Permafrost Monthly Alerts (PMAs)

2019032088 Blöthe, Jan H. (University of Bonn, Department of Geography, Bonn, Germany); Rosenwinkel, Swenja; Hoser, Thorsten and Korup, Oliver. Rock-glacier dams in high Asia: Earth Surface Processes and Landforms, 44(3), p. 808-824, illus. incl. 5 tables, 113 ref., March 15, 2019.

Rock glaciers in semiarid mountains contain large amounts of ice and might be important water stores aside from glaciers, lakes, and rivers. Yet whether and how rock glaciers interact with river channels in mountain valleys remains largely unresolved. We examine the potential for rock glaciers to block or disrupt river channels, using a new inventory of more than 2000 intact rock glaciers that we mapped from remotely sensed imagery in the Karakoram (KR), Tien Shan (TS), and Altai (ALT) mountains. We find that between 5% and 14% of the rock glaciers partly buried, blocked, diverted or constricted at least 95 km of mountain rivers in the entire study area. We use a Bayesian robust logistic regression with multiple topographic and climatic inputs to discern those rock glaciers disrupting mountain rivers from those with no obvious impacts. We identify elevation and potential incoming solar radiation (PISR), together with the size of feeder basins, as dominant predictors, so that lower-lying and larger rock glaciers from larger basins are more likely to disrupt river channels. Given that elevation and PISR are key inputs for modelling the regional distribution of mountain permafrost from the positions of rock-glacier toes, we infer that river-blocking rock glaciers may be diagnostic of non-equilibrated permafrost. Principal component analysis adds temperature evenness and wet-season precipitation to the controls that characterise rock glaciers impacting on rivers. Depending on the choice of predictors, the accuracy of our classification is moderate to good with median posterior area-under-the-curve values of 0.71-0.89. Clarifying whether rapidly advancing rock glaciers can physically impound rivers, or fortify existing dams instead, deserves future field investigation. We suspect that rock-glacier dams are conspicuous features that have a polygenetic history and encourage more research on the geomorphic coupling between permafrost lobes, river channels, and the sediment cascades of semiarid mountain belts. Copyright 2018 John Wiley & Sons, Ltd.

DOI: 10.1002/esp.4532

2019032137 Ceperley, Elizabeth G. (University of Wisconsin at Madison, Department of Geoscience, Madison, WI); Marcott, Shaun A.; Rawling, J. Elmo; Zoet, Lucas K. and Zimmerman, Susan R. H. The role of permafrost on the morphology of an MIS 3 moraine from the southern Laurentide ice sheet: Geology (Boulder), Pre-Issue Publication, illus. incl. geol. sketch map, 31 ref., March 21, 2019. GSA Data Repository item 2019172.

The Laurentide Ice Sheet (LIS) represents the single largest contributor to global sea level during the late Pleistocene glacial-interglacial cycle. Fluctuations of global sea level prior to the Last Glacial Maximum (LGM; 26-19 ka) are well documented, but the terrestrial extent of the LIS prior to the LGM is uncertain. In central Wisconsin, United States, three north-south-trending end moraines of the LIS are preserved. The two eastward moraines are constrained to the LGM through radiocarbon and surface exposure dating methods, while the westward moraine is constrained only by relative dating techniques and is estimated to be up to >125 ka. Here, we report surface exposure ages from this westward moraine (the Arnott moraine) and demonstrate that the LIS reached an equivalent extent to its LGM position at ca. 35 ka, during Marine Isotope Stage (MIS) 3. These new age constraints for the Arnott moraine are significantly younger than prior estimates, which were based on sediment weathering and low-relief moraine morphology. To address this dichotomy between the relatively young exposure dates and the low relief, we applied a landscape diffusion model to the Arnott moraine and found that during permafrost conditions, intense erosion can act to efficiently and quickly smooth the moraine surface. This study connects the LIS as a potential source for sea-level lowering during MIS 3 while simultaneously demonstrating the inherent uncertainty associated with relative dating techniques if nonlinear erosional conditions are not accounted for in periglacial terrains.

DOI: 10.1130/G45874.1

2019033914 Ji Yukun (China University of Mining and Technology, Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou, China); Zhou Guoqing; Zhou Yang and Vandeginste, Veerle. Frost heave in freezing soils; a quasi-static model for ice lens growth: Cold Regions Science and Technology, 158, p. 10-17, illus. incl. 1 table, 34 ref., February 2019. Based on Publisher-supplied data.

Frost heave can have a very destructive impact on infrastructure in permafrost regions. The complexity of nanoscale ice-mineral interactions and their relation to the macroscale frost heave phenomenon make ice lens growth modeling an interesting but challenging task. Taking into account the limiting assumption of the constant segregation temperature in the segregation potential model, we propose here a new quasi-static model for ice lens growth under a time varying temperature based on the water activity criterion. In this model, the conventional pressure potential gradient in Darcy's law is replaced by a water activity based chemical potential gradient for the calculation of water flow velocity, which provides a better prediction of ice lens growth and is useful to describe the ice nucleation and the state of water at a specific temperature. Moreover, based on the analysis of the new developed model, a mathematical description of the segregation potential is provided here. The modified Kozeny-Carman equation is applied to determine the water permeability of a given soil. In our new model, the effects of the equivalent water pressure are taken into account to modify the freezing characteristic function. Hence, the temperature- and equivalent water pressure-dependent hydraulic permeability in the frozen fringe is mathematically determined and improved. By coupling the quasi-static model with the modified hydraulic permeability function, the numerical calculation of ice lens growth is validated based on the experimental data of the temperature of the ice lens measured in the laboratory. The prediction of ice lens growth using the proposed method contributes and facilitates the simplified calculation of frost heave in the field and/or laboratory scenarios at a quasi-static state, and thus enables a better understanding of phase change and fluid flow in partially frozen granular media (soils).

DOI: 10.1016/j.coldregions.2018.11.003

2019033919 Kong, Xiangbing (Laval University, Department of Civil and Water Engineering, Quebec, QC, Canada); Doré, Guy and Calmels, Fabrice. Thermal modeling of heat balance through embankments in permafrost regions: Cold Regions Science and Technology, 158, p. 117-127, illus. incl. 6 tables, sketch map, 36 ref., February 2019. Based on Publisher-supplied data.

Permafrost is widely distributed in the northern hemisphere and permafrost degradation underneath transportation infrastructure is on-going due to many factors, such as climate change. The test site, constructed in 2008 along Alaska Highway at Beaver Creek, Yukon, Canada, provides valuable information on the long-term thermal response of permafrost underneath transportation infrastructure, to disturbances induced by constructions and climate change. The temperature data collected can also be used to calibrate thermal models to gain insight into relative effects of different factors on the sensitivity of the ground thermal regime underneath transportation infrastructure to on-going climate change. A finite-element, 2D heat conduction model, taking ice-water phase change into account, was developed based on the Beaver Creek experimental site characteristics and conditions. To increase the accuracy of the model, site-specific parameters, such as soil properties, near surface air temperature, and embankment dimension, were measured and used as input parameters. After calibration of the model, sensitivity analysis of certain input parameters, such as air temperature, embankment thickness and ground temperature, was conducted for different site conditions. The model was used to develop an engineering design chart allowing assessing the heat balance at the interface between embankment and natural ground. The heat balance analysis and the design chart are based on the results of sensitivity analysis and validated using the data from the Tasiujaq airstrip in Northern Quebec, Canada.

DOI: 10.1016/j.coldregions.2018.11.013

2019033891 Rey, David M. (Colorado School of Mines, Hydrologic Science and Engineering Program, Golden, CO); Walvoord, Michelle; Minsley, Burke; Rover, Jennifer and Singha, Kamini. Investigating lake-area dynamics across a permafrost-thaw spectrum using airborne electromagnetic surveys and remote sensing time-series data in Yukon Flats, Alaska: Environmental Research Letters, 14(2), Paper no. 025001, illus. incl. 1 table, sketch maps, 52 ref., February 2019. Part of a special issue entitled Resiliency and vulnerability of arctic and boreal ecosystems to environmental change; advances and outcomes of ABoVE (the Arctic Boreal Vulnerability Experiment, edited by Goetz, S., et al.

