Permafrost Monthly Alerts (PMAs)

USPA LogoThe USPA is pleased to announce the availability of an updated searchable database on permafrost-related publications. The American Geosciences Institute (AGI), with support from the National Science Foundation (NSF), has migrated the previous Cold Regions Bibliography to a new platform. Included are the USPA supported PMAs dating back to 2011. The Bibliography is searchable at


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

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2021069030 Whalley, W. Brian (University of Sheffield, Department of Geography, Sheffield, United Kingdom). Geomorphological information mapping of debris-covered ice landforms using Google Earth; an example from the Pico de Posets, Spanish Pyrenees: Geomorphology, 393, Article 107948, November 15, 2021. Based on Publisher-supplied data.

Geomorphological mapping records 'snapshots', making it difficult to investigate change and sensitivity in changing environments. The high resolution now available in Google Earth (GE) permits re-investigation of landscape features/landforms previously recorded in the literature or mapped. Transects across geomorphologically interesting locations can be provided with decimal degree WGS 84 locations and bearings via GE. Landform elements are identified, located and coded onto transects that summarise geomorphological information. Transects crossing rock cliffs, scree slopes, snowpatches, protalus ramparts, 'vanishing' glaciers, moraines and rock glaciers are investigated using GE on the Pico de Posets in the Spanish Pyrenees. Observations of geometry/form, materials and processes involved in ice and sediment movement are linked to the Randolph Glacier Inventory and map records. The transect mapping shows that accumulated weathered rock debris insulated a remnant Little Ice Age glacier that formed a lateral moraine and a contiguous rock glacier as the glacier wasted down. Landforms previously considered to indicate permafrost are shown not to do so. Glacigenic formation of moraines, protalus rampart and rock glaciers provides the simplest explanation for their origin.

DOI: 10.1016/j.geomorph.2021.107948

2021067286 Fouché, Julien (Université de Montpellier, Laboratoire d'Étude des Interactions entre Sol, Agrosystème et Hydrosystème, Montpellier, France); Bouchez, Camille; Keller, Catherine; Allard, Michel and Ambrosi, Jean-Paul. Seasonal cryogenic processes control supra-permafrost pore water chemistry in two contrasting Cryosols: Geoderma, 401, Article 115302, illus. incl. 2 tables, sketch map, 156 ref., November 1, 2021.

Over the last decades, Arctic landscapes have experienced intense warming leading to permafrost degradation and rapid ecosystem changes. Active layer thickening, widespread melting of ground ice and thermo-erosion have affected the mobilization of organic and mineral elements. While the carbon and nitrogen cycles are intensively studied, the soil weathering has been less documented. In the present study, we monitored the chemistry of soil capillary and gravitational pore waters, rainfall and stream waters daily during the growing season in two experimental sites under tussock tundra vegetation in the low-Arctic region, in Salluit (Nunavik, Canada). We aimed to investigate the seasonal thaw controls on the evolution of concentrations of major organic and inorganic elements in the active layer (i.e., seasonally thawed surface layers) of two permafrost soils (Cryosols) differing in parental materials: an ombrotrophic bog (i.e., Histic Cryosol) and post-glacial marine sediments continuously waterlogged (i.e., Turbic Cryosol). In the Histic Cryosol, the electrical conductivity was <100 mS cm-1 and Cl- and Na+ were the dominant soluble ions originating from atmospheric depositions. In the Turbic Cryosol, decarbonated in the first 40 cm, Ca2+ and Mg2+ were the dominant soluble ions in the capillary water reflecting the dissolution of soil minerals, while Cl- and SO42- dominated in gravitational water, illustrating inputs from uphill. In the two soils, Ca2+ and Mg2+ concentrations as well as Mg/Na and Ca/Na increased with depth. Along summer, the soil pore water chemistry evolved with thaw front and water table depths in the two sites. Particularly in the Histic Cryosol, electrical conductivity, solute concentrations, Mg/Na and Ca/Na ratios increased with the thaw front deepening. Our observations suggest that the active layer thickening and increasing supra-permafrost flow contribution, expected to increase with Arctic warming, could lead to a shift in chemistry of pore waters in organic and mineral permafrost soils, differently depending on permafrost landform settings.

DOI: 10.1016/j.geoderma.2021.115302

2021067293 Yang Shuhua (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resource, State Key Laboratory of Cryospheric Science, Lanzhou, China); Li Ren; Wu Tonghua; Wu Xiaodong; Zhao Lin; Hu Guojie; Zhu Xiaofan; Du Yizhen; Xiao Yao; Zhang Yuxin; Ma Junjie; Du Erji; Shi Jianzong and Qiao Yongping. Evaluation of soil thermal conductivity schemes incorporated into CLM5.0 in permafrost regions on the Tibetan Plateau: Geoderma, 401, Article 115330, illus. incl. 4 tables, geol. sketch map, 76 ref., November 1, 2021.

Soil thermal conductivity (STC) is essential parameter for revealing thermodynamic changes and projecting changes in soil thermal regimes. However, the incorporation of different STC schemes into land surface process models (LSMs) can afford large errors. Thus, to accurately simulate soil thermal regimes in permafrost regions, a suitable STC scheme in LSMs is important. Herein, we selected nine normalized STC schemes and evaluated their performance in simulating STC and soil temperatures with in situ measurements in permafrost regions on the Tibetan Plateau (TP). These schemes were divided into three categories and incorporated into the latest version of the Community Land Model (CLM5.0). The results showed that the category comprising minerals, soil organic matter, and gravel soil afforded better performance at most sites than the other categories. The Balland and Arp (BA2005), Chadburn (C2015), and Bao (B2016) schemes had better performances in their affiliated categories, respectively. The BA2005 scheme ranked the best among the selected schemes with an average root-mean-square error decreased of 56.2% and 15.0% in simulating STC and soil temperatures compared to the default scheme, respectively. Additionally, the different schemes yielded a maximum difference of 2.69 W·m-1 K-1 and 2.55 °C in simulating STC and soil temperature, respectively. Possible causes affecting the results were also investigated. The results indicated that soil moisture is a determinant: slight changes in soil moisture may cause large changes in thermal processes. However, the CLM5.0 yields large uncertainties of soil moisture. In addition, soil properties, atmospheric forcing data, and model structures also yielded errors in the simulated results. Note that no single STC scheme can be applied to all regions with satisfactory results. Therefore, multiple schemes need to be employed depending on their suitability in different regions. And more studies should focus on the accuracy of the hydraulic processes, especially soil hydraulic conductivity, unfrozen water, and snow processes.

DOI: 10.1016/j.geoderma.2021.115330

2021061648 Kong, Xiangbing (Laval University, Department of Civil and Water Engineering, Quebec City, QC, Canada) and Doré, Guy. Thermal stabilization of embankments built on thaw-sensitive permafrost: Journal of Cold Regions Engineering, 35(3), September 2021. Based on Publisher-supplied data.

