June 2021 Monthly Permafrost Alert (PMA) Program

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

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

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

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2021043126 Slaymaker, O. (University of British Columbia, Department of Geography, Vancouver, BC, Canada); Spencer, T. and Embleton-Hamann, C. Recasting geomorphology as a landscape science: Geomorphology, 384, Article no. 107723, July 1, 2021. Based on Publisher-supplied data.

There is a common acceptance that the Anthropocene epoch is characterized by the increasing dominance of human activity as a driver of global terrestrial change. Geomorphology, with its historical roots in geology and geography, would seem to be ideally positioned as a geoscience to tackle the well documented, rapidly degrading health of that environment. However, the word "geomorphology" is problematic outside the academy in a way that "landscape" is not. A more explicit identification of geomorphology as a landscape science would encourage engagement by geomorphologists in one of the most urgent environmental questions of our time. If humanity is indeed the most important driver of environmental change, we propose that geomorphologists need to engage more seriously with the cognate landscape sciences, such as landscape architecture, anthropology and political ecology. In particular, there are landscapes that are more threatened than others and critical zones in landscapes that must be protected and enhanced with greater care than others. We argue that recasting geomorphology as not only a geoscience but also a landscape science would highlight issues of human well-being at different spatio-temporal scales and we illustrate this in three case studies from our respective countries: UK, Canada and Austria. As traditional geoscientists, we are not used to thinking of coastal flooding, permafrost degradation and snow depletion as centrally important to our science. But as landscape scientists the inclusion of these and all other components of the cryosphere's interaction with human wellbeing is entirely logical and the distinction between systemic and cumulative environmental responses provides a key to unravelling the variable contributions of local actors, managers and decision makers to environmental degradation. Decision making at zonal, regional and local scales are integral to the way in which geomorphic systems function. This argument clearly has wider application. It is up to geomorphology, acting as a landscape science, to provide the underpinning principles that identify landscape-changing actions as being unsustainable and in providing better-informed future pathways away from such actions.

DOI: 10.1016/j.geomorph.2021.107723

2021041941 Yang Yuzhong (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Laboratory of Frozen Soil Engineering, Lanzhou, China); Wu Qingbai; Liu, Fengjing and in Huijun. Spatial-temporal trends of hydrological transitions in thermokarst lakes on northeast Qinghai-Tibet Plateau based on stable isotopes: Journal of Hydrology, 597, Paper no. 126314, illus. incl. 1 table, sketch map, 79 ref., June 2021.

Regarded as the water towers of numerous large rivers in Asia, the Source Area of Yellow River (SAYR) on Northeast Qinghai-Tibet Plateau (QTP) contains substantial thermokarst lakes, which have exerted significant roles on the regional hydrology and water resources under permafrost degradation. To address the potential impact of climate- and permafrost-induced changes in surface hydrological processes in the SAYR, the hydrological transitions and water balance of thermokarst lakes were characterized on large scales during three years using stable isotope method. Spatial and seasonal deviations in hydrological processes of thermokarst lakes were remarkable. Calculations of evaporation-to-inflow (E/I) ratios based on an isotope-mass balance model revealed substantial evaporation for all thermokarst lakes during June due to the control of climate conditions and limited input water. Substantial feeds from summer/fall rain and permafrost meltwater resulted in lower evaporation and positive water balance of lakes during July, August, September, and October. Based on the relationship between lake-specific input water isotope compositions (dI) and annual average isotope value of precipitation (dP), the recharge patterns of thermokarst lakes in the SAYR were classified: supra-permafrost water/rainfall-dominated lakes were mainly concentrated during June and October regardless of spatial divergences, and summer precipitation / permafrost thaw-dominated lakes are popular during July and August. Qualitatively, seasonal diversities in the water balance of thermokarst lakes are combinatively controlled by air temperature, precipitation regimes, permafrost degradation in the SAYR. Lastly, the future hydrological trajectories of thermokarst lakes are expected under climatic warming and permafrost degradation. This study serves as an important contribution for understanding future hydrological changes and allocation of water resources on the QTP, as well as an indication of permafrost degradation under climate warming.

DOI: 10.1016/j.jhydrol.2021.126314

2021040277 Gonzalez Moguel, Regina (McGill University, Geotop Research Centre, Earth and Planetary Sciences, Montreal, QC, Canada); Bass, Adrian M.; Garnett, Mark H.; Pilote, Martin; Keenan, Benjamin; Matveev, Alex and Douglas, Peter M. J. Radiocarbon data reveal contrasting sources for carbon fractions in thermokarst lakes and rivers of Eastern Canada (Nunavik, Quebec): Journal of Geophysical Research: Biogeosciences, 126(4), Article e2020JG005938, illus., 66 ref., April 2021.

Greenhouse gas emissions from permafrost organic carbon decomposition in lakes and rivers can accelerate global warming. We used radiocarbon (14C) measurements to determine the predominant sources of dissolved organic carbon (DOC), particulate organic carbon (POC), dissolved inorganic carbon (DIC), and methane (CH4) in five thermokarst lakes and three rivers in an area of widespread permafrost degradation in Northern Quebec to assess contributions from thawing permafrost and other old carbon (fixed before CE 1950) reservoirs. We compared emission pathways (dissolved gas and ebullition), seasons (summer and winter), and surface soil type (mineral and peat soils). Modern carbon (fixed after CE 1950) was the dominant source of DOC, DIC, and CH4 of non-peatland aquatic systems, while POC and sediment carbon were predominantly fixed in the last millennia. In the peatland systems, modern and permafrost carbon were important sources of DOC, lake DIC, lake ebullition CO2, and lake dissolved CH4. In contrast, POC, lake ebullition CH4, and river DIC were dominated by millennial-old carbon. In winter, the 14C age of DOC, DIC, and POC in the peatland lakes increased, but the 14C age of dissolved CH4 did not change. Our results point to a clearly older overall carbon source for ebullition CH4 relative to dissolved CH4 in the peatland lakes but not the non-peatland lakes. The younger ages of dissolved CH4 and DIC relative to DOC and POC in all lakes suggest that recent primary productivity strongly influences the large total lake CH4 and CO2 emissions in this area, as diffusion fluxes greatly exceed ebullition fluxes. Abstract Copyright (2021), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020JG005938

2021040166 Chen, Liangzhi (University of Helsinki, Department of Geosciences and Geography, Helsinki, Finland); Aalto, Juha and Luoto, Miska. Decadal changes in soil and atmosphere temperature differences linked with environment shifts over northern Eurasia: Journal of Geophysical Research: Earth Surface, 126(3), Article e2020JF005865, illus. incl. 2 tables, sketch maps, 79 ref., March 2021.

The difference between soil and air temperatures (DT) in a specified time is dependent on meteorological conditions, properties of soil and land covers. Understanding DT is critical in assessing land-atmosphere thermal interactions in changing environment. However, systematic knowledge of interannual variations and responses of DT to the environmental changes (e.g., snow cover and soil moisture) at decadal scales remain limited. Here, variations of the mean annual air and soil temperatures, and DT were investigated at 217 sites in northern Eurasia during 1981-2015. It is found that changes in the mean annual air and soil temperatures were inconsistent as the average increase in soil temperature was generally less than that of air. The relationships between trends in soil and air temperatures were significant in the upper ground (0.2 and 0.8 m) over the seasonal frost region but insignificant in the permafrost regions and deeper ground. During the period, widespread changes in DT occurred and closely responded to the environmental changes, but the relationships varied with soil depth. Among the tested factors, trends in snow cover thickness dominantly control trends in DT, followed by trends in snow cover duration and solar radiation. Both linear and nonlinear analyses indicate enhanced relationships between trends in snow depth and DT as depth increases. This study provides the first view of decadal trends in DT and conjunctions with the environmental changes during 1981-2015 over northern Eurasia. The findings are relevant to quantify land-atmosphere thermal interactions given impacts of future environmental changes. Abstract Copyright (2021). The Authors.