Lakes in boreal lowlands cycle carbon and supply an important source of freshwater for wildlife and migratory waterfowl. The abundance and distribution of these lakes are supported, in part, by permafrost distribution, which is subject to change. Relationships between permafrost thaw and lake dynamics remain poorly known in most boreal regions. Here, new airborne electromagnetic (AEM) data collected during June 2010 and February 2016 were used to constrain deep permafrost distribution. AEM data were coupled with Landsat-derived lake surface-area data from 1979 through 2011 to inform temporal lake behavior changes in the 35 500-km² Yukon Flats ecoregion of Alaska. Together, over 1500 km of AEM data, and roughly 30 years of Landsat data were used to explore processes that drive lake dynamics across a variety of permafrost thaw states not possible in studies conducted with satellite imagery or field measurements alone. Clustered time-series data identified lakes with similar temporal dynamics. Clusters possessed similarities in lake permanence (i.e. ephemeral versus perennial), subsurface permafrost distribution, and proximity to rivers and streams. Of the clustered lakes, ~66% are inferred to have at least intermittent connectivity with other surface-water features, ~19% are inferred to have shallow subsurface connectivity to other surface water features that served as a low-pass filter for hydroclimatic fluctuations, and ~15% appear to be isolated by surrounding permafrost (i.e. no connectivity). Integrated analysis of AEM and Landsat data reveals a progression from relatively synchronous lake dynamics among disconnected lakes in the most spatially continuous, thick permafrost to quite high spatiotemporal heterogeneity in lake behavior among variably-connected lakes in regions with notably less continuous permafrost. Variability can be explained by the preferential development of thawed permeable gravel pathways for lateral water redistribution in this area. The general spatial progression in permafrost thaw state and lake area behavior may be extended to the temporal dimension. However, extensive permafrost thaw, beyond what is currently observed, is expected to promote ubiquitous subsurface connectivity, eventually evolving to a state of increased lake synchronicity. Copyright (Copyright) 2019 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/aaf06f

2019033917 Rivière, Agnès (PSL University, MINES ParisTech, Centre of Geosciences, Fontainebleau, France); Jost, Anne; Gonçalvès, Julio and Font, Marianne. Pore water pressure evolution below a freezing front under saturated conditions; large-scale laboratory experiment and numerical investigation: Cold Regions Science and Technology, 158, p. 76-94, illus. incl. 3 tables, 38 ref., February 2019. Based on Publisher-supplied data.

Subpermafrost aquifer hydrodynamics is generally poorly known due to monitoring technology issues. The few available data show that this aquifer is confined below continuous permafrost due to ice expansion. We conducted a 2 m´1 m´1 m sand box experiment under controlled conditions in a cold room to (1) evaluate the confinement of the unfrozen part of a saturated porous medium below a propagating freezing/thawing front, (2) assess the associated uplift of the soil surface, and therefore (3) quantify how the ice expansion translates into frost heave and excess pore-water pressure in the unfrozen part below the freezing soil. Pore water pressure, soil temperature and soil heave were monitored inside the sand box during a 70-day freeze-thaw cycle. A transient fully coupled heat transport and water flow model (called ) was developed to reproduce the freeze-thaw experiment numerically. It takes into account excess pore-water pressure related to pore water phase changes and uses a simple hydro-mechanical term based on the storage coefficient to estimate soil heave. Fairly good agreement was obtained between measured and simulated pressure heads in the unfrozen part below the freezing front over time. Both experimental and numerical approaches show that the ice expansion is translated into excess pore-water pressure (maximum pore water pressure: 5.5 m) and frost heave (2.2 cm).

DOI: 10.1016/j.coldregions.2018.11.005

2019033892 Streletskiy, Dmitry A. (George Washington University, Department of Geography, Washington, DC); Suter, Luis J.; Shiklomanov, Nikolay I.; Porfiriev, Boris N. and Eliseev, Dmitry O. Assessment of climate change impacts on buildings, structures and infrastructure in the Russian regions on permafrost: Environmental Research Letters, 14(2), Paper no. 025003, illus. incl. 3 tables, sketch maps, 41 ref., February 2019. Part of a special issue entitled Focus on northern Eurasia in the global earth and human systems; changes, interactions, and sustainable societal development, edited by Groisman, P., et al.

Russian regions containing permafrost play an important role in the Russian economy, containing vast reserves of natural resources and hosting large-scale infrastructure to facilitate these resources' exploitation. Rapidly changing climatic conditions are a major concern for the future economic development of these regions. This study examines the extent to which infrastructure and housing are affected by permafrost in Russia and estimates the associated value of these assets. An ensemble of climate projections is used as a forcing to a permafrost-geotechnical model, in order to estimate the cost of buildings and infrastructure affected by permafrost degradation by mid-21st century under RCP 8.5 scenario. The total value of fixed assets on permafrost was estimated at 248.6 bln USD. Projected climatic changes will affect 20% of structures and 19% of infrastructure assets, costing 16.7 bln USD and 67.7 bln USD respectively to mitigate. The total cost of residential real estate on permafrost was estimated at 52.6 bln USD, with 54% buildings affected by significant permafrost degradation by the mid-21st century. The paper discusses the variability in climate-change projections and the ability of Russia's administrative regions containing permafrost to cope with projected climate-change impacts. The study can be used in land use planning and to promote the development of adaptation and mitigation strategies for addressing the climate-change impacts of permafrost degradation on infrastructure and housing. Copyright (Copyright) 2019 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/aaf5e6

2019033920 Wagner, Anna M. (U. S. Army Cold Regions Research and Engineering Laboratory, Ft. Wainwright, AK) and Barker, Amanda J. Distribution of polycyclic aromatic hydrocarbons (PAHs) from legacy spills at an Alaskan Arctic site underlain by permafrost: Cold Regions Science and Technology, 158, p. 154-165, illus. incl. 2 tables, 40 ref., February 2019. Based on Publisher-supplied data.

Widespread polycyclic aromatic hydrocarbon (PAH) contamination resulting from petroleum spills at military and industrial sites along the Arctic Ocean Coast is a major issue in the Alaskan Arctic. Polycyclic aromatic hydrocarbons (PAHs) consist of one or more fused aromatic rings and comprise a major portion of petroleum products like fuels. PAHs are commonly found in a variety of geomedia and are considered environmentally persistent, toxic, and carcinogenic. In the present study, the subsurface distribution of PAHs was investigated at a former U.S. Department of the Navy site in northern Alaska using laser-induced fluorescence coupled with ultraviolet optical screening tool (LIF-UVOST). The former Naval Arctic Research Laboratory (NARL) study site has historical presence just outside the city of Utqiagvik, Alaska (formerly Barrow) and has a long history of petroleum spills since the early 1950s primarily at the Airstrip and Powerhouse sites. To determine the extent of PAH accumulation in the subsurface a total of 143 vertical soil profiles were characterized using LIF-UVOST during September 2015 (87 at the Airstrip site and 56 at the Powerhouse site). We also compared the intensities of different wavelengths (350 versus 500 nm) to estimate spill source and we found a substantial accumulation of PAHs in the surface and subsurface at both sites and vertical distribution of PAHs was primarily heterogeneous, varying as a function of probing locations and soil depth. Both sites were found to have no correlation between depth of the maximum fluorescence signal and depth of the probing refusal depth (top of permafrost). Using LIF-UVOST for the direct chemical sensing of PAHs proved to be a useful tool and revealed unique signature PAH fluorescence responses when comparing 350 and 500 nm intensities between the Airstrip and Powerhouse sites, likely attributable to the original source of the spill. Results from this project can be directly used for other potential studies, including planning remediation strategies and investigating local bodies of water for PAH transport.

DOI: 10.1016/j.coldregions.2018.11.012

2019033886 Mauritz, Marguerite (Northern Arizona University, Center for Ecosystem Society and Science, Flagstaff, AZ); Celis, Gerardo; Ebert, Chris; Hutchings, Jack A.; Ledman, J.; Natali, Susan M.; Pegoraro, E.; Salmon, Verity G.; Schädel, Christina; Taylor, Meghan and Schuur, E. A. G. Using stable carbon isotopes of seasonal ecosystem respiration to determine permafrost carbon loss: Journal of Geophysical Research: Biogeosciences, 124(1), p. 46-60, illus. incl. 3 tables, 97 ref., January 2019.