DOI: 10.1061/(ASCE)CR.1943-5495.0000256

2021061688 Kuhn, D. (Federal Institute for Geosciences and Natural Resources, Hanover, Germany); Torizin, J.; Fuchs, M.; Hermanns, R. L.; Redfield, T. F. and Balzer, D. Back analysis of a coastal cliff failure along the Forkastningsfjellet coastline, Svalbard; implications for controlling and triggering factors: Geomorphology, 389, Article 107850, illus. incl. 3 tables, sketch map, September 15, 2021. Based on Publisher-supplied data.

Based on a morphostructural analysis of a cliff coast segment of Forkastningsfjellet, back analysis of the August 12th, 2016 rock slide situated at 78°19'10"N/15°39'52"E was carried out. This rock slide comprises a volume of 175,000 m3, and indicates a partial reactivation at the front of the ~100 million m3 large postglacial Forkastningsfjellet rock slide. We studied the controlling and triggering factors of the reactivation using a 2-D limit-equilibrium calculations and a 3-D simulation with Scoops3D. Slope instability initiated along a pre-existing listric block fault that was inherited from the postglacial Forkastningsfjellet rock slide. The cause of the failure is attributed to a strength decrease and additional water pressures along the pre-existing sliding plane, possibly in combination with a degradation of the affected weak shales of the Rurikfjellet Formation, which build up a major part of the steep slope. Although the analysis suggests a structural control on the type and mechanism of slope failure, a significant impact of climate-related factors is inferred. Increasing temperatures and changing precipitation trends are reported from Svalbard. These are interpreted to foster permafrost degradation and reduce bonding forces in the thawing ice-filled fractures at the site. In addition, progressive weakening by more frequent frost and thaw cycles of the slaking shales and the introduction of additional water pressures to the rock mass are considered to contribute to the instability. The final trigger of the 2016 failure is attributed to a two-day rainfall that had preceded the event. The application of the Scoops3D software tool showed that it is capable of predicting the locations and affected volumes of landslides with reasonable accuracy, when the geological and structural setting is well established. Under such premises the tool can be used to support preliminary susceptibility assessments in study areas with comparable geological and morphostructural settings.

DOI: 10.1016/j.geomorph.2021.107850

2021061678 Lillquist, Karl (Central Washington University, Geography Department, Ellensburg, WA) and Weidenaar, Mark. Rock glaciers in the eastern Cascades, Washington State, USA; impacts of selected variables on spatial distribution and landform dimensions: Geomorphology, 389, Article 107839, illus. incl. 6 tables, sketch map, September 15, 2021. Based on Publisher-supplied data.

Recent regional-scale studies of rock glaciers have added much to our knowledge of rock glaciers and associated permafrost spatial distribution. In this study, we used Google Earth Pro imagery and selected field work to identify and classify 159 rock glaciers in the marine-influenced, continental margin, Eastern Cascades of Washington state in Western North America. Most rock glaciers are tongue-shaped, talus-derived, intact features. The majority are found in the Northeastern Cascades where temperatures are lower because of high elevations, high latitudes, and increasingly continental conditions. Most rock glaciers are also clustered around high peaks and ridges at the bases of cirque headwalls where steep, converging slopes provide ample debris. Dimensions of rock glaciers increase with increasing maximum elevation, area, relief, length, and slope of rocksheds. In comparison to other ranges, Eastern Cascades rock glaciers are generally small and low in spatial density, perhaps because of lower elevations and younger landscapes. Despite this, rock glaciers are significant components of the alpine/subalpine geomorphic continuum in the Eastern Cascades typically occupying late Pleistocene or Holocene cirques. Intact rock glaciers suggest that discontinuous permafrost currently exists down to ~1945 m elevation while relict features suggest that permafrost once extended down to ~1870 m elevation. As climate warms, slowly melting ice in rock glaciers will play a larger role in providing base flow for streams previously primarily supplied by snow and glacier melt.

DOI: 10.1016/j.geomorph.2021.107839

2021067307 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Dornblaser, Mark M. and Striegl, Robert G. Storm-scale and seasonal dynamics of carbon export from a nested subarctic watershed underlain by permafrost: Journal of Geophysical Research: Biogeosciences, 126(8), Article e2021JG006268, illus. incl. 2 tables, 85 ref., August 2021.

Subarctic catchments underlain by permafrost sequester a major stock of frozen organic carbon (C), which may be mobilized as the Arctic warms. Warming can impact C export from thawing soils by altering the depth and timing of runoff related to changing storm and fire regimes and altered soil thaw depths. We investigated C export in a first order headwater stream (West Twin Creek) and its receiving third order river (Beaver Creek) in interior Alaska using discrete sampling of dissolved organic and inorganic C (DOC and DIC) and 15-min collection of specific conductance (SC), fluorescent dissolved organic matter (fDOM) and water discharge (Q). Storm SC-Q relationships displayed negative slopes, indicating solute limitation and limited influence of seasonal soil thaw on storm runoff chemistry. Concurrently, fDOM-Q displayed positive slopes that decreased over the summer, indicating flushing of a limited fDOM pool. Baseflow DIC increased over the season concurrent with soil thaw, with higher DIC at the larger scale indicating greater influence of deeper, mineral-rich flow paths. Storm and seasonal trends were generally similar at both scales. The biggest difference was in fDOM, which displayed higher concentrations and slower depletion in the first order stream. Improved process understanding from this study can be used to better predict carbon export and cycling by stream networks as northern forests and arctic regions continue to warm. Abstract Copyright Published 2021. This article is a U.S. Government work and is in the public domain in the USA.

DOI: 10.1029/2021JG006268

2021068872 Mleczak, Mateusz (Adam Mickiewicz University, Institute of Geology, Poznan, Poland); Woronko, Barbara; Pisarska-Jamrozy, Malgorzata and Bujak, Lukasz. Permafrost as the main factor controlling the fluvial sedimentation style on glaciomarginal fans: Sedimentary Geology, 422, Article 105971, illus. incl. strat. cols., 2 tables, geol. sketch maps, 94 ref., August 2021.

This study describes the sedimentary successions of two glaciomarginal fans (=end moraines) deposited during MIS 6 and MIS 2 in the eastern and northwestern part of Poland. Sedimentological analyses of the successions indicate they were both deposited close to the ice sheet margin and are dominated by extensive gravelly and sandy sheet beds derived from the upper flow regime with single ice-wedge structures. Qualitative and quantitative analysis of the pancake-like gravelly and sandy sediments was performed using Markov chain analysis. The presence of these, admittedly common, sedimentary successions raises two key points: why sheetfloods are so common on glaciomarginal fans instead of in-channel flows, and whether sedimentary rhythms deposited by sheetfloods represent the full depositional records, or only partial ones due to accompanying erosion. While both points remain unclear, the answers to these questions may be connected to the presence of permafrost, which occupied the foreland of the ice sheet where the glaciomarginal fans were deposited: it can control the type of proglacial river flows on glaciomarginal fans, the depth of erosion and influence the record of sedimentary rhythms.

