Permafrost Monthly Alerts (PMAs)

2018031998 Gautier, Emmanuèle (Université Paris I Panthéon-Sorbonne, Laboratoire de Géographie Physique, Meudon, France); Dépret, Thomas; Costard, François; Virmoux, Clément; Fedorov, Alexander; Grancher, Delphine; Konstantinov, Pavel and Brunstein, Daniel. Going with the flow; hydrologic response of middle Lena River (Siberia) to the climate variability and change: Journal of Hydrology, 557, p. 475-488, illus. incl. 2 tables, sketch map, 65 ref., February 2018.

Recent observations indicate that over the last decades, climate change has increasingly influenced the frequency, intensity and duration of extreme climatic and hydrologic events. The main aim of this study is to determine the hydrologic response, especially the flood evolution, of the Lena River in Eastern Siberia to ongoing climate change. Draining the coldest region of the Northern Hemisphere, the Lena River is impacted by global warming, which is particularly pronounced in periglacial areas characterized by deep and continuous permafrost. We document the hydrologic variability of the Middle Lena River, first by characterizing trend and stationarity of monthly discharges. Second, we analyze on the basis of the peak over threshold method (POT) the temporal evolution of intensity and duration of three discharge classes: bar-full discharge, bank-full discharge and large floods. Finally, we also determined the dates of the flood beginning and of the flood peak. Data on mean monthly discharge and flood peaks are available since 1936 and daily discharges since 1954. Our results provide evidence for a net hydrologic change with an increase in the intensity and duration of floods in the two decades ending in 2012. The frequency of high floods is unprecedented, and small floods no longer occur. The tail of the temporal distribution of the flood peak is also changing. More frequent early floods are occurring in spring with secondary flood peaks in summer, the latest probably represents the most striking change. Furthermore, the changes have been accelerating since 2004. Finally, two islands were instrumented (2008-2012) in order to study the flooding dynamics with a better precision.

DOI: 10.1016/j.jhydrol.2017.12.034

2018032259 Parazoo, Nicholas C. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA); Koven, Charles D.; Lawrence, David M.; Romanovsky, Vladimir and Miller, Charles E. Detecting the permafrost carbon feedback; talik formation and increased cold-season respiration as precursors to sink-to-source transitions: The Cryosphere (Online), 12(1), p. 123-144, illus. incl. 2 tables, 51 ref., 2018.

Thaw and release of permafrost carbon (C) due to climate change is likely to offset increased vegetation C uptake in northern high-latitude (NHL) terrestrial ecosystems. Models project that this permafrost C feedback may act as a slow leak, in which case detection and attribution of the feedback may be difficult. The formation of talik, a subsurface layer of perennially thawed soil, can accelerate permafrost degradation and soil respiration, ultimately shifting the C balance of permafrost-affected ecosystems from long-term C sinks to long-term C sources. It is imperative to understand and characterize mechanistic links between talik, permafrost thaw, and respiration of deep soil C to detect and quantify the permafrost C feedback. Here, we use the Community Land Model (CLM) version 4.5, a permafrost and biogeochemistry model, in comparison to long-term deep borehole data along North American and Siberian transects, to investigate thaw-driven C sources in NHL (> 55°N) from 2000 to 2300. Widespread talik at depth is projected across most of the NHL permafrost region (14 million km²) by 2300, 6.2 million km² of which is projected to become a long-term C source, emitting 10 Pg C by 2100, 50 Pg C by 2200, and 120 Pg C by 2300, with few signs of slowing. Roughly half of the projected C source region is in predominantly warm sub-Arctic permafrost following talik onset. This region emits only 20 Pg C by 2300, but the CLM4.5 estimate may be biased low by not accounting for deep C in yedoma. Accelerated decomposition of deep soil C following talik onset shifts the ecosystem C balance away from surface dominant processes (photosynthesis and litter respiration), but sink-to-source transition dates are delayed by 20-200 years by high ecosystem productivity, such that talik peaks early (~ 2050s, although borehole data suggest sooner) and C source transition peaks late (~ 2150-2200). The remaining C source region in cold northern Arctic permafrost, which shifts to a net source early (late 21^st century), emits 5 times more C (95 Pg C) by 2300, and prior to talik formation due to the high decomposition rates of shallow, young C in organic-rich soils coupled with low productivity. Our results provide important clues signaling imminent talik onset and C source transition, including (1) late cold-season (January-February) soil warming at depth (~ 2 m), (2) increasing cold-season emissions (November-April), and (3) enhanced respiration of deep, old C in warm permafrost and young, shallow C in organic-rich cold permafrost soils. Our results suggest a mosaic of processes that govern carbon source-to-sink transitions at high latitudes and emphasize the urgency of monitoring soil thermal profiles, organic C age and content, cold-season CO₂ emissions, and atmospheric ¹⁴CO₂ as key indicators of the permafrost C feedback.

URL: https://www.the-cryosphere.net/12/123/2018/tc-12-123-2018.pdf

2018032260 Yi, Yonghong (University of Montana, Numerical Terradynamic Simulation Group, Missoula, MT); Kimball, John S.; Chen, Richard H.; Moghaddam, Mahta; Reichle, Rolf H.; Mishra, Umakant; Zona, Donatella and Oechel, Walter C. Characterizing permafrost active layer dynamics and sensitivity to landscape spatial heterogeneity in Alaska: The Cryosphere (Online), 12(1), p. 145-161, illus. incl. 3 tables, 62 ref., 2018.

An important feature of the Arctic is large spatial heterogeneity in active layer conditions, which is generally poorly represented by global models and can lead to large uncertainties in predicting regional ecosystem responses and climate feedbacks. In this study, we developed a spatially integrated modeling and analysis framework combining field observations, local-scale (~ 50 m resolution) active layer thickness (ALT) and soil moisture maps derived from low-frequency (L + P-band) airborne radar measurements, and global satellite environmental observations to investigate the ALT sensitivity to recent climate trends and landscape heterogeneity in Alaska. Modeled ALT results show good correspondence with in situ measurements in higher-permafrost-probability (PP >&eq; 70 %) areas (n = 33; R = 0.60; mean bias = 1.58 cm; RMSE = 20.32 cm), but with larger uncertainty in sporadic and discontinuous permafrost areas. The model results also reveal widespread ALT deepening since 2001, with smaller ALT increases in northern Alaska (mean trend = 0.32±1.18 cm yr^-1) and much larger increases (> 3 cm yr^-1) across interior and southern Alaska. The positive ALT trend coincides with regional warming and a longer snow-free season (R = 0.60 ± 0.32). A spatially integrated analysis of the radar retrievals and model sensitivity simulations demonstrated that uncertainty in the spatial and vertical distribution of soil organic carbon (SOC) was the largest factor affecting modeled ALT accuracy, while soil moisture played a secondary role. Potential improvements in characterizing SOC heterogeneity, including better spatial sampling of soil conditions and advances in remote sensing of SOC and soil moisture, will enable more accurate predictions of active layer conditions and refinement of the modeling framework across a larger domain.

URL: https://www.the-cryosphere.net/12/145/2018/tc-12-145-2018.pdf

2018031744 Rudy, Ashley C. A. (Queen's University, Department of Geography and Planning, Kingston, ON, Canada); Lamoureux, Scott F.; Kokelj, S. V.; Smith, I. R. and England, J. H. Accelerating thermokarst transforms ice-cored terrain triggering a downstream cascade to the ocean: Geophysical Research Letters, 44(21), p. 11,080-11,087, illus., 32 ref., November 16, 2017, [November 16, 2017].

Recent climate warming has activated the melt-out of relict massive ice in permafrost-preserved moraines throughout the western Canadian Arctic. This ice that has persisted since the last glaciation, buried beneath as little as 1 m of overburden, is now undergoing accelerated permafrost degradation and thermokarst. Here we document recent and intensifying thermokarst activity on eastern Banks Island that has increased the fluvial transport of sediments and solutes to the ocean. Isotopic evidence demonstrates that a major contribution to discharge is melt of relict ground ice, resulting in a significant hydrological input from thermokarst augmenting summer runoff. Accelerated thermokarst is transforming the landscape and the summer hydrological regime and altering the timing of terrestrial to marine and lacustrine transfers over significant areas of the western Canadian Arctic. The intensity of the landscape changes demonstrates that regions of cold, continuous permafrost are undergoing irreversible alteration, unprecedented since deglaciation (~13 cal kyr B.P.). Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL074912

2018031270 Mu, C. C. (Lanzhou University, Key Laboratory of Western China's Environmental Systems, Lanzhou, China); Abbott, B. W.; Wu, X. D.; Zhao, Q.; Wang, H. J.; Su, H.; Wang, S. F.; Gao, T. G.; Guo, H.; Peng, X. Q. and Zhang, T. J. Thaw depth determines dissolved organic carbon concentration and biodegradability on the northern Qinghai-Tibetan Plateau: Geophysical Research Letters, 44(18), p. 9389-9399, illus. incl. sketch map, 77 ref., September 28, 2017, [September 30, 2017].

The response of dissolved organic carbon (DOC) flux to permafrost degradation is one of the major sources of uncertainty in predicting the permafrost carbon feedback. We investigated DOC export and properties over two complete flow seasons in a catchment on the northern Qinghai-Tibetan Plateau. DOC concentration and biodegradability decreased systematically as thaw depth increased through the season, attributable to changing carbon sources and degree of microbial processing. Increasing DOC aromaticity and d¹³C-DOC indicated shifts toward more recalcitrant carbon sources and greater residence time in soils prior to reaching the stream network. These strong and consistent seasonal trends suggest that gradual active layer deepening may decrease DOC export and biodegradability from permafrost catchments. Because these patterns are opposite observations from areas experiencing abrupt permafrost collapse (thermokarst), the overall impact of permafrost degradation on DOC flux and biodegradability may depend on the proportion of the landscape experiencing gradual thaw versus thermokarst. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2017GL075067

2018033334 Anh Phuong Tran (Lawrence National Berkeley Laboratory, Division of Climate & Ecosystems, Berkeley, CA); Dafflon, Baptiste and Hubbard, Susan S. Coupled land surface-subsurface hydrogeophysical inverse modeling to estimate soil organic carbon content and explore associated hydrological and thermal dynamics in the Arctic tundra: The Cryosphere (Online), 11(5), p. 2089-2109, illus. incl. 2 tables, 39 ref., 2017.

Quantitative characterization of soil organic carbon (OC) content is essential due to its significant impacts on surface-subsurface hydrological-thermal processes and microbial decomposition of OC, which both in turn are important for predicting carbon-climate feedbacks. While such quantification is particularly important in the vulnerable organic-rich Arctic region, it is challenging to achieve due to the general limitations of conventional core sampling and analysis methods, and to the extremely dynamic nature of hydrological-thermal processes associated with annual freeze-thaw events. In this study, we develop and test an inversion scheme that can flexibly use single or multiple datasets - including soil liquid water content, temperature and electrical resistivity tomography (ERT) data - to estimate the vertical distribution of OC content. Our approach relies on the fact that OC content strongly influences soil hydrological-thermal parameters and, therefore, indirectly controls the spatiotemporal dynamics of soil liquid water content, temperature and their correlated electrical resistivity. We employ the Community Land Model to simulate nonisothermal surface-subsurface hydrological dynamics from the bedrock to the top of canopy, with consideration of land surface processes (e.g., solar radiation balance, evapotranspiration, snow accumulation and melting) and ice-liquid water phase transitions. For inversion, we combine a deterministic and an adaptive Markov chain Monte Carlo (MCMC) optimization algorithm to estimate a posteriori distributions of desired model parameters. For hydrological-thermal-to-geophysical variable transformation, the simulated subsurface temperature, liquid water content and ice content are explicitly linked to soil electrical resistivity via petrophysical and geophysical models. We validate the developed scheme using different numerical experiments and evaluate the influence of measurement errors and benefit of joint inversion on the estimation of OC and other parameters. We also quantify the propagation of uncertainty from the estimated parameters to prediction of hydrological-thermal responses. We find that, compared to inversion of single dataset (temperature, liquid water content or apparent resistivity), joint inversion of these datasets significantly reduces parameter uncertainty. We find that the joint inversion approach is able to estimate OC and sand content within the shallow active layer (top 0.3 m of soil) with high reliability. Due to the small variations of temperature and moisture within the shallow permafrost (here at about 0.6 m depth), the approach is unable to estimate OC with confidence. However, if the soil porosity is functionally related to the OC and mineral content, which is often observed in organic-rich Arctic soil, the uncertainty of OC estimate at this depth remarkably decreases. Our study documents the value of the new surface-subsurface, deterministic-stochastic inversion approach, as well as the benefit of including multiple types of data to estimate OC and associated hydrological-thermal dynamics.

URL: https://www.the-cryosphere.net/11/2089/2017/tc-11-2089-2017.pdf

2018032983 Borge, Amund F. (University of Oslo, Department of Geosciences, Oslo, Norway); Westermann, Sebastian; Solheim, Ingvild and Etzelmüller, Bernd. Strong degradation of palsas and peat plateaus in northern Norway during the last 60 years: The Cryosphere (Online), 11(1), p. 1-16, illus. incl. 4 tables, sketch map, 92 ref., 2017.