High latitude warming and permafrost thaw will expose vast stores of deep soil organic carbon (SOC) to decomposition. Thaw also changes water movement causing either wetter or drier soil. The fate of deep SOC under different thaw and moisture conditions is unclear. We measured weekly growing-season d¹³C of ecosystem respiration (Recod¹³C) across thaw and moisture conditions (Shallow-Dry; Deep-Dry; Deep-Wet) in a soil warming manipulation. Deep SOC loss was inferred from known d¹³C signatures of plant shoot, root, surface soil, and deep soil respiration. In addition, a 2-year-old vegetation removal treatment (No Veg) was used to isolate surface and deep SOC decomposition contributions to Reco. In No Veg, seasonal Recod¹³C indicated that deep SOC loss increased as the soil column thawed, while in vegetated areas, root contributions appeared to dominate Reco. The Recod¹³C differences between Shallow-Dry and Deep-Dry were significant but surprisingly small. This most likely suggests that, under dry conditions, soil warming stimulates root and surface SOC respiration with a negative ¹³C signature that opposes the more positive ¹³C signal from increased deep SOC respiration. In Deep-Wet conditions, Recod¹³C suggests reduced deep SOC loss but could also reflect altered diffusion or methane (CH₄) dynamics. Together, these results demonstrate that frequent Recod¹³C measurements can detect deep SOC loss and that plants confound the signal. In future studies, soil profile d¹³C measurements, vegetation removal across thaw gradients, and isotopic effects of CH₄ dynamics could further deconvolute deep SOC loss via surface Reco. Abstract Copyright (2018). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2018JG004619

2019031923 Cai, Lei (University of Alaska-Fairbanks, International Arctic Research Center, Fairbanks, AK); Alexeev, Vladimir A.; Arp, Christopher D.; Jones, Benjamin M. and Romanovsky, Vladimir E. Modelling the impacts of projected sea ice decline on the low atmosphere and near-surface permafrost on the North Slope of Alaska: International Journal of Climatology, 38(15), p. 5491-5504, illus. incl. 1 table, sketch map, 67 ref., December 2018.

This model-based study assesses the response of the lower atmosphere and near-surface permafrost on the North Slope of Alaska to projections in sea ice decline. The Weather Research and Forecast model, with polar optimization (polar WRF), was configured for the North Slope of Alaska and the adjacent Arctic Ocean and run for two decade-long control periods, the 1970s and the 2040s. Community Earth System Model output was used to drive the polar WRF model. By swapping the sea ice coverage in the control cases, two polar WRF sensitivity experiments were designed to quantify the changes in the low atmosphere and near-surface permafrost in response to projected declines in sea ice extent. The strongest impacts of sea ice decline occur primarily during the late fall and early winter. These include increases in surface air temperature, surface humidity, total cloud cover, and precipitation amount. Future impacts of sea ice decline are projected to become weaker over time in the late fall and early winter while becoming more prominent in late spring and early summer. Projected sea ice decline also inhibits low-level cloud formation in summer as a result of destabilization of the boundary layer. Sensitivity experiments by polar WRF and Geophysical Institute Permafrost Laboratory model, respectively, suggest that sea ice decline explains approximately 20% of both the atmospheric and permafrost warmings on a mean annual basis compared to the overall projected warming under the RCP4.5 scenario. Abstract Copyright (2018), Royal Meteorological Society.

DOI: 10.1002/joc.5741

2019031924 Chang Yan (Chinese Academy of Sciences/Northwest Institute of Eco-Environment and Resources, Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions, Lanzhou, China); Lyu Shihua; Luo Siqiong; Li Zhaoguo; Fang Xuewei; Chen Boli; Li Ruiqing and Chen Shiqiang. Estimation of permafrost on the Tibetan Plateau under current and future climate conditions using the CMIP5 data: International Journal of Climatology, 38(15), p. 5659-5676, illus. incl. 4 tables, 64 ref., December 2018.

Permafrost has significant impacts on climate change through its strong interaction with the climate system. In order to better understand the permafrost variation and the role it plays in climate change, model outputs from Phase 5 of the Coupled Model Intercomparison Project (CMIP5) are used in the present study to diagnose the near-surface permafrost on the Tibetan Plateau (TP), assess the abilities of the models to simulate present-day (1986-2005) permafrost and project future permafrost change on the TP under four different representative concentration pathways (RCPs). The results indicate that estimations of present-day permafrost using the surface frost index (SFI) and the Kudryavtsev method (KUD) show a spatial distribution similar to that of the frozen soil map on the TP. However, the permafrost area calculated via the KUD is larger than that calculated via the SFI. The SFI produces a present-day permafrost area of 127.2´10⁴ km². The results also indicate that the permafrost on the TP will undergo regional degradation, mainly at the eastern, southern and northeastern edges, during the 21st century. Furthermore, most of the sustainable permafrost will probably exist only in the northwestern TP by 2099. The SFI also indicates that the permafrost area will shrink by 13.3´10⁴ km² (9.7%) and 14.6´10⁴ km² (10.5%) under the RCP4.5 and RCP8.5 scenarios, respectively, in the next 20 years and by 36.7´10⁴ km² (26.6%) and 45.7´10⁴ km² (32.7%), respectively, in the next 50 years. The results are helpful for us to better understand the permafrost response to climate change over the TP, further investigate the physical mechanism of the freeze-thaw process and improve the model parameterization scheme. Abstract Copyright (2018), Royal Meteorological Society.

DOI: 10.1002/joc.5770

2019026701 Iwata, Yukiyoshi (National Agriculture and Food Research Organization, Hokkaido Agricultural Research Center, Hokkaido, Japan); Yanai, Yosuke; Yazaki, Tomotsugu and Hirota, Tomoyoshi. Effects of a snow compaction treatment on soil freezing, snowmelt runoff, and soil nitrate movement; a field scale paired plot experiment: Journal of Hydrology, 567, p. 280-289, illus. incl. 1 table, 41 ref., December 2018.

A frozen soil layer may impede snowmelt infiltration, resulting in a large amount of runoff that influences the soil water balance and anion movement in the soil profile. To examine the relationships among soil frost depth, snowmelt runoff, and nitrate leaching in agricultural fields, we measured both the snowmelt runoff for three winters and other environmental factors including the soil frost depth and nitrate content in a ~10,000 m² field. We divided the field into two subplots: one was maintained in a natural snow cover condition (the control plot), and the snow cover was compacted on the other plot (the treated plot) to enhance the development of the soil frost depth. In all three winters, soil frost depths in the control plot were <0.2 m and very little runoff was observed during the snowmelt period. In contrast, the soil frost depth became >0.4 m and a large amount of snowmelt runoff was observed in the treated plot. The depth of the peak nitrate concentration after the snowmelt period was shallower in the treated plot compared to the control plot. Moreover, a significant linear relationship was observed between (1) the amount of nitrate in the 0-0.3 m depth after the snowmelt period and (2) the total amount of snowmelt infiltration calculated by subtracting the amount of snowmelt runoff from the amount of snowmelt water. These results suggest that snow compaction can be a promising technique to develop a uniform soil frost depth in large-scale fields, which consequently controls the soil water and nutrient movement in the soil layer.

DOI: 10.1016/j.jhydrol.2018.10.016

2019031974 Richter, Detlev K. (Ruhr University Bochum, Institute for Geology, Mineralogy and Geophysics, Bochum, Germany); Scholz, Denis; Jöns, Niels; Neuser, Rolf D. and Breitenbach, Sebastian F. M. Coarse-grained cryogenic aragonite as end-member of mineral formation in dolomite caves: Sedimentary Geology, 376, p. 136-146, illus. incl. 3 tables, geol. sketch map, 73 ref., November 15, 2018.

Cryogenic carbonate particles (single crystals and aggregates) have recently been recognized as important witnesses of permafrost dynamics, as they can be used to estimate the thickness and timing of development of permafrost. In this study, the petrography and geochemistry of coarse-grained cryogenic aragonite (CGC_Ar) identified in Zoolithen Cave in NE Bavaria, Germany, are described in detail for the first time. We provide a sequence of carbonate precipitation during freezing, where CGC_Ar mark the final crystallization phase in freezing water on ice. Our results support the notion that host rock composition, solution chemistry, and cave ventilation play an important role for aragonite formation in caves.Using petrographic and geochemical evidence we distinguish aragonitic spherulites, and precursory spherulitic and rhombohedral aggregates of magnesian calcite. The aragonitic particles are characterized by very low oxygen isotope (d¹⁸O=-17.1 ppm to -17.8 ppm) and relatively high carbon isotope values (d¹³C=+1.0 ppm to +0.8 ppm). Among the magnesian calcites the spherulitic forms show more negative oxygen and more positive carbon isotope values, compared to rhombohedral crystals (d¹⁸O=-17.2 ppm to -15.0 ppm vs. -16.2 ppm to -9.9 ppm; d¹³C=+0.4 ppm to -3.5 ppm vs. -0.8 ppm to -4.8 ppm). This sequence is mirrored also in mineralogical/geochemical data from the spherulitic CGC_Ar, where the calcite fibers show an increase in Mg from 1.5-2.5 mol-% to 7.5-10 mol-% MgCO₃, before aragonitic spherulites are formed.U-series dates from cryocalcites formed prior to the identified CGC_Ar in Zoolithen Cave place the formation of the former into the last glacial to between 28.75 ka and 30.63 ka. Aragonitic spherulites on cryocalcites represent the end-member of the succession cold water calcite-cryocalcite-cryoaragonite. The sampling depth at 30 m below surface represents a minimum thickness of last glacial permafrost in this location in Central Europe.

