Permafrost Monthly Alerts (PMAs)

2020080615 Li Xiangying (Hohai University, College of Hydrology and Water Resources, Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Nanjing, China); Ding Yongjian; Han Tianding; Sillanpaa, Mika; Jing Zhefan; You Xiaoni; Liu Sha; Yang Chuanyang; Yu Congrong and Li Guoyu. Seasonal and interannual changes of river chemistry in the source region of Yellow River, Tibetan Plateau: Applied Geochemistry, 119, Article 104638, illus. incl. 4 tables, sketch map, 73 ref., August 2020.

The seasonal and annual processes of river chemistry as well as chemical weathering and controlling factors were examined in the source region of Yellow River (SRYE) during 2013-2015. River discharge exhibited strong seasonality and was dominated by precipitation and/or groundwater. Sediment concentrations were positively related to discharge, and the dominant sediment-producing area was this area from JM to JG owing to large precipitation and strong erosion. The dominant cations and anions were Na⁺, Ca²⁺ and HCO₃^-, and concentrations of most ions displayed obvious seasonality with a negative relationship with discharge, suggesting a hydrological control on river chemistry. Comparison of ion concentrations suggest that the regional climate and land surface affect the soil/rock erosion and solute release. River chemistry was dominated by the weathering of carbonate and silicate. HCO₃^-, Ca²⁺ and Mg²⁺ were primarily derived from calcite and dolomite weathering, and Na⁺ and K⁺ mainly came from silicate weathering. CWR and CatWR showed strong seasonality and were closely related to discharge, air temperature, precipitation and PER, suggesting that chemical weathering rates are dominated by lithology, discharge and precipitation. The sediment and solute yields ranged from 25,110 to 97,270 t km^-2 a^-1 and 22,610 to 27,800 t km^-2 a^-1 respectively in the SRYE (at TNH), where CWR and CatWR were 5.42-7.63 t km^-2 a^-1 and 1.20-2.62 t km^-2 a^-1 respectively. Higher CatWR in the SRYE than those in other basins with higher specific discharge implies that silicate weathering is more sensitive to permafrost degradation.

DOI: 10.1016/j.apgeochem.2020.104638

2020079384 Magnusson, Runa I. (Wageningen University and Research, Plant Ecology and Nature Conservation Group, Wageningen, Netherlands); Limpens, Juul; Huissteden, Jacobus; Kleijn, David; Maximov, Trofim C.; Rotbarth, Ronny; Sass-Klaassen, Ute and Heijmans, Monique M. P. D. Rapid vegetation succession and coupled permafrost dynamics in arctic thaw ponds in the Siberian Lowland tundra: Journal of Geophysical Research: Biogeosciences, 125(7), Article e2019JG005618, illus. incl. 1 table, 1 table, 100 ref., July 2020.

Thermokarst features, such as thaw ponds, are hotspots for methane emissions in warming lowland tundra. Presently we lack quantitative knowledge on the formation rates of thaw ponds and subsequent vegetation succession, necessary to determine their net contribution to greenhouse gas emissions. This study sets out to identify development trajectories and formation rates of small-scale (<100 m²), shallow arctic thaw ponds in north-eastern Siberia. We selected 40 ponds of different age classes based on a time-series of satellite images and measured vegetation composition, microtopography, water table, and thaw depth in the field and measured age of colonizing shrubs in thaw ponds using dendrochronology. We found that young ponds are characterized by dead shrubs, while older ponds show rapid terrestrialization through colonization by sedges and Sphagnum moss. While dead shrubs and open water are associated with permafrost degradation (lower surface elevation, larger thaw depth), sites with sedge and in particular Sphagnum display indications of permafrost recovery. Recruitment of Betula nana on Sphagnum carpets in ponds indicates a potential recovery toward shrub-dominated vegetation, although it remains unclear if and on what timescale this occurs. Our results suggest that thaw ponds display potentially cyclic vegetation succession associated with permafrost degradation and recovery. Pond formation and initial colonization by sedges can occur on subdecadal timescales, suggesting rapid degradation and initial recovery of permafrost. The rates of formation and recovery of small-scale, shallow thaw ponds have implications for the greening/browning dynamics and carbon balance of this ecosystem. Abstract Copyright (2020). The Authors.

DOI: 10.1029/2019JG005618

2020079378 Philben, Michael (Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN); Tas, Neslihan; Chen, Hongmei; Wullschleger, Stan D.; Kholodov, Alexander; Graham, David E. and Gu, Baohua. Influences of hillslope biogeochemistry on anaerobic soil organic matter decomposition in a tundra watershed: Journal of Geophysical Research: Biogeosciences, 125(7), Article e2019JG005512, illus., 47 ref., July 2020.

We investigated rates and controls on greenhouse gas (CO₂ and CH₄) production in two contrasting water-saturated tundra soils within a permafrost-affected watershed near Nome, Alaska, United States. Three years of field sample analysis have shown that soil from a fen-like area in the toeslope of the watershed had higher pH and higher porewater ion concentrations than soil collected from a bog-like peat plateau at the top of the hillslope. The influence of these contrasting geochemical and topographic environments on CO₂ and CH₄ production was tested in soil microcosms by incubating both the organic- and mineral-layer soils anaerobically for 55 days. Nitrogen (as NH₄Cl) was added to half of the microcosms to test potential effects of N limitation on microbial greenhouse gas production. We found that the organic toeslope soils produced more CO₂ and CH₄, fueled by higher pH and higher concentrations of water-extractable organic C (WEOC). Our results also indicate N limitation on CO₂ production in the peat plateau soils but not the toeslope soils. Together these results suggest that the weathering and leaching of ions and nutrients from tundra hillslopes can increase the rate of anaerobic soil organic matter decomposition in downslope soils by (1) increasing the pH of soil porewater; (2) providing bioavailable WEOC and fermentation products such as acetate; and (3) relieving microbial N limitation through nutrient runoff. We conclude that the soil geochemistry as mediated by landscape position is an important factor influencing the rate and magnitude of greenhouse gas production in tundra soils. Abstract Copyright (2020). American Geophysical Union. All Rights Reserved. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

