Permafrost Monthly Alerts (PMAs)

2022033229 Kamp, Ulrich (University of Michigan at Dearborn, Dearborn, MI); Walther, Michael and Dashtseren, Avirmed. Mongolia's cryosphere: Geomorphology, 410, Article 108202, August 1, 2022. Based on Publisher-supplied data.

Mongolia's cryosphere is relatively poorly studied; this review sheds light on the research on paleoglaciations, recent glaciers, and permafrost. Historical works mostly added to reconstructions of paleoglaciations and the development of geochronologies that are increasingly based on numerical dating methods including the use of cosmogenic radionuclides. During the Pleistocene, four glaciation centers existed: Altai, Eastern Sayan, Khangai, and Kenthii mountains. Pleistocene glaciations covered an area of between 20,000 and 30,000 km² and occurred partly asynchronously across these mountain systems: the glacier maximum in the Altai, Khangai, and Eastern Sayan occurred during MIS 3, while it occurred during MIS 2 in the Khentii and Gobi Altai. Today, Mongolia's glaciers are restricted to the Altai and generally in recession for the past decades; the total glacial area decreased by 35% from 1990 to 2016, when 627 glaciers covered 334 km². In the Upper Khovd River Basin that includes Tavan Bogd, Mongolia's recent glaciation center, the contribution from meltwater to total runoff decreased by >3% from 2000 to 2016. The Altai glaciers are predicted to undergo sustained mass loss by 2100, with some locations, particularly in the western Altai, losing all their ice. Uncertainties about the occurrence and distribution of permafrost still exist as subtype classifications vary, periglacial conditions might have been interpreted as permafrost, and not all researchers agree on the existence of continuous permafrost within Mongolia. Today, permafrost covers 26% of Mongolia's territory. Undoubtedly, permafrost warming and thawing is widespread, and the ground ice is predicted to disappear in the 21st century. Climate change already left its mark on Mongolia's cryosphere and consequently on many communities. Hence, sustainable approaches are needed in water resources management in the Altai and technical infrastructure maintenance and improvement in permafrost regions.

DOI: 10.1016/j.geomorph.2022.108202

2022030422 Marr, Philipp (University of Vienna, Department of Geography and Regional Research, Vienna, Austria); Winkler, Stefan; Dahl, Svein Olaf and Löffler, Jörg. Age, origin and palaeoclimatic implications of peri- and paraglacial boulder-dominated landforms in Rondane, South Norway: Geomorphology, 408, Article 108251, illus. incl. 4 tables, sketch maps, 126 ref., July 2022.

Boulder-dominated landforms of periglacial, paraglacial and related origin constitute a valuable, but often unexplored source of paleoclimatic and morphodynamic information. The timing of landform development initiation and its subsequent stabilization can be linked to past climatic conditions offering the potential to reconstruct cold climatic periods. In this study, Schmidt-hammer exposure-age dating (SHD) was applied to a variety of boulder-dominated landforms (sorted stripes, blockfield, rock-slope failure, paraglacial alluvial fan) in Rondane, eastern South Norway for the first time. On the basis of old and young control points a regional SHD calibration curve was established and successively utilized for the calculation of surface exposure ages for individual landforms. The chronological investigation of development and stabilization of the respective landforms permitted an assessment of Holocene climate variability in Rondane and its impact on overall landform evolution. Our obtained SHD age estimates ranged from 11.44 ± 1.22 ka (ST-D2) to 4.09 ± 1.51 ka (AF1) showing their inactive and relict character. Most surface exposure ages for sorted stripes clustered between 9.88 ± 1.35 ka and 9.25 ± 1.21 ka, hence indicating stabilization during the late stage of the Erdalen Event or shortly thereafter. It is inferred that the blockfield formed prior to the Last Glacial Maximum, was protected by cold-based ice throughout glaciation and shortly reactivated during the Erdalen Event only to subsequently becoming inactive. The surface exposure age of a rock-slope failure (7.58 ± 0.73 ka) falls into the early phase of the Holocene Thermal Maximum (HTM, ~8.0-5.0 ka). This indicates permafrost degradation and/or increasing hydrological pressure negatively influencing slope stability. The paraglacial alluvial fan with its four subsites yielded ages between 8.73 ± 1.63 ka and 4.09 ± 1.51 ka. The old exposure ages point to fan aggradation following regional deglaciation due to paraglacial processes, whereas the younger ages can be explained by increasing precipitation during the onset neoglaciation at ~4.0 ka. Our results underline the importance of meltwater for the activation of periglacial landforms in a continental climate and indicate that the Erdalen Event and immediately following onset of the HTM had major impact on landscape evolution in Rondane. Our obtained surface exposure ages from boulder-dominated landforms in Rondane give important insights into the local paleoclimatic variability during the Holocene.

DOI: 10.1016/j.geomorph.2022.108251

2022031922 Cheng, Feng (Rice University, Department of Earth, Environmental, and Planetary Sciences, Houston, TX); Lindsey, Nathaniel J.; Sobolevskaia, Valeriia; Dou, Shan; Freifeld, Barry; Wood, Todd; James, Stephanie R.; Wagner, Anna M. and Ajo-Franklin, Jonathan B. Watching the cryosphere thaw; seismic monitoring of permafrost degradation using distributed acoustic sensing during a controlled heating experiment: Geophysical Research Letters, 49(10), Article e2021GL097195, illus. incl. geol. sketch map, 67 ref., May 28, 2022.

Permafrost degradation is rapidly increasing in response to a warming Arctic climate, altering landscapes and damaging critical infrastructure. Solutions for monitoring permafrost thaw dynamics are essential to understand biogeochemical feedbacks as well as to issue warnings for hazardous geotechnical conditions. We investigate the feasibility of permafrost monitoring using permanently installed fiber-optic seismic networks. We conducted a 2-month seismic monitoring campaign during a controlled thaw experiment using a permanent surface orbital vibrator (SOV) and a 2D-array of distributed acoustic sensing (DAS) cables, and observed significant (15%) shear-wave velocity (V_s) reductions and approximately 2 m depression of the permafrost table beneath the heating zone. These observations were validated by time-lapse horizontal-to-vertical spectral ratio (HVSR) analysis from three co-located broadband seismometers. The combination of SOV and DAS provided unique seismic observations for permafrost monitoring at the field scale, as well as a basis for design and development of early warning systems for permafrost thaw. Abstract Copyright (2022), The Authors. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

DOI: 10.1029/2021GL097195

2022033378 Conroy, Nathan A. (Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM); Dann, Julian B.; Newman, Brent D.; Heikoop, Jeffrey M.; Arendt, Carli; Busey, Bob; Wilson, Cathy J. and Wullschleger, Stan D. Chemostatic concentration discharge behaviour observed in a headwater catchment underlain with discontinuous permafrost: Hydrological Processes, 36(5), Article e14591, illus. incl. 2 tables, sketch map, 35 ref., May 2022.