DOI: 10.1016/j.sedgeo.2021.105971

2021061797 Ulrich, Mathias (Leipzig University, Institute for Geography, Geoinformatics and Remote Sensing, Leipzig, Germany); Jongejans, Loeka L.; Grosse, Guido; Schneider, Birgit; Opel, Thomas; Wetterich, Sebastian; Fedorov, Alexander N.; Schirrmeister, Lutz; Windirsch, Torben; Wiedman, Julia and Strauss, Jens. Geochemistry and weathering indices of yedoma and alas deposits beneath thermokarst lakes in central Yakutia: Frontiers in Earth Science (Lausanne), 9(704141), 23 p., illus. incl. 2 tables, 100 ref., August 2021.

Ice- and organic-rich deposits of late Pleistocene age, known as Yedoma Ice Complex (IC), are widespread across large permafrost regions in Northeast Siberia. To reconstruct Yedoma IC formation in Central Yakutia, we analyzed the geochemistry, sedimentology, and stratigraphy of thawed and frozen deposits below two thermokarst lakes in different evolutionary stages (a mature alas lake and a initial Yedoma lake) from the Yukechi site in the Lena-Aldan interfluve. We focused on inorganic geochemical characteristics and mineral weathering in two ~17 m long sediment cores to trace syngenetic permafrost aggradation and degradation over time. Geochemical properties, element ratios, and specific weathering indices reflect varying sedimentation processes and seasonal thaw depths under variable environmental conditions. Deeper thaw during the interstadial Marine Isotope Stage (MIS) 3 enabled increasing mineral weathering and initial thermokarst processes. Sedimentological proxies reflect high transport energy and short transport paths and mainly terrestrial sediment supply. The Yedoma formation resulted from fluvial, alluvial and aeolian processes. Low mean TOC contents in both cores contrast with Yedoma deposits elsewhere. Likely, this is a result of the very low organic matter content of the source material of the Yukechi Yedoma. Pronounced cryostructures and strongly depleted pore water stable isotopes show a perennially frozen state and preserved organic matter for the lower part of the Yedoma lake core, while changing permafrost conditions, conditions promoting weathering, and strong organic matter decomposition are suggested by our proxies for its middle and upper parts. For the alas lake core, less depleted water stable isotopes reflect the influence of recent precipitation, i.e. the infiltration of rain and lake water into the unfrozen ground. The FENG, MIA(R), and ICV weathering indices have proven to be promising proxies for the identification of conditions that promote mineral weathering to different degrees in the stratigraphy of the thawed and frozen Yedoma deposits, for which we assume a rather homogeneous chemical composition of the parent material. Our study highlights that the understanding of environmental conditions during Yedoma formation and degradation processes by specific geochemical proxies is crucial for assessing the potential decomposition and preservation of the frozen and unfrozen Yedoma inventories.

DOI: 10.3389/feart.2021.704141

2021062816 Wang Honglei (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Laboratory of Frozen Soil Engineering, Lanzhou, China); Sun Zhizhong; Zhang Jianming; Liu Yongzhi and Li Guoyu. Formation and evolution of suprapermafrost taliks beneath earth-filled embankments along the Qinghai-Tibet Railway in permafrost regions: Cold Regions Science and Technology, 188, Paper 103300, illus. incl. 1 table, sketch map, August 2021. Based on Publisher-supplied data.

Taliks are bodies or layers of unfrozen ground in permafrost areas. Suprapermafrost taliks (SPTs) formed between the active layer and permafrost table beneath embankments along the Qinghai-Tibet Railway (QTR) would reduce the stability of the embankments and thus threaten the safety of QTR operations, because the SPTs exhibit a lower bearing capacity than that of frozen ground. This study investigated the formation and evolution of SPTs beneath earth-filled embankments at two monitoring sites (P7 and P17) along the QTR in order to determine the SPTs formation mechanism. The SPTs under the left shoulder of the embankments at P7 and P17 were caused by thermal disturbance of filling and vertical heat accumulation, respectively. The mechanism of SPTs formation beneath the embankments was closely associated with the mean annual ground temperature and the height of embankment filling materials. The study findings can facilitate understanding the formation and evolution of SPTs beneath the embankments in similar sections along the QTR. In particular, the findings can serve as a guidance for the QTR administration bureau in implementing countermeasures for eliminating these unfrozen layers and increasing ground bearing capacity.

DOI: 10.1016/j.coldregions.2021.103300

2021061796 Monhonval, Arthur (Université Catholique de Louvain, Earth and Life Institute, Louvain-la-Neuve, Belgium); Strauss, Jens; Mauclet, Elisabeth; Hirst, Catherine; Bemelmans, Nathan; Grosse, Guido; Schirrmeister, Lutz; Fuchs, Matthias and Opfergelt, Sophie. Iron redistribution upon thermokarst processes in the yedoma domain: Frontiers in Earth Science (Lausanne), 9(703339), illus. incl. block diags., 2 tables, sketch map, 101 ref., July 2021.

DOI: 10.3389/feart.2021.703339

2021064160 Nesterova, Nataliia (Melnikov Permafrost Institute, North-Eastern Permafrost Station, Magadan, Russian Federation); Makarieva, Olga and Post, David Andrew. Parameterizing a hydrological model using a short-term observational dataset to study runoff generation processes and reproduce recent trends in streamflow at a remote mountainous permafrost basin: Hydrological Processes, 35(7), Paper no. e14278, illus. incl. 7 tables, geol. sketch map, 86 ref., July 2021.

Recent decades have seen a change in the runoff characteristics of the Suntar River basin in the mountainous, permafrost, hard-to-reach region of Eastern Siberia. This study aims to investigate and simulate runoff formation processes, including the factors driving recent changes in hydrological response of the Suntar River, based on short-term historical observations of a range of hydrological, climatological and landscape measurements conducted in 1957-1959. The hydrograph model is applied as it has the advantage of using observed physical properties of landscapes as its parameters. The developed parametrization of the goltsy landscape (rocky-talus) is verified by comparison of the results of simulations of variable states of snow and frozen ground with observations carried out in 1957-1959. Continuous simulations of streamflow on a daily time step are conducted for the period 1957-2012 in the Suntar River (area 7680 km2, altitude 828-2794 m) with mean and median values of Nash-Sutcliff criteria reaching 0.58 and 0.67, respectively. The results of simulations have shown that the largest component of runoff (about 70%) is produced in the high-altitude area which comprises only 44% of the Suntar River basin area. The simulated streamflow reproduces the patterns of recently observed changes, including the increase in low flows, suggesting that the increase in the proportion of liquid precipitation in autumn due to air temperature rise is an important factor in driving streamflow changes in the region. The data presented are unique for the vast mountainous parts of North-Eastern Eurasia which play an important role in the global climate system. The results indicate that parameterizing a hydrological model based on observations allows the model to be used in studying the response of river basins to climate change with greater confidence. Abstract Copyright (2021), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.14278

2021065884 Hou Yandong (Chinese Academy of Sciences, Nanjing Institute of Geography and Limnology, Nanjing, China); Long Hao; Shen Ji and Gao Lei. Holocene lake-level fluctuations of Selin Co on the central Tibetan Plateau; regulated by monsoonal precipitation or meltwater?: Quaternary Science Reviews, 261, Article no. 106919, illus. incl. sketch maps, strat. col., 4 tables, block diags., 141 ref., June 1, 2021.