DOI: 10.1029/2019JG005512

2020080496 Anders, Katharina (Heidelberg University, Institute of Geography, 3D Geospatial Data Processing Group, Heidelberg, Germany); Marx, Sabrina; Boike, Julia; Herfort, Benjamin; Wilcox, Evan James; Langer, Moritz; Marsh, Philip and Höfle, Bernhard. Multitemporal terrestrial laser scanning point clouds for thaw subsidence observation at Arctic permafrost monitoring sites: Earth Surface Processes and Landforms, 45(7), p. 1589-1600, illus. incl. 3 tables, sketch map, 40 ref., June 15, 2020.

This paper investigates different methods for quantifying thaw subsidence using terrestrial laser scanning (TLS) point clouds. Thaw subsidence is a slow (millimetre to centimetre per year) vertical displacement of the ground surface common in ice-rich permafrost-underlain landscapes. It is difficult to quantify thaw subsidence in tundra areas as they often lack stable reference frames. Also, there is no solid ground surface to serve as a basis for elevation measurements, due to a continuous moss-lichen cover. We investigate how an expert-driven method improves the accuracy of benchmark measurements at discrete locations within two sites using multitemporal TLS data of a 1-year period. Our method aggregates multiple experts' determination of the ground surface in 3D point clouds, collected in a web-based tool. We then compare this to the performance of a fully automated ground surface determination method. Lastly, we quantify ground surface displacement by directly computing multitemporal point cloud distances, thereby extending thaw subsidence observation to an area-based assessment. Using the expert-driven quantification as reference, we validate the other methods, including in-situ benchmark measurements from a conventional field survey. This study demonstrates that quantifying the ground surface using 3D point clouds is more accurate than the field survey method. The expert-driven method achieves an accuracy of 0.1±0.1 cm. Compared to this, in-situ benchmark measurements by single surveyors yield an accuracy of 0.4±1.5 cm. This difference between the two methods is important, considering an observed displacement of 1.4 cm at the sites. Thaw subsidence quantification with the fully automatic benchmark-based method achieves an accuracy of 0.2±0.5 cm and direct point cloud distance computation an accuracy of 0.2±0.9 cm. The range in accuracy is largely influenced by properties of vegetation structure at locations within the sites. The developed methods enable a link of automated quantification and expert judgement for transparent long-term monitoring of permafrost subsidence. Copyright 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

DOI: 10.1002/esp.4833

2020074102 Cuozzo, Nicolas (University of Washington, Department of Earth and Space Sciences, Seattle, WA); Sletten, Ronald S.; Hu, Yan; Liu, Lu; Teng, Fang-Zhen and Hagedorn, Birgit. Silicate weathering in antarctic ice-rich permafrost; insights using magnesium isotopes: in The continents; origin, evolution and interactions with other reservoirs (Teng, Fang-Zhen, editor; et al.), Geochimica et Cosmochimica Acta, 278, p. 244-260, illus. incl. 4 tables, sketch map, 87 ref., June 1, 2020.

This study reports that substantial chemical weathering occurs at subzero temperatures in ice-and-salt-rich permafrost in the McMurdo Dry Valleys, Antarctica. Chemical weathering is documented in a 30.0-m core collected in Beacon Valley by measuring the ionic composition, pH, and Mg isotopes of water extracted from thawed ice-rich sediment. Evidence of rock weathering is revealed by coinciding increases in the Mg isotopic composition and pH values. The primary factor that controls weathering is the salt content that leads to unfrozen brine; this is most apparent in the upper 7.0 m where salt content is high, temperatures rise above -21°C and modeled unfrozen water reaches up to 4.0% of ice-content. In the upper 7.0 m, up to 60% of soluble Mg in the thawed permafrost ice is sourced from Ferrar Dolerite (d²⁶Mg=-0.22±0.07 ppm) weathering, resulting in d²⁶Mg values ranging from of -0.82±0.05 ppm to -0.64±0.05 ppm. Below 7.0 m, temperatures remain below -21°C, unfrozen water is less than 2.0% of ice-content, and on average, 5% of soluble Mg is sourced from dolerite weathering with d²⁶Mg values ranging from -1.05±0.05 ppm to -0.76±0.05 ppm. Regions of the core that are modeled to have no unfrozen water show little or no evidence of chemical weathering and relatively constant d²⁶Mg values close to Taylor Glacier and Beacon Valley snowfall values (-0.93±0.06 ppm). This study demonstrates that significant chemical weathering occurs at subzero temperatures in permafrost where liquid brines form.

DOI: 10.1016/j.gca.2019.07.031

2020076795 Dyonisius, M. N. (University of Rochester, Department of Earth and Environmental Sciences, Rochester, NY); Petrenko, V. V.; Smith, A. M.; Hua, Q.; Yang, B.; Schmitt, J.; Beck, J.; Seth, B.; Bock, M.; Hmiel, B.; Vimont, I.; Menking, J. A.; Shackleton, S. A.; Baggenstos, D.; Bauska, T. K.; Rhodes, R. H.; Sperlich, P.; Beaudette, R.; Harth, C.; Kalk, M.; Brook, E. J.; Fischer, H.; Severinghaus, J. P. and Weiss, R. F. Old carbon reservoirs were not important in the deglacial methane budget: Science, 367(6480), p. 907-910, illus. incl. 1 table, 40 ref., February 21, 2020.

