July 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 July Alert contains 84 citations from the 2020 meeting of the European Geosciences Union General Assembly.

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

2020055513 Chen Shengyun (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Cryospheric Science, Lanzhou, China); Li Xiangfei; Wu Tonghua; Xue Kai; Luo Dongliang; Wang Xiaoming; Wu Qingbai; Kang Shichang; Zhou Huakun and Wei Dengxian. Soil thermal regime alteration under experimental warming in permafrost regions of the central Tibetan Plateau: Geoderma, 372, Article no. 114397, illus. incl. 2 tables, sketch map, 81 ref., August 1, 2020.

Soil thermal regime in permafrost regions is sensitive to climate change and may cause vast ecological consequences under future warming scenarios. However, there still lacks a systematic evaluation on the effect of warming on soil thermodynamics in the different ecosystems of permafrost regions. This study investigated the alterations of soil thermodynamics in alpine swamp meadow and alpine steppe under experimental warming by open-top chambers in permafrost regions of the central Tibetan Plateau. The results showed that air temperature increased significantly with an annual mean increase of 1.4 °C under warming. Compared to alpine swamp meadow, soil thermodynamics represented by soil temperature, soil thermal parameters, soil freeze-thaw process and active layer thickness in alpine steppe was more susceptible to warming. Specifically, soil temperature at 5-40 cm depths increased more in alpine steppe than alpine swamp meadow under warming, especially at topsoil (5-20 cm). Moreover, the increase in soil temperature at topsoil was greater during cold season than warm season. Greater alterations of soil thermal parameters were likely because soil moisture content reduced more in alpine steppe. Regarding soil freeze-thaw process, warming significantly postponed the onset of completely frozen stage and reduced the completely frozen days in alpine steppe. Active layer thickness in alpine steppe distinctly increased by 46 cm on average and showed an increasing trend under warming from 2009 to 2011. Overall, vegetation coverage and soil moisture content were responsible for the different responses of soil thermodynamics to experimental warming. The study has important implications for future scenarios as permafrost and grassland degradation may intensify under climate warming.

DOI: 10.1016/j.geoderma.2020.114397

2020059158 Warbritton, Matthew J. (Iowa State University, Department of Geological and Atmospheric Sciences, Ames, IA); Iverson, Neal R.; Lagroix, France and Schomacker, Anders. Strain patterns in glacitectonically thrusted sediments and conditions during thrusting: Journal of Structural Geology, 137, Article 104064, illus. incl. 1 table, sketch map, August 2020. Based on Publisher-supplied data.

Glacitectonically thrusted blocks of unlithified sediment are commonly inferred to have been frozen during thrusting, with implications for paleoclimate and glacier dynamics. We inferred strain patterns within thrusted blocks of glaciolacustrine mud in the Rubjerg Knude and Mons Klint glacitectonic complexes of coastal Denmark to try to assess whether the mud was frozen during thrusting. Fabrics based on the anisotropy of magnetic susceptibility (AMS) of the muds are interpreted with results of ring-shear experiments and models of AMS fabric development during layer-parallel shortening (LPS). In intact distal stratigraphy, fabrics indicate moderate LPS. Fabrics where thrusts have disrupted more proximal stratigraphy indicate rotation of mud sheets during thrusting with insufficient penetrative strain to reset the LPS fabric. The exception is within decimeters of faults at Rubjerg Knude where shear overprinted the LPS fabric. Although these data indicate that mud sheets were mostly rigid during thrusting, this is not necessarily evidence of permafrost. Critical-taper theory indicates that even a gentle slope of the proglacial surface away from the glacier margin would have allowed slip without internal deformation of thrust sheets, requiring only minimal pore-water pressures.

DOI: 10.1016/j.jsg.2020.104064

2020059145 Li, Dongfeng (National University of Singapore, Department of Geography, Singapore, Singapore); Li Zhiwei; Zhou Yinjun and Lu, Xixi. Substantial increases in the water and sediment fluxes in the headwater region of the Tibetan Plateau in response to global warming: Geophysical Research Letters, 47(11), Paper no. e2020GL087745, illus. incl. sketch maps, 36 ref., May 16, 2020.

The long-term effects of increased temperatures on sediment fluxes in cold regions remain poorly investigated. Here, we examined the multidecadal changes in runoff and sediment fluxes in the Tuotuohe River, a headwater river of the Yangtze River on the Tibetan Plateau (TP). The sediment fluxes and runoff increased at rates of 0.03±0.01 Mt/yr (5.9±1.9%/yr) and 0.025±0.007´km3/yr (3.5±1.0%/yr) from 1985 to 2016, with net increases of 135% and 78% from 1985-1997 to 1998-2016, respectively. The increases are primarily due to warming temperature (+1.44°C) and intensified glacier-snow-permafrost melting, with enhanced precipitation (+30%) as a secondary cause. Sediment fluxes are much more susceptible to climate warming than runoff in this undisturbed cold environment. The substantially increased sediment fluxes from the headwater region could threaten the numerous constructed reservoirs and influence the aquatic ecosystems of the TP and its marginal areas. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GL087745

2020059143 O'Connor, Michael T. (University of Texas at Austin, Department of Geological Sciences, Austin, TX); Cardenas, M. Bayani; Ferencz, Stephen B.; Wu, Yue; Neilson, Bethany T.; Chen, Jingyi and Kling, George W. Empirical models for predicting water and heat flow properties of permafrost soils: Geophysical Research Letters, 47(11), Paper no. e2020GL087646, illus. incl. sketch map, 42 ref., May 16, 2020.

Warming and thawing in the Arctic are promoting biogeochemical processing and hydrologic transport in carbon-rich permafrost and soils that transfer carbon to surface waters or the atmosphere. Hydrologic and biogeochemical impacts of thawing are challenging to predict with sparse information on arctic soil hydraulic and thermal properties. We developed empirical and statistical models of soil properties for three main strata in the shallow, seasonally thawed soils above permafrost in a study area of ~7.500 km2 in Alaska. The models show that soil vertical stratification and hydraulic properties are predictable based on vegetation cover and slope. We also show that the distinct hydraulic and thermal properties of each soil stratum can be predicted solely from bulk density. These findings fill the gap for a sparsely mapped region of the Arctic and enable regional interpolation of soil properties critical for determining future hydrologic responses and the fate of carbon in thawing permafrost. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GL087646

2020059139 Young, Nathan Lee (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Lemieux, Jean-Michel; Delottier, H.; Fortier, R. and Fortier, Philippe. A conceptual model for anticipating the impact of landscape evolution on groundwater recharge in degrading permafrost environments: Geophysical Research Letters, 47(11), Paper no. e2020GL087695, illus. incl. 1 table, sketch map, 41 ref., May 16, 2020.

Temperatures in the arctic and subarctic are rising at more than twice the rate of the global average, driving the accelerated thawing of permafrost across the region. The impacts of permafrost degradation have been studied in the discontinuous permafrost zone at Umiujaq, in northern Quebec, Canada, for over 30 years, but the effects of changing land cover on groundwater recharge are not well understood. The water table fluctuation method was used to compute groundwater recharge using 4 years of water level data and soil moisture readings from five field sites characteristic of different stages of permafrost degradation and vegetation invasion. Results indicate that as vegetation grows taller, groundwater recharge increases, likely due to increased snow thickness. Results were then combined with a preexisting conceptual model that describes the evolution from tundra to shrubland and forests to create a new model for describing how groundwater recharge is affected by landscape evolution. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GL087695

2020057642 Chen, Lin (University of Montreal, Geography Department, Geocryolab, Cold regions geomorphology and geotechnical laboratory, Montreal, QC, Canada); Fortier, Daniel; McKenzie, Jeffrey M. and Sliger, Michel. Impact of heat advection on the thermal regime of roads built on permafrost: Hydrological Processes, 34(7), p. 1647-1664, illus. incl. 6 tables, 76 ref., March 30, 2020.

In northern regions, transportation infrastructure can experience severe structural damages due to permafrost degradation. Water infiltration and subsurface water flow under an embankment affect the energy balance of roadways and underlying permafrost. However, the quantification of the processes controlling these changes and a detailed investigation of their thermal impacts remain largely unknown due to a lack of available long-term embankment temperature data in permafrost regions. Here, we report observations of heat advection linked to surface water infiltration and subsurface flow based on a 9-year (from 2009 to 2017) thermal monitoring at an experimental road test site built on ice-rich permafrost conditions in southwestern Yukon, Canada. Our results show that snowmelt water infiltration in the spring rapidly increases temperature in the upper portion of the embankment. The earlier disappearance of snow deposited at the embankment slope increases the thawing period and the temperature gradient in the embankment compared with the natural ground. Infiltrated summer rainfall water lowered the near-surface temperatures and subsequently warmed embankment fill materials down to 3.6-m depth. Heat advection caused by the flow of subsurface water produced warming rates at depth in the embankment subgrade up to two orders of magnitude faster than by atmospheric warming (heat conduction). Subsurface water flow promoted permafrost thawing under the road embankment and led to an increase in active layer thickness. We conclude that the thermal stability of roadways along the Alaska Highway corridor is not maintainable in situations where water is flowing under the infrastructure unless mitigation techniques are used. Severe structural damages to the highway embankment are expected to occur in the next decade. Abstract Copyright (2020), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.13688

2020056527 Song Chunlin (Chinese Academy of Sciences, Institute of Mountain Hazards and Environment, Chengdu, China); Wang Genxu; Mao Tianxu; Dai Junchen and Yang, Daqing. Linkage between permafrost distribution and river runoff changes across the Arctic and the Tibetan Plateau: Science China. Earth Sciences, 63(2), p. 292-302, illus. incl. 2 tables, geol. sketch maps, 47 ref., February 2020.

River runoff in the Arctic and the Tibetan Plateau (TP) change significantly in recent decades. However, the mechanisms of the physical processes of permafrost river runoff change remain uncertain across large scale. This study investigated the mainstreams and tributaries of main Arctic and TP rivers dominated by permafrost and assessed the linkage between hydrological regime change and permafrost. The results show that the effects of permafrost on river runoff are highly dependent on the permafrost coverage of a watershed. For the past decades, the majority of the Arctic and TP basins showed increased discharge, while all of the studied basins showed increased baseflow, with faster increasing speed than total discharge. Both total discharge and baseflow annual change rate (DQ and DBF) increased with permafrost coverage, indicating the increments of streamflow are enhanced with high permafrost coverage. Meanwhile, the annual change of precipitation showed weak connection with total discharge and baseflow change. The high permafrost coverage basins showed high annual maximum/ minimum discharge ratio (Qmax/Qmin), while the Qmax/Qmin changed slightly in low permafrost cover basins. Our results highlight the importance of permafrost coverage on streamflow regime change for permafrost basins across the northern hemisphere. Due to these linkage between permafrost extent and runoff regime change and the increasing changes of permafrost, more attention should be paid to the change of hydrological processes in permafrost-underlain basins.

DOI: 10.1007/s11430-018-9383-6

2020057612 Wang Genxu (Chinese Academy of Sciences, Institute of Mountain Hazards and Environment, Key Laboratory of Mountain Surface Processes and Ecological Regulation, Chengdu, China); Lin Shan; Hu Zhaoyong; Lu Yaqiong; Sun Xiangyang and Huang Kewei. Improving actual evapotranspiration estimation integrating energy consumption for ice phase change across the Tibetan Plateau: Journal of Geophysical Research: Atmospheres, 125(3), Paper no. e2019JD031799, illus. incl. 3 tables, sketch maps, 38 ref., February 16, 2020.

Permafrost thawing over the Tibetan Plateau (TP) is a consequence of climatic warming, which will change local hydrological processes remarkably. Evapotranspiration (ET) is an important local hydrological process indicator that needs to be well quantified. Several methods have been applied to estimate the ET. However, energy consumed by thawing was neglected in ET estimation on TP. Here a simple but effective method was introduced to represent the energy consumption due to ice phase changes in the generalized nonlinear complementary principle. Our method improved ET estimation by 4.60-106.67% in the nonlinear complementary model, validated at five eddy flux observation sites. With the new formulation, we analyzed the spatiotemporal patterns of ET and their driving factors during 1961-2014. The spatial averaged ET was 294.21 mm/year and decreased from southeast to northwest areas, cocontrolled by precipitation (Pre) and net radiation (Rn); dominated by the Rn in the warm-humid areas while by the Pre in the cold-dry areas. The temporal pattern of ET over the TP showed an increasing trend during 1961-2014, with a rate of 0.38 mm/year. The variations in air temperature (Tair) and Rn could explain 79.1% of the temporal variations in ET over the TP during the past 54 years, indicating atmosphere demand is the dominant factor on ET temporal variation. We also found that permafrost thawing accelerated the ET increases in the last 15 years over the transitional permafrost and seasonal permafrost areas, suggesting that degradation and ablation of permafrost under climatic changes will lead to accelerated ET. Abstract Copyright (2020), American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2019JD031799

2020056607 Fernandez, Leyden (Uppsala University, Department of Ecology and Genetics, Uppsala, Sweden); Bertilsson, Stefan and Peura, Sari. Non-cyanobacterial diazotrophs dominate nitrogen-fixing communities in permafrost thaw ponds: in Linking metagenomics to aquatic microbial ecology and biogeochemical cycles (Grossart, Hans-Peter, editor; et al.), Limnology and Oceanography, 65(S1), p. S180-S193, illus. incl. 3 tables, 74 ref., January 2020.

There is a growing concern about the implications of accelerated thawing of permafrost for regional biogeochemical cycling of carbon and other bioreactive elements. One such element of concern is nitrogen, and in this study, we investigated the diversity and biogeography of potential diazotrophs within a series of thaw ponds representing different ontogenetic stages in pond development. Using metagenomic sequence data from subarctic thaw ponds, we identified an array of nitrogenase genes across the ponds. The iron-only nitrogenase gene (anfH) was positively correlated with sulfate, while there was no correlation with methane despite previous findings that organisms carrying anfH can simultaneously participate in nitrogen fixation and methanogenesis. Sulfate is known to inhibit microbial uptake of molybdate, an element essential for the activity of the nifH (molybdenum-iron) nitrogenase and this may explain the high potential for nitrogen fixation utilizing anfH in sulfate-rich ponds. NifH was particularly abundant in the hypolimnion of the deeper and older ponds, with Deltaproteobacteria and Chlorobi as the putative dominant diazotrophs. In the epilimnetic waters, nifH composition was more variable, with various Gammaproteobacteria as abundant representatives, while cyanobacterial diazotrophs were scarce. Interestingly, nifH gene abundance was significantly positively correlated with in situ methane concentration. Based on genome-resolved metagenomics, we hypothesize that diazotrophs and methanogens engage in syntrophic interactions in anoxic waters, possibly via propionate oxidation or (in Geobacter) by interspecies electron transfer. Our results also suggest that nitrogen fixers may supply bioreactive nitrogen compounds to the thaw pond communities, thereby enhancing growth and activity of methanogens. Abstract Copyright (2019), Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11243

2020056608 Peura, Sari (Swedish University of Agricultural Science, Department of Forest Mycology and Plant Pathology, Science for Life Laboratory, Uppsala, Sweden); Wauthy, Maxime; Simone, Domenico; Eiler, Alexander; Einarsdottir, Karolina; Rautio, Milla and Bertilsson, Stefan. Ontogenic succession of thermokarst thaw ponds is linked to dissolved organic matter quality and microbial degradation potential: in Linking metagenomics to aquatic microbial ecology and biogeochemical cycles (Grossart, Hans-Peter, editor; et al.), Limnology and Oceanography, 65(S1), p. S248-S263, illus., 72 ref., January 2020.

Warming climate is thawing the permafrost in arctic and subarctic regions, leading to formation of thermokarst ponds. During the formation and geomorphological succession of these ponds, carbon that has been trapped in frozen soils for thousands of years is hydrologically mobilized and returned to the active carbon cycle. We sampled 12 thermokarst ponds representing three different stages of pond succession to study the potential of microbial communities to metabolize the organic carbon in the water. We investigated the quality of the dissolved organic carbon (DOC) in the water column based on the spectrophotometric and fluorometric properties of the chromophoric dissolved organic matter combined with parallel factor analysis and the potential of the microbial community for degrading these carbon compounds based on genetic markers related to carbon degradation. Our analysis showed a clear difference in the DOC quality across the different developmental stages. In the younger ponds, organic matter quality suggested that it was originating from the degrading permafrost and in the metagenomes collected from these ponds, the normalized abundance of genes related to degradation of carbon compounds was higher. There was also a shift in the degradation potential in the water column of the ponds, with higher potential for organic matter degradation in deeper, anoxic layers. In conclusion, our results show that the DOC quality and the genetic potential of the microbial community for carbon cycling change across the pond ontogeny, suggesting a capacity of the microbial communities to adapt to changing environmental conditions. Abstract Copyright (2019), The Authors. Periodicals, Inc. on behalf of Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11349

2020058969 Liu Futing (Chinese Academy of Sciences, Institute of Botany, State Key Laboratory of Vegetation and Environmental Change, Beijing, China); Kou Dan; Abbott, Benjamin W.; Mao Chao; Chen Yongliang; Chen Leiyi and Yang Yuanhe. Disentangling the effects of climate, vegetation, soil and related substrate properties on the biodegradability of permafrost-derived dissolved organic carbon: Journal of Geophysical Research: Biogeosciences, 124(11), p. 3377-3389, illus. incl. 1 table, sketch map, 79 ref., November 2019.

Dissolved organic carbon (DOC) plays an important role in permafrost carbon cycle. However, substantial uncertainties remain about what determines the biodegradability of permafrost-derived DOC and how the biodegradability varies between permafrost and active-layer soils at a regional scale. Here, we conducted an incubation experiment with DOC leached from permafrost and active-layer soils along a »1,000-km permafrost transect on the Tibetan Plateau. Our results showed that permafrost-derived DOC had high biodegradability, with an average of 21.7% loss of DOC over a 28-day incubation. The biodegradability of DOC leached from permafrost soils was larger than or equal to that in active-layer within 72% of sampling sites. Our results also revealed that variation in DOC biodegradability in permafrost soils and its difference with that in active-layer soils were jointly determined by vegetation types, soil properties, and related DOC composition. The biodegradability of permafrost-derived DOC in alpine steppe and meadow was lower than that in swamp meadow. It also declined with the decreasing soil carbon: nitrogen ratio, increasing pH, clay content, DOC molecular weight, and its degradation degree. Similarly, the variability in the difference of DOC biodegradability between permafrost and active-layer soils also resulted from the differences of three types of above-mentioned factors between the two layers. These results suggest that permafrost thawing-induced DOC release could intensify permafrost carbon-climate feedback due to its vulnerability to microbial decomposition, with its impact depending on vegetation, soil, and substrate properties. Abstract Copyright (2019), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2018JG004944

2020058975 Matveev, Alex (Center for Northern Studies, Quebec City, QC, Canada); Laurion, Isabelle and Vincent, Warwick F. Winter accumulation of methane and its variable timing of release from thermokarst lakes in subarctic peatlands: Journal of Geophysical Research: Biogeosciences, 124(11), p. 3521-3535, illus. incl. 4 tables, 59 ref., November 2019.

Previous studies of thermokarst lakes have drawn attention to the potential for accumulation of CH4 under the ice and its subsequent release in spring; however, such observations have not been available for thermokarst waters in carbon-rich peatlands. Here we undertook a winter profiling of five black-water lakes located on eroding permafrost peatlands in subarctic Quebec for comparison with summer profiles and used a 2-year data set of automated water temperature, conductivity, and oxygen measurements to evaluate how the annual mixing dynamics may affect the venting of greenhouse gases to the atmosphere. All of the sampled lakes contained large amounts of dissolved CH4 under their winter ice cover. These sub-ice concentrations were up to 5 orders of magnitude above air equilibrium (i.e., the expected concentration in lake water equilibrated with the atmosphere), resulting in calculated emission rates at ice breakup that would be 1-2 orders of magnitude higher than midsummer averages. The amount of CO2 dissolved in the water column was reduced in winter, and the estimated ratio of potential diffusive CO2 to CH4 emission in spring was half the measured summer ratio, suggesting a seasonal shift in methanogenesis and bacterial activity. All surface lake ice contained bubbles of CH4 and CO2, but this amounted to <5% of the total amount of the dissolved CH4 and CO2 in the corresponding lake water column. The continuous logging records suggested that lake morphometry may play a role in controlling the timing and extent of CH4 and CO2 release from the water column to the atmosphere. Abstract Copyright (2019), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2019JG005078

2020057597 Vecellio, Daniel J. (Texas A&M University, Department of Geography, Climate Science Laboratory, College Station, TX); Nowotarski, Christopher J. and Frauenfeld, Oliver W. The role of permafrost in Eurasian land-atmosphere interactions: Journal of Geophysical Research: Atmospheres, 124(22), p. 11644-11660, illus. incl. 3 tables, 59 ref., November 27, 2019.

Permafrost is an important indicator of climate change that affects, e.g., ecosystems, hydrology, and infrastructure in cold regions. Interactions between the surface and atmosphere in permafrost regions are complex and vary seasonally due to the contrasting energy and moisture conditions of frozen versus unfrozen ground. Differences in surface-atmosphere connections have been documented between permafrost types, with significantly increased moisture feedbacks in areas of continuous Eurasian permafrost, but no such relationship in other regions. This study elucidates the processes responsible for these observed land-atmosphere feedbacks in Eurasian permafrost regions. The Weather Research and Forecasting model is used to determine the varying effects of discontinuous versus continuous permafrost on different weather scenarios. For two 72-hour periods, surface fluxes, boundary layer characteristics, and corresponding meso-to-synoptic scale meteorological features varied when comparing the two experiments: one with a saturated active layer representing continuous permafrost, and another witht a drier surface layer representing discontinuous permafrost. Depending on the weather regime, an increase in boundary layer moisture in response to increased latent heat fluxes over continuous permafrost increases precipitation and low-level cloudiness. The effects of changing soil conditions are evident as far aloft as 500 hPa, as a mid-level low over continuous permafrost is stronger and moves southward. Incipient moisture associated with continuous permafrost allows for different land-atmosphere interactions than over discontinuous permafrost. Continued permafrost degradation as a result of climate change may lead to increased dryness in the region, altering the surface energy balance and associated weather and climate feedbacks. Abstract Copyright (2019), American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2019JD031204

2020058730 Cao, Xianyong (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Research Unit Potsdam, Potsdam, Germany); Tian, Fang; Li, Furong; Gaillard, Marie-José; Rudaya, Natalia; Xu Qinghai and Herzschuh, Ulrike. Pollen-based quantitative land-cover reconstruction for northern Asia covering the last 40 ka cal BP: Climate of the Past, 15(4), p. 1503-1536, illus. incl. 5 tables, 229 ref., 2019.

We collected the available relative pollen productivity estimates (PPEs) for 27 major pollen taxa from Eurasia and applied them to estimate plant abundances during the last 40 ka cal BP (calibrated thousand years before present) using pollen counts from 203 fossil pollen records in northern Asia (north of 40°N). These pollen records were organized into 42 site groups and regional mean plant abundances calculated using the REVEALS (Regional Estimates of Vegetation Abundance from Large Sites) model. Time-series clustering, constrained hierarchical clustering, and detrended canonical correspondence analysis were performed to investigate the regional pattern, time, and strength of vegetation changes, respectively. Reconstructed regional plant functional type (PFT) components for each site group are generally consistent with modern vegetation in that vegetation changes within the regions are characterized by minor changes in the abundance of PFTs rather than by an increase in new PFTs, particularly during the Holocene. We argue that pollen-based REVEALS estimates of plant abundances should be a more reliable reflection of the vegetation as pollen may overestimate the turnover, particularly when a high pollen producer invades areas dominated by low pollen producers. Comparisons with vegetation-independent climate records show that climate change is the primary factor driving land-cover changes at broad spatial and temporal scales. Vegetation changes in certain regions or periods, however, could not be explained by direct climate change, e.g. inland Siberia, where a sharp increase in evergreen conifer tree abundance occurred at ca. 7-8 ka cal BP despite an unchanging climate, potentially reflecting their response to complex climate-permafrost-fire-vegetation interactions and thus a possible long-term lagged climate response.