DOI: 10.1029/2020JF005865

2021040167 Kang, Seung-Goo (Korea Polar Research Institute, Division of Earth Sciences, Incheon, South Korea); Jin, Young Keun; Jang, Ugeun; Duchesne, Mathieu J.; Shin, Changsoo; Kim, Sookwan; Riedel, Michael; Dallimore, Scott R.; Paull, Charles K.; Choi, Yeonjin and Hong, Jong Kuk. Imaging the P-wave velocity structure of Arctic subsea permafrost using laplace-domain full-waveform inversion: Journal of Geophysical Research: Earth Surface, 126(3), Article e2020JF005941, illus. incl. sketch maps, 31 ref., March 2021. Part of a special issue entitled The Arctic; an AGU joint special collection.

Climate change in the Arctic has recently become a major scientific issue, and detailed information on the degradation of subsea permafrost on continental shelves in the Arctic is critical for understanding the major cause and effects of global warming, especially the release of greenhouse gases. The subsea permafrost at shallow depths beneath the Arctic continental shelves has significantly higher P-wave velocities than the surrounding sediments. The distribution of subsea permafrost on Arctic continental shelves has been studied since the 1970s using seismic refraction methods. With seismic refraction data, the seismic velocity and the depth of the upper boundary of subsea permafrost can be determined. However, it is difficult to identify the lower boundary and the internal shape of permafrost. Here, we present two-dimensional P-wave velocity models of the continental shelf in the Beaufort Sea by applying the Laplace-domain full-waveform inversion method to acquired multichannel seismic reflection data. With the inverted P-wave velocity model, we identify anomalous high seismic velocities that originated from the subsea permafrost. Information on the two-dimensional distribution of subsea permafrost on the Arctic continental shelf area, including the upper and lower bounds of subsea permafrost, are presented. Also, the two-dimensional P-wave velocity model allows us to estimate the thawing pattern and the shape of subsea permafrost structures. Our proposed P-wave velocity models were verified by comparison with the previous distribution map of subsea permafrost from seismic refraction analyses, geothermal modeling, and well-log data. Abstract Copyright (2021). Her Majesty the Queen in Right of Canada. Reproduced with the permission of the Minister of Natural Resources.

DOI: 10.1029/2020JF005941

2021040187 Rangel, R. C. (University of Wyoming, Department of Geology and Geophysics, Laramie, WY); Parsekian, A. D.; Farquharson, L. M.; Jones, B. M.; Ohara, N.; Creighton, A. L.; Gaglioti, B. V.; Kanevskiy, M.; Breen, A. L.; Bergstedt, H.; Romanovsky, V. E. and Hinkel, K. M. Geophysical observations of taliks below drained lake basins on the Arctic Coastal Plain of Alaska: Journal of Geophysical Research: Solid Earth, 126(3), Article e2020JB020889, illus. incl. 3 tables, 96 ref., March 2021.

Lakes and drained lake basins (DLBs) together cover up to ~80% of the western Arctic Coastal Plain of Alaska. The formation and drainage of lakes in this continuous permafrost region drive spatial and temporal landscape dynamics. Postdrainage processes including vegetation succession and permafrost aggradation have implications for hydrology, carbon cycling, and landscape evolution. Here, we used surface nuclear magnetic resonance (NMR) and transient electromagnetic (TEM) measurements in conjunction with thermal modeling to investigate permafrost aggradation beneath eight DLBs on the western Arctic Coastal Plain of Alaska. We also surveyed two primary surface sites that served as nonlake affected control sites. Approximate timing of lake drainage was estimated based on historical aerial imagery. We interpreted the presence of taliks based on either unfrozen water estimated with surface NMR and/or TEM resistivities in DLBs compared to measurements on primary surface sites and borehole resistivity logs. Our results show evidence of taliks below several DLBs that drained before and after 1949 (oldest imagery). We observed depths to the top of taliks between 9 and 45 m. Thermal modeling and geophysical observations agree about the presence and extent of taliks at sites that drained after 1949. Lake drainage events will likely become more frequent in the future due to climate change and our modeling results suggest that warmer and wetter conditions will limit permafrost aggradation in DLBs. Our observations provide useful information to predict future evolution of permafrost in DLBs and its implications for the water and carbon cycles in the Arctic. Abstract Copyright (2021), . The Authors.

DOI: 10.1029/2020JB020889

2021041953 Laurion, Isabelle (Institut National de la Recherche Scientifique, Center for Northern Studies, Quebec, QC, Canada); Massicotte, Philippe; Mazoyer, Flora; Negandhi, Karita and Mladenov, Natalie. Weak mineralization despite strong processing of dissolved organic matter in eastern Arctic tundra ponds: in Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change (Hernes, Peter J., editor; et al.), Limnology and Oceanography, 66(S1), p. S47-S63, illus. incl. 4 tables, 80 ref., February 2021.

Permafrost thawing mobilizes large quantities of organic carbon that was sequestered in Arctic regions over the last glacial cycle. Processes involved in the oxidation of this carbon need to be further assessed to estimate the fraction to be released into the atmosphere. Shallow tundra ponds are sites of active carbon turnover on the landscape and significant sources of greenhouse gases. Dissolved organic matter (DOM) leached from thawing peat into these ponds is exposed to sunlight, with the potential to accelerate its mineralization directly into CO2 or through the production of more labile molecules. We tested the catalytic effect of sunlight on DOM mineralization in tundra ponds formed on organic-rich polygonal landscapes originating from syngenetic permafrost, including a pond exposed to active permafrost erosion. Microbial decay rates, measured as the loss of chromophoric DOM, were similar to photodecay rates (1%-3% d-1). Groups of fluorescing molecules were formed through microbial transformation or lost through photolysis at differing rates among studied ponds, with the erosive trough pond presenting a unique response suggesting the involvement of soil microbes. Despite the stimulation of microbial growth under sunlight and the dynamic response of DOM optical properties, the loss of dissolved organic carbon was not significant under any treatment. This suggests that microbial and photochemical mineralization of DOM was slow and potentially substrate-limited during the dry period when ponds were sampled. The static nature of tundra ponds, with their long water retention time, may thus constrain hot moments when water moves and transports carbon on the landscape. Abstract Copyright (2020), Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11634

2021041955 Levenstein, Brianna (University of New Brunswick, Department of Biology, Fredericton, NB, Canada); Lento, Jennifer and Culp, Joseph. Effects of prolonged sedimentation from permafrost degradation on macroinvertebrate drift in Arctic streams: in Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change (Hernes, Peter J., editor; et al.), Limnology and Oceanography, 66(S1), p. S157-S168, illus. incl. 2 tables, sketch map, 67 ref., February 2021.

Retrogressive thaw slumps are areas of unstable degraded permafrost that often drain into nearby watersheds, leading to increased sediment loads and changes in water quality. Thaw slumps are prevalent across the Arctic, including western Canada, Alaska, and Russia, and high-altitude areas of western China. Over the past several decades, increased temperatures and precipitation in the Arctic have led to increases in the size and frequency of thaw slumps. Our study explored the effects of prolonged sedimentation from thaw slumps in the Peel Plateau, NWT, Canada on benthic macroinvertebrate drift, an important biological function of stream ecosystems. Though sedimentation is known to initiate a catastrophic drift response, studies have generally not considered the drift response to ongoing, long-term perturbation. Drift densities and sediment loads were measured using drift nets and sediment traps at paired sites upstream and downstream of thaw slumps. We compared drift densities and sediment loads between sites and examined how drift differed over a fine-sediment gradient. The amount of suspended and settling fine sediments increased significantly at downstream sites. Drift densities decreased at downstream sites; however, when drift was corrected for benthic abundance at each site, there was an increase in proportional drift density associated with increased fine sediments. These results indicate that prolonged impacts from thaw slumps result in lower macroinvertebrate abundance and higher proportional drift relative to undisturbed sites. Ultimately, increased sediment loads from thaw slumps represent a chronic stressor that will continue to prevent recovery of macroinvertebrate communities at impacted sites until these features stabilize. Abstract Copyright (2020), The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11657

2021041954 Preskienis, Vilmantas (Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Quebec, QC, Canada); Laurion, Isabelle; Bouchard, Frédéric; Douglas, Peter M. J.; Billett, Michael F.; Fortier, Daniel and Xu, Xiaomei. Seasonal patterns in greenhouse gas emissions from lakes and ponds in a High Arctic polygonal landscape: in Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change (Hernes, Peter J., editor; et al.), Limnology and Oceanography, 66(S1), p. S117-S141, illus. incl. 6 tables, sketch map, 97 ref., February 2021.