Palsas and peat plateaus are permafrost landforms occurring in subarctic mires which constitute sensitive ecosystems with strong significance for vegetation, wildlife, hydrology and carbon cycle. Firstly, we have systematically mapped the occurrence of palsas and peat plateaus in the northernmost county of Norway (Finnmark, ~ 50 000 km²) by manual interpretation of aerial images from 2005 to 2014 at a spatial resolution of 250 m. At this resolution, mires and wetlands with palsas or peat plateaus occur in about 850 km² of Finnmark, with the actual palsas and peat plateaus underlain by permafrost covering a surface area of approximately 110 km². Secondly, we have quantified the lateral changes of the extent of palsas and peat plateaus for four study areas located along a NW-SE transect through Finnmark by utilizing repeat aerial imagery from the 1950s to the 2010s. The results of the lateral changes reveal a total decrease of 33-71 % in the areal extent of palsas and peat plateaus during the study period, with the largest lateral change rates observed in the last decade. However, the results indicate that degradation of palsas and peat plateaus in northern Norway has been a consistent process during the second half of the 20th century and possibly even earlier. Significant rates of areal change are observed in all investigated time periods since the 1950s, and thermokarst landforms observed on aerial images from the 1950s suggest that lateral degradation was already an ongoing process at this time. The results of this study show that lateral erosion of palsas and peat plateaus is an important pathway for permafrost degradation in the sporadic permafrost zone in northern Scandinavia. While the environmental factors governing the rate of erosion are not yet fully understood, we note a moderate increase in air temperature, precipitation and snow depth during the last few decades in the region.

URL: http://www.the-cryosphere.net/11/1/2017/tc-11-1-2017.pdf

2018033338 Charkin, Alexander N. (Russian Academy of Sciences, Far Eastern Branch, Pacific Oceanological Institute, Vladivostok, Russian Federation); van der Loeff, Michiel Rutgers; Shakhova, Natalia E.; Gustafsson, Orjan; Dudarev, Oleg V.; Cherepnev, Maxim S.; Salyuk, Anatoly N.; Koshurnikov, Andrey V.; Spivak, Eduard A.; Gunar, Alexey Y.; Ruban, Alexey S. and Semiletov, Igor P. Discovery and characterization of submarine groundwater discharge in the Siberian Arctic seas; a case study in the Buor-Khaya Gulf, Laptev Sea: The Cryosphere (Online), 11(5), p. 2305-2327, illus. incl. 2 tables, 98 ref., 2017.

It has been suggested that increasing terrestrial water discharge to the Arctic Ocean may partly occur as submarine groundwater discharge (SGD), yet there are no direct observations of this phenomenon in the Arctic shelf seas. This study tests the hypothesis that SGD does exist in the Siberian Arctic Shelf seas, but its dynamics may be largely controlled by complicated geocryological conditions such as permafrost. The field-observational approach in the southeastern Laptev Sea used a combination of hydrological (temperature, salinity), geological (bottom sediment drilling, geoelectric surveys), and geochemical (²²⁴Ra, ²²³Ra, ²²⁸Ra, and ²²⁶Ra) techniques. Active SGD was documented in the vicinity of the Lena River delta with two different operational modes. In the first system, groundwater discharges through tectonogenic permafrost talik zones was registered in both winter and summer. The second SGD mechanism was cryogenic squeezing out of brine and water-soluble salts detected on the periphery of ice hummocks in the winter. The proposed mechanisms of groundwater transport and discharge in the Arctic land-shelf system is elaborated. Through salinity vs. ²²⁴Ra and ²²⁴Ra/²²³Ra diagrams, the three main SGD-influenced water masses were identified and their end-member composition was constrained. Based on simple mass-balance box models, discharge rates at sites in the submarine permafrost talik zone were 1. 7 ´ 10⁶ m³ d^-1 or 19.9 m³ s^-1, which is much higher than the April discharge of the Yana River. Further studies should apply these techniques on a broader scale with the objective of elucidating the relative importance of the SGD transport vector relative to surface freshwater discharge for both water balance and aquatic components such as dissolved organic carbon, carbon dioxide, methane, and nutrients.

URL: https://www.the-cryosphere.net/11/2305/2017/tc-11-2305-2017.pdf

2018031204 Davesne, Gautier (Université de Montréal, Cold Regions Geomorphology and Geotechnical Laboratory, Montreal, QC, Canada); Fortier, Daniel; Domine, Florent and Gray, James T. Wind-driven snow conditions control the occurrence of contemporary marginal mountain permafrost in the Chic-Choc Mountains, south-eastern Canada; a case study from Mont Jacques-Cartier: The Cryosphere (Online), 11(3), p. 1351-1370, illus. incl. strat. cols., 5 tables, sketch maps, 79 ref., 2017.

We present data on the distribution and thermophysical properties of snow collected sporadically over 4 decades along with recent data of ground surface temperature from Mont Jacques-Cartier (1268 m a.s.l.), the highest summit in the Appalachians of south-eastern Canada. We demonstrate that the occurrence of contemporary permafrost is necessarily associated with a very thin and wind-packed winter snow cover which brings local azonal topo-climatic conditions on the dome-shaped summit. The aims of this study were (i) to understand the snow distribution pattern and snow thermophysical properties on the Mont Jacques-Cartier summit and (ii) to investigate the impact of snow on the spatial distribution of the ground surface temperature (GST) using temperature sensors deployed over the summit. Results showed that above the local treeline, the summit is characterized by a snow cover typically less than 30 cm thick which is explained by the strong westerly winds interacting with the local surface roughness created by the physiography and surficial geomorphology of the site. The snowpack structure is fairly similar to that observed on windy Arctic tundra with a top dense wind slab (300 to 450 kg m^-3) of high thermal conductivity, which facilitates heat transfer between the ground surface and the atmosphere. The mean annual ground surface temperature (MAGST) below this thin and wind-packed snow cover was about -1 °C in 2013 and 2014, for the higher, exposed, blockfield-covered sector of the summit characterized by a sporadic herbaceous cover. In contrast, for the gentle slopes covered with stunted spruce (krummholz), and for the steep leeward slope to the south-east of the summit, the MAGST was around 3 °C in 2013 and 2014. The study concludes that the permafrost on Mont Jacques-Cartier, most widely in the Chic-Choc Mountains and by extension in the southern highest summits of the Appalachians, is therefore likely limited to the barren wind-exposed surface of the summit where the low air temperature, the thin snowpack and the wind action bring local cold surface conditions favourable to permafrost development.

URL: http://www.the-cryosphere.net/11/1351/2017/tc-11-1351-2017.pdf

2018031199 Gilbert, Graham L. (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Norway); Cable, Stefanie; Thiel, Christine; Christiansen, Hanne H. and Elberling, Bo. Cryostratigraphy, sedimentology, and the late Quaternary evolution of the Zackenberg River delta, northeast Greenland: The Cryosphere (Online), 11(3), p. 1265-1282, illus. incl. strat. cols., 2 tables, sketch maps, 63 ref., 2017.

The Zackenberg River delta is located in northeast Greenland (74°30' N, 20°30' E) at the outlet of the Zackenberg fjord valley. The fjord-valley fill consists of a series of terraced deltaic deposits (ca. 2 km²) formed during relative sea-level (RSL) fall. We investigated the deposits using sedimentological and cryostratigraphic techniques together with optically stimulated luminescence (OSL) dating. We identify four facies associations in sections (4 to 22 m in height) exposed along the modern Zackenberg River and coast. Facies associations relate to (I) overriding glaciers, (II) retreating glaciers and quiescent glaciomarine conditions, (III) delta progradation in a fjord valley, and (IV) fluvial activity and niveo-aeolian processes. Pore, layered, and suspended cryofacies are identified in two 20 m deep ice-bonded sediment cores. The cryofacies distribution, together with low overall ground-ice content, indicates that permafrost is predominately epigenetic in these deposits. Fourteen OSL ages constrain the deposition of the cored deposits to between approximately 13 and 11 ka, immediately following deglaciation. The timing of permafrost aggradation was closely related to delta progradation and began following the subaerial exposure of the delta plain (ca. 11 ka). Our results reveal information concerning the interplay between deglaciation, RSL change, sedimentation, permafrost aggradation, and the timing of these events. These findings have implications for the timing and mode of permafrost aggradation in other fjord valleys in northeast Greenland.

URL: http://www.the-cryosphere.net/11/1265/2017/tc-11-1265-2017.pdf

2018033671 Göckede, Mathias (Max Planck Institute for Biogeochemistry, Jena, Germany); Kittler, Fanny; Kwon, Min Jung; Burjack, Ina; Heimann, Martin; Kolle, Olaf; Zimov, Nikita and Zimov, Sergey. Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure: The Cryosphere (Online), 11(6), p. 2975-2996, illus. incl. 3 tables, sketch map, 97 ref., 2017. Includes appendices.

Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the northern high-latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in northeast Siberia comprising a drained and a control site. At the drainage site, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net effects of drainage. Reduced thermal conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere as sensible heat in the drained area, which may trigger a warming of the lower atmospheric surface layer.

URL: https://www.the-cryosphere.net/11/2975/2017/tc-11-2975-2017.pdf

2018032985 Gruber, Stephan (Carleton University, Ottawa, ON, Canada); Fleiner, Renate; Guegan, Emilie; Panday, Prajjwal; Schmid, Marc-Olivier; Stumm, Dorothea; Wester, Philippus; Zhang Yinsheng and Zhao Lin. Review article; inferring permafrost and permafrost thaw in the mountains of the Hindu Kush Himalaya region: The Cryosphere (Online), 11(1), p. 81-99, illus. incl. 1 table, 179 ref., 2017.

The cryosphere reacts sensitively to climate change, as evidenced by the widespread retreat of mountain glaciers. Subsurface ice contained in permafrost is similarly affected by climate change, causing persistent impacts on natural and human systems. In contrast to glaciers, permafrost is not observable spatially and therefore its presence and possible changes are frequently overlooked. Correspondingly, little is known about permafrost in the mountains of the Hindu Kush Himalaya (HKH) region, despite permafrost area exceeding that of glaciers in nearly all countries. Based on evidence and insight gained mostly in other permafrost areas globally, this review provides a synopsis on what is known or can be inferred about permafrost in the mountains of the HKH region. Given the extreme nature of the environment concerned, it is to be expected that the diversity of conditions and phenomena encountered in permafrost exceed what has previously been described and investigated. We further argue that climate change in concert with increasing development will bring about diverse permafrost-related impacts on vegetation, water quality, geohazards, and livelihoods. To better anticipate and mitigate these effects, a deepened understanding of high-elevation permafrost in subtropical latitudes as well as the pathways interconnecting environmental changes and human livelihoods are needed.

URL: http://www.the-cryosphere.net/11/81/2017/tc-11-81-2017.pdf

2018031205 Holloway, Jean E. (Queen's University, Department of Geography and Planning, Kingston, ON, Canada); Rudy, Ashley C. A.; Lamoureux, Scott F. and Treitz, Paul M. Determining the terrain characteristics related to the surface expression of subsurface water pressurization in permafrost landscapes using susceptibility modelling: The Cryosphere (Online), 11(3), p. 1403-1415, illus. incl. 4 tables, 63 ref., 2017.

Warming of the Arctic in recent years has led to changes in the active layer and uppermost permafrost. In particular, thick active layer formation results in more frequent thaw of the ice-rich transient layer. This addition of moisture, as well as infiltration from late season precipitation, results in high pore-water pressures (PWPs) at the base of the active layer and can potentially result in landscape degradation. To predict areas that have the potential for subsurface pressurization, we use susceptibility maps generated using a generalized additive model (GAM). As model response variables, we used active layer detachments (ALDs) and mud ejections (MEs), both formed by high PWP conditions at the Cape Bounty Arctic Watershed Observatory, Melville Island, Canada. As explanatory variables, we used the terrain characteristics elevation, slope, distance to water, topographic position index (TPI), potential incoming solar radiation (PISR), distance to water, normalized difference vegetation index (NDVI; ME model only), geology, and topographic wetness index (TWI). ALDs and MEs were accurately modelled in terms of susceptibility to disturbance across the study area. The susceptibility models demonstrate that ALDs are most probable on hill slopes with gradual to steep slopes and relatively low PISR, whereas MEs are associated with higher elevation areas, lower slope angles, and areas relatively far from water. Based on these results, this method identifies areas that may be sensitive to high PWPs and helps improve our understanding of geomorphic sensitivity to permafrost degradation.

URL: http://www.the-cryosphere.net/11/1403/2017/tc-11-1403-2017.pdf

2018033669 Kass, M. Andy (U. S. Geological Survey, Crustal Geophysics and Geochemistry Science Center, Denver, CO); Irons, Trevor P.; Minsley, Burke J.; Pastick, Neal J.; Brown, Dana R. N. and Wylie, Bruce K. In situ nuclear magnetic resonance response of permafrost and active layer soil in boreal and tundra ecosystems: The Cryosphere (Online), 11(6), p. 2943-2955, illus. incl. 1 table, sketch map, 48 ref., 2017.