Over the Tibetan Plateau (TP), lakes as paleoenvironmental archives have been the most extensively investigated for their sensitivities to climate change on different timescales. Well-preserved shoreline and terrace remains surrounding these lakes provide critical geomorphological and sedimentary evidence that can be used to infer past lake levels over geological timescales. These features can offer an analogue for understanding how future lake-levels respond to global warming. In this study, we investigated a series of water level-related depositional profiles around the Selin Co basin from the central TP, by dating 28 samples using K-feldspar luminescence techniques. Combining the obtained chronological data with sedimentological, stratigraphic evidence and differential GPS survey observations, the Holocene history of lake-level fluctuations in Selin Co was inferred. The results show a stable highstand between 10 ka and 7 ka but a striking subsequent lake-level decline. This pattern appears to follow the solar insolation-forced changes in the intensity of the Indian summer monsoon (ISM), particularly during the early Holocene. However, such gradual weakening of ISM intensity after the early Holocene may not interpret the dramatically rapid shrinking of Selin Co, implying other components are largely underrecognized driving factors accounting for the effective moisture of lakes in the early Holocene. Here, we argue that the increased meltwater input from glaciers and permafrost, together with increased precipitation, might have resulted in the high lake level at 10-7 ka, as the high summer temperature during the early Holocene induced massive melting water flow into the lake. By 7 ka, the abrupt lake-level drop is likely related to the decreased meltwater owing to decreasing regional temperatures documented from glacier landforms, ice cores and lacustrine sediments. Therefore, we highlight that meltwater from glaciers and permafrost poured into lakes on the central TP, particularly during warm periods on the millennial timescales, might also dominate the Holocene high lake levels.

DOI: 10.1016/j.quascirev.2021.106919

2021061795 Wetterich, Sebastian (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Rudaya, N.; Nazarova, L.; Syrykh, L.; Pavlova, M.; Palagushkina, O.; Kizyakov, A.; Wolter, J.; Kuznetsova, T.; Aksenov, A.; Stoof-Leichsenring, K. R.; Schirrmeister, Lutz and Fritz, M. Paleo-ecology of the yedoma ice complex on Sobo-Sise Island (eastern Lena Delta, Siberian Arctic): Frontiers in Earth Science (Lausanne), 9(681511), 15 p., illus. incl. 2 tables, 108 ref., June 2021.

DOI: 10.3389/feart.2021.681511

2021063027 van Huissteden, J. (Vrije Universiteit, Earth Science Department, Amsterdam, Netherlands); Teshebaeva, K.; Cheung, Y.; Magnusson, R. I.; Noorbergen, H.; Karsanaev, S. V.; Maximov, T. C. and Dolman, A. J. Geomorphology and InSAR-tracked surface displacements in an ice-rich yedoma landscape: Frontiers in Earth Science (Lausanne), 9(680565), illus. incl. 3 tables, sketch map, 87 ref., April 2021.

Ice-ridge Yedoma terrain is susceptible to vertical surface displacements by thaw and refreeze of ground ice, and geomorphological processes of mass wasting, erosion and sedimentation. Here we explore the relation between a 3 year data set of InSAR measurements of vertical surface displacements during the thaw season, and geomorphological features in an area in the Indigirka Lowlands, Northeast Siberia. The geomorphology is presented in a geomorphological map, based on interpretation of high resolution visible spectrum satellite imagery, field surveys and available data from paleo-environmental research. The main landforms comprise overlapping drained thaw lake basins and lakes, erosion remnants of Late Pleistocene Yedoma deposits, and a floodplain of a high-sinuosity anastomosing river with ancient river terrace remnants. The spatial distribution of drained thaw lake basins and Yedoma erosion remnants in the study area and its surroundings is influenced by neotectonic movements. The 3 years of InSAR measurement include 2 years of high snowfall and extreme river flooding (2017-2018) and 1 year of modest snowfall, early spring and warm summer (2019). The magnitude of surface displacements varies among the years, and show considerable spatial variation. Distinct spatial clusters of displacement trajectories can be discerned, which relate to geomorphological processes and ground ice conditions. Strong subsidence occurred in particular in 2019. In the wet year of 2017, marked heave occurred at Yedoma plateau surfaces, likely by ice accumulation at the top of the permafrost driven by excess precipitation. The spatial variability of surface displacements is high. This is explored by statistical analysis, and is attributed to the interaction of various processes. Next to ground ice volume change, also sedimentation (peat, colluvial deposition) and shrinkage or swelling of soils with changing water content may have contributed. Tussock tundra areas covered by the extreme 2017 and 2018 spring floods show high subsidence rates and an increase of midsummer thaw depths. We hypothesize that increased flood heights along Siberian lowland rivers potentially induce deeper thaw and subsidence on floodplain margins, and also lowers the drainage thresholds of thaw lakes. Both mechanisms tend to increase floodplain area. This may increase CH4 emission from floodplains, but also may enhance carbon storage in floodplain sedimentary environments.

DOI: 10.3389/feart.2021.680565

2021062872 Brooks, Heather (BGC Engineering, Edmonton, AB, Canada); Doré, Guy and Locat, Ariane. Soil bridging effects within permafrost-supported embankment infrastructure: Journal of Cold Regions Engineering, 35(1), March 2021. Based on Publisher-supplied data.

Accidents, infrastructure closures and reductions in capacity, and delays have occurred and are documented in the literature due to bridge formation, sinkholes, or rapid collapses within embankment infrastructure on permafrost. However, the failure mechanics are not well understood or studied. This paper investigates soil particle position, negative pore-pressure generation, and frozen soil flexure as possible mechanisms for bridging. Published literature and laboratory testing confirmed that soil particle position is a possible mechanism for bridging voids within embankments. Factor of safety equations were developed for (1) tensile stress conditions within a loaded frozen soil beam and (2) tensile stress from matric suction conditions within unfrozen soils over a void. Using published data for common embankment materials, example calculations for bridging via matric suction and frozen soil flexure are presented. All of the presented mechanisms for creating and maintaining bridges are possible, depending on site conditions; however, the probability and consequences of bridge collapse after formation vary widely depending on the mechanism.

DOI: 10.1061/(ASCE)CR.1943-5495.0000232

2021061586 Cao Bin (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Laboratory of Tibetan Plateau Earth System Science, Beijing, China); Li Xin; Feng Min and Zheng Donghai. Quantifying overestimated permafrost extent driven by rock glacier inventory: Geophysical Research Letters, 48(8), Paper no. e2021GL092476, illus., 38 ref., March 28, 2021.

Rock glaciers (RGs) are normally used as "ground-truth" observations to indicate the presence of permafrost, and hence extensively used in training permafrost distribution models. However, the unique structure and composition of RGs enhance ground cooling effects, leading to more favorable conditions for permafrost presence than in adjacent ground. We therefore hypothesized and confirmed that permafrost extent is overestimated using RG-driven models. The results indicate that the permafrost zonation index was overestimated by about 8.4%-13.1% in a model driven by RG observations compared to a model using in situ measurements of permafrost presence/absence. The bias is particularly pronounced in discontinuous permafrost region, where it is thought to be highly sensitive to climate change, resulting in about a 41.8%-90.8% overestimation in permafrost region and 7.0%-18.6% misclassification. In order to better use the large RG datasets available to understand permafrost conditions, we provide a method to correct this bias in a fundamental model. Abstract Copyright (2021). American Geophysical Union. All Rights Reserved.