DOI: 10.5194/cp-15-1503-2019

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CONFERENCE REFERENCES

2020059523 Ala-aho, Pertti (University of Oulu, Water, Energy and Environmental Engineering Research Unit, Oulu, Finland); Autio, Anna; Bhattacharjee, Joy; Isokangas, Elina; Kujala, Katharina; Marttila, Hannu; Menberu, Meseret; Merio, Leo-Juhani; Postila, Heini; Rauhala, Anssi; Ronkanen, Anna-Kaisa; Rossi, Pekka M.; Saari, Markus; Haghighi, Ali Torabi and Klove, Bjorn. Influence of seasonally frozen ground on hydrological partitioning; a global systematic review [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8441, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Seasonally frozen ground (SFG) occurs on ~25% of the Northern Hemisphere's land surface, and the influence of SFG on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively researched, but the influence of SFG has been receiving less attention. Intuitively, water movement in frozen ground is blocked by ice forming in soil pores that were open to water flow prior to freezing. However, it has been shown that the hydrological influence of SFG is insignificant in some cases, with soil remaining permeable to water even when frozen. There is a clear knowledge gap concerning (1) how intensively and (2) under what physiographical and climate conditions SFG influences hydrological fluxes. We conducted a systematic literature review examining the hydrological importance of SFG we found reported in 143 publications. We found a clear hydrological influence of frozen ground in small-scale laboratory measurements, but a more ambiguous effect when the spatial scale under study increased to hillslopes, catchments, or watersheds. We also found that SFG may be hydrologically less important in forested areas or in regions with deep snow cover. Our systematic review suggests that hydrological influence of SFG may become more important in a future warmer climate with less snow and intensified land use in high-latitude areas. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8441

2020059434 Alekseev, Ivan (Saint Petersburg State University, Biological Faculty, St. Petersburg, Russian Federation) and Abakumov, Evgeny. Soil organic matter in soils of the Russian Arctic; insights from 13C-NMR spectroscopy [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1058, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Polar soils play a key role in global carbon circulation and stabilization as they contain maximum stocks of soil organic matter (SOM) within the whole pedosphere. Cold climate and active layer dynamics result in the stabilization of essential amounts of organic matter in soils, biosediments, and grounds of the polar biome. Chemical composition of soil organic carbon (SOC) determines its decomposability and may affect soil organic matter stabilization (SOM) rate (Beyer, 1995). This is quite important for understanding variability in SOC pools and stabilization rate in context of changes in plant cover or climate (Rossi et al. 2016). 13C nuclear magnetic resonance spectroscopy, which provides detailed information on diversity of structural composition of humic acids and SOM, may also be used to study the SOM dynamics under decomposition and humification processes (Kogel-Knabner, 1997; Zech et al., 1997). This study aims to characterize molecular organization of the humic acids, isolated from various permafrost-affected soils of Yamal region and to assess the potential vulnerability of soils organic matter in context of possible mineralization processes. Organic carbon stocks for studied area were 7.85 ± 2.24 kg m-2 (for 0-10 cm layer), 14.97 ± 5.53 kg m-2 (for 0-30 cm), 23.99 ± 8.00 kg m-2 (for 0-100 cm). Results of solid-state 13C-NMR spectrometry showed low amounts of aromatic components in studied soils. All studied humic powders are characterized by predominance of aliphatic structures, and also carbohydrates, polysaccharides, ethers and amino acids. High content of aliphatic fragments in studied humic acids shows their similarity fulvic acids. Low level of aromaticity reflects the accumulation in soil of lowly decomposed organic matter due to cold temperatures. Our results provide further evidence of high vulnerability and sensitivity of permafrost-affected soils organic matter to Arctic warming. Consequently, these soils may play a crucial role in global carbon balance under effects of climate warming. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1058

2020059501 Bernhard, Philipp (ETH Zürich, Department of Civil, Environmental and Geomatic Engineering, Zurich, Switzerland); Zwieback, Simon; Leinss, Silvan and Hajnsek, Irena. Monitoring rapid permafrost thaw using elevation models generated from satellite radar interferometry [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6965, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to terrain-altering thermokarst in a warming climate. Among the most rapid and dramatic changes are retrogressive thaw slumps. These slumps evolve by a retreat of the slump headwall during the summer months, making them detectable by comparing digital elevation models over time using the volumetric change as an indicator. Despite the availability of many topographic InSAR observations to generate digital elevation models, there is currently no method to map and analyze retrogressive thaw slumps. Here, we present and assess a method to detect and monitor thaw slumps using time-series of elevation models (DEMs), generated from single-pass InSAR observations, which have been acquired across the Arctic at high resolution since 2011 by the TanDEM-X satellite pair. At least three observations over this timespan are available with a spatial resolution of about 12 meter and the height sensitivity of 0.5-2 meter. We first difference the generated digital elevation and detect significant elevation changes taking the uncertainty estimates of each elevation measurement into account. In the implementation of the processing chain we focused on making it as automated as much as possible to be able to cover large areas of the northern hemisphere. This includes detecting common problems with the data and apply appropriate algorithms to obtain DEMs with high accuracy. Additionally we implemented methods to deal with problematic features like wet-snow, vegetation and water bodies. After generating the DEMs we use DEM differencing followed by a blob detection and cluster algorithm to detect active thaw slumps. To improve the accuracy of our method we apply and compare different machine learning methods, namely a simple threshold method, a Random Forest and a Support-Vector-Machine. To estimate the accuracy of our method we use data from past studies as well as a classification based on optical satellite data. The obtained locations of thaw slumps can be used as a starting point to extract important slump properties, like the headwall height and volumetric change, which are currently not available on regional scales. Additionally to the thaw slump detection, we show first results of the thaw slump property extraction for thaw slumps located in Northern Canada (Peel Plateau, Mackenzie River Delta, Banks Island, Ellesmere Island). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6965

2020059463 Bernsteiner, Heidi (University of Bayreuth, Chair of Geomorphology, Bayreuth, Germany); Götz, Joachim; Haas, Florian; Heckmann, Tobias; Sass, Oliver and Becht, Michael. Ground and dead ice in Alpine proglacial areas; sensitivity towards climate change since 1850, recent dynamics and future trends [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3310, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

As the climate warms, the earths' cryosphere melts. Among the regions with the highest sensitivity to recent climate change are the high altitudes of the European Alps. This can be seen most clearly in the melting of glacier ice. Most glaciers show a strong receding trend since the last maximum extent during the little ice age (LIA) around AD 1850. When glaciers retreat, they leave behind a characteristic paraglacial landscape in a transient state from glacial to non-glacial conditions. Dominated by large amounts of unconsolidated glacial sediments they show an extremely high geomorphic activity. However, these proglacial areas can still hold ice even decades after the glacier has left. In a simplified manner, this can be conceptually described by two main mechanisms: i) When glaciers retreat parts of the glacier front are often decoupled from the main glacier. These so-called dead ice bodies can remain for years, especially when they are buried by a thick debris cover and thus protected from atmospheric conditions. ii) Particularly in high-elevated glacier forefields, the thermal regime can be suitable for the direct transition from a glacial to a periglacial environment, compassing the aggradation of permafrost ice in areas that have been released from the glacier. Climate warming speeds up in recent times, related with an enhanced receding of glaciers and growing alpine proglacial areas. Ground and dead ice are among the most important drivers of geomorphic activity in these regions, though in the long-term it is most likely, that it will melt out as well. How fast this will happen and in what stage it may play a role in stabilizing these environments is not yet fully clarified. Therefore, a better knowledge on ice distribution and dynamics in alpine proglacial regions is needed. Additionally, the quantification of ice and water contents is crucial in terms of potential hazardous processes, regarding the supply of (drinking) water and hydropower. Here we present a new (PhD-) project in close cooperation with the DFG-funded research unit SEHAG, which is at the beginning of its implementation. Focussing on ground and dead ice we aim i) to assess the current distribution, ii) to reconstruct dynamics since the LIA, iii) to reveal recent and future trends (aggradation, degradation and persistence), and iv) to quantify effects on sediment dynamics in three Central Alpine proglacial areas. We combine different geophysical techniques with a focus on electrical resistivity tomography, water isotope analysis and ground (surface) temperature measurements with high-resolution geomorphic change modelling. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3310

2020059477 Boaga, Jacopo (University of Padova, Department of Geoscience, Padua, Italy); Phillips, Marcia; Noetzli, Jeannette; Haberkorn, Anna; Kenner, Robert and Bast, Alexander. The use of frequency domain electro-magnetometry for the characterization of permafrost active layers; case studies in the Swiss Alps [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5104, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The characterization of the active layer (AL) in mountain permafrost is an important part of monitoring climate change effects in periglagical environments and may help to determine potential slope instability. Permafrost affects 25% of the Northern Hemisphere and 17% of the entire Earth. It has been studied for decades both in the polar regions and - starting a few decades later - in high mountain environments. Typical point information from permafrost boreholes can be extended to wider areas by geophysical prospecting and provide information that cannot be detected by thermal observations alone. During Summer 2019 we performed several geophysical surveys at permafrost borehole sites in the Swiss Alps. We focused on electrical resistivity tomography (ERT) and Frequency Domain Electro-magnetic techniques (FDEM) to compare the methods and test the applicability of FDEM for active layer characterization, i.e., its thickness and lateral continuity. ERT provides an electrical image of the subsoil and can discern active layer thickness, changes in ground ice and geological features of the subsoil. From a logistic point of view a contactless method such as FDEM would be preferable : i) it can provide electrical properties of the subsoil with no need of physical electrical contact with the soil; ii) it can cover a wider area of exploration compared to ERT, iii) it is faster and data collection is simpler than with ERT due to lighter instruments and less preparation time needed. Based on the FDEM surveys at the Swiss permafrost sites we were able to detect the frozen/unfrozen boundary and to achieve results that were in agreement with those obtained from classical ERT and borehole temperature data. The results were promising for future active layer monitoring with the contactless FDEM method. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5104

2020059473 Bordignon, Frederique (Ecole des Ponts ParisTech, Direction de la Documentation, Paris, France). Extracting value from scientific literature with scientometric methods and tools; a case study of permafrost and civil engineering [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4566, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

We illustrate how the use of scientometric methods and tools can facilitate the scanning and interpretation of large volumes of scientific outputs and benefit the literature review of a scientific topic, reducing the cognitive burden to identify emerging trends and shifts in scientific interest. We rely on a corpus of publications about permafrost which proves to be a fast-growing and multifaceted object of study in the geosciences (16,267 references retrieved from Scopus and published since the 1970s) and undertake a scientometric approach to understand the knowledge about permafrost that has been produced and disseminated so far. With the rise of digital technology and the increase in the amount of data available, scientometrics has benefited in its methods from text-mining and data visualisation tools, thus enabling maps to be drawn up to visually represent the semantic space of a textual corpus (for example with networks representing graphically the proximity between strongly related terms) and to observe its dynamics over time. We outline the benefits of 2 scientometric tools and a few of their specific functions: CiteSpace, for a structural analysis based on bibliographic data (e.g. co-citation networks to reveal underlying intellectual structures) and Cortext, for a lexicometric analysis based on terms extracted from metadata and press articles (e.g. co-occurrence networks to detect trends and transition patterns). First, we tackled the corpus in a global and objective way, without presupposing which fields have been involved. Then we focused on one particular field (civil engineering) to demonstrate how we can better feed these tools with terms extracted from a corpus of press articles mentioning construction and building issues. In this longitudinal study, we use 3 units of analysis and evaluate their frequencies, shares and patterns of co-occurrences: disciplinary fields (retrieved via Scopus journal classification scheme), terms (automatically extracted from titles, abstracts and keywords and validated by similar extraction on media articles and expert review), geographical areas (automatically extracted with Name Entity Recognition function, and investigated both as a field of study and also as information about countries interested in any aspect of permafrost). We can then show and explain the increasing share of publications about permafrost, the ever-growing number of disciplinary fields involved along with content fluctuations in the engineering field, the emergence of new associations between terms and in particular with "climate change", and the significant impact of studies about the Qinghai-Tibet plateau. The focus on civil engineering allows us to perform contrast analyses with other sub-corpuses (about climate change or environmental sciences) and to identify the existing overlaps but mostly the gaps to be filled. With this case study on permafrost, we show how scientometric tools can meet the need for objectivity in extensive literature reviews when fake news and climate skepticism are threats to science integrity and the sound dissemination of its results. Besides, we provide for more knowledge about the development of research on permafrost and initiate a particular focus on civil engineering issues providing evidence for future works. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4566

2020059454 Bowring, Simon (Laboratoire des Sciences de Climat et de l'Environnement, Gif-Sur-Yvette, France); Lauerwald, Ronny; Guenet, Bertrand; Jornet-Puig, Albert and Ciais, Philippe. How permafrost-affected Arctic rivers may become net carbon sinks over the 21st century [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2214, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The rivers of the Arctic permafrost region discharge about 11% of the global volumetric river water flux into oceans, doing so into an ocean (the Arctic) with 1% of global ocean water volume and a very high surface area: volume ratio, making it comparatively sensitive to influxes of terrestrially derived matter. This river flux is sourced from precipitation as either rain or snow, which, upon initial contact with the landscape has the immediate potential to interact with carbon (C) in one of two ways: Water running over carbonate or silicate -bearing rocks will cause a reaction whose reactant requires the uptake of atmospheric CO2, which is subsequently transported in river water. This "inorganic" C derived from interaction of water, atmosphere and lithosphere thus represents a C storage or "sink" vector. In addition, water interacting with organic matter in tree canopies, litter or soil can dissolve C contained therein, and transfer it via surface and subsurface water flows into rivers, whereupon it may either be metabolised to the atmosphere or exported to the sea. Recent improvements in understanding of terrestrial C dynamics indicate that this hydrologic transfer of organic matter represents the dominant fate of organic carbon, after plant and soil respiration are accounted for. In the context of amplified Arctic anthropogenic warming, the thermal exposure imposed on the permafrost C stock with expectations of enhanced future precipitation point toward substantial shifts in the lateral flux-mediated organic and inorganic C cycle. However, the complex totality of the processes involved make prediction of this shift difficult. Here, we build upon previous advances in earth system modelling to include the production and lateral transport of dissolved organic C (DOC), respiration-derived CO2, and rock-weathering derived alkalinity in a global land surface model (ORCHIDEE) previously developed to specifically resolve permafrost-region processes. By subjecting the resulting model to state of the art soil, water, vegetation and climatology datasets, we are able to reproduce existing lateral transport processes and fluxes, and project them into the future. In what follows, we show that while Pan-Arctic alkalinity exports and attendant CO2 uptake increase over the 20th and 21st Centuries under warming, DOC fluxes decline largely as a result of deeper soil water flow-paths and the resulting changes in carbon-water interactions. Rather than displaying a clear continuous (linear or nonlinear) temperature sensitivity, future Arctic DOC release can increase or decrease with temperature depending on changes in the thermal state and hydrologic flow paths in the deep soil. The net marine effect of these fluxes is to decrease future terrestrially derived seawater acidification. Conversely, our simulations show that CO2 uptake from chemical weathering exceeds its evasion from river water, meaning that when weathering is considered, the inland water carbon cycle shifts from being a net C-source to a sink. Further, this sink increases into the 21st C, partially buffering soil C loss from permafrost thaw. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2214

2020059503 Bröder, Lisa (Swiss Federal Institute of Technology, Geological Institute, Zurich, Switzerland); Keskitalo, Kirsi; Zolkos, Scott; Shakil, Sarah; Tank, Suzanne; Tesi, Tommaso; Van Dongen, Bart; Haghipour, Negar; Eglinton, Timothy and Vonk, Jorien. Characterization of mobilized sediments and organic matter in retrogressive thaw slumps on the Peel Plateau, NWT, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7176, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Peel Plateau in northwestern Canada hosts some of the fastest growing "mega slumps", retrogressive thaw slumps exceeding 2000 m2 in area. The region is located at the former margin of the Laurentide ice sheet and its landscape is dominated by ice-rich hummocky moraines. Rapid permafrost thaw resulting from enhanced warming and increases in summer precipitation has been identified as a major driver of sediment mobilization in the area, with some of the largest slumps relocating up to 106 m3 of previously frozen sediments into fluvial networks. The biogeochemical transformation of this thawed substrate within fluvial networks may represent a source of CO2 to the atmosphere and have a large impact on downstream ecosystems, yet its fate is currently unclear. Concentrations of dissolved organic matter are lowered in slump-impacted streams, while the particle loads increase. Here, we aim to characterize the mobilized material and its sources by analyzing active layer, Holocene and Pleistocene permafrost, debris (recently thawed, still at the headwall) and slump outflow samples from four different slumps on the Peel Plateau. We use sediment properties (mineral surface area, grain size distribution), carbon isotopes (13C, 14C) and molecular markers (solvent-extractable lipids, lignin phenols, cutin acids, non-extractable compound classes analyzed by pyrolysis-GCMS) in order to assess the composition and quality of the mobilized sediment and organic matter and thereby improve our understanding of their fate and downstream effects. Preliminary results show that organic matter content and radiocarbon age in debris and outflow from all four slumps are dominantly derived from Holocene and Pleistocene permafrost soils with a smaller influence of the organic-rich active layer. Degradation proxies based on extractable lipid and lignin biomarkers suggest Holocene and Pleistocene permafrost organic matter to be more matured than the fresh plant material found in the active layer, while debris and outflow samples show a mixed signal. For the non-extractable organic matter, aromatics and phenols make up the largest fraction of all samples. Lignin markers are almost exclusively found in the active layer samples, which also contain a larger proportion of polysaccharides, while N-containing compounds and alkanes make up the remaining 2-25% with no obvious patterns. Active layer soils also have the highest median grain sizes, whereas Pleistocene permafrost soils consist of much finer mineral grains. Samples collected at the slump outflow are significantly more homogeneous (i.e., showing a narrower grain size distribution) than any of the other samples. We thus infer that both organic matter degradation and hydrodynamic sorting during transport play a role within these slump features; determining their relative magnitudes will be crucial to better assess potential feedbacks of these increasingly abundant "mega slumps" to changing climate. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7176

2020059460 Chaillou, Gwénaëlle (Université du Québec à Rimouski, Institut des Sciences de la Mer de Rimouski, Rimouski, QC, Canada); Kipp, Lauren; Bélanger, Frederik and Whalen, Dustin. Detecting the signature and transformations of water from coastal permafrost thaw in the Beaufort Sea [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3094, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Canadian Beaufort Sea is experiencing coastal erosion at unprecedent rates due to waves impacts and permafrost thaw. Water derived from permafrost thaw has profound impacts on coastal hydrogeology and carbon dynamics. The quality and volume of permafrost water (as surficial and groundwater) discharging to the ocean controls on coastal water chemistry and turbidity. These disturbances alter coastal ecosystems and endanger species with ecological, cultural, and economic value. Robust estimates of these solute and solid inputs are needed on a site-specific scale to obtain accurate regional and global estimations. However, the determination of appropriate endmembers to estimate these fluxes is not straightforward; and yet, little is known about the chemical composition and reactivity of carbon, nutrients and metals of water in coastal permafrost settings. The main objective here is to trace permafrost-derived solutes and study their transport and transformation to coastal water. Several coastal permafrost slumps were visited last summer in the Tuktoyaktuk Peninsula region. Melting-ice, surficial and groundwater were collected to systematically measure short-live isotopes (Rn-222, Ra-223, Ra-224), the stable isotopes of water (d18O, dD), dissolved organic and inorganic carbon (DOC and DIC), chromophoric component of the organic matter (CDOM), total and non-carbonate alkalinity. In front of these systems, surface seawater samples were collected to 1 to 2 km from the shore to trace these chemical inputs to the coastal ocean. Preliminary results will be presented with a specific focus on the geochemical signature of waters at the nearshore. This project is a part of the WP4 Nunataryuk Program, in collaboration with Natural Resources Canada [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3094

2020059465 Chaudhary, Nitin (University of Oslo, Department of Geosciences, Oslo, Norway); Zhang, Wenxin; Schurgers, Guy; Page, Susan and Westermann, Sebastian. Quantification of peatland-mediated feedbacks to the climate system [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3660, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Peatlands are important carbon reserves in the terrestrial ecosystem and cover 3% of the terrestrial land surface. Peatlands have stored around 350-500 Petagrams [1015] of carbon over the last thousands of years, comprising around 30% of the present-day soil organic carbon pool. Peatlands share many characteristics with upland mineral soils and non-peat wetland ecosystems. However, they constitute a unique ecosystem type with many special characteristics, such as a shallow water table depth, carbon-rich soils, a unique vegetation cover, spatial heterogeneity, anaerobic biogeochemistry and permafrost in the high latitude regions (>45°N). The recent changes in climate and land-use patterns have disturbed the Earth's climate-carbon cycle equilibrium. These changes trigger some potentially important land-surface feedbacks, which will further modify the Earth's climate. The ongoing changes in peatland carbon balance as a result of climate warming have the potential for strong positive and negative feedbacks to climate, but these impacts are poorly constrained. To assess the importance of these feedbacks, the interactions between the peatland carbon cycle and climate should be taken into account. However, the absence of peatlands in current Earth system models limits our understanding of the peatland-mediated feedbacks at different scales. LPJ-GUESS peatland-vegetation model showed a reasonable demonstration of capturing the right carbon accumulation rates and permafrost dynamics at different spatial and temporal scales and will be further improved and employed to quantify the hypothesized peatland-mediated feedbacks when coupled with regional/global climate models. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3660

2020059448 Chen Yangxin (Beijing Normal University, GCESS, Beijing, China) and Ji Duoying. Solar radiation modification slows down permafrost carbon loss [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1740, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Circumpolar permafrost is degrading under anthropogenic global warming, thus the large amount of soil organic carbon in it would be vulnerable to microbial decomposition and further aggravating future warming. However, solar radiation modification (SRM), as a theoretical approach to reducing some of the impacts of anthropogenic climate change, hopefully could mitigate the permafrost degradation and slow down permafrost carbon loss. Here we use two solar geoengineering experiments came up in CMIP6/GeoMIP6 -- G6solar and G6sulfur, to explore changes in circumpolar permafrost carbon under solar radiation modification scenarios. Earth system models' simulations show that under G6 scenarios, annual mean surface air temperature in circumpolar permafrost region is about 5 lower relative to the high forcing scenario SSP5-8.5 by year 2100, with a growing trend but remains below 0 from 2015 to 2100, which is close to that in the medium forcing scenario SSP2-4.5. The lower temperature causes lower degradation rate of permafrost area. In SSP5-8.5 scenario, almost all the permafrost thaws by year 2100, but up to half of it remains frozen in SSP2-4.5 and G6 scenarios compared to year 2015. The lower temperature also results in less carbon assimilation in this area, thus the lower vegetation carbon accumulation. By 2100, a maximum soil carbon loss of 18.09 PgC under SSP5-8.5 scenario regarding to different model constructions, while in G6 the soil carbon loss could be reduce to 3.70 PgC, even less than that of 5.29 PgC in SSP2-4.5 scenario. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1740

2020059508 de Bruin, Jelte (Wageningen University, Environmental Sciences Group, Hydrology and Quantitative Water Management, Wageningen, Netherlands); Bense, Victor and van der Ploeg, Martine. Freeze-thaw dynamics in synthetic permafrost soil columns with variable organic carbon content [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7532, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Cold-regions hold a pool of organic carbon that has accumulated over many thousands to millions of years and which is currently kept immobile by permafrost. However, in a warming climate, a deepening of the active layer results in the release of greenhouse gasses CO2 and CH4 into the atmosphere from this carbon pool. Additionally, due to the degradation of deeper permafrost, soil hydraulic properties and associated groundwater flow paths are shifting rapidly as a result of which also organic carbon in deeper permafrost is being dissolved into groundwater, which can then reach the surface environment via groundwater flow. This provides an additional mechanism by which permafrost carbon can be mobilized in a warming climate, and one which is likely increasingly important for progressive surface warming. Although the process of carbon leaching from thawing organic rich permafrost layers into the groundwater is an increasingly important part of the carbon cycle of cold-regions, it is notoriously difficult to measure in situ or incorporate into numerical model assessments due to the highly heterogeneous properties of the permafrost, and lack of process knowledge. In particular, the crucial understanding of the influence of different soil physical properties such as soil grain size and organic matter content on permafrost thawing processes is missing, as well the precise release mechanisms of organic matter into pore waters in thawing soils. This study employs lab soil column experiments to investigate the interplay between soil physical properties and thawing dynamics of permafrost. One meter high soil columns are frozen to create controlled permafrost conditions. A range of sand grain sizes (0.1 to 0.8 mm) and organic matter contents (1 to 10 wt%) representative for sedimentary permafrost are used. The column is thermally insulated on the sides and top, exposing only one face to ambient temperature in the climate chamber. In this way one-dimensional heat flow conditions are created. So far, the columns are equipped with arrays of temperature sensors. Experiments consist of a cycle of freezing and thawing. Our initial data and analysis illustrate how a fast evolving thawing front develops through the frozen soil column including the effects of latent heat at the thawing front. Numerical modeling allows to infer the soil thermal properties relevant to model the permafrost thawing process. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7532

2020059451 Delcourt, Clement J. (Vrije Universiteit Amsterdam, Faculty of Science, Amsterdam, Netherlands); Izbicki, Brian; Kukavskaya, Elena A.; Mack, Michelle C.; Maximov, Trofim C.; Petrov, Roman E.; Rogers, Brendan M.; Scholten, Rebecca; Shestakova, Tatiana; van der Werf, Guido; van Wees, Dave and Veraverbeke, Sander. Carbon emissions from wildfires in larch forest ecosystems of northeast Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1939, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The boreal forest is one of the largest terrestrial carbon reservoirs on Earth and accounts for approximately 30% of the world's forest cover. The boreal carbon balance is thus of global significance. Wildfires affect the boreal carbon balance, releasing large amounts of carbon into the atmosphere when soil organic layers and aboveground biomass are combusted. The boreal forest is warming faster than the global average. These higher temperatures lead to increases in the frequency and severity of wildfire disturbance in boreal regions. Significant progress has been made in quantifying carbon combustion in North American boreal forests, yet few measurements have been conducted in the larch dominated boreal forests of Northeast Siberia. Deciduous needleleaf larch forest growing on continuous permafrost is a unique ecosystem of Siberia. Although these larch forests cover approximately 20% of the boreal biome, the consequences of intensifying fire regimes on the carbon stocks and vegetation dynamics of these ecosystems remain poorly understood. We conducted a field campaign in larch forests around Yakutsk, Northeast Siberia, during the summer of 2019 with the goal of filling parts of these knowledge and data gaps by collecting ground measurements of carbon combustion from two large fire events in 2017 and 2018. During this campaign, we sampled 42 burned sites in two fire scars that cover gradients of fire severity, vegetation composition and landscape position. Within these sites, we performed a wide range of measurements to quantify aboveground and belowground carbon emissions, constrained by data from 12 unburned sites. We also assessed post-fire recovery and active layer deepening. We investigated major drivers of pre-fire carbon stocks and subsequent combustion at the site level. Our results will reduce uncertainties in larger scale estimates of carbon emissions from Siberian fires which is in turn essential for assessing the implications of the climate-induced intensification of fire regimes for the global carbon cycle. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1939

2020059510 Descarrega, Didac Pascual (Lund University, Lund, Sweden); Akerman, Jonas; Becher, Marina; Callaghan, Terry; Christensen, Torben R.; Dorrepaal, Ellen; Emanuelsson, Urban; Giesler, Reiner; Hammarlund, Dan; Hanna, Edward; Hofgaard, Annika; Jin, Hongxiao; Johansson, Cecilia; Jonasson, Christer; Karlsson, Jan; Klaminder, Jonatan; Lundin, Erik; Michelsen, Anders; Olefeldt, David; Persson, Andreas; Phoenix, Gareth; Raczkouska, Zofia; Rinnan, Riikka; Strom, Lena; Tang, Jing; Varner, Ruth; Wookey, Phil and Johansson, Margareta. The missing pieces for better future predictions in subarctic ecosystems [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7684, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic and subarctic ecosystems are undergoing substantial changes in response to climatic and other anthropogenic drivers, and these changes are likely to continue over this Century. Due to the strong linkages between the biotic (vegetation and carbon cycle) and abiotic (permafrost, hydrology and local climate) ecosystem components, the total magnitude of these changes result from multiple interacting effects that can enhance or counter the direct effects. In some cases, short-lived extreme events can override climate-driven long-term trends. The field measurements can mostly tackle individual drivers rather than the interactions between them. Currently, a comprehensive assessment of the drivers of different changes and the magnitude of their impact on subarctic ecosystems is missing. The Tornetrask area, in the Swedish subarctic, has an unrivalled history of environmental observation over 100 years and encompasses the 12% of all published papers and the 19% of all study citations across the Arctic. In this study, we summarize and rank the direct and indirect drivers of ecosystem change in the Tornetrask area, and propose future research priorities identified to improve future predictions of ecosystem change. First, we identified the direct and indirect changing drivers and the multiple related processes and feedbacks impacting the local climate, permafrost, hydrology, vegetation, and the carbon cycle based on the existing literature. Subsequently, an Expert Elicitation with the participation of 27 leading scientists was used to rank the short- (2020-2040) and long-term (2040-2100) future impact of these drivers according to their opinions on the relative importance and novelty. These two key evaluation matrices form the basis for identifying the current research priorities for subarctic regions. The relatively small size of the Tornetrask area, its great biological and geomorphological complexity, and its unique datasets is a microcosm of the subarctic and the rapidly transforming Arctic ecosystems that can help understand the ongoing processes and future ecosystem changes at a larger circumpolar-scale. This in turn will provide the basis for future mitigation and adaptation plans needed in a changing climate.

