T cycle during autumn-winter season, but advances them during winter-spring season, thus shortens the durations of completely freezing (14.9 days °C-1) and total duration of soil F-T period from autumn to spring (11.7 days °C-1). Thus, asynchronic shifts of the soil F-T cycle induced by warming significantly decreased total CO2 emission by 31-47% relative to T0 treatment during the whole F-T period from autumn to spring. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-12031

2020063100 Wee, Julie (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Delaloye, Reynald and Barboux, Chloé Post-glacial dynamics of alpine Little Ice Age glacitectonized frozen landforms (Swiss Alps) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-18360, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Glaciers and frozen debris landforms have coexisted and episodically interacted throughout the Holocene, the former having altered the development, spatial distribution and thermal regime of the latter. In the Alps, the apogee of last interaction phase occurred during the Little Ice Age (LIA). Since then, due to glacier shrinkage, interactions between glaciers and LIA pre-existing frozen debris have gradually diminished and are leaning towards being non-existent. Post-LIA glacier forefields in permafrost environments, including associated glacitectonized frozen landforms (GFL) have shifted from a thermal and mechanical glacier dominant regime towards a periglacial or even post-periglacial regime. GFL are undergoing thermal and mechanical readjustments in response to both the longer-term glacier recession and the more recent drastic climatic warming. They can be expressed by a combination of mass-wasting processes and thaw-induced subsidence. In various regions of the Swiss Alps, slope movements occurring in a periglacial context have been inventoried in previous works using differential SAR interferometry (DInSAR) (Barboux et al., 2014). In the scope of this study, and focusing solely on mass-wasting GFL, the former inventory allowed the identification of the latter under various spatial configurations within LIA glacier forefields. While most observed GFL are disconnected from the associated glacier, some are still connected. Additionally, ground ice occurs as interstitial or massive (buried) glacier ice. This potentially infers the ongoing of non-uniform morphodynamical readjustments. To understand the site-specific behaviour of GFL, the analysis of long-term time-series of permafrost monitoring and multi-temporal high-resolution Digital Elevation Models will allow the assessment of the recent evolution of the Aget and Ritord/Challand LIA glacier forefields (46°00'32"N, 7°14'20"E and 45°57'10"N, 7°14'52"E, respectively) and their associated GFL (i.e. push-moraines). Both glacier forefields present a contrasting spatial configuration, making their morphodynamical evolution to differ partly from one another. The Aget push-moraine is a back-creeping GFL, which has been disconnected from the Aget glacier since the 1940s at latest. For the last two decades, surface displacement velocities have decelerated in comparison to the accelerating regional trend (PERMOS, 2019). Additionally, a 30% decrease of the electrical resistivity of the frozen ground, combined with locally observed thaw-induced subsidence of up to 10 cm/year suggest an advanced permafrost degradation. The Ritord/Challand system presents a push-moraine disconnected from its glacier as well as several push-moraines connected to a still existing debris-covered glacier. Between 2016 and 2019, surface lowering up to 10 m attesting massive ice melt has been locally detected in the former where buried glacier ice was visually observed. Whereas in the latter, subtle surface displacements ranging from 10 to 30 cm/year occur. This confirms the heterogeneity of the morphodynamical processes occurring in GFL, expressed as a function of both their spatial configuration and ground ice properties. Barboux, C., Delaloye R. and Lambiel, C. (2014). Inventorying slope movements in an Alpine environment using DInSAR. Earth Surface Processes and Landforms, 39/15, 2087-2099. PERMOS 2019. Permafrost in Switzerland 2014/2015 to 2017/2018. Noetzli, J., Pellet, C., and Staub, B. (eds.), Glaciological Report (Permafrost) No. 16-19 of the Cryospheric Commission of the Swiss Academy of Sciences, 104. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-18360