Concentration-discharge dynamics were evaluated in a small (~ 2.25 km²) headwater catchment underlain with discontinuous permafrost on the Seward Peninsula of western Alaska. A large storm, during which 48 mm of rain fell over a 24-h period, enabled the evaluation of solute concentration-discharge response to a sizeable hydrological event, while water stable isotopes enabled an appraisal of the contributions of event water. Under normal catchment conditions, chemostatic behaviour was observed for solutes typically derived from mineral weathering (e.g. calcium, magnesium, sodium and silica). The chemostatic behaviour observed for most solutes under normal catchment conditions indicated that catchment storage and residence times are sufficiently long for many solute generating reactions to approach equilibrium. Following the storm however, most solutes exhibited dilutive and highly variable behaviour. This likely indicated the exceedance of a discharge threshold where chemostatic behaviour could no longer be maintained for most solutes. Dissolved organic carbon and silica were the only solutes monitored to exhibit chemostatic behaviour during all time periods. Abstract Copyright (2022), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.14591

2022033381 Rooney, Erin C. (Oregon State University, Department of Crop and Soil Science, Corvallis, OR); Bailey, Vanessa L.; Patel, Kaizad F.; Possinger, Angela R.; Gallo, Adrian C.; Bergmann, Maya; SanClements, Michael and Lybrand, Rebecca A. The impact of freeze-thaw history on soil carbon response to experimental freeze-thaw cycles: Journal of Geophysical Research: Biogeosciences, 127(5), Article e2022JG006889, illus. incl. 2 tables, 81 ref., May 2022.

Freeze-thaw is a disturbance process in cold regions where permafrost soils are becoming vulnerable to temperature fluctuations above 0°C. Freeze-thaw alters soil physical and biogeochemical properties with implications for carbon persistence and emissions in Arctic landscapes. We examined whether different freeze-thaw histories in two soil systems led to contrasting biogeochemical responses under a laboratory-controlled freeze-thaw incubation. We investigated controls on carbon composition through Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to identify nominal carbon oxidation states and relative abundances of aliphatic-type carbon molecules in both surface and subsurface soils. Soil cores (~60 cm-depth) were sampled from two sites in Alaskan permafrost landscapes with different in situ freeze-thaw characteristics: Healy (>40 freeze-thaw cycles annually) and Toolik (<15 freeze-thaw cycles annually). FT-ICR-MS was coupled with in situ temperature data and soil properties (i.e., soil texture, mineralogy) to assess (a) differences in soil organic matter composition associated with previous freeze-thaw history and (b) sensitivity to experimental freeze-thaw in the extracted cores. Control (freeze-only) samples showed greater carbon oxidation in Healy soils compared with Toolik, even in lower mineral horizons where freeze-thaw history was comparable across both sites. Healy showed the most loss of carbon compounds following experimental freeze-thaw in the lower mineral depths, including a decrease in aliphatics. Toolik soils responded more slowly to freeze-thaw as shown by intermediary carbon oxidation distributed across multiple carbon compound classes. Variations in the response of permafrost carbon chemistry to freeze-thaw is an important factor for predicting changes in soil function as permafrost thaws in high northern latitudes. Abstract Copyright (2022), . The Authors.

DOI: 10.1029/2022JG006889

2022033380 Stuenzi, Simone Maria (Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute, Potsdam, Germany); Kruse, Stefan; Boike, Julia; Herzschuh, Ulrike; Oehme, Alexander; Pestryakova, Luidmila A.; Westermann, Sebastian and Langer, Moritz. Thermohydrological impact of forest disturbances on ecosystem-protected permafrost: Journal of Geophysical Research: Biogeosciences, 127(5), Article e2021JG006630, illus. incl. 5 tables, 100 ref., May 2022. Includes appendices.

Boreal forests cover over half of the global permafrost area and protect underlying permafrost. Boreal forest development, therefore, has an impact on permafrost evolution, especially under a warming climate. Forest disturbances and changing climate conditions cause vegetation shifts and potentially destabilize the carbon stored within the vegetation and permafrost. Disturbed permafrost-forest ecosystems can develop into a dry or swampy bush- or grasslands, shift toward broadleaf- or evergreen needleleaf-dominated forests, or recover to the pre-disturbance state. An increase in the number and intensity of fires, as well as intensified logging activities, could lead to a partial or complete ecosystem and permafrost degradation. We study the impact of forest disturbances (logging, surface, and canopy fires) on the thermal and hydrological permafrost conditions and ecosystem resilience. We use a dynamic multilayer canopy-permafrost model to simulate different scenarios at a study site in eastern Siberia. We implement expected mortality, defoliation, and ground surface changes and analyze the interplay between forest recovery and permafrost. We find that forest loss induces soil drying of up to 44%, leading to lower active layer thicknesses and abrupt or steady decline of a larch forest, depending on disturbance intensity. Only after surface fires, the most common disturbances, inducing low mortality rates, forests can recover and overpass pre-disturbance leaf area index values. We find that the trajectory of larch forests after surface fires is dependent on the precipitation conditions in the years after the disturbance. Dryer years can drastically change the direction of the larch forest development within the studied period. Abstract Copyright (2022), . The Authors.

DOI: 10.1029/2021JG006630

2022031928 Sun Zhe (Nanjing University of Information Science & Technology, Nanjing, China); Zhao Lin; Hu Guojie; Zhou Huayun; Liu Shibo; Qiao Yongping; Du Erji; Zou Defu and Xie Changwei. Numerical simulation of thaw settlement and permafrost changes at three sites along the Qinghai-Tibet engineering corridor in a warming climate: Geophysical Research Letters, 49(10), Article e2021GL097334, illus. incl. 1 table, 32 ref., May 28, 2022.

Thaw settlement caused by permafrost degradation has great impacts on engineering infrastructure, hydrological cycles and ecosystems in recent decades under climate warming. We combined the moving-grid method (Lagrangian method) with the heat conduction equation to develop a new moving-grid permafrost model. Our model takes into account not only the cryostratigraphy of permafrost, but also the thaw settlement. We used the model to simulate the thaw settlement and the permafrost changes at the three sites along the Qinghai-Tibet Engineering Corridor from 1966 to 2018. The monitoring of the ground temperature and the geodetic leveling in situ were used for model validation. The results show that our model can accurately reproduce the observed interannual thaw settlement and ground temperature fields. The risk of thawing settlement in ice-rich permafrost regions in the zero-temperature-gradient stage is high. Abstract Copyright (2022), . American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GL097334

2022030078 Rooney, Erin C. (Oregon State University, Department of Crop and Soil Science, Corvallis, OR); Bailey, Vanessa L.; Patel, Kaizad F.; Dragila, Maria; Battu, Anil K.; Buchko, Alexander C.; Gallo, Adrian C.; Hatten, Jeffery; Possinger, Angela R.; Qafoku, Odeta; Reno, Loren R.; SanClements, Michael; Varga, Tamas and Lybrand, Rebecca A. Soil pore network response to freeze-thaw cycles in permafrost aggregates: Geoderma, 411, Article 115674, illus. incl. sketch map, 62 ref., April 1, 2022.