DOI: 10.5194/egusphere-egu2020-7684

2020059513 Dietze, Elisabeth (Alfred-Wegener-Institute Helmholtz-Centre for Polar and Marine Research, Potsdam, Germany); Mangelsdorf, Kai; Andreev, Andrei; Schwamborn, Georg; Melles, Martin; Wennrich, Volker; Fedorov, Grigory; Vyse, Stuart and Herzschuh, Ulrike. What do anhydrosugars in up to 420 kyrs old Lake El'gygytgyn sediments tell us about low-temperature fires of northeastern Siberia? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8019, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Forest fires are an important factor of the global carbon cycle and high latitude ecosystems. Eastern Siberian tundra, summergreen larch-dominated boreal forest on permafrost and evergreen spruce- and pine-dominated boreal forest have characteristic fire regimes with varying fire frequencies and intensities. However, it is unknown which role fire plays in climate-vegetation-permafrost feedbacks and how high-latitude fire regimes and ecosystems will change in a warmer world - questions that are crucial considering that boreal and permafrost regions have been identified as tipping elements in the climate system (Lenton et al., 2008, PNAS). Here, we investigate fire regime shifts during previous warmer-than-present interglacials, i.e. marine isotope stages (MIS) 5e and 11c, which were not influenced by human activity. We use specific biomass burning residues, i.e. monosaccharide anhydrides (anhydrosugars), that are a rather chemically reactive group of pyrogenic carbon. These molecules are mainly produced by low-temperature fires, but their pathways through the Earth system from source to sink and their stability in sedimentary deposits are very poorly constrained (Suciu et al. 2019, Biogeochemistry). A recent study (Dietze et al., 2020, ClimPastDisc) found anhydrosugars in up to 420 kyr old sediment of Lake El'gygytgyn (ICDP Site 5011-1), northeastern Siberia, and suggest that these molecular markers are suitable proxies for fires in Siberian summergreen boreal forests. Surprisingly, the ratios of the anhydrosugars levoglucosan to its isomers mannosan and galactosan were exceptionally low compared to published emission ratios from modern biomass burning, pointing to either a specific local biomass source and/or isomer-specific preservation. To understand what anhydrosugars from interglacial Arctic lake sediments tell us about fire regime changes, we studied modern sediment samples from Lake El'gygytgyn, its catchment and from other lakes located in East Siberian summergreen and evergreen boreal forest. The latter lake systems represent spatial analogues to the conditions at Lake El'gygytgyn during MIS 5e and 11c, respectively. We analyzed anhydrosugars using ultra high-performance liquid chromatography coupled to a high-resolution mass spectrometer. We discuss the modern anhydrosugar concentrations and isomer ratios in context of (1) well-explored modern lake and catchment configurations and (2) multiple late glacial to interglacial results of Lake El'gygytgyn sediment cores. By better constraining the sources and (degradation) pathways that determine the proxy meaning of sedimentary anhydrosugars in northeastern Siberia, we provide a step forward to understand the regional pyrogenic carbon cycle and long-term feedbacks that are crucial for model predictions of future fire regime shifts in the high northern latitudes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8019

2020059450 Douglas, Thomas (U. S. Army Cold Regions Research and Engineering Laboratory, Fort Wainwright, AK); Hiemstra, Christopher; Anderson, John and Zhang, Caiyun. Identifying vegetation-geomorphology relationships in permafrost with airborne LiDAR, electrical resistivity tomography, seasonal thaw depth measurements, and machine learning [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1900, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Mean annual temperatures in interior Alaska, currently -1°C, are projected to increase as much as 5°C by 2100. An increase in mean annual temperatures is expected to degrade permafrost and alter hydrogeology, soils, vegetation, and microbial communities. Ice and carbon rich "yedoma type" permafrost in the area is ecosystem protected against thaw by a cover of thick organic soils and mosses. As such, interactions between vegetation, permafrost ice content, the snow pack, and the soil thermal regime are critical in maintaining permafrost. We studied how and where vegetation and soil surface characteristics can be used to identify subsurface permafrost composition. Of particular interest were potential relationships between permafrost ice content, the soil thermal regime, and vegetation cover. We worked along 400-500 m transects at sites that represent the variety of ecotypes common in interior Alaska. Airborne LiDAR imagery was collected from May 9-11, 2014 with a spatial resolution of 0.25 m. During the winters from 2013-2019 snow pack depths have been made at roughly 1 m intervals along site transects using a snow depth datalogger coupled with a GPS. In late summer from 2013-2019 maximum seasonal thaw depths have been measured at 4 m intervals along each transect. Electrical resistivity tomography measurements were collected across the site transects. A variety of machine learning geospatial analysis approaches were also used to identify relationships between ecosystem characteristics, seasonal thaw, and permafrost soil and ice composition. Wintertime measurements show a clear relationship between vegetation cover and snow depth. Interception (and shallow snow) was evident in the birch and white spruce forests and where dense shrubs are present while the open tussock and intermittent shrub regions yield the greatest snow depths. Results from repeat seasonal thaw depth measurements also show a strong relationship with vegetation where mixed birch and spruce forest is associated with the deepest seasonal thaw. The tussock/shrub and spruce forest zones consistently exhibited the shallowest seasonal thaw. Roughly 60% of the seasonal thaw along the transects occurred by mid-July and downward movement of the thaw front had mostly ceased by late August with little additional thaw between August 20 and early October. Summer precipitation shows a relationship with seasonal thaw depth with the wettest summers associated with the deepest thaw. Results from this study identify clear relationships between ecotype, permafrost composition, and seasonal thaw dynamics that can help identify how and where permafrost degradation can be expected in a warmer future arctic. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1900

2020059453 Draebing, Daniel (University of Bayreuth, Chair of Geomorphology, Bayreuth, Germany); Mayer, Till; Jacobs, Benjamin and McColl, Samuel. Identification of paraglacial and periglacial processes and resulting rockfall activity [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2157, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Rockfall is characteristic of deglaciated alpine rockwalls. Small (<5 km2) to very small (<0.5 km2) alpine glaciers are located at altitudes where periglacial and paraglacial processes jointly influence rockfall processes. In this study, we (i) reconstruct glacier retreat history, (ii) quantify rock fracture damage, (iii) model permafrost distribution, (iv) model patterns of frost weathering, and (v) assess how these may combine to influence rockfall processes around a small alpine glacier in the Hungerl Valley (Swiss Alps). To achieve this, we use geomorphic, geophysical, geotechnical and remote sensing techniques on three rockwalls (RW1-3) with different glacial retreat history and elevation. Glacier retreat is reconstructed based on existing LGM ice extent models, mapping of moraines and analysis of historic photos. The resulting retreat history is used as an upper age limit for the calculation of paraglacial rockwall retreat rates. Rockwall fracture damage is quantified in the field using laboratory-calibrated seismic refraction tomography and our results demonstrate that rockwall fracture density increases with proximity to the glacier. This relationship suggests that rockwalls in proximity to the glacier are still experiencing paraglacial stress-release jointing and that rockfall is yet to remove these fractured blocks. Local permafrost modelling based on temperature logger data indicates that areas with likely permafrost occurrence (<-3°C) are limited to the peaks and upper cirque walls (>3000 m). Areas of "possible" permafrost (<0°C) extend to elevations as low as 2700 m. We determined rock strength properties in the lab (Draebing and Krautblatter, 2019) and monitored rock temperature in the field for three years. These data were applied to the physical-based frost cracking model by Rempel et al. (2016). Model simulations show that frost cracking is highly sensitive to lithology and increases with altitude due to decreasing rock temperatures. We applied terrestrial laserscanning of the rockwalls to quantify rockfall activity. Rockfall volumes demonstrate a typical frequency-magnitude distribution. Applying a space-for-time substitution using glacier retreat history reveals that rockwall retreat rates are increased in proximity to the glacier where rockwalls experience permafrost and a high frost cracking intensity. In conclusion, our data suggest a synergy of paraglacial processes, frost cracking and permafrost thaw in preparing and triggering rockfalls. This synergy follows an altitudinal gradient that moves upwards with glacier retreat, permafrost thaw and frost cracking trajectories. Draebing, D., & Krautblatter, M.: The Efficacy of Frost Weathering Processes in Alpine Rockwalls. Geophysical Research Letters, 46(12), 6516-6524, 2019. Rempel, A. W., Marshall, J. A., & Roering, J. J.: Modeling relative frost weathering rates at geomorphic scales. Earth and Planetary Science Letters, 453, 87-95, 2016. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2157

2020059475 Dublyansky, Yuri (Innsbruck University, Institute of Geology, Innsbruck, Austria); Koltai, Gabriella; Scholz, Denis; Meyer, Michael; Gliganic, Luke; Kadebskaya, Olga; Cheng Hai and Spötl, Christoph. History of late Pleistocene permafrost in Southern Ural revealed by studies of speleothems and cave sediments [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4800, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In the area of the European-Asian border, in the Ural Mountains, the southern boundary of permafrost has moved in meridional direction by more than 1000 km in response to Quaternary climate variations. During cold climate states, permafrost extended as far south as the Southern Ural (53°N). We studied three independent archives in three caves in the Southern Ural (Shulgan-Tash, Victoria and Grandioznaya) in order to gain insights into the long-term dynamics of permafrost in the region. Common speleothems (e.g., stalagmites and flowstone) require liquid water to form, and are therefore restricted to permafrost-free periods. Cryogenic cave carbonates (CCC) form when the temperature in the cave is close to or slightly below 0°C (permafrost conditions). These two types of speleothems were dated using the 230Th-U method in order to determine the timing of permafrost and permafrost-free conditions. As a novel indicator of freezing conditions in caves we identified frost wedges in silty cave sediments filled by sand. These sands were dated using OSL to constrain the timing of sub-zero rock temperatures (required to form frost wedges) in caves. Stalagmites, abundant in in South Uralian caves, exhibit two prominent growth phases, associated with interglacials - MIS 5e and Holocene. In addition, mm-thin layers of flowstone formed in one chamber of Shulgan-Tash cave in association with smaller-scale warming episodes during MIS 3 (Greenland interstadials GI-9 and GI-8) and MIS 2 (GI-1; Bolling-Allerod). All CCC in Shulgan-Tash and Victoria caves yielded MIS 3 ages, typically lagging cooling events (Greenland stadials) GS-16.1, GS-15.1, GS-13, GS-12, GS-10, and GS-7 by several hundred years up to one 1 ka. CCC from Grandioznaya cave formed during a single episode following GS-1 (Younger Dryas). Sand filling frost wedges in Victoria cave was washed into the cave during MIS 2, ca. 24-25 ka BP. Apparently, during this time the karst massif hosting the cave was engulfed by permafrost (to a depth of at least 90 m) and flow of water through the cave was severely restricted, which led to back-flooding of the cave passage and the accumulation of several m-thick silt deposits, interspersed with thin sand layers. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4800

2020059519 Fleischer, Fabian (Catholic University of Eichstätt-Ingolstadt, Physical Geography Department, Eichstatt, Germany); Haas, Florian; Heckmann, Tobias; Altmann, Moritz; Piermattei, Livia; Rom, Jakob and Becht, Michael. Multi-decadal (1953-2017) response of rock glacier morphodynamics to climate change in the Kauner Valley in the Otztaler Alps, Austria based on historical aerial images and airborne LiDAR data [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8231, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Although the observed global climate change has particularly affected high-alpine regions and these geosystems seem to react very sensitively to changes in external forcing, there is a lack of understanding about the effect of a changing climate upon high-alpine landscapes at the timescale of decades. In the case of rock glaciers, which are common features in high alpine periglacial landscapes, numerous studies suggest a general acceleration of rock glacier displacement rates accompanied by surface lowering. This behaviour has been attributed to the rising permafrost temperature, induced by atmospheric warming and regulated by thermo-hydrological processes. On the other hand, decoupled kinematics of nearby rock glaciers under the same climatic forcing have also been proven. This is attributed to different local topo-climatic conditions and genesis of the investigated rock glaciers. To contribute to the understanding of multi-decadal rock glacier response to climate change, we investigate the morphodynamic changes for selected rock glaciers in the Upper Kauner Valley in the Otztaler Alps, Austria, a catchment comprising numerous rock glaciers of different size, genesis, elevation, aspect and activity status. This is done for multiple time slices between 1953 and 2017. These changes are analysed with respect to rock glacier characteristics and changes in the meteorological forcing. This work is part of the interdisciplinary and multi-university research project SEHAG (Sensitivity of high alpine geosystems to climate change since 1850), which aims to investigate changes in different processes of alpine geosystems and their interaction. In order to investigate morphodynamics of the rock glaciers, we use digital photogrammetry to generate orthophotos and digital elevation models from historical aerial images (available since 1953). Additionally, we use digital elevation models generated from three airborne LiDAR surveys within the period 2006-2017. While the diachronic analysis of digital elevation models predominantly addresses vertical surface changes, image correlation of multitemporal digital orthophotos yields information on rates of horizontal displacement. The results for the individual rock glaciers are compared to each other and to meteorological data of nearby weather stations to analyse the response of rock glaciers with different characteristics to changing climate forcing. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8231

2020059470 Fritz, Michael (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Permafrost Research, Potsdam, Germany); Grotheer, Hendrik; Meyer, Vera; Riedel, Thorsten; Pfalz, Gregor; Mathieu, Laura; Hefter, Jens; Gentz, Torben; Lantuit, Hugues and Mollenhauer, Gesine. Burial and origin of permafrost organic carbon in the Arctic nearshore zone [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4244, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Germany Increasing air and sea surface temperatures at high latitudes lead to accelerated thaw, destabilization, and erosion of perennially frozen soils (i.e., permafrost), which are often rich in organic carbon. Coastal erosion leads to an increased mobilization of organic carbon into the Arctic Ocean that can be converted into greenhouse gases and may therefore contribute to further warming. Carbon decomposition can be limited if organic matter is efficiently deposited on the seafloor, buried in marine sediments and thus removed from the short-term carbon cycle. Basins, canyons and troughs near the coastline can serve as sediment traps and potentially accommodate large quantities of organic carbon along the Arctic coast. Here we use biomarkers (source-specific molecules), stable carbon isotopes (d13C) and radiocarbon (D14C) to identify the sources of organic carbon in the nearshore zone of the southern Canadian Beaufort Sea. We use an end-member model based on the carbon isotopic composition of bulk organic matter to identify sources of organic carbon. Monte Carlo simulations are applied to quantify the contribution of coastal permafrost erosion to the sedimentary carbon budget. The models suggest that 40% of all carbon released by coastal erosion is efficiently trapped and sequestered in the nearshore zone. We conclude that permafrost coastal erosion releases huge amounts of sediment and organic matter into the nearshore zone. Rapid burial removes large quantities of carbon from the carbon cycle in depositional settings. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4244

2020059492 Fujii, Kazumichi (Forestry and Forest Products Research Institute, Japan); Matsuura, Yojiro; Inagaki, Yoshiyuki and Hayakawa, Chie. Uptake of urea by "drunken" trees on permafrost [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6271, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Boreal forest productivity on permafrost is limited by availability of soil nitrogen (N) in the active layer. Low soil temperature and summer flooding limit microbial N mineralization on shallow permafrost table. Uptake of amino acids by plant root-mycorrhizal association is known to mitigate N limitation in boreal forest soils. However, amino acid hypothesis can not fully explain advantage of black spruce trees in drunken forests due to competition of amino acids between plants, bryophytes, and microbes. Based on the observation of urea accumulation in deeper soil, we test another hypothesis that black spruce trees take up intact urea in deeper soil. Mixture solutions (glutamic acid, urea, ammonium, nitrate), with only one N form labeled by 13C and/or 15N, was injected into the organic/mineral soil layers. We compared two black spruce forest sites with/without shallow permafrost table in northern Canada. We found that black spruce trees take up intact urea as well as amino acids in the shallow permafrost sites. Urea accumulation is explained by low microbial activities to mineralize 14C-labeled urea. The other plants or bryophyte compete with black spruce for amino acids, but not for urea. Since the other black spruce trees in the deeper soil sites rely on amino acids and inorganic N, urea uptake strategy is specific to black spruce trees on shallow permafrost table. The root expansion on hummocky microrelief provides opportunity for leaning trees to access urea. The uptake of intact urea could be one of strategy of black spruce trees to mitigate N limitation in permafrost-affected hummocky soils. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6271

2020059442 Gagnon, Samuel (Université Laval, Centre d'études nordiques, Quebec, QC, Canada) and Allard, Michel. Modelled (1990-2100) variations in active-layer thickness and ice-wedge activity near Salluit, Nunavik (Canada) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1428, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Between 2016 and 2018, Gagnon and Allard (2019) investigated the impact of climate change on winter ice-wedge (IW) cracking frequency and IW morphology. In this study, they revisited 16 sites in the Narsajuaq valley (Canada) that were extensively studied between 1989 and 1991. Climate warming only started around 1993 whence mean annual air temperatures started to rise from -10 °C then to about -6 °C nowadays. This gave the unique opportunity to observe and measure changes by directly comparing field data with data pre-dating a climate warming of known amplitude. They found that based on IW tops, the active layer reached depths that were 1.2 to 3.4 times deeper than in 1991, which led to the widespread degradation of IW in the valley. Whereas 94% of the IWs unearthed in 1991 showed multiple recent growth structures, only 13% of the IWs unearthed in 2017 still had such features. However, about half of the IWs in 2017 had ice veins connecting them to the base of the active layer, an indication that the recent cooling trend (2010-now) in the region was enough to reactivate frost cracking and IW growth. This shows that the soil system can respond quickly to short-term climate variations. For this study, we aimed to determine how changes in surface temperatures affected active-layer thickness (ALT) and dynamics over the past 25 years in order to understand the timing and reaching times of ground temperature thresholds for soil cracking and IW degradation. We used TONE, a one-dimensional finite-element thermal model, to simulate ground temperatures over the past 25 years. A monthly mean air temperature from a reanalysis (1948-2016) was combined with data from a weather station about 9 km west of the study area (2002-2018) to simulate the soil temperature profiles of four typical soil types found in the valley: thick sandy peat cover, thick peat cover, thin sandy peat cover, and fluvial sands. Our results show that ALT variations were predominantly controlled by changes in thawing season air temperature with regards to the previous year. As soon as 1998, the active layer had already reached the main stages of the IWs, i.e. the largest and oldest part composing the IWs, but it is only from 2006 that the main stages started melt until 2010, an exceptionally warm year. Based on soil temperature thresholds, our results show that IWs remained active until around 2006. This means that as the active layer deepened and caused IW tops degradation, freezing season temperatures were still cold enough to induce soil cracking and IW growth in width. After 2010, the cooling trend was enough to reactivate the IWs from as a soon as 2011. This study shows that prior to advanced degradation, IWs can melt substantively and remain active at the same time as long as freezing season temperatures are cold enough to induce soil contraction cracking. However, it is likely that pulse events such as ground collapse will cause positive feedbacks contributing to rapid IW degradation before the soil completely stops cracking. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1428

2020059457 Giamberini, Mariasilvia (National Research Council of Italy, Institute of Geoscience and Earth Resources, Pisa, Italy); Baneschi, Ilaria; Lelli, Matteo; Magnani, Marta; Raco, Brunella and Provenzale, Antonello. A critical zone approach to carbon fluxes in the Arctic tundra [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2956, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic tundra is currently undergoing significant changes induced by the effects of a rapid temperature rise, that in the Arctic is about twice as fast as in the rest of the world. The response of the system composed by the permafrost active layer, soil and vegetation is especially relevant. In fact, it is still unclear whether the system will turn from a carbon sink to a carbon source, owing to the interplay of two opposite phenomena: the increasing time span of the growing season, favouring Net Ecosystem Production (NEP), and the increasing soil temperatures, favouring degradation of organic matter through heterotrophic respiration (HR) and then creating a positive climate feedback. In this work, we analyse soil-vegetation-atmosphere CO2 flux data of a field campaign conducted in the Bayelva river basin, Spitzbergen, in the Svalbard Archipelago (NO) during summer 2019, measured by a portable accumulation chamber. We use a "Critical Zone" perspective, considering the multiple interactions between biotic and abiotic components. We measured the Net Ecosystem Exchange (NEE) and Ecosystem Respiration (ER) along a slope gradient at different degrees of soil humidity and active layer depths, relating flux data to climate and environmental parameters, soil physical-chemical parameters and vegetation type. The statistical empirical relationships between variables are analysed to identify the main drivers of carbon exchanges. An empirical data-driven model is built to describe the coupled dynamics of soil, vegetation, water and atmosphere that contributes to budgeting the carbon cycle in the Arctic Critical Zone. A comparison of the carbon fluxes obtained with the accumulation chamber method and an Eddy Covariance tower located in the same area is also addressed. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2956

2020059433 Glückler, Ramesh (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Polar Terrestrial Environmental Systems, Potsdam, Germany); Herzschuh, Ulrike; Pestryakova, Luidmila; Kruse, Stefan; Vyse, Stuart; Andreev, Andrei and Dietze, Elisabeth. Late Holocene fire history documented at Lake Khamra, SW Yakutia (eastern Siberia) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1018, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Recent large-scale fire events in Siberia have drawn increased attention to boreal forest fire history. Boreal forests contain about 25% of all global biomass and act as an enormous carbon storage. Fire events are important ecological disturbances connected to the overarching environmental changes that face the Arctic and Subarctic, like vegetation dynamics, permafrost degradation, changes in soil nutrient cycling and global warming, and act as the dominant driver behind boreal forest's landscape carbon balance. By looking into past fire regimes we can learn about fire frequency and potential linkages to other environmental factors, e.g. fuel types, reconstructed temperature/humidity or geomorphologic landscape dynamics. Unfortunately, fire history data is still very sparse in large parts of Siberia, a region strongly influenced by climate change. The Global Charcoal Database (www.paleofire.org) lists only a handful of continuous charcoal records for all of Siberia, with only three of those featuring published data from macroscopic charcoal as opposed to microscopic charcoal from pollen slides. We aim to reconstruct the late Holocene fire history using lacustrine sediments of Lake Khamra (SW Yakutia at N 59.99°, E 112.98°). It covers an area of c. 4.6 km2 with about 22 m maximum water depth, located within the zone of transition from summer-green and larch-dominated to evergreen boreal forest. We present the first continuous, high-resolution (c. 10 years/sample) macroscopic charcoal record (> 150 mm) including information on particle size and morphology for the past c. 2200 years. We compare this to complementary information from microscopic charcoal in pollen slides, a pollen and non-pollen palynomorph record as well as mXRF data. This multi-proxy approach adds valuable data about fire activity in the region and allows a comparison of different prevalent fire reconstruction methods. As the first record of its kind from Siberia, it provides a long-term context for current fire activity in central Siberian boreal forests and enables a better understanding of the environmental interactions occurring in the changing subarctic landscape. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1018

2020059452 Grant, Robert (University of Alberta, Department of Renewable Resources, Edmonton, AB, Canada). Climate change impacts on CO2 and CH4 exchange in an Arctic polygonal tundra depend on changes in vegetation and drainage [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2027, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Model projections of CO2 and CH4 exchange in Arctic tundra during the next century diverge widely. In this modelling study, we used ecosys to examine how climate change will affect CO2 and CH4 exchange through its effects on net primary productivity (NPP), heterotrophic respiration (Rh) and thereby on net ecosystem productivity (NEP) in landform features (troughs, rims, centers) of a coastal polygonal tundra landscape at Barrow AK. The model was shown to simulate diurnal and seasonal variation in CO2 and CH4 fluxes associated with those in air and soil temperatures (Ta and Ts) and soil water contents (q) under current climate in 2014 and 2015. During RCP 8.5 climate change from 2015 to 2085, rising Ta, atmospheric CO2 concentrations (Ca) and precipitation (P) increased NPP from 50-150 g C m-2 y-1, consistent with current biometric estimates, to 200-250 g C m-2 y-1, depending on feature elevation. Concurrent increases in Rh were slightly smaller, so that net CO2 exchange rose from values of -25 (net emission) to +50 (net uptake) g C m-2 y-1 to ones of -10 to +65 g C m-2 y-1, again depending on feature elevation. Large increases in Rh with thawing permafrost were not modelled. Increases in net CO2 uptake were largely offset by increases in CH4 emissions from 0-6 g C m-2 y-1 to 1-20 g C m-2 y-1, depending on feature elevation, reducing gains in NEP. Increases in CH4 emissions with climate change were mostly attributed to increases in Ta, but also to increases in Ca and P. These increases in net CO2 uptake and CH4 emissions were modelled with hydrological boundary conditions that were assumed not to change with climate. Both these increases were smaller if boundary conditions were gradually altered to increase landscape drainage during model runs with climate change. The model was then applied to the entire permafrost zone of North America to project RCP 8.5 climate change effects on active layer depth and ecosystem productivity by 2100. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2027