Permafrost and methane hydrates are large, climate-sensitive old carbon reservoirs that have the potential to emit large quantities of methane, a potent greenhouse gas, as the Earth continues to warm. We present ice core isotopic measurements of methane (d¹⁴C, d¹³C, and dD) from the last deglaciation, which is a partial analog for modern warming. Our results show that methane emissions from old carbon reservoirs in response to deglacial warming were small (<19 teragrams of methane per year, 95% confidence interval) and argue against similar methane emissions in response to future warming. Our results also indicate that methane emissions from biomass burning in the pre-Industrial Holocene were 22 to 56 teragrams of methane per year (95% confidence interval), which is comparable to today.

DOI: 10.1126/science.aax0504

2020080075 Bliss, Andrew (Colorado State University, Department of Anthropology, Fort Collins, CO); Hock, Regine; Wolken, Gabriel; Whorton, Erin; Aubry-Wake, Caroline; Braun, Juliana; Gusmeroli, Alessio; Harrison, Will; Hoffman, Andrew; Liljedahl, Anna and Zhang, Jing. Glaciers and climate of the upper Susitna Basin, Alaska: Earth System Science Data (ESSD), 12(1), p. 403-427, illus. incl. 8 tables, sketch maps, 31 ref., 2020.

Extensive field observations were conducted in the Upper Susitna basin, a 13 289 km² glacierized catchment in central Alaska in 2012-2014. This paper describes the comprehensive data set of meteorological, glacier mass balance, snow cover, and soil measurements, as well as the data collection and processing. Results are compared to similar observations from the 1980s. Environmental lapse rates measured with weather stations between about 1000 and 2000 m a.s.l. were significantly lower over the glaciers than the non-glacierized areas. Glacier-wide mass balances shifted from close to balanced in 1981-1983 to less than -1.5 m w.e. yr^-1 in 2012-2014. Winter snow accumulation measured with ablation stakes on the glaciers closely matched observations from helicopter-borne radar. Soil temperature measurements across the basin showed that there was no permafrost in the upper 1 m of the soil column. The data produced by this study are available at: URL: https://doi.org/10.14509/30138 (Bliss et al., 2019) and will be useful for hydrological and glaciological studies including modeling efforts.

DOI: 10.5194/essd-12-403-2020

2020080524 Gavrilov, Anatoliy (Lomonosov Moscow State University, Faculty of Geology, Moscow, Russian Federation); Pavlov, Vladimir; Fridenberg, Alexandr; Boldyrev, Mikhail; Khilimonyuk, Vanda; Pizhankova, Elena; Buldovich, Sergey; Kosevich, Natalia; Alyautdinov, Ali; Ogienko, Mariia; Roslyakov, Alexander; Cherbunina, Maria and Ospennikov, Evgeniy. The current state and 125 kyr history of permafrost on the Kara Sea shelf; modeling constraints: The Cryosphere (Online), 14(6), p. 1857-1873, illus. incl. 7 tables, 88 ref., 2020.

The evolution of permafrost on the Kara Shelf is reconstructed for the past 125 kyr. The work includes zoning of the shelf according to geological history; compiling sea level and ground temperature scenarios within the distinguished zones; and modeling to evaluate the thickness of permafrost and the distribution of frozen, cooled and thawed deposits. Special attention is given to the scenarios of the evolution of ground temperature in key stages of history that determined the current state of the Kara shelf permafrost zone: characterization of the extensiveness and duration of the existence of the sea during stage 3 of the marine oxygen isotope stratigraphy (MIS-3), the spread of glaciation and dammed basins in MIS-2. The present shelf is divided into areas of continuous, discontinuous-to-sporadic and sporadic permafrost. Cooled deposits occur at the western and northwestern water zones and correspond to areas of MIS-2 glaciation. Permafrost occurs in the periglacial domain that is within a zone of modern sea depth from 0 to 100 m, adjacent to the continent. The distribution of permafrost is mostly sporadic in the southwest of this zone, while it is mostly continuous in the northeast. The thickness of permafrost does not exceed 100 m in the southeast and ranges from 100 to 300 m in the northeast. Thawed deposits are confined to the estuaries of large rivers and the deepwater part of the St. Anna trench. The modeling results are correlated to the available field data and are presented as a geocryological map. The formation of frozen, cooled and thawed deposits of the region is inferred to depend on the spread of ice sheets, sea level, and duration of shelf freezing and thawing periods.

DOI: 10.5194/tc-14-1857-2020

2020080265 Gruber, Stephan (Carleton University, Department of Geography and Environmental Studies, Ottawa, ON, Canada). Ground subsidence and heave over permafrost; hourly time series reveal interannual, seasonal and shorter-term movement caused by freezing, thawing and water movement: The Cryosphere (Online), 14(4), p. 1437-1447, illus. incl. 2 tables, 51 ref., 2020.

Heave and subsidence of the ground surface can offer insight into processes of heat and mass transfer in freezing and thawing soils. Additionally, subsidence is an important metric for monitoring and understanding the transformation of permafrost landscapes under climate change. Corresponding ground observations, however, are sparse and episodic. A simple tilt-arm apparatus with logging inclinometer has been developed to measure heave and subsidence of the ground surface with hourly resolution and millimeter accuracy. This contribution reports data from the first two winters and the first full summer, measured at three sites with contrasting organic and frost-susceptible soils in warm permafrost. The patterns of surface movement differ significantly between sites and from a prediction based on the Stefan equation and observed ground temperature. The data are rich in features of heave and subsidence that are several days to several weeks long and that may help elucidate processes in the ground. For example, late-winter heave followed by thawing and subsidence, as reported in earlier literature and hypothesized to be caused by infiltration and refreezing of water into permeable frozen ground, has been detected. An early-winter peak in heave, followed by brief subsidence, is discernible in a previous publication but so far has not been interpreted. An effect of precipitation on changes in surface elevation can be inferred with confidence. These results highlight the potential of ground-based observation of subsidence and heave as an enabler of progress in process understanding, modeling and interpretation of remotely sensed data.