2020063013 Westermann, Sebastian (University of Oslo, Department of Geosciences, Oslo, Norway); Martin, Leo; Nitzbon, Jan; Aas, Kjetil; Scheer, Johanna; Eiken, Trond and Etzelmüller, Bernd. Measuring and modelling thermal erosion patterns of peat plateaus in Northern Norway [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10183, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Peat plateaus are a major type of permafrost landscape in Arctic and Siberian lowlands. They represent a substantial pool of several hundreds of petagrams of organic carbon that has the potential to contribute to the Permafrost Carbon Feedback. The thermal response of these soils to the climate signal is complex and implies the interaction of various surface and subsurface processes operating at a very small spatial scale involving water, snow and heat fluxes and surface subsidence. As these processes have the ability to generate feedbacks between each other and trigger non-linear evolutions of the landscape, they challenge our abilities to measure and model them. Peat plateaus in Northern Norway have been actively degrading over at least the last 60 years. They thus offer a precious opportunity to measure and model the degradation patterns they exhibit. We present new topographical observations derived from drone-based photogrammetry that we acquired for one site in Northern Norway. Over a period of 3 years, these Digital Elevation Models allows quantifying precisely the surface subsidence and resulting lateral degradation of the peat plateaus. In a second time, we use the land surface model CryoGrid to model the observed patterns. The model is able to (i) simulate the snow fluxes and the water and heat sub-surface fluxes within the plateau and between the plateau and the surrounding wet mire and to (ii) represent the soil surface subsidence due to excess ice melt in the soil. We implement a set up that discretize the interface between the peat plateaus and the wet mire and force the Surface Energy Balance module of the model with climatic data derived from regional atmospheric modelling. Our simulations manage to reproduce the degradation speed we observe in our topographical data. We also present a sensitivity analysis of the degradation speed to snow cover and to the geometry of the peat plateaus and show how the feedbacks between the dynamical topography and the lateral fluxes of snow and water can trigger rapid permafrost thawing and fast degradation of permafrost landscapes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10183

2020063069 Wieczorek, Mareike (Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Polar Terrestrial Environmental Systems, Potsdam, Germany); Heim, Birgit; Böhmer, Thomas; Gebhardt, Nadine; Bartsch, Annett and Herzschuh, Ulrike. Challenges in creating and exemplary applications of two cross-repository data compilations on sedimentary pollen and permafrost soil temperature [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-14019, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Large scale analyses of climatic or ecological data are important to understand complex relationships. Often, such data are available in open repositories or national measurement programmes, others are only made available via the responsible researcher. However, merging data from various sources is often not straightforward, due to issues with the data itself or the metadata. Nevertheless, the application of such compilations offers various possibilities. In our working group, two large-scale compilations are currently constructed and applied. The Northern Hemispheric Pollen Compilation consists of data from NEOTOMA, European Pollen Database (EPD), PANGAEA and various authors. With the help of this compilation, we reconstruct climate and vegetation of large spatial and temporal scales. The circumpolar soil temperature dataset consist of data from the Global Terrestrial Network for Permafrost (GTN-P), Roshydromet, PANGAEA, Nordicana D and the National Science Foundation (NSF) Arctic Data Center. In its first version, the compilation has already been successfully applied to validate the ESA CCI Permafrost soil temperature map. The various sources of errors and problems will be shown by the two compilations of (i) sedimentary pollen data and (ii) soil temperature data. The most general problem and error source are wrong or inaccurate coordinates. These errors arise out of coordinates provided with two decimals only, wrong conversion of DMS to decimal format, wrong coordinates etc. For most analyses, the most exact geographic position is a prerequisite, as e.g. lake size is an important parameter when reconstructing vegetation out of sedimentary pollen data. Sedimentary pollen records not located in a lake according to their given location thus need manual reposition according to the main researcher of a dataset or satellite maps. Further challenges concerning the pollen dataset pose various naming conventions or variable resolution in time. Furthermore, taxonomic resolution varies between datasets, making homogenization necessary. But also for the soil temperature dataset, extensive checks were necessary, as even quality checked data comprise erroneous values. Furthermore, measured depths vary between datasets. For easy comparisons of soil temperature simulations against data, standardized depths were extracted. In a future step, interpolations between measured depths will help the end-users to extract the exactly needed depths and a compilation of available metadata on e.g. surrounding vegetation and borehole stratigraphy shall be provided. All compilations will be made available on public repositories. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-14019