2020059498 Grebenets, Valery (Moscow State University, Department of Cryolithology and Glaciology, Moscow, Russian Federation); Iurov, Fedor and Tolmanov, Vasily. Negative changes in permafrost due to waste storage [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6824, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The problem of waste storage is particularly acute in Arctic. This is due to the vulnerability of northern ecosystems, the existence of permafrost, especially vulnerable to anthropogenic impact, the water-resistant properties of frozen rocks and the effect of destructive cryogenic processes. In addition, the causes of concern are the trends in air and frozen soil temperatures reported for the northern regions: pollutants stored in relatively stable frozen state can be released into the environment as a result of thawing. This is especially true for industrial regions, where billions of cubic meters of waste from the mining and beneficiation of ores and coal, form timber processing, mine water spills and drilling fluids, etc. are stored in a frozen state. Field investigations were carried out in number of settlements in cryolithozone of Russia (Norilsk, Vorkuta, Igarka, settlements in the lower Ob, national villages of Taimyr, etc.). The observations involved remote sensing methods and included estimation of the area of littering and the types of waste. In many cases sampling for chemical analyzes, thermometry, and mapping of hazardous processes were made. The impact of stored wastes on permafrost was divided into three main types: a) mechanical (changing the relief and the flow paths of surface and ground waters); b) physical and chemical (pollution by the waste itself and by its decomposition products); c) thermal (heating of frozen soils by high-temperature waste or heat generation during various chemical reactions). During the research, 6 main types of waste storage were identified, each of which had a destructive effect on permafrost soils and northern ecosystems: dumps of municipal solid waste (inherent in all settlements); storages of industrial waste, tailing storage facilities in the industrial centers of the north; abandoned and cluttered territories; landfills of timber processing waste in the centers of the timber industry; rock dumps in open-cast mining sites, which in the cold climate can transform into rock glaciers; storage areas for polluted snow transferred from built-up areas. Particular attention was paid to the accumulation of chemical pollutants in industrial centers (with Norilsk industrial region as an example). This problem in conditions of permafrost is exacerbated by the low self-purification of northern biogeocenoses; slowdown of oxidation and some other chemical reactions in cold climates; drainage and unloading of groundwater of seasonally thawed layer, intra-permafrost and under-permafrost taliks into the water bodies. The use of imperfect technologies for the extraction and processing the raw materials, remains of past years practices with neglected environmental situation, the lack of special standards for the storage of waste and industrial by-products, the lack of development of waste disposal methods for severe climatic conditions led to the pollution of vast territories and to destruction of many ecosystems. This work was supported by the RFBR grant 18-05-60080 "Dangerous nival-glacial and cryogenic processes and their impact 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-egu2020-6824

2020059476 Grenier, Christophe (Institut Pierre Simon Laplace, Laboratoire des Sciences du Climat et de l'Environnement (LSCE / IPSL), Gif sur Yvette, France) and Costard, Francois. InterFrost Project; Phase 2, Updated experiment results for the validation of cryohydrogeological codes (frozen inclusion) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4865, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Recent field and modelling studies indicate that a fully-coupled, multi-dimensional, thermo-hydraulic (TH) approach is required to accurately model the evolution of permafrost-impacted landscapes and groundwater systems. However, the relatively new and complex numerical codes being developed for coupled non-linear freeze-thaw systems require validation. This issue was first addressed within the InterFrost IPA Action Group, by means of an intercomparison of thirteen numerical codes for two-dimensional TH test cases (TH2 & TH3). The main results (cf. Grenier et al. 2018 and wiki.lsce.ipsl.fr/interfrost) demonstrate that these codes provide robust results for the test cases considered. The second phase of the InterFrost project is devoted to the simulation of a cold-room reference experiment based on test case TH2 (Frozen Inclusion). In a first implementation phase of the experimental setup, the initial frozen inclusion was inserted in the setup prior to the complete filling of the porous medium and the flow initiation. The thermal evolution of the system was monitored by thermistors located at the center of the initial inclusion and along the downgradient centerline. This setup provided optimal conditions to control the initial experiment geometries but resulted in slight differences in the initialization time for different experiments. In a second implementation strategy, we now consider "in place" generation of an initial frozen inclusion through a cooling coil. The initial frozen inclusion is obtained after the initial cooling time and its initial thermal state is measured by means of an array of thermistors. In a second step, the flow is initiated, and the thermal evolution is monitored through an array of 11 thermistors (within the initial position and downgradient). The experimental setup and an overview of all monitoring results as well as preliminary numerical simulations are presented. In an attempt to prevent formerly observed drifts in total water flow rates, the porous medium is renewed for each single experiment considering some key experimental conditions (full-flow vs. no-flow). A repetition of experiments provides an estimation of experimental uncertainty bounds. Derived results and conclusions from this experiment will form the basis for the next phase within the InterFrost validation exercise. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4865

2020059482 Groos, Alexander Raphael (University of Bern, Institute of Geography, Bern, Switzerland); Niederhauser, Janik; Akcar, Naki and Veit, Heinz. The enigma of large sorted stone stripes in the tropical Ethiopian Highlands [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5552, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Bale Mountains in the southern Ethiopian Highlands (7-8°N) are formed of multiple superimposed flood basalts and comprise Africa's largest plateau above 4000 m. Glacial and periglacial landforms are well-preserved and facilitate the reconstruction of the paleoclimate and landscape of the afro-alpine environment. During the Late Pleistocene, an ice cap covered the central part of the plateau and outlet glaciers extended down into the northern valleys. A striking geomorphological feature on the plateau are large sorted stone stripes that consist of hardly-weathered columnar basalt and are up to 2 m deep, 15 m wide and 200 m long. The stone stripes are located between 3850 and 4050 m at gentle slopes (4-8°) of two volcanic plugs 3-5 km south of the highest peak (Tullu Dimtu, 4377 m) and in the far west of the plateau. Sorted patterned grounds of similar size are characteristic for periglacial environments of the high latitudes, but unique for tropical mountains since their formation requires permafrost and a deep active layer. While diurnal freeze-thaw cycles in tropical mountains are sufficient for the genesis of small-scale patterned grounds, the sorting of large basalt columns (length >2 m, diameter >40 cm) assumes seasonal (or multi-annual) freeze-thaw cycles and a deep active layer. When and under which climatic conditions the sorted stone stripes in the Bale Mountains formed, remains an unsolved mystery. The stone stripes might have developed during the Late Pleistocene under periglacial conditions in close proximity to the ice cap or after deglaciation (~15-14 ka). To assess the timing of the final stagnation of the stone stripes, we determined the age of six basalt columns from two different stripes using 36Cl surface exposure dating. In addition, we installed temperature data logger in 2, 10 and 50 cm depth across the plateau and between the stone stripes to investigate the present thermal conditions and diurnal and seasonal temperature variations in the ground. The difference between the measured mean annual temperature and presumed average ground temperature for permafrost (≤&eq;0°C) indicates an extreme temperature depression on the plateau of >&eq;10°C during the formation period of the sorted stone stripes. Such a Late Pleistocene cooling would be unprecedented in the tropical mountains. Finally, we applied a simple statistical model forced with meteorological data from a nearby weather station to simulate ground temperatures and test which climatic preconditions are necessary for the formation of sporadic permafrost in the Bale Mountains. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5552

2020059446 Gu Jing (Nanjing University, Joint International Research Laboratory of Atmospheric and Earth System Sciences, Nanjing, China); Pang Qiaotong; Ding Jinzhi; Yin Runsheng; Yang Yuanhe and Zhang Yanxu. The storage and influencing factors of mercury in the permafrost of the Tibetan Plateau [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1598, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Soil is one of the largest reservoir of mercury in the environment. Globally, most of the mercury in the soil is stored in permafrost, such as the Arctic and the Tibetan Plateau. Mercury in the soil is mainly derived from atmospheric deposition and tightly bound to the organic carbon. The mercury level in the permafrost over the Tibetan Plateau and its influencing factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in meadow soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric mercury deposition. The relationship between STHg and soil organic carbon (OCD) as well as atmospheric deposition are explored. We also extend our analysis to data in the Tibetan Plateau and other regions of China in the literature. Our results show that the STHg concentrations in the Tibetan Plateau are 19.9±12.4 ng/g. The concentrations are higher in the south/east and lower in the north/west in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 ug m-2 yr-1 with 57% contributed by dry deposition of Hg0, followed by dry deposition of HgII and HgP (19%) and wet deposition (24%). We calculate the Hg to carbon ratio (RHgC) of 5.52 ± 5.11 mg Hg/g C and the estimated STHg is 67.45 Gg in alpine grasslands in the Tibetan Plateau, contributing about 2.7% globally. We find a positive correlation between OCD and STHg in the Tibetan Plateau (Log(STHg) = 0.35 log(OCD) + 0.99, R2 = 0.24) and a weak relationship between model residual (defined as the difference between model fitting values and observations) and atmospheric total Hg deposition. We conclude that soil organic carbon (SOC) and atmospheric deposition work simultaneously for STHg. Atmospheric deposition determines the potential levels of STHg in large spatial scales, while SOC and its characteristics modulate STHg locally by influencing the fate and transport of Hg. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1598

2020059502 Hendrickx, Hanne (Ghent University, Geography Department, Gent, Belgium); Delaloye, Reynald; Nyssen, Jan and Frankl, Amaury. Recent geomorphic destabilization of mountain slopes, a possible link to climate change? Two case studies from Switzerland [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7037, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Geomorphological destabilisations in high mountain areas are often linked to permafrost degradation and changing precipitation intensities, induced by climate change. Considering the complex interaction between meteorological conditions, geology and topography, two alpine mass movements that took place in 2019 in the canton of Valais (Swiss Alps) were investigated with regard to their possible causes. During three consecutive summers (2017-2019), independent surveys were carried out on a high alpine talus slope at Col du Sanetsch (2100-2750 m a.s.l.) and an unstable rock face at Grosse Grabe, Mattertal (2600-2700 m a.s.l.), using unmanned aerial vehicle (UAV) and terrestrial laser scanning (TLS). The resulting high-resolution topography allows detecting and quantifying small and large geomorphic changes, such as rock tilting, rockfalls, rockslides, erosion and depositions of rock debris by snow avalanche action, debris channel cutting and fill and debris flow deposits. In both study areas, the summer of 2019 was characterized by mass movement events of greater magnitude than the geomorphic activity measured in the summers before. At Grosse Grabe, the rock face was observed by webcam imagery since 2011, in the background of a rock glacier, which was initially the main object of survey. Isolated rock falls started in January 2017, launching a more accurate survey of the rock face by TLS in July 2017. In the next two summers, the entire unstable part of the rock wall, 70 m high, had been tilting at an increasing rate (1 to 3.3 cm/month). From mid-July until the end of October 2019, consecutive large rock fall events (up to > 10,000 m3) lead to the complete collapse of the monitored rock face (5000 m2), with a total volume of more than 60,000 m3. After the collapse of this heavily fractured, south facing rock face, the long-lasting wet rockfall scar indicated the presence of thawing permafrost ice. Beside the geological characteristics, which are favouring the rock wall instability, the consequences of the multi-decennial significant warming of the permafrost is presumably an implicated factor. On the talus slope (2 km2) that was surveyed at Col du Sanetsch, a large debris flow event (ca. 20,000 m3 spread over multiple debris flow channels) was observed in the evening of 11 August 2019. Most of the mobilized sediments originated from incision of the talus apex area, while only a small part came from intermediate debris storage within rock wall gullies. An analysis of historical aerial photographs shows that the total displaced volume during the 2019 event exceeds each historical debris flow event that occurred on the talus slope since 1946. In contrast to Grosse Grabe, where weather conditions have played no role on the development of the instability, the debris flow event at Col de Sanetsch is linked to an intense prefrontal supercell, causing rainfall intensities between 10 and 25 mm/h, in some places in less than 15 minutes. As such events are presumed to become more frequent with climate change, more debris flow events of this type can be expected in the future. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7037

2020059428 Hille, Erika (Aurora College, Aurora Research Institute, Inuvik, Canada); McAlister, Joel; Wilson, Alice and Kokelj, Steve. Community engagement in permafrost research at the Western Arctic Research Centre, Inuvik, Northwest Territories, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-591, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic is experiencing climate warming at a more pronounced rate than other regions. This has significant implications for the thermal stability of permafrost, which strongly depends on the long, cold winters typical of the region. Canada's western Arctic is typically more sensitive to permafrost thaw than other Arctic regions in Canada, because it is underlain by large regions of ice-rich permafrost that are only protected by a thin layer of organic and mineral soil. As a result, disturbances (i.e. fire, shallow landslides, thermal and mechanical erosion, construction) often lead to the exposure and thaw of the underlying permafrost. Climate-induced permafrost thaw has led to dramatic changes to the landscape, impacting communities, infrastructure, and traditional ways of being. In this region, northern stakeholders have invested in research infrastructure that enables them to actively participate in research, research design and implementation, and lead their own research programs. Since permafrost is intrinsically linked to the social, cultural, and economic fabric of the region, it is critical that local stakeholders be engaged in permafrost research. The Western Arctic Research Centre (WARC) is located in Inuvik, Northwest Territories, Canada. Inuvik is situated in the Beaufort Delta Region of Northwestern Canada, approximately 120 km from the Arctic Ocean. A key goal of WARC is to support and conduct research that fosters the social, cultural, and economic prosperity of the people of the Northwest Territories. In response to local concerns, WARC has developed a suite of research programs that focus on the impacts of permafrost thaw on terrestrial, freshwater, and marine systems. To ensure that these research programs are responsive to the concerns of northern and Indigenous residents, WARC works in partnership with researchers, communities, government bodies, and Indigenous and co-management organizations. Project partners provide critical feedback on research design, study site selection, and how to communicate research to a northern audience. Furthermore, the Permafrost Information Hub at WARC is working with local organizations to establish community-based permafrost research and monitoring in the Beaufort Delta Region. This includes the development and delivery of training programs for local environmental monitors, increasing capacity in the region to support permafrost research. Northerners need to be involved in permafrost research. How Northerners want to be involved will differ depending on the location within the region and the nature of the research. This emphasizes the need for consistent, open lines of communication between researchers and local partners. This oral presentation will outline the steps WARC has taken to engage northern and Indigenous residents in its permafrost research programs, lessons learned, and successes. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-591

2020059522 Hjort, Jan (University of Oulu, Geography Research Unit, Oulu, Finland); Karjalainen, Olli; Aalto, Juha; Westermann, Sebastian; Romanovsky, Vladimir; Nelson, Frederick; Etzelmüller, Bernd and Luoto, Miska. Degrading permafrost threatens Arctic nature and built environment [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8408, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic earth surface systems are undergoing unprecedented changes, with permafrost thaw as one of the most striking examples. Permafrost is critical because it controls ecosystem processes, human activities, and landscape dynamics in the north. Degradation (i.e. warming and thawing) of permafrost is related to several hazards, which may pose a serious risk to humans and the environment. Thaw of ice-rich permafrost increases ground instability, landslides, and infrastructure damages. Degrading permafrost may lead to the release of significant amounts of greenhouse gases to the atmosphere and threatens also biodiversity, geodiversity and ecosystem services. Thawing permafrost may even jeopardize human health. Consequently, a deeper understanding of the hazards and risks related to the degradation of permafrost is fundamental for science and society. To address climate change effects on infrastructure and human activities, we (i) mapped circumpolar permafrost hazard areas and (ii) quantified critical engineering structures and population at risk by mid-century. We used observations of ground thermal regime, geospatial environmental data, and statistically-based ensemble methods to model the current and future near-surface permafrost extent at ca. 1 km resolution. Using the forecasts of ground temperatures, a consensus of three geohazard indices, and geospatial data we quantified the amount and proportion of infrastructure elements and population at risk owing to climate change. We show that ca. 70% of current infrastructure and population in the permafrost domain are in areas with high potential for thaw of near-surface permafrost by 2050. One-third of fundamental infrastructure is located in high hazard regions where the ground is susceptible to thaw-related ground instability. Owing to the observed data-related and methodological limitations we call for improvements in the circumpolar hazard mappings and infrastructure risk assessments. To successfully manage climate change impacts and support sustainable development in the Arctic, it is critical to (i) produce high-resolution geospatial datasets of ground conditions (e.g., content of organic material and ground ice), (ii) develop further high-resolution permafrost modelling, (iii) comprehensively map permafrost degradation-related hazards, and (iv) quantify the amount and economic value of infrastructure and natural resources at risk across the circumpolar permafrost area. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8408

2020059478 Hoelzle, Martin (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Barandun, Martina; Saks, Tomas; Azisov, Erlan; Gafurov, Abror; Ghirlanda, Alyssa; Kayumov, Abdulhamid; Kenzhebaev, Ruslan; Kronenberg, Marlene; Machguth, Horst; Mamirov, Halim; Moldobekov, Bolot; Petrov, Maxim; Salzmann, Nadine; Usubaliev, Ryskul; Yakovlev, Andrey and Zemp, Michael. Glacier monitoring, capacity building and related cryospheric research in Central Asia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5135, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Climate change is a major challenge for humanity and the related global implications will influence and threaten future economies and livelihood of coming generations, especially in developing countries. Central Asia is one of the regions mostly vulnerable to climate change considering its hydrological constraints. Tien Shan and Pamir, are among the largest mountain systems of the world, and play a significant role in serving water to the arid and continental region. Future water resources in Central Asia depend strongly on the cryosphere, particularly on snow, glaciers and permafrost. These cryospheric components store enormous amounts of fresh water and under the ongoing climate warming, expected changes will play an important role for future water availability in the region. Recent research clearly points out that a) for current climate conditions, water release by the cryosphere, particularly glaciers, is fundamental to keep runoff sufficient during the dry summer months and b) at the end of this century the water contribution of glaciers will be drastically reduced. Certain catchments are expected to completely dry-out. This setting creates a complex set of future challenges in the domains of water management, energy production, irrigation, agriculture, environment, disaster risk reduction, security and public health and potential political tension and conflicts between the countries cannot be excluded. Notably, climate change also poses challenges in the field of climate services, as the lack of reliable data and commitment of the governments to fully integrate their observatory systems inhibits the sustainable adaptation and development of the region. At this point, the project CICADA (Cryospheric Climate Services for improved Adaptations) is currently contributing to the improvement of the Cryospheric Climate Services in the Central Asian countries by installing modern monitoring infrastructure, by training local students and researchers and by using the collected in situ measurements in combination with remote sensing and modelling to provide climate scenarios and services for water runoff and natural hazards. This is a prerequisite to allow early planning and adaptation measures within the water resource management and disaster risk reduction sectors. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5135

2020059514 Hoelzle, Martin (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Hauck, Christian; Noetzli, Jeannette; Pellet, Cécile and Scherler, Martin. Long-term energy balance measurements at three different mountain permafrost sites in the Swiss Alps [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8076, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The surface energy balance is one of the most important influencing factors for the ground thermal regime. It is therefore crucial to understand the interactions of the individual heat fluxes at the surface and within the subsurface layers as well as their relative impacts. A unique set of high-altitude meteorological measurements has been analysed to determine the energy balance at three mountain permafrost sites in the Swiss Alps, where data is being collected since the late 1990s in collaboration with the Swiss Permafrost Monitoring (PERMOS). The three stations have a standardized equipment with sensors for four-component radiation, air temperature, humidity, wind speed and direction as well as ground temperatures and snow height. The three sites differ considerably by their surface and ground material composition ranging from a coarse blocky active layer above ice supersaturated permafrost at rock glacier Murtèl-Corvatsch to deeply weathered micaceous shales, which are covered by fine grained debris of sandy and silty material with a low ice content at the Northern slope of Schilthorn summit. The third site at the Stockhorn plateau shows intermediate ice contents and heterogeneous surface conditions with medium-size debris, fine grained material and outcropping bedrock. Ice content estimation and general ground characterisation are based on geophysical surveying and borehole drilling. The energy fluxes are calculated based on around two decades of field measurements. While the determination of the radiation budget and the ground heat flux is comparatively straightforward (by the four-component radiation sensor and thermistor measurements within the boreholes, respectively), larger uncertainties exist for the determination of sensible and latent turbulent heat fluxes. They are therefore determined on the one hand by the bulk aerodynamic method using the bulk Richardson number to describe the stability of the surface layer relating the relative effects of buoyancy to mechanical forces and on the other hand by the bowen ratio method. Results show that mean air temperature at Murtèl-Corvatsch (1997-2018, elevation 2600 m asl.) is -1.66°C and has increased by about 0.7°C during the observation period. The Schilthorn (1999-2018, elevation 2900 m asl.) site shows a mean air temperature of -2.48°C with a mean increase of 1.0°C and the Stockhorn (2003-2018, elevation 3400 m asl.) site shows lower air temperatures with a mean of -5.99°C with an increase of 0.6°C. Measured net radiation, as the most important energy input at the surface, shows substantial differences with mean values of 33.41 Wm-2 for Murtèl-Corvatsch, 40.65 Wm-2 for Schilthorn and 24.88 Wm-2 for Stockhorn. The calculated turbulent fluxes show values of around 7 to 12 Wm-2 using the bowen ratio method and 8 to 18 Wm-2 using the bulk method at all sites. Large differences are observed regarding the energy used for melting of the snow cover: at Schilthorn a value of 12.41 Wm-2, at Murtèl-Corvatsch of 7.31 Wm-2 and at Stockhorn of 3.46 Wm-2 is calculated reflecting the differences in snow height at the three sites. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8076

2020059499 Hu Yufeng (Chang'an University, Xi'an, China). Ground surface elevation changes estimated using multiple GNSS signal-to-noise ratio observations over permafrost area [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6841, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The ground surface over permafrost area subsides and uplifts annually due to the seasonal thawing and freezing of active layer. GPS Interferometric Reflectometry (GPS-IR) has been successfully applied to the signal-to-noise ratio (SNR) observations to retrieve elevation changes of frozen ground surface at Barrow, Alaska. In this study, the method is extended to include GLONASS and Galileo SNR observations. Based on the multiple SNR observations collected by SG27 in Barrow, the multiple GNSS-IR time series of ground surface elevation changes during snow-free days from late June to middle October in year 2018 are obtained at daily intervals. All the three time series show a similar pattern that the ground subsided in thaw season followed by uplifts in freezing season, which is well characterized by the previous composite physical model using thermal indexes. Fitted with the composite model, the amplitude of the GPS-derived elevation changes during the snow-free days is suggested to be 3.3 ± 0.2 cm. However, the time series of GLONASS-IR and Galileo-IR measurements are much noisier than that of GPS-IR due to their inconsistent daily satellite tracks. Applied with a specific strategy in the composite model fitting, the amplitudes of GLONASS- and Galileo-derived elevation changes are estimated to be 4.0 ± 0.3 cm and 3.9 ± 0.5 cm, respectively. Then, GLONASS-IR and Galileo-IR time series are reconstructed in turn with the fitting coefficients. Moreover, the occurrences of the short-term variations in time series of GNSS-IR measurements are found to coincidence with the precipitation events, indicating the hydrologic control on the movements of frozen ground surface. The results presented in this study show the feasibility to combine multiple GNSS to densely monitor frozen ground surface deformations, and provide an insight to understand the impacts of both thermal and hydrologic forces on the frozen ground dynamics. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6841

2020059497 Iurov, Fedor (Lomonosov Moscow State University, Cryolithology and Glaciology, Moscow, Russian Federation) and Grebenets, Valery. Bearing capacity of frozen soils for foundations of objects in the north of western Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6695, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The North of Western Siberia is a very promising region for industrial development. It is rich in oil and gas deposits, large settlements are located here and there is an extensive system of transport infrastructure (gas and oil pipelines, roads and railways). The territory has very differentiated permafrost-geological conditions in various types of landscapes. The development of new production sites, the construction and operation of infrastructure objects often activates dangerous cryogenic processes. Trends in increasing air temperatures result in increase in the active layer depth, which leads to the decrease in the freezing area of frozen foundations, as well as in increase of the soil temperature, which reduces the forces of freezing. The problem is enhanced by the anthropogenic impact, which intensifies the negative changes in permafrost. Quantitative estimation of changes in the bearing capacity of frozen pile foundations in the North of Western Siberia was carried out up to 2050 for various types of soils (sand, clay soils, peat) with trends in increasing temperatures of frozen soils and trends in increasing thickness of the active layer taken into account. Detailed calculations were carried out for the route of the "Vankor-Purpe" oil pipeline. The calculations showed that maintaining current rate of climate warming, by 2050, there will be significant deterioration of the engineering-geocryological situation. The largest negative changes will take place in the southern part of the permafrost zone of Western Siberia (in the Tazovsky, Novourengoysky and Nadymsky districts), where the decrease in bearing capacity will exceed 50%. In the more northern regions (on the territory of Yamal), the predicted changes in the bearing capacity of frozen pile foundations by 2050 will not be so critical (no more than 20%). However, an increase in the thickness of the active layer can cause activation of the thermokarst process due to closeness of the thick stratal ice to the surface, as well as other destructive cryogenic processes. In the region of investigation, under the influence of rising soil temperatures and an increase in the depth of seasonal thawing, the most vulnerable to climatic changes are loamy soils, which, according to the calculations, are characterized by the maximum decrease in the bearing capacity of frozen piles (up to 10% over 10 years). Sandy soils are more stable, a decrease in bearing capacity occurs in such areas at a lower speed (up to 5-7% over 10 years). Areas with moss-peat layer at the surface are less susceptible to changes in bearing capacity, however, with industrial methods of foundation construction, the layer is destroyed in places where the piles are built. This work was supported by the RFBR grant 18-05-60080 "Dangerous nival-glacial and cryogenic processes and their impact 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-egu2020-6695

2020059484 Jiskra, Martin (University of Basel, Environmental Geosciences, Basel, Switzerland); Sonke, Jeroen E.; Lim, Artem G.; Loiko, Sergey V.; Kosykh, Natalia; Pokrovsky, Oleg; Agnan, Yannick; Helmig, Detlev and Obrist, Daniel. The role of permafrost soils in Arctic mercury cycling; source tracing with Hg stable isotopes and revised soil pool estimate [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5734, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Mercury (Hg) is a pollutant of great concern for indigenous populations in the Arctic, which are exposed to high dietary Hg from fish and marine mammal consumption. Hg in marine biota can be derived from direct atmospheric deposition to the Arctic Ocean or from terrestrial sources by river runoff. Permafrost soils thereby play a pivotal role in the Arctic Hg cycle by storing atmospheric Hg deposition and providing a reservoir for later mobilization to the Arctic Ocean. The stability of Hg in permafrost soils depends on the pathway of atmospheric Hg deposition and Hg release processes, i.e. reduction and re-emission to the atmosphere and transfer to river runoff. We combined Hg stable isotope with Hg flux measurements in a field study on the Arctic Coastal Plain in northern Alaska. We could show that gaseous elemental Hg uptake by vegetation represents 70% of total atmospheric Hg deposition. Atmospheric Hg uptake by vegetation results in a characteristic Hg isotope fingerprint. This fingerprint dominates Hg signatures in permafrost soils measured across the Arctic coastal plain and is also imprinted in marine mammals and Ocean sediments, suggesting that Hg from Arctic permafrost soils represent a major source to the Arctic Ocean. Knowing the pool and spatial distribution of Hg in permafrost soils is therefore essential to assess current Hg mobilization to aquatic ecosystems and potential future changes due to permafrost thaw and climate change. Two recent studies have used Hg to carbon (C) ratios, RHgC, measured in Alaskan permafrost mineral and peat soils, together with a northern soil carbon inventory, to estimate that these soils contain large amounts, 184 to 755 Gg of Hg in the upper 1 m. In a second part, we present new Hg and C data for six peat cores, down to mineral horizons, across a latitudinal permafrost gradient in the Western Siberian lowlands. Hg concentrations increase from south to north in all soil horizons, reflecting enhanced net accumulation of atmospheric gaseous elemental Hg by the vegetation Hg pump. We reviewed and estimate pan-arctic organic and mineral soil RHgC to be 0.19 and 0.77 Gg Pg-1, and use a soil C budget to revise the northern soil Hg pool to be 67 Gg (37-88 Gg, interquartile range (IQR)) in the upper 30 cm and 225 Gg (102-320 Gg, IQR) in the upper 1 m. Finally, we discuss how climate change may affect the mobilization of Hg from permafrost soils to the atmosphere and the Arctic Ocean. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5734