DOI: 10.5194/tc-14-1437-2020

2020080523 Mamot, Philipp (Technical University of Munich, Chair of Landslide Research, Munich, Germany); Weber, Samuel; Lanz, Maximilian and Krautblatter, Michael. The influence of mica-rich rocks on the shear strength of ice-filled discontinuities: The Cryosphere (Online), 14(6), p. 1849-1855, illus. incl. sketch map, 25 ref., 2020.

A temperature- and stress-dependent failure criterion for ice-filled rock (limestone) joints was proposed in 2018 as an essential tool to assess and model the stability of degrading permafrost rock slopes. To test the applicability to other rock types, we conducted laboratory tests with mica schist and gneiss, which provide the maximum expected deviation of lithological effects on the shear strength due to strong negative surface charges affecting the rock-ice interface. Retesting 120 samples at temperatures from -10 to -0.5°C and normal stress of 100 to 400kPa, we show that even for controversial rocks the failure criterion stays unaltered, suggesting that the failure criterion is transferable to mostly all rock types.

DOI: 10.5194/tc-14-1849-2020

2020080519 Reinosch, Eike (Technische Universität Braunschweig, Institute of Geodesy and Photogrammetry, Braunschweig, Germany); Buckel, Johannes; Dong Jie; Gerke, Markus; Baade, Jussi and Riedel, Björn. InSAR time series analysis of seasonal surface displacement dynamics on the Tibetan Plateau: The Cryosphere (Online), 14(5), p. 1633-1650, illus. incl. 3 tables, 70 ref., 2020.

Climate change and the associated rise in air temperature have affected the Tibetan Plateau to a significantly stronger degree than the global average over the past decades. This has caused deglaciation, increased precipitation and permafrost degradation. The latter in particular is associated with increased slope instability and an increase in mass-wasting processes, which pose a danger to infrastructure in the vicinity. Interferometric synthetic aperture radar (InSAR) analysis is well suited to study the displacement patterns driven by permafrost processes, as they are on the order of millimeters to decimeters. The Nyainqentanglha Range on the Tibetan Plateau lacks high vegetation and features relatively thin snow cover in winter, allowing for continuous monitoring of those displacements throughout the year. The short revisit time of the Sentinel-1 constellation further reduces the risk of temporal decorrelation, making it possible to produce surface displacement models with good spatial coverage. We created three different surface displacement models to study heave and subsidence in the valleys, seasonally accelerated sliding and linear creep on the slopes. Flat regions at Nam Co are mostly stable on a multiannual scale but some experience subsidence. We observe a clear cycle of heave and subsidence in the valleys, where freezing of the active layer followed by subsequent thawing cause a vertical oscillation of the ground of up to a few centimeters, especially near streams and other water bodies. Most slopes of the area are unstable, with velocities of 8 to 17 mm yr^-1. During the summer months surface displacement velocities more than double on most unstable slopes due to freeze-thaw processes driven by higher temperatures and increased precipitation. Specific landforms, most of which have been identified as rock glaciers, protalus ramparts or frozen moraines, reach velocities of up to 18 cm yr^-1. Their movement shows little seasonal variation but a linear pattern indicating that their displacement is predominantly gravity-driven.

DOI: 10.5194/tc-14-1633-2020

2020080261 Rode, Matthias (University of Graz, Institute of Geography and Regional Science, Graz, Austria); Sass, Oliver; Kellerer-Pirklbauer, Andreas; Schnepfleitner, Harald and Gitschthaler, Christoph. Permafrost distribution and conditions at the headwalls of two receding glaciers (Schladming and Hallstatt Glaciers) in the Dachstein Massif, Northern Calcareous Alps, Austria: The Cryosphere (Online), 14(4), p. 1173-1186, illus. incl. 2 tables, sketch map, 79 ref., 2020.

Permafrost distribution in rock walls surrounding receding glaciers is an important factor in rock stability and rock wall retreat. We investigated bedrock permafrost distribution in the Dachstein Massif, Austria, reaching up to 2995 m a.s.l. The occurrence, thickness and thermal regime of permafrost at this partly glaciated mountain massif are scarcely known. We applied a multi-method approach with continuous ground surface and near-surface temperature monitoring (GST), measurement of the bottom temperature of the winter snow cover (BTS), electrical resistivity tomography (ERT), airborne photogrammetry, topographic maps, visual observations, and field mapping. Our research focused on several steep rock walls consisting of massive limestone above receding glaciers exposed to different slope aspects at elevations between ca. 2600 and 2700 m a.s.l. We aimed to quantify the distribution and conditions of bedrock permafrost particularly at the transition zone between the present glacier surface and the adjacent rock walls. According to our ground temperature data, permafrost is mainly found at north-facing rock walls. At south-east-facing rock walls, permafrost is probable only in very favorable cold conditions at radiation-sheltered higher elevations (>2700m a.s.l.). ERT measurements reveal high resistivities (>30,000Wm depth at north-exposed slopes. Deducted from laboratory studies and additional small-scale ERT measurements, these values indicate permafrost existence. Permafrost bodies were found at several rock walls independent of investigated slope orientation; however, particularly large permafrost bodies were found at north-exposed sites. Furthermore, at vertical survey lines, a pronounced imprint of the former Little Ice Age (LIA) ice margin was detected. Resistivities above and below the LIA line are markedly different. At the LIA glacier surface, the highest resistivities and lowest active-layer thicknesses were observed. The active-layer thickness increases downslope from this zone. Permafrost below the LIA line could be due to permafrost aggradation or degradation; however, the spatial patterns of frozen rock point to permafrost aggradation following glacier surface lowering or retreat. This finding is significant for permafrost and cirque erosion studies in terms of frost-influence weathering in similar high-mountain settings.