Climate change in Arctic landscapes may increase freeze-thaw frequency within the active layer as well as newly thawed permafrost. Freeze-thaw is a highly disruptive process that can deform soil pores and alter the architecture of the soil pore network with varied impacts to water transport and retention, redox conditions, and microbial activity. Our objective was to investigate how freeze-thaw cycles impacted the pore network of newly thawed permafrost aggregates to improve understanding of what type of transformations can be expected from warming Arctic landscapes. We measured the impact of freeze-thaw on pore morphology, pore throat diameter distribution, and pore connectivity with X-ray computed tomography (XCT) using six permafrost aggregates with sizes of 2.5 cm³ from a mineral soil horizon (Bw; 28-50 cm depths) in Toolik, Alaska. Freeze-thaw cycles were performed using a laboratory incubation consisting of five freeze-thaw cycles (-10°C to 20°C) over five weeks. Our findings indicated decreasing spatial connectivity of the pore network across all aggregates with higher frequencies of singly connected pores following freeze-thaw. Water-filled pores that were connected to the pore network decreased in volume while the overall connected pore volumetric fraction was not affected. Shifts in the pore throat diameter distribution were mostly observed in pore throats ranges of 100 mm or less with no corresponding changes to the pore shape factor of pore throats. Responses of the pore network to freeze-thaw varied by aggregate, suggesting that initial pore morphology may play a role in driving freeze-thaw response. Our research suggests that freeze-thaw alters the microenvironment of permafrost aggregates during the incipient stage of deformation following permafrost thaw, impacting soil properties and function in Arctic landscapes undergoing transition.

DOI: 10.1016/j.geoderma.2021.115674

2022031518 Li Xiaoying (Northeast Forestry University, College of Forestry, Key Laboratory of Sustainable Forest Ecosystem Management (Ministry of Education), Harbin, China); Jin Huijun; Wang Hongwei; Jin Xiaoying; Bense, Victor F.; Marchenko, Sergey S.; He Ruixia; Huang Yadong and Luo Dongliang. Effects of fire history on thermal regimes of permafrost in the northern Da Xing'anling Mountains, NE China: Geoderma, 410, Article 115670, illus. incl. 4 tables, sketch map, 79 ref., March 15, 2022.

Forest fires potentially result in the irreversible and rapid degradation of permafrost, soil evolution, successions of boreal forests, and consequent development of hazardous periglacial landforms. Two burned-areas of Mangui and Alongshan at the western flank of the northern Da Xing'anling Mountains in Northeast China were chosen to study the effects of forest fires on thermal regimes of near-surface permafrost and the active layer. The study results show risen post-fire ground temperatures with increasing fire severity, and mainly at depths of 0-1.5 m. Moreover, nine years after a severe burn, the depth of evident temperature changes exceeded 6 m, and a warming of 2.7°C at 6 m depth was inferred. Presumably due to the influences of forest fires, the active layer thickness at severely burned sites was 3.8 m compared to 1.2 m at the un-burned site. Soil moisture content and organic-layer and snow-cover thicknesses also play important roles in further complicating the fire impacts on the permafrost environment. These impacting mechanisms and thresholds await more systematic, in-depth, and quantitative studies. Numerical models deem necessary for simulating and predicting the spatiotemporal variations in ground hydrothermal regimes under different fire severity and for evaluating the contributions and thresholds of changes in these important environmental factors (e.g., organic layer and snow cover) for the hydrothermal state of near-surface permafrost and active layer.

DOI: 10.1016/j.geoderma.2021.115670

2022033008 Suhrhoff, Tim Jesper (ETH Zürich, Institute of Geochemistry and Petrology, Department of Earth Sciences, Zurich, Switzerland); Rickli, Jörg; Christl, Marcus; Vologina, Elena G.; Pham, Viet; Belhadj, Moustafa; Sklyarov, Eugene V.; Jeandel, Catherine and Vance, Derek. Source to sink analysis of weathering fluxes in Lake Baikal and its watershed based on riverine fluxes, elemental lake budgets, REE patterns, and radiogenic (Nd, Sr) and ¹⁰Be/⁹Be isotopes: Geochimica et Cosmochimica Acta, 321, p. 133-154, illus. incl. 6 tables, sketch maps, 133 ref., March 15, 2022.

We present a detailed analysis of weathering fluxes at Lake Baikal, the largest lake in the world, using the major element, trace element and isotope geochemistry of major inflowing rivers, the lake itself, and its sediments. Our objective is to assess how lake records could be used to understand river-catchment-scale denudation and weathering processes.Total denudation rates at Lake Baikal, as obtained from meteoric ¹⁰Be/⁹Be, are an order of magnitude lower than the global average, at 16-35 t km^-2 yr^-1. Chemical weathering rates obtained from the riverine dissolved load and discharge are, on the other hand, in the same range as global values, at 6-29 t km^-2 yr^-1. Chemical weathering rates are higher in the north of the catchment than in the south, consistent with higher runoff in the north. In contrast, ¹⁰Be/⁹Be-derived denudation rates are higher in the south. We hypothesize that this pattern of variation may be due to the stabilizing effect of permafrost soils preventing erosion in the north. An inverse model shows that the Selenga River, Lake Baikal's major tributary, has a silicate weathering contribution to riverine dissolved cation fluxes of 42 mol%; this and other characteristics are representative of large rivers globally. Many trace elements have much lower concentrations in the lake than in inflowing rivers (Be (5%), Mn (3%), Fe (0.4%) and REE (1-2%)). We suggest, based on REE patterns and Mn, Fe-depth profiles in the lake, that this removal is the result of pH induced changes in dissolved-adsorbed partitioning at the river-lake interface, and the incorporation of trace elements into authigenic Fe-Mn (oxyhydr)oxide phases forming within the lake. Strontium is isotopically uniform within the lake, demonstrating that the whole lake mixes on a timescale shorter than its residence time (<330 years). Neodymium and Be, in contrast, show isotopic variability between the basins. While the Sr isotope budget of the lake is largely consistent with observed riverine Sr fluxes, an unradiogenic Nd source is needed to explain lake Nd isotope compositions, especially in the Northern Basin. This source appears to derive from old crustal rocks in this part of the catchment and could be hydrothermal, or small rivers that were not sampled here. Similarly, elevated ¹⁰Be/⁹Be ratios in the lake basins relative to the river input imply variable but significant atmospheric inputs of ¹⁰Be into the lake. Overall, this study demonstrates that records of the paleo-chemistry of lakes, and Lake Baikal in particular, hold promise for understanding denudation and weathering on the continents, in ways that are more directly relatable to the environmental conditions of the catchment than is possible with marine records.

DOI: 10.1016/j.gca.2022.01.007

2022035315 Del Vecchio, J. (Pennsylvania State University, Department of Geosciences, University Park, PA); DiBiase, R. A.; Corbett, L. B.; Bierman, P. R.; Caffee, M. W. and Ivory, S. J. Increased erosion rates following the onset of Pleistocene periglaciation at Bear Meadows, Pennsylvania, USA: Geophysical Research Letters, 49(4), Article e2021GL096739, illus. incl. sketch maps, 65 ref., January 16, 2022.