2020059424 Jones, Melissa Ward (McGill University, Department of Geography, Montreal, QC, Canada); Jones, Benjamin and Pollard, Wayne. Daily monitoring of retrogressive thaw slumps in the Fosheim Peninsula, Ellesmere Island, Canada [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-360, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Retrogressive thaw slumps (RTS) occur from the mass wasting of ice-rich permafrost. These horseshoe-shaped features have an ablating or retreating ice-rich headwall with fluidized sediment that is transported along the RTS floor. RTS can remain active for up to decades and enlarge as the headwall retreats. With observed increases in RTS number, rates and sizes in recent decades, there is a need to understand these highly dynamic landforms, however there is a general lack of detailed field observations of RTSs. We monitored 3 RTS for over half of the 2017 thaw period by setting up and tracking survey transects on a near daily basis. We correlated mean daily and cumulative retreat to mean daily air temperature (MDAT), total daily precipitation (TDP) and thawing degree days (TDD) using various polynomial regressions and Pearson correlation techniques. Our results show that July retreat was highly variable and periods of increased RTS retreat did not always align with periods of increased air temperature. Also, multiple periods of increased retreat could occur within a single period of increased air temperature. These retreat trends were observed to be largely driven by sediment redistribution in the RTS floor. Retreat rates decreased suddenly in early August, indicating a threshold of either air temperature, solar radiation or a combination of both must be reached for increased retreat rates. There was a statistically significant correlation between daily mean and mean cumulative retreat with MDAT (p < 0.001) and TDD (p < 0.001 and < 0.0001) but not with TDP. Correlating mean cumulative retreat and cumulative TDD using polynomial regression (quadratic and cubic) generated R2 values greater than 0.99 for all 3 sites as these variables account for past and current conditions within the monitoring period, as well as lag responses of retreat. This suggests the potential of accurately modelling RTS retreat with minimal field data (air temperature and headwall position), however this is currently restricted to individual RTSs and only within short time scales. We tested this idea by modelling 2 weeks of cumulative retreat in 2018 for 2 of our sites we monitored using the 2017 regression equations. Percent prediction error was 8% at one site and 16% at the other. Monitoring RTS on a daily scale allows RTS behaviour and trends to be identified that may be obscured at annual time scales. With the widespread increased numbers of RTSs being observed around the Arctic, understanding their dynamics is critical as these landforms impact surrounding ecosystems and infrastructure which will be exacerbated with climate change. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-360

2020059504 Jong, Dirk (Vrije Universiteit, Amsterdam, Netherlands); Bröder, Lisa; Keskitalo, Kirsi; Kloostra, Oscar; Tesi, Tommaso; Zimov, Nikita; Davydova, Anya; Haghipour, Negar; Eglinton, Timothy and Vonk, Jorien. Permafrost organic carbon transport and degradation on a transect from the Kolyma River to the East Siberian shelf [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7206, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic rivers will be increasingly affected by the hydrological and biogeochemical effects of thawing permafrost. During transport, permafrost thaw-derived organic carbon (OC) can be degraded into greenhouse gases and potentially add to further climate warming, or transported to the shelf seas and buried in marine sediments, attenuating this "permafrost carbon feedback". To assess the transport pathways and fate of permafrost-OC, we focus on the river-shelf continuum of the Kolyma River, the largest river on Earth completely underlain by continuous permafrost. Three pools of riverine OC were investigated: dissolved OC (DOC), suspended particulate OC (POC), and river sediment OC (SOC). Preliminary results of bulk carbon isotopes (d13C, 14C) and molecular biomarkers (lignin phenols, leaf wax lipids) show contrasts in composition and degradation state for these carbon pools. Old permafrost-OC seems to be mostly associated with SOC, and less dominant in POC. However, while SOC shows the oldest 14C signal, lignin phenol results (e.g., acid to aldehyde ratios) suggest this material is the least degraded. In contrast, DOC shows more degraded signal, even at the outflow of an active permafrost thaw site. Our study serves as a terrestrial extension to earlier investigated marine sediments from the Kolyma paleoriver transect in the East Siberian Sea. It also highlights the value of connecting terrestrial and marine observations to gain insight into the complete pathway of permafrost-OC, from the moment of thaw, via aquatic transport and degradation, towards storage in marine sediments. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7206

2020059479 Juhls, Bennet (Freie Universität Berlin, Institute of Space Sciences, Berlin, Germany); Overduin, Pier Paul; Stedmon, Colin Andrew; Morgenstern, Anne; Meyer, Hanno; Heim, Birgit; Hölemann, Jens and Povazhnyi, Vasily. Seasonality in Lena River biogeochemistry and dissolved organic matter [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5253, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The carbon export by rivers to the Arctic Ocean is expected to increase in response to the rapidly changing climate in the Arctic (Camill, 2005; Freeman et al., 2001; Frey and Smith, 2005). This is in part due to thawing permafrost and mobilization of particulate and dissolved organic matter (DOM). The Lena River delivers approximately one fifth of the total river discharge to the Arctic Ocean and is the main source of DOM in the Laptev Sea shelf (Thibodeau et al., 2014). To date river fluxes of DOM have been based on sparse coverage of sample across the hydrograph about 700 km upstream (Cooper et al. 2005; Raymond et al. 2007; Stedmon et al. 2011; Amon et al. 2012). The effects of low frequency sampling on load estimates are unknown and potentially large for systems such as these where there are considerable changes across the hydrograph. Here we present results from a unique high frequency sampling program and evaluate its viability to monitor export fluxes of DOM and its biogeochemistry in the Lena River. The sampling takes place close to the river mouth at the research station Samoylov in the central Lena River Delta. The Samoylov research station allows a unique chance for continuous sampling since it operates throughout the year. The sampling program includes measurements of several water parameters, such as temperature, electric conductivity, dissolved organic carbon (DOC), spectral CDOM absorption (aCDOM), fluorescent dissolved organic matter (FDOM) and water stable isotopes. The data facilitated the identification of the main drivers behind the seasonality of DOM concentration and biogeochemistry of the Lena River. Three main water sources could be identified (1) (snow) melt water, (2) rain water and (3) subsurface water. Melt and rain water are found to be the prevailing water sources that combined transport 5.8 Tg C dissolved organic matter (~ 85% of annual flux (6.8 Tg C)) into the Lena River. The high number of samples throughout the whole year allowed flux calculations that are independently from load models that likely lead to a large variation of earlier studies. The absorption properties of DOM revealed changing composition and sources of DOM throughout the year. Decreasing SUVA values during the summer point towards an increasing fraction of old DOM which potentially originates from degrading permafrost. In contrast, during the spring freshet, high SUVA indicate mostly fresh organic matter with high molecular weight and high aromaticity. This dataset represents the first year of a planned long-term monitoring program at the Research Station Samoylov Island and provides a baseline data set against which future change of this large integrative system may be measured. A continuous sampling of Arctic River water will facilitate to identify intra and inter-annual trends with ongoing climate change. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5253

2020059520 Keskitalo, Kirsi (Vrije Universiteit Amsterdam, Amsterdam, Netherlands); Bröder, Lisa; Jong, Dirk; Zimov, Nikita; Davydova, Anya; Davydov, Sergey; Tesi, Tommaso; Mann, Paul; Haghipour, Negar; Eglinton, Timothy and Vonk, Jorien. Degradation of permafrost carbon in the Kolyma River [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8311, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Soil temperatures in permafrost (i.e. perennially frozen ground) are rising globally. The increasing temperatures accelerate permafrost thaw and release of organic carbon, that has been locked in permafrost soils since the last glacial period, to the contemporary carbon cycle. The potential remineralisation of organic carbon to greenhouse gases can contribute to further climate warming. Particulate organic carbon (POC) in the Kolyma River is older than dissolved organic carbon (DOC) thus serves as a good tracer for abrupt permafrost thaw (i.e. river bank erosion and thermokarst) that dominantly releases old POC. While dissolved organic carbon (DOC) mobilised from the old Yedoma outcrops on the banks of the Kolyma River is shown to be highly labile, vulnerability of POC to biodegradation is not yet known. In this study we aim to constrain degradation rates for POC in the Kolyma River. To capture seasonal variability of the POC pool and its degradation rate the incubation was conducted both during the spring freshet and in late summer (2019 and 2018, respectively). We incubated whole-water samples over 9 to 15 days and quantified POC (and DOC) loss over time, as well as dissolved inorganic carbon (DIC). The incubation was carried out in the dark. We also tracked changes in POC composition and age with carbon isotopes (d13C-OC, d13C-DIC, D14C). Preliminary results from 2018 suggest a decrease in POC concentrations of up to 30% while those of DOC decrease by up to 11%. The rate of POC degradation is nearly three times faster than DOC though the absolute amounts of DOC are in turn higher than those of POC (< 1 mg L-1 for POC and ~3 mg L-1 for DOC). Furthermore, the changes in d13C of POC, DOC and DIC suggest ongoing microbial degradation and conversion of organic carbon into inorganic carbon. These first estimates show that POC degrades fairly rapidly while transported in the Kolyma River. A better understanding of POC degradation along lateral flow paths is critical for improving our knowledge of permafrost thaw and its possible climate impacts in the future. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8311

2020059493 Kim, Jin-Soo (University of Edinburgh, School of GeoSciences, Edinburgh, United Kingdom); Kug, Jong-Seong; Jeong, Su-Jong; Park, Hotaek and Schaepman-Strub, Gabriela. Extensive fires in southeastern Siberian permafrost linked to preceding Arctic Oscillation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6502, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Terrestrial Arctic is a critical region for positive carbon-climate feedback because of the release of considerable organic carbon from the permafrost buried in the soil. Fires rapidly transfer carbon to the atmosphere. Thus, carbon release through boreal fires could considerably accelerate Arctic warming; however, boreal fire occurrence mechanisms and dynamics remain largely unknown. Here, we analyze fire activity and relevant large-scale atmospheric conditions over southeastern Siberia, which has the largest burned area fraction in the circumboreal and high-level carbon emissions due to high-density peatlands. It is found that the annual burned area increased when a positive Arctic Oscillation (AO) takes place in early months of the year, despite peak fire season occurring 1 to 2 months later. A local high-pressure system linked to the AO drives a high-temperature anomaly in late winter, causing premature snowmelt. This causes earlier ground surface exposure and drier ground in spring due to enhanced evaporation, promoting fire spreading. Recently, southeastern Siberia has experienced warming and snow retreat; therefore, southeastern Siberia requires appropriate fire management strategies to prevent massive carbon release and accelerated global warming. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6502

2020059487 Knoflach, Bettina (University of Innsbruck, Department of Geography, Innsbruck, Austria); Tussetschläger, Hannah; Sailer, Rudolf; Meissl, Gertraud and Stötter, Johann. A rockfall inventory; Otztal Alps, Tyrol, Austria [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5945, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Climate change has serious implications for the cryosphere and a close relationship between the instability of rock faces and the changes in high mountain permafrost is suspected. Although, the number of rockfall events in Alpine areas is increasing, detailed analyses of the frequency and runout distances in high altitudes are rare. This study gives an insight into the rockfall activity in the Otztal Alps in Tyrol, Austria. A systematic observation utilizing bi-temporal ALS-DTMs in combination with orthoimages revealed a total of 93 rockfalls over an area of 637 km2 in the period from 2006 to 2010. Since more than 90% of the rockfall release areas were mapped in potential permafrost areas, a correlation between rockfall activity and climatically driven degradation of permafrost in bedrock is very likely. 18 rockfall events, ranging in volume from 69 to 8420 m3, were suitable for runout assessments. To estimate the maximum range of future rockfalls with empirical models, values of 30 ° (Fahrböschung) and 26 ° (minimum shadow angle) can be proposed for risk assessment at a regional scale (1:25,000 - 1:100,000). Rockfalls occurring on snow or ice may also go below these values. Keywords: Rockfall, Permafrost, digital elevation model; runout distance, Fahrböschung, minimum shadow angle, Otztal Alps [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5945

2020059516 Krebs, Nora (GFZ German Research Centre for Geosciences, Potsdam, Germany); Voigtländer, Anne; Bücker, Matthias; Hördt, Andreas; Schroeckh, Ruben and Buckel, Johannes. Pushing the limits of electrical resistivity tomography measurements on a rock glacier at 5500 m a.s.l. on the Tibetan Plateau; successes and challenges [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8159, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Geophysical methods provide a powerful tool to understand the internal structure of active rock glaciers. We applied Electrical Resistivity Tomography (ERT) to a rock glacier at an elevation of 5500 m a.s.l. in the semi-arid Nyainqentanglha mountain range on the Tibetan plateau, China. The investigations comprised three transects across the rock glacier and its catchment, each spanning over a distance of 296 m up to 396 m, equipped with 75 up to 100 electrodes respectively. Our measurements were successful in revealing internal structures of the rock glacier, but were also accompanied by challenges. We successfully detected first-order permafrost structures, such as a shallow about 4 m thick active layer of low electrical resistivity values that was underlain by potentially ice rich zones of high resistivity. Further high-resistivity zones were found and interpreted as dense bed rock of adjacent slopes that undergird the loose rock glacier debris. Challenges, we faced in the application of ERT, were mainly posed by the morphology and internal structure of the rock glacier itself. Coarse debris created a rough surface that prevented a uniform setup with accurate 4 m spacing. The presence of loosely nested blocks of pebble size up to boulders with large interspaces resulted in high contact resistances. The consequent low injection current densities and possible noisy voltage readings downgraded part of the data, causing low data density and resolution. Coupling was partly improved by attaching salt-watered sponges to the electrodes and adding more conductive fine-grained materials to the electrodes. The detected high resistivity ice layer impeded deep penetration of electrical currents, which caused that the lower limit of the permanently frozen zone could not be defined. Despite these challenges, the captured ERT profiles are an indispensable contribution to the sparse field data on the internal structure of rock glaciers on the Tibetan plateau. Our results contribute to a better understanding of the prospective evolution of rock glaciers in dry, high mountain ranges under a changing climate. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8159

2020059426 Krivenok, Liudmila (Russian Academy of Sciences, A.M. Obukhov Institute of Atmospheric Physics, Moscow, Russian Federation); Kazantsev, Vladimir and Dvornikov, Yury. Experimental study of methane emission from lake seeps of western Siberia permafrost zone [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-563, 3 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Methane is one of the most potent greenhouse gases affecting climate change. According to different estimates, natural sources contribute 35-50% to global CH4 emission. Among them, the third-biggest source is lakes emitting to the atmosphere 10-50 TgCH4 per year [Anderson et al., 2010]. We have discovered two gas seeps during the summer 2019 field campaign within the lake near the Vas'kiny Dachi research station (Central Yamal, Western Siberia). Measurement of the ebullition intensity in tenfold replicate and gas sampling were carried out using a bubble trap of the original design. The concentration of methane in seep gas was determined by a Crystal 5000.2 gas chromatograph with a flame ionization detector; each sample was diluted tenfold with air. We calculated the annual CH4 flux from seep to the atmosphere with the consideration of the intensity of seep ebullition and the methane concentration in gas equal during the year. To determine the potential source of the gas, we analyzed the isotopic composition of CH4 (d13C and dD) by a Delta-V mass spectrometer. The values (median ± SD) of the gas ebullition are 175 ± 26 mL/min and 127 ± 10 mL/min for the first and second seeps respectively. The methane concentration in gas is 95-100%. The intensity of CH4 emission from the first seep is 89.7 thousand L or 64 kg per year; from the second seep is 65.1 thousand L or 46.5 kg per year. Analysis of the content of d13C and dD isotopes in methane gives the following results. For the first seep: d13C vs VPDB, ppm = -75.73, dD vs VSMOW, ppm = -226.68. For the second seep: d13C vs VPDB, ppm = -76.97, dD vs VSMOW, ppm = -222.31. According to the classification from [Whiticar, 1999], seep methane is of biogenic origin. Potentially, gas could migrate to the lake surface through sub-lake talik from the underlying geological horizon containing methane hydrates in self-preserved form as widely documented for this area [Chuvilin et al., 2000]. To summarize, lake seeps of the Western Siberia tundra zone have been studied as a source of the atmospheric methane for the first time. Considering the occurrence of methane hydrates withing permafrost in the study area, we describe a path of the CH4 release from decomposing gas hydrates into the atmosphere in the northern part of Western Siberia. The study was partially supported by the RAS Program no. 20 and the state contract of the IAP RAS no. 075-03-2019-628. References: Anderson B., Bartlett K., Frolking S. et al. Methane and nitrous oxide emissions from natural sources. Washington: EPA. 2010. 194 p. Chuvilin E.M., Yakushev V.S., Perlova E.V. Gas and possible gas hydrates in the permafrost of Bovanenkovo gas field, Yamal Peninsula, West Siberia // Polarforschung. 2000. V. 68. P. 215-219. Whiticar M. Carbon and hydrogen isotope systematics of bacterial formation and oxidation of methane. Chemical Geology. 1999. V. 161. P. 291-314. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-563

2020059480 Kulawska, Aleksandra (University of Birmingham, School of Geography, Earth & Environmental Sciences, Birmingham, United Kingdom); Pugh, Thomas A. M.; Kettridge, Nicholas; MacKenzie, Rob and Ullah, Sami. What governs the effects of permafrost thaw on boreal forest dynamics? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5404, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Boreal forests are located at latitudes that are predicted to experience some of the greatest warming on the planet. Forests growing on permafrost may be particularly vulnerable, with accelerated soil warming and permafrost degradation linked to changing patterns of tree growth and longevity. Many have speculated that thawing permafrost, through its effects on soil water content and ground stability, will increase forest mortality across the boreal region. However, recent evidence indicates mixed forest responses to permafrost thaw. In some areas, the onset of thaw is followed by increased tree growth and increased forest cover area. In other sites, thaw has been linked to decreased growth and forest cover loss. It is currently poorly understood what determines these contrasting responses, and the roles that different environmental and climatic factors may play. This leads to two major issues: (1) uncertainties in predicting the effects of future permafrost thaw on carbon dynamics in northern ecosystems, and (2) poor understanding of where scientific and conservation efforts should be focused. Here, we present a review of the recent evidence of permafrost thaw effects on boreal forest dynamics and propose an explanation for the differing responses across sites. We argue that the outcome is controlled by a set of factors that influence two major pathways and the interactions between them: (1) permafrost-soil water content and (2) soil water content-plant growth. We present a series of conceptual models explaining these interactions and highlight the largest sources of uncertainties. Based on these, we propose a set of hypotheses and methodologies to guide future research in this area. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5404

2020059474 Lakomiec, Patryk (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Holst, Jutta and Rinne, Janne. Methane emissions from a palsa-mire underlaid by sporadic permafrost under rapid degradation [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4748, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Methane is one of the most important greenhouse gases. The largest natural source of this gas are wetlands. Quantification emission from this source, especially from subarctic regions, which are exposed to fast climate changes, is important for our understanding of biogeochemical climate feedbacks. Abisko Stordalen is one of few mires in this climatic zone in which the methane emission is being measured continuously. Here we analyze eddy covariance data from the ICOS Sweden site with respect to environmental parameters possibly controlling the methane emissions. Due to the large scale topography at Abisko, wind is channeled along the valley, resulting in to two main wind directions. This divides the measurements into two different surface type groups. On easterly winds, the flux footprint is dominated by permafrost features, while for westerly winds it is dominated by non-permafrost fen. Measured methane fluxes from these to wetland types, exposed for the same environmental conditions, differ considerably being higher from non-permafrost area. We will further analyze the differences in the annual methane emission from the two systems, and their dependencies from environmental parameters. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4748

2020059512 Lee, Dong-Hun (Hanyang University, ERICA Campus, Ansan, South Korea); Kim, Ji-Hoon; Lee, Yung Mi; Jin, Young Keun and Shin, Kyung-Hoon. Biogeochemical signature of elevated methane in water column of the outer East Siberian Arctic shelf [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7898, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The East Siberian Arctic Shelf (ESAS) had high methane concentrations in the seawater of the inner shelf over the decades, which was regarded as significant methane source for global warming. The source information of elevated dissolved methane at the inner ESAS has so far been reported, however, the characterizations (i.e., formation and transport) of enriched ones in the outer ESAS remain to date still unclear. To unravel this, we have reported methane properties along south-north transects of the outer ESAS (73.7°-77.1°N and 164.3°-178.0°E, water depths; 41-370 m) performed from 2016, 2018 and 2019 ARAON Expeditions. The dissolved methane concentrations in surface seawater were mostly higher than those of the atmospheric equilibrium concentration and its maximum value in the water column of the outer ESAS hotspots had ca. 204 nM. Based on principal component analysis including CTD profiles (i.e., temperature, salinity, dissolved oxygen and fluorescence) and methane concentrations, elevated methane concentrations (88 to 204 nM) were close to fluorescence concentrations (0.1 to 0.4 mg/m3). Furthermore, the isotopic signatures of dissolved methane (d13C; -66.6 to -26.6 ppm and dD; -218.8 to -34.0 ppm) and dissolved inorganic carbon (d13C; -10.1 to -4.4 ppm) showed large isotopic variations, indicating the methane production in the study area is likely to be complicated using carbon dioxide and methyl substrates. In this regard, organic matter preserved in the submerged permafrost and/or methyl compound produced by phytoplankton might be also potential substrates for elevated methane at some locations. In the near future, mass balance model via end-member approach will be applied for determining the discriminative contributions of possible methane sources in the outer ESAS. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7898

2020059489 Li, Haiyan (University of Helsinki, Institute for Atmospheric and Earth System Research, Helsinki, Finland); Maki, Mari; Kohl, Lukas; Valiranta, Minna; Back, Jaana and Bianchi, Federico. Overlooked volatile production from Arctic permafrost triggered by global warming [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5988, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost thaw, as a consequence of climate warming, liberates large quantities of frozen organic carbon in the Arctic regions. The response of gaseous carbon release upon permafrost thaw might play a crucial role in the future evolution of atmosphere-land fluxes of biogenic gases such as volatile organic compounds (VOCs), a group of reactive gases and the dominant modulator of tropospheric oxidation capacities. Here, we examine the response of volatile release from Finnish Lapland permafrost soils to temperature increase in a series of laboratory incubation experiments. The experiments show that when the temperature rises from 0 °C to 15 °C, various VOC species are significantly emitted from the gradually thawing soils. The VOC fluxes from thawing permafrost are on average four times as high as those from active layer. Acetic acid and acetone dominate the total volatile emissions from both permafrost and active layer, with significant amounts of aromatics and terpenes detected as well. The emission rate and the composition of volatile release from thawing soils are highly responsive to temperature variations. As temperature increases, more less volatile compounds are released, i.e., sesquiterpenes and diterpenes. Collectively, these results demonstrate the highly overlooked volatile production from thawing permafrost, which will create a stronger permafrost carbon-climate feedback. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5988

2020059494 Li Rongxing (Tongji University, Shanghai, China); Hao Tong; Lu Ping; Qiao Gang; Chen Lemin; Han Jiangping and Li Zhenshi Zhenshi. Estimation of active layer thickness from modeling and InSAR deformation data at QTP [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6560, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In context of global warming, permafrost, as an important component of cryosphere in the Qinghai-Tibetan Plateau (QTP) that is located in middle and low latitudes with a high radiation intensity of high Asia mountains, is particularly sensitive to climate changes. The active layer thickness (ALT) in a permafrost area is an important index to indicate its stability. Traditional methods for measuring ALT in QTP mainly rely on ground-based field surveys and accordingly are extremely time- consuming and labor-intensive. The field works provide a good quality of data at a single site, however, such measurements are limited in spatial coverage and difficult for multi-temporal acquisitions. In addition, the harsh environment in QTP is not suitable for large-scale field measurements. In this study, the ALT of permafrost in QTP is estimated using modelling and remote sensing data. Particularly, the surface deformation on permafrost, as detected by the long-term InSAR technique, is considered as an input to the inversion model of ALT. The time-series deformation results over an experimental permafrost area were obtained by the SBAS-InSAR technique. Then, combined with the soil characteristics of soil moisture and soil thermal conductivity in the Stefan model, the melting thickness was estimated. Finally, the resulting ALT was tested and verified against a set of in-situ borehole measurements of depth-temperature. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6560

2020059506 Loew, Simon (ETH Zurich, Department of Earth Sciences, Zurich, Switzerland); Buehler, Nora and Aaron, Jordan. Does climate change influence the frequency of large rock slope failures? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7361, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

A large number of scientific contributions (e.g. BAFU 2017, Speicher 2017, Phillips et al. 2017, Ravanel et al. 2017, Haque et al. 2016) have suggested that many recent rock slope failures in the European Alps have been triggered by climate warming. For example, Huggel et al. 2012 and Fischer et al. 2012 could show that rock fall frequencies above 2000 masl increased significantly since 1990 at regional (Swiss Alps and adjacent areas) and local (Mont Blanc) scale, based on 52 events larger than 1000 m3 (PERMOS data base) covering the period 1900-2010. This increase in frequency could be correlated with a significant departure of mean annual temperature from the 1960-1990 average, based on a dataset describing conditions in Switzerland. Paranunzio et al. 2016 systematically studied the climatic conditions and anomalies occurring before 41 rock fall events in the Italian Alps with volumes of several hundred to several million m3. They show that positive and negative temperature anomalies triggered the majority of analysed rock fall events in a complex manner, but that melting of permafrost was clearly not the only rock fall trigger. However, there have been no studies which systematically investigate changes in the frequency of rock fall events based on complete inventories covering a large range of rock fall volumes. To fill this gap, we have generated a new database for rapid rock slope failures in the Swiss Alps covering events larger than 100'000 m3 (Bühler 2019, BSc Thesis ETH 2019). This catalogue covers the period between 1700 and 2019 and includes 86 events with reliably estimated volume, date and location of occurrence, and pre-disposing factors (such as slope orientation, permafrost occurrence and geological setting). Volume-cumulative frequency plots of the events demonstrate completeness of the catalogue for all size classes, and significant changes in the ratios between large and small events through time. An enhanced frequency of the volume class of 105 m3 (100'000-999'000 m3) is observed starting from 1940, predominantly occurring in permafrost areas and elevations ranging between 2800 and 3200 masl. This increasing frequency signal with time disappears for increasing volumes beyond a magnitude of about 400'000 m3 and is clearly absent for very large rock slope failure of millions to tens of millions of m3. The volume dependence of climate sensitivity can be physically explained, as larger volume slope failures tend to have deeper failure surfaces. Typical failure depth for multi-million m3 slope failures in crystalline rocks are up to a few 100 meters, and beyond the depth of Alpine permafrost. Direct impacts of surface temperature changes on permafrost are mainly manifested through a minor thickening of the active layer, typically ranging between 1 and 10 meters, but indirect effects at the depth range of decameters (i.e. the depth of failure surfaces for events of the 105 m3 class) have been assessed and demonstrated in a large number of studies. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7361

