|
2019017071 Isaev, V. S. (Lomonosov Moscow State University, Department of Geocryology, Moscow, Russian Federation); Koshurnikov, A. V.; Pogorelov, A.; Amangurov, R. M.; Podchasov, O.; Sergeev, D. O.; Buldovich, S. N.; Aleksyutina, D. M.; Grishakina, E. A. and Kioka, Arata. Cliff retreat of permafrost coast in south-west Baydaratskaya Bay, Kara Sea, during 2005-2016: Permafrost and Periglacial Processes, 30(1), p. 35-47, illus. incl. 2 tables, 40 ref., March 2019.
Recent years of increasing air temperature in the Arctic have led to a significant increase in the rate of retreat of permafrost coast, which has threatened livelihoods and infrastructure in these areas. The Kara Sea hosts more than 25% of the total Arctic coastline. However, little is known about how coastal erosion in the Kara Sea may have changed through time, and the climatic and environmental drivers remain unclear. Here we study coastal dynamics along a 4-km stretch of permafrost and sea-ice-affected coastline in south-west Baydaratskaya Bay of the Kara Sea, western Siberia, between 2005 and 2016, by using handheld differential GPS mapping and satellite imagery. We identified temporal and spatial variations in the retreat rates, ranging between 1.0 (+0.1/-0.6) and 1.9 (+0.7/-1.3) m/yr over the studied coastline during 2005-2016. We also made ground temperature measurements, subsurface resistivity measurements and estimates of wave energy flux of wind-driven ocean waves, to investigate the dominant climatic factors influencing the observed retreat rates through time. We found that wind-driven wave activity during sea-ice-free days influences the magnitude of coastal retreat in the study area, while recent temperature rise has contributed less to enhancing coastal retreat during the study period. This suggests that the amount of eroded sediment and the associated release of nutrient to the nearshore zone are controlled by the magnitude of wave activity, which may influence infrastructure along the permafrost coast and marine ecosystems in the proximal ocean. Abstract Copyright (2019), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1993
2019017072 Kim, Kyungmin (Seoul National University, School of Earth and Environmental Science, Seoul, South Korea); Yang, Ji-Woong; Yoon, Hyunsuk; Byun, Eunji; Fedorov, Alexander; Ryu, Yeongjun and Ahn, Jinho. Greenhouse gas formation in ice wedges at Cyuie, central Yakutia: Permafrost and Periglacial Processes, 30(1), p. 48-57, illus. incl. 1 table, 33 ref., March 2019.
Greenhouse gases (GHGs) trapped in ice wedges may provide useful information on biogeochemical environments in ground ice. Previous studies have reported highly elevated CO2 and CH4 mixing ratios in ice wedges. However, N2O mixing ratios in ice wedges remain unknown. Here, we present CO2, CH4 and N2O mixing ratios in bubbles and plausible mechanisms of GHG formation for two lakeside ice wedges at Cyuie village near Yakutsk. The CO2 gas age corresponds to the Last Glacial Maximum (18-19 ka). The d(N2/Ar) values and bubble shapes indicate that the ice wedges formed by dry snow compaction rather than snowmelt water refreezing, while the d18O and dD values of the ice indicate changes in the source area location and/or the climate during the Last Glacial Maximum. Using a dry extraction method, we obtained gas mixing ratios of 7-13% CO2, 5-130 ppm CH4 and 100-5000 ppb N2O. The d(O2/Ar) values imply that most of the O2 was consumed by biological respiration. The CH4 is negatively correlated with N2O and CO2. The N2O might have inhibited CH4 production. Abstract Copyright (2019), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1994
2019017069 Nagy, Balazs (Eotvos University, Department of Physical Geography, Budapest, Hungary); Igneczi, Adam; Kovacs, Jozsef; Szalai, Zoltan and Mari, Laszlo. Shallow ground temperature measurements on the highest volcano on Earth, Mt. Ojos del Salado, arid Andes, Chile: Permafrost and Periglacial Processes, 30(1), p. 3-18, illus. incl. 3 tables, 35 ref., March 2019. Includes 3 appendices.