Direct measurements of erosional response to past climate change are scarce, but mid-latitude landscapes can record how shifts between cold and warm periods altered erosion outside glacial margins. To study hillslope responses to periglaciation, we measured bulk geochemistry and cosmogenic ¹⁰Be and ²⁶Al concentrations in colluvium and weathered bedrock in an 18 m regolith core from Bear Meadows, Pennsylvania, ~100 km south of maximum glacial extent. Using core lithology, cosmogenic nuclide concentrations, and regional ¹⁰Be-derived erosion rates, we show the onset of 100-Kyr glacial cycles at the Mid-Pleistocene Transition (1.2-0.7 Ma) instigated multiple periglacial episodes in central Appalachia, increasing erosion rates compared to the relatively warmer Neogene. Our results show the higher efficiency of periglacial versus temperate erosion processes and highlight a pervasive Pleistocene periglacial erosion signal preserved in the ¹⁰Be inventory of surface sediments in central Appalachia, where erosion rates are slow enough to integrate previous cold-climate processes. Abstract Copyright (2022), American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GL096739

2022032816 Wen Amin (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Cryosphere Research Station on the Qinghai-Tibet Plateau, State Key Laboratory of Cryospheric Science, Lanzhou, China); Wu Tonghua; Zhu Xiaofan; Li Ren; Wu Xiaodong; Chen Jie; Qiao Yongping; Ni Jie; Ma Wensi; Li Xiangfei and Shang Chenpeng. Changes in the spatial distribution of Bryophytes on the Qinghai-Tibet Plateau under CMIP6 future projections: Environmental Earth Sciences, 81(1), Article 15, illus. incl. 3 tables, geol. sketch map, 78 ref., January 2022.

Bryophytes play important roles in high altitude-latitude ecosystem owing to their extensive geographical coverage. Particularly, the insulating effect prevent permafrost degradation with the rapidly climate warming on the QTP. However, few studies investigated how Bryophytes will react to environmental change at the global scale. In this study, a maximum entropy (Maxent) model was utilized to predict the potential impact of climate change on the distribution of Bryophytes on the QTP. Predictions were based on the under historical (years of 1970-2000) and future climate scenarios (years of 2041-2060 and 2081-2100) using the average climate data of nine global climate models (GCMs) for shared socio-economic pathways (SSP2-4.5) of CMIP6 and other environmental variables. In addition, the key environmental factors affecting the habitat distribution and range shifts of Bryophytes were examined. The results revealed that Bryophytes occupied an area of approximately 179.97(±0.87)´10⁴ km², 77(±0.44)% of the total areal extent of QTP in the past. Niche suitability of the Bryophytes was dominated by soil moisture, ultraviolet-B radiation seasonality, temperature seasonality and precipitation of the coldest quarter. Under future climate scenarios, the occupied area increased continuously towards the relatively higher elevation regions. Moreover, permafrost regions would become the buffer zone for the range shifts of niches and covers of Bryophytes on the QTP. This paper will improve our understanding of vegetable potential impact on the permafrost climate feedback.

DOI: 10.1007/s12665-021-10122-w

2022032658 Tang Liyun (Xi'an University of Science and Technology, School of Architecture and Civil Engineering, Xi'an, China); Yang Liujun; Wang Xiaogang; Yang Gengshe; Ren Xiang; Li Zhen and Li Guoyu. Numerical analysis of frost heave and thawing settlement of the pile-soil system in degraded permafrost region: Environmental Earth Sciences, 80(20), Article 693, illus. incl. 4 tables, 35 ref., October 2021.

Climate change in permafrost regions has caused frost heave and thawing settlement of soil around piles, inducing bridge engineering damage. Herein, the solid-to-liquid ratio is used as a hydrothermal coupling term and the frost heave ratio is introduced to establish a pile-soil system frost heave and thawing settlement model. An indoor physical model test is used to confirm the calculation model's correctness. Based on the investigation data of the No. 16 pile of the Chalabing Bridge on the Qinghai-Tibet Plateau, studies on soil temperature and moisture fields as well as frost heave and thawing settlement of the pile-soil system were conducted through the secondary development of partial differential equation (PDE) module in the COMSOL software package. Results show that the permafrost table will degrade from -3.2 to -4.9 m with an atmospheric temperature increase of 2.6°C in the next 50 years. The migration of water to the pile side will increase. Moreover, the thawing settlement amount on the pile side will gradually increase with increasing atmospheric temperature, and the maximum thawing settlement amounts on the pile side in years 1, 10, 30, and 50 will be 4.95, 7.63, 11.58, and 13.66 mm, respectively. Similarly, the frost heave amount will gradually decrease with increasing atmospheric temperature, and the frost heave amounts on the pile side for years 1, 10, 30, and 50 will be 6.66, 5.51, 3.99, and 3.69 mm, respectively. For the stability of pile foundation engineering in permafrost regions in the future, the prevention and control of thawing settlement should be focused.

DOI: 10.1007/s12665-021-09999-4

2022034833 Malov, A. I. (N. Laverov Federal Center for Integrated Arctic Research of the Ural Branch of the Russian Academy of Sciences, Arkhangelsk, Russian Federation). Tritium records to trace groundwater recharge and mixing in the western Russian Arctic: Environmental Earth Sciences, 80(17), Article 583, illus. incl. 2 tables, sketch maps, 59 ref., September 2021.

The Arctic regions are characterized by widespread development of permafrost. We studied a sandy aquifer used for water supply in the talik zone of the Pechora River valley. It has been found that groundwater has TDS values from 75 mg/L far from the river bank to 200 mg/L in the coastal zone. This indicates a predominantly atmospheric recharge of groundwater far from the river and the significant contribution of river water in the composition of groundwater in the coastal zone. The ³H age of groundwater in onshore wells was 20-25 years, on the basis of which it was concluded that the groundwater entering the aquifer before 1995-2000 was almost completely replaced. Mean water residence time, sampled from wells far from the river bank, ranges from 20 to 50 years. However, unlike onshore wells, this groundwater contains "bomb water" and old water that entered the aquifer before 1952. The age of the old water reaches 12.9 ± 2.5 ka. The use of information on the distribution of tritium isotopes made it possible to clarify the conditions of groundwater recharge and end-member ratios of young water, "bomb water" and old water in different parts of the aquifer.

DOI: 10.1007/s12665-021-09893-z

2022029072 Rettelbach, Tabea (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, Potsdam, Germany); Langer, Moritz; Nitze, Ingmar; Jones, Benjamin; Helm, Veit; Freytag, Johann-Christoph and Grosse, Guido. A quantitative graph-based approach to monitoring ice-wedge trough dynamics in polygonal permafrost landscapes: Remote Sensing, 13(16), Article 3098, illus. incl. sketch map, 77 ref., August 2, 2021. Includes appendices.

In response to increasing Arctic temperatures, ice-rich permafrost landscapes are undergoing rapid changes. In permafrost lowlands, polygonal ice wedges are especially prone to degradation. Melting of ice wedges results in deepening troughs and the transition from low-centered to high-centered ice-wedge polygons. This process has important implications for surface hydrology, as the connectivity of such troughs determines the rate of drainage for these lowland landscapes. In this study, we present a comprehensive, modular, and highly automated workflow to extract, to represent, and to analyze remotely sensed ice-wedge polygonal trough networks as a graph (i.e., network structure). With computer vision methods, we efficiently extract the trough locations as well as their geomorphometric information on trough depth and width from high-resolution digital elevation models and link these data within the graph. Further, we present and discuss the benefits of graph analysis algorithms for characterizing the erosional development of such thaw-affected landscapes. Based on our graph analysis, we show how thaw subsidence has progressed between 2009 and 2019 following burning at the Anaktuvuk River fire scar in northern Alaska, USA. We observed a considerable increase in the number of discernible troughs within the study area, while simultaneously the number of disconnected networks decreased from 54 small networks in 2009 to only six considerably larger disconnected networks in 2019. On average, the width of the troughs has increased by 13.86%, while the average depth has slightly decreased by 10.31%. Overall, our new automated approach allows for monitoring ice-wedge dynamics in unprecedented spatial detail, while simultaneously reducing the data to quantifiable geometric measures and spatial relationships.