DOI: 10.1029/2021GL092476

2021061355 Qin Yanhui (Qingdao University of Technology, School of Civil Engineering, Qingdao, China); Wu Tonghua; Zhang Peng; Liu Wenfeng; Xue Shanbin and Guo Zonghe. Spatiotemporal freeze-thaw variations over the Qinghai-Tibet Plateau 1981-2017 from reanalysis: International Journal of Climatology, 41(2), p. 1438-1454, illus. incl. 6 tables, February 2021. Based on Publisher-supplied data.

The thawing and freezing conditions on the Qinghai-Tibet Plateau (QTP) are considered effective indicators that are widely used in ecology, climate change, cold-region engineering design, and permafrost mapping. The purpose of this study is to utilize reanalysis to detect spatial variations in freeze-thaw conditions across the QTP from 1981-2017. From a comparison of five recent reanalysis models (MERRA2: National Aeronautics and Space Administration Modern-Era Reanalysis for Research and Applications, Version 2; ERA: European Center for Medium-Range Weather Forecasts Interim Reanalysis; GLDAS: Global Land Data Assimilation System NOAH; CFS: National Centers for Environmental Prediction Climate Forecast System Reanalysis, Version 2; and CMFD: China Meteorological Forcing Dataset) against existing sparse observations of 2-m surface air temperature (SAT), we find that NASA MERRA2 dataset is the most applicable to the QTP. Then, the MERRA2 SAT dataset was selected for this study and was corrected and validated by utilizing calibration models built from the observed data. The results revealed that the correlation coefficients between the corrected MERRA2 SAT and meteorological station observed data increased from 0.52 to 0.93, 0.49 to 0.90, 0.56 to 0.93, and 0.69 to 0.93 in spring, summer, autumn, and winter, respectively. The corrected parameters performed better in the southern and southeastern portions of the QTP. Finally, we utilize the corrected MERRA2 dataset to develop freeze-thaw indices and evaluate statistical trends. We find that relatively high air freezing indices are one of the important factors for the presence of permafrost in the central and northeastern portions of the QTP. Trends in the air thawing and freezing indices in the permafrost and seasonally frozen ground regions indicate that, from 1981 to 2017 in the permafrost regions, the warming was more significant in the summer than in the other seasons. However, the winter warming rates in permafrost and seasonally frozen ground regions are almost the same. Abstract Copyright (2020), Royal Meteorological Society.

DOI: 10.1002/joc.6849

2021062743 Gao Hongkai (East China Normal University, Key Laboratory of Geographic Information Science, Shanghai, China); Wang Jingjing; Yang Yuzhong; Pan Xicai; Ding Yongjian and Duan, Zheng. Permafrost hydrology of the Qinghai-Tibet Plateau; a review of processes and modeling: Frontiers in Earth Science (Lausanne), 8(576838), 13 p., illus. incl. 1 table, sketch map, 205 ref., January 2021.

Permafrost extends 40% of the Qinghai-Tibet Plateau (QTP), a region which contains the headwaters of numerous major rivers in Asia. As an aquiclude, permafrost substantially controls surface runoff and its hydraulic connection with groundwater. The freeze-thaw cycle in the active layer significantly impacts soil water movement direction, velocity, storage capacity, and hydraulic conductivity. Under the accelerating warming on the QTP, permafrost degradation is drastically altering regional and even continental hydrological regimes, attracting the attention of hydrologists, climatologists, ecologists, engineers, and decision-makers. A systematic review of permafrost hydrological processes and modeling on the QTP is still lacking, however, leaving a number of knowledge gaps. In this review, we summarize the current understanding of permafrost hydrological processes and applications of some permafrost hydrological models of varying complexity at different scales on the QTP. We then discuss the current challenges and future opportunities, including observations and data, the understanding of processes, and model realism. The goal of this review is to provide a clear picture of where we are now and to describe future challenges and opportunities. We concluded that more efforts are needed to conduct long-term field measurements, employ more advanced observation technologies, and develop flexible and modular models to deepen our understanding of permafrost hydrological processes and to improve our ability to predict the future responses of permafrost hydrology to climate changes.

DOI: 10.3389/feart.2020.576838

2021063953 Wologo, Ethan (Montana State University, Department of Land Resources and Environmental Sciences, Bozeman, MT); Shakil, Sarah; Zolkos, Scott; Textor, Sadie; Ewing, Stephanie; Klassen, Jane; Spencer, Robert G. M.; Podgorski, David C.; Tank, Suzanne E.; Baker, Michelle A.; O'Donnell, Jonathan A.; Wickland, Kimberly P.; Foks, Sydney S. W.; Zarnetske, Jay P.; Lee-Cullin, Joseph; Liu Futing; Yang Yuanhe; Kortelainen, Pirkko; Kolehmainen, Jaana; Dean, Joshua F.; Vonk, Jorien E.; Holmes, Robert M.; Pinay, Gilles; Powell, Michaela M.; Howe, Jansen; Frei, Rebecca J.; Bratsman, Samuel P. and Abbott, Benjamin W. Stream dissolved organic matter in permafrost regions shows surprising compositional similarities but negative priming and nutrient effects: Global Biogeochemical Cycles, 35(1), Article e2020GB006719, illus. incl. 1 table, geol. sketch map, 202 ref., January 2021.

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28-day incubations. We incubated late-summer stream water from 23 locations nested in seven northern or high-altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two-way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways. Abstract Copyright (2020). The Authors.

DOI: 10.1029/2020GB006719

2021063025 Burn, Christopher R. (Carleton University, Department of Geography and Environmental Studies, Ottawa, ON, Canada); Cooper, Mark; Morison, Stephen R.; Pronk, Toon and Calder, John H. The Canadlan Federation of Earth Sciences scientific statement on climate change; its impacts in Canada, and the critical role of Earth scientists in mitigation and adaptation: Geoscience Canada, 48(2), p. 59-71 (French sum.), illus. incl. sketch map, 81 ref., 2021.