Lakes and ponds can be hotspots for CO2 and CH4 emissions, but Arctic studies remain scarce. Here we present diffusive and ebullition fluxes collected over several years from 30 ponds and 4 lakes formed on an organic-rich polygonal tundra landscape. Water body morphology strongly affects the mixing regime-and thus the seasonal patterns in gas emissions-with ice-out and autumnal turnover periods identified as hot moments in most cases. The studied thermokarst lake maintained relatively high ebullition rates of millennia-old CH4 (up to 3405 14C YBP). Larger and deeper kettle lakes maintained low fluxes of both gases (century to millennium-old), slowly turning into a CO2 sink over the summer. During winter, lakes accumulated CO2, which was emitted during the ice-out period. Coalescent polygonal ponds, influenced by photosynthesizing benthic mats, were continuous CO2 sinks, yet important CH4 emitters (modern carbon). The highest fluxes were recorded from ice-wedge trough ponds (up to 96 mmol CO2 equivalent m-2 d-1). However, despite clear signs of permafrost carbon inputs via active shore erosion, these sheltered ponds emitted modern to century-old greenhouse gases. As the ice-free period lengthens, scenarios of warmer and wetter conditions could favor both the production of CO2 and CH4 from thawing permafrost carbon, and CH4 production from recently fixed carbon through an atmospheric CO2-to-CH4 shunt at sites in which primary production is stimulated. This must be carefully considered at the landscape scale, recognizing that older carbon stocks can be mineralized efficiently in specific locations, such as in thermokarst lakes. Abstract Copyright (2021), Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11660

2021041956 Rocher-Ros, Gerard (Umea University, Department of Ecology and Environmental Science, Abisko, Sweden); Harms, Tamara K.; Sponseller, Ryan A.; Vaisanen, Maria; Morth, Carl-Magnus and Giesler, Reiner. Metabolism overrides photo-oxidation in CO2 dynamics of Arctic permafrost streams: in Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change (Hernes, Peter J., editor; et al.), Limnology and Oceanography, 66(S1), p. S169-S181, illus. incl. 2 tables, 74 ref., February 2021.

Global warming is enhancing the mobilization of organic carbon (C) from Arctic soils into streams, where it can be mineralized to CO2 and released to the atmosphere. Abiotic photo-oxidation might drive C mineralization, but this process has not been quantitatively integrated with biological processes that also influence CO2 dynamics in aquatic ecosystems. We measured CO2 concentrations and the isotopic composition of dissolved inorganic C (d13CDIC) at diel resolution in two Arctic streams, and coupled this with whole-system metabolism estimates to assess the effect of biotic and abiotic processes on stream C dynamics. CO2 concentrations consistently decreased from night to day, a pattern counter to the hypothesis that photo-oxidation is the dominant source of CO2. Instead, the observed decrease in CO2 during daytime was explained by photosynthetic rates, which were strongly correlated with diurnal changes in d13CDIC values. However, on days when modeled photosynthetic rates were near zero, there was still a significant diel change in d13CDIC values, suggesting that metabolic estimates are partly masked by O2 consumption from photo-oxidation. Our results suggest that 6-12 mmol CO2-C m-2 d-1 may be generated from photo-oxidation, a range that corresponds well to previous laboratory measurements. Moreover, ecosystem respiration rates were 10 times greater than published photo-oxidation rates for these Arctic streams, and accounted for 33-80% of total CO2 evasion. Our results suggest that metabolic activity is the dominant process for CO2 production in Arctic streams. Thus, future aquatic CO2 emissions may depend on how biotic processes respond to the ongoing environmental change. Abstract Copyright (2020), The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11564

2021041957 Zabelina, Svetlana A. (Russian Academy of Science, N. Laverov Federal Center for Integrated Arctic Research, Arkhangelsk, Russian Federation); Shirokova, Liudmila S.; Klimov, Sergey I.; Chupakov, Artem V.; Lim, Artem G.; Polishchuk, Yuri M.; Polishchuk, Vladimir Y.; Bogdanov, Alexander N.; Muratov, Ildar N.; Guerin, Frederic; Karlsson, Jan and Pokrovsky, Oleg S. Carbon emission from thermokarst lakes in NE European tundra: in Biogeochemistry and ecology across Arctic aquatic ecosystems in the face of change (Hernes, Peter J., editor; et al.), Limnology and Oceanography, 66(S1), p. S216-S230, illus. incl. 1 table, geol. sketch map, 94 ref., February 2021.

Emission of greenhouse gases (GHGs) from inland waters is recognized as highly important and an understudied part of the terrestrial carbon (C) biogeochemical cycle. These emissions are still poorly quantified in subarctic regions that contain vast amounts of surface C in permafrost peatlands. This is especially true in NE European peatlands, located within sporadic to discontinuous permafrost zones which are highly vulnerable to thaw. Initial measurements of C emissions from lentic waters of the Bolshezemelskaya Tundra (BZT; 200,000 km2) demonstrated sizable CO2 and CH4 concentrations and fluxes to the atmosphere in 98 depressions, thaw ponds, and thermokarst lakes ranging from 0.5´106 to 5´106 m2 in size. CO2 fluxes decreased by an order of magnitude as waterbody size increased by > 3 orders of magnitude while CH4 fluxes showed large variability unrelated to lake size. By using a combination of Landsat-8 and GeoEye-1 images, we determined lakes cover 4% of BZT and thus calculated overall C emissions from lentic waters to be 3.8±0.65 Tg C yr-1 (99% C-CO2, 1% C-CH4), which is two times higher than the lateral riverine export. Large lakes dominated GHG emissions whereas small thaw ponds had a minor contribution to overall water surface area and GHG emissions. These data suggest that, if permafrost thaw in NE Europe results in disappearance of large thermokarst lakes and formation of new small thaw ponds and depressions, GHG emissions from lentic waters in this region may decrease. Abstract Copyright (2020), The Authors. Limnology and Oceanography published by Wiley Periodicals LLC. on behalf of Association for the Sciences of Limnology and Oceanography.

DOI: 10.1002/lno.11560

2021039951 Klinge, Michael (University of Göttingen, Institute of Geography, Gottingen, Germany); Schlütz, Frank; Zander, Anja; Hülle, Daniela; Batkhishig, Ochirbat and Lehmkuhl, Frank. Late Pleistocene lake level, glaciation and climate change in the Mongolian Altai deduced from sedimentological and palynological archives: Quaternary Research, 99, p. 168-189, illus. incl. 3 tables, geol. sketch maps, 107 ref., January 2021.

Glacial and lacustrine sediments from the Mongolian Altai provide paleoclimatic information for the late Pleistocene in Mongolia, for which only a few sufficiently studied archives exist. Glacial stages referred to global cooling events are reported for the last glacial maximum (27-21 ka) and the late glacial period (18-16 ka). Sedimentary archives from the first part of the last glacial period are infrequent. We present proxy data for this period from two different archives (88-63 and 57-30 ka). Due to the limitation of effective moisture, an increase of precipitation is discussed as one trigger for glacier development in the cold-arid regions of central Asia. Our pollen analysis from periods of high paleolake levels in small catchments indicate that the vegetation was sparse and of dry desert type between 42-29 and 17-11 ka. This apparent contradiction between high lake levels and dry landscape conditions, the latter supported by intensified eolian processes, points to lower temperatures and cooler conditions causing reduced evaporation to be the main trigger for the high lake levels during glacier advances. Rising temperatures that cause melting of glacier and permafrost ice and geomorphological processes play a role in paleolake conditions. Interpreting lake-level changes as regional or global paleoclimate signals requires detailed investigation of geomorphological settings and mountain-basin relationships.