DOI: 10.3390/rs13163098

2022029062 Sudakova, Maria (Russian Academy of Science, Siberian Branch, Earth Cryosphere Institute, Tyumen, Russian Federation); Sadurtdinov, Marat; Skvortsov, Andrei; Tsarev, Andrei; Malkova, Galina; Molokitina, Nadezda and Romanovsky, Vladimir. Using ground penetrating radar for permafrost monitoring from 2015-2017 at calm sites in the Pechora River delta: Remote Sensing, 13(16), Article 3271, illus. incl. 2 tables, sketch map, 34 ref., August 2, 2021.

This paper describes the results of ground penetrating radar (GPR) research combined with geocryological data collected from the Circumpolar Active Layer Monitoring (CALM) testing sites in Kashin and Kumzha in August 2015, 2016, and 2017. The study area was located on the Pechora River delta. Both sites were composed of sandy ground and the permafrost depth at the different sites ranged from 20 cm to 8-9 m. The combination of optimum offset and multifold GPR methods showed promising results in these investigations of sandy permafrost geological profiles. According to direct and indirect observations after the abnormally warm conditions in 2016, the thickness and water content of the active layer in 2017 almost returned to the values in 2015 in the Kashin area. In contrast, the lowering of the permafrost table continued at Kumzha, and lenses of thin frozen rocks that were observed in the thawed layer in August of 2015 and 2017 were absent in 2016. According to recent geocryological and geophysical observations, increasing permafrost degradation might be occurring in the Pechora River delta due to the instability of the thermal state of the permafrost.

DOI: 10.3390/rs13163271

2022028991 You Qinglong (Fudan University, Department of Atmospheric and Oceanic Sciences & Institute of Atmospheric Sciences, Shanghai, China); Cai Ziyi; Pepin, Nick; Chen, Deliang; Ahrens, Bodo; Jiang Zhihong; Wu Fangying; Kang Shichang; Zhang Ruonan; Wu Tonghua; Wang Pengling; Li Mingcai; Zuo Zhiyan; Gao Yanhong; Zhai Panmao and Zhang Yuqing. Warming amplification over the Arctic Pole and Third Pole; trends, mechanisms and consequences: Earth-Science Reviews, 217, Article no. 103625, illus. incl. sketch maps, 1 table, 237 ref., June 2021.

Warming amplification over the Arctic Pole (AP hereafter) and Third Pole (Tibetan Plateau, TP hereafter) can trigger a series of climate responses and have global consequences. Arctic amplification (AA) and Tibetan amplification (TA) are the most significant characteristics of climate change patterns over the two Poles. In this study, trends, mechanisms and consequences of both AA and TA are compared. Based on ERA5 reanalysis during 1979-2020, both AP and TP have undergone significant warming with an annual rate of 0.72 °C/decade and 0.34 °C/decade respectively, which exceeds the rates for the Northern Hemisphere (0.29 °C/decade) and the global means (0.19 °C/decade) over the same period. Based on 22 Coupled Model Intercomparison Project Phase 6 models, AA over the AP is warming at a rate almost four times than the global means and twice as fast over the TP. Although both AA and TA are projected to continue in the future, currently there is no consensus on the dominant mechanisms for AA or TA over the two Poles. Proposed mechanisms of AA can be divided into two types: local climate factors (sea ice-albedo feedback, Planck feedback, temperature gradient feedback, cloud feedback, and water vapor feedback); and poleward heat and moisture transport from lower latitudes (atmospheric circulation effect, ocean circulation effect, and modulation of Pacific and Atlantic SST). Consequences of AA include decline of sea ice cover, retreat of the Greenland ice sheet, permafrost degradation, accelerated disturbances in marine and terrestrial ecosystems, and influences on extreme climate events at lower latitudes. Anthropogenic greenhouse gas emission, snow/ice-albedo feedback, cloud-radiation interactions, water vapor and radiative flux feedbacks, local forcing and feedback processes, land use changes and reduction in total ozone, are generally considered to be the main mechanisms causing TA. TA has caused significant change within the atmosphere and cryosphere over the TP and its surroundings, such as changes in climate extremes, snow cover, the retreat of glaciers, and permafrost degradation. Similarities and differences of warming amplifications over the two Poles are proposed, and the relative contribution of each mechanism to the warming amplifications and how the specific consequences may compare over the two Poles remain unclear and under continuing investigation.

DOI: 10.1016/j.earscirev.2021.103625

2022031975 Natali, Susan M. (Woodwell Climate Research Center, Falmouth, MA); Holdren, John P.; Rogers, Brendan M.; Treharne, Rachael; Duffy, Philip B.; Pomerance, Rafe and MacDonald, Erin. Permafrost carbon feedbacks threaten global climate goals: Proceedings of the National Academy of Sciences of the United States of America, 118(21), Article e2100163118, illus., 15 ref., May 25, 2021.

Rapid Arctic warming has intensified northern wildfires and is thawing carbon-rich permafrost. Carbon emissions from permafrost thaw and Arctic wildfires, which are not fully accounted for in global emissions budgets, will greatly reduce the amount of greenhouse gases that humans can emit to remain below 1.5 °C or 2 °C. The Paris Agreement provides ongoing opportunities to increase ambition to reduce society's greenhouse gas emissions, which will also reduce emissions from thawing permafrost. In December 2020, more than 70 countries announced more ambitious nationally determined contributions as part of their Paris Agreement commitments; however, the carbon budgets that informed these commitments were incomplete, as they do not fully account for Arctic feedbacks. There is an urgent need to incorporate the latest science on carbon emissions from permafrost thaw and northern wildfires into international consideration of how much more aggressively societal emissions must be reduced to address the global climate crisis.

DOI: 10.1073/pnas.2100163118

2022033148 Romanowicz, Karl (University of Michigan, Department of Ecology and Evolutionary Biology, Ann Arbor, MI); Crump, Byron and Kling, George. Rainfall alters permafrost soil redox conditions, but meta-omics show divergent microbial community responses by tundra type in the Arctic: Soil Systems, 5(1), Article 17, illus. incl. 5 tables, 120 ref., 2021.