Mt. Ojos del Salado (6893 m a.s.l.) lies within the Andean Arid Diagonal, on the Chilean-Argentinean border. Due to the extremely arid climate, surface ice is not widespread on Mt. Ojos del Salado and at similar high-altitude massifs in the region, although ice-bearing permafrost might be present. However, the thermal regime of the ground is relatively unknown in the region, especially outside of rock glaciers at high elevations north of 30°S. To study ground thermal regimes, in-situ shallow ground temperature and snow coverage from satellite imagery have been surveyed for four years (2012-2016) at six sites between the elevations of 4200-6893 m a.s.l. on Mt. Ojos del Salado (27°07'S, 68°32'W). According to the ground temperature and snow coverage data at the six monitoring sites, the presence of permafrost is unlikely below 4550 m a.s.l. but likely above 5250 m a.s.l. on Mt. Ojos del Salado. In addition, the active layer becomes extremely thin around 6750 m a.s.l. Abstract Copyright (2019), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1989
2019017073 Yang Yuzhong (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Qingbai; Hou Yandong; Zhang Peng; Yun Hanbo; Jin Huijun; Xu Xiaoming and Jiang Guanli. Using stable isotopes to illuminate thermokarst lake hydrology in permafrost regions on the Qinghai-Tibet Plateau, China: Permafrost and Periglacial Processes, 30(1), p. 58-71, illus. incl. 4 tables, 44 ref., March 2019.
Thermokarst lakes are widespread and developing on the Qinghai-Tibet Plateau (QTP), and they have modified hydrological processes and water balance in the region. Despite increasing attention, our understanding of the hydrological behaviors of thermokarst lakes under permafrost degradation remains limited on the QTP. In this study, water stable isotope tracers were used to characterize the spatial and seasonal hydrological changes of thermokarst lakes on the central QTP. Significant seasonal variations and factors influencing the isotopic hydrology of lakes were revealed through the ice-free season. Substantial differences in lake-specific input water isotope compositions (dI) among the lakes indicate two lake-recharge regimes: rain-dominated, and snowmelt/permafrost thaw-dominated. We suggest that precipitation and active-layer hydrology controlled these hydrological changes in the ice-free season. However, under ice cover, melting of the surrounding permafrost (including ground ice) dominated the hydrology of thermokarst lakes. Importantly, a conceptual model delineates the hydrological evolution of thermokarst lakes under permafrost degradation. This study serves as a baseline for future investigations of hydrological processes and water balance relating to thawing permafrost on the QTP. Abstract Copyright (2019), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1996
2019019546 Bolch, Tobias (University of Zurich, Department of Geography, Zurich, Switzerland); Rohrbach, N.; Kutuzov, S.; Robson, B. A. and Osmonov, A. Occurrence, evolution and ice content of ice-debris complexes in the Ak-Shiirak, central Tien Shan revealed by geophysical and remotely-sensed investigations: Earth Surface Processes and Landforms, 44(1), p. 129-143, illus. incl. 1 table, geol. sketch maps, 60 ref., January 2019.
Rock glaciers and large ice-debris complexes are common in many mountain ranges and are especially prominent in semi-arid mountains such as the Andes or the Tien Shan. These features contain a significant amount of ice but their occurrence and evolution are not well known. Here, we present an inventory of the ice-debris complexes for the Ak-Shiirak, Tien Shan's second largest glacierised massif, and a holistic methodology to investigate two characteristic and large ice-debris complexes in detail based on field investigations and remote sensing analysis using Sentinel-1 SAR data, 1964 Corona and recent high resolution stereo images. Overall, we found 74 rock glaciers and ice-debris complexes covering an area of 11.2 km2 (3.2% of the glacier coverage) with a mean elevation of about 3950 m asl. Most of the complexes are located south-east of the main ridge of Ak-Shiirak. Ground penetrating radar (GPR) measurements reveal high ice content with the occurrence of massif debris-covered dead-ice bodies in the parts within the Little Ice Age glacier extent. These parts showed significant surface lowering, in some places exceeding 20 m between 1964 and 2015. The periglacial parts are characterised by complex rock glaciers of different ages. These rock glaciers could be remnants of debris-covered ice located in permafrost conditions. They show stable surface elevations with no or only very low surface movement. However, the characteristics of the fronts of most rock glacier parts indicate slight activity and elevation gains at the fronts slight advances. GPR data indicated less ice content and slanting layers which coincide with the ridges and furrows and could mainly be formed by glacier advances under permafrost conditions. Overall, the ice content is decreasing from the upper to the lower part of the ice-debris complexes. Hence, these complexes, and especially the glacier-affected parts, should be considered when assessing the hydrological impacts of climate change. Copyright 2018 John Wiley & Sons, Ltd.