Characterization of permafrost, particularly warm and near-surface permafrost which can contain significant liquid water, is critical to understanding complex interrelationships with climate change, ecosystems, and disturbances such as wildfires. Understanding the vulnerability and resilience of permafrost requires an interdisciplinary approach, relying on (for example) geophysical investigations, ecological characterization, direct observations, remote sensing, and more. As part of a multiyear investigation into the impacts of wildfires on permafrost, we have collected in situ measurements of the nuclear magnetic resonance (NMR) response of the active layer and permafrost in a variety of soil conditions, types, and saturations. In this paper, we summarize the NMR data and present quantitative relationships between active layer and permafrost liquid water content and pore sizes and show the efficacy of borehole NMR (bNMR) to permafrost studies. Through statistical analyses and synthetic freezing simulations, we also demonstrate that borehole NMR is sensitive to the nucleation of ice within soil pore spaces.

URL: https://www.the-cryosphere.net/11/2943/2017/tc-11-2943-2017.pdf

2018031203 Leifer, Ira (Bubbleology Research International, Solvang, CA); Chernykh, Denis; Shakhova, Natalia and Semiletov, Igor. Sonar gas flux estimation by bubble insonification; application to methane bubble flux from seep areas in the outer Laptev Sea: The Cryosphere (Online), 11(3), p. 1333-1350, illus. incl. 2 tables, 67 ref., 2017.

Sonar surveys provide an effective mechanism for mapping seabed methane flux emissions, with Arctic submerged permafrost seepage having great potential to significantly affect climate. We created in situ engineered bubble plumes from 40 m depth with fluxes spanning 0.019 to 1.1 L s^-1 to derive the in situ calibration curve (Q(s)). These nonlinear curves related flux (Q) to sonar return (s) for a multibeam echosounder (MBES) and a single-beam echosounder (SBES) for a range of depths. The analysis demonstrated significant multiple bubble acoustic scattering - precluding the use of a theoretical approach to derive Q(s) from the product of the bubble s(r) and the bubble size distribution where r is bubble radius. The bubble plume s occurrence probability distribution function (Y(s)) with respect to Q found Y(s) for weak s well described by a power law that likely correlated with small-bubble dispersion and was strongly depth dependent. Y(s) for strong s was largely depth independent, consistent with bubble plume behavior where large bubbles in a plume remain in a focused core. Y(s) was bimodal for all but the weakest plumes. Q(s) was applied to sonar observations of natural arctic Laptev Sea seepage after accounting for volumetric change with numerical bubble plume simulations. Simulations addressed different depths and gases between calibration and seep plumes. Total mass fluxes (Q_m) were 5.56, 42.73, and 4.88 mmol s^-1 for MBES data with good to reasonable agreement (4-37 %) between the SBES and MBES systems. The seepage flux occurrence probability distribution function (Y(Q)) was bimodal, with weak Y(Q) in each seep area well described by a power law, suggesting primarily minor bubble plumes. The seepage-mapped spatial patterns suggested subsurface geologic control attributing methane fluxes to the current state of subsea permafrost.

URL: http://www.the-cryosphere.net/11/1333/2017/tc-11-1333-2017.pdf

2018031779 Magnin, Florence (Université Savoie Mont Blanc, Laboratory of Environment Dynamics and Territories of the Mountain, France); Josnin, Jean-Yves; Ravanel, Ludovic; Pergaud, Julien; Pohl, Benjamin and Deline, Philip. Modelling rock wall permafrost degradation in the Mont Blanc massif from the LIA to the end of the 21^st century: The Cryosphere (Online), 11(4), p. 1813-1834, illus., 106 ref., 2017.

High alpine rock wall permafrost is extremely sensitive to climate change. Its degradation has a strong impact on landscape evolution and can trigger rockfalls constituting an increasing threat to socio-economical activities of highly frequented areas; quantitative understanding of permafrost evolution is crucial for such communities. This study investigates the long-term evolution of permafrost in three vertical cross sections of rock wall sites between 3160 and 4300 m above sea level in the Mont Blanc massif, from the Little Ice Age (LIA) steady-state conditions to 2100. Simulations are forced with air temperature time series, including two contrasted air temperature scenarios for the 21st century representing possible lower and upper boundaries of future climate change according to the most recent models and climate change scenarios. The 2-D finite element model accounts for heat conduction and latent heat transfers, and the outputs for the current period (2010-2015) are evaluated against borehole temperature measurements and an electrical resistivity transect: permafrost conditions are remarkably well represented. Over the past two decades, permafrost has disappeared on faces with a southerly aspect up to 3300 m a.s.l. and possibly higher. Warm permafrost (i.e. > -2 °C) has extended up to 3300 and 3850 m a.s.l. in N and S-exposed faces respectively. During the 21st century, warm permafrost is likely to extend at least up to 4300 m a.s.l. on S-exposed rock walls and up to 3850 m a.s.l. depth on the N-exposed faces. In the most pessimistic case, permafrost will disappear on the S-exposed rock walls at a depth of up to 4300 m a.s.l., whereas warm permafrost will extend at a depth of the N faces up to 3850 m a.s.l., but possibly disappearing at such elevation under the influence of a close S face. The results are site specific and extrapolation to other sites is limited by the imbrication of local topographical and transient effects.

URL: https://www.the-cryosphere.net/11/1813/2017/tc-11-1813-2017.pdf

2018033670 Mewes, Benjamin (Ruhr-University Bochum, Institute of Hydrology, Water Resources Management and Environmental Engineering, Bochum, Germany); Hilbich, Christin; Delaloye, Reynald and Hauck, Christian. Resolution capacity of geophysical monitoring regarding permafrost degradation induced by hydrological processes: The Cryosphere (Online), 11(6), p. 2957-2974, illus. incl. 2 tables, 65 ref., 2017.

Geophysical methods are often used to characterize and monitor the subsurface composition of permafrost. The resolution capacity of standard methods, i.e. electrical resistivity tomography and refraction seismic tomography, depends not only on static parameters such as measurement geometry, but also on the temporal variability in the contrast of the geophysical target variables (electrical resistivity and P-wave velocity). Our study analyses the resolution capacity of electrical resistivity tomography and refraction seismic tomography for typical processes in the context of permafrost degradation using synthetic and field data sets of mountain permafrost terrain. In addition, we tested the resolution capacity of a petrophysically based quantitative combination of both methods, the so-called 4-phase model, and through this analysed the expected changes in water and ice content upon permafrost thaw. The results from the synthetic data experiments suggest a higher sensitivity regarding an increase in water content compared to a decrease in ice content. A potentially larger uncertainty originates from the individual geophysical methods than from the combined evaluation with the 4-phase model. In the latter, a loss of ground ice can be detected quite reliably, whereas artefacts occur in the case of increased horizontal or vertical water flow. Analysis of field data from a well-investigated rock glacier in the Swiss Alps successfully visualized the seasonal ice loss in summer and the complex spatially variable ice, water and air content changes in an interannual comparison.

URL: https://www.the-cryosphere.net/11/2957/2017/tc-11-2957-2017.pdf

2018033005 Schuh, Carina (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Frampton, Andrew and Christiansen, Hanne Hvidtfeldt. Soil moisture redistribution and its effect on inter-annual active layer temperature and thickness variations in a dry loess terrace in Adventdalen, Svalbard: The Cryosphere (Online), 11(1), p. 635-651, illus. incl. 7 tables, 80 ref., 2017.

High-resolution field data for the period 2000-2014 consisting of active layer and permafrost temperature, active layer soil moisture, and thaw depth progression from the UNISCALM research site in Adventdalen, Svalbard, is combined with a physically based coupled cryotic and hydrogeological model to investigate active layer dynamics. The site is a loess-covered river terrace characterized by dry conditions with little to no summer infiltration and an unsaturated active layer. A range of soil moisture characteristic curves consistent with loess sediments is considered and their effects on ice and moisture redistribution, heat flux, energy storage through latent heat transfer, and active layer thickness is investigated and quantified based on hydro-climatic site conditions. Results show that soil moisture retention characteristics exhibit notable control on ice distribution and circulation within the active layer through cryosuction and are subject to seasonal variability and site-specific surface temperature variations. The retention characteristics also impact unfrozen water and ice content in the permafrost. Although these effects lead to differences in thaw progression rates, the resulting inter-annual variability in active layer thickness is not large. Field data analysis reveals that variations in summer degree days do not notably affect the active layer thaw depths; instead, a cumulative winter degree day index is found to more significantly control inter-annual active layer thickness variation at this site. A tendency of increasing winter temperatures is found to cause a general warming of the subsurface down to 10 m depth (0.05 to 0.26 °C yr^-1, observed and modelled) including an increasing active layer thickness (0.8 cm yr^-1, observed and 0.3 to 0.8 cm yr^-1, modelled) during the 14-year study period.

URL: http://www.the-cryosphere.net/11/635/2017/tc-11-635-2017.pdf

2018031777 Vieira, Goncalo (Universidade de Lisboa, Centre for Geographical Studies, Lisbon, Portugal); Mora, Carla and Faleh, Ali. New observations indicate the possible presence of permafrost in North Africa (Djebel Toubkal, High Atlas, Morocco): The Cryosphere (Online), 11(4), p. 1691-1705, illus. incl. 2 tables, 66 ref., 2017.

Relict and present-day periglacial features have been reported in the literature for the upper reaches of the High Atlas mountains, which is the highest range in North Africa (Djebel Toubkal - 4167 m a.s.l.). A lobate feature in the Irhzer Ikhibi south at 3800 m a.s.l. has been previously interpreted as an active rock glacier, but no measurements of ground or air temperatures are known to exist for the area. In order to assess the possible presence of permafrost, we analyse data from June 2015 to June 2016 from two air temperature measurement sites at 2370 and 3210 m a.s.l. and from four ground surface temperature (GST) sites at 3220, 3815, 3980 and 4160 m a.s.l. to characterize conditions along an altitudinal gradient along the Oued Ihghyghaye valley to the summit of the Djebel Toubkal. GSTs were collected at 1 h intervals, and the presence of snow cover at the monitoring sites was validated using Landsat 8 and Sentinel-2 imagery. Two field visits allowed for logger installation and collection and for assessing the geomorphological features in the area. The results show that snow plays a major role on the thermal regime of the shallow ground, inducing important spatial variability. The lowest site at 3220 m had a thermal regime characterized by frequent freeze-thaw cycles during the cold season but with few days of snow. When snow settled, the ground surface remained isothermal at 0 °C , indicating the absence of permafrost. The highest sites at 3980 and 4160 m a.s.l. showed very frequent freeze-thaw cycles and a small influence of the snow cover on GST, reflecting the lack of snow accumulation due to the wind-exposed settings on a ridge and on the summit plateau. The site located at 3815 m in the Irhzer Ikhibi south valley had a cold, stable thermal regime with GST varying from -4.5 to -6 °C from December to March, under a continuous snow cover. The site's location in a concave setting favours wind-driven snow accumulation and lower incoming solar radiation due to the shading effect of a ridge, inducing the conservation of a thick snow pack. The stable and low GSTs are interpreted as a strong indicator of the probable presence of permafrost at this site, which is an interpretation supported by the presence of lobate and arcuate features in the talus deposits. We present first results and further observations using geophysics, and borehole measurements are foreseen. This is the first time that probable permafrost has been reported from temperature observations in the mountains of North Africa.

URL: https://www.the-cryosphere.net/11/1691/2017/tc-11-1691-2017.pdf

2018031781 Vonk, Jorien E. (Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands); Tesi, Tommaso; Broder, Lisa; Holmstrand, Henry; Hugelius, Gustaf; Andersson, August; Dudarev, Oleg; Semiletov, Igor and Gustafsson, Orjan. Distinguishing between old and modern permafrost sources in the northeast Siberian land-shelf system with compound-specific d²H analysis: The Cryosphere (Online), 11(4), p. 1879-1895, illus. incl. 6 tables, 82 ref., 2017.