DOI: 10.1016/j.sedgeo.2018.08.006

2019029384 Littlefair, Cara A. (University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada) and Tank, Suzanne E. Biodegradability of thermokarst carbon in a till-associated, glacial margin landscape; the case of the Peel Plateau, NWT, Canada: Journal of Geophysical Research: Biogeosciences, 123(10), p. 3293-3307, illus. incl. 4 tables, 86 ref., October 2018.

The Peel Plateau is a characteristic glacial margin landscape, with permafrost comprised of thick, ice-rich glacial tills deposited at the end of the Last Glacial Maximum. Unmodified tills at depth are overlain by a paleo-active layer, created when early Holocene warming deepened regional active layers, enabling organic matter incorporation into now-frozen soils. Ice-rich permafrost encourages retrogressive thaw slumps, which mobilize variable proportions of modern active layer, paleo-active layer, and Pleistocene tills to downstream systems. Here we investigate the biolability of thaw-released dissolved organic carbon (DOC) on the Peel Plateau and compare our results to previous studies from nontill-dominated landscapes. Similar to other Arctic regions, biolability was significantly greater for slump-derived DOC (retrogressive thaw slump runoff) than for DOC from paired, unimpacted locations. However, runoff source was an important control on biolability. Lability was greater for slumps releasing water with a Holocene-like d¹⁸O signature than for slumps with a more Pleistocene-like signature, while a small slump, with runoff d¹⁸O similar to the modern active layer, showed no biolability increase. Similar to other Arctic regions, biolability was strongly related to DOC aromaticity and molecular weight. However, lability also increased significantly with increasing nutrients, which has not been shown universally. Previous work has shown that DOC concentration dynamics differ sharply on the Peel Plateau when compared to other permafrost thaw landscapes. This work indicates that the lability of permafrost DOC may be relatively uniform across variable Arctic regions, although some factors-such as the importance of nutrient status-may need further exploration. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2018JG004461

2019033895 Mu Yanhu (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Ma Wei; Li Guoyu; Niu Fujun; Liu Yongzhi and Mao Yuncheng. Impacts of supra-permafrost water ponding and drainage on a railway embankment in continuous permafrost zone, the interior of the Qinghai-Tibet Plateau: Cold Regions Science and Technology, 154, p. 23-31, illus., 30 ref., October 2018. Based on Publisher-supplied data.

In a permafrost environment, supra-permafrost water is an important local factor affecting the shallow ground thermal regime and also plays a significant role in geotechnical problems. In this study, the impacts of supra-permafrost water ponding and drainage on the thermal regime and settlement characteristics of a railway embankment in continuous permafrost zone, the interior of the Qinghai-Tibet Plateau were investigated using 13-year records (2003-2016) of field measured data. Results showed that, because of the great latent heat of the ponded water alongside the embankment, a zero curtain layer (ZCL) as much as 5.5 m thick developed in and beneath the embankment after embankment construction in 2003. A three-layered thermal regime developed in the embankment and the subgrade. Although crushed rock revetments were installed 5 years after embankment construction, no soil cooling occurred beneath the ZCL and the ZCL remained stable in thickness. Meanwhile, embankment settlement developed quickly and nearly linearly from 2003 to 2012, with a cumulative settlement approaching approximately 160 mm at both the sunny and the shady embankment shoulders. Compression and creep of warm and ice-rich permafrost layer (WIPL) beneath the ZCL are considered as the main contributors to this significant settlement. Following drainage of the ponded water during 2012, the ZCL cooled quickly and completely frozen after two cold seasons. The underlying permafrost table moved upwards into the embankment and the WIPL cooled with time. Embankment settlement also slowed significantly. However, an asymmetrical temperature field developed in the embankment and the subgrade because of the sunny-shady embankment slope effect, leading to differential settlement between the sunny and the shady embankment shoulders.

DOI: 10.1016/j.coldregions.2018.06.007

2019026315 Wang Yuhan (Tsinghua University, Department of Hydraulic Engineering, Beijing, China); Yang Hanbo; Gao Bing; Wang Taihua; Qin Yue and Yang Dawen. Frozen ground degradation may reduce future runoff in the headwaters of an inland river on the northeastern Tibetan Plateau: Journal of Hydrology, 564, p. 1153-1164, illus. incl. 8 tables, sketch map, 74 ref., September 2018.

On the Tibetan Plateau, climate change, particularly increases in air temperature, significantly affects cryospheric and hydrological processes. Based on 5 typical future climate scenarios from the Coupled Model Intercomparison Project (CMIP5) under emission scenario RCP4.5 and a distributed ecohydrological model (GBEHM), this study analyzes the potential characteristics of future climate change (from 2011 to 2060) and the associated effects on the cryospheric and hydrological processes in the upper Heihe River Basin, a typical cold mountain region located on the northeastern Tibetan Plateau. The precipitation, air temperature, and frozen ground elasticities of runoff/evapotranspiration are then estimated based on the simulation results. The typical future climate scenarios suggest that air temperature will increase at an average rate of 0.34 °C/10a in the future and that precipitation will increase slightly by 6 mm/10a under the RCP 4.5 emission scenario. Based on the GBEHM-simulated results, due to the increase in air temperature, glaciers would be reduced to less than 100 million m³ by 2060, the permafrost area would shrink by 23%, the maximum frozen depth of seasonally frozen ground would decrease by 5.4 cm/10a and the active layer depth of the frozen ground would increase by 6.1 cm/10a. Additionally, runoff would decrease by approximately 5 mm/10a, and evapotranspiration would increase by approximately 9 mm/10a. The estimated elasticities indicate that annual runoff would decrease at an average rate of 24 mm/°C and evapotranspiration would increase at an average rate of 21 mm/°C with rising air temperature in the future. The impacts of increased air temperature on hydrological processes are mainly due to changes in frozen ground. The thickening of the active layer of the frozen ground increases the soil storage capacity, leading to decreased runoff and increased evapotranspiration. When the active layer depth increases by 1 cm, annual runoff decreases by approximately 1.3 mm, and annual evapotranspiration increases by approximately 0.9 mm. In addition, the shift from permafrost to seasonal frozen ground increases groundwater infiltration, which decreases surface runoff. Compared to that over the past 50 years, the effect of increased air temperature on the frozen ground in the upper Heihe River Basin will be greater in the future, which would result in a faster reduction in runoff in the future considering the effects of global warming.

DOI: 10.1016/j.jhydrol.2018.07.078

2019031449 Wilkman, Eric (San Diego State University, Department of Biology, San Diego, CA); Zona, Donatella; Tang, Yanfei; Gioli, Beniamino; Lipson, David A. and Oechel, Walter. Temperature response of respiration across the heterogeneous landscape of the Alaskan Arctic tundra: Journal of Geophysical Research: Biogeosciences, 123(7), p. 2287-2302, illus. incl. 4 tables, 130 ref., July 2018.

Predictions of the response of ecosystem respiration to warming in the Arctic are not well constrained, partly due to the considerable spatial heterogeneity of these permafrost-dominated areas. Accurate calculations of in situ temperature sensitivities of respiration (Q₁₀) are vital for the prediction of future Arctic emissions. To understand the impact of spatial heterogeneity on respiration rates and Q₁₀, we compared respiration measured from automated chambers across the main local polygonized landscape forms (high and low centers, polygon rims, polygon troughs) to estimates from the flux-partitioned net ecosystem exchange collected in an adjacent eddy covariance tower. Microtopographic type appears to be the most important variable explaining the variability in respiration rates, and low-center polygons and polygon troughs show the greatest cumulative respiration rates, possibly linked to their deeper thaw depth and higher plant biomass. Regardless of the differences in absolute respiration rates, Q₁₀ is surprisingly similar across all microtopographic features, possibly indicating a similar temperature limitation to decomposition across the landscape. Q₁₀ was higher during the colder early summer and lower during the warmer peak growing season, consistent with an elevated temperature sensitivity under colder conditions. The respiration measured by the chambers and the estimates from the daytime flux-partitioned eddy covariance data were within uncertainties during early and peak seasons but overestimated respiration later in the growing season. Overall, this study suggests that it is possible to simplify estimates of the temperature sensitivity of respiration across heterogeneous landscapes but that seasonal changes in Q₁₀ should be incorporated into model simulations. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2017JG004227

2019031505 Makarov, V. N. (Russian Academy of Sciences, Siberian Branch, Permafrost Institute, Yakutsk, Russian Federation). Ions of organic carboxylic acids (formic, acetic, and oxalic) in the snow cover of permafrost landscapes of boreal eastern Siberia: Geochemistry International, 56(6), p. 608-615, 12 ref., June 2018.