2020059511 Magnusson, Runa (Wageningen University, Environmental Sciences Group, Wageningen, Netherlands); Heijmans, Monique M. P. D.; Limpens, Juul; van Huissteden, Ko; Kleijn, David and Maximov, Trofim C. Arctic greening, Arctic browning or Arctic drowning? [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7727, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Thawing of permafrost and the resulting decomposition of previously frozen organic matter constitute a positive feedback to global climate. However, contrasting mechanisms are at play. Gradual increases in thawing depth and temperature are associated with enhanced vegetation growth, most notably in shrubs ("greening"). In ice-rich permafrost, abrupt thaw (thermokarst) results in disturbance of vegetation and surface wetting, which may result in an opposing trend ("browning"). We determined the balance of shrub decline and expansion in an ice-rich lowland tundra ecosystem in north-Eastern Siberia using vegetation classification and change analysis. We used random forest classification on 3 very high resolution commercial satellite images gathered between 2010 and 2019 (GeoEye-I and WorldView-II). To mitigate (slight) differences in sensor properties and vegetation phenology, a spatio-temporal implementation of Potts model was used to utilize both spectral properties of a pixel and its degree of correspondence with spatially and temporally neighbouring pixels. This reduced artefacts in change detection substantially and improved accuracy of classification for all three images. We found that shrub vegetation declines in this lowland tundra ecosystem. Areas of thaw features (thermokarst ponds, thermoerosion gullies) and aquatic plant types (sedges and peat mosses) however show an increasing trend. Markov Chain analysis reveals that thaw features display a succession from open water / mud to sedges to peat moss. This transition from shrub dominated to wetland species dominated tundra may have important implications for this ecosystem's greenhouse gas balance and is indicative of wetter conditions. Thermokarst may be an important driver of such change, as thaw features are found to expand at the expense of shrub vegetation and show rapid colonization by aquatic species. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7727

2020059515 Majdanski, Mariusz (Polish Academy of Sciences, Institute of Geophysics, Warsaw, Poland); Marciniak, Artur; Owoc, Bartosz; Dobinski, Wojciech; Wawrzyniak, Tomasz; Osuch, Marzena; Nawrot, Adam and Glazer, Michal. Geophysical imaging of permafrost in the SW Svalbard; the result of two High Arctic expeditions to Spitsbergen [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8136, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic regions are the place of the fastest observed climate change. One of the indicators of such evolution are changes occurring in the glaciers and the subsurface in the permafrost. The active layer of the permafrost as the shallowest one is well measured by multiple geophysical techniques and in-situ measurements. Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). Two seismic profiles have been designed to visualize the shape of permafrost between the sea coast and the slope of the mountain, and at the front of a retreating glacier. For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with GPR and ERT measurements, and continuous temperature monitoring in shallow boreholes. Joint interpretation of seismic and auxiliary data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the active layer where P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. The same laboratory study shows significant (>10%) increase of velocity in frozen low porosity rocks, that should be easily visible in seismic. In the reflection seismic processing, the most critical part was a detailed front mute to eliminate refracted arrivals spoiling wide-angle near-surface reflections. Those long offset refractions were however used to estimate near-surface velocities further used in reflection processing. In the reflection seismic image, a horizontal reflection was traced at the depth of 120 m at the sea coast deepening to the depth of 300 m near the mountain. Additionally, an optimal set of seismic parameters has been established, clearly showing a significantly higher signal to noise ratio in case of frozen ground conditions even with the snow cover. Moreover, logistics in the frozen conditions are much easier and a lack of surface waves recorded in the snow buried geophones makes the seismic processing simpler. Acknowledgements: This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8136

2020059435 Makarieva, Olga (Melnikov Permafrost Institute, Yakutsk, Russian Federation); Nesterova, Nataliia; Fedorov, Alexander and Shikhov, Andrey. The impact of thermokarst lakes on streamflow generation in central Yakutia (Russia); data assessment and modelling [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1095, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Central Yakutian Plain (Russia) is situated in Eastern Siberia in the Lena River basin and is characterized by severe continental climate, continuous permafrost and flat relief. The combination of semi-arid climate, gentle topography and ice-rich permafrost provides favorable conditions for the development of thermokarst lakes. Poorly developed river drainage system and the distribution of thermokarst lakes within the river basins form the areas with internal drainage which contribute runoff to river network only in wet conditions. The results of such environment are the special hydrological regime of the region which is characterized by extreme seasonal and annual variability of streamflow. In this project we study the hydrological processes in four rivers of Central Yakutia with the basin area from 1270 to 8290 km2 and available long-term streamflow data. Thermokarst lakes take up to 5-10% of the area of those basins. Annual precipitation of this area is about 240 mm, while average annual streamflow varies from 1 to 15 mm depending on the river basin. Due to climate warming the number and area of thermokarst lakes in Central Yakutia is increasing (Kravsova, Tarasenko, 2011). The aim of the project is to investigate the impact of thermokarst lakes on hydrological regime and provide some reasonable projections of its changes in the future. Previous study (Lebedeva, 2018) has shown that the results of streamflow simulations in this region based on standard hydrological modeling approach were not satisfactory. We used remote sensing data (Landsat images) to assess the seasonal and annual variation of thermokarst lakes area and their contributing area and combined that data with hydrological modelling of runoff formation processes. The hydrological model Hydrograph (Vinogradov et al., 2011) was applied in this study. The model contains the algorithms of heat and moisture dynamics in the upper part of soil profile which allow its use in the permafrost conditions. New part of the model algorithm was developed which considers the variations of thermokarst area depending on meteorological conditions, evaporation from open water areas and the dynamic of surface runoff retention depth. These model improvements allowed for the satisfactory results in streamflow simulations for historical period and future projections. In general, with the future development of thermokarst lakes in Central Yakutia one may expect the decrease of annual streamflow and its higher variation from one year to another. The results of the study will be presented. The study was funded by RFBR, project number 19-35-50030. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1095

2020059436 Manasypov, Rinat (Tomsk State University, BIO-GEO-CLIM Laboratory, Tomsk, Russian Federation); Pokrovsky, Oleg and Shirokova, Liudmila. Biogeochemistry of macrophytes, sediments and porewaters in thermokarst lakes of western Siberia in the discontinuous and continuous permafrost zone [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1128, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Despite high importance of macrophytes in shallow thaw lakes for control of major and trace nutrients in lake water, the chemical composition of different aquatic plants and trace element (TE) partitioning between macrophytes and lake water and sediments in the permafrost regions remain totally unknown. Here we sampled dominant macrophytes of thermokarst (thaw) lakes of discontinuous and continuous permafrost zones in Western Siberia Lowland (WSL) and we measured major and trace elements in plant biomass, lake water, lake sediments and sediment porewater. All 6 studies plants (Hippuris vulgaris L., Glyceria maxima (Hartm.) Holmb., Comarum palustre L., Ranunculus spitzbergensis Hadac, Carex aquatilis Wahlenb s. str., Menyanthes trifoliata L.), sizably accumulate macronutrients (Na, Mg, Ca), micronutrients (B, Mo, Nu, Cu, Zn, Co) and toxicants (As, Cd) relative to lake sediments. The accumulation of other trace elements including rare earth elements (REE) in macrophytes relative to pore waters and sediments was strongly species-specific. Under climate warmings scenario and the propagation of southern species northward, the accumulation of trace metals in aquatic plants of thermokarst lakes will produce preferential uptake of Cd, Pb, Ba from thermokarst lake water and sediments by the biomass of aquatic macrophytes. This may eventually diminish the transport of metal micronutrients from lakes to rivers and further to the Arctic Ocean. Support from the RSF (RNF) grant 19-77-00073 "Experimental modeling of the formation mechanisms for elemental composition of water in thermokarst lakes of Western Siberia: vegetation effect". [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1128

2020059471 Maximov, Trofim C. (Russian Academy of Sciences, Siberian Branch, Institute for Biological Problems of Cryolithozone, Yakutsk, Russian Federation); Dolman, Han; Kotani, Ayumi; Anderson, Per; Maksimov, Ayaal and Petrov, Roman. Carbon cycle of permafrost transect; main terrestrial and hydrological ecosystems of eastern Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4322, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Almost 65% of Siberian forests and 23% of tundra vegetation grow in permafrost zone. According to our estimate, carbon stocks in the soils of forest and tundra ecosystems of Yakutia (Eastern Siberia, Russia) amount to 17 billion tons (125.5 million hectares of forest and 37 million hectares of tundra in total) that is about 25% of total carbon resource in the forest soils of the Russian Federation. This presentation is compiled from the results of many years time series investigations conducted on the study of carbon cycle in permafrost-dominated forests with different productivity and typical tundra and along Great Lena river basin including Aldan and Viluy tributaries. Seasonal photosynthesis maximum of forest canopy vegetation in dry years falls into June, and in humid ones - into July. During the growing season the woody plants of Yakutia uptake from 1.5 to 4.0 t C ha-1 season-1 depending on water provision. Night respiration is higher in dry and extremely dry years (10.9 and 16.1% respectively). The productive process of tree species in Eastern Siberia is limited by endogenous (stomatal conductance) and exogenous (provision with moisture and nutrients, nitrogen specifically) factors. The increase of an atmospheric precipitation after long 2-3 annual droughts accompanied with strong surge in photosynthetic activity of forest plants is almost 2.5 times. The temperature of soil is a key factor influencing soil respiration in the larch forests. Average soil respiration for the growing season comes to 6.9 kg C ha-1 day-1, which is a characteristic of Siberian forests. Annual average soil emission is 4.5±0.6 t C ha-1 yr-1. As our multi-year studies showed, there is significant interannual NEE variation in the Central Yakutia larch forest, while in the Southern Yakutia larch forest and tundra ecosystem variation is more smooth, because the climatic conditions in these zones (close to the mountain and sea) are less changeable than in sharply continental Central Yakutia. According to our long-term eddy-correlation data, the annual uptake of carbon flux (NEE) in the high productivity larch forest of South eastern Yakutia, 60N - 2.43±0.23 t C ha-1 yr-1, in the moderate productivity larch forest of the Central Yakutia, 62N makes 2.12±0.34 t C ha-1 yr-1 and in the tundra zone, 70N - 0.75±0.14 t C ha-1 yr-1. Interannual variation of carbon fluxes in permafrost forests in Northeastern Russia (Yakutia) makes 1.7-2.4 t C ha-1 yr-1 that results in the upper limit of annual sequestering capacity of 450-617 Mt C yr-1. In connection with climate warming there is a tendency of an increase in the volume of carbon sequestration by tundra and as opposed to decrease by forest ecosystem in the result of prolongation of the growing season and changing of plant successions. This is also supported by changes in land use as well as by CO2 sequestration in the form of fertilizer. According our biogeochemical investigation annual flux of carbon from main in Eastern Siberia Lena river hydrological basin is almost 6.2 Mt C yr-1 including 28% at Aldan and 14% at Viluy rivers. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4322

2020059437 Mazoyer, Flora (Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Quebec City, QC, Canada); Laurion, Isabelle and Rautio, Milla. The role of photodegradation on the mineralization of permafrost DOM [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1144, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost thaw leads to the formation of shallow water bodies in which large quantities of terrestrial organic carbon are mobilized as dissolved organic matter (DOM), partly turned into greenhouse gases (GHG). DOM comes from ancient carbon pools trapped in frozen soils for hundreds to thousands of years but also from present-day primary producers. Determining the fate of these pools is fundamental to evaluate the potential of these water bodies to amplify climate warming through their GHG emissions. In addition to the microbial degradation pathways producing CO2 and CH4, DOM can be directly mineralized into CO2 by sunlight. The CO2 production rates from photodegradation vary extensively across Arctic regions. The controlling factors and interactions with the microbial communities are not well understood, while photodegradation is likely to rise as the open-water season extends. Determining the photo- and bio-lability of the carbon pools available on thawing permafrost landscapes is needed to predict to what extent these systems can affect the global carbon cycle. Various DOM and environmental characteristics are considered in my PhD project, including mixing regime, seasonal exposure and light attenuation, as well as the microbial community response to photo-induced chemistry changes in DOM. Study sites include subarctic and arctic peatland areas of Eastern Canada, rich in thaw ponds and where organic matter started to accumulate between 3700 and 5600 years BP. These are non-Yedoma systems that have been poorly studied despite the large amount of organic carbon they store. This presentation will show the results of a lab experiment using a solar simulator where DOM of various origins and ages were tested: thaw pond water and leachates from plants, permafrost active layer, and previously unthawed permafrost. Short term incubations were carried out under five treatments: exposure to light without bacteria (0.2 mm filtration), exposure to light followed by a dark incubation with a bacterial inoculum, dark incubation with a bacterial inoculum, dark incubation with the whole bacterial community (2.7 mm filtration), and dark control without bacteria. A set of optical, biological and chemical characteristics were measured at the beginning and end of incubation. DOM losses (DOC, CDOM, and FDOM) and CO2 production vary extensively among treatments and DOM pools. They were the highest in dark bacterial incubations of plants leachates. DOM of the subarctic area was quite refractory to degradation in general, except for the biodegradation of the unthawed permafrost leachate (- 50%). Photodegradation was observed in all water types, with DOM losses faster than biodegradation ones for the Arctic soils leachates and all the ponds waters. The highest CO2 photoproduction was measured in Arctic unthawed permafrost leachates. Finally, the enhancement of DOM lability to microbes caused by photodegradation was generally observed for unthawed permafrost leachates. Incoming biological and 14C data, along with multivariate analyses, will improve the characterisation of the trends. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1144

2020059507 Mollaret, Coline (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Wagner, Florian M.; Hilbich, Christin and Hauck, Christian. Quantification of ground ice through petrophysical joint inversion of seismic and electrical data applied to alpine permafrost [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-7489, 2 ref., 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Quantification of ground ice is particularly crucial for understanding permafrost systems. The volumetric ice content is however rarely estimated in permafrost studies, as it is particularly difficult to retrieve. Geophysical methods have become more and more popular for permafrost investigations due to their capacity to distinguish between frozen and unfrozen regions and their complementarity to standard ground temperature data. Geophysical methods offer both a second (or third) spatial dimension and the possibility to gain insights on processes happening near the melting point (ground ice gain or loss at the melting point). Geophysical methods, however, may suffer from potential inversion imperfections and ambiguities (no unique solution). To reduce uncertainties and improve the interpretability, geophysical methods are standardly combined with ground truth data or other independent geophysical methods. We developed an approach of joint inversion to fully exploit the sensitivity of seismic and electrical methods to the phase change of water. We choose apparent resistivities and seismic travel times as input data of a petrophysical joint inversion to directly estimate the volumetric fractions of the pores (liquid water, ice and air) and the rock matrix. This approach was successfully validated with synthetic datasets (Wagner et al., 2019). This joint inversion scheme warrants physically-plausible solutions and provides a porosity estimation in addition to the ground ice estimation of interest. Different petrophysical models are applied to several alpine sites (ice-poor to ice-rich) and their advantages and limitations are discussed. The good correlation of the results with the available ground truth data (thaw depth and ice content data) demonstrates the high potential of the joint inversion approach for the typical landforms of alpine permafrost (Mollaret et al., 2020). The ice content is found to be 5 to 15% at bedrock sites, 20 to 40% at talus slopes, and up to 95% at rock glaciers (in good agreement to the ground truth data from boreholes). Moreover, lateral variations of bedrock depth are correctly identified according to outcrops and borehole data (as the porosity is also an output of the petrophysical joint inversion). A time-lapse version of this petrophysical joint inversion may further reduce the uncertainties and will be beneficial for monitoring and modelling studies upon climate-induced degradation. References: Mollaret, C., Wagner, F. M., Hilbich, C., Scapozza, C., and Hauck, C. Petrophysical joint inversion of electrical resistivity and refraction seismic applied to alpine permafrost to image subsurface ice, water, air, and rock contents. Frontiers in Earth Science, 2020, submitted. Wagner, F. M., Mollaret, C., Günther, T., Kemna, A., and Hauck, C. Quantitative imaging of water, ice, and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data. Geophysical Journal International, 219 (3):1866-1875, 2019. doi:10.1093/gji/ggz402. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-7489

2020059430 Nesterova, Nina (Tyumen State University, Tyumen, Russian Federation); Khomutov, Artem; Kalyukina, Arina and Leibman, Marina. The specificity of thermal denudation feature distribution on Yamal and Gydan Peninsulas, Russia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-746, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Thermal denudation is a combination of the processes responsible for the formation of retrogressive thaw slumps (cryogenic earth flows) and thermocirques. Thermocirques are the depressions with a semi-circle shape resulting from tabular ground ice thaw. Environments characteristic of Central parts of Yamal and Gydan peninsulas forming the so called Kara sub-latitudinal transect, are favorable to activation of thermal denudation. The key factors are continuous permafrost distribution and shallow occurrence of tabular ground ice. An increase in ground temperature and active layer thickness in 2012-2013 cause the intensification of thermal denudation along Kara sub-latitudinal transect. Field studies in the area of "Vaskiny Dachi" research station as well as remote sensing of 2018 data demonstrates the presence of both active and stabilized thermocirques during. This research presents preliminary results of collecting and analyzing the distribution of more than 400 landforms caused by thermal denudation identified in central Yamal and central Gydan peninsulas. Coastal thermodenudation landforms were not taken into account to exclude the influence of wave erosion in this study. Such work became possible due to free of charge satellite images with a very high spatial resolution available at the service Yandex.Maps (URL: https://yandex.ru/maps/). In Yamal peninsula, we identified 63 active and 53 stabilized thermodenudation landforms, in Gydan peninsula, 169 active and 166 stabilized, respectively. Active thermodenudation features concentrate in the western and southern parts of central Yamal, while stabilized dominate in western and central parts. In central Gydan both active and stabilized features of thermal denudation are located at northwestern part and are distributed more evenly compared to Yamal. Northern border of all identified thermodenudation features for both Yamal and Gydan peninsulas is located at 71 degrees North, and the southern border at 69 degrees North. Despite the difficulties of visual interpretation of thermal denudation features, we defined the majority of them as thermocirques, most of which are located along lake coastlines. Such indication was also confirmed by in-situ data collected during multiyear field campaigns in the study area. These results reveal a prevalence of thermal denudation features in the study area and the collected data gives us an opportunity for spatial analysis of their distribution. The reported study was partially funded by RFBR according to the research project #18-05-60222 [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-746

2020059445 Patzner, Monique S. (University Tuebingen, Center for Applied Geoscience, Tubingen, Germany); Logan, Merritt; Mueller, Carsten W.; Joss, Hanna; Anthony, Sara E.; Scholten, Thomas; Byrne, James M.; Borch, Thomas; Kappler, Andreas and Bryce, Casey. Organic carbon sorbed to reactive iron minerals released during permafrost collapse [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1465, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The release of vast amounts of organic carbon during thawing of high-latitude permafrost is an urgent issue of global concern, yet it is unclear what controls how much carbon will be released and how fast it will be subsequently metabolized and emitted as greenhouse gases. Binding of organic carbon by iron(III) oxyhydroxide minerals can prevent carbon mobilization and degradation. This "rusty carbon sink" has already been suggested to protect organic carbon in soils overlying intact permafrost. However, the extent to which iron-bound carbon will be mobilized during permafrost thaw is entirely unknown. We have followed the dynamic interactions between iron and carbon across a thaw gradient in Abisko (Sweden), where wetlands are expanding rapidly due to permafrost retreat. Using both bulk (selective extractions, EXAFS) and nanoscale analysis (correlative SEM and nanoSIMS), we found that up to 19.4±0.7% of total organic carbon is associated with reactive iron minerals in palsa underlain by intact permafrost. However, during permafrost collapse, the rusty carbon sink is lost due to more reduced conditions which favour microbial Fe(III) mineral dissolution. This leads to high dissolved Fe(II) (2.93±0.42 mM) and organic carbon concentrations (480.06±34.10 mg/L) in the porewater at the transition of desiccating palsa to waterlogged bog. Additionally, by combining FT-ICR-MS and greenhouse gas analysis both in the field and in laboratory microcosm experiments, we are currently determining the fate of the mobilized organic carbon directly after permafrost collapse. Our findings will improve our understanding of the processes controlling organic carbon turnover in thawing permafrost soils and help to better predict future greenhouse gas emissions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1465

2020059429 Pogojeva, Maria (State Oceanographic Institute, Moscow, Russian Federation); Yakushev, Evgeniy; Petrov, Ilya; Yaeski, Evgeniy and Polukhin, Alexander. Study of sea water chemistry changes due to thawing permafrost [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-736, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Influence of thawing permafrost on the chemical properties of the sea water was studied in 2 experiments organized in Svalbard in 2017 and 2018. Permafrost samples were collected at an abrasive cliff 10 km west of Longyearbyen. Experiments were focused on identifying the possible changes in concentrations of nutrients, carbonate system parameters and pollutant composition related to permafrost thawing. During the experiment, the samples of permafrost were added to the seawater. The solution was exposed to natural conditions for 24 hours in 2017 and 5 days in 2018 while water samples from the solution were taken at specified time intervals. The results of the experiment show that the sea water composition changes are connected to the permafrost thawing. Data from this experiment allowed us to estimate the total annual supply of nutrients to the Arctic from permafrost thawing by multiplying the change in concentration from this study by the annual eroded permafrost total volume in Siberia. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-736

2020059461 Ran Min (Henan University, College of Environment and Planning, Henan, China). An n-alkane-based Holocene climate reconstruction in the Altai Mountains, northern Xinjiang, China [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3185, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The climate in the Altai Mountains is highly sensitive to large-scale forcing factors because of its special geographic location. Based on n-alkane data of 150 samples and with a chronologic support of 15 accelerator mass spectrometry (AMS) dates from a 600-cm core at GHZ Peat, the Holocene climatic changes in the Altai Mountains were reconstructed. The reconstruction revealed a warming and drying early Holocene (~10,750-~8500 cal. yr BP), a cooling and persistent dry middle Holocene (~8500-~4500 cal. yr BP), and a cooling and wetting late Holocene (~4500-~700 cal. yr BP). The Holocene temperature changes were primarily controlled by the summer solar radiation with a certain time lag in the early Holocene and also modulated by solar activity, and the time lag in the early Holocene was probably resulted from ice and permafrost melting. The Holocene moisture in the southern Altai Mountains was likely modulated by the North Atlantic Oscillations (NAO) or by the Atlantic Multi-centennial Oscillations (i.e., AMO-like) or by temperature, and or by any combination of the three (NAO, AMO-like, and temperature). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3185

2020059456 Rasmussen, Laura Helene (University of Copenhagen, Institute for Geosciences and Natural Resource Management, Copenhagen, Denmark); Ambus, Per; Zhang, Wenxin; Jansson, Per Erik; Michelsen, Anders and Elberling, Bo. Slope hydrology and permafrost; the effect of snowmelt N transport on downslope ecosystem [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2927, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

In the permafrost-affected landscape, surface and near-surface water movement links areas of higher elevation with lowlands and surface water bodies. Water supply is dominated by snow melt and is thus highly seasonal, as most water moves on the frozen surface in spring, passing only a thin layer of thawed soil. Soluble nutrients mobilized by soil thaw may thus be transported laterally from upslope to downslope ecosystems, which in nutrient-limited cold ecosystems may affect vegetation, ecosystem respiration and surface-atmosphere interaction. In a nitrogen (N) limited ecosystem, however, released inorganic N may in reality not travel far downslope. This study quantifies the potential effect of the snowmelt water nutrient transport by tracing dissolved N in meltwater moving downslope on the frozen surface in a W Greenlandic slope with a snow fan supplying meltwater throughout most of the summer. We use the stable isotopes 15N and D applied simultaneously on top of the frozen surface upslope in a combined solution to investigate the behavior of water and dissolved N flow patterns. We further address the effect of season by tracing N supplied in the early thaw season (30 cm to the frozen surface) and in the late thaw season (90 cm to the frozen surface). Monitoring the slope in detail, we then use the numerical coupled heat-and-mass transfer Coup model to simulate the biotics and abiotics of the receiving ecosystem and study the importance of the lateral N input and the effect of increased N transport in a warmer future. About 50% of the N tracer was retained in the ecosystem immediately below injection in the early growing season (30 cm active layer), whereas about 35% was retained in the later growing season (90 cm active layer). Most of the applied 15N was rapidly immobilized by microbes and into the bulk soil, whereas only a few percentages was taken up by the vegetation. D recovery seemed to follow the pattern of microbial N uptake, suggesting that N and D moved physically from the frozen surface and to the immediate subsoil together. Modelling the ecosystem based on measured N and C pool sizes, meteorology, soil temperature and -moisture revealed a large N constrain on vegetation growth. The current observed vegetation could not be explained with the measured pools alone, suggesting an "invisible" source of N to support the observed vegetation. We conclude that a substantial fraction of lateral N input is transported further downslope, but that increases in N release and transport might not affect vegetation immediately, as most supplied N ends in the soil pool. Vegetation in the receiving ecosystem relies on an external N source, which could be dissolved N transported by snowmelt water on the frozen surface. Snowmelt redistribution of N in the landscape may thus be a factor to account for when studying N cycling in a spatial context. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2927