Pleistocene ice complex permafrost deposits contain roughly a quarter of the organic carbon (OC) stored in permafrost (PF) terrain. When permafrost thaws, its OC is remobilized into the (aquatic) environment where it is available for degradation, transport or burial. Aquatic or coastal environments contain sedimentary reservoirs that can serve as archives of past climatic change. As permafrost thaw is increasing throughout the Arctic, these reservoirs are important locations to assess the fate of remobilized permafrost OC. We here present compound-specific deuterium (d²H) analysis on leaf waxes as a tool to distinguish between OC released from thawing Pleistocene permafrost (ice complex deposits; ICD) and from thawing Holocene permafrost (from near-surface soils). Bulk geochemistry (%OC; d¹³C; %total nitrogen, TN) was analyzed as well as the concentrations and d²H signatures of long-chain n-alkanes (C₂₁ to C₃₃) and mid- to long-chain n-alkanoic acids (C₁₆ to C₃₀) extracted from both ICD-PF samples (n = 9) and modern vegetation and O-horizon (topsoil-PF) samples (n = 9) from across the northeast Siberian Arctic. Results show that these topsoil-PF samples have higher %OC, higher OC/TN values and more depleted d¹³C-OC values than ICD-PF samples, suggesting that these former samples trace a fresher soil and/or vegetation source. Whereas the two investigated sources differ on the bulk geochemical level, they are, however, virtually indistinguishable when using leaf wax concentrations and ratios. However, on the molecular isotope level, leaf wax biomarker d²H values are statistically different between topsoil PF and ICD PF. For example, the mean d²H value of C₂₉ n-alkane was -246 ± 13 ppm (mean ± SD) for topsoil PF and -280 ± 12 ppm for ICD PF. With a dynamic isotopic range (difference between two sources) of 34 to 50 ppm; the isotopic fingerprints of individual, abundant, biomarker molecules from leaf waxes can thus serve as endmembers to distinguish between these two sources. We tested this molecular d²H tracer along with another source-distinguishing approach, dual-carbon (d¹³C-D¹⁴C) isotope composition of bulk OC, for a surface sediment transect in the Laptev Sea. Results show that general offshore patterns along the shelf-slope transect are similar, but the source apportionment between the approaches vary, which may highlight the advantages of either. This study indicates that the application of d²H leaf wax values has potential to serve as a complementary quantitative measure of the source and differential fate of OC thawed out from different permafrost compartments.

URL: https://www.the-cryosphere.net/11/1879/2017/tc-11-1879-2017.pdf

2018031206 Westermann, Sebastian (University of Oslo, Department of Geosciences, Oslo, Norway); Peter, Maria; Langer, Moritz; Schwamborn, Georg; Schirrmeister, Lutz; Etzelmüller, Bernd and Boike, Julia. Transient modeling of the ground thermal conditions using satellite data in the Lena River delta, Siberia: The Cryosphere (Online), 11(3), p. 1441-1463, illus. incl. 3 tables, 93 ref., 2017.

Permafrost is a sensitive element of the cryosphere, but operational monitoring of the ground thermal conditions on large spatial scales is still lacking. Here, we demonstrate a remote-sensing-based scheme that is capable of estimating the transient evolution of ground temperatures and active layer thickness by means of the ground thermal model CryoGrid 2. The scheme is applied to an area of approximately 16 000 km² in the Lena River delta (LRD) in NE Siberia for a period of 14 years. The forcing data sets at 1 km spatial and weekly temporal resolution are synthesized from satellite products and fields of meteorological variables from the ERA-Interim reanalysis. To assign spatially distributed ground thermal properties, a stratigraphic classification based on geomorphological observations and mapping is constructed, which accounts for the large-scale patterns of sediment types, ground ice and surface properties in the Lena River delta. A comparison of the model forcing to in situ measurements on Samoylov Island in the southern part of the study area yields an acceptable agreement for the purpose of ground thermal modeling, for surface temperature, snow depth, and timing of the onset and termination of the winter snow cover. The model results are compared to observations of ground temperatures and thaw depths at nine sites in the Lena River delta, suggesting that thaw depths are in most cases reproduced to within 0.1 m or less and multi-year averages of ground temperatures within 1-2 °C. Comparison of monthly average temperatures at depths of 2-3 m in five boreholes yielded an RMSE of 1.1 °C and a bias of -0.9 °C for the model results. The highest ground temperatures are calculated for grid cells close to the main river channels in the south as well as areas with sandy sediments and low organic and ice contents in the central delta, where also the largest thaw depths occur. On the other hand, the lowest temperatures are modeled for the eastern part, which is an area with low surface temperatures and snow depths. The lowest thaw depths are modeled for Yedoma permafrost featuring very high ground ice and soil organic contents in the southern parts of the delta. The comparison to in situ observations indicates that transient ground temperature modeling forced by remote-sensing data is generally capable of estimating the thermal state of permafrost (TSP) and its time evolution in the Lena River delta. The approach could hence be a first step towards remote detection of ground thermal conditions and active layer thickness in permafrost areas.

URL: https://www.the-cryosphere.net/11/1441/2017/tc-11-1441-2017.pdf

2018031201 Wicky, Jonas (University of Fribourg, Department of Geosciences, Fribourg, Switzerland) and Hauck, Christian. Numerical modelling of convective heat transport by air flow in permafrost talus slopes: The Cryosphere (Online), 11(3), p. 1311-1325, illus. incl. 2 tables, 67 ref., 2017.

Talus slopes are a widespread geomorphic feature in the Alps. Due to their high porosity a gravity-driven internal air circulation can be established which is forced by the gradient between external (air) and internal (talus) temperature. The thermal regime is different from the surrounding environment, leading to the occurrence of permafrost below the typical permafrost zone. This phenomenon has mainly been analysed by field studies and only few explicit numerical modelling studies exist. Numerical simulations of permafrost sometimes use parameterisations for the effects of convection but mostly neglect the influence of convective heat transfer in air on the thermal regime. In contrast, in civil engineering many studies have been carried out to investigate the thermal behaviour of blocky layers and to improve their passive cooling effect. The present study further develops and applies these concepts to model heat transfer in air flows in a natural-scale talus slope. Modelling results show that convective heat transfer has the potential to develop a significant temperature difference between the lower and the upper parts of the talus slope. A seasonally alternating chimney-effect type of circulation develops. Modelling results also show that this convective heat transfer leads to the formation of a cold reservoir in the lower part of the talus slope, which can be crucial for maintaining the frozen ground conditions despite increasing air temperatures caused by climate change.

URL: http://www.the-cryosphere.net/11/1311/2017/tc-11-1311-2017.pdf

2018033000 Widhalm, Barbara (Zentralanstalt für Meteorologie und Geodynamik, Division of Data, Methods and Modelling, Vienna, Austria); Bartsch, Annett; Leibman, Marina and Khomutov, Artem. Active-layer thickness estimation from X-band SAR backscatter intensity: The Cryosphere (Online), 11(1), p. 483-496, illus. incl. 2 tables, sketch map, 58 ref., 2017.

The active layer above the permafrost, which seasonally thaws during summer, is an important parameter for monitoring the state of permafrost. Its thickness is typically measured locally, but a range of methods which utilize information from satellite data exist. Mostly, the normalized difference vegetation index (NDVI) obtained from optical satellite data is used as a proxy. The applicability has been demonstrated mostly for shallow depths of active-layer thickness (ALT) below approximately 70 cm. Some permafrost areas including central Yamal are, however, characterized by larger ALT. Surface properties including vegetation structure are also represented by microwave backscatter intensity. So far, the potential of such data for estimating ALT has not been explored. We therefore investigated the relationship between ALT and X-band synthetic aperture radar (SAR) backscatter of TerraSAR-X (averages for 10 ´ 10 m window) in order to examine the possibility of delineating ALT with continuous and larger spatial coverage in this area and compare it to the already-established method of using NDVI from Landsat (30 m). Our results show that the mutual dependency of ALT and TerraSAR-X backscatter on land cover types suggests a connection of both parameters. A range of 5 dB can be observed for an ALT range of 100 cm (40-140 cm), and an R² of 0.66 has been determined over the calibration sites. An increase of ALT with increasing backscatter can be determined. The root mean square error (RMSE) over a comparably heterogeneous validation site with maximum ALT of > 150 cm is 20 cm. Deviations are larger for measurement locations with mixed vegetation types (especially partial coverage by cryptogam crust) with respect to the spatial resolution of the satellite data.

URL: http://www.the-cryosphere.net/11/483/2017/tc-11-483-2017.pdf

2018031789 Zou Defu (Chinese Academy of Sciences, Cryosphere Research Station on Qinghai-Xizang Plateau, Lanzhou, China); Zhao Lin; Sheng Yu; Chen Ji; Hu Guojie; Wu Tonghua; Wu Jichun; Xie Changwei; Wu Xiaodong; Pang Qiangqiang; Wang Wu; Du Erji; Li Wangping; Liu Guangyue; Li Jing; Qin Yanhui; Qiao Yongping; Wang Zhiwei; Shi Jianzong and Cheng Guodong. A new map of permafrost distribution on the Tibetan Plateau: The Cryosphere (Online), 11(6), p. 2527-2542, illus. incl. 5 tables, 83 ref., 2017.

The Tibetan Plateau (TP) has the largest areas of permafrost terrain in the mid- and low-latitude regions of the world. Some permafrost distribution maps have been compiled but, due to limited data sources, ambiguous criteria, inadequate validation, and deficiency of high-quality spatial data sets, there is high uncertainty in the mapping of the permafrost distribution on the TP. We generated a new permafrost map based on freezing and thawing indices from modified Moderate Resolution Imaging Spectroradiometer (MODIS) land surface temperatures (LSTs) and validated this map using various ground-based data sets. The soil thermal properties of five soil types across the TP were estimated according to an empirical equation and soil properties (moisture content and bulk density). The temperature at the top of permafrost (TTOP) model was applied to simulate the permafrost distribution. Permafrost, seasonally frozen ground, and unfrozen ground covered areas of 1.06 ´ 10⁶ km² (0.97-1.15 ´ 10⁶ km², 90 % confidence interval) (40 %), 1.46 ´ 10⁶ (56 %), and 0.03 ´ 10⁶ km² (1 %), respectively, excluding glaciers and lakes. Ground-based observations of the permafrost distribution across the five investigated regions (IRs, located in the transition zones of the permafrost and seasonally frozen ground) and three highway transects (across the entire permafrost regions from north to south) were used to validate the model. Validation results showed that the kappa coefficient varied from 0.38 to 0.78 with a mean of 0.57 for the five IRs and 0.62 to 0.74 with a mean of 0.68 within the three transects. Compared with earlier studies, the TTOP modelling results show greater accuracy. The results provide more detailed information on the permafrost distribution and basic data for use in future research on the Tibetan Plateau permafrost.

URL: https://www.the-cryosphere.net/11/2527/2017/tc-11-2527-2017.pdf

2018031056 Govaerts, Joan (Centre d'Étude de l'Énergie Nucléaire, Belgium); Beerten, Koen and ten Veen, Johan. Weichselian permafrost depth in the Netherlands; a comprehensive uncertainty and sensitivity analysis: The Cryosphere (Online), 10(6), p. 2907-2922, illus. incl. 2 tables, 52 ref., 2016.

The Rupelian clay in the Netherlands is currently the subject of a feasibility study with respect to the storage of radioactive waste in the Netherlands (OPERA-project). Many features need to be considered in the assessment of the long-term evolution of the natural environment surrounding a geological waste disposal facility. One of these is permafrost development as it may have an impact on various components of the disposal system, including the natural environment (hydrogeology), the natural barrier (clay) and the engineered barrier. Determining how deep permafrost might develop in the future is desirable in order to properly address the possible impact on the various components. It is expected that periglacial conditions will reappear at some point during the next several hundred thousands of years, a typical time frame considered in geological waste disposal feasibility studies. In this study, the Weichselian glaciation is used as an analogue for future permafrost development. Permafrost depth modelling using a best estimate temperature curve of the Weichselian indicates that permafrost would reach depths between 155 and 195 m. Without imposing a climatic gradient over the country, deepest permafrost is expected in the south due to the lower geothermal heat flux and higher average sand content of the post-Rupelian overburden. Accounting for various sources of uncertainty, such as type and impact of vegetation, snow cover, surface temperature gradients across the country, possible errors in palaeoclimate reconstructions, porosity, lithology and geothermal heat flux, stochastic calculations point out that permafrost depth during the coldest stages of a glacial cycle such as the Weichselian, for any location in the Netherlands, would be 130-210 m at the 2s level. In any case, permafrost would not reach depths greater than 270 m. The most sensitive parameters in permafrost development are the mean annual air temperatures and porosity, while the geothermal heat flux is the crucial parameter in permafrost degradation once temperatures start rising again.

URL: http://www.the-cryosphere.net/10/2907/2016/tc-10-2907-2016.pdf

2018031051 Jones, Benjamin M. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Baughman, Carson A.; Romanovsky, Vladimir E.; Parsekian, Andrew D.; Babcock, Esther L.; Stephani, Eva; Jones, Miriam C.; Grosse, Guido and Berg, Edward E. Presence of rapidly degrading permafrost plateaus in south-central Alaska: The Cryosphere (Online), 10(6), p. 2673-2692, illus. incl. sects., strat. cols., 4 tables, sketch maps, 87 ref., 2016.