DOI: 10.1017/qua.2020.67

2021039958 Murchie, Tyler J. (McMaster University, McMaster Ancient DNA Centre, Hamilton, ON, Canada); Kuch, Melanie; Duggan, Ana T.; Ledger, Marissa L.; Roche, Kévin; Klunk, Jennifer; Karpinski, Emil; Hackenberger, Dirk; Sadoway, Tara; MacPhee, Ross; Froese, Duane and Poinar, Hendrik. Optimizing extraction and targeted capture of ancient environmental DNA for reconstructing past environments using the PalaeoChip Arctic-1.0 bait-set: Quaternary Research, 99, p. 305-328, illus. incl. charts, 1 table, sketch map, 110 ref., January 2021.

Sedimentary ancient DNA (sedaDNA) has been established as a viable biomolecular proxy for tracking taxon presence through time in a local environment, even in the total absence of surviving tissues. SedaDNA is thought to survive through mineral binding, facilitating long-term biomolecular preservation, but also challenging DNA isolation. Two common limitations in sedaDNA extraction are the carryover of other substances that inhibit enzymatic reactions, and the loss of authentic sedaDNA when attempting to reduce inhibitor co-elution. Here, we present a sedaDNA extraction procedure paired with targeted enrichment intended to maximize DNA recovery. Our procedure exhibits a 7.7-19.3x increase in on-target plant and animal sedaDNA compared to a commercial soil extraction kit, and a 1.2-59.9x increase compared to a metabarcoding approach. To illustrate the effectiveness of our cold spin extraction and PalaeoChip capture enrichment approach, we present results for the diachronic presence of plants and animals from Yukon permafrost samples dating to the Pleistocene-Holocene transition, and discuss new potential evidence for the late survival (~9700 years ago) of mammoth (Mammuthus sp.) and horse (Equus sp.) in the Klondike region of Yukon, Canada. This enrichment approach translates to a more taxonomically diverse dataset and improved on-target sequencing.

DOI: 10.1017/qua.2020.59

2021039766 Mu Cuicui (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China); Abbott, Benjamin W.; Norris, Adam J.; Mu Mei; Fan Chenyan; Chen Xu; Jia Lin; Yang Ruimin; Zhang Tingjun; Wang Kang; Peng Xiaoqing; Wu Qingbai; Guggenberger, Georg and Wu Xiaodong. The status and stability of permafrost carbon on the Tibetan Plateau: Earth-Science Reviews, 211, Article no. 103433, illus. incl. sketch maps, 3 tables, block diag., 235 ref., December 2020.

Permafrost regions at high latitudes and altitudes store about half of the Earth's soil organic carbon (SOC). These areas are also some of the most intensely affected by anthropogenic climate change. The Tibetan Plateau or Third Pole (TP) contains most of the world's alpine permafrost, yet there remains substantial uncertainty about the role of this region in regulating the overall permafrost climate feedback. Here, we review the thermal and biogeochemical status of permafrost on the TP, with a particular focus on SOC stocks and vulnerability in the face of climate warming. SOC storage in permafrost-affected regions of the TP is estimated to be 19.0±6.6 Pg to a depth of 2 m. The distribution of this SOC on the TP is strongly associated with active layer thickness, soil moisture, soil texture, topographic position, and thickness of weathered parent material. The mean temperature sensitivity coefficient (Q10) of SOC decomposition is 9.2±7.1 across different soil depths and under different land-cover types, suggesting that carbon on the TP is very vulnerable to climate change. While the TP ecosystem currently is a net carbon sink, climate change will likely increase ecosystem respiration and may weaken or reverse the sink function of this region in the future. Although the TP has less ground ice than high latitude permafrost regions, the rugged topography makes it vulnerable to widespread permafrost collapse and thermo-erosion (thermokarst), which accelerates carbon losses. To reduce uncertainty about SOC quantities and sensitivity to warming, future studies are needed that explain variation in Q10 (e.g. based on SOC source or depositional position) and quantify the role of nutrient availability in regulating SOC dynamics and ecosystem recovery following disturbance. Additionally, as for the high latitude permafrost region, soil moisture and thermokarst formation remain major challenges to predicting the permafrost climate feedback on the TP. We present a conceptual model for of greenhouse gas release from the TP and outline the empirical observations and modeling approaches needed to test it.

DOI: 10.1016/j.earscirev.2020.103433

2021042791 Pesch, Charles (Aalborg University, Department of the Built Environment, Aalborg, Denmark); Lamande, Mathieu; de Jonge, Lis Wollesen; Norgaard, Trine; Greve, Mogens Humlekrog and Moldrup, Per. Compression and rebound characteristics of agricultural sandy pasture soils from South Greenland: Geoderma, 380, Article no. 114608, December 15, 2020. Based on Publisher-supplied data.

The reduction of permafrost areas and a prolonged vegetation period, both due to the ongoing climate change, open up new possibilities for agricultural activities in the circumpolar region. Presently, not much is known about the physical and functional properties of subarctic agricultural soils, making it challenging to evaluate soil impacts from increased agricultural activity. This study aims at assessing the mechanical properties of sandy Greenlandic pasture soils regarding a potential future land-use change. The compression curves of 210 undisturbed soil core samples of three pasture fields in South Greenland and, as comparison, four intensively cultivated agricultural fields in Denmark were generated by uniaxial confined compression tests (UCCT). Four soil mechanical properties were determined: the precompression stress (spc) as a measure of soil strength, the compression index (Cc) as a measure of compressibility, the swelling index (Cs) as a measure of resilience to compaction and the rebound (De) after a relaxation time of 60 s as a measure of short-time recovery from compaction. The Greenlandic pasture soils exhibited significantly higher spc than the Danish cultivated soils despite their significantly lower initial bulk density, rb. The Cc negatively correlated with rb, and the Greenlandic soils showed higher Cc values than the Danish soils. The Cs showed a reciprocal correlation with rb and, partly due to lower rb of the Greenlandic soils, higher Cs than the Danish soils. The South Greenlandic sandy pasture soils showed compression and rebound characteristics on level with Danish loamy cultivated soils, likely due to a high content of particulate organic matter (non-degraded organic matter, including grass root-mat residues).

DOI: 10.1016/j.geoderma.2020.114608

2021042982 Pain, Andrea J. (University of Florida, Department of Geological Sciences, Gainesville, FL); Martin, Jonathan B.; Martin, Ellen E.; Rahman, Shaily and Ackermann, Philip. Differences in the quantity and quality of organic matter exported from Greenlandic glacial and deglaciated watersheds: Global Biogeochemical Cycles, 34(10), Article e2020GB006614, illus. incl. 5 tables, sketch map, 87 ref., October 2020.