The Canadian Federation of Earth Sciences (CFES) has issued this statement to summarize the science, effects, and implications of climate change. We highlight the role of Earth scientists in documenting and mitigating climate change, and in managing and adapting to its consequences in Canada. CFES is the coordinated voice of Canada's Earth Sciences community with 14 member organizations representing some 15,000 geoscientists. Our members are drawn from academia, industry, education, and government. The mission of CFES is to ensure decision makers and the public understand the contributions of Earth Science to Canadian society and the economy. Climate change has become a national and global priority for all levels of government. The geological record shows us that the global climate has changed throughout Earth's history, but the current rates of change are almost unprecedented. Over the last 70 years, levels of common greenhouse gases (GHGs) in the atmosphere have steadily increased. Carbon dioxide (CO2) concentration is now 418 parts per million - its highest of the last three million years. The chemical (isotopic) composition of carbon in the atmosphere indicates the increase in GHGs is due to burning fossil fuels. GHGs absorb energy emitted from Earth's surface and re-radiate it back, warming the lower levels of the atmosphere. Climatic adjustments that have recently occurred are, in practical terms, irreversible, but further change can be mitigated by lowering emissions of GHGs. Climate change is amplified by three important Earth system processes and effects. First, as the climate warms evaporation increases, raising atmospheric concentrations of water vapour, itself a GHG - and adding to warming. Second, loss of ice cover from the polar ice sheets and glaciers exposes larger areas of land and open water - leading to greater absorption of heat from the sun. Third, thawing of near-surface permafrost releases additional GHGs (primarily CO2 and methane) during decay of organic matter previously preserved frozen in the ground. Some impacts of climate change are incremental and steadily occurring, such as melting of glaciers and ice sheets, with consequent sea level rise. Others are intermittent, such as extreme weather events, like hurricanes - but are becoming more frequent. Summer water shortages are increasingly common in western Canada as mountain snowpacks melt earlier and summer river flows decline. In northern Canada, warming and thawing of near-surface permafrost has led to deterioration of infrastructure and increased costs for buildings that now require chilled foundations. Other consequences of unchecked climate change include increased coastal erosion, increases in the number and size of wildfires, and reduction in winter road access to isolated northern communities. Reductions in net GHG emissions are urgently required to mitigate the many effects of further climate change. Industrial and public works development projects must now assess the effects of climate change in their planning, design, and management. Cities, municipalities, and rural communities need to plan new residential development carefully to avoid enhanced risk of flooding, coastal erosion, or wildfire. Earth Science knowledge and expertise is integral to exploration and development of new metals and Earth materials required for a carbon-neutral future, and in the capture and storage of CO2 within the Earth. Earth Science is also central to society's adaptation to new climatic regimes and reduction of risks. This includes anticipation, assessment, and management of extreme events, development of new standards and guidelines for geotechnical and engineering practice, and revision to regulations that consider climate change. Geoscientists also have an important role in the education of students and the public on the reasons for necessary action. Canada is uniquely positioned with its strong global geoscientific leadership, its vast landmass, and its northern terrain to effectively leverage research activities around climate change. Geoscience tools and geoscientists' skills will be integral to Canada's preparation for climate change.

DOI: 10.12789/geocanj.2021.48.173

2021062742 Schmidt, Juditha Undine (University of Oslo, Department of Geosciences, Oslo, Norway); Etzelmüller, Bernd; Schuler, Thomas Vikhamar; Magnin, Florence; Boike, Julia; Langer, Moritz and Westermann, Sebastian. Surface temperatures and their influence on the permafrost thermal regime in high-Arctic rock walls on Svalbard: The Cryosphere (Online), 15(5), p. 2491-2509, illus. incl. 7 tables, sketch map, 86 ref., 2021. Includes 2 appendices.

Permafrost degradation in steep rock walls and associated slope destabilization have been studied increasingly in recent years. While most studies focus on mountainous and sub-Arctic regions, the occurring thermo-mechanical processes also play an important role in the high Arctic. A more precise understanding is required to assess the risk of natural hazards enhanced by permafrost warming in high-Arctic rock walls. This study presents one of the first comprehensive datasets of rock surface temperature measurements of steep rock walls in the high Arctic, comparing coastal and near-coastal settings. We applied the surface energy balance model CryoGrid 3 for evaluation, including adjusted radiative forcing to account for vertical rock walls. Our measurements comprise 4 years of rock surface temperature data from summer 2016 to summer 2020. Mean annual rock surface temperatures ranged from -0.6 in a coastal rock wall in 2017/18 to -4.3°C in a near-coastal rock wall in 2019/20. Our measurements and model results indicate that rock surface temperatures at coastal cliffs are up to 1.5°C higher than at near-coastal rock walls when the fjord is ice-free in winter, resulting from additional energy input due to higher air temperatures at the coast and radiative warming by relatively warm seawater. An ice layer on the fjord counteracts this effect, leading to similar rock surface temperatures to those in near-coastal settings. Our results include a simulated surface energy balance with shortwave radiation as the dominant energy source during spring and summer with net average seasonal values of up to 100 W m-2 and longwave radiation being the main energy loss with net seasonal averages between 16 and 39 W m-2. While sensible heat fluxes can both warm and cool the surface, latent heat fluxes are mostly insignificant. Simulations for future climate conditions result in a warming of rock surface temperatures and a deepening of active layer thickness for both coastal and near-coastal rock walls. Our field data present a unique dataset of rock surface temperatures in steep high-Arctic rock walls, while our model can contribute towards the understanding of factors influencing coastal and near-coastal settings and the associated surface energy balance.

DOI: 10.5194/tc-15-2491-2021

2021062741 von Deimling, Thomas Schneider (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Lee, Hanna; Ingeman-Nielsen, Thomas; Westermann, Sebastian; Romanovsky, Vladimir; Lamoureux, Scott; Walker, Donald A.; Chadburn, Sarah; Trochim, Erin; Cai Lei; Nitzbon, Jan; Jacobi, Stephan and Langer, Moritz. Consequences of permafrost degradation for Arctic infrastructure; bridging the model gap between regional and engineering scales: The Cryosphere (Online), 15(5), p. 2451-2471, illus. incl. 3 tables, 77 ref., 2021.

Infrastructure built on perennially frozen ice-rich ground relies heavily on thermally stable subsurface conditions. Climate-warming-induced deepening of ground thaw puts such infrastructure at risk of failure. For better assessing the risk of large-scale future damage to Arctic infrastructure, improved strategies for model-based approaches are urgently needed. We used the laterally coupled 1D heat conduction model CryoGrid3 to simulate permafrost degradation affected by linear infrastructure. We present a case study of a gravel road built on continuous permafrost (Dalton highway, Alaska) and forced our model under historical and strong future warming conditions (following the RCP8.5 scenario). As expected, the presence of a gravel road in the model leads to higher net heat flux entering the ground compared to a reference run without infrastructure and thus a higher rate of thaw. Further, our results suggest that road failure is likely a consequence of lateral destabilisation due to talik formation in the ground beside the road rather than a direct consequence of a top-down thawing and deepening of the active layer below the road centre. In line with previous studies, we identify enhanced snow accumulation and ponding (both a consequence of infrastructure presence) as key factors for increased soil temperatures and road degradation. Using differing horizontal model resolutions we show that it is possible to capture these key factors and their impact on thawing dynamics with a low number of lateral model units, underlining the potential of our model approach for use in pan-Arctic risk assessments. Our results suggest a general two-phase behaviour of permafrost degradation: an initial phase of slow and gradual thaw, followed by a strong increase in thawing rates after the exceedance of a critical ground warming. The timing of this transition and the magnitude of thaw rate acceleration differ strongly between undisturbed tundra and infrastructure-affected permafrost ground. Our model results suggest that current model-based approaches which do not explicitly take into account infrastructure in their designs are likely to strongly underestimate the timing of future Arctic infrastructure failure. By using a laterally coupled 1D model to simulate linear infrastructure, we infer results in line with outcomes from more complex 2D and 3D models, but our model's computational efficiency allows us to account for long-term climate change impacts on infrastructure from permafrost degradation. Our model simulations underline that it is crucial to consider climate warming when planning and constructing infrastructure on permafrost as a transition from a stable to a highly unstable state can well occur within the service lifetime (about 30 years) of such a construction. Such a transition can even be triggered in the coming decade by climate change for infrastructure built on high northern latitude continuous permafrost that displays cold and relatively stable conditions today.