DOI: 10.1134/S0016702918060083

2019026247 Weber, Samuel (University of Zurich, Department of Geography, Zurich, Switzerland); Faillettaz, Jérome; Meyer, Matthias; Beutel, Jan and Vieli, Andreas. Acoustic and microseismic characterization in steep bedrock permafrost on Matterhorn (CH): Journal of Geophysical Research: Earth Surface, 123(6), p. 1363-1385, illus. incl. 1 table, 85 ref., June 2018.

Understanding of processes and factors influencing slope stability is essential for assessing the stability of potentially hazardous slopes. Passive monitoring of acoustic emissions and microseismology provides subsurface information on fracturing (timing and identification of the mechanism) and therefore complement surface displacement data. This study investigates for the first time acoustic and microseismic signals generated in steep, fractured bedrock permafrost, covering the broad frequency range of 1 - 10⁵ Hz. The analysis of artificial forcing experiments using a rebound hammer in a controlled setting led to two major findings: First, statistically insignificant cross correlation between signals indicates that waveforms change strongly with propagation distance. Second, a significant amplification is found in the frequency band 33-67 Hz. This finding is strongly supported by evidence from artificial rockfall events and more importantly by naturally occurring fracture events identified in fracture displacement data. Thus, filtering this frequency band enables enhanced detection of microseismic events relevant for slope stability assessment. The analysis of 2-year time series in this frequency band further suggests that the detected energy rate baseline of all automatically triggered events using the STA/LTA algorithm is not sensitive to temperature forcing, an observation of primary importance for long-term data collection, analysis, and interpretation. The event detection in the established frequency band is not only improved but also not affected by the short- and long-term temperature changes in such a rapidly changing environment. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2018JF004615

2019028194 Bibi, Sadia (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Key Laboratory of Tibetan Environmental Changes and Land Surface Processes, Beijing, China); Wang Lei; Li Xiuping; Zhou Jing; Chen Deliang and Yao Tandong. Climatic and associated cryospheric, biospheric, and hydrological changes on the Tibetan Plateau; a review: International Journal of Climatology, 38(S1), p. e1-e17, illus., 155 ref., April 2018.

We review recent climate changes over the Tibetan Plateau (TP) and associated responses of cryospheric, biospheric, and hydrological variables. We focused on surface air temperature, precipitation, seasonal snow cover, mountain glaciers, permafrost, freshwater ice cover, lakes, streamflow, and biological system changes. TP is getting warmer and wetter, and air temperature has increased significantly, particularly since the 1980s. Most significant warming trends have occurred in the northern TP. Slight increases in precipitation have occurred over the entire TP with clear spatial variability. Intensification of surface air temperature is associated with variation in precipitation and decreases in snow cover depth, spatial extent, and persistence. Rising surface temperatures have caused recession of glaciers, permafrost thawing, and thickening of the active layers over the permafrost. Changing temperatures, precipitation, and other climate system components have also affected the TP biological system. In addition, elevation-dependent changes in air temperature, wind speed, and summer precipitation have occurred in the TP and its surroundings in the past three decades. Before projecting multifaceted interactions and process responses to future climate change, further quantitative analysis and understanding of the change mechanisms is required. Abstract Copyright (2018), Royal Meteorological Society.

DOI: 10.1002/joc.5411

2019025242 Fisher, Joshua B. (California Institute of Technology, Jet Propulsion Laboratory, Pasadena, CA); Hayes, Daniel J.; Schwalm, Christopher R.; Huntzinger, Deborah N.; Stofferahn, Eric; Schaefer, Kevin; Luo, Yiqi; Wullschleger, Stan D.; Goetz, Scott; Miller, Charles E.; Griffith, Peter; Chadburn, Sarah; Chatterjee, Abhishek; Ciais, Philippe; Douglas, Thomas A.; Genet, Hélène; Ito, Akihiko; Neigh, Christopher S. R.; Poulter, Benjamin; Rogers, Brendan M.; Sonnentag, Oliver; Tian, Hanqin; Wang, Weile; Xue, Yongkang; Yang, Zong-Liang; Zeng, Ning and Zhang, Zhen. Missing pieces to modeling the Arctic-Boreal puzzle: Environmental Research Letters, 13(2), Paper no. 020202, illus., 95 ref., February 2018.

NASA has launched the decade-long Arctic-Boreal Vulnerability Experiment (ABoVE). While the initial phases focus on field and airborne data collection, early integration with modeling activities is important to benefit future modeling syntheses. We compiled feedback from ecosystem modeling teams on key data needs, which encompass carbon biogeochemistry, vegetation, permafrost, hydrology, and disturbance dynamics. A suite of variables was identified as part of this activity with a critical requirement that they are collected concurrently and representatively over space and time. Individual projects in ABoVE may not capture all these needs, and thus there is both demand and opportunity for the augmentation of field observations, and synthesis of the observations that are collected, to ensure that science questions and integrated modeling activities are successfully implemented. Copyrigh 2018 The Author(s). Published by IOP Publishing Ltd

DOI: 10.1088/1748-9326/aa9d9a

2019025240 Gaglioti, Benjamin V. (Lamont-Doherty Earth Observatory, Palisades, NY); Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Farquharson, Louise M.; Reanier, Richard E.; Jones, Benjamin M. and Wooller, Matthew J. Aeolian stratigraphy describes ice-age paleoenvironments in unglaciated Arctic Alaska: Quaternary Science Reviews, 182, p. 175-190, illus. incl. geol. sketch map, 76 ref., February 15, 2018.

Terrestrial paleoenvironmental records with high dating resolution extending into the last ice age are rare from the western Arctic. Such records can test the synchronicity and extent of ice-age climatic events and define how Arctic landscapes respond to rapid climate changes. Here we describe the stratigraphy and sedimentology of a yedoma deposit in Arctic Alaska (the Carter Section) dating to between 37,000 and 9000 calibrated radiocarbon years BP (37-9 ka) and containing detailed records of loess and sand-sheet sedimentation, soil development, carbon storage, and permafrost dynamics. Alternation between sand-sheet and loess deposition provides a proxy for the extent and activity of the Ikpikpuk Sand Sea (ISS), a large dune field located immediately upwind. Warm, moist interstadial times (ca. 37, 36.3-32.5, and 15-13 ka) triggered floodplain aggradation, permafrost thaw, reduced loess deposition, increased vegetation cover, and rapid soil development accompanied by enhanced carbon storage. During the Last Glacial Maximum (LGM, ca. 28-18 ka), rapid loess deposition took place on a landscape where vegetation was sparse and non-woody. The most intense aeolian activity occurred after the LGM between ca. 18 and 15 ka when sand sheets fringing the ISS expanded over the site, possibly in response to increasingly droughty conditions as summers warmed and active layers deepened. With the exception of this lagged LGM response, the record of aeolian activity at the Carter Section correlates with other paleoenvironmental records from unglaciated Siberia and Alaska. Overall, rapid shifts in geomorphology, soils, vegetation, and permafrost portray an ice-age landscape where, in contrast to the Holocene, environmental change was chronic and dominated by aeolian processes.

DOI: 10.1016/j.quascirev.2018.01.002

2019025237 Zhang, Hui (University of Helsinki, Department of Environmental Sciences, Helsinki, Finland); Piilo, Sanna R.; Amesbury, Matthew J.; Charman, Dan J.; Gallego-Sala, Angela V. and Valiranta, Minna M. The role of climate change in regulating Arctic permafrost peatland hydrological and vegetation change over the last millennium: Quaternary Science Reviews, 182, p. 121-130, illus. incl. 1 table, sketch map, 87 ref., February 15, 2018.