2020063005 Wilcox, Evan J. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Walker, Branden; Hould-Gosselin, Gabriel; Sonnentag, Oliver; Wolfe, Brent B. and Marsh, Philip. Landscape controls on the hydrological variability of thermokarst lakes between Inuvik and Tuktoyaktuk, NWT [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-9279, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is warming at twice the rate of the rest of the world, causing precipitation to shift from snowfall to rainfall, permafrost to thaw, longer snow-free land and ice-free lakes, and increased evaporation. Thermokarst lakes across the Arctic have experienced different changes over the past decades: in some regions, lakes are expanding through thawing adjacent permafrost, while in other regions they are drying up and shrinking, or not changing at all. It is important to understand what governs lake water balance as it affects lake ecosystems that support large populations of migratory birds and fish; are important to local communities for food and recreation; and control the flux of carbon and other nutrients from thawing permafrost into lakes. For example, lake inflow, evaporation and water residence time affect the concentration of nutrients within lakes, ultimately affecting the aquatic ecosystem and greenhouse gas release. Previous research has focused on quantifying the water inputs and outputs of individual lakes, but a better understanding of the drivers and processes controlling lake water balances is required to understand how they will respond to a changing climate. We measured lake water flux components at multiple spatial and temporal scales across the 5000 km2 boreal - tundra transition zone between Inuvik and Tuktoyaktuk, Northwest Territories, Canada. Lake water flux components were measured at two adjacent thermokarst lakes with different ratios of lake area to catchment area (LACA), from 2017-2019. Also, water isotope samples were collected from March - September 2018 from ~100 lakes across 2000 km2. From these water isotope compositions we estimated the ratio of evaporation to inflow, residence time, and the mixture of snowmelt and rainfall runoff in each lake. Catchments of all 7500 lakes in the region were delineated using a high-resolution digital elevation model in order to estimate their LACA, and evaluate connectivity between lakes. Paired lake water balance measurements showed that the lake with a larger LACA had a residence time an order of magnitude shorter than the larger lake, and displayed larger fluctuations in water level. Also, the ratio of evaporation to inflow was significantly larger in lakes with smaller LACA. Water isotope compositions showed that only 10-50% of a lake's water is replaced by snowmelt in spring, as the majority of snowmelt runoff flowed overtop of lake ice and through the lake outlet. Deeper lakes had significantly less snowmelt mixing, as the volume of water for the snowmelt to mix with was greater than in shallower lakes. These results show that lake water balance can be characterized using lake and catchment properties, allowing future research to more easily characterize lake hydrology and build further understanding about how lake water balance is connected to other aspects of the permafrost environment. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-9279

2020063094 Wild, Birgit (Stockholm University, Department of Environmental Science, Stockholm, Sweden); Shakhova, Natalia; Dudarev, Oleg; Ruban, Alexey; Kosmach, Denis; Tumskoy, Vladimir; Tesi, Tommaso; Joss, Hanna; Alexanderson, Helena; Jakobsson, Martin; Mazurov, Alexey; Semiletov, Igor and Gustafsson, Orjan. Vulnerability of subsea permafrost organic matter to degradation after thaw [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-17935, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Subsea permafrost contains a potentially large and vulnerable organic carbon pool that might be or become a source of greenhouse gases to the atmosphere. While organic carbon stocks and vulnerability of terrestrial permafrost are increasingly well constrained, the dynamics of subsea permafrost remain highly uncertain due to limited observational data from these hard-to-access systems. Based on a unique set of drill cores from the near-coastal Laptev Sea, we here assess the vulnerability of subsea permafrost organic matter to degradation after thaw. To that end, we combine biomarker analyses of organic matter above and below the in-situ thaw front with incubation of subsea permafrost material in the laboratory. Biomarker degradation proxies based on the lignin phenol composition of organic matter (acid/aldehyde ratios of syringyl and vanillyl phenols; 3,5-dihydroxybenzoic acid/vanillyl ratio) suggest an overall low degradation state of lignin compared to terrestrial permafrost deposits and marine sediments in the region, and no systematic change across the thaw front. These lignin-based proxies are mostly sensitive to degradation under oxic conditions, i.e. before organic matter burial in subsea permafrost deposits, and less to degradation under anoxic conditions that prevail at the thaw front of subsea permafrost. Lignin phenol proxies will therefore be complemented by other biomarker degradation proxies sensitive to degradation under anoxic conditions, as well as by first data from incubation of subsea permafrost material under cold, anoxic conditions. Together, these data will enhance our understanding of organic matter in subsea permafrost, its vulnerability to degradation after thaw and the potential for greenhouse gas emissions from this system. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-17935