DOI: 10.5194/tc-14-1173-2020

2020080263 Yang, Ji-Woong (Seoul National University, School of Earth and Environmental Sciences, Seoul, South Korea); Ahn, Jinho; Iwahana, Go; Han, Sangyoung; Kim, Kyungmin and Fedorov, Alexander. The reliability of gas extraction techniques for analysing aCH₄ and aN₂O compositions in gas trapped in permafrost ice wedges: The Cryosphere (Online), 14(4), p. 1311-1324, illus., 26 ref., 2020. Includes appendix.

Methane and nitrous oxide compositions in ground ice may provide information on their production mechanisms in permafrost. However, existing gas extraction methods have not been well tested. We tested conventional wet and dry gas extraction methods using ice wedges from Alaska and Siberia, finding that both methods can extract gas from the easily extractable parts of the ice (e.g. gas bubbles) and yield similar results for mixing ratios. We also found insignificant effects of microbial activity during wet extraction. However, both techniques were unable to fully extract gas from the ground ice, presumably because gas molecules adsorbed onto or enclosed in soil aggregates are not easily extractable. Estimation of gas production in a subfreezing environment of permafrost should consider such incomplete gas extraction.

DOI: 10.5194/tc-14-1311-2020

2020080525 Zhang Jiahua (Chinese University of Hong Kong, Earth System Science Program, Hong Kong, China); Liu Lin and Hu Yufeng. Global positioning system interferometric reflectometry (GPS-IR) measurements of ground surface elevation changes in permafrost areas in northern Canada: The Cryosphere (Online), 14(6), p. 1875-1888, illus. incl. 4 tables, sketch map, 48 ref., 2020.

Global Positioning System interferometric reflectometry (GPS-IR) is a relatively new technique which uses reflected GPS signals to measure surface elevation changes to study frozen-ground dynamics. At present, more than 200 GPS stations are operating continuously in the Northern Hemisphere permafrost areas, which were originally designed and maintained for tectonic and ionospheric studies. However, only one site in Utqiagvik, Alaska (formerly Barrow), was assessed to be usable for studying permafrost by GPS-IR. Moreover, GPS-IR has high requirements on the ground surface condition, which needs to be open, flat, and homogeneous. In this study, we screen three major GPS networks in Canada and identify 12 out of 38 stations located in permafrost areas as useful ones where reliable GPS-IR measurements can be obtained. We focus on the five Canadian Active Control System stations and obtain their daily GPS-IR surface elevation changes. We find that the ground surface subsided in Alert, Resolute Bay, and Repulse Bay respectively by 0.61±0.04/cm yr^-1 (2012-2018), 0.70±0.02 cm yr⁼¹ (2003-2014), and o.26 ± 0.05cm yr⁼¹ (2014-2019). At the other two sites of Baker Lake and Iqaluit, the trends are not statistically significant. The linear trends of deformation were negatively correlated with those of thaw indices in Alert, Resolute Bay, and Repulse Bay. Furthermore, in Resolute Bay, we also find that the end-of-thaw elevations during 2003-2012 were highly negatively correlated with the square root of thaw indices. This study is the first one using multiple GPS stations to study permafrost by GPS-IR. It highlights the multiple useful GPS stations in northern Canada, offering multi-year, continuous, and daily GPS-IR surface deformation, which provides new insights into frozen-ground dynamics at various temporal scales and across a broad region.

DOI: 10.5194/tc-14-1875-2020

2020075629 Ji Xiaowen (Nanjing University, Laboratory of Pollution Control and Resource Reuse, Nanjing, China); Abakumov, Evgeny; Polyako, Vyacheslav; Xie Xianchuan and Wei Dongyang. The ecological impact of mineral exploitation in the Russian Arctic; a field-scale study of polycyclic aromatic hydrocarbons (PAHs) in permafrost-affected soils and lichens of the Yamal-Nenets autonomous region: Environmental Pollution (1987), 255(Part 1), Article 113239, illus. incl. sketch maps, 73 ref., December 2019.

Forty soil and lichen samples and sixteen soil horizon samples were collected in the mining and surrounding areas of the Yamal-Nenets autonomous region (Russian Arctic). The positive matrix factorization (PMF) model was used for the source identification of PAHs. The results of the source identification showed that the mining activity was the major source of PAHs in the area, and that the mining influenced the surrounding natural area. The 5+6-ring PAHs were most abundant in the mining area. The lichen/soil (L/S) results showed that 2+3-ring and 4-ring PAHs could be transported by air and accumulated more in lichens than in the soil, while 5+6-ring PAHs accumulated more in the soil. Strong relationships between the quotient of soil/lichen (Q_SL) and Log K_OA and Log P_L and between the quotient of lichen/histic horizon soil and K_OW were observed. In addition, hydrogeological conditions influenced the downward transport of PAHs. Particularly surprising is the discovery of the high levels of 5+6 rings in the permafrost table (the bottom of the active layer). One hypothesis is given that the global climate change may lead to further depth of active layer so that PAHs may migrate to the deeper permafrost. In the impact area of mining activities, the soil inventory for 5+6-ring PAHs was estimated at 0.14±0.017 tons on average.