Climate warming has inevitable impacts on the vegetation and hydrological dynamics of high-latitude permafrost peatlands. These impacts in turn determine the role of these peatlands in the global biogeochemical cycle. Here, we used six active layer peat cores from four permafrost peatlands in Northeast European Russia and Finnish Lapland to investigate permafrost peatland dynamics over the last millennium. Testate amoeba and plant macrofossils were used as proxies for hydrological and vegetation changes. Our results show that during the Medieval Climate Anomaly (MCA), Russian sites experienced short-term permafrost thawing and this induced alternating dry-wet habitat changes eventually followed by desiccation. During the Little Ice Age (LIA) both sites generally supported dry-hummock habitats, at least partly driven by permafrost aggradation. However, proxy data suggest that occasionally, MCA habitat conditions were drier than during the LIA, implying that evapotranspiration may create important additional eco-hydrological feedback mechanisms under warm conditions. All sites showed a tendency towards dry conditions as inferred from both proxies starting either from ca. 100 years ago or in the past few decades after slight permafrost thawing, suggesting that recent warming has stimulated surface desiccation rather than deeper permafrost thawing. This study shows links between two important controls over hydrology and vegetation changes in high-latitude peatlands: direct temperature-induced surface layer response and deeper permafrost layer-related dynamics. These data provide important backgrounds for predictions of Arctic permafrost peatlands and related feedback mechanisms. Our results highlight the importance of increased evapotranspiration and thus provide an additional perspective to understanding of peatland-climate feedback mechanisms.

DOI: 10.1016/j.quascirev.2018.01.003

2019033616 Olichwer, Tomasz (University of Wroclaw, Institute of Geological Sciences, Wroclaw, Poland) and Tarka, Robert. Thermal and mineral springs of southern Spitsbergen: Polish Polar Research, 39(3), p. 331-348, illus. incl. 5 tables, geol. sketch map, 42 ref., 2018. Based on Publisher-supplied data.

In the southern Spitsbergen area, thermal and mineral waters are primarily associated with subpermafrost deep circulation, being mixed with shallow circulation and glacial waters. Four thermal springs, located in the region of Stormbukta (Sorkappland), were studied and analyzed. In the thermal waters, the main cation is sodium, while the main anions are chloride and bicarbonate. The temperatures of the mineral and thermal waters range from 3.4 to 15.1°C. The pH values are between 7.43 and 8.41. The total dissolved solids (TDS) content of the geothermal waters is in the range of 346-4031 mg/l and the Olsok thermal spring has the highest TDS values. Based on the variation in physicochemical characteristics, two thermal water types were distinguished in the study area. The first type is associated with thermal waters originating from deep circulation waters. The second type is associated with the thermal and mineral waters originating from the mixture of subpermafrost hot brines with glacial waters.

DOI: 10.24425/118750

2019030333 Lin, Jeen-Shang (U.S. Department of Energy, National Energy Technology Laboratory, Morgantown, WV); Seol, Yongkoo and Choi, Jeong Hoon. Geomechanical modeling of hydrate-bearing sediments during dissociation under shear: International Journal for Numerical and Analytical Methods in Geomechanics, 41(14), p. 1523-1538, illus. incl. 1 table, 27 ref., October 10, 2017.

Methane hydrate-bearing sediments exist throughout the world in continental margins and in Arctic permafrost. Hydrates are ice-like compounds when dissociate due to temperature rise or reduction in fluid pressure, release gas. Because of the mechanical property changes caused by dissociation in which the loads supported by the hydrates are transferred to soil grains, these sediments may become unstable. To quantify the risk of ground instability triggered by dissociation, which may happen during operation to extract methane gas or from climate changes, a reliable predictive model is indispensable. Even though many models have been proposed, a detailed validation of the ability to model dissociation impact is still needed. This study investigated the adequacy of an spatially mobilized plane constitutive model and a modeling framework using laboratory-induced dissociation tests under shear from literature. Using laboratory-imposed temperature and pressure changes and the resulting hydrate saturation changes as input, this study was able to capture the geomechanical responses and determine the stability state of methane hydrate-bearing sediments as observed. Copyright Copyright 2017 John Wiley & Sons, Ltd.

DOI: 10.1002/nag.2695

2019027868 Perov, Veniamin (Moscow State University, Moscow, Russian Federation); Chernomorets, Sergey; Budarina, Olga; Savernyuk, Elena and Leontyeva, Tatiana. Debris flow hazards for mountain regions of Russia; regional features and key events: in Natural hazards and risk research in Russia; historical roots, current approaches and future challenges (Fuchs, Sven, editor; et al.), Natural Hazards, 88(1, Suppl.), p. 199-235, illus. incl. 3 tables, 118 ref., August 2017.

The total area of debris flow territories of the Russian Federation accounts for about 10% of the area of the country. The highest debris flow activity areas located in Kamchatka-Kuril, North Caucasus and Baikal debris flow provinces. The largest debris flow events connected with volcano eruptions. Maximum volume of debris flow deposits per one event reached 500 ´ 10⁶ m³ (lahar formed during the eruption of Bezymyanny volcano in Kamchatka in 1956). In the mountains of the Greater Caucasus, the maximum volume of transported debris material reached 3 ´ 10⁶ m³; the largest debris flows here had glacial reasons. In the Baikal debris flow province, the highest debris flow activity located in the ridges of the Baikal rift zone (the East Sayan Mountains, the Khamar-Daban Ridge and the ridges of the Stanovoye Highland). Spatial features of debris flow processes within the territory of Russia are analyzed, and the map of Debris Flow Hazard in Russia is presented. We classified the debris flow hazard areas into 2 zones, 6 regions and 15 provinces. Warm and cold zones are distinguished. The warm zone covers mountainous areas within the southern part of Russia with temperate climate; rain-induced debris flows are predominant there. The cold zone includes mountainous areas with subarctic and arctic climate; they are characterized by a short warm period, the occurrence of permafrost, as well as the predominance of slush flows. Debris flow events are described for each province. We collected a list of remarkable debris flow events with some parameters of their magnitude and impact. Due to climate change, the characteristics of debris flows will change in the future. Availability of maps and information from previous events will allow to analyze the new cases of debris flows. Copyright 2017 Springer Science+Business Media B.V. and Springer Science+Business Media Dordrecht

DOI: 10.1007/s11069-017-2841-3

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2019031743 Kublik, Kristina (Geological Survey of Canada, Calgary, AB, Canada) and Grasby, Stephen E. Controls on perennial spring temperature and discharge in high latitude region with thick permafrost [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 160-12, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

At 81°11.4'N, the Ice River spring is the most northern perennial spring in the world. Located within the polar desert of the Canadian High Arctic (average precipitation 75.5 mm/yr; average air temperature -19.7 °C), discharge rates vary from ~110 L/s up to ~520 L/s. Since 2011, continuous temperature measurements show perennial discharge (above zero temperatures) with seasonal variation between 6-9°C, despite being in a region with a low geothermal gradient (25°C/km) and thick permafrost (>400 m). Where recognized, other High Arctic springs have low discharge rates (<10 L/s) and are linked to unusual geologic features, like recently active volcanic centers (Spitsbergen) or hypersaline brines caused by fluid flow along salt diapirs that inhibit freezing (Expedition Fiord on Axel Heiberg Island). By comparison, Ice River is unique because it has relatively fresh water and high flow rates in a cool geothermal setting. We report on controls on this unique spring system and factors that influence the annual temperature profile and discharge. Results provide key insight into cold region hydrogeological processes with applicability to polar regions as well as potential groundwater discharge process on Mars.

2019033440 Molnia, Bruce F. (U. S. Geological Survey, Reston, VA); Angeli, Kim M. and Dilles, Shawn J. Using global fiducial program imagery to better understand and manage the geology and hydrology of public lands [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 128-8, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

Since 1994, the Global Fiducials Program (GFP) has systematically collected imagery from more than 500 environmentally sensitive 'Fiducial Sites' to better understand Earth's environmental processes, variations, and changes on annual to decadal scales. The result is a library of imagery time-series, collected at the highest resolution possible, that systematically documents many behaviors of Earth's surface. Initial GFP site selections were made by Federal and academic scientists based on each site's unique history, susceptibility, or environmental value. Collection strategies were carefully defined for each site with specific repeat intervals and image characteristics to maximize information extraction capabilities. About 40% of GFP sites are within the US, with more than 135 located on public lands. In 2008, the GFP's focus was expanded to also include the unrestricted release of many Fiducial imagery time series, with intended audiences being the public, decision makers, scientists, educators, and the media. Public release provides unequivocal documentation of Earth's rapidly changing character and unrestricted access to the imagery. Five categories of GFP sites exist: 1) Geologic Processes; 2) Ocean and Hydrologic Processes; 3) Ice and Snow Dynamics; 4) Land Use / Land Cover; and 5) Atmospheric & Meteorological Processes. At least 80% of GFP sites are geologic or hydrologic process related. Since 2008, more than 10,000 one-meter resolution images from more than 140 GFP sites have been released. This consistency of imagery parameters and acquisition histories enhances user ability to understand Earth's dynamic processes and characterize long-term trends. Individual time series focus on: volcano and earthquake impacts; landslide behavior; fluvial processes; land-use and land-cover change; Arctic sea ice dynamics; temperate glacier behavior; mid-continent wetland change; barrier island response to hurricanes; coastline evolution; wildland fire recovery; invasive species impacts; permafrost melt; Long-Term Ecological Resource (LTER) site processes; and many other topics. Metadata supported, orthorectified imagery can be freely downloaded from the USGS, making them ideal for use in Earth Science education and GIS projects. For additional information go to: URL: http://gfl.usgs.gov.