2020062991 Wilkenskjeld, Stiig (Max Planck Institute for Meteorology, Hamburg, Germany); Overduin, Paul; Miesner, Frederieke; Puglini, Matteo and Brovkin, Victor. Integrating subsea permafrost into an Earth system model (MPI-ESM) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8473, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Subsea permafrost on the Arctic Shelf originates as terrestrial permafrost which was submerged by ocean water following sea level rise during deglaciation. The thickness and depth of subsea permafrost are not well known on the circumpolar scale. Subsea frozen sediments contain organic carbon as well as preventing the upward diffusion of carbon-containing greenhouse gases. Thawing of subsea permafrost - which may accelerate as a consequence of global warming - makes this carbon available for release to the ocean-atmosphere system and thus constitutes a positive feedback to global warming. Present estimates of the carbon associated with subsea permafrost range over two orders of magnitude and are thus highly uncertain and the amount of stored organic carbon potentially huge. Due to the long time scales involved in thawing permafrost, subsea permafrost may become - especially in a future with low anthropogenic carbon emissions - a significant contributor to global carbon releases and thus to an enhanced global warming. The best tool for estimating the effects of future carbon releases are the Earth System Models (ESMs) which, however, are - due to their computational demands - not well suited for the long time scale of build-up and degradation of subsea permafrost. We therefore apply a novel two-model approach. The multiple glacial-cycle model Submarine Permafrost Map (SuPerMap) was used to obtain the pre-industrial distribution of permafrost based on 1D modelling of heat flow driven by glacial, marine and aerial surface upper boundary conditions. This state was then used to initialize JSBACH, the land surface component of the MPI Earth System Model (MPI-ESM), which was extended to allow subsea permafrost applications. JSBACH was used to generate present-day and near-future permafrost thaw by applying historical and future scenario forcings from the MPI-ESM runs performed within the Coupled Model Intercomparison Project, CMIP6. As a first step we here present the modelled physical state (temperature and ice content profiles) of the subsea sediments on the Arctic Shelf in the pre-industrial and present states as well as in the near future. SuPerMap generated a region of cryotic (<0°C) sediment on the Arctic Shelf of 2.5 million km2, more than 80% of which lay north of Eastern Siberia. In the JSBACH simulations, permafrost thawing rates accelerate after the mid-20th century. From about 2060 onwards, the choice of shared social-economic pathway (SSP) determines the rate of thaw and up to about 1/3 of the pre-industrial cryotic area is lost before year 2100. Regional aspects of the SSP projections will be presented. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8473

2020063078 Wittig, Sophie (Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France); Berchet, Antoine; Paris, Jean-Daniel; Arshinov, Mikhail; Machida, Toshinobu; Sasakawa, Motoki; Worthy, Doug and Pison, Isabelle. Assessment of CH4 sources in the Arctic using regional atmospheric measurements and their link to surface emissions [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-16584, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is a critical area in terms of global warming. Not only are the rising temperatures already causing changes in the natural conditions of this region, but the high potential of increased methane (CH4) regional emissions are also likely to intensify global warming even stronger in the near term. This future effect consists in the thawing and destabilization of inland and sub-sea permafrost that enhance the release of methane into the atmosphere from extensive CH4 and organic carbon pools which have so far been shielded by ice and frozen soil. Moreover, the high latitude regions are already playing a key role in the global CH4-budget because of such large sources as wetlands and freshwater lakes in addition to human activities, predominantly the fossil fuel industry of the Arctic nations. However, the level of scientific understanding of the actual contribution of Arctic methane emissions to the global CH4-budget is still relatively immature. Besides the difficulties in carrying out measurements in such remote areas, this is due to a high inhomogeneity in the spatial distribution of methane sources and sinks as well as to ongoing changes in hydrology, vegetation and carbon decomposition. Therefore, the aim of this work is to reduce the uncertainties about methane sources and sinks in the Arctic region during the most recent years by using an atmospheric approach, in order to improve the quality of the assessment of the local and global impacts. To do so, the data of atmospheric CH4 concentrations measured at about 30 stations located in different Arctic nations have been analysed in regard to the trends, seasonal fluctuations and spatial patterns that they demonstrate as well as their link to regional emissions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-16584