Riverine input of terrestrial dissolved organic matter (DOM) is an important component of the marine carbon cycle and drives net carbon dioxide production in coastal zones. DOM exports to the Arctic Ocean are likely to increase due to melting of permafrost and the Greenland Ice Sheet, but the quantity and quality of DOM exports from deglaciated watersheds in Greenland, as well as expected changes with future melting, are unknown. We compare DOM quantity and quality in Greenland over the melt seasons of 2017-2018 between two rivers directly draining the Greenland Ice Sheet (meltwater rivers) and four streams draining deglaciated catchments that are disconnected from the ice (nonglacial streams). We couple these data with discharge records to compare dissolved organic carbon (DOC) exports. DOM sources and quality differ significantly between watershed types: fluorescence characteristics and organic molar C:N ratios suggest that DOM from deglaciated watersheds is derived from terrestrial vegetation and soil organic matter, while that in glacial watersheds contains greater proportions of algal and/or freshly produced biomass and may be more reactive. DOC specific yield is similar for nonglacial streams (0.1-1.2 Mg/km2/year) compared to a glacial meltwater river (0.2-1.1 Mg/km2/year), despite orders of magnitude differences in instantaneous discharge. Upscaling based on land cover leads to an estimate of total DOC contributions from Greenland between 0.2 and 0.5 Tg/year, much of which is derived from deglaciated watersheds. These results suggest that future warming and ice retreat may increase DOC fluxes from Greenland with consequences for the Arctic carbon cycle. Abstract Copyright (2020), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020GB006614

2021040028 Villa, Jorge A. (University of Louisiana at Lafayette, School of Geosciences, Lafayette, LA). Functional representation of biological components in methane-cycling processes in wetlands improves modeling predictions: Journal of Geophysical Research: Biogeosciences, 125(10), Article e2020JG005794, illus., 30 ref., October 2020.

Wetlands are important natural sources of methane. However, methane predictions are unconstrained due in part to simplified representations in biogeochemical models of complex interactions between biological components and biophysical drivers. Chang et al. (2019, URL: https://doi.org/10.1029/2019JG005355) demonstrate how mechanistic descriptions of processes mediated by biological components and their drivers help improve methane prediction in the thawing permafrost peatlands, where biological components are shifting as a response to current climate change. These findings underscore the need for accounting for the different methanogenic pathways in biogeochemical models to predict methane cycling under a changing climate scenario. This comment presents some implications of considering the methanogenic pathways when simulating different wetland ecosystems and discusses the relevance of including other processes mediated by biological components in the methane cycle in models. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2020JG005794

2021039970 Nyland, Kelsey E. (Michigan State University, Department of Geography, Environment, and Spatial Sciences, East Lansing, MI); Nelson, Frederick E. and Figueiredo, Paula M. Cosmogenic 10Be and 36Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland: Quaternary Research, 97, p. 157-166, illus. incl. 3 tables, geol. sketch map, 70 ref., September 2020.

Cryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments. Geomorphologists have debated for more than a century over processes involved in the formation of these elevated, step-like, bedrock features. Presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the Yukon-Tanana Upland (YTU) in Alaska, part of unglaciated eastern Beringia, obtained from terrestrial cosmogenic nuclides (TCN) in surface boulders. Ages comprise six 10Be TCN ages from two terrace treads near Eagle Summit and six 36 Cl ages from two treads on Mt. Fairplay. Based on these exposure ages, scarps at both locations were last actively eroding from 49 to 22.4 ka. Both locations exhibit time-transgressive development, particularly near scarp-tread junctions. Boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0.11 to 0.56 cm/yr. These numerical exposure ages presented here demonstrate that the cryoplanation terraces in the YTU are diachronous surfaces actively eroding during multiple cold intervals. With these results, hypotheses for cryoplanation terrace formation are discussed and evaluated for the YTU, including those based on geologic structure, nivation, and the influence of permafrost.

DOI: 10.1017/qua.2020.25

2021039312 Quinton, William (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Berg, Aaron; Braverman, Michael; Carpino, Olivia; Chasmer, Laura; Connon, Ryan; Craig, James; Devoie, Élise; Hayashi, Masaki; Haynes, Kristine; Olefeldt, David; Pietroniro, Alain; Rezanezhad, Fereidoun; Schincariol, Robert and Sonnentag, Oliver. A synthesis of three decades of hydrological research at Scotty Creek, NWT, Canada: Hydrology and Earth System Sciences (HESS), 23(4), p. 2015-2039, illus. incl. 1 table, sketch map, 112 ref., 2019.

Scotty Creek, Northwest Territories (NWT), Canada, has been the focus of hydrological research for nearly three decades. Over this period, field and modelling studies have generated new insights into the thermal and physical mechanisms governing the flux and storage of water in the wetland-dominated regions of discontinuous permafrost that characterises much of the Canadian and circumpolar subarctic. Research at Scotty Creek has coincided with a period of unprecedented climate warming, permafrost thaw, and resulting land cover transformations including the expansion of wetland areas and loss of forests. This paper (1) synthesises field and modelling studies at Scotty Creek, (2) highlights the key insights of these studies on the major water flux and storage processes operating within and between the major land cover types, and (3) provides insights into the rate and pattern of the permafrost-thaw-induced land cover change and how such changes will affect the hydrology and water resources of the study region.

DOI: 10.5194/hess-23-2015-2019

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2021041578 Alvarez, Alejandro J. (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Young, Joseph M; Kokelj, Steven V. and Froese, Duane G. Characterization of permafrost cores from the Inuvik-Tuktoyaktuk Corridor [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-12, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Permafrost, or ground that remains below 0°C for two or more years, is the binding agent holding many northern landscapes from collapse. The sensitivity and impacts of climate change on permafrost is primarily related to the nature and amount of ground ice in the host materials that may potentially lose cohesion with thaw, and may develop terrain effects from subsidence, termed thermokarst. The magnitude of thermokarst development is largely a function of the abundance of excess ice, i.e., ice that exceeds the pore space of the host sediments.This study analyzed three ice-rich cores (BH-1, BH-4, and BH-8) recording a variety of depositional environments, along the Inuvik-Tuktoyaktuk Highway, NWT. Cores were analyzed for cryostructures, water isotopes (d18O and d2H) and underwent radiocarbon dating to determine the origin of the sedimentary records and associated ground ice. Ice-rich diamictons are present near the base of the BH-1 and BH-4 cores. These diamictons are fine-grained and have d18O water isotope values of -18 to -20 ppm, with a co-isotope slope less than the local meteoric water line. These values are more enriched than primary glacial diamictons in the area, suggesting these diamicton bodies have been modified by thaw and refrozen with younger Holocene water. A prominent 4 m thick massive ice body is present in BH-1 between the diamicton and the peat's base. Water isotopes from the massive ice body are depleted relative to the values from the rest of the cores and fall on the local meteoric water line, suggesting the preservation of buried ground ice. Core BH-8 contains ice-rich silt and clay near the base overlain by ~4 m of peat. Radiocarbon dates and sedimentary structures indicate a shifting landscape with a local lake from ~11,500 to 9000 years ago, subsequently draining, developing epigenetic permafrost, and transitioning to syngenetic peat in the early Holocene. Collectively, these deposits suggest preservation of a relict permafrost landscape affected by thaw in the early Holocene, followed by subsequent stabilization and permafrost aggradation. Since the distribution and abundance of ground ice is strongly related to the geologic history of permafrost regions, future work will focus on placing these cores into a Quaternary geologic context and allow future trajectories of thermokarst to be identified.

DOI: 10.1130/abs/2020AM-357781

2021041575 Buchanan, Casey Alexander (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Froese, Duane G. and Porter, Trevor J. Stable isotope record development in ground ice along alpine tundra slopes in the Ogilvie Mountains, Yukon Territory [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-9, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Stable isotope (d18O, d2H) signatures of permafrost ground ice provide a proxy for past hydroclimate. This relationship arises from the strong temperature dependence of d18O and d2H in precipitation. Precipitation that infiltrates the active layer - the horizon which undergoes annual thaw in permafrost-affected soils - becomes incorporated into the upper permafrost ice as the surface aggrades. However, mechanisms which potentially modify the original d18O and d2H values of meteoric waters during their residence within the active layer, and during the freezing process, are not well understood. This study investigates how d18O and d2H are modified in the active layer prior to long-term incorporation as ground ice by addressing three questions: 1) how do d18O and d2H in active layer waters vary across topography and hydrological regime, 2) what mechanisms give rise to these variations, and 3) what is the relationship between d18O and d2H values of active layer waters and the upper permafrost aggradational ice? To test these questions, ground ice samples were cored in June 2019, and active layer waters were collected in September 2019 along two catenas within the Ogilvie Mountains, Yukon Territory. The isotopic values of active layer waters and upper permafrost ice co-varied with respect to topographic position, likely arising from compounding influences of evapotranspiration and thawed ground ice waters during downslope migration. Furthermore, although upper permafrost ice (sourced from lower active layer waters) was consistently more enriched than September active layer waters, this enrichment was significantly less than predicted by ideal Rayleigh-style cryofractionation, which is consistent with findings from previous studies. Ultimately, this research improves our understanding of stable isotopic development in pore ice, enhancing their potential as quantitative paleotemperature proxies.