2019033448 Moore, Myles T. (Ohio State University, School of Earth Sciences, Columbus, OH); Phillips, Stephen C.; Cook, Ann; Sawyer, Derek E.; Lary, Brent A.; Wulsin, Gus and Darrah, Thomas H. Noble gas and hydrocarbon geochemical composition of fluids associated with gas hydrate formation in cores from Gulf of Mexico Green Canyon, Block GC955 [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 129-4, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

Methane hydrates hosted in continental slope and permafrost sediments constitute a large and important hydrocarbon reservoir globally (~1015 m³). More work is needed to determine the genetic source(s) (i.e., biogenic, thermogenic, mixed) of hydrocarbon gases, the hydrocarbon source rocks, the rates of clathrate formation, and residence time of natural gases in these hydrate systems. Here, we examine gases released from hydrate in two pressurized cores extracted from coarse silt/sand reservoirs ~430 m below the seafloor within the GC955 block of the Green Canyon area in the Gulf of Mexico to resolve the genetic source of natural gas within hydrates and the residence times of natural gas in this area. Previous industry work has inferred the genetic source of natural gases from this area using analyses of hydrocarbon molecular (C₁/C₂₊) and stable isotopic composition of gases (e.g., 2D¹³C-CH4, d²H-CH₄) and water (e.g., d²H-H₂O, d¹⁸O-H₂O), and trace elements. Because these parameters can be affected by mixing, migration, microbial activity, and oxidation, we integrate measurements of noble gases to better constrain the genetic source of hydrocarbons. Preliminary noble gas and hydrocarbon molecular data indicates at least two end-members including a) a nearly pure biogenic end-member with low ⁴He and high C₁/C₂₊ (>10,000) and b) an apparently mixed end-member consisting of moderate ⁴He and intermediate C₁/C₂₊ ranging from 800-3,000. As part of this work, we developed and validated an improved method for sample collection during core depressurization that dramatically reduced atmospheric contamination by >90%. This reduction in atmospheric contamination improves residence time model estimates in this study. Our preliminary noble gas measurements and residence time models suggest unexpectedly young residence times ranging from ~50,000 to 300,000 kyr precluding significant contributions from the long-range migration of "older" thermogenic gas from deeper formations. In general, we do observe a general trend of higher apparent ages in the mixed genetic end-member.

2019031751 Muskett, Reginald Reed (University of Alaska at Fairbanks, Geophysical Institute, Fairbanks, AK). The importance of L-frequency SAR volume scattering on lowland tundra in periglacial and permafrost terrains [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 161-7, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

Geodetic methods to measure centimeter to millimeter-scale changes using aircraft- and spacecraft deployed Synthetic Aperture RADAR cannot ignore volume scattering. Backscatter and coherence at L-frequency and others possess both surface and volumetric scattering. On lowland tundra underlain by permafrost volume scattering dominants the RADAR backscatter coherence. Measurement of the L-frequency penetration depth for evaluation of mass change (loss and transport) through permafrost thaw-degradation with erosion is necessary. Data from the NASA Ice, Cloud, and land Elevation Satellite Geoscience Laser Altimeter System (ICESat GLAS), JAXA Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture RADAR (ALOS PALSAR), aircraft-deployed NASA L-band UAVSAR, the Polar Geospatial Center Arctic DEM, the USGS IfSAR DEM and in-situ measurements with observations are employed. Collocation of ICESat GLAS exact-repeat profiles for elevation change (surface scattering) indicates PALSAR InSAR Line-Of-Sight changes are due to volume scattering. UAVSAR L-frequency Full Polarimetry Cross-Pole HHVV (polarization rotation) confirms the dominance of volume scattering on lowland tundra (RADAR-soft target) whereas surface scattering (HHHH or VVVV, no rotation) dominates on river channel deposits, rock outcrops and metal objects (RADAR-hard targets). Quantifying polarization rotation and the L-frequency penetration depth on lowland tundra are challenges for a new field validation experiment.

2019031738 O'Connor, Michael T. (University of Texas at Austin, Jackson School of Geosciences, Austin, TX); Nicholaides, Kindra D.; Cardenas, Bayani; Neilson, Bethany T.; Jan, Ahmad; Coon, Ethan T. and Kling, George W. Impact of a depth-variable organic mat on thaw and groundwater flow in continuous permafrost [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 160-7, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

Global climate change is driving rapid increases in arctic temperatures and the thawing of shallow permafrost. The amount of anticipated permafrost thaw has uncertainty because of the limited observations of hydraulic and thermal properties of arctic soils. This is especially true in the 'organic mat' that tends to overlie continuous permafrost in the arctic. However, few studies consider how the depth-variability of hydraulic and thermal properties observed in the organic mat could affect how the arctic active layer thaws and laterally transmits groundwater. Here we present high-spatial-density measurements of organic mat hydraulic and thermal properties, as well as model simulations of groundwater flow and freeze-thaw informed by these measurements. Our measurements of water retention, thermal conductivity, organic matter content, porosity, and permeability across multiple watersheds with continuous permafrost illustrate that soil hydraulic and thermal properties vary predictably due to spatial factors such as depth, glacial age, location along a topographic transect, and microtopographic relief. Furthermore, simulations of freeze-thaw and groundwater flow indicate that the observed variability can exert a strong control on active layer thaw and groundwater fluxes. These findings can be used to inform landscape-scale Land Surface Models designed to predict changes in heat, water, and carbon fluxes in arctic watersheds due to increased thaw.

2019033473 Stewart, Alexander K. (Saint Lawrence University, Department of Geology, Canton, NY); Hubbard, Trent D.; Heinrich, Catherine; Eifert, Helen and Leech, Maria. Landscape instability, permafrost and remote infrastructure corridors; dendrogeomorphology using black spruce, Alaska [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 131-6, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.

Alaska's infrastructure corridors are some of the more remote in North America; providing access to critical resources. Many corridors were developed quickly and with limited planning and understanding of cold-regions engineering in geologically complex terrains with widespread permafrost. This results in unique climate-driven maintenance requirements with a projected need of an additional $6.1 billion for normal wear-and-tear costs until 2030 (Larsen et al., 2008). Supporting the Alaskan Department of Transportation and Public Facilities, we evaluated the dendrogeomorphic response of black spruce (Picea mariana) to reveal landscape change along important infrastructure corridors in three sites across Alaska-Northway Junction, Tonsina Hill, and Treasure Creek. At each site, 60 samples from 30 visibly tilted trees were collected, digitized, and quality checked with disturbance years recorded. At Northway Junction along the Alaska Highway in east-central Alaska, there was a site-wide, rapid onset of reaction wood in 1989. Widespread tilting of trees on a retrogressive mass movement, likely a response to thawing permafrost conditions, necessitated an expensive road realignment. At the Tonsina Hill site along the Richardson Highway south of Glennallen, rapid onset of reaction wood began in 1978 and is likely associated with permafrost degradation due to road refurbishment and increased heavy-equipment traffic from the emplacement of the Trans-Alaska Pipeline. At the Treasure Creek site near Fairbanks, remote-sensing and geophysical data indicate land instability in the area, but the reaction wood signal is weak and monotonous from 1950 to the present; this likely represents characteristic tree instability above permafrost. Because each site is situated atop permafrost, unstable ground is expected under certain conditions, which may exacerbate the relatively quiescent process of permafrost thaw. As Alaska continues to modernize in concert with record population growth, efforts to recognize, mitigate, and/or prevent permafrost-thaw-induced landscape changes have become a focus for infrastructure projects. Improved evaluation of infrastructure siting and smarter technologies could help minimize the effects of permafrost thaw on human concerns.

2019028360 Gonzalez, Pablo J. (University of Liverpool, Department of Earth, Ocean and Ecological Sciences, Liverpool, United Kingdom); Zhang, Yu and Samsonov, Sergey. Quantitative morphological description of pingos (permafrost hills) using high-resolution DEMs from UAV and satellite photogrammetry [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-18481, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.