2020063023 Zangrando, Roberta (National Research Council of Italy, Institute of Polar Sciences, Italy); Hidalgo, Maria del Carmen Villoslada; Turetta, Clara; Cannone, Nicoletta; Malfasi, Francesco and Onofri, Silvano. Characterization of soil organic matter along an elevation gradient at Stelvio Pass (Italian Alps) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-10750, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Climate Change (CC) has evident impacts on the biotic and abiotic components of ecosystems. Soil is the third largest reservoir of carbon, next to the lithosphere and the oceans, and stores approximately 1500 Gt in the top 1 m depth. Even small changes in soil C stocks could have a vast impact on atmospheric CO2 concentration. Elevated surface temperature can substantially affect global C budgets and produce positive or negative feedbacks to climate change. Therefore, understanding the response of soil organic carbon (SOC) stocks to warming is of critical importance to evaluate the feedbacks between terrestrial C cycle and climate change. In comparison to other ecosystems, the areas at high altitudes and latitudes are the most vulnerable. In permafrost areas of the Northern Hemisphere the CC has already determined an increase in greenhouse gas emissions, shrub vegetation and variation in the composition of microbial communities. While numerous studies have been performed in Arctic, much less numerous are available for high altitude areas. These areas are a quarter of the emerged lands and have suffered strong impacts from the CC. Mountain permafrost makes up 14% of global permafrost, stores large quantities of organic carbon (SOC), and can release large quantities of CO2 due to climate change. However, permafrost contribution to the IPCC global budget has not yet been correctly quantified, in particular for ecosystems of prairie and shrubland, which alone could incorporate over 80Pg of C between soil and biomass. In the last decades, the plant component has undergone migration of species to higher altitudes, expansion of shrubs, variations in floristic composition and dominance, variations in area distribution. The expansion of the shrubs accelerates the regression of alpine meadows and snow valleys. The sampling activities have been carried out in July and September, from September 2017 to July 2019 in an area near Stelvio Pass (2,758 m a.s.l.) (Italian Central-Eastern Alps) along an altitude gradient. Two sampling sites located at 2600 m a.s.l. and 2200 m a.s.l. in altitude, corresponding to about 3° C difference in the average annual air temperature were chosen. At the 2600 m site, warming experiments using open-top chambers (OTCs) to investigate how climate warming affects SOC were performed. In order to characterize the SOM (Soil Organic Matter), Total carbon (TC), Organic carbon (OC), Total Nitrogen (TN) and Dissolved Organic Carbon (DOC) were determined in soils. TC and TN were determined in biomass. In both soils and biomass were analyzed to quantify the distribution of stable isotopes of C and N, d13C and d15N. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-10750

2020061630 Schaetzl, Randall J. (Michigan State University, Department of Geography, Environment, and Spatial Sciences, East Lansing, MI); Running, Garry L.; Larson, Phillip H. and Rittenour, Tammy M. Sand wedges point to permafrost and aeolian activity in the Chippewa Valley ca. 18-13 ka [abstr.]: in Geological Society of America, North-Central Section, 54th annual meeting, Abstracts with Programs - Geological Society of America, 52(5), Abstract no. 25-1, May 2020. Meeting: Geological Society of America, North-Central Section, 54th annual meeting, May 18-19, 2020, Duluth, MN.