DOI: 10.1130/abs/2020AM-358114

2021041576 Conaway, Christopher H. (U. S. Geological Survey, Menlo Park, CA); Johnson, Cordell; Lorenson, Thomas D.; Turetsky, Merritt R.; Euskirchen, Eugénie S.; Waldrop, Mark P. and Swarzenski, Peter W. Permafrost mapping with ERT in interior Alaska wetlands [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-10, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

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

DOI: 10.1130/abs/2020AM-356219

2021041574 Douglas, Madison (California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA); Lamb, Michael P.; Li, Gen; Rowland, Joel C.; West, A. Joshua; Schwenk, Jon; Piliouras, Anastasia; Kemeny, Preston C.; Chadwick, Austin J. and Fischer, Woodward W. Floodplain architecture and organic carbon storage in discontinuous permafrost [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-8, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Patterns of Arctic river channel migration may change as thawing permafrost destabilizes riverbanks, allowing rivers to mobilize sediment and carbon from permafrost that was previously sequestered far below the ground surface. Therefore, in addition to threatening infrastructure built on permafrost river floodplains, changes to river migration rates may alter downstream fluxes of sediment and carbon to the Arctic Ocean, modulating the carbon cycle and consequently the climate system. In order to quantify floodplain-scale organic carbon (OC) fluxes due to river channel migration, we combined field, remote sensing and chemical measurements from the floodplain of the Koyukuk River, a major meandering tributary of the Yukon that flows through discontinuous permafrost in central Alaska. We mapped geomorphic landforms, floodplain relative depositional ages and riverbank erosion rates from remote sensing imagery to develop the context for soil OC measurements to quantify the OC eroded and deposited by river meandering. We found that near-surface permafrost is located predominantly on older floodplain deposits, while younger river deposits have well-preserved scroll bars and a higher frequency of meander bends translating downstream rather than expanding outwards. Sediment radiocarbon content does not correlate with deposit relative age, and spans the radiocarbon content of woody debris from the same location. By comparing soil OC stocks across different geomorphologic units on the floodplain, we identified oxbow lakes as important OC reservoirs. We also used channel erosion and deposition masks generated from Landsat imagery to calculate that total OC fluxes into and out of the Koyukuk due to bank erosion and bar deposition are balanced over the interval 1978-2018. Our results illustrate how the Koyukuk River governs patterns of permafrost succession as it migrates across its floodplain, and provide a framework for linking geochemical budgets to lateral transport processes across a landscape.

DOI: 10.1130/abs/2020AM-359406

2021041572 Fountain, Andrew G. (Portland State University, Department of Geology, Portland, OR) and Levy, Joseph S. Rapid geomorphic change in an unchanging polar desert, Antarctica [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-6, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

The McMurdo Dry Valleys, Antarctica, is the largest ice-free region on the continent, located along the edge of the western shore of the Ross Sea at about 78°S. It is a polar desert with annual air temperatures of about -20°C and summer air temperatures occasionally warming a few degrees above 0°C. With no rainfall, little snowmelt, and glaciers frozen at their base, the rate of geomorphic change is slow. Indeed, high elevations landscapes are thought to have been largely stable for the past 14 million years. In this context, it was surprising to encounter, in January 2009, a rapidly incising stream in Garwood Valley, one of the McMurdo Dry Valleys. Field inspection showed incision of up to several meters in places and later aerial lidar differencing showed not only deep incisions in the main stream channel but also incisions in tributary channels as part of the geomorphic response. Investigations in the upper elevations of the valley revealed two glacier-dammed lakes, each episodically draining by melt-erosion through the ice-dam formed by the toe of each glacier. Measurements and time-lapse imagery at one ice dam showed the lake draining in a few hours after breakout. We hypothesize that a similar glacier-dammed lake flooding event took place during an unusual warm period in the austral summer of 2001-02. The flood waters thermally eroded a narrow ice-dam between the glacier and valley wall draining the lake to another glacier-dammed lake below, which it too thermally eroded under the toe of that glacier sending the water down valley. The flood waters eroded through the ice-cemented permafrost mantling a layer of massive ice below. This ice was most likely emplaced during the last ice age when the Ross Ice Shelf entered the valley. Subsequent aeolian drift covered the ice, preserving it, when the Ross Ice Shelf withdrew. When the flooding stream waters reached this buried ice, it eroded quickly causing bank collapse in the main channel as well as incision in the tributary streams during the following years as the fluvial system adjusted to the new equilibrium. Calculations of flood volume and rates of incision will be presented. The warm event in 2001/02 thought to have triggered the flood may be unique in the past ~10,000 years as there is no evidence of prior stream incision.

DOI: 10.1130/abs/2020AM-357979

2021041569 Froese, Duane G. (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Porter, Trevor J. and Mahony, Matthew. The MIS 2 ice wedge problem in unglaciated Yukon and the problem of yedoma definitions [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-3, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

The concept of Yedoma is increasingly used to correlate the extensive fine-grained syngenetic sediments that accumulated during Pleistocene cold stages across Beringia. The Russian concept of Yedoma, as presented by Andrei Sher in the 1990s, identifies at least three uses: geomorphic (Yedoma surface), stratigraphic (Yedoma suite) and sedimentologic, referring to the ice-rich silts with large penetrating ice wedges. The latter has largely become the de facto definition for Yedoma, characterizing extensive fine-grained sediments that includes large syngenetic ice wedges that accumulated during Pleistocene cold stages. But this definition, requiring ice wedges to be present, remains problematic as we apply it to the North American context, and in particular to sites of greater relief where sedimentation is affected by hillslope and aspect effects. Late Pleistocene Yedoma deposits in the Klondike area (Yukon) show varying stratigraphic expression because of changes in surface processes coupled to past climate. During the MIS 3 interstadial, large, isotopically depleted (ca. -26 to -28 per mil d18O) syngenetic ice wedges are present within loessal sediments, while the contemporaneous pore ice is typically 2-4 per mil more enriched. The contrast between wedge and pore ice would be expected since ice wedges preferentially sample winter or spring snow melt following thermal contraction cracking in winter, while pore ice is a late season phenomenon in which waters at the base of the active layer are incorporated into the top of permafrost by freeze-back in the fall. However, during the height of the last cold stage, ice wedges are rare in the Klondike record, suggesting a lack of thermal contraction cracking. However, rare, narrow ice wedges have been found dating to MIS 2 and the corresponding isotope data from ice wedges are depleted (ca. -30 to -33 per mil d18O), and these values are similar to contemporaneous pore ice. This creates a paradox- how can pore ice be isotopically similar to wedge ice when they have different seasonalities? We now think that these differing records have underestimated the importance of aspect, and the role of perennial snow banks and ice patches that likely covered these surfaces in proximal slope positions. The presence of snow cover would reduce or inhibit thermal contraction cracking, while the release of that melt through the summer and into the fall, provides a mechanism for the depleted pore ice.