DOI: 10.5194/tc-15-2451-2021

2021062738 Wani, John Mohd (Indian Institute of Technology, Department of Civil Engineering, Roorkee, India); Thayyen, Renoj J.; Ojha, Chandra Shekhar Prasad and Gruber, Stephan. The surface energy balance in a cold and arid permafrost environment, Ladakh, Himalayas, India: The Cryosphere (Online), 15(5), p. 2273-2293, illus. incl. 5 tables, sketch map, 124 ref., 2021.

Recent studies have shown the cold and arid trans-Himalayan region comprises significant areas underlain by permafrost. While the information on the permafrost characteristics of this region started emerging, the governing energy regime is of particular interest. This paper presents the results of a surface energy balance (SEB) study carried out in the upper Ganglass catchment in the Ladakh region of India which feeds directly into the Indus River. The point-scale SEB is estimated using the 1D mode of the GEOtop model for the period of 1 September 2015 to 31 August 2017 at 4727 m a.s.l. elevation. The model is evaluated using field-monitored snow depth variations (accumulation and melting), outgoing long-wave radiation and near-surface ground temperatures and showed good agreement with the respective simulated values. For the study period, the SEB characteristics of the study site show that the net radiation (29.7 W m-2) was the major component, followed by sensible heat flux (-15.6 W m-2), latent heat flux (-11.2 W m-2) and ground heat flux (-0.5 W m-2). During both years, the latent heat flux was highest in summer and lowest in winter, whereas the sensible heat flux was highest in post-winter and gradually decreased towards the pre-winter season. During the study period, snow cover builds up starting around the last week of December, facilitating ground cooling during almost 3 months (October to December), with sub-zero temperatures down to -20°C providing a favourable environment for permafrost. It is observed that the Ladakh region has a very low relative humidity in the range of 43% compared to e.g. ~70% in the European Alps, resulting in lower incoming long-wave radiation and strongly negative net long-wave radiation averaging ~-90 W m-2 compared to -40 W m-2 in the European Alps. Hence, land surfaces at high elevation in cold and arid regions could be overall colder than the locations with higher relative humidity, such as the European Alps. Further, it is found that high incoming short-wave radiation during summer months in the region may be facilitating enhanced cooling of wet valley bottom surfaces as a result of stronger evaporation.

DOI: 10.5194/tc-15-2273-2021

2021066949 Tomczyk, Aleksandra M. (Adam Mickiewicz University, Faculty of Geographical and Geological Sciences, Poznan, Poland); Ewertowski, Marek W. and Carrivick, Jonathan L. Geomorphological impacts of a glacier lake outburst flood in the high arctic Zackenberg River, NE Greenland: Journal of Hydrology, 591, Article no. 125300, illus. incl. 1 table, sketch maps, 85 ref., December 2020.

Glacier lake outburst floods (GLOFs), especially those in the Arctic, can deliver exceptionally high volumes of sediment and solutes to fjords and shallow-marine settings, in comparison to typical seasonal river flows. These sediments and solutes strongly affect coastal geomorphology and aquatic ecosystems, yet are rarely observed. In this study, we have quantified the short-term geomorphological response of the most distal part of the Zackenberg River (northeast Greenland), where it enters Young Sund, to a glacier lake outburst flood that occurred on August 6th 2017. The main aims were to: (1) quantify riverbank and floodplain geomorphology changes that occurred as a consequence of the flood; (2) analyze the spatial patterns of those geomorphological changes and suggest the key controls on them. We used a time-series of very high-resolution UAV-generated images taken on the 5th, 6th, and 8th of August 2017, which enabled us to compare pre- and post-flood fluvial geomorphology. The GLOF induced intense and widespread geomorphological changes, which was surprising because several floods of a similar magnitude have occurred along this river. Approximately 30% of the area of interest experienced changes that were larger than the minimum level of detection (0.15 m). Lateral erosion reached almost 10 m in some places. The total volume loss from bank erosion was at least 26,561 m3 (± 14%), whereas the deposition was at least 7745 m3 (± 39%). Such an intensive geomorphological response resulted from a combination of factors; namely: (1) bank geometry; (2) composition of bank material; (3) time of occurrence of the event; (4) presence of permafrost; (6) channel geometry; and (7) multitude and diversity of geomorphological processes. We speculate the severity of the geomorphological impact relative to that from previous floods could have been due to warming air temperatures that provided sediment from thawed permafrost, and to an aggrading delta that raised the river base level. Overall, we contend that climate warming will not only make outburst floods from glaciers more likely but that those floods will achieve more geomorphological work with mechanical erosion of permafrost. Erosion and gravitational failures during future flood events will perhaps become even more widespread and intense.

DOI: 10.1016/j.jhydrol.2020.125300

2021061354 Yao Jimin (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Gu Lianglei; Yang Cheng; Chen Hao; Wang Jiemin; Ding Yongjian; Li Ren; Zhao Lin; Xiao Yao; Qiao Yongping; Shi Jianzong and Chen Caiping. Estimation of surface energy fluxes in the permafrost region of the Tibetan Plateau based on in situ measurements and the surface energy balance system model: International Journal of Climatology, 40(13), p. 5783-5800, illus. incl. 3 tables, November 15, 2020. Based on Publisher-supplied data.

The surface energy balance is a key issue in land surface process research and important for studies of climate and hydrology. In this paper, the surface energy fluxes (net radiation, ground heat flux, sensible heat flux and latent heat flux) at the Tanggula (TGL) and Xidatan (XDT) sites were measured and the distributions of the regional surface energy fluxes on the Tibetan Plateau were obtained using a revised surface energy balance system (SEBS) model. The results show that the surface energy fluxes have obvious seasonal variations. At both sites, the sensible heat flux is highest in spring and lowest in summer, and the latent heat flux is highest in summer and lowest in winter. The high elevation, snow cover, freeze-thaw process, precipitation, vegetation and soil texture are important influencing factors for land surface energy fluxes. The time-phase difference between the net radiation and ground heat flux for bare soils is estimated to be 2-3 hr. The ratio of ground heat flux and net radiation ranged from approximately 0.18 to 0.33, and a parameterization scheme for the remote sensing of ground heat flux over the Tibetan Plateau bare soil in summer is developed. The simulation results of the regional surface energy fluxes show that the distributions of surface parameters, such as vegetation, soil texture and soil moisture content, are important for understanding regional changes in the surface energy fluxes. Abstract Copyright (2020), Royal Meteorological Society.