DOI: 10.1002/esp.4487
2019023967 Luo Dongliang (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Jin Huijun and Bense, Victor F. Ground surface temperature and the detection of permafrost in the rugged topography on NE Qinghai-Tibet Plateau: Geoderma, 333, p. 57-68, illus. incl. 2 tables, sketch map, 55 ref., January 1, 2019.
The thermal regime of permafrost in the rugged topography on parts of the Qinghai-Tibet Plateau (QTP) remains ambiguous, due to general inaccessibility and inconvenient investigations with geophysical prospecting. While the relatively easy implementations of monitoring ground surface temperature (GST) may facilitate the investigations of permafrost thermal state. Here, surface freezing and thawing and the relationship between GST and permafrost temperature are investigated in the Bayan Har Mountains, NE QTP on the basis of 22 monitoring sites. Results demonstrate that, unlike the air temperature (Ta) mainly controlled by elevation, the GST is complicately influenced by elevation and the surface characteristics, such as vegetation, local soil textures, as well as the exposure to solar radiation. Mean annual GST (MAGST) ranges from 1.1 °C to -3.1 °C and is averaged at -0.8 °C. MAGST generally decreases at a lapse rate of 1.1 °C/100 m in relation to elevation. Surface freezing and thawing processes depend on topography and local surface characteristics. The onset of unstable thawing, stable thawing, unstable freezing, and stable freezing are averaged at 6 April 2015, 15 May 2015, 14 October 2015, and 21 October 2015. Based on the relationship between MAGST and the ground temperature at the depth of zero annual amplitude, GST likely serves as a reliable indicator of the thermal state of permafrost. For the 22 sites, it is estimated that the lowest TZAA of permafrost is -3.4 °C and the thickest permafrost is 106.2 m. However, detailed investigations of subsurface characteristics are indispensable for the accurate inference of permafrost.
DOI: 10.1016/j.geoderma.2018.07.011
2019019303 Murphy, Melissa J. (University of Oxford, Department of Earth Sciences, Oxford, United Kingdom); Porcelli, Don; Pogge von Strandmann, Philip A. E.; Hirst, Catherine A.; Kutscher, Liselott; Katchinoff, Joachim A.; Mörth, Carl-Magnus; Maximov, Trofim and Andersson, Per S. Tracing silicate weathering processes in the permafrost-dominated Lena River watershed using lithium isotopes: Geochimica et Cosmochimica Acta, 245, p. 154-171, illus. incl. 1 table, sketch map, 87 ref., January 15, 2019. Includes appendices.
Increasing global temperatures are causing widespread changes in the Arctic, including permafrost thawing and altered freshwater inputs and trace metal and carbon fluxes into the ocean and atmosphere. Changes in the permafrost active layer thickness can affect subsurface water flow-paths and water-rock interaction times, and hence weathering processes. Riverine lithium isotope ratios (reported as d7Li) are tracers of silicate weathering that are unaffected by biological uptake, redox, carbonate weathering and primary lithology. Here we use Li isotopes to examine silicate weathering processes in one of the largest Russian Arctic rivers: the Lena River in eastern Siberia. The Lena River watershed is a large multi-lithological catchment, underlain by continuous permafrost. An extensive dataset of dissolved Li isotopic compositions of waters from the Lena River main channel, two main tributaries (the Aldan and Viliui Rivers) and a range of smaller sub-tributaries are presented from the post-spring flood/early-summer period at the onset of active layer development and enhanced water-rock interactions. The Lena River main channel (average d7Lidiss ~19 ppm) has a slightly lower isotopic composition than the mean global average of 23 ppm (Huh et al., 1998a). The greatest range of [Li] and d7Lidiss are observed in catchments draining the south-facing slopes of the Verkhoyansk Mountain Range. South-facing slopes in high-latitude, permafrost-dominated regions are typically characterised by increased summer insolation and higher daytime temperatures relative to other slope aspects. The increased solar radiation on south-facing catchments promotes repeated freeze-thaw cycles, and contributes to more rapid melting of snow cover