DOI: 10.1016/j.envpol.2019.113239

2020075486 Palmer, Adrian P. (University of London, Department of Geography, Centre for Quaternary Research, Egham, United Kingdom); Bendle, Jacob M.; MacLeod, Alison; Rose, James and Thorndycraft, Varyl R. The micromorphology of glaciolacustrine varve sediments and their use for reconstructing palaeoglaciological and palaeoenvironmental change: Quaternary Science Reviews, 226, Paper no. 105964, illus. incl. charts, 2 tables, sketch maps, 95 ref., December 15, 2019.

Former glaciolacustrine systems are an important archive of palaeoglaciological, palaeoenvironmental and palaeoclimatic change. The annually laminated (varved) sediments that, under certain conditions, accumulate in former glacial lakes, offer a rare opportunity to reconstruct such changes (e.g. glacier advance and retreat cycles, glacier ablation trends, permafrost melt, nival events) at annual or even sub-annual temporal resolution. Data of this kind are desirable for their ability to guide and test numerical model simulations of glacier dynamics and palaeoclimatic change that occur over rapid time intervals, with implications for predicting future glacier response to climatic change, or the effects of weather and climate events on lake sedimentation. The most valuable records preserved in glaciolacustrine systems are continuous varved sequences formed in the distal parts of glacial lakes, where microscale lamination structures can accumulate relatively undisturbed. Technological advances, in the last few decades, have enabled improved characterisation of glaciolacustrine varve microfacies and the precise measurement of varve thickness at the micrometre scale. However, unlike in cognate fields (e.g. soil science), protocols for the robust and consistent description and interpretation of glaciolacustrine varve sediments are lacking. To fill this gap, and to provide a resource for future studies of glaciolacustrine varved sediments, this paper reviews the processes of sedimentation in glacial lake basins, and presents the defining microfacies characteristics of glacial varves using a descriptive protocol that uses consistent examination of grain size, sorting, structure, nature of contacts, development of plasmic fabrics and features such as dropgrains and intraclasts within individual laminations. These lamination types are then combined into lamination sets, whose structures can be interpreted as glaciolacustrine varves. Within this framework, we define five principal assemblages of glaciolacustrine varve microfacies which, if clearly identified in palaeoglaciolacustrine settings, enable more detailed palaeoenvironmental interpretations to be made. Finally, we discuss the utility and complexities of reconstructing the evolution of former glacial lake systems using varve microfacies and thickness datasets.

DOI: 10.1016/j.quascirev.2019.105964

2020078532 Lininger, Katherine B. (University of Colorado at Boulder, Department of Geography, Boulder, CO) and Wohl, Ellen. Floodplain dynamics in North American permafrost regions under a warming climate and implications for organic carbon stocks; a review and synthesis: Earth-Science Reviews, 193, p. 24-44, illus. incl. 3 tables, sketch map, 251 ref., June 2019.

Although there have been studies on changes to hydrology in permafrost regions and exports of nutrients and organic matter to the Arctic Ocean, little is known about how geomorphic dynamics of rivers in permafrost regions will change in the future under a warming climate and the effects of those changes on floodplains. We focus on river dynamics in the context of channel-floodplain interactions and the implications for organic carbon storage in floodplains. As sites of nutrient processing and storage of sediments and organic matter, changes in channel and floodplain form and process will impact sediment yields, nutrient and organic matter export to the Arctic Ocean, aquatic and riparian habitat, and infrastructure. We present a review of the factors influencing reach-scale river dynamics, using the framework of factors affecting erosive force and erosional resistance of banks and floodplain surfaces, which will change due to a warming climate. We summarize studies indicating how observed and modeled trends in these factors will affect erosive force and erosional resistance in the future. We then hypothesize the net effects that these changes will have on the ratio of erosive force to erosional resistance, and the cascading effects on channel and floodplain form and process. We describe two scenarios that could occur under different conditions in the form of conceptual models, one in which the ratio of erosive force and erosional resistance decreases, and one in which the ratio increases. An increase in the ratio of erosive force to erosional resistance due to a reduction in permafrost extent and depth and an overall increase in discharge would increase bank erosion, bank failures, sediment supply, and lateral channel migration rates, decreasing floodplain turnover time and the age of riparian vegetation. A decrease in the ratio of erosive force to erosional resistance due to a reduction in erosive force relative to sediment supply would cause enhanced deposition within the river corridor. Regardless of which scenario may occur, changes in channel process and form will influence the ratio of lateral to vertical accretion, change the nature and stored amount of floodplain sediment, and change the sources and storage of organic carbon within floodplains.

DOI: 10.1016/j.earscirev.2019.02.024

2020078543 Obu, Jaroslav (University of Oslo, Department of Geosciences, Oslo, Norway); Westermann, Sebastian; Bartsch, Annett; Berdnikov, Nikolai; Christiansen, Hanne H.; Dashtseren, Avirmed; Delaloye, Reynald; Elberling, Bo; Etzelmüller, Bernd; Kholodov, Alexander; Khomutov, Artem; Kaab, Andreas; Leibman, Marina O.; Lewkowicz, Antoni G.; Panda, Santosh K.; Romanovsky, Vladimir; Way, Robert G.; Westergaard-Nielsen, Andreas; Wu Tonghua; Yamkhin, Jambaljav and Zou Defu. Northern Hemisphere permafrost map based on TTOP modelling for 2000-2016 at 1 km² scale: Earth-Science Reviews, 193, p. 299-316, illus. incl. 2 tables, sketch map, 129 ref., June 2019.