Permafrost presence is determined by a complex interaction of climatic, topographic, and ecological conditions operating over long time scales. In particular, vegetation and organic layer characteristics may act to protect permafrost in regions with a mean annual air temperature (MAAT) above 0 °C. In this study, we document the presence of residual permafrost plateaus in the western Kenai Peninsula lowlands of south-central Alaska, a region with a MAAT of 1.5 ± 1 °C (1981-2010). Continuous ground temperature measurements between 16 September 2012 and 15 September 2015, using calibrated thermistor strings, documented the presence of warm permafrost (-0.04 to -0.08 °C). Field measurements (probing) on several plateau features during the fall of 2015 showed that the depth to the permafrost table averaged 1.48 m but at some locations was as shallow as 0.53 m. Late winter surveys (augering, coring, and GPR) in 2016 showed that the average seasonally frozen ground thickness was 0.45 m, overlying a talik above the permafrost table. Measured permafrost thickness ranged from 0.33 to > 6.90 m. Manual interpretation of historic aerial photography acquired in 1950 indicates that residual permafrost plateaus covered 920 ha as mapped across portions of four wetland complexes encompassing 4810 ha. However, between 1950 and ca. 2010, permafrost plateau extent decreased by 60.0 %, with lateral feature degradation accounting for 85.0 % of the reduction in area. Permafrost loss on the Kenai Peninsula is likely associated with a warming climate, wildfires that remove the protective forest and organic layer cover, groundwater flow at depth, and lateral heat transfer from wetland surface waters in the summer. Better understanding the resilience and vulnerability of ecosystem-protected permafrost is critical for mapping and predicting future permafrost extent and degradation across all permafrost regions that are currently warming. Further work should focus on reconstructing permafrost history in south-central Alaska as well as additional contemporary observations of these ecosystem-protected permafrost sites south of the regions with relatively stable permafrost.

URL: http://www.the-cryosphere.net/10/2673/2016/tc-10-2673-2016.pdf

2018031052 Marmy, Antoine (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Rajczak, Jan; Delaloye, Reynald; Hilbich, Christin; Hoelzle, Martin; Kotlarski, Sven; Lambiel, Christophe; Noetzli, Jeannette; Phillips, Marcia; Salzmann, Nadine; Staub, Benno and Hauck, Christian. Semi-automated calibration method for modelling of mountain permafrost evolution in Switzerland: The Cryosphere (Online), 10(6), p. 2693-2719, illus. incl. 4 tables, 113 ref., 2016. Includes appendices.

Permafrost is a widespread phenomenon in mountainous regions of the world such as the European Alps. Many important topics such as the future evolution of permafrost related to climate change and the detection of permafrost related to potential natural hazards sites are of major concern to our society. Numerical permafrost models are the only tools which allow for the projection of the future evolution of permafrost. Due to the complexity of the processes involved and the heterogeneity of Alpine terrain, models must be carefully calibrated, and results should be compared with observations at the site (borehole) scale. However, for large-scale applications, a site-specific model calibration for a multitude of grid points would be very time-consuming. To tackle this issue, this study presents a semi-automated calibration method using the Generalized Likelihood Uncertainty Estimation (GLUE) as implemented in a 1-D soil model (CoupModel) and applies it to six permafrost sites in the Swiss Alps. We show that this semi-automated calibration method is able to accurately reproduce the main thermal condition characteristics with some limitations at sites with unique conditions such as 3-D air or water circulation, which have to be calibrated manually. The calibration obtained was used for global and regional climate model (GCM/RCM)-based long-term climate projections under the A1B climate scenario (EU-ENSEMBLES project) specifically downscaled at each borehole site. The projection shows general permafrost degradation with thawing at 10 m, even partially reaching 20 m depth by the end of the century, but with different timing among the sites and with partly considerable uncertainties due to the spread of the applied climatic forcing.

URL: http://www.the-cryosphere.net/10/2693/2016/tc-10-2693-2016.pdf

2018031055 Müller, Johann (University of Zurich, Department of Geography, Zurich, Switzerland); Vieli, Andreas and Gärtner-Roer, Isabelle. Rock glaciers on the run; understanding rock glacier landform evolution and recent changes from numerical flow modeling: The Cryosphere (Online), 10(6), p. 2865-2886, illus. incl. 6 tables, 83 ref., 2016.

Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment-ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment-ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.

URL: http://www.the-cryosphere.net/10/2865/2016/tc-10-2865-2016.pdf

2018033044 Isayev, V. I. (Tomsk Technical University, Institute of Natural Resources, Tomsk, Russian Federation). Otsenka vliyaniya tolshch vechnoy merzloty pozdnechetvertichnogo klimaticheskogo pokholodaniya na geotermicheskiy rezhim neftematerinskikh otlozheniy Zapadnoy Sibiri [Influence of upper Quaternary permafrost on thermal regime of petroleum source rocks in West Siberia]: Neftegazovaya Geologiya. Teoriya i Praktika = Petroleum Geology - Theoretical and Applied Studies, 10(2), 24 p. (English sum.), illus. incl. 7 tables, sketch map, 37 ref., 2015.

The probable paleoclimatic factors influencing the formation of the geothermal regime of oil source deposits are determined: 1) secular variation of temperature on the surface of the Earth; 2) the formation and degradation of neopleistocene strata of permafrost rocks; 3) Late Quaternary ice caps. The purpose of research is quantitative assessment of the impact of frost on the geothermal regime and the implementation of the generation potential of Bazhenov sediments in the southeast of Western Siberia (latitude of Tomsk region). The author's method of research based on the method of paleotemperature modeling is applied - solving the inverse and direct issues of geothermy under a sedimentation conditions. It was established that the account of permafrost with thickness of about 300 m is required for adequate recovery of the thermal history of oil source deposits on south-eastern areas of Western Siberia. This will enable to properly take into account the history of the main phase of oil generation and not to underestimate (up to 25%) the hydrocarbon resources.

DOI: 10.17353/2070-5379/21_2015

2018033191 Popescu, Razvan (University of Bucharest, Faculty of Geography, Bucharest, Romania); Vespremeanu-Stroe, Alfred; Cruceru, Nicolae and Pop, Olimpiu. Permafrost response to the post Little Ice Age climate variability in the Romanian Carpathians [abstr.]: in Special issue; late Pleistocene and Holocene climatic variability in the Carpathian-Balkan region; abstracts volume (Mindrescu, Marcel, editor; et al.), Georeview, 24(2), p. 144, 2014.

The geomorphological evidences along with the range of methods recently (since 2008) applied in the Romanian Carpathians indicate that most of the rock glaciers are relict or inactive in the present. Only a few cases of active or complex rock glaciers (active only across their upper parts) are supposed to exist in the highest granitic massifs of Southern Carpathians (Retezat and Parang), but contemporary inactivation trends seem to take place as indicated by growth of vegetation (especially Pinus mugo) on their fronts. On the other hand, most of the inactive rock glaciers present distinct signs of activity in the recent past that followed the Little Ice Age colder period which in the Romanian Carpathians had its last maximum between 1820 and 1840 (Popa and Kern, 2008).

URL: http://georeview.ro/ojs/index.php/revista/article/view/237

2018033206 Zamosteanu, Andrei (Stefan cel Mare University of Suceava, Department of Geography, Suceava, Romania); Cristea, Ionut Alexandru and Mindrescu, Marcel. Electrical resistivity tomography (ERT) surveys on glacial deposits in Romanian Carpathians [abstr.]: in Special issue; late Pleistocene and Holocene climatic variability in the Carpathian-Balkan region; abstracts volume (Mindrescu, Marcel, editor; et al.), Georeview, 24(2), p. 186-189, sect., geol. sketch map, 7 ref., 2014.

The study presents preliminary results regarding the use of electrical resistivity surveys in the assessment of the internal structure of the glacial deposits from the Romanian Carpathians. ERT is a geophysical method used to quantify changes in electrical resistivity of the ground towards passing electric current across an array of electrodes and simultaneous measurement of the induced potential gradient. Using specific software the measurements are further processed and correlated with the topography in order to obtain bedrock resistivity features. Therefore, the method is useful to evaluate the characteristics of geological strata and is widely used for mapping shallow subsurface geological structures. In the mountain regions ERT studies have been applied in different glacial and periglacial geomorphological studies - for permafrost detection (in Romanian Carpathians - Urdea et. al., 2008; Vespremeanu-Stroe et al., 2012), slope deformation analysis, the assessment of slip surface depths, sediment thickness, groundwater levels etc. One of the most commonly 2-D array used is the Wenner electrode configuration, which is moderately sensitive to both horizontal and vertical ground structures. Due to their elevations and Pleistocene's climatic conditions, the Romanian Carpathians have been partially affected by Quaternary glaciations. The glaciers descended to about 1050-1200 m a.s.l. (Urdea and Reurther, 2009) in the Transylvanian Alps and Rodna Mountains (Eastern Carpathians) carving a large number of U-shaped valleys and glacial cirques (Mindrescu, 2006) and forming accumulations of unconsolidated glacial debris (moraines). Our study areas are two sites located in the northern (Rodna Mts.) and southern (Iezer Papusa Mts.) part of the mountain range.

URL: http://georeview.ro/ojs/index.php/revista/article/view/188

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2018031507 Braud, Isabelle (Irstea, UR HHLY, Villeurbanne, France); Gaillardet, Jérôme; Hankard, Fatim; Le Borgne, Tanguy; Nord, Guillaume; Six, Delphine; Galy, Catherine; Laggoun-Défarge, Fatima; Tallec, Tiphaine and Pauwels, Hélène. OZCAR; the French network of Critical Zone Observatories; principles and scientific objectives [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5410, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

This contribution aims at presenting the principles that underlined the creation of the OZCAR research infrastructure, gathering various Critical Zone Observatories in France, and the scientific questions that drives the observation settings. The Critical Zone includes the fine zone between the lower atmosphere at the top of the canopy down to the bedrock-soil interface. This lithosphere-atmosphere boundary is critical for the availability of life-sustaining resources and critical for humanity because this is the zone where we live, where we build our cities, from which we extract our food and our water and where we release most of our wastes. This is the fragile zone on which the natural ecosystem relies because this is where nutrients are being released from the rocks. OZCAR is a distributed research infrastructure gathering instrumented sites and catchments on continental surfaces all dedicated to the observation and monitoring of the different compartments of the Critical Zone at the national scale. All these observatories (more that 40) were all built up on specific questions (acid deposition, flood prediction, urban hydrology...), some of them more than 50 years ago, but they have all in common to be highly instrumented, permanently funded as infrastructures. They all share the same overarching goal of understanding and predicting the Critical Zone in a changing world. OZCAR gathers instrumented catchments, hydrogeological sites, peatlands, glacier and permafrost regions and a spatial observatory under the common umbrella of understanding water and biogeochemical cycles and the associated fluxes of energy by using natural gradients and experimentation. Based on the collaboration with Southern Countries, OZCAR's sites have a global coverage including tropical areas and high mountainous regions in the Andes and the Himalaya. OZCAR benefits from a French investments project called CRITEX (Innovative equipment for the critical zone, URL: https://www.critex.fr/critex-3/observatories/) that is centered on the development and deployment of innovative instrumentation in the sites. OZCAR was launched in 2016 under the leadership of the French Ministry in charge of Higher Education and Research, assembling all French Research Institutions involved in environmental studies and with the ambition of facilitating interdisciplinary research in terrestrial surfaces, stimulating instrumental development and being visible at the international level. The paper will presents the main common scientific questions, challenges in terms of instrumentation and experimentation deployment, in particular in terms of co-location of sites, data base and modeling activities that the OZCAR network plan to address in the next years. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5410.pdf

2018031364 Chlachula, Jiri (Tomas Bata University, Department of Environmental Security, Laboratory for Paleoecology, Zlin, Czech Republic). The last glacial ecosystems of North Siberia; permafrost-sealed evidence from fossiliferous cryolithic formations [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5065, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Institute of Geoecology and Geoinformation, Adam Mickiewicz University, Poznan, Poland Multi-proxy palaeoecology and geoarchaeology records released from degrading permafrost in the Yana River basin and the tributary valleys (66-67°N) confirm the past existence of natural conditions for sustainment of the Pleistocene megafauna as well as the last glacial peopling of this sub-polar area. Well-preserved and taxonomically diverse large fossil fauna skeletal remains sealed in the Pleistocene colluvial and alluvial-plain formations in intact geological positions 10-20 m above the present river and scattered on gravelly river banks after their erosion from the primary geo-contexts attest to a high biotic potential of the Late Pleistocene (MIS 3-2) sub-Arctic forest-tundra. Pollen records from the ancient interstratified boggy sediments and megafauna coprolites (14C-dated to 41-38 ka BP) show a predominance of the Siberian larch, dwarf birch and willow in the local vegetation cover accompanied by grassy communities during the mid-Last Glacial stage not dissimilar from the present northern taiga forest. Articulated and humanly used/worked fauna bones (mammoth, rhinoceros, horse, bison and reindeer among other species) point to co-existence of the large animals with the upper Paleolithic people within the mosaic open riverine ecosystems of the late Last Ice Age. The time-trangressive macro-lithic stone industry produced from pre-selected river gravel cobbles document some specific ways of human environmental adjustment to past periglacial settings. Geomorphology and hydrogeology indices of field mappings in congruence with the long-term statistical meteorology data illustrate a steadily increasing annual temperature trend in the broader Yana-Adycha Basins (current MAT -14.5°C) that triggers accelerated permafrost thaw across the Verkhoyansk region of NE Siberia, particularly the lowlands, similarly as in the Indigirka and Kolyma Basins further east. The regional flu-vial discharge is most dynamic during late spring due to the cumulative effects of snow-melting and solar radiation exposing buried paleo-surfaces. This process has a fundamental bearing for an increased visibility and frequency of the encountered occurrences of fossil fauna as well as the early cultural records released from the permafrost grounds precipitating a more systematic Quaternary geology-palaeoecology research. The Paleolithic finds from the Bytantay River valley are the first ones documenting the local pre-Holocene prehistoric occupation. The new data add to present knowledge on the initial colonization process of the sub-Arctic and Arctic regions of Siberia. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5065.pdf