DOI: 10.1002/joc.6551

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2021068788 Dabrowski, Jessica StephanieRadium isotopes and radon-222 as tracers of sediment-water interaction in Arctic coastal and lacustrine environments: 108 p., illus. incl. 8 tables, 227 ref., Master's, 2020, Massachusetts Institute of Technology, Cambridge, MA. Joint MIT/WHOI Program.

Arctic marine and lacustrine systems are experiencing rapid warming due to climate change. These changes are especially important at the interface between sediments and surface waters because they are hotspots for biogeochemical transformations such as redox reactions, nutrient consumption and regeneration, organic matter leaching and degradation, and mineral weathering. Radium isotopes (223Ra, 224Ra, 226Ra, 228Ra) and radon-222, naturally occurring radioactive isotopes produced in sediments, are well-suited as tracers of nutrients, trace metals, and organic matter cycling processes at the sediment-water interface. In this thesis, I have applied radon-222 and the quartet of radium isotopes to study fundamental processes in subarctic lakes and on the Arctic continental shelf. First, radon-222 is used to quantify groundwater discharge into a shallow, tundra lake on the Yukon-Kuskokwim Delta in Alaska in summer of 2017. Radon-derived groundwater fluxes were then paired with methane (CH4) measurements to determine delivery rates of methane into the lake via groundwater. Groundwater CH4 fluxes significantly exceeded diffusive air-water fluxes from the lake to the atmosphere, suggesting that groundwater is an important source of CH4 to Arctic lakes and may drive observed CH4 emissions. Higher CH4 emissions were observed compared to those reported previously in high latitude lakes, like due to higher CH4 concentrations in groundwater. These findings indicate that deltaic lakes across warmer permafrost regions may act as important hotspots for methane release across Arctic landscapes. Then, the quartet of radium isotopes is used to study the impacts of storms and sea ice formation as drivers of sediment-water interaction on the Alaskan Beaufort shelf. The timeseries presented in this study is among the first to document the combined physical and chemical signals of winter water formation in the Beaufort Sea, made possible by repeat occupations of the central Beaufort shelf. Radium measurements are combined with inorganic nitrogen and hydrographic measurements to elucidate the episodic behavior of winter water formation and its ability to drive exchange with bottom sediments during freeze-up.

DOI: 10.1575/1912/26239

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2021062883 Carson, Eric (Wisconsin Geological and Natural History Survey, Madison, WI); Ives, Libby; Stolzman, Kacie C. and Rawling, J. Elmo, III. Tracking the evolution of glacial lakes Yahara and Scuppernong, south-central Wisconsin, USA [abstr.]: in Geological Society of America, North-Central Section, South-Central Section, 55th annual meeting, Abstracts with Programs - Geological Society of America, 53(3), Abstract no. 1-1, April 2021. Meeting: Geological Society of America, North-Central Section, South-Central Section, 55th annual meeting, April 18-20, 2021, World Wide Web.

As the MIS 2 Green Bay Lobe retreated to the northeast from its maximum position in south-central WI, glacial Lakes Yahara (gLY) and Scuppernong (gLS) formed as proglacial lakes fed by meltwater from the retreating ice sheet. The lakes persisted until the sills that controlled drainage to the south downcut sufficiently for lake level to drop, forming modern lakes in the Madison area within the footprint of gLY and completing draining gLS. While the general geologic history of the lakes has been documented, little chronologic control exists to constrain either lake and the precise extent of gLS is poorly understood. Cores from four locations within the gLY basin capture the stratigraphic shift from lacustrine to marsh sediment as lake level fell, and the laminated lake sediment has been found to contain abundant plant macrofossils of riparian species as well as gastropods and bivalves. Initial AMS radiocarbon ages indicate that gLY formed sometime prior to ~18.2 ka (Beta-563548), and that the lake ceased to exist in the timeframe of ~11.7 to ~11.2 ka (Beta-563547 and Beta-563550, respectively). These age constraints will continue to be refined by additional coring and radiocarbon dating specific to gLY. Mapping of gLS and associated coring suggests that the lake was likely less extensive than previously hypothesized. The proglacial landscape was likely very dynamic, evidenced by different elevations of ice-contact deltas associated recessional-phase moraines. Lake levels likely fluctuated widely during retreat of the Green Bay Lobe due to complex interactions between meltwater discharge; complex lake basin shape in the low-relief, drumlinized landscape; and shifting outlets. The lowest areas of this landscape contain lacustrine sediments overlain by marsh sediments. These areas had active lacustrine deposition until at least ~9.1 ka (Beta-563553), and transitioned to marsh by ~6.8 ka (Beta-563552). Ice-wedge polygons are common on the gLS lake plain in areas that are higher on the landscape and not covered by marsh sediments. Prior studies indicate that permafrost conditions were pervasive in southern Wisconsin only up until ~15.0 ka. Therefore, most of the sediments were likely deposited and exposed subaerially prior to that time, which is consistent with deposition in gLS beginning prior to ~17.9 ka (Beta-548564).

DOI: 10.1130/abs/2021NC-362665

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2021064038 Pearce, John M. (U. S. Geological Survey) and Van Hemert, Caroline R. U. S. Geological Survey Arctic ecosystem assessments: Fact Sheet - U. S. Geological Survey, Rep. No. FS 2021-3016, 2 p., illus., March 2021.

The U.S Geological Survey (USGS) conducts natural hazard and resource assessments of the Earth's ecosystems and the response of those ecosystems to environmental change, human activities, and land use. Arctic regions of Alaska are important for cultural and economic sustainability and host a wide variety of wildlife species, many of which are of conservation and management interest to the U.S. Department of the Interior. The USGS and collaborators provide information about Arctic ecosystems that are used by Arctic residents, management agencies, and industry. This fact sheet describes recent USGS assessments on focal species and important topic areas in the Arctic.

DOI: 10.3133/fs20213016

2021064020 Waldrop, Mark P. (U. S. Geological Survey); Anderson, Lesleigh; Dornblaser, Mark; Erikson, Li H.; Gibbs, Ann E.; Herman-Mercer, Nicole M.; James, Stephanie R.; Jones, Miriam C.; Koch, Joshua C.; Leewis, Mary-Cathrine; Manies, Kristen L.; Minsley, Burke J.; Pastick, Neal J.; Patil, Vijay; Urban, Frank; Walvoord, Michelle A.; Wickland, Kimberly P. and Zimmerman, Christian. USGS permafrost research determines the risks of permafrost thaw to biologic and hydrologic resources: Fact Sheet - U. S. Geological Survey, Rep. No. FS 2020-3058, 6 p., illus. incl. sketch maps, 5 ref., January 2021.

The U.S. Geological Survey (USGS), in collaboration with university, Federal, Tribal, and independent partners, conducts fundamental research on the distribution, vulnerability, and importance of permafrost in arctic and boreal ecosystems. Scientists, land managers, and policy makers use USGS data to help make decisions for development, wildlife habitat, and other needs. Native villages and cities can forecast landscape change and where soils are vulnerable to thaw with more certainty. The scientific community can use USGS data to develop scenarios of future permafrost change.

DOI: 10.3133/fs20203058

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