Permafrost is a key element of the cryosphere and an essential climate variable in the Global Climate Observing System. There is no remote-sensing method available to reliably monitor the permafrost thermal state. To estimate permafrost distribution at a hemispheric scale, we employ an equilibrium state model for the temperature at the top of the permafrost (TTOP model) for the 2000-2016 period, driven by remotely-sensed land surface temperatures, down-scaled ERA-Interim climate reanalysis data, tundra wetness classes and landcover map from the ESA Landcover Climate Change Initiative (CCI) project. Subgrid variability of ground temperatures due to snow and landcover variability is represented in the model using subpixel statistics. The results are validated against borehole measurements and reviewed regionally. The accuracy of the modelled mean annual ground temperature (MAGT) at the top of the permafrost is ±2°C when compared to permafrost borehole data. The modelled permafrost area (MAGT <0°C) covers 13.9´10⁶ km² (ca. 15% of the exposed land area), which is within the range or slightly below the average of previous estimates. The sum of all pixels having isolated patches, sporadic, discontinuous or continuous permafrost (permafrost probability >0) is around 21´10⁶ km² (22% of exposed land area), which is approximately 2´10⁶ km² less than estimated previously. Detailed comparisons at a regional scale show that the model performs well in sparsely vegetated tundra regions and mountains, but is less accurate in densely vegetated boreal spruce and larch forests.

DOI: 10.1016/j.earscirev.2019.04.023

2020076502 Fedorov, Roman (Russian Academy of Sciences, Siberian Branch, Earth Cryosphere Institute, Tyumen Scientific Centre, Tyumen, Russian Federation). Cryogenic resources; ice, snow, and permafrost in traditional subsistence systems in Russia: Resources (Basel), 8(1), Article 17, illus., 45 ref., March 2019.

This article is devoted to the study of the role of natural cryogenic resources in the traditional subsistence systems of the people of Russia. The main source of the actual information and the empirical basis reflecting the features of traditional ecological knowledge of the ethnic groups considered in the article are the scientific publications and ethnographic descriptions made by Russian researchers in the second half of the 19th century through to the beginning of the 21st century, and the results of our modern field research in the territory of Siberia and the Far East of Russia. The methodology of the study lies in the field of ethnoecology, and contains comparative and typological approaches, which have allowed for the detection and systematization of the main spheres of using natural cryogenic resources in traditional subsistence systems by the people of Russia, which include using the environment for indigenous subsistence, building materials, food preservation, obtaining potable water, the irrigation of crops, etc. In conclusion, some of the prospective for the ethnoecological examination of the role of the natural cryogenic resources in traditional subsistence systems were designated, and adaptations to modern innovative technologies based on the rational use of natural resources were also examined.

DOI: 10.3390/resources8010017

2020073375 Li Zongxing (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Gui Juan; Wang Xufeng; Feng Qi; Zhao, Tongtiegang; Ouyang Chaojun; Guo Xiaoyan; Zhang Baijuan and Shi Yang. Water resources in inland regions of Central Asia; evidence from stable isotope tracing: Journal of Hydrology, 570, p. 1-16, illus. incl. sketch maps, 2 tables, sects., 79 ref., March 2019.

Complex hydrological processes affect valuable water resources in inland regions across arid central Asia. Historically, this was a critical part of the Silk Road, and it is now named the modern Silk Road Economic Belt. Using the Qilian Mountains and Hexi Corridor in China as a case-study of the inland region, we collected a total of 2311 water samples from the area and performed a comprehensive investigation of the water cycle. Results from stable isotope tracing indicate clear spatial patterns. In the upstream mountainous regions, glacier snow meltwater becomes groundwater at the periglacial belt. Supra-permafrost water develops into river runoff in the permafrost region. There are also frequent exchanges between groundwater and river runoff along the vegetation belt. In the middle/downstream region, river runoff becomes groundwater. Throughout these processes, both river runoff and groundwater are consumed by evapotranspiration, are recycled, and make a substantial contribution to precipitation. Overall, the upstream mountainous region is a critical part of the water resources. The cryosphere belt accounts for 44% of the mountainous region but contributes to about 80% of water resources. Recycling of moisture also plays an important role. During the summer months (May to September) moisture recycling accounted for 24% and 14% of precipitation in upstream and middle/downstream regions, respectively. The findings from the stable isotope tracing provide insights into hydrological processes and can help improve water management in inland regions of Central Asia.

DOI: 10.1016/j.jhydrol.2019.01.003

2020074865 Betlem, Peter (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Svalbard and Jan Mayen Islands); Senger, Kim and Hodson, Andrew J. 3D thermobaric modelling of the gas hydrate stability zone onshore central Spitsbergen, Arctic Norway: Marine and Petroleum Geology, 100, p. 246-262, illus. incl. sects., sketch maps, strat. col., 2 tables, geol. sketch map, 109 ref., February 2019.