2018035133 Etzelmuller, Bernd (University of Oslo, Norway, Oslo, Norway); Isaksen, Ketil; Westermann, Sebastian; Hauck, Christian and Hilbich, Christin. Accelerating warming and degradation of permafrost in northern Norway [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6060, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Permafrost is sensitive to climate change, modulating geomorphological process rates and ultimately landscape development. In Norway, since the 1980ies many studies have been carried out to evaluate the permafrost distribution, its changing state and its relation especially to climate and snow conditions. This knowledge has flown into numerical models, calculating ground temperatures in space and time. At present Norway has an unique data set obtained from bore holes where we measure temperatures along both altitudinal and latitudinal gradients. In addition at all sites geophysical surveys are available using refraction seismic and electrical resistivity tomography, partly multi-temporal. Finally, daily gridded data sets of meteorological parameters such as air temperature, precipitation and associated snow cover are available back to 1957, allowing the evaluation of climate-ground thermal regime relations along regional gradients. This presentation summarises a c. 10 year record of ground thermal measurements and geophysical surveys from three main sites in northern Norway, along with new evaluations of changes in palsa distribution and size. For the first time we demonstrate the development of talliks in mountain permafrost in northern Norway, and relate and discuss the development of these talliks to changing atmospheric and snow conditions. The observations are also related to long-term change detection observations of palsa mires in the vicinity of the bore holes, highlighting accelerating thaw and degradation of permafrost during the last two decades. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-6060.pdf

2018035138 Etzelmuller, Bernd (University of Oslo, Oslo, Norway); Myhra, Kristin S.; Westermann, Sebastian and Magning, Florence. Cryo-conditioniong of geomorphological processes in steep slopes in time and space [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6071, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The role of the ground thermal regime on geomorphological processes in settings associated to steep slopes has received considerable attention in the past. It is evident from recent studies that e.g. rock walls have a profound effect on the thermal regime in mountain sides, a.o. influencing rock wall stability, weathering regimes and glacier-permafrost interaction in space and time. This presentation discusses the importance of the thermal regime in space and time on geomorphological processes in steep slopes. We combine direct observations of air, ground and rock wall temperatures with numerical simulations using a 2D transient thermal model (CryoGRID 2D). We analyze how thermal gradients in rock walls or coastal cliffs may influence important geomorphological processes related to weathering, talus developments, material accumulation and ice aggregation in coarse material. On longer time scales,permafrost dynamics associated with glaciation and deglaciaton phases, may have influenced the development and stability of large-scale valley systems. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-6071.pdf

2018031492 Fischer, Andrea (Austrian Academy of Sciences, Institute for Interdisciplinary Mountain Research, Innsbruck, Austria); Helfricht, Kay; Seiser, Bernd; Stocker-Waldhuber, Martin; Hartl, Lea and Wiesenegger, Hans. The challenge of monitoring the cryosphere in alpine environments; prepare the present for the future [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5363, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Understanding the interaction of mountain glaciers and permafrost with weather and climate is essential for the interpretation of past states of the cryosphere in terms of climate change. Most of the glaciers and rock glaciers in Eastern Alpine terrain are subject to strong gradients in climatic forcing, and the persistence of these gradients under past climatic conditions is, more or less, unknown. Thus a key challenge of monitoring the cryosphere is to define the demands on a monitoring strategy for capturing essential processes and their potential changes. For example, the effects of orographic precipitation and local shading vary with general circulation patterns and the amount of solar radiation during the melt(ing) season. Recent investigations based on the Austrian glacier inventories have shown that glacier distribution is closely linked to topography and climatic situation, and that these two parameters imply also different sensitivities of the specific glaciers to progressing climate change. This leads to the need to develop a monitoring system capturing past, but also fairly unknown future ensembles of climatic state and sensitivities. As a first step, the Austrian glacier monitoring network has been analyzed from the beginning of the records onwards. Today's monitoring network bears the imprints of past research interests, but also past funding policies and personal/institutional engagements. As a limitation for long term monitoring in general, today's monitoring strategies have to cope with being restricted to these historical commitments to preserve the length of the time series, but at the same time expanding the measurements to fulfill present and future scientific and societal demands. The decision on cryospheric benchmark sites has an additional uncertainty: the ongoing disintegration of glaciers, their increasing debris cover as well as the potential low ice content and relatively unknown reaction of rock glaciers in the course of climate change, limits the number of potential candidates for future monitoring drastically. In the light of these developments, sample sizes are a critical question for reliable monitoring, together with strategies for coping with changing monitoring sites and composition of time series. As a first step, the Austrian monitoring network has been analyzed from 1891 onwards. Past changes evident from the glacier inventories capturing all glaciers have been compared to the subsamples of glaciers monitored for length change, mass balance and ice flow velocities. The results show that for capturing the full bandwidth of regional changes, glacier inventories are necessary. Without the analysis of larger scale changes, the interpretation of records with very low sample sizes, such as mass balance or length change, has a high uncertainty level. For specific research or monitoring purposes, for example, the development of runoff master sites with all types of monitoring techniques improve the certainty of the spatial extrapolations of local records or the interpretation of volume changes. The challenge of preparing the present network for the future requires a thorough analysis of potential future developments to be able to switch sites with a common observation period necessary to investigate the different sensitivities. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5363.pdf

2018031351 Frieling, Joost (Utrecht University, Department of Earth Sciences, Utrecht, Netherlands); Peterse, Francien; Lunt, Daniel; Bohaty, Steven; Damste, Jaap Sinninghe; Reichart, Gert-Jan and Sluijs, Appy. Carbon sources during the Paleocene-Eocene thermal maximum [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4032, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The Paleocene-Eocene Thermal Maximum (PETM; ~56 Ma) was a period of rapid 4-5°C global warming and a global negative carbon isotope excursion (CIE) of 3-4.5h signaling the input of at least 1500 Gt of d¹³C-depleted carbon into the ocean-atmosphere system. Carbon cycle modeling has indicated that the shape and magnitude of this CIE are generally explained by a large and rapid initial pulse, followed by ~50 kyr of d¹³C-depleted carbon injection. Crucially, some of suggested carbon sources, e.g. submarine methane hydrates and permafrost thawing, may respond to warming and act as positive carbon cycle feedbacks on millennial timescales. Previous analyses showed that warming started prior to the CIE at some high and mid-latitude sites, but is still unknown whether this is a global signal and timing and magnitude of such a warming remain poorly constrained. We generated a new high-resolution TEX86 and d¹³C record from Ocean Drilling Program Site 959 in the eastern tropical Atlantic and find that initial warming preceded the PETM CIE by 10 kyr. Moreover, cross-correlation functions on these new and published temperature-d¹³C data imply that substantial (2-3 C) warming lead d¹³C-depleted carbon injection by an average of 2-3 kyr globally. Finally, a data compilation shows that global burial fluxes of non-detrital Ba approximately tripled across all depths of the ocean studied, which on PETM time scales can only be explained by significant Ba addition to the oceans. Submarine hydrates are Ba-rich and require warming to dissociate. The simplest explanation for the temperature lead and Ba addition to the ocean is that methane hydrates dissociated as a response to initial warming and acted as a positive carbon cycle feedback during the PETM. The attribution of the CIE to a carbon cycle feedback naturally leads to the question what caused the early warming. The absence of a d¹³C change during the early warming implies a d¹³C-neutral CO₂ source, such as volcanism, is the most likely explanation. Recent findings directly connected hydrothermal vent activity in the Voring and More Basins to the PETM CIE, explaining its' exceptionally long duration (Frieling et al., 2016 PNAS) and Storey et al. (2007 Science) already showed based on absolute dating that the most active phase of North Atlantic Igneous Province (NAIP) roughly coincides with the PETM. We speculate the NAIP played a central role in Paleocene-Eocene climate change and, in addition to the thermogenic methane, also supplied the CO₂ that drove the initial warming, which lead to massive methane hydrate dissociation during the PETM. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4032.pdf

2018031469 Hilger, Paula (Geological Survey of Norway, Trondheim, Norway); Hermanns, Reginald L.; Myhra, Kristin S.; Gosse, John C.; Ivy-Ochs, Susan and Etzelmüller, Bernd. Rock-slope failure activity and geological crises in western Norway [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5300, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

In Norway a compilation of terrestrial cosmogenic nuclide (TCN) ages of rock-avalanche deposits suggests a close link of rock-slope failures related to deglaciation. Although ages spread over several thousand years at the end of the late Pleistocene, 50% of all documented events occurred within 1000 years after deglaciation. It is therefore likely that debuttressing triggered most of the events. The same data set suggests that 25% of the events occurred during a period stretching until the Holocene thermal maximum (HTM). These events might be interpreted as possible reactions to additional factors such as the thawing of high-altitude permafrost. An example of a geological crisis following deglaciation and before the HTM are seven lobate rock-avalanche deposits mapped under the slope of the Vora Mountain (1450 m asl.) in the Nordfjord area of western Norway. Three events of this rock-slope failure cluster date within a short time period of 2000 years, where modeling studies indicate that high-altitude permafrost was present. After the HTM rock-slope failures are distributed temporally and spatially rather evenly throughout the Holocene and western Norway. But there are two independent local clusters with frequent rock slides during a short time span. (1) At the active Mannen rock-slope instability several rock-avalanche and rockslide deposits were mapped on the valley bottom. Stratigraphic relations combined with TCN dating suggest that at least one event occurred when the valley bottom was below the marine limit. TCN ages of further four lobes cluster around 5.2 ka BP, which does not coincide with any other rock-avalanche occurrence in the region. The top of the north facing 1295 m high unstable slope concurs with the currently estimated permafrost boundary. Preliminary TCN ages of the sliding surface indicate that larger parts of the mountain did not become active until the climate maximum. It is likely that due to structural complexity not allowing for any easy kinematic failure process, it required several thousand years of rock-slope deformation prior to the multiple failures. (2) The youngest independent rock-avalanche cluster is historic with 5 rock avalanches sourcing from Ramnefjellet in 1905, 1936 (three events), and 1950 entering into Loen Lake in western Norway. Subsequent displacement waves killed 61 people in 1905 and 73 people due to the first failure in 1936. The back scarp does not exceed 850 m elevation and lies hence below the present day and Little Ice Age permafrost limit. It is therefore unlikely that permafrost dynamics contribute to this sequence of rock-slope failures. Local clusters or a geological crisis by rock-slope failures seems to be related to different main factors, such as glacial debutressing, influence of ground thermal regime changes (Mannen) and probably more disconnected to major climate variability (Loen). For an integrated risk management it is therefore important to understand that large rock-slope failures do not necessarily have to occur in single events but can occur over several decades or centuries and thus complicate severely land use management after catastrophic events. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5300.pdf

2018031550 Magnin, Florence (University of Oslo, Oslo, Norway); Etzelmüller, Bernd; Hilger, Paula; Westermann, Sebastian; Isaksen, Ketil and Hermanns, Reginald L. Measuring and mapping rock wall permafrost across Norway [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5489, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The investigation of rock wall permafrost is of high relevance for geohazards assessment and for understanding cold-climate landscape evolution since its changes over time can cause slope instability and trigger rock falls. The destabilization of steep slopes is a serious threat to human activities and lives in Norway, especially because most of rock walls lie directly above houses, infrastructures and large water bodies with potential of high-energy displacement waves. Rock wall permafrost has been investigated since the early 2010s in alpine massifs of western Norway thanks to the CryoLINK project (2008-2011). The CryoWALL project (2015-2019) aims at extending this preliminary study to the nation-wide scale. It consists in systematic measurements of rock surface temperature (RST) in order model and to map the spatial distribution of rock wall permafrost. In between August 2015 and August 2016, 20 RST loggers (Geoprecision mini data loggers, accuracy 0.1 C, precision 0.01 C, sensors PT1000) were installed at 10 cm depth of 7 selected sites. These loggers are distributed along a latitudinal transect (from 60°50'N to 69°46'N), cover various elevations and sun-exposures, and are completed by 4 other loggers installed in Jotunheimen in 2009 and 2010. The RST time series are used for (a) characterizing the distribution of rock wall permafrost across Norway, (b) running steady-state and transient numerical models of rock wall permafrost at selected sites, and to (c) calibrate a general linear regression model that will be used to (d) predict the spatial distribution of rock wall permafrost at the national scale. In this communication we will introduce the RST measurement installations and sites, as well as the first RST records that encompass 6 years of continuous measurements in Jotunheimen, and 1 year of record for 13 other loggers. The preliminary analysis shows that RST differs by 3 C between N and S faces in Southern Norway, with mean annual RST as low as -1.9°C at 1700 m a.s.l in a N face (Nordfjord, Sogn of Fjordane) during the measurement year which was about 0.8°C above normal (1981-2010). In Northern Norway, the RST difference between N and S faces is rather around 1.5°C due to the midnight sun and polar night effects, inducing similar RST in both aspects during December, January, May and June. Negative mean annual RST is found as low as 1200 m a.s.l in S-exposed faces (Kafjorden, Troms) during the measurement year which was 1.1 C above normal in this area. The ice and snow coating the rock faces during winter appears as a significant warming factor that can raise the mean annual RST up to at least 1 C compared to bare rock conditions. This first data set is shown to be of high relevance for predictive modeling. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5489.pdf