2020059447 Reinosch, Eike (Technische Universität Braunschweig, Institute for Geodesy and Photogrammetry, Brunswick, Germany); Buckel, Johannes; Gerke, Markus; Baade, Jussi and Riedel, Björn. Creating a rock glacier inventory of the northern Nyainqentanglha Range (Tibetan Plateau) based on InSAR time-series analysis [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1605, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The northern Nyainqentanglha range on the southern Tibetan Plateau reaches an elevation of 7150 m and is mainly characterized by a periglacial landscape. A monsoonal climate, with a wet period during the summers and arid conditions during the rest of the year governs the landscape processes. Large parts of the mountain range are considered permafrost due to the high altitude and the associated low air temperature. Rock glaciers, which are bodies of ice-rich debris, are a typical landform. The recently published IPCC report on the cryospheres of high mountain areas highlights the sensitivity of rock glaciers to climate warming and emphasizes the importance of their study. We study the distribution of rock glaciers of the northern Nyainqentanglha range and our aim is to produce an inventory of active rock glaciers based on their surface motion characteristics. The lack of higher order vegetation and the relatively low winter precipitation enable us to employ Interferometric Synthetic Aperture Radar (InSAR) time-series techniques to study both seasonal and multi-annual surface displacement patterns. InSAR is a powerful microwave remote sensing technique, which makes it possible to study displacement from a few millimeters to centimeters and decimeters per year. It is thus suitable to detect sliding and creeping processes related to periglacial landscapes and permafrost conditions on the Earth's surface. We use both Sentinel-1 (2015-2019) and TerraSAR-X ScanSAR data (2017-2019) for our analysis. In this study we differentiate rock glaciers from the surrounding seasonally sliding slopes by their significantly higher surface creeping rates with mean velocities of 5-20 cm yr-1. We also observe that the velocity of rock glaciers is less dependent on the summer monsoon, which allows us to further differentiate between rock glaciers and other landforms. This method could potentially be used to create rock glacier inventories in other remote regions, as long as the snow cover in winter is thin enough to allow continuous InSAR time-series analysis. These rock glacier inventories are necessary to assess the effects of climate change on vulnerable high mountain regions. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1605

2020059467 Romanovskaya, Maria (Lomonosov Moscow State University, Faculty of Geology, Moscow, Russian Federation); Romanovsky, Vladimir and Kuznetsova, Tatiana. Global climate warming; permafrost degradation and expected consequences [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3859, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

At present, the degradation of permafrost caused by climate warming raises serious concerns of scientists and the public around the world. As a result of degradation of permafrost containing a huge amount of organic material and the decomposition of this organic material, the greenhouse effect can increase significantly. Some scientists estimate that the amount of carbon in the permafrost is more than two times than there is in atmospheric carbon dioxide (Schuur E. A. G.et al., 2015). Besides, a large amount of greenhouse gasses, mostly methane, is already contained in watery glacier bottoms, where these gasses build up through anaerobic organic decomposition (Burns R., 2018). Therefore, there are concerns that permafrost thaw and glacier retreat as the Earth warms will lead to new greenhouse gasses being released into the atmosphere, thus further accelerating the global warming process. Our research devoted to this problem was carried out at the archaeological Upper Paleolithic site Divnogorie 9 (50.9649° N, 39.3031° E) in the National Park "Divnogorie". Our study area occupies the southern part of the Middle Russian Upland (the East European Plain). It has experienced several Quaternary glaciations: the Don, Dnepr, Moscow, and Valdai Glaciations. The facts of the presence of permafrost and its degradation during the late Pleistocene and Holocene are established here as well. The site is located at the right bank of the Tikhaya Sosna River, a right tributary of the Don River. The Don River basin is a world known area because of high concentration of the Upper Paleolithic archaeological sites here - Kostenki-Borshevo district (51°23'40" N, 39°30'31"E) which contains 26 open-air mammoth remnant sites (38-18 ka BP). Divnogorie 9 is an unique site in Europe which is well-known for numerous findings of fossilized equestrian remains of wild horses - more than eight thousands samples. Our most detailed study of the Quaternary deposits was carried out at a 18-m thick section. Bones are concentrated in seven layers (levels). This section exposes several paleosol layers, as well. Estimates of the radiocarbon age of the fossils and paleosol layers here yielded 14-12 ka BP. We studied the organic carbon from paleo-soils of Divnogorie 9. The abundant presence of such large grazers as horses and especially mammoths during the Late Pleistocene supports the widespread existence of high productivity grasslands and organic-rich soils. However, the results of our analysis do not show a significant amount of organic carbon in these paleo-soils at the present. It may possibly be an indication that the originally carbon rich permafrost and subglacial deposits lost their carbon upon permafrost thaw and glacial retreat during the transition from the last glaciation to the Holocene. This ancient carbon was massively released into the atmosphere and to the aquatic systems during that time. At the same time, there were not widespread catastrophic consequences to the Earth's environment except possibly for the extinction of mammoths and other large fauna in the arctic and subarctic. These results provide some cautious optimism about the severity in current amount of changes and consequences thereof. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3859

2020059443 Ruggiero, Livio (National Institute of Geophysics and Volcanology, Rome, Italy); Sciarra, Alessandra; Mazzini, Adriano; Mazzoli, Claudio; Romano, Valentina; Tartarello, Maria Chiara; Florindo, Fabio; Ascani, Massimiliano; Wilson, Gary; Dagg, Bob; Hardie, Richard; Anderson, Jacob; Worthington, Rachel; Lupi, Matteo; Bigi, Sabina; Ciotoli, Giancarlo; Graziani, Stefano; Fischanger, Federico and Sassi, Raffaele. SourcE and impact of greeNhousE gases in AntarctiCA; the SENECA Project [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1431, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Current global climate changes represent a threat for the stability of the polar regions and may result in cascading broad impacts. Studies conducted on permafrost in the Arctic regions indicate that these areas may store almost twice the carbon currently present in the atmosphere. Therefore, permafrost thawing may potentially cause a significant increase of greenhouse gases concentrations in the atmosphere, exponentially rising the global warming effect. Although several studies have been carried out in the Arctic regions, there is a paucity of data available from the Southern Hemisphere. The Seneca project aims to fill this gap and to provide a first degree of evaluations of gas concentrations and emissions from permafrost and/or thawed shallow strata of the Dry Valleys in Antarctica. The Taylor and Wright Dry Valleys represent one of the few Antarctic areas that are not covered by ice and therefore represent an ideal target for permafrost investigations. Here we present the preliminary results of a multidisciplinary field expedition conducted during the Antarctic summer in the Dry Valleys, aimed to collect and analyse soil gas and water samples, to measure CO2 and CH4 flux exhalation, to investigate the petrological soil properties, and to acquire geoelectrical profiles. The obtained data are used to 1) derive a first total emission estimate for methane and carbon dioxide in this part of the Southern Polar Hemisphere, 2) locate the potential presence of geological discontinuities that can act as preferential gas pathways for fluids release, and 3) investigate the mechanisms of gas migration through the shallow sediments. These results represent a benchmark for measurements in these climate sensitive regions where little or no data are today available. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1431

2020059431 Saidaliyeva, Zarina (University of Reading, Department of Geography and Environmental Science, Reading, United Kingdom); Shahgedanova, Maria; Wade, Andrew; Yapiyev, Vadim; Kapitsa, Vassiliy; Kasatkin, Nikolay and Severskiy, Igor. Characterising water sources in glacierized catchments in the northern Tien Shan using stable isotopes [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-807, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Kishi and Ulken Almaty rivers drain glacierized catchments in the northern Tien Shan, Kazakhstan. Both rivers supply water for the Almaty agglomeration with population around 2.5 million. Changes in discharge of these [and many other regional] rivers are affected by changes in all components of the cryosphere (seasonal snow, glacier ice, ground ice) as well as precipitation and ground water. Uncertainties of projections of water availability in the context of the observed climatic warming are an important economic and politic issue in this region. Knowledge of the extent, to which discharge of these rivers depends on different sources of nourishment, is important for the formulation of regional adaptation strategies and policies. A comprehensive data set on concentrations of daily values of stable isotopes of oxygen and hydrogen, temperature, precipitation, and discharge was collected in both catchments in 2017 and 2018 in order to characterize contribution of different sources of water to total discharge. There is a clear correlation between isotopic concentrations in stream water with temperature, precipitation and discharge enabling separation between contributions of ground water (d2H=-78.25 ppm; d18O=-11.80 ppm), snow melt (d2H=-84.56 ppm; d18O=-13.20 ppm), and glacial melt (d2H=-78.97 ppm; d18O=-12.41 ppm). Analysis of isotopic signatures of sources of water shows separation between seasonal snow, glacier ice, rock glaciers and permafrost. Following these preliminary results, the sampling programme has been extended in 2019 to the Ulken Almaty and Kishi Almaty (Kazakhstan), Ala-Archa and Chon Kyzyl-Cuu (Kyrgyzstan), Chirchik (Uzbekistan), Varzob-Kofarnihon (Tajikistan) catchments in 2019-2020 enabling the development of the most comprehensive data set on water isotopes in Central Asia. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-807

2020059455 Schmidt, Juditha (University of Oslo, Mathematics and Natural Sciences, Geosciences, Oslo, Norway); Westermann, Sebastian; Etzelmüller, Bernd and Magnin, Florence. The influence of radiative forcing on permafrost temperatures in Arctic rock walls [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2416, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Climate change has a strong impact on periglacial regions and intensifies the degradation of mountain permafrost. This can result in instabilities of steep rock walls as rock- and ice-mechanical properties are modified. Besides altitude and the related air temperature, latitude is a crucial factor, as solar radiation has a strong impact on the energy transfer processes from the atmosphere to the ground. It can differ significantly in intensity and time over latitudinal positions and exposures of frozen rock slopes. In this project, we suggest improving the parametrization of short-wave and long-wave radiation in thermal models for permafrost degradation. To achieve this, we will analyze temperature data of surface temperature loggers from Southern Norway to Svalbard. In total, 37 loggers were installed between 2010 and 2017. The field sites display enormous latitudinal gradients as well as topographic settings. Furthermore, they provide hourly data, allowing us to set up short-stepped time series for examination of solar radiation angles at varying latitudes. The data is used to set up a transient heat-flow model (CryoGrid) to simulate the local thermal regime. The model takes into account varying input of short-wave radiation due to aspect, slope angle and time as well as long-wave radiation under different sky-view factors. Finally, the influence of solar radiation on permafrost degradation in steep rock walls is investigated. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2416

2020059496 Sonnentag, Oliver (Université de Montréal, Département de Géographie, Montreal, QC, Canada); Fouché, Julien; Helbig, Manuel; Gosselin, Gabriel Hould; Detto, Matteo; Connon, Ryan; Quinton, William and Moore, Tim. A thawing boreal peat landscape along the southern limit of permafrost presently is carbon neutral [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6621, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Along the southern limit of permafrost in northwestern Canada rising air temperatures have caused widespread land cover changes at unprecedented rates. A prominent change includes thermokarst wetland expansion at the expense of black spruce-dominated boreal forest stands due to the permafrost thaw-induced collapse of peat plateaus. We present a multi-year (2013-2017) net ecosystem carbon (C) balance (NECB, g C m-2 year-1) at Scotty Creek near Fort Simpson, NT. The highly fragmented study site is dominated by permafrost-free wetlands and forested permafrost peat plateaus. Eddy covariance measurements of net ecosystem carbon dioxide (CO2) and methane (CH4) exchanges (2013-2017) are complemented by discharge (2014-2016) and water chemistry monitoring (2015 and 2016) at the outlets of three small headwater catchments (<0.5 km2) draining the eddy covariance footprint area. In addition to net ecosystem CO2 and CH4 exchanges, the NECB includes the export of dissolved C (DC) as the sum of inorganic and organic C (DIC and DOC), free CO2 and CH4 through runoff, and the estimated import of DOC through precipitation. We use absorbance spectroscopy for dissolved organic matter (DOM) characterization to distinguish different DOM sources among catchments and characteristic land cover types. Between 2013 and 2017, the NECB varied between a weak net C source (~16 ±5 g C m-2 year-1) and sink (~-22 ±5 g C m-2 year-1) in 2015 and 2013, respectively, with a mean value of -1 ±7 g C m-2 year-1. The net C sink-source strength was largely controlled by variations in net CO2 exchange, ranging between a weak net CO2 sink (~-29 ±3 g C m-2 year-1) and source (~8 ±4 g C m-2 year-1) in 2015 and 2013, respectively. In contrast, our study site was a persistent annual net CH4 source (~8 ±1 g C m-2 year-1). Compensated by the import of DOC through precipitation, DC exported from the three catchments was a negligible component of the NECB. There were no significant differences in DOC concentrations and absorbance indices among catchments, and thawed and frozen land cover types, overall illustrating high DOM aromaticity (SUVA254= 3.3 ± 0.6 L mg-1 m-1) and high molecular weight (a254:a365 = 4.3 ± 0.3) characteristic for peatlands and peat-dominated landscapes outside the circumpolar permafrost region. We conclude that a rapidly thawing boreal peat landscape along the southern limit of permafrost presently appears to be C neutral. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6621

2020059438 Stella, Elisa (Consiglio Nazionale delle Ricerche, Polar Sciences Institute, Venice, Italy); Mari, Lorenzo; Barbante, Carlo; Gabrieli, Jacopo and Bertuzzo, Enrico. Spatiotemporal influence of permafrost thaw on anthrax diffusion [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1184, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The recent 2016 outbreak of anthrax disease affecting reindeer herds in Siberia has been associated to the presence of old infected carcasses released from thawing permafrost, underlying the emerging character of such disease in the Arctic region due to climate change. Anthrax occurs in nature as a global zoonotic and epizootic disease caused by the spore-forming bacterium Bacillus anthracis. It principally affects herbivores and causes high animal mortality. Transmission occurs mainly via environmental contamination through spores which can remain viable in permafrost for many decades. We propose and analyze a novel epidemiological model for anthrax transmission specifically tailored for the Arctic region. It conceptualizes the transmission of disease between susceptible and infected animals in the presence of environmental contamination, considering also herding practices (e.g. seasonal grazing) and the seasonal environmental forcing caused by thawing permafrost. We performed stability analyses and implemented Floquet theory for periodically forced systems, and therefore applied our model to the 17-year-long records of permafrost thawing depth available at the Lena River Delta (northern Siberia). Accordingly, in order to spatialize potential anthrax incidence and consequently the possible hazardous areas in the Arctic, we used the Maximum Entropy (Maxent) approach considering environmental variables and, in particular, accounting for current and expected permafrost thawing rates. Results show how temporal variability of grazing and thawing may influence and favor sustained anthrax transmission. Also, particularly warm years are associated to increased risk of anthrax incidence. Accordingly, we show that such risk could be mitigated with specific precautions involving herding practices, for example by anticipating or postponing seasonal grazing. Finally, a spatial map of the potential Arctic areas at risk is presented, providing a tool for local authorities in view of eventual targeted prevention measures. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1184

2020059500 Stimmler, Peter (Universtität Bayreuth, Bayreuth, Germany). Future Arctic soil nutrient availability and microbial community structure [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6870, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The Arctic permafrost soils are very diverse in regard to parent material, geobiological composition and genesis. There is sparse knowledge about nutrient availability in Arctic soil and it was found that the permafrost layer differs in nutrient availability compared to the active layer. Recently, it was shown that elements like Si, Ca and P are potentially affecting the greenhouse gas from Arctic soil. However, it is not known how those elements are distributed in Arctic soils for a larger dataset. Furthermore, it is unclear whether regional differences in the availability of those elements or a change in availability due to permafrost thaw is changing microbial decomposer community. Therefore, we analyzed 445 soil depth profiles around the Arctic regarding different element availabilities. Furthermore, we conducted an incubation experiment to measure the effect of different Si, Ca and P availabilities on the structure of the microbial decomposer community. We found large differences in the availability of Si, Ca, Al, Fe and P in the layers of the panarctic permafrost soils from Canada, Alaska, Russia, Scandinavia, Greenland and Svalbard. There are differences in the distribution of Ca and Si pools over the panarctic permafrost soils. Especially the availability of P is directly linked to the concentration of Ca and Si and the presence of Al and Fe based minerals. With rising temperatures, the thaw depth of the upper horizon may increase and elements stored in deeper layers become potentially mobilized. These processes modify the nutrient availability for microorganisms and by this the production of greenhouse gases like CO2 and CH4. The community structure of bacteria and fungi is related to the availability of Ca and Si. With modified availabilities of Si and Ca, we found direct linear correlations in the changes of the microbial structure at the phylum level for Greenlandic soils. These changes depend on the origin of the soil and the original availability of Ca and Si. We found direct links between the share of gram-positive bacteria and the Ca concentration in both soils and the production of greenhouse gases. The availabilities of these elements may be helpful for better predicting greenhouse gases fluxes in the Arctic as well as element transfer to marine systems. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-6870

2020059517 Stolpmann, Lydia (Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Morgenstern, Anne; Boike, Julia; Fritz, Michael; Herzschuh, Ulrike; Dvornikov, Yury; Heim, Birgit; Lenz, Josefine; Coch, Caroline; Larsen, Amy; Anthony, Katey Walter; Arp, Christopher; Jones, Benjamin; Frey, Karen and Grosse, Guido. First pan-Arctic assessment of dissolved organic carbon concentration in permafrost-region lakes [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8174, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost-region lakes are dynamic landscape systems and play an important role for climate change feedbacks. Lake processes such as mineralization and flocculation of DOC, one of the main carbon fraction in lakes, contribute to the global carbon cycle. These processes are in focus of climate research but studies have been limited in geographic extent. We synthesized published datasets and unpublished datasets from the author team totaling 1,691 water samples from 1,387 lakes across the Subarctic and Arctic in permafrost regions of Alaska, Canada, Siberia, and Greenland to provide first insights for linkages between DOC concentration to the basin. In our synthesis, we find regional differences in DOC concentration of permafrost-region lakes. We focussed on relations between lake DOC concentration and latitude, permafrost zones, ecoregions, lake surrounding deposit type, and ground ice classification of each lake basin. Additionally, we analysed the lake surrounding soil organic carbon content from 0-100 cm depth and 0-300 cm depth. Individual lake DOC concentrations of our dataset range from below detection limit assigned to 0 mg L-1 (North Slope, Alaska) to 1,130 mg L-1 (Yukon Flats, Alaska). We found regional median lake DOC concentrations of 18.8 mg L-1 (Greenland, n=25), 12.2 mg L-1 (Alaska, n= 1,135), 9.6 mg L-1 (Siberia, n=252), and 7.2 mg L-1 (Canada, n=279). Lakes in the isolated permafrost zone had the highest median DOC concentration compared to lakes in the sporadic, discontinuous, and continuous permafrost zones. Our synthesis shows increasing lake DOC concentration with decreasing latitude and, due to a larger availability of biomass and organic carbon, a significant relationship of lake DOC concentration and ecoregion of the lake. We found higher lake DOC concentrations in boreal permafrost sites compared to tundra sites. About 22% of lakes in our dataset are located in regions with ice-rich syngenetic permafrost deposits (yedoma). Because yedoma contains large amounts of organic carbon, we assumed to find higher DOC concentrations in yedoma lakes compared to non-yedoma lakes. Our analysis shows a significant relationship of lake DOC concentration and surrounding deposit type but not a higher DOC concentration in yedoma lakes compared to non-yedoma lakes. Finally, we found a relationship of soil organic carbon content from 0-100 cm depth and lake DOC concentration. In contrast, a comparison of soil organic carbon content from 0-300 cm depth and lake DOC concentration shows no significant correlation. This was also found for ground-ice content and lake DOC concentration. Our dataset of lakes across the Arctic shows that the DOC concentration of a lake strongly depends on its environmental properties. This dataset will be fundamental to establish a pan-Arctic lake DOC pool for estimations of the impact of lake DOC on the global carbon cycle and further on climate change. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8174

2020059485 Teufel, Bernardo (McGill University, Montreal, QC, Canada) and Sushama, Laxmi. Abrupt changes across the Arctic permafrost region endanger northern development [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-5847, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Extensive degradation of near-surface permafrost is projected during the 21st century, which will have detrimental effects on northern communities, ecosystems and engineering systems. This degradation will expectedly have consequences for many processes, which most previous modelling studies suggested would occur gradually. Here, we project that soil moisture will decrease abruptly (within a few months) in response to permafrost degradation over large areas of the present-day permafrost region, based on analysis of transient climate change simulations performed using a state-of-the-art regional climate model. This regime shift is reflected in abrupt increases in summer near-surface temperature and convective precipitation, and decreases in relative humidity and surface runoff. Of particular relevance to northern systems are changes to the bearing capacity of the soil due to increased drainage, increases in the potential for intense rainfall events and increases in lightning frequency, which combined with increases in forest fuel combustibility are projected to abruptly and substantially increase the severity of wildfires, which constitute one of the greatest risks to northern ecosystems, communities and infrastructure. The fact that these changes are projected to occur abruptly further increases the challenges associated with climate change adaptation and potential retrofitting measures. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-5847

2020059469 Thonicke, Kirsten (Potsdam Institute for Climate Impact Research, Potsdam, Germany); Billing, Maik; Von Bloh, Werner; Sakschewski, Boris; Niinemets, Ulo; Penuelas, Josep; Cornelissen, J. Hans C.; van Bodegom, Peter; Shaepman, Michael E.; Schneider, Fabian D. and Walz, Ariane. Simulating co-existence of functionally diverse trees in European natural forests with LPJmL-FIT [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4100, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

We adopted the flexible trait Dynamic Global Vegetation Model LPJmL-FIT for European natural forests by eliminating bioclimatic limits of Plant Functional Types (PFTs) and replacing prescribed values of functional traits with flexible individual traits. Vegetation dynamics are simulated with permafrost and fire disturbance being considered in the simulation domain. Leaf and stem-economic traits are assigned to individual trees at establishment which then determine plant competition for light and water in a forest patch. We simulate vegetation dynamics in selected natural forests sites and at the Pan-European scale. We quantified functional richness (FR), functional divergence (FDv) and functional evenness (FE) from combinations of functional and structural traits of the simulated individual trees. We find good agreement with observed productivity, biomass and tree height, and spatial PFT and local trait distributions. The latter is compared against TRY observations. We find site-specific trait distributions and spatial gradients of the simulated LES and SES traits to coincide with environmental and competitive filtering for light and water in environments with strong abiotic stress. Where deciduous and needle-leaved trees co-occur in a forest patch, functional richness (potential niche space) is high, and extreme ends of the niche space are occupied resulting in high FDv. Functional divergence declines where the performance of deciduous trees decreases due to increasing environmental stress as simulated along altitudinal and latitudinal gradients. When climate gets cooler, needle-leaved trees become dominant, occupying the extreme ends of the niche space. Under Mediterranean climate conditions, drought increasingly limits tree growth thus niche differentiation becomes more important. Co-existence of functionally diverse trees within and across PFTs emerges from alternative life history strategies, disturbance and tree demography. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4100

2020059440 Tikhonova, Anna (Shirshov Institute of Oceanology, Moscow, Russian Federation) and Merenkova, Sofia. The modern assemblages of benthic foraminifers of the east Siberian sea initial and active methane seeps zones of the Laptev Sea [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1337, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

We present the initial data on the distribution of benthic foraminifera (BF) on East Siberian Sea shelf. Previous researchers analyzed BF in the sediment cores from the continental slope and basin areas of the East Siberian Sea (Wollenburg et al., 2000; Mackensen et al., 2014; Barrientos et al., 2018) but not from central shelf. Last year we received boxcorer samples of bottom sediments from the shelf of the East Siberian Sea and the Laptev Sea during the 78th cruise of research vessel Akademik Mstislav Keldysh (September-October 2019). We examined the species composition of BF assemblages of Rose Bengal-stained surface samples from 2 stations in the East Siberian Sea and 7 stations in the Laptev Sea, and compared this data set with an existing data set along the East Siberian Sea and the Laptev Sea. Recent studies (Shakhova et al., 2007, 2009, 2015; Nicolsky et al., 2009) state that the East Siberian Sea is one of the largest sources of methane emission into the atmosphere due to degradation of permafrost, ice complex retreat and decaying gas hydrates deposits. Perhaps this has an impact on the species composition of the BF assemblages and the morphological changes and defects of their shells, which we have identified. Samples from active methane seeps of the Laptev Sea have been studied to identify the relationship between methane emission and the reaction of benthic foraminifera. This data have been compared with "background" (i.e. non-venting, without any methane seeps activity) stations of the Laptev Sea and the East Siberian Sea. The identified features require further detailed study. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1337

2020059427 Timofeeva, Maria; Goncharova, Olga and Matyshak, Georgy. Hydrological conditions and peat constitution effect on DOC leaching from permafrost-affected soils; model experiment (western Siberia, Russia) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-590, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The main aim of our study was to determine the relationship among peat type, water regime and the quantity and composition of water borne carbon export. The research site was located in the discontinuous permafrost zone (N65°18', E72°52'). Monoliths of various peat soils were collected in summer 2019 for a laboratory experiment. The experiments were carried out with 6 types of monoliths (oligotrophic fibric peat; oligotrophic hemic peat with lichen debris; eutrophic hemic peat with reindeer moss debris; eutrophic sapric peat; eutrophic sapric peat with a burnt horizon; oligotrophic fibric peat, underlied with sand). We try to understand how organic matter is leached from peat soils with different constitution and different degree of decomposition. In the model experiment, we simulated 3 types of hydrological conditions. Soil monoliths were watered, and the contents of DOC and POC were determined in the collected soil waters. 1. Simulation of the moderate rainfall (70 mm) by adding distilled water during the week. DOC in this case ranged from 44,2±3.0 mg/l in oligotrophic peat to 80,6±28,7 mg/l in eutrophic peat. 2. The simultaneous flow of large quantities of water, simulating prolonged rainfall or spring snowmelt. In this case DOC content leaching from fibric oligotrophic peat didn't change much while DOC leaching from sapric eutrophic peat decreased in comparison with moderate rainfall. 3. During modeling short stagnant regimen (spring conditions) we observed increase DOC, especially in sapric eutrophic peat (up to 291,0±11,3 mg/l). The mineral horizon under the peat layer reduced the rate of leaching of organic substances from the soil. Our results indicate the significant role of both the peat constitution and hydrological regime of soils on the rate and amount of organic matter entering the hydrological basin from peat permafrost-affected soils. The data can be used to simulate the dynamics of permafrost ecosystems with changing climatic parameters or with the activation of anthropogenic load. This research was supported by the Russian Foundation for Basic Research (Grant 18-04-00952) [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-590