Dissociation of onshore natural gas hydrates (NGHs) could lead to the release of methane directly to the atmosphere, especially in Arctic regions such as Svalbard, where enhanced climate warming has the capacity to promote rapid methane evasion to the atmosphere following the decay of permafrost and glacier ice. Here we present the first assessment of the NGH stability zone (GHSZ) in central Spitsbergen, a climate-sensitive part of Svalbard where thermobaric conditions appear favourable for onshore NGH formation. We developed an approach incorporating regionally constrained 3-dimensional parameterisation of temperature, pressure and phase boundary (93% methane, 7% ethane, 35 ppt salinity) to define the GHSZ. This resulted in an up to 650 m thick (mean: 308 m) GHSZ covering 74.8% of the study area, thickening significantly in the east where the climate is colder. Perturbation of the base case parameters was undertaken to quantify the sensitivity of the GHSZ to the variation in environmental conditions across the study area. We present 26 examples of these deterministic scenarios and show that the largest changes in the GHSZ were observed when either the ethane content (to 20%) or the regional pore water pressure (to 125% hydrostatic) were increased. The GHSZ also increased markedly when the geothermal gradient was reduced from 33 to 26°C km^-1, but was almost completely inhibited by a dry gas (100% methane), greater salinity (50 ppt), or exposure to an increase in surface temperatures relative to the mean annual air temperature (e.g., by 2°C). Most parameters affected both the upper and the lower stability boundary of the GHSZ, with the exception of the geothermal gradient, which impacted primarily upon the latter. Given that Svalbard is host to a proven petroleum system, we conclude that NGHs almost certainly exist onshore Svalbard.

DOI: 10.1016/j.marpetgeo.2018.10.050

2020074936 Boike, Julia (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Potsdam, Germany); Nitzbon, Jan; Anders, Katharina; Grigoriev, Mikhail; Bolshiyanov, Dmitry; Langer, Moritz; Lange, Stephan; Bornemann, Niko; Morgenstern, Anne; Schreiber, Peter; Wille, Christian; Chadburn, Sarah; Gouttevin, Isabelle; Burke, Eleanor and Kutzbach, Lars. A 16-year record (2002-2017) of permafrost, active-layer, and meteorological conditions at the Samoylov Island Arctic permafrost research site, Lena River delta, northern Siberia; an opportunity to validate remote-sensing data and land surface, snow, and permafrost models: Earth System Science Data (ESSD), 11(1), p. 261-299, illus. incl. 7 tables, 79 ref., 2019.

Most of the world's permafrost is located in the Arctic, where its frozen organic carbon content makes it a potentially important influence on the global climate system. The Arctic climate appears to be changing more rapidly than the lower latitudes, but observational data density in the region is low. Permafrost thaw and carbon release into the atmosphere, as well as snow cover changes, are positive feedback mechanisms that have the potential for climate warming. It is therefore particularly important to understand the links between the energy balance, which can vary rapidly over hourly to annual timescales, and permafrost conditions, which changes slowly on decadal to centennial timescales. This requires long-term observational data such as that available from the Samoylov research site in northern Siberia, where meteorological parameters, energy balance, and subsurface observations have been recorded since 1998. This paper presents the temporal data set produced between 2002 and 2017, explaining the instrumentation, calibration, processing, and data quality control. Furthermore, we present a merged data set of the parameters, which were measured from 1998 onwards. Additional data include a high-resolution digital terrain model (DTM) obtained from terrestrial lidar laser scanning. Since the data provide observations of temporally variable parameters that influence energy fluxes between permafrost, active-layer soils, and the atmosphere (such as snow depth and soil moisture content), they are suitable for calibrating and quantifying the dynamics of permafrost as a component in earth system models. The data also include soil properties beneath different microtopographic features (a polygon centre, a rim, a slope, and a trough), yielding much-needed information on landscape heterogeneity for use in land surface modelling. For the record from 1998 to 2017, the average mean annual air temperature was -12.3 °C, with mean monthly temperature of the warmest month (July) recorded as 9.5 °C and for the coldest month (February) -32.7 °C. The average annual rainfall was 169 mm. The depth of zero annual amplitude is at 20.75 m. At this depth, the temperature has increased from -9.1 °C in 2006 to -7.7 °C in 2017. The presented data are freely available through the PANGAEA (URL: https://doi.org/10.1594/PANGAEA.891142) and Zenodo (URL: https://zenodo.org/record/2223709), last access: 6 February 2019) websites.

DOI: 10.5194/essd-11-261-2019

2020079926 Weber, Samuel (University of Zurich, Department of Geography, Zurich, Switzerland); Beutel, Jan; Da Forno, Reto; Geiger, Alain; Gruber, Stephan; Gsell, Tonio; Hasler, Andreas; Keller, Matthias; Lim, Roman; Limpach, Philippe; Meyer, Matthias; Talzi, Igor; Thiele, Lothar; Tschudin, Christian; Vieli, Andreas; Vonder Mühll, Daniel and Yucel, Mustafa. A decade of detailed observations (2008-2018) in steep bedrock permafrost at the Matterhorn Hornligrat (Zermatt, CH): Earth System Science Data (ESSD), 11(3), p. 1203-1237, illus. incl. 8 tables, 99 ref., 2019.

The PermaSense project is an ongoing interdisciplinary effort between geo-science and engineering disciplines and started in 2006 with the goals of realizing observations that previously have not been possible. Specifically, the aims are to obtain measurements in unprecedented quantity and quality based on technological advances. This paper describes a unique >10-year data record obtained from in situ measurements in steep bedrock permafrost in an Alpine environment on the Matterhorn Hornligrat, Zermatt, Switzerland, at 3500 ma.s.l. Through the utilization of state-of-the-art wireless sensor technology it was possible to obtain more data of higher quality, make these data available in near real time and tightly monitor and control the running experiments. This data set constitutes the longest, densest and most diverse data record in the history of mountain permafrost research worldwide with 17 different sensor types used at 29 distinct sensor locations consisting of over 114.5 million data points captured over a period of 10 or more years. By documenting and sharing these data in this form we contribute to making our past research reproducible and facilitate future research based on these data, e.g., in the areas of analysis methodology, comparative studies, assessment of change in the environment, natural hazard warning and the development of process models. Finally, the cross-validation of four different data types clearly indicates the dominance of thawing-related kinematics.

DOI: 10.5194/essd-11-1203-2019

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