2018035124 Prantl, Hannah (University of Innsbruck, Institute of Geography, Innsbruck, Austria); Sailer, Rudolf; Stötter, Johann and Nagler, Thomas. Regional permafrost distribution based on remote sensing data [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6037-2, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The detection of permafrost phenomena and its distribution in mountain environments as well as the monitoring of changes of permafrost with respect to climatic changes is important for alpine risk, infrastructure, natural hazards and climate change studies. It is assumed that in Iceland less than ten percent of the land surface is underlain by permafrost and that most of it may disappear under global warming in the 21st century. In particular regions these changes will cause sincere problems for the society in mountainous regions. But because of the complexity of permafrost detection, the knowledge about its distribution in Iceland is currently not very well evaluated and only based on small-scale observations. As permafrost is at most not directly observable, different indicators, e.g. rock glaciers and perennial snow patches, can be mapped to identify the distribution of permafrost. The study site is situated on the Trollaskagi peninsula, in Northern Iceland. The peninsula is situated between Skagafjorgur and Eyjafjorgur and the highest summits reach an altitude of about 1400. For large-scale identification of perennial snow patches (PSP) over the Trollaskagi peninsula remote sensing techniques are a practicable technique. In our study, we use optical satellite (Landsat-5/7/8 and Sentinel-2B) data in combination with aerial images to map and monitor the spatial distribution of perennial snow patches, indicating a low or negative ground temperature underneath. After an atmospheric correction of the satellite data, pan sharpening of the Landsat data and resampling the Sentinel-2B data, and Normalized Difference Snow Index (NDSI) calculations, the perennial snow patches are classified in i) mainly permafrost, ii) mainly wind and iii) mainly avalanche induced origin. For that purpose, topographic information such as slope angle, aspect and curvature are determined from a DEM of Trollaskagi peninsula. In a first step a digital elevation model with a grid size of 25 m is used, which will be replaced after the release of the ArcticDEM offering a grid size of 5 m. Furthermore, the wind atlas from the Icelandic Met Office (IMO) is used to identify the main wind direction. The analysis of the satellite data in combination with topographic as well as wind atlas information will result in a PSP distribution map of the Trollaskagi peninsula. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-6037.pdf

2018033240 Pugh, Thomas (University of Birmingham, School of Geography, Earth and Environmental Sciences, Birmingham, United Kingdom); Jones, Chris; Burton, Chantelle; Huntingford, Chris; Arneth, Almut; Lomas, Mark; Piao Shilong and Sitch, Stephen. The committed long-term sink of carbon due to vegetation changes may rival carbon losses due to permafrost thawing [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7717, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The terrestrial biosphere provides an important sink of atmospheric carbon, the size and persistence of which is one of the largest uncertainties in future climate projections. However, the response of the biosphere to changes in its environment substantially lags the rate of environmental change in many aspects. Transient assessments of changes in ecosystem properties therefore do not capture the full magnitude of the response to which ecosystems are committed. Here an ensemble of Dynamic Global Vegetation Model and Earth System Model simulations is used to assess the magnitude of committed changes in tree cover and carbon storage, to attribute the drivers of uncertainty in these values, and to assess the likely magnitude and direction of committed changes in biospheric carbon stocks post 2100. The results show consistently large committed changes post-2100 in slow components of ecosystems, notably carbon stores and vegetation cover fractions, despite relatively small changes in productivity. In boreal locations, increases in vegetation and soil carbon storage may be large enough to offset committed carbon losses from thawing permafrost. As much of this committed sink results from increased biomass as a result of changes in vegetation composition, the results indicate a pressing need for vegetation dynamics, as well as the now widely-considered anthropogenic land cover change, to be more routinely represented in the coupled Earth System Models used to make future climate projections. However, the timescales over which committed changes in vegetation cover and biomass occur are highly uncertain, and represent a key limitation in assessing whether the simulated committed sink will be realised on human-relevant timescales. A move away from evaluating DGVMs in terms of their stable vegetation state, towards addressing their ability to capture transient responses, is advocated. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7717.pdf

2018033258 Rasmussen, Laura Helene (University of Copenhagen, Department of Geosciences and Natural Resource Management, Center for Permafrost (CENPERM), Copenhagen, Denmark); Zhang, Wenxin; Hollesen, Jorgen; Cable, Stefanie; Christiansen, Hanne Hvidtfeldt; Jansson, Per-Erik and Elberling, Bo. Modelling high Arctic deep permafrost temperature sensitivity in Northeast Greenland based on experimental and field observations [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7773, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Permafrost affected areas in Greenland are expected to experience a marked temperature increase within decades. Most studies have considered near-surface permafrost sensitivity, whereas permafrost temperatures below the depths of zero annual amplitude is less studied despite being closely related to changes in near-surface conditions, such as changes in active layer thermal properties, soil moisture and snow depth. In this study, we measured the sensitivity of thermal conductivity (TC) to gravimetric water content (GWC) in frozen and thawed permafrost sediments from fine-sandy and gravelly deltaic and fine-sandy alluvial deposits in the Zackenberg valley, NE Greenland. We further calibrated a coupled heat and water transfer model, the "CoupModel", for one central delta sediment site with average snow depth and further forced it with meteorology from a nearby delta sediment site with a topographic snow accumulation. With the calibrated model, we simulated deep permafrost thermal dynamics in four 20-year scenarios with changes in surface temperature and active layer (AL) soil moisture: a) 3 C warming and AL water table at 0.5 m depth; b) 3 C warming and AL water table at 0.1 m depth; c) 6 C warming and AL water table at 0.5 m depth and d) 6 C warming and AL water table at 0.1 m depth. Our results indicate that frozen sediments have higher TC than thawed sediments. All sediments show a positive linear relation between TC and soil moisture when frozen, and a logarithmic one when thawed. Gravelly delta sediments were highly sensitive, but never reached above 12% GWC, indicating a field effect of water retention capacity. Alluvial sediments are less sensitive to soil moisture than deltaic (fine and coarse) sediments, indicating the importance of unfrozen water in frozen sediment. The deltaic site with snow accumulation had 1 C higher mean annual ground temperature than the average snow depth site. Permafrost temperature at the depth of 18 m increased with 1.5 C and 3.5 C in the scenarios with 3 C and 6 C warming, respectively. Increasing the soil moisture had no important additional effect to warming, although an increase in thermal offset was indicated. We conclude that below-ground sediment properties affect the sensitivity of TC to GWC, that surface temperature changes can influence the deep permafrost within a short time scale, and that differences in snow depth affect surface temperatures. Sediment type and the type of precipitation should thus be considered when estimating future High Arctic deep permafrost sensitivity. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7773.pdf

2018031455 Scapozza, Cristian (University of Applied Sciences and Arts of Southern Switzerland, Canobbio, Switzerland). Alpine relict rock glaciers and periglacial talus slopes; the witnesses of paraperiglacial crisis? [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5265, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The "paraglacial" and "paraperiglacial" concepts were introduced in the second half of 20th Century for describe processes, landforms and deposits directly conditioned by deglaciation (paraglacial), respectively by permafrost degradation (paraperiglacial). They represents theoretical models describing the transition from glacial to periglacial, or more generally non glacial conditions (paraglacial model), and from periglacial to temperate conditions (paraperiglacial model). Evidences of sediment transfer conditioned by these processes were described in particular in the Arctic and Subarctic domains. These evidences are less generalized in the Alps and they consider rarely both concepts, integrating periglacial landforms and deposits in source to sink sediment transfer in a single catchment. Here we present evidences of para(peri)glacial sedimentary crises by quantifying sediment transfer under cold climates for the upper Ticino River catchment (southern Swiss Alps). Compilation and revision of chronological data and the assessment of rockwall erosion rates in the periglacial zone, allowed empirical models of sediment transfer to be produced (Scapozza 2016). These models highlights significant rates of rockwall erosion during periods of intense temperature warming and intense permafrost degradation (such as at the beginning of Bolling and during the Preboreal), showing a very good correspondence with paraglacial and paraperiglacial theoretical models. Sediment transfer evolution during the entire Lateglacial and the first half of Holocene in the southern Swiss Alps may then be explained by a combination of a paraglacial erosion phase related to the deglaciation and of two paraperiglacial erosion phases related with significant periods of temperature warming during the Bolling/Allerod and the first part of the Holocene. The first phase of paraperiglacial erosion taking place during the Bolling/Allerod was driven by significant permafrost degradation in rockwalls conducing to the formation of actually relict rock glaciers, which are larger than intact ones. During the second phase of paraperiglacial erosion, occurred at the beginning of the Holocene and driving an enhanced erosion phase in the periglacial zone (with erosion rates higher than 2.0 meters per millennium) until the end of the mid-Holocene climate optimum, were formed the main part of periglacial talus slopes and were released deposits that will constitute intact rock glaciers in the followings millennia. For the second part of the Holocene, otherwise, the increase in sedimentation rates in the valley floor is probably explained by the general glacial advance characterizing the six cold phases registered in Central Europe since 6.2 cal. ka BP. For the periglacial zone, this period was at the opposite characterized by low rockwall erosion rates related to limited permafrost degradation at least until the end of the Little Ice Age. REFERENCE Scapozza C. (2016). Evidence of paraglacial and paraperiglacial crisis in Alpine sediment transfer since the Last Glaciation (Ticino, Switzerland). Quaternaire 27(2): 139-155. DOI: 10.4000/quaternaire.7805 [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5265.pdf

2018033282 Strzelecki, Matt (University of Wroclaw, Institute of Geography and Regional Development, Wroclaw, Poland); Lim, Michael; Kasprzak, Marek; Swirad, Zuzanna; Rachlewicz, Grzegorz; Pawlowski, Lukasz; Jaskolski, Marek and Migon, Piotr. Impact of periglacial and paraglacial processes on rocky coast geomorphology in Arctic and Antarctic [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7814, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

In contrast to mid and low latitude coasts, relatively little is known regarding the potential impacts of climate and sea-level change on polar coastal margins. Indeed, many of the existing intellectual paradigms regarding the functioning of polar coasts are now out-dated, based on descriptive geomorphology and a limited process-based understanding. Our work aims to address this deficiency in understanding by quantifying the processes controlling the evolution and behaviour of rock coasts in polar climates, based on representative examples from South Shetland Islands (Antarctic) and Svalbard (Arctic). The pristine coasts of South Shetland Islands and Svalbard provide a superb opportunity to quantify how polar rock coasts are responding to sea-level changes and intensification of periglacial and paraglacial processes associated with climate warming. The selected coastline forms part of the South Shetland and Svalbard strandflat, which is characterized by diverse range of coastal landforms. The rock cliffs and shore platforms in selected study sites are formed in volcanic rocks (Antarctic) and divers mixture of sedimentary and crystalline formations (Svalbard). In our project we utilise a rigorous, coherent and novel suite of techniques to analyse the spatially and temporally diverse range of processes and responses controlling the polar rock coast environments: - Schmidt Hammer and Equotip tests of rock surface resistance; - micro-erosion meter measurements of rock surface downwearing rates; - observations of seasonal changes in the state of permafrost developed in solid rocks using electrical resistivity tomography (ERT); - monitoring of thermal state of the rocky cliffs and platforms using network of thermistors; - photogrammetric analysis of digital images of scanned cliffs and platforms and GIS processing of obtained data. In this paper we present the results of field campaigns of the project carried out in years 2014-2016 in Admiralty Bay (South Shetland) and Hornsund and Billefjorden (Svalbard) that focused on: - rock resistance surveys using Schmidt Hammer Rock Tests (SHRT) and Equotip (EQ) across the modern and uplifted shore platforms formed in various volcanic rocks; - measurements of shore platform downwearing rates using the Traverse Micro-Erosion Meter (TMEM) stations; - mapping rock coast permafrost distribution using geophysical techniques (ERT). This lithological variability provided an excellent opportunity to examine the influence of rock resistance on the development of various coastal landforms in periglacial climate. SHRT, EQ and TMEM surveys along several morphologically different coast types demonstrated broad variety of interrelations between rock surface resistance and distance from present-day shoreline as well as thickness of sediment and snow covers. In general, rock cliff surfaces were the most resistant in their lower and middle zones which are thermally insulated by thick winter snowdrifts. Whereas the more exposed cliff tops were heavily fractured and weathered. The differences in rock resistance and downwearing rates observed along the shore platforms were highly dependent on thickness of sediment cover and shoreline configuration. These characteristics favoured stronger rock surfaces in areas exposed to the longest wave fetch, but also washing by meltwaters from decaying ice-foot. The results of ERT survey suggest that most of the rocky capes and platforms are free of continuous permafrost and frozen ground conditions develop further inland along mountain slopes and plateaux. The results presented in this paper emphasize the richness of microrelief features and processes operating in polar rock coastal environments. This paper is a contribution to the National Science Centre in Poland OPUS project UMO2013/11/B/ST10/00283:'POROCO - Mechanisms controlling the evolution and geomorphology of rock coasts in polar climates'. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-7814.pdf