Soil anoxia is common in the annually thawed surface ('active') layer of permafrost soils, particularly when soils are saturated, and supports anaerobic microbial metabolism and methane (CH₄) production. Rainfall contributes to soil saturation, but can also introduce oxygen, causing soil oxidation and altering anoxic conditions. We simulated a rainfall event in soil mesocosms from two dominant tundra types, tussock tundra and wet sedge tundra, to test the impacts of rainfall-induced soil oxidation on microbial communities and their metabolic capacity for anaerobic CH₄ production and aerobic respiration following soil oxidation. In both types, rainfall increased total soil O₂ concentration, but in tussock tundra there was a 2.5-fold greater increase in soil O₂ compared to wet sedge tundra due to differences in soil drainage. Metagenomic and metatranscriptomic analyses found divergent microbial responses to rainfall between tundra types. Active microbial taxa in the tussock tundra community, including bacteria and fungi, responded to rainfall with a decline in gene expression for anaerobic metabolism and a concurrent increase in gene expression for cellular growth. In contrast, the wet sedge tundra community showed no significant changes in microbial gene expression from anaerobic metabolism, fermentation, or methanogenesis following rainfall, despite an initial increase in soil O₂ concentration. These results suggest that rainfall induces soil oxidation and enhances aerobic microbial respiration in tussock tundra communities but may not accumulate or remain in wet sedge tundra soils long enough to induce a community-wide shift from anaerobic metabolism. Thus, rainfall may serve only to maintain saturated soil conditions that promote CH₄ production in low-lying wet sedge tundra soils across the Arctic.

DOI: 10.3390/soilsystems5010017

2022028957 Campeau, A. (Uppsala University, Department of Earth Sciences, Uppsala, Sweden); Soerensen, A. L.; Martma, T.; Akerblom, S. and Zdanowicz, C. Controls on the ¹⁴C content of dissolved and particulate organic carbon mobilized across the Mackenzie River basin, Canada: Global Biogeochemical Cycles, 34(12), Article e2020GB006671, illus. incl. 1 table, 83 ref., December 2020.

The Mackenzie River basin (MRB) delivers large quantities of organic carbon (OC) into the Arctic Ocean, with significant implications for the global C budgets and ocean biogeochemistry. The amount and properties of OC in the Mackenzie River's delta have been well monitored in the last decade, but the spatial variability in OC sources transported by its different tributaries is still unclear. Here we present new data on the radiocarbon (¹⁴C) content of dissolved and particulate OC (D¹⁴C-DOC and D¹⁴C-POC) across the mainstem and major tributaries of the MRB, comprising 19 different locations, to identify factors controlling spatial patterns in riverine OC sources. The D¹⁴C-DOC and D¹⁴C-POC varied across a large range, from -179.9 ppm to 62.9 ppm, and -728.8 ppm to -9.0 ppm, respectively. Our data reveal a positive spatial coupling between the D¹⁴C of DOC and POC across the MRB, whereby the most ¹⁴C-depleted waters were issued from the mountainous west bank of the MRB. This ¹⁴C-depleted DOC and POC likely originates from a combination of petrogenic sources, connected with the presence of kerogens in the bedrock, and biogenic sources, mobilized by thawing permafrost. Our analysis also reveals intriguing relationships between D¹⁴C of DOC and POC with turbidity, water stable isotope ratio and catchment elevation, indicating that hydrology and geomorphology are key to understanding riverine OC sources in this landscape. A closer examination of the specific mechanisms giving rise to these relationships is recommended. For now, this study provides a road map of the key OC sources in this rapidly changing river basin. A+bstract Copyright (2020), The Authors.

DOI: 10.1029/2020GB006671

2022028856 Ponziani, Michel (Functional Centre of Aosta Valley, Department of Civil Protection, Aosta, Italy); Pogliotti, Paolo; Stevenin, Herve and Ratto, Sara Maria. Debris flow indicator for an early warning system in the Aosta Valley region: Natural Hazards, 104(2), p. 1819-1839, illus. incl. 6 tables, geol. sketch map, 50 ref., November 2020.

Aosta Valley, an Alpine region in north-western Italy, has an early warning system (EWS) that issues hydrogeological alerts based on hydrological modelling and rainfall thresholds that identify the possibility of shallow landslides being triggered in different areas of the region. The high headwater catchments are characterized by the presence of permafrost and glacial sediments, and they are frequently prone to debris flows. The summer debris flows are initiated by short-duration, high-intensity rainstorms, which are associated with high meteorological uncertainty; therefore, they are not always detected by the early warning system of shallow landslides. In this study, the hydro-meteorological and permafrost conditions related to the debris-flow events from 2013 to 2018 are investigated in order to determine the variables affecting the triggering of debris flows. Debris-Flow Indicator (DFI), an early warning system specific for debris flows, was developed using recorded air temperatures, thunderstorm alerts and forecast rainfall. Two alert levels of the DFI were defined by two thresholds (S1 and S2) of the freezing level determined from performance metrics. The performance of the DFI was then studied with a back-analysis from 2013 to 2019, using observed air temperatures and forecast rainfalls. This analysis showed that the experimental implementation of the DFI in the EWS of the Aosta Valley region resulted in detecting most of the events with some false alerts (for the lower threshold, S1) or detecting only major events, but without generating false alerts (for the higher threshold, S2). Consequently, the DFI can be applied for issuing debris-flow alerts for large areas in mountain regions based only on meteorological data and forecast.

DOI: 10.1007/s11069-020-04249-5

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2022033304 Jones, Benjamin M. (University of Alaska Fairbanks, Fairbanks, AK); Jones, Melissa Ward; Garron, Jessica; Grosse, Guido; Zwieback, Simon; Frost, Gerald J. J.; Bergstedt, Helena and Raynolds, Martha, organizers. 16th international circumpolar remote sensing symposium: Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, 181 p., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK. Individual abstracts within scope are cited separately.