Permafrost dynamics, related to ice aggradation and thawing, are effective climatic indicators. Pingos (conical ice-cored hills) concentrate large amounts of ice near the surface and, hence can be sensitive to environmental changes. Thus, the dynamics of pingos can be used to monitor the effects of climate change over many regions in the Arctic. To use pingos for environmental monitoring, we need to quantify the relationship of pingos morphology with its origin and permafrost conditions, and to monitor pingo dynamics (growth, stability or collapse) effectively. Arctic permafrost ice-landforms and pingos are characterized with small reliefs. Particularly, pingo elevations are usually less than 40 m, with an average of 4.8 m. Current topographic databases are of sufficient quality to identify many pingos, but are completely inadequate to quantitatively measure the morphology of the vast majority of pingos, which prevent from a rigorous morphometric classification and monitoring. In this work, we present a quantitative morphological description of pingos located in the Tuktoyaktuk Coastal Plain area, Northwest Territories, Canada. During the summer of 2017, we collected relevant very-high-resolution topographic data using UAVs drones, and satellite tri-stereo optical photogrammetric data from the Pleaides satellite constellation. We compare and validate our results with the newly available ArcticDEM [URL: https://www.pgc.umn.edu/data/arcticdem/]. The quantitative relationships derived from this very-high-resolution topographic dataset will allow to numerically described pingo morphologies, and contribute to establish rigorously its origin and dynamic processes, with the overall aim to fully exploit its potential as climate indicators. Acknowledgements: The financial support of the NERC Arctic Office under the UK-Canada Arctic Partnership 2017 Bursaries Programme and Mr. Daniel Tucker (BSc Geophysics, University of Liverpool) processed UAV DEMs in the framework of a final year degree project. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-18481-1.pdf

2019028584 Ogneva, Olga (Lomonosov Moscow State University, Soil Science, Moscow, Russian Federation) and Matyshak, George. Permafrost peatlands soils under the climate change impact; the alteration of hydrological conditions and cryogenic processes [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-820, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.

Permafrost Peatlands (PP) cover 70% of arctic region, and PP soils store enormous amount of organic carbon (C)--about 15-30% of world's soil stock, that makes PP incredibly important to the global climate system. Cryogenic processes, such as freeze-thaw cycles (FTCs) and cryoturbations play a key role in the development and maintenance of PP soils and landscapes. Nowadays PP are subjected to climate change which leads to permafrost thawing, and therefore one of the potential critical ways of PP landscapes evolution is water flooding of territory. Thus, the aim of the study was to estimate the effect of freeze-thaw cycles and cryoturbations on organic C of PP soils in case of flooding development. The PP soils were studied in the northwest Siberia in forest-tundra transition zone of discontinuous permafrost (Nadym region, N65°19', E72°53'). The increase of annual temperature in the last 20 years is noted for the region and promotes thawing of permafrost. PP soil cover is represented by a complex of Turbic Cryosol and Cryic Histosols. Peat soil profiles were divided into horizons due to decomposition degree (from 15 to 55-60%), age (from 1000 to 5700 yrs.) and botanical composition. The effects of water content, FTCs and cryoturbations on basal respiration, microbial biomass C (Cmic), and dissolved organic carbon (DOC) contents were studied under laboratory conditions (+4 C) by model experiment. To study effect of water content on soil samples, they were incubated at a range of WHC--from 50 (natural, field water content) to 100% during 5 days. Later, samples were subjected to 10 FTCs (3 days each) at the temperatures of -10 C and +4 C. For the half of samples cryoturbations after every FTC were provided. CO₂ efflux from soil samples subjected to flooding after FTCs was in 1.3 time higher than from the samples under field water content (2,3 and 1,8 C-CO₂ g-1 h-1) and in 1.2 times higher compared to cryoturbated samples. Cmic was not affected by flooding, however cryoturbations increased Cmic in 1.3 times compared to not cryoturbated samples (from 1180 to 1515 mkg g-1). DOC content raised from 965 to 1390 mg kg-1 with the highest value found in flooded cryoturbated samples. Thus, FTCs in case of water flooding increase decomposition of organic matter and peat mineralization. Cryoturbations, in turn, promote peat decomposition due to increasing physical disintegration of organic matter, which increase DOC release from polymeric organic matter composition. This additional DOC efflux promotes microbial biomass growth, however, does not intensify microbial mineralization of peat soils. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-820.pdf

2019028308 Siewert, Matthias B. (Umea University, Department of Ecology and Environmental Science, Sweden); Bouchard, Frédéric; Deshpande, Bethany; Fritz, Michael; Malenfant-Lepage, Julie; Nieuwendam, Alexandre; Paquette, Michel; Rudy, Ashley; Sansoulet, Julie; Sjoberg, Ylva; Veillette, Audrey; Weege, Stefanie; Harbor, Jon and Habeck, J. Otto. Frozen-ground cartoons; an international collaboration between artists and permafrost scientists [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-17051, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.

Permafrost is a hot-topic in climate research, but apart from people living in cold region communities and the scientific community, people know very little about what permafrost is, how we study it and what is happening to it under a warming climate. This project was started almost three years ago by young researchers from Europe and Canada to communicate knowledge and science about an underground phenomenon that keeps showing up in the news headlines. Two artists: Noemie Ross (Canada) and Heta Naas (Finland) created 22 pages of first class outreach material with the input from scientists. Frozen-Ground cartoons are a set of beautiful, artistic, humoristic, and pedagogic comics that aim to explain the consequences of climate change in permafrost regions. They address how climate change and thawing permafrost impacts northern communities, infrastructure, wildlife and greenhouse gas emissions. The printed comics also include a glossary about permafrost. The target audience is kids, youth, parents and teachers who want to learn more about the cold North. Printed comics are now being distributed to school kids, the general public and scientist at various events in Europe and North America. The comics are also available as a free download on the project webpage: URL: https://www.frozengroundcartoon.com and printed copies will be handed out at the poster. The project will now enter its second phase and some of the goals include: to distribute the comics as wide as possible, to translate the comics to local languages and to evaluate the effectiveness for science communication in collaboration with schools and pedagogic experts. The second phase will also see a series of augmented reality material to interact with the comics. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-17051-1.pdf

2019028318 Vivero, Sebastián (University of Lausanne, Institute of Earth Surface Dynamics (IDYST), Lausanne, Switzerland) and Lambiel, Christophe. The potential of UAV technology for monitoring rock glacier kinematics; examples from the Western Swiss Alps [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-16966, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.

Active rock glaciers are unique geomorphological landforms resulting from the creep of mountain permafrost, with superficial rates of movement ranging from few cm a^-1 to few m a^-1. They correspond to aggregations of debris and ice with tongue-shape or lobate form. Regular monitoring of active rock glaciers can be achieved by different means, such as repeated terrestrial geodetic surveys, laser scanning, time-lapse cameras or UAV flights. Repeated UAV surveys can bring new insights about the rock glacier surface changes and current destabilisation phases. Due to the very-high spatial resolution obtained by UAV systems, small rock sizes (i.e. tens of cm) can be tracked, and further detailed analysis can be exploited, such as the rotational movements of rock groups and compression patterns. However, studies that combine an assessment of the quality and accuracy based on concomitant in situ measurements remain unusual. In this case, the validation of remote sensing measurements remains troublesome due to logistical constrains caused by steep slopes over unstable terrain and high surface velocities. To overcome this, we provide the first results after two years of terrestrial geodetic and UAV surveys from slow and fast rock glaciers in the Valais Alps, Switzerland. We focus on the UAV survey design and the Structure from Motion (SfM) workflow used to process and obtain very-high resolution datasets, such as cloud points, Digital Elevation Models (DEM) and orthophotomosaics. Common processing practices, including imagery orthorectification, co-registration and feature tracking algorithms are performed to derive rock glacier surface displacements, which are extensively validated using ground information from terrestrial geodetic surveys. Preliminary, comparisons between coincident terrestrial geodetic surveys and UAV-derived velocities revealed a good agreement, underlining the potential to study rock glacier kinematics completely from UAV surveys. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]

URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-16966.pdf

2019028979 Hilger, P. (Geological Survey of Norway, Norway); Hermanns, R. L.; Gosse, J. C. and Etzelmüller, B. Evaluation of rock slope failures and rockslides in steep permafrost slopes using ¹⁰Be- and ³⁶Cl-dating [abstr.]: in Third Nordic workshop on Cosmogenic nuclide techniques; celebrating 30 years of counting cosmogenic atoms (Blomdin, Robin, editor; et al.), Nordic Workshop on Cosmogenic Nuclide Techniques, 3, p. 8-9, illus., 8 ref., 2016. Meeting: Third Nordic workshop on Cosmogenic nuclide techniques; celebrating 30 years of counting cosmogenic atoms, June 8-10, 2016, Stockholm, Sweden.

URL: http://www.skb.com/publication/2483898/Nordic+workshop.pdf

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