A variety of geomorphic evidence suggests that permafrost was once widespread in the Driftless Area and nearby landscapes such as the Chippewa Valley of western Wisconsin. Permafrost may have covered this landscape from ca. 25-24 ka, when Late Wisconsin ice was at or near its LGM position, until 14-13 ka, or perhaps even until 12.5 ka in preferred locations, as the ice front was variously receding from the region. Our work adds to this chronology for permafrost in the Chippewa valley. Previous and ongoing work in the Chippewa Valley, outside of the Late Wisconsin margin, has indicated that strong winds and aeolian processes also dominated the region during and immediately after the LGM. Dates on sandy aeolian landforms - sand ramps, sand sheets, parabolic dunes and linear dunes ("stringers") - on the valley floor range between ca. 9 and 13 ka, pointing to the end of what may have been a prolonged period of sand mobilization. Loess deposition may have begun at ca. 24 ka, and continued until at least 13 ka. The general lack of loess on the sandy valley floor, coupled with thick loess deposits on the immediate eastern and southeastern sides of large bedrock ridges in the valley, seems to indicate that much of this loess was later deflated and removed, likely on very strong winds, as assisted by saltating sand. An OSL date of ca. 13.2 ka from interbedded loess and aeolian sand from a large ridge appears to constrain the end of this major aeolian interval. We present new data from five sand wedges at two different sites in and near the valley that not only constrain the later part of the permafrost interval, but also link it to aeolian activity in the basin. Wedge morphologies indicate formation within a dry, sandy, windswept, permafrost environment. The dates on these sand wedges, which range from ca. 18.6 to 13.7 ka, provide the first numerical control on the permafrost interval in this region. Together, ages from sand wedges and aeolian landforms indicate a dry, sandy, windswept Chippewa Valley landscape, lasting from at least 18 ka until ca. 13 ka.

2020061631 Shandonay, Kenzie L. (Minnesota State University at Mankato, Earth Systems Laboratory, Mankato, MN); Mataitis, Richard J.; Burds, Luke; Larson, Phillip H.; Bowen, Mark W.; Running, Garry L.; Schaetzl, Randall J. and Rittenour, Tammy. Geomorphology of aeolian sand stringers in western Wisconsin and southeastern Minnesota [abstr.]: in Geological Society of America, North-Central Section, 54th annual meeting, Abstracts with Programs - Geological Society of America, 52(5), Abstract no. 25-2, May 2020. Meeting: Geological Society of America, North-Central Section, 54th annual meeting, May 18-19, 2020, Duluth, MN.

Subtle (1-5 m high), elongate (<20 km long, 10-100 m wide), aeolian deposits termed "sand stringers" have been identified and described throughout the western Great Lakes region beyond the Late Wisconsin glacial margin. Although previous studies have attempted to map their distribution, and to a minor extent examine their composition and absolute age (e.g. Zanner 1999; Koch 2004; Millett et al. 2018), little is known of their geomorphic history and paleoenvironmental significance. This study aims to build on prior work to determine their distribution, orientation, morphology, composition, depositional chronology and processes of formation. The following methods were utilized to better understand these features: 1) GIS/remote sensing techniques to map and analyze their spatial distribution and morphology; 2) ground penetrating radar (GPR) analysis, sediment augering, and pedon descriptions to characterize their stratigraphy; and 3) optically stimulated luminescence dating (OSL) to constrain the timing of their formation and evolution. Although prior mapping efforts noted >500 sand stringers in western Wisconsin and southeastern Minnesota, our more conservative mapping approach identified, with high confidence, 246 such features. Of these, 91% were orientated WNW-ESE. OSL ages on five stringers range from ~12.9 ka to ~8.8 ka. Comprehensive investigation of one stringer resulted in GPR imagery showing sub-parallel and slightly undulating stratigraphy in the stringers, but 3D analysis is still needed. Augering revealed three distinct units consisting of a lower coarse sand unit interpreted as glacial outwash, a middle unit of fine to medium sand interpreted as aeolian sand, and an upper unit composed of fine sand and silt interpreted as loess. From this analysis we hypothesize that sand stringers formed in a post-permafrost landscape with sparse vegetation. Thawing allowed sand to be mobilized and the lack of vegetation allowed for aeolian transport and deposition. Initial deposition within the sand stringer consisted of aeolian sand, shifting to loess, possibly as the climate warmed and the landscape began to stabilize.

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