2022033310 Bartsch, Annett (b.geos, Vienna, Austria); Irrgang, Anna; Boike, Julia; Martin, Julia; Grosse, Guido; Lantuit, Hugues; Nitze, Ingmar; Vieira, Goncalo; Jones, Benjamin M.; Widhalm, Barbara and Baeckmann, Clemens V. Earth observation for permafrost-dominated Arctic coasts; contributions to the next generation of the Arctic Coastal Dynamics database [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 49-51, illus., 7 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033334 Farquharson, Louise (University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK); Nicolsky, Dmitry; Romanovsky, Vladimir; Tracey, Bill; Irrgang, Anna and Jones, Benjamin M. Permafrost thaw and talik development drives future coastal inundation in North Slope communities [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 135-136, illus., 5 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033337 Hantson, Wouter (University of Maine, School of Forest Resources, Orono, ME); Hayes, Daniel; Yang, Dedi and Serbin, Shawn. Scaling spectral and structural characterizations of vegetation and landscape features along permafrost thaw gradients in Arctic tundra [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 142-144, illus., 4 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033318 Jones, Katreen Wikstrom (Alaska Department of Natural Resources, Division of Geological & Geophysical Science Center, Fairbanks, AK); Wolken, Gabriel; Daanen, Ronald P. and Stevens, De Anne. Change detection of permafrost-thaw triggered slope instablilities in coastal south-central Alaska using aerial lidar [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 78-80, illus., 5 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033343 Nole, Michael (Sandia National Laboratories, Center for Energy and Earth Systems, Albuquerque, NM); Frederick, Jennifer M. and Eymold, William K. Predicting permafrost greenhouse gas emissions by linking local and space-based observations through large-scale thermo-hydrologic modeling [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 157-158, illus., 5 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033319 Rowland, J. (Los Alamos National Laboratory, Earth and Environmental Science Division, Los Alamos, NM); Schwenk, J.; Muss, J.; Shelef, E.; Stachelek, J.; Stauffer, S.; Ahrens, D.; Douglas, M.; Chadwick, A.; Lamb, M. and Piliouras, Anastasia. Multiscale analysis of remotely sensed imagery to quantify spatial and temporal patterns of river bank erosion in floodplains with permafrost [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 81-82, May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033320 Runge, Alexandra (Alfred Wegener Institute, Permafrost Research, Potsdam, Germany); Juhls, Bennett; Westermann, S. and Grosse, Guido. Permafrost vulnerability; deriving a vulnerability index from ESA CC1 EO-datasets [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 83-85, illus., 4 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033312 Ward Jones, Melissa K. (University of Alaska, Institute of Northern Engineering, Fairbanks, AK); Jones, Benjamin M.; Nitze, Ingmar; Gessner, Matthias and Grosse, Guido. Observing permafrost coastal bluff erosion using a high spatial and temporal resolution remote sensing time series at Drew Point, Beaufort Sea Coast, Alaska [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 54-55, 3 ref., May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022033317 Webb, Elizabeth E. (University of Florida, School of Natural Resources and Environment, Gainesville, FL); Lijedahl, Anna K.; Cordeiro, Jada A.; Loranty, Michael M.; Witharana, Chandi and Lichstein, Jeremy W. Permafrost thaw drives surface water drainage across the pan-Arctic [abstr.]: in 16th international circumpolar remote sensing symposium (Jones, Benjamin M., organizer; et al.), Circumpolar Symposium on Remote Sensing of Arctic Environments, 16, p. 77, May 2022. Meeting: 16th international circumpolar remote sensing symposium (ICRSS), May 16-20, 2022, Fairbanks, AK.

2022029486 Ackerson, Crey (Simon Fraser University, Department of Earth Sciences, Burnaby, BC, Canada); Ward, Brent; Kennedy, Kristen; Dai, Chunli; Griffith, Peter C. and Hoy, Elizabeth. Active layer detachment slides, Kluane Ranges, southwest Yukon [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 85-6, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

Active layer detachment landslides (ALD's), where the failure plane is the contact between seasonally thawed ground and permafrost, are common in Yukon Territory. Ground disturbance associated with these slides can have a negative effect on water quality, infrastructure and human safety. The close connection between permafrost thaw and ALD's raises the possibility the frequency and magnitude of these events may be increasing with anthropogenic climate change. This project aims to: Determine magnitude and frequency changes of ALD's through historic airphoto analysis Study the failure mechanisms of a cluster of 25 ALD's that occurred on or around August 17, 2020, associated with a large precipitation event. The study area is the central and northern Kluane Ranges of the St. Elias Mountains, southwest Yukon. The area extends from A'ay Chu (Slim's River) northwest to the Donjek River and was selected based on an abundance of permafrost related landslides. Fieldwork occurred in July and August of 2020 and included field visits, unmanned aerial vehicle (UAV) based photogrammetry and low-level helicopter flights. Changes to the frequency and magnitude of ALD's will be investigated utilizing historic airphotos and satellite imagery. Time intervals of 10-20 years, beginning in 1946, will be used to generate digital elevation models (DEM's) from airphotos and satellite imagery using Structure-from-Motion photogrammetry techniques. An inventory of ALD's will be made for each time interval to determine changes in frequency. Changes in magnitude will be assessed by comparing slide area of the each time interval. The cluster of 25 near-synchronous ALD's have failure planes marked by the 1250 BC White River Tephra, giving them a distinctive streaky white appearance. Detailed DEM's generated from satellite imagery indicate a gentle over steep topography. The insulating properties and hydraulic conductivity of the tephra will be investigated to better understand what role the tephra plays in the failure mechanism. Landslide modeling will be preformed to determine a correlation between causative factors and landslide occurrence.

DOI: 10.1130/abs/2021AM-369887

2022029671 Aman Cromwell, Lindsey (West Virginia University, Morgantown, WV); Knights, Deon and Russoniello, Christopher. Surface water-groundwater interactions contributing to annual and seasonal shrinkage of Arctic lakes [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 120-3, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

Lakes in Arctic delta environments act to smooth fresh river discharge rates to the Arctic Ocean, both filtering and serving as reservoirs for nutrients, sediments, and flood waters. Recent remote sensing studies show Arctic lakes in discontinuous permafrost zones are shrinking over seasonal and annual time scales with potential impacts on those mitigation roles. The shrinkage of these lakes are attributed to the heat transfer from relatively warm surface bodies to the surrounding permafrost. Surface water connectivity between channels and lakes serve as a pathway to introduce greater temperatures into isolated areas. The development of taliks (local permafrost thaw permafrost beneath surface water bodies) increases lake-groundwater connectivity, which promotes additional permafrost thaw and decreases Arctic lake volume and surface area. We built numerical groundwater, heat flow, and transport models that incorporate freeze-thaw dynamics in FEFLOW to investigate the correlation between lake-channel proximity, and subsequent heat transfer and talik development to greater groundwater connectivity. These models are calibrated against in-situ temperature measurements from a Northern Alaska field season in summer 2021 to provide realistic boundary conditions. Preliminary results suggest lakes closest to the channel experience greater heat transfer and subsequent talik development while lakes furthest from the channel remain isolated. Understanding the changing dynamics of thermokarst lakes within Arctic deltas is critical for future mitigation efforts.

DOI: 10.1130/abs/2021AM-369904

2022029865 Englert, Peter (University of Hawaii at Manoa, Hawaii Institute of Geophysics and Planetology, Honolulu, HI); Bishop, Janice; Foerder, Andrew; Bailey, Andrew H.; Burton, Zachary Florentino; Patel, Shital; Dera, Przemyslaw; Koeberl, Christian and Gibson, Everett K. Weathering and chemical alteration in Wright Valley, Antarctica, as an analog for alteration on Mars [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 179-11, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

Two ponds in Wright Valley, Antarctica , Don Juan Pond (DJP) and Don Quixote Pond (DQP), are in a landscape that has experienced moderate Pliocene expansion of local alpine glaciers paired with continuous cold-desert conditions. The basins of DJP and DQP in the South and North Forks of the valley have experienced alteration over the past 2 million years that they have been ice-free. A detailed comparison of processes of the DJP and DQP microenvironments demonstrates their potential as analogs for understanding alteration processes on Mars. We investigated trends in i) major and trace elements, ii) mineralogy (from reflectance spectra and XRD), and iii) soluble ions in the soils from the surface, sediment cores, and trenches as a function of depth and location in the basins to evaluate the effects of physical and chemical alteration. Differences in multiple parameters of three cores from the DJP saltpan reveal inversely related chemical and physical alteration gradients as a function of distance to the pond. For example, average sulfate and chloride salt abundances decrease from about 20% to less than 5% over 300 m. No such gradient is observed in radially collected surface samples of the DQP basin. While sulfate and chloride salt abundances are consistently around 5% in samples close to and far away from DQP, the salt abundances at a radial distance between 16 and 28 m of a 50 m sampling traverse are at about 15%. At DJP basin light rare earth element abundances decrease significantly towards the pond as does variability with depths, arguing strongly for increasing chemical alteration towards the pond. Rare earth element abundances in DQP basin are grouped closer and do not illustrate the spread found at DJP, indicating a lower level of chemical alteration. The difference in degree of alteration between the two microenvironments of similar soil composition and exposure time is attributed to the sources of liquid water. DJP sources include upwelling groundwater, temporary stream input, and active layer transport atop the permafrost table within the colluvium end of the pond. For DQP only shallow groundwater has been identified as a liquid water source. Our study provides complex and graded aqueous alteration scenarios under cold and dry desert conditions with strong potential for analogous aqueous processes on Mars, past or present.