DOI: 10.1130/abs/2020AM-358017

2021042862 Hong, Wei-Li (University of Tromso-Arctic University of Norway, Centre for Arctic Gas Hydrate, Environment and Climate, Tromso, Norway); Lepland, Aivo; Himmler, Tobias; Kim, Ji-Hoon; Chand, Shyam; Sahy, Diana; Solomon, Evan A.; Rae, James; Martma, Tonu; Nam, Seung-Il and Knies, Jochen Manfred. Discharge of meteoric water in the eastern Norwegian Sea since the last glacial period [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 102-3, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Submarine groundwater discharge could impact the transport of critical solutes to the ocean. However, its driver(s), significance over geological time scales, and geographical coverage are poorly understood. We characterize a submarine groundwater seep from the continental slope off northern Norway where substantial amount of meteoric water was detected. We reconstruct the seepage history from textural relationships and U-Th geochronology of authigenic minerals. We demonstrate how glacial-interglacial dynamics have promoted submarine groundwater circulation more than 100 km offshore and result in high fluxes of critical solutes to the ocean. Such cryosphere-hydrosphere coupling is likely common in the circum-Arctic implying that future decay of glaciers and permafrost in a warming Arctic is expected to attenuate such a coupled process and thus decreases the export of critical solutes.

DOI: 10.1130/abs/2020AM-356406

2021041573 Kennedy, Kristen (Yukon Geological Survey, Whitehorse, YT, Canada); Calmels, Fabrice; Lipovsky, Panya and Roy, Louis-Philippe. Community permafrost mapping in Yukon; understanding community needs and data limitations in a changing North [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-7, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Northern communities are facing unprecedented challenges to adequately predict and adapt to landscape evolution resulting from rapid climate change. In one of the most impacted regions of the world, geomorphic processes driven by factors such as precipitation and air temperature are occurring with increased intensity, frequency, and unpredictability. These changes result in considerable cost and safety concerns for local governments and regulators. In Yukon, thaw of widespread permafrost terrain is related to higher incidences of ground subsidence, thermal erosion, and mass wasting. While much of the academic research focuses on global and regional characterizations of permafrost thaw susceptibility and distribution, local governments are struggling to adequately predict and plan for infrastructure development, maintenance, and public safety priorities. In an effort to develop adequate and cost-effective planning and adaptation tools, researchers at Yukon University and Yukon Geological Survey initiated a hazard mapping program in 2010 in partnership with 8 communities across the Territory. The resulting community-focused maps better define connections between surficial materials and ground ice, and account for the repercussions of climate change on geomorphic processes and associated hazards. Ten years after the project began, we continue to be unable to comprehensively predict ground ice distributions, relationships between permafrost and groundwater, and regionally relevant thaw trajectories. Examples from this project highlight the diverse needs of northern societies and the requirement for tailored approaches for specific applications.

DOI: 10.1130/abs/2020AM-358742

2021039882 Miner, Kimberley (Jet Propulsion Laboratory, Pasadena, CA); Miller, Charles; Fernandez-Prieto, Diego; Turetsky, Merritt R. and Bartsch, Annett. Biogeochemical hazards of a thawing Arctic [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 237-12, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Arctic permafrost degradation is introducing biogeochemical hazards into the local and global environment. Known paleo-ecological hazards that may cause uncertain ecosystem impacts in the present include methanogenic bacteria, viruses, bacteria, and pathogens. These emergent species join a variety of modern biogeochemical hazards in the Arctic, including banned pesticides like DDT, mercury, and nuclear materials previously sequestered in permafrost. The preservation of frozen permafrost is critical to mitigating a punctuated release of these compounds into the local environment, however, adaptation and remediation may be more prudent in a warming world. This talk will identify the types of hazards presented by permafrost degradation, the pathways of exposure, and the socio-environmental impacts of chemical mobilization through the environment.

DOI: 10.1130/abs/2020AM-356331

2021039834 Purtill, Matthew (State University of New York at Fredonia, Department of Geology and Environmental Sciences, Fredonia, NY) and Tytka, Gillian. Possible evidence of relict polygonal ground features in the Finger Lakes region of New York; a pilot study using Google Earth Pro [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 231-7, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Relict polygonal ground (RPG) are soil-geomorphic features that formed during past cold-climate, deep frost or permafrost, conditions. In the Great Lakes region, RPGs are increasingly recognized on deglaciated landscapes of Indiana, Ohio, Michigan, and Wisconsin. In contrast, RPGs are not reported for New York state despite other evidence of periglacial conditions during the late Pleistocene. This pilot study used geographic information systems, primarily Google Earth Pro, to review high-resolution aerial images between the years 2005 and 2016 in three New York counties in the Finger Lakes region: Seneca, Schuyler, and Tompkins. This study identified 52 potential RPG clusters across ~31 km2 of primarily agricultural land between N42.3° and N42.8° latitude. This finding confirms the presence of RPGs in New York, north of the LGM margin. Observed RPGs are rounded to curvilinear, dark outlined, interlocking nests of polygons of variable size. RPG visibility varies between image years and ground cover conditions. Direct age control is absent, but RPGs likely formed between 17.5 and 14.7 ka cal yr BP based on radiocarbon dating of the Outer Valley Heads and Mapleton moraines which formed during the Port Bruce and Port Huron Stadials, respectively. A dense concentration of RPGs immediately south of, and largely paralleling, the Inner Valley Heads morainal system dated to 15.8 ka cal yr BP may indicate a temporal association for many of these features. The recovery of Dryas fossils in basal cores of Dumond Lake dating to 12.6 ka cal yr BP, however, potentially suggest a late persistence of permafrost conditions in the region. Expansion of this pilot study is planned in the coming years and will include ground truthing of select RPG targets and continued review of additional counties along a roughly north-south transect across New York.

DOI: 10.1130/abs/2020AM-355834

2021041580 Robert, Zena V. (University of Alaska at Fairbanks, Department of Geosciences, Fairbanks, AK); Mann, Daniel H.; Farquharson, Louise; Romanovsky, Vladimir; Meyer, Franz J. and Maio, Christopher V. The impacts of rapid climate change on mass movements in Denali National Park and Preserve, Alaska [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-14, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

The eastern portion of Denali National Park and Preserve (DENA) is a high-altitude (800 m-1400 m asl) alpine (63°N) environment that is experiencing a new wave of geomorphological destabilization as a result of a warming climate. Hillslopes are becoming unstable as permafrost (perennially frozen ground) thaws, which can then trigger various types of mass movements. Mass movements have the potential to affect the structural integrity of the Denali Park Road, alter the flow of groundwater or river systems, uproot vegetation, and negatively impact the safety of the half a million visitors that the park receives every year. The purpose of this study to understand how mass movements in DENA are affected by different aspects of climate change, such as increased rainfall and rising air and ground temperatures, to determine when and why DENA's landscape experienced periods of instability in the past, and to better understand the potential trajectory of current landscape changes. To establish a timeline of mass movement activity since the early Holocene, we performed lichenometry on relict rockfalls and rock glaciers to determine when the paleo-landscape began to stabilize. Many of the ongoing mass movements in DENA are reactivations of older landslides or rock glaciers that were active in the early Holocene, such as the Mile 35 Slide. The Mile 35 Slide is a polygenetic mass movement that initiated along the Park Road during the summer of 2016. We used a combination of remote sensing, field surveys, and local weather records to establish a four-year timeline of this landslide's movement and how it responded to rapid changes in climate. Observations of the Mile 35 Slide illustrate the important role played by freeze/thaw processes and extreme rainfall events in DENA mass movement initiation and progression. Our lichenometric analysis of rockfalls in DENA reveal earlier episodes of widespread mass movement, the oldest dating to ca. 11,000 yr. BP. This indicates that DENA has experienced several previous episodes of landscape instability in the past, and that cycles of stability/instability are characteristic of this environment. We conclude that ongoing mass movements are occurring on hillslopes that were unstable in the past and that rapid changes in climate are important triggers of mass movements in this alpine environment.