2020059432 Tolmanov, Vasily (Lomonosov Moscow State University, Cryolithology and Glaciology, Moscow, Russian Federation). Thermoerosion process on Tazovskiy Peninsula; factors and dynamics [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-825, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Cryogenic processes, especially "warm" significantly affect the reliability of the northern infrastructure. Thermoerosion is the process of destruction of the banks or ground massives constructed by the permafrost and ground ice, by thermal and mechanical influence of the running water. Tazovskiy peninsula, where the largest gas production facilities are located, is referred in Russia as "The kingdom of the thermoerosion". The geodetical level of the surface on Tazovskiy peninsula varies between 15-20 m. and 60-80 m., but the thermoerosion processes are very active. The area exposed to thermoerosion was 10-15% of the territory in the beginning of 1980th and actively enlarges. The period of the maximum active layer thaw depth is August, when the precipitation amount is the highest, which coupled with the raising trend of the air temperature (0.8°C per decade) (IPCC, 2014) and growing temperature (up to 1.5-2° warmer) of the upper permafrost layers, results in the ground destruction. The appearance of the thermoerosion process we clarify by the highly blurred sediments at the surface: the upper Quaternary silty iced (up to 40-60%) sands or sandy loams. The other auspicious factor is polygonal ice systems formed by iced peatlands (2-3 m of depth) serving as the positions of the future thermoerosion cuts. Our investigations showed that in the raising probability of the erosion occurrence, weak root systems of the shrubs and grasses can not cope with the process. The factor that significantly intensify the speed of the thermoerosion is active snow melting in May-beginning of June. Together with increasing snowiness of the winters it additionally activates the processes of gullies formation. The conducted field works during the snowmelt revealed lumpy collapsing of the big ground blocks near the lateral sides of the watercourses which was the main reason of erosion speed boost. The blocks remained frozen, the rate of the lateral erosion was 15-20 cm/per day, the widths was up to 1.5-2 m. We started to observe dynamics of the thermoerosion in early 2000's. The rate of the gullies growing on the right side of the r. Nyudya-Adlyurdyepoka was up to 10 m. per year. The length of the gully was 60 m. in 2006 and it was U-shaped. In 2016 the gully had length of 80 m.. The profile of the gully became V-shape everywhere, the gully was branched out and the steepness of the edges increased. More detailed characteristics of the other representative gullies development will be consider in this research. Our study showed that construction and exploitation of the road systems between the deposit fields entailed the formation of linear overmoistured zones near the roads and formed new thermoerosion systems. Satellite data showed that territory occupied by thermoerosion processes raised by 15-20% in the last 40 years. It is due to climatic changes, the active exploitation of the technogenic systems on iced and easily blurred soils. This work is supported by the RFBR project a-18-05-60080 "Dangerous nival-glacial and cryogenic processes and their impact 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-egu2020-825

2020059441 Tsai, Ya-Lun (German Aerospace Center, German Remote Sensing Data Center, Wessling, Germany); Uereyen, Soner; Dietz, Andreas; Kuenzer, Claudia and Oppelt, Natascha. Global snow cover extent mapping using Sentinel-1 [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1383, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Seasonal snow cover extent (SCE) is a critical component not only for the global radiation balance and climatic behavior but also for water availability of mountainous and arid regions, vegetation growth, permafrost, and winter tourism. However, due to the effects of the global warming, SCE has been observed to behave in much more irregular and extreme patterns in both temporal and spatial aspects. Therefore, a continuous SCE monitoring strategy is necessary to understand the effect of climate change on the cryosphere and to assess the corresponding impacts on human society and the environment. Nevertheless, although conventional optical sensor-based sensing approaches are mature, they suffer from cloud coverage and illumination dependency. Consequently, spaceborne Synthetic Aperture Radar (SAR) provides a pragmatic solution for achieving all-weather and day-and-night monitoring at low cost, especially after the launch of the Sentinel-1 constellation. In the present study, we propose a new global SCE mapping approach, which utilizes dual-polarization intensity-composed bands, polarimetric H/A/a decomposition information, topographical factors, and a land cover layer to detect the SCE. By including not only amplitude but also phase information, we overcome the limitations of previous studies, which can only map wet SCE. Additionally, a layer containing the misclassification probability is provided as well for measuring the uncertainty. Based on the validation with in-situ stations and optical imagery, around 85% accuracy of the classification is ensured. Consequently, by implementing the proposed method globally, we can provide a novel way to map high resolution (20 m) and cloud-free SCE even under cloud covered/night conditions. Preparations to combine this product with the optical-based DLR Global SnowPack are already ongoing, offering the opportunity to provide a daily snow mapping service in the near future which is totally independent from clouds or polar darkness. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1383

2020059449 Ulrich, Mathias (University of Leipzig, Institute for Geography, Leipzig, Germany) and Habeck, J. Otto. Permafrost dynamics and indigenous land use; tracing past and current landscape conditions and effects of environmental change in Sakha/Yakutia, Russia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1840, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Arctic and Subarctic regions are currently experiencing a more rapid warming than other parts of the Earth. This trend is of particular salience for the Republic of Sakha/Yakutia (East Siberia, Russia) - a vast region where both permafrost research and social science research on animal husbandry have been conducted intensively but thus far separately. Here we are presenting a new project that will combine these disconnected strands and utilize an interdisciplinary approach for examining landscape and land use development under climatic change. Such an approach is topical because effects of past and imminent permafrost degradation on indigenous livelihoods have hitherto been described in rather simplistic terms. The project is designed as a comparative study of two regions in Central and Northeast Sakha/Yakutia. Both areas are susceptible to permafrost degradation, but under divergent zonal and socio-economic conditions (taiga vs. tundra; cattle and horse vs. reindeer husbandry). A key element of landscape dynamics in both regions is thermokarst, i.e. the thawing of ice-rich deposits leading to soil subsidence and lake formation. Thaw lakes mark an early phase of thermokarst formation; they can serve as indicators for changes in climate, permafrost and vegetation. On the one hand, thermokarst processes have taken place in earlier millennia, notably in the Pleistocene/Holocene transition and during the mid-Holocene climate optimum; in the long run, this has led to the formation of grass-rich depressions (known as alas), creating the preconditions for cattle farming in Central Sakha/Yakutia which emerged at least 500 years ago. On the other hand, thermokarst processes occur at present in connection with global warming; the effects of the latter are likely to produce unprecedented rapid change, with very grave consequences for local land users. In the analysis of landscape development and land use, we distinguish between two periods: before and after the start of pastoralism and farming. We test the hypothesis that landscape and land-use changes occurred at different scales and speeds in the two zonal settings (Central vs Northeastern Sakha/Yakutia). Furthermore, we postulate that existing forms of land use are going to influence landscape development in different ways: They (i) correlate with, (ii) exacerbate or (iii) neutralize the effects of climate change (owing to different feedback mechanisms). Finally, taking into account the most important demographic, economic and socio-cultural influences, the project will contribute to formulating parameters for modelling the future risks that permafrost degradation exerts on rural communities. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1840

2020059444 van Huissteden, Ko (Vrije Universiteit, Earth Sciences Department, Amsterdam, Netherlands); Teshebaeva, Kanayim; Cheung, Yuki; Noorbergen, Hein and van Persie, Mark. Climate change and the carbon cycle of frozen floodplains [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-1445, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Permafrost-affected river plains are highly diverse in discharge regime, floodplain morphology, channel forms, channel mobility and ecosystems. Frozen floodplains range from almost barren systems with high channel mobility, to extensive wetland areas with low channel mobility, abundant abandoned channels, back-swamps and shallow floodplain lakes. Floodplain processes are increasingly affected by climate-induced changes in river discharge and temperature regime: changes in the dates of freeze-up, break-up and spring floods, and changes in the discharge distribution throughout the year. In permafrost floodplains, changes in flooding frequency, flood height and water temperature affect active layer thickness, subsidence and erosion processes. Data from the Northeast Siberian Berelegh river floodplain (a tributary to the Indigirka river) demonstrate that increasing spring flood height potentially causes permafrost thaw, soil subsidence and increase of the floodplain area. INSAR (interferometric synthetic aperture radar) data indicate that poorly drained areas in this region are affected by soil subsidence. Morphological evidence for subsidence of the river floodplain is abundant, and river-connected lakes show expansion features also seen in thaw lakes. These floodplain wetland ecosystems are also affected by changes in the discharge regime and permafrost. On the one hand, floodplains are sites of active sedimentation of organic matter-rich sediments and sequestration of carbon. This carbon is derived from upstream erosion of permafrost and vegetation, and from autochthonous primary production. Nutrient supply by flood waters supports highly productive ecosystems with a comparatively large biomass. On the other hand, these ecosystems also emit high amounts of CH4, which may be affected by flooding regime. In the example presented here, the CH4 emission from floodplain wetlands is about seven times higher that the emission from similar tundra wetlands outside the floodplain. The dynamic nature of floodplains hinders carbon and greenhouse gas flux measurements. Better quantification of greenhouse gas fluxes from these floodplains, and their relation with river regime changes, is highly important to understand future emissions from thawing permafrost. Given the difficulties of surface greenhouse gas flux measurements, recent remote sensing material could play an important role here. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-1445

2020059521 Voit, Klaus (University of Natural Resources and Life Sciences, Vienna, Austria); Rechberger, Christina; Fey, Christine; Mair, Volkmar and Zangerl, Christian. Engineering-geological characterisation and activity analysis of a deep-seated rockslide near Laatsch (south Tyrol) [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-8331, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Deep-seated rockslides in Alpine areas are common phenomena, especially if geological and tectonic conditions enable a disintegration of the rock mass extending deep into the ground. Furthermore, the failure process usually is controlled by groundwater flow, permafrost degradation and rock weathering mostly by input of surface water along geological discontinuities as well as by temperature fluctuations. Thereby, extensive slope areas can become unstable and - in the worst case - can endanger population and infrastructure. At the valley entrance of the Münstertal at the stream Rambach (South Tyrol, Italy), close to the national road SS41 ca. road kilometres 6.5, a deep-seated rockslide was formed at a south-facing mountain slope with a gradient of ca. 30-50°. The U-shaped valley was formed by glaciers, whereby the valley floor is filled with alluvial sediments. The rockslide is approx. 400 m wide, measures approx. 700 m in height at its longest extension and comprise a total rock volume of approx. 500,000 m3. The geological bedrock consists of foliated metamorphic rocks (mainly orthogneisses) which partially is covered by talus and glacial sediments. In the past and still continuing, the area was exposed to major tectonic stress due to its close range to the Vinschgau and Schlinig fault zones generating a dense fracture system in the rock mass. Since several years, the highly active rockslide shows displacements of several metres per year. In 2014, the road SS41 was relocated over a length of ca. 800 m to the other side of the Rambach due to ongoing rock fall events. Field surveys conducted at that time already showed clear geomorphological indications for the destabilization of a large area at the mountain ridge by the presence of primary and secondary scarps, tension cracks, and up-hill facing scarps in the slope area ranging up to the mountain ridge. Geological field studies in 2018 and 2019 were carried out to investigate the rockslide geometry and kinematics as well as deformation and failure processes. Quantification of the deformation rates was carried out by multi-temporal terrestrial laser scanning (TLS). From a kinematic point of view, the rockslide can be divided into different slabs of varying activity showing actual deformation rates between approx. 0.3 to 3.6 m per year. The individual slabs show a translational movement behaviour with minor internal deformation. However, also a rotational kinematics along polygonal slip surfaces was observed. Disintegration and formation of slabs mostly takes place along pre-existing steeply dipping joint surfaces. In this contribution, a preliminary geological, geometrical and kinematical model of the current rockslide is presented by the detailed analyses of field mapping and deformation monitoring data. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-8331

2020059459 Wetterich, Sebastian (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Potsdam, Germany); Murton, Julian B.; Toms, Phillip; Wood, Jamie; Blinov, Alexander; Opel, Thomas; Fuchs, Margret C.; Merchel, Silke; Rugel, Georg; Gärtner, Andreas and Savvinov, Grigoriy. Multi-method dating of ancient permafrost of the Batagay megaslump, East Siberia [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-2999, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Dating of ancient permafrost is essential for understanding permafrost stability and interpreting past climate and environmental conditions over Pleistocene timescales but faces substantial challenges to geochronology. Here, we date permafrost from the world's largest retrogressive thaw slump at Batagay in the Yana Upland, East Siberia (67.58 °N, 134.77 °E). The slump headwall exposes four generations of ice and sand-ice (composite) wedges that formed synchronously with permafrost aggradation. The stratigraphy differentiates into a Lower Ice Complex (IC) overlain by a Lower Sand Unit, an Upper IC and an Upper Sand Unit. Two woody beds below and above the Lower Sand Unit represent the remains of two episodes of taiga forest development prior to the Holocene forest. Thus, the ancient permafrost at Batagay potentially provides one of the longest terrestrial records of Pleistocene environments in western Beringia. We apply four dating methods to the permafrost deposits to disentangle the chronology of the Batagay permafrost archive - optically-stimulated luminescence (OSL) dating of quartz and post-infrared-stimulated luminescence (pIR-IRSL) dating of feldspar as well as accelerator mass spectrometry-based Cl-36/Cl dating of wedge ice and radiocarbon dating of organic material. The age information obtained so far indicates that the Batagay permafrost sequence is discontinuous and that the Lower IC developed well before MIS 7, the overlying Lower Sand Unit formed during MIS 6, and the Upper IC and the Upper Sand Unit formed both during MIS 3-2. Additional sampling for all dating approaches presented here took place in spring 2019, and is part of ongoing research to enhance the geochronology of the exceptional palaeoenvironmental archive of the Batagay megaslump. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-2999

2020059464 Zabelina, Svetlana (Russian Academy of Sciences, N.Laverov Federal Center for Integrated Arctic Research, Arkhangelsk, Russian Federation); Shirokova, Liudmila; Klimov, Sergey; Chupakov, Artem; Lim, Artem; Polishchuk, Yuri; Polishchuk, Vladimir; Bogdanov, Alexander; Muratov, Ildar; Guerin, Frederic; Karlsson, Jan and Pokrovsky, Oleg. Carbon emission related to thermokarst processes in wetlands of NE European tundra [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-3452, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Emission of greenhouse gases (GHG) from inland waters is recognized as highly important and understudied part of terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in permafrost regions containing a vast amount of surface C in frozen peatlands. This is especially true for NE European peatlands, located within sporadic to discontinuous permafrost zone which is highly vulnerable to thaw. For a first quantification of the C emission from lentic waters of the Bolshezemelskaya Tundra (BZT, 200,000 km2), we measured CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds and thermokarst lakes ranging from 0.5 to 5x106 m2 in size. The CO2 fluxes decreased by an order of magnitude when lake size increased by > 3 orders of magnitude, while CH4 fluxes showed large variability that were not related to lake size By using a combination of Landsat-8 and GeoEye-1 images we found that lakes cover 4% of BZT, and calculated the overall C emission (CO2+CH4) from the lakes of the territory to 3.8 Tg C y-1 (99% C-CO2, 1% C-CH4). Large lakes (> 10,000 m2) dominated GHG emissions whereas small thaw ponds (< 1000 m2) had a minor contribution to overall lake surface area (< 2%) and GHG emission (< 5% of CO2; < 20% of CH4). The results suggest that, if permafrost thaw in NE Europe leads to the disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, this will decrease GHG emission from lentic waters of this region. However, due to temporal and spatial variations of C fluxes, the uncertainties on areal GHG emission are at least one order of magnitude in small thaw ponds and a factor of 3 to 5 in thermokarst lakes. This work was supported by the State Task AAAA-A18-118012390200-5, RFBR grant No. 18-05-70087 "Arctic Resources", 19-07-00282, 18-45-860002, 18-45-703001 and 18-47-700001, and the Swedish Research Council (grant no. 2016-05275). [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-3452

2020059491 Zhao Lin (Nanjing University of Information Science & Technology, Nanjing, China); Hu Guojie; Zou Defu; Li Ren; Sheng Yu and Pang Qiangqiang. Status, changes and impacts of permafrost on Qinghai-Tibet Plateau [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-6246, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

Due to the climate warming, permafrost on the Qinghai-Tibet Plateau (QTP) was degradating in the past decades. Since its impacts on East Asian monsoon, and even on the global climate system, it is fundamental to reveal permafrost status, changes and its physical processes. Based on previous research results and new observation data, this paper reviews the characteristics of the status of permafrost on the QTP, including the active layer thickness (ALT), the spatial distribution of permafrost, permafrost temperature and thickness, as well as the ground ice and soil carbon storage in permafrost region. The results showed that the permafrost and seasonally frozen ground area (excluding glaciers and lakes) is 1.06 million square kilometers and 1.45 million square kilometers on the QTP. The permafrost thickness varies greatly among topography, with the maximum value in mountainous areas, which could be deeper than 200 m, while the minimum value in the flat areas and mountain valleys, which could be less than 60 m. The mean value of active layer thickness is about 2.3 m. Soil temperature at 0-10 cm, 10-40 cm, 40-100 cm, 100-200 cm increased at a rate of 0.439, 0.449, 0.396, and 0.259°C/10a, respectively, from 1980 to 2015. The increasing rate of the soil temperature at the bottom of active layer was 0.486 °C/10a from 2004 to 2018. The volume of ground ice contained in permafrost on QTP is estimated up to 1.27´104 km3 (liquid water equivalent). The soil organic carbon stored in the upper 2 m of soils within the permafrost region is about 17 Pg. Most of the research results showed that the permafrost ecosystem is still a carbon sink at the present, but it might be shifted to a carbon source due to the loss of soil organic carbon along with permafrost degradation. Overall, the plateau permafrost has undergone remarkable degradation during past decades, which are clearly proven by the increasing ALTs and ground temperature. Most of the permafrost on the QTP belongs to the unstable permafrost, meaning that permafrost over TPQ is very sensitive to climate warming. The permafrost interacts closely with water, soil, greenhouse gases emission and biosphere. Therefore, the permafrost degradation greatly affects the regional hydrology, ecology and even 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-egu2020-6246

2020059472 Zhu Chenyi (Peking University, Department of Physical Geography and Natural Resources, Beijing, China); Liu Hongyan; Wang Hongya; Feng Siwen and Han Yue. Determinants of ~1000-year woody vegetation dynamics at the southern boreal forest margin in northeast China [abstr.]: in European Geosciences Union general assembly 2020, Geophysical Research Abstracts, 22, Abstract EGU2020-4417, 2020. Meeting: European Geosciences Union general assembly 2020, May 4-8, 2020, World Wide Web.

The most dramatic permafrost degradation is expected to occur at its southernmost distribution, which causes significant vegetation changes in the southernmost boreal forests and consequently affects the carbon stock. To reveal determinants of vegetation change and, in particular, the role of permafrost dynamics, the reconstruction of the long- term vegetation history spanning a warming-cooling cycle is required. Here, we showed that over the last 990 years, vegetation development was characterized by changes in the relative proportions of taxa, such as Larix, Pinus and Corylus, corresponding to the variation in temperature. However, since ~1950 AD, rapid warming has led to the breakdown of the stable relationship among vegetation, climate and permafrost, and the proportion of conifers has shown an increasing trend in the short term due to the influence of permafrost thawing regulated by terrain. In general, we have observed that the coupling system of vegetation, climate and permafrost was stable before ~1950 AD; however, there has been a transition in the most recent rapid warming-induced permafrost thawing. As the southern boundary of permafrost moves northward, it is suspected that the boreal forest in this region will be unstable or may even collapse in the future, and the complete replacement of conifers by broad-leaved trees could greatly reduce the carbon stock in this area by that time. [Copyright Author(s) 2020. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

DOI: 10.5194/egusphere-egu2020-4417

2020055393 Gehringer, Holden M. (Purdue University, Department of Earth, Atmospheric and Planetary Sciences, West Lafayette, IN) and Granger, Darryl E. Glacial and postglacial geomorphology of Tippecanoe County, Indiana [abstr.]: in Geological Society of America, North-Central Section, 54th annual meeting, Abstracts with Programs - Geological Society of America, 52(5), Abstract no. 31-1, May 2020. Meeting: Geological Society of America, North-Central Section, 54th annual meeting, May 18-19, 2020, Duluth, MN.

We used LiDAR topography to map glacial and periglacial features in Tippecanoe County, Indiana, near the southern margin of the Laurentide Ice Sheet. The map reveals a palimpsest of landforms associated with ice advance and retreat. We describe some of these here in chronological order: The area was last glaciated by the East White sublobe, which advanced over older Michigan Lobe till. Radiocarbon dating of a log recovered locally shows that Late Wisconsin ice advanced here at 22,500 +/- 500 radiocarbon years BP (West and Granger, 2018, Indiana Acad. Sci.). The topography is dominated by a NE-SW drainage pattern that follows subglacial tunnel valleys and eskers, and by a subperpendicular set of recessional moraines. A number of features are associated with deglaciation and ice collapse, including rectilinear kames that likely formed in fractured ice; a meandering supraglacial stream channel that cut into the underlying till; and numerous kettle holes. After deglaciation the area was subject to permafrost conditions, as evidenced by widespread thaw lakes and ice-wedge polygons. The county is bisected by the Wabash River, which follows a channel occupied by at least two cataclysmic floods. The older flood likely occurred near the ice margin (Fraser and Bleuer, 1988, GSA Spec. Pap. 229). The younger flood is the Maumee Torrent, released by the collapse of the Fort Wayne moraine near 14,000 radiocarbon years BP (Fullerton, 1980, USGS PP 1089). Cataclysmic flood deposits are distinguished by streamlined bedforms, cross-bar channels, kettles in bar deposits, and megaripple trains. Periglacial features are generally present on the older flood features, but absent on terraces of the Maumee torrent. Finally, the youngest features include parabolic dunes and dune fields formed by westerly winds.

2020057694 Stephens, Connor (Appalachian State University, Department of Geological and Environmental Sciences, Boone, NC) and Evans, Sarah G. Analysis of increased baseflow across northern Eurasian rivers underlain by permafrost [abstr.]: in Geological Society of America, Southeastern Section, 69th annual meeting; Geological Society of America, Northeastern Section, 55th annual meeting, Abstracts with Programs - Geological Society of America, 52(2), Abstract no. 59-13, March 2020. Meeting: Geological Society of America, Southeastern Section, 69th annual meeting; Geological Society of America, Northeastern Section, 55th annual meeting, March 20-22, 2020, Reston, VA.

The Arctic is currently warming at twice the rate of the global average, resulting in increased rates of Arctic river discharge and the thawing of perennially frozen ground known as permafrost. As permafrost thaws, the layer of soil above permafrost that thaws during the summer and refreezes in the winter known as the active layer, increases in depth. An increase in the depth of the active layer is postulated to be one of the main reasons why we have observed increased rates of river discharge in the Arctic. It is important to understand why and at what rate permafrost thaws, as the hydrology of permafrost is also intimately connected with the carbon cycle since thawing permafrost releases stored carbon as methane or carbon dioxide into the atmosphere more readily when soils are unsaturated, further accelerating climate warming. In this study we quantify how changes to Arctic permafrost relate to changes in Arctic river discharge by analyzing daily streamflow records across northern Eurasia for 139 different river discharge stations from 1913 to 2003. We perform a baseflow recession analysis for these stations for the low flow and snow-free months of September and October. We chose these low flow months when streamflow comes from groundwater storage or baseflow to minimize the influence of precipitation and snowmelt from higher elevations. Across all 139 river discharge stations we observe a positive recession flow intercept (a proxy for increasing active layer depth) for the majority of those stations underlain by continuous permafrost, while we see a negative recession flow intercept for stations underlain by less extensive permafrost including discontinuous, sporadic, isolated, and no permafrost regions. This may indicate that active layer is deepening in areas underlain by continuous permafrost which causes an increase in baseflow, while in areas without continuous permafrost, the increased baseflow may be caused by large scale permafrost thawing and an increase in regional hydraulic conductivity, or the ease at which water flows through the ground. The results from this work may help us to understand the changing hydrologic cycle in the Arctic which has implications for carbon cycling as the Arctic continues to warm.

2020054406 Phillips, Stephen C. (University of Texas at Austin, Institute for Geophysics, Austin, TX). Pressure coring in marine sediments; insights into gas hydrate systems and future directions [abstr.]: in Geological Society of America, 2019 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 51(5), Abstract no. 245-3, September 2019. Meeting: Geological Society of America, 2019 annual meeting & exposition, Sept. 22-25, 2019, Phoenix, AZ.

Pressure core barrels were developed to accurately characterize gas hydrate concentration and composition in marine sediments, and were first deployed successfully on Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) expeditions. Gas hydrates are ice-like solids that consist of a gas guest molecule (most commonly methane) within a cage of water molecules, and can can occur in high concentration in continental margin and permafrost sediments. Hydrates represent a large potential energy source, are a potential target for CO2 sequestration, and are a major pool in the global carbon cycle. Collection of samples with intact hydrate and maintaining in situ properties is a key challenge in investigating gas hydrates. A recent focus on deepwater, coarse-grained, high-concentration hydrate reservoirs as a potential energy resource has motivated hydrate drilling and pressure coring expeditions in Japan, India, China, and the U.S., as well as the capability to perform a variety of analyses under pressure and transfer pressurized cores to shore-based laboratories. Pressurized cores can now be analyzed with X-ray imaging, and for physical properties, geomechanical properties, permeability, and microbial activity while maintaining the of samples pressure and temperature within the hydrate stability field. These pressure coring efforts have resulted in an improved understanding of hydrate formation processes, reservoir conditions, and the fundamental properties of hydrate-bearing sediments. Beyond characterization of hydrate systems, preservation of in situ properties and gas content/composition of sediments by pressure coring has the potential to illuminate deep microbial processes, the geomechanical conditions that can influence submarine slope failures, and the properties of hydrocarbon-bearing mudrocks.

2020058669 He, B. B. (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Sheng, Y.; Chou, Y. L.; Hu, X. Y. and Feng, Y. L. Analysis of the embankment stability in permafrost regions based on double strength reduction finite element method: in 2018 international conference on Civil and hydraulic engineering (IConCHE 2018) (Khu, Soon-Thiam; et al.), IOP Conference Series. Earth and Environmental Science, 189(2), Paper no. 022022, illus. incl. 1 table, sect., 34 ref., November 2018. Meeting: 2018 international conference on Civil and hydraulic engineering (IConCHE 2018), Nov. 23-25, 2018, Qingdao, China.

In order to study the embankment stability in permafrost regions, the vertical deepening and horizontal extension of the thaw bulb under the embankment in permafrost regions have been calculated and analyzed based on the double strength reduction finite element method. The vertical depth of the thaw bulb has less impact on the location of longitudinal cracks, and greater impact on the size of cracks on the embankment surface. Moreover, the deeper the vertical depth of the thaw bulb is, the larger the size of cracks becomes. The horizontal extension of the thaw bulb not only impacts on the location of longitudinal cracks on the embankment surface, but also impacts on the size of cracks. There is a critical length for the horizontal extension of the thaw bulb, where the probability of longitudinal cracks is the greatest. When the length is smaller than the critical length, the probability of longitudinal cracks increases with the length increasing; when the length is greater than the critical length, there will be no longitudinal cracks, but the whole embankment tilts to the sunny slope. Copyright Published under licence by IOP Publishing Ltd

DOI: 10.1088/1755-1315/189/2/022022

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