2018030056 Tubini, Niccolo (Universita' di Trento, Ingegneria Civile, Ambientale e Meccanica/ CUDAM, Trento, Italy); Serafin, Francesco; Gruber, Stephan; Casulli, Vincenzo and Rigon, Riccardo. New insights in permafrost modelling [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4870, 3 ref., 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Simulating freezing soil has ignored for long time in mainstream surface hydrology. However, it has indubitably a large influence on soil infiltrability and an even larger influence on the soil energy budget, and, over large spatial scales, a considerable feedback on climate. The topic is difficult because it involves concepts of disequilibrium Thermodynamics and also because, once solved the theoretical problem, integration of the resulting partial differential equations in a robust manner, is not trivial at all. In this abstract, we are presenting a new algorithm to estimate the water and energy budget in freezing soils. The first step is a derivation of a new equation for freezing soil mass budget (called generalized Richards equation) based on the freezing equals drying hypothesis (Miller 1965). The second step is the re-derivation of the energy budget. Finally there is the application of new techniques based on the double nested Newton algorithm (Casulli and Zanolli, 2010) to integrate the coupled equations. Some examples of the freezing dynamics and comparison with the Dall'Amico et al. (2011) algorithm are also shown. References Casulli, V., & Zanolli, P. (2010). A nested newton-type algorithm for finite colume methods solving Richards' equation in mixed form. SIAM J. SCI. Comput., 32(4), 2225-2273. Dall'Amico, M., Endrizzi, S., Gruber, S., & Rigon, R. (2011). A robust and energy-conserving model of freezing variably-saturated soil. The Cryosphere, 5(2), 469-484. URL: http://doi.org/10.5194/tc-5-469-2011 Miller, R.: Phase equilibria and soil freezing, in: Permafrost: Proceedings of the Second International Conference. Washington DC: National Academy of Science-National Research Council, 287, 193-197, 1965. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4870.pdf

2018031626 van Huissteden, Ko (Vrije Universiteit, Faculty of Earth and Life Sciences, Earth Sciences, Amsterdam, Netherlands); Heijmans, Monique; Dean, Josh; Meisel, Ove; Goovaerts, Arne; Parmentier, Frans-Jan; Schaepman-Strub, Gabriela; Marchesini, Luca Belelli; Kononov, Alexander; Maximov, Trofim; Borges, Alberto and Bouillon, Steven. Thaw pond dynamics and carbon emissions in a Siberian lowland tundra landscape [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5661, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

Arctic climate change induces drastic changes in permafrost surface wetness. As a result of thawing ground ice bodies, ice wedge troughs and thaw ponds are formed. Alternatively, ongoing thaw may enhance drainage as a result of increased interconnectedness of thawing ice wedge troughs, as inferred from a model study (Liljedahl et al., 2016, Nature Geoscience, DOI: 10.1038/NGEO2674). However, a recent review highlighted the limited predictability of consequences of thawing permafrost on hydrology (Walvoord and Kurylyk, 2016, Vadose Zone J., DOI:10.2136/vzj2016.01.0010). Overall, these changes in tundra wetness modify carbon cycling in the Arctic and in particular the emissions of CO2 and CH4 to the atmosphere, providing a possibly positive feedback on climate change. Here we present the results of a combined remote sensing, geomorphological, vegetation and biogechemical study of thaw ponds in Arctic Siberian tundra, at Kytalyk research station near Chokurdakh, Indigirka lowlands. The station is located in an area dominated by Pleistocene ice-rich "yedoma" sediments and drained thaw lake bottoms of Holocene age. The development of three types of ponds in the Kytalyk area (polygon centre ponds, ice wedge troughs and thaw ponds) has been traced with high resolution satellite and aerial imagery. The remote sensing data show net areal expansion of all types of ponds. Next to formation of new ponds, local vegetation change from dry vegetation types to wet, sedge-dominated vegetation is common. Thawing ice wedges and thaw ponds show an increase in area and number at most studied locations. In particular the area of polygon centre ponds increased strongly between 2010 and 2015, but this is highly sensitive to antecedent precipitation conditions. Despite a nearly 60% increase of the area of thawing ice wedge troughs, there is no evidence of decreasing water surfaces by increasing drainage through connected ice wedge troughs. The number of thaw ponds shows an equilibrium between newly formed and disappearing ponds, although their net area increased by 16%. The disappearing of ponds was mostly the result of vegetation succession, rather than drainage. This vegetation succession results from an invasion by sedges, followed by establishment of Sphagnum and seedlings of dwarf shrubs. The formation of thaw ponds and troughs resulting from small-scale permafrost collapse results in a drastic change of CH₄ and CO₂ emissions, from near-zero emission or uptake to high emission. New water surfaces with drowned dry tundra vegetation show the highest emission. However, rapid vegetation succession may mitigate these emissions over time, in particular in the relatively shallow thaw ponds. In contrast, the polygon centre ponds with a stable, oligotrophic vegetation show modest and constant CH₄ emission and CO₂ uptake. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5661.pdf

2018030129 Zubrzycki, Sebastian (Universität Hamburg, Hamburg, Germany); Pfeiffer, Eva-Maria; Kutzbach, Lars and Desiatkin, Aleksei. Organic carbon deposits of soils overlying the ice complex in the Lena River delta [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5031, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The Lena River Delta (LRD) is located in northeast Siberia and extends over a soil covered area of around 21,500 km². LRD likely stores more than half of the entire soil organic carbon (SOC) mass stored in deltas affected by permafrost. LRD consists of several geomorphic units. Recent studies showed that the spatially dominating Holocene units of the LRD (61% of the area) store around 240 Tg of SOC and 12 Tg of nitrogen (N) within the first meter of ground. These units are a river terrace dominated by wet sedge polygons and the active floodplains. About 50% of these reported storages are located in the perennially frozen ground below 50 cm depth and are excluded from intense biogeochemical exchange with the atmosphere today. However, these storages are likely to be mineralized in near future due to the projected temperature increases in this region. A substantial part of the LRD (1,712 km²) belongs to the so-called Ice Complex (Yedoma) Region, which formed during the Late Pleistocene. This oldest unit of the LRD is characterized by extensive plains incised by thermo-erosional valleys and large thermokarst depressions. Such depressions are called Alases and cover around 20% of the area. Ice Complex deposits in the LDR are known to store high amounts of SOC. However, within the LRD no detailed spatial studies on SOC and N in the soils overlying Ice Complex and thermokarst depressions were carried out so far. We present here our "investigation in progress" on soils in these landscape units of the LRD. Our first estimates, based on 69 pedons sampled in 2008, show that the mean SOC stocks for the upper 30 cm of soils on both units were estimated at 13.0 kg m²± 4.8 kg m² on the Ice Complex surfaces and at 13.1 kg m² ± 3.8 kg m² in the Alases. The stocks of N were estimated at 0.69 kg m² ± 0.25 kg m² and at 0.70 kg m² ± 0.18 kg m² on the Ice Complex surfaces and in the Alases, respectively. The estimated SOC and N pools for the depth of 30 cm within the investigated part of the LRD add to 20.9 Tg and 1.1 Tg, respectively. The Ice Complex surfaces (1,313 km²) store 17.1 ± 6.3 Tg SOC and 0.9 ± 0.3 Tg N, whereas the Alases (287 km²) store 3.8 ± 1.1 Tg SOC and 0.2 ± 0.05 Tg N within the investigated depth of 30 cm. Further analyses of the soil core material collected in 2015 will provide SOC and N pool estimates for a depth of 100 cm including both, the seasonally active layer and the perennially frozen ground. With continuing advanced analyses of an available digital elevation model, slopes will be designated with their extents and inclinations since the planar extents of slopes derived from satellite imagery do not correspond to the actual slope soil surface area, which is vital for spatial SOC and N storage calculations as well as trace gas release estimates. The actual soil surface area of slopes will be calculated prior to result extrapolations. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-5031.pdf

2018030112 Zubrzycki, Sebastian (Universität Hamburg, Hamburg, Germany); Pfeiffer, Eva-Maria and Kutzbach, Lars. Genesis and diversity of Cryosols of the northeast Siberian Lena River delta [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4995, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.

The North-Siberian Lena River Delta (LRD) is the largest Arctic delta and an important interface between the Arctic Ocean in the North and the large Siberian land masses in the South. LRD consists not only of Holocene deltaic sediment deposits as a river terrace and the modern active floodplains but also of remnants of the former Pleistocene mainland including large islands of ice-complex sediments and the Arga-Muora-Sise Island, which is composed of pure sand sediments of still debated origin. The highly diverse landscape structure of LRD is reflected by a great variety of permafrost-affected soils (cryosols). This study aims at describing this great cryosol diversity and at analysing the dominant soil-forming processes in this comparatively scarcely studied soil region. The soil development in the investigated continuous permafrost region is limited by the short thawing period of around three months (June to September) and takes place in the shallow (below 1 m) seasonally thawed active layer. The geological parent material plays an important role for the development of soils in the LRD region. The distribution of the various soil types closely follows the pattern of the geomorphic units characterised by differing sedimentation conditions. The properties and genesis of the soils on the Holocene river terrace and the modern floodplains are strongly affected by the enormous amounts of fluvial sediments (about 12 x 10⁶ tons per year) brought by the Lena River into its delta. The fluvial sedimentation together with the also pronounced aeolian sedimentation results in a fast vertical growth of soils. The upward rise of the soil surface leads to an upward movement of the permafrost table resulting in fast incorporation of soil material formed in the supra-permafrost zone into the permafrost. Due to the morphodynamics of ice-wedge polygons and resulting formation of patterned ground with elevated rims and depressed and water-saturated centres, the Holocene river terrace of the delta is in its main extent covered by a soil complex of Glaci-Turbic Cryosols and Hapli-Histic Cryosols. The active floodplain levels are dominated by sandy or gleyic Fluvi Gleyic Cryosols or Areni Fluvic Cryosols. The surfaces of the Arga-Muora-Sise Island are frequently reshaped by aeolian sedimentation and erosion. The soils on these scarcely vegetated landscapes are dominated by cryoturbated and sand-rich soils with high moisture contents, e.g., various Areni-Turbic Cryosols and Aqui-Turbic Cryosols. The modern soils covering the older Pleistocene ice-complex plains are influenced by wide ice-wedge net structures and consist of a soil complex of Glaci-Turbic Cryosols and Gleyi-Histic Cryosols. The widespread thermokarst depressions within the ice-complex are covered by Histi-Turbic Cryosols and Gleyi-Histic Cryosols, whereas the slopes are dominated by Aqui-Turbic Cryosols and Gleyi-Cryic Cryosols. For the largely unexplored hinterland of LRD it can be assumed that the active genesis of the soils lasts longer than in the active delta regions due to a much lower sedimentation and more stable surface conditions. In these regions widespread cryoturbated and peat-rich soils like Histi-Turbic Cryosols and Histic Cryosols. An increased understanding of spatial variability and genesis of permafrost-affected soils is essential for meaningful predictions of climate change consequences in Arctic permafrost regions. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-4995.pdf

2018029372 Stecca, Guglielmo (National Institute of Water and Atmospheric Research, Christchurch, New Zealand); Siviglia, Annunziato and Blom, Astrid. An accurate numerical solution to the Saint-Venant-Hirano model for mixed-sediment morphodynamics in rivers: in Numerical modelling of river morphodynamics; latest developments and remaining challenges (Siviglia, Annunziato, editor; et al.), Advances in Water Resources, 93(Part A), p. 39-61, illus. incl. 1 table, 63 ref., July 2016. Meeting: European Geosciences Union general assembly session on Numerical modelling and experiments in river morphodynamics, April 27-May 2, 2014, Vienna, Austria.

We present an accurate numerical approximation to the Saint-Venant-Hirano model for mixed-sediment morphodynamics in one space dimension. Our solution procedure originates from the fully-unsteady matrix-vector formulation developed in [54]. The principal part of the problem is solved by an explicit Finite Volume upwind method of the path-conservative type, by which all the variables are updated simultaneously in a coupled fashion. The solution to the principal part is embedded into a splitting procedure for the treatment of frictional source terms. The numerical scheme is extended to second-order accuracy and includes a bookkeeping procedure for handling the evolution of size stratification in the substrate. We develop a concept of balancedness for the vertical mass flux between the substrate and active layer under bed degradation, which prevents the occurrence of non-physical oscillations in the grainsize distribution of the substrate. We suitably modify the numerical scheme to respect this principle. We finally verify the accuracy in our solution to the equations, and its ability to reproduce one-dimensional morphodynamics due to streamwise and vertical sorting, using three test cases. In detail, (i) we empirically assess the balancedness of vertical mass fluxes under degradation; (ii) we study the convergence to the analytical linearised solution for the propagation of infinitesimal-amplitude waves [54], which is here employed for the first time to assess a mixed-sediment model; (iii) we reproduce Ribberink's E8-E9 flume experiment [46].

DOI: 10.1016/j.advwatres.2015.05.022

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