DOI: 10.1130/abs/2020AM-351792

2021041570 Rudy, Ashley C. A (Northwest Territories Geological Survey, Yellowknife, NT, Canada); Kokelj, Steven V.; Lamoureux, Scott F.; Lantz, Trevor; Morse, Peter D. and Gingras-Hill, Tristan. Multi-scale investigations of permafrost landscape change [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-4, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Ice-rich permafrost terrains comprise some of the most rapidly changing landscapes in the world due to the effects of climate-driven permafrost thaw. Thermokarst is the surface manifestation of thaw-driven geomorphic change. It can be expressed as discrete features on thawing slopes such as retrogressive thaw slumps or as contiguous areas where particular surface and subsurface conditions give rise to broad areas of disturbed terrain as in the case of degrading ice-wedge polygons. Present-day patterns of thermokarst are a product of geological, climate and environmental history. The nature and distribution of thermokarst is a critical indicator of subsurface conditions and terrain sensitivity, and a predictor of the trajectories of landscape change. This presentation will highlight thermokarst landscape sensitivity using empirically-driven models and explore geophysical factors driving the alteration of thermokarst systems and how they are represented at different scales. Thermokarst types have been inventoried across northwestern Canada at various spatial scales using a combination of high-resolution satellite imagery and mapping methods. These inventories have been used to develop statistical models (Random Forest) that identified the relationship between the spatial distribution of thermokarst and terrain characteristics (i.e. surficial geology, permafrost condition, slope, aspect, elevation, vegetation), which can then be used to predict landscape scale sensitivity to future thermokarst. The relative importance of terrain variables in the model reflects geomorphic process and provides insight into the controls over thermokarst development. As climate continues to warm, knowledge of the physical factors driving the alteration of thermokarst systems and a regional-scale analysis of thermokarst is necessary to not only assess hazards and inform management of northern infrastructure and heritage assets but to also better understand the trajectories of northern ecosystem change and the cascade of downstream consequences.

DOI: 10.1130/abs/2020AM-359412

2021041567 Walvoord, Michelle A. (U. S. Geological Survey, Denver, CO); Rey, David M.; Minsley, Burke and Ebel, Brian A. Supra-permafrost taliks in thawing landscapes of boreal Alaska, USA [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-1, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Recently, there has been focused attention on the development of supra-permafrost taliks (perennially unfrozen zones in permafrost) that follows active-layer thickening in the sequence of top down permafrost-thaw progression in high latitudes. Talik formation can substantially influence geomorphic, hydrologic, and biogeochemical processes in permafrost landscapes, thus motivating efforts to understand current talik distribution and provide constraints on future evolution under changing climate. Here we present examples of talik formation in contrasting field sites in upland and lowland boreal forest ecoregions in interior Alaska, USA. Sites are located near the broadly mapped transition between continuous and discontinuous permafrost. Multiple lines of geophysical data provide support for enhanced talik development in response to disturbance, including wildfire and ice jam river flooding, superimposed on atmospheric warming. Drawing from results of cryohydrogeologic model simulations, field measurements, and additional analytical assessments, we discuss hydrologic implications for talik development and permafrost thaw acceleration at our contrasted sites. We identify and explore landscape characteristics and initial thermal conditions that control the propensity for talik development. Field investigations show localized examples of rapid talik development that outpace current coarse scale talik projections under the most extreme greenhouse gas emission scenario by ~100 years. Though large-scale extrapolation of localized extremes is not advised, our research raises questions regarding the potential for aggregated localized thaw to evolve toward regional importance as widespread wildfire activity and flooding intensify in the future.

DOI: 10.1130/abs/2020AM-354326

2021041581 Wolfe, Stephen A. (Geological Survey of Canada, Ottawa, ON, Canada) and Morse, Peter D. Sedimentary and physiographic constraints on pingo distribution, Tuktoyaktuk Peninsula region, Northwest Territories, Canada [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-15, 1 ref., October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

The physical basis for the widespread distribution of pingos in the Tuktoyaktuk Peninsula region has long intrigued scientists. Early mapping identified ~1400 of these ice-cored permafrost hills on the modern Mackenzie Delta and Pleistocene deposits to the east, occupying drained lake basins, depressions, and floodplains (Mackay 1962), but was limited by the resolution of monochromatic aerial photographs and precise georeferencing. We developed a comprehensive dataset of pingos in this region using an ArcticDEM basemap and high resolution (1 m or better) colour satellite imagery on ArcGIS Earth and Google Earth platforms. Pingo-like features were identified and those that met both topographic and optical criteria were confirmed as pingos. We mapped nearly 2820 pingo-like features, confirmed over 2350 pingos, and noted about 5% in a state of collapse. Pingos occur in an area of about 18,500 km2 at elevations from 60 m asl to sea level. Only ~5% of the mapped pingos were in the outer delta. According to Mackay (1979), most pingos occur on Pleistocene interglacial sands and silts, veneered with glacial and postglacial sediments. We attribute these pingos to Pleistocene alluvial sediments, specifically the Kidluit Formation distributed by the paleo-Peel and paleo-Porcupine rivers. Pingos are absent on the Caribou Hills and Anderson Plain, and west of Nicholson Point, which provides constraints on the extent of the Kidluit deposits. Pingos are least abundant on the Toker Point Moraine, Kittigazuit Low Hills, and Husky Lakes Pitted Terrain physiographic units, suggesting additional glacial and postglacial controls on pingo distribution. Pingos are most concentrated within the Low Involuted Hills, Kugmallit Plain, and Tununuk Low Hills, where Holocene thermokarst lacustrine basins are most abundant. The georeferenced database improves the geological context for pingos in the Tuktoyaktuk Peninsula region. The catalogue of collapsed forms and other pingo-like forms provides a means to assess associated morphologies, and to assess pingo-like features elsewhere on Earth and Mars.

DOI: 10.1130/abs/2020AM-353180

2021041571 Young, Joseph M. (University of Alberta, Department of Earth and Atmospheric Sciences, Edmonton, AB, Canada); Van der Sluijs, Jurjen; Kokelj, Steven V. and Froese, Duane G. Recent development of deep permafrost landslides (molard-type) in discontinuous permafrost from the central Mackenzie Mountain foothills, Northwest Territories, Canada [abstr.]: in Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Abstracts with Programs - Geological Society of America, 52(6), Abstract no. 209-5, October 2020. Meeting: Geological Society of America, 2020 annual meeting; GSA 2020 connects online, Oct. 26-30, 2020, World Wide Web.

Widespread permafrost warming in hillslope terrain increases the potential for thermokarst mass wasting. These disturbances can damage infrastructure, rapidly degrade aquatic environments, and pose direct and indirect risks to communities. Here, we use repeat satellite imagery to inventory over 280 landslides and retrogressive thaw slumps in the Extensive Discontinuous Permafrost Zone from the central Mackenzie Valley Foothills, NWT. These disturbances have largely initiated in the last 10-15 years and show a close correlation with historic forest fire extents from the 1990s. This association suggests a thermal legacy from fire activity as a primary preconditioning mechanism for these permafrost slope failures. In addition, we complement remote mapping with geological and cryostratigraphic site investigations, and high-resolution UAV imagery. This contribution focuses on three of the largest permafrost landslides in the study area. These three deep-seated landslides collapsed recently (2015-2018), on shallow to moderate slopes in areas of fine-grained diamicts, and range in size from approximately 0.6 km2 to 2.5 km2. Their debris tongues include the presence of meter-scale conical-shaped mounds, termed molards, which indicate the abrupt translocation of frozen blocks of slide material followed by its subsequent thaw into the distinctive mounds. These large-scale failures leave a distinctive geomorphic signature, associated with the molard-type mounds, but also depositing large volumes of material into downstream valleys forming distinct valley-fill deposits with the potential to dam rivers. The increase in these failures suggests an acceleration of this new form in response to climate warming, potentially from thaw at the base of the permafrost table. Further quantification of the parameters and mechanisms regulating the initiation of these landslides will improve our understanding of the severity to which permafrost hillslope landscapes will respond to increasing climatic and environmental stressors.

DOI: 10.1130/abs/2020AM-357935

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