DOI: 10.1130/abs/2021AM-364655

2022030017 Guimond, Julia (Dalhousie University, Department of Civil and Resource Engineering, Halifax, NS, Canada); Mohammed, Aaron A.; Walvoord, Michelle A.; Bense, Victor F. and Kurylyk, Barret. Climate change impacts on Arctic submarine groundwater discharge [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 230-5, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

Climate change is impacting the exchange of groundwater and surface water in the coastal zone with responses dependent on hydrologic setting, sea-level rise rate, local climate, and geological setting. In permafrost environments, climate change is activating groundwater flow systems with potential implications for surface-subsurface connectivity and submarine groundwater discharge. Understanding of present and projected coastal high-latitude groundwater-ocean exchange is lacking due to limited field data and numerical models capable of simulating complex coastal Arctic processes. Here, we use a newly developed permafrost hydrological model that simulates variable-density groundwater flow and salinity-dependent freeze-thaw processes to investigate the impacts of sea-level rise coupled with land and ocean warming on the magnitude, distribution, and timing of submarine groundwater discharge. Results project an increase in the magnitude of submarine groundwater discharge with warming, particularly in the highest warming scenarios following the formation of a lateral talik. This increase is predominantly driven by increased freshwater discharge as a result of enhanced groundwater flow and land-sea connectivity. In contrast, sea-level rise decreases the magnitude of submarine groundwater discharge while also pushing the location of peak discharge landward. Enhanced understanding of changes in coastal zone groundwater flow and exchange due to climate change is critical with profound implications for coastal stability, carbon fluxes, and water resources.

DOI: 10.1130/abs/2021AM-369879

2022031204 Jiang, Hehe (University of Toronto, Department of Earth Sciences, Toronto, ON, Canada) and Chu, Xu. Rapid deglaciation in the Paleoproterozoic Huronian glacial event indicated by clastic dikes in Ontario, Canada [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 55-12, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

Clastic dikes occur in a wide variety of depositional environments. The injection of clastic dikes is due to forceful emplacement of remobilized sediments in response to overpressure that might be triggered by seismic activity, tectonic stress, rapid sediment deposition, and variation in pore fluid pressures. In this study, we investigated the clastic dikes crosscutting the glacial-interglacial section of the Quirke Lake Group within the Paleoproterozoic Huronian supergroup (2.45-2.2 Ga) near Espanola, Ontario, Canada. The Bruce Formation at the lowest of Quirke Lake Group consists of glaciogenic diamictites representing the second pulse of Huronian Glacial Event. The overlying Espanola Formation consists of lower limestone units and upper siltstone-argillite-dolomite units, and is considered to deposit in interglacial shallow marine or lacustrine environments. Sandstone and conglomerate dikes are commonly seen in the Espanola Formation. The petrography and geochemistry of these clastic dikes show close affinity with the underlying Bruce formation, suggesting upward injection of the unconsolidated sediments shortly after deposition of the Bruce Formation. Cobble-sized clasts concentrate in the center of the dikes within a granule-to-silt matrix. This alignment suggests liquefaction and a laminar flow profile for the process of injection. We modeled plug flow in a channel assuming that the suspension flow behaves as a Herschel-Bulkley fluid, and calculated the velocity profile using different viscosities. Model results show that the drag force exerted on a »6cm clast is large enough to overcome the gravitational force with relatively small disturbance or overpressure (»2000 Pa/m). The gradient of overpressure can possibly be attributed to sub-permafrost instabilities during the unloading of glacial ice sheets. Thus, we conclude that the deglaciation of the Bruce Glacial Event was rapid. The Bruce-Espanola boundary is featured by drastic changes of a range of geochemical proxies, which are cited by researchers to argue for the synchronicity of oxygenation and glacial-interglacial cycles within the Huronian Glacial Event. Rapid interglacial thawing would lead to a sudden flux of nutrients into the oceans, which might have stimulated the blooms of oxygenic photosynthesis.

DOI: 10.1130/abs/2021AM-370324

2022029859 Yesilbas, Merve (Umea University, Department of Chemistry, Umea, Sweden) and Bishop, Janice. Following the water on Mars; a molecular level study for liquid salty brine formation in Mars analogs in the mid-IR region [abstr.]: in Geological Society of America, 2021 annual meeting; GSA connects 2021, Abstracts with Programs - Geological Society of America, 53(5), Abstract no. 179-5, October 2021. Meeting: Geological Society of America, 2021 annual meeting; GSA connects 2021, Oct. 10-13, 2021, Portland, OR.

H₂O is a simple molecule, yet essential for all living organisms to sustain life. NASA and ESA have focused on the 'follow the water' strategy to search for life and habitability on Mars and other planetary bodies, which is a component of the NASA Perseverance and upcoming ESA Rosalind Franklin Mars rover missions. The extreme conditions on Mars today allow no stable water on the surface, but various types of chloride and perchlorate salts that have been widely detected in martian regoliths across equatorial and mid-latitude regions could facilitate the formation of liquid salty brines well below 0 °C due to the deliquescence properties of these salts. Such liquid salty brines can also be formed and stabilized within aggregates of mineral particles by forming thin water films. While previous studies with Cl-bearing salts mainly focused on their deliquescence/efflorescence features, some of our recent studies specifically focused on the effect of Mars analogs on the low temperature phase changes of briny water. In our experiments, we aim to identify the complex relationships of Cl salts in Mars analogs as they transform from the permafrost state to a liquid salty brine and then to thin water films formed in soil aggregates using cryogenic FTIR spectroscopy in the mid-IR region. In this study, we used two volcanic soils from Hawaii plus the Mojave Mars Simulant (MMS) with varied particle size distributions and chemical compositions. We mixed these samples with 40% wt. CaCl₂ and 10% wt. Mg(ClO₄)₂ solutions. These mixtures were flash-frozen at -90 °C as a coating on a precooled temperature controlled Attenuated Total Reflectance (ATR) stage. The temperature was slowly increased up to 25 °C while continually collecting spectra in order to monitor the phase changes of the frozen/liquid salty brines. We observed that each sample has distinct spectral features at -90 °C depending on the type of Cl salt. As the samples were warmed up, one of the volcanic ash samples presented spectral changes following the phase diagrams of Cl salts including the transition from frozen to liquid salty water, yet the other samples presented liquid salty brine features at higher temperatures than expected. Future studies with cryogenic-XRD are needed to resolve the potential role of salty martian analogs in liquid salty brine formation.

DOI: 10.1130/abs/2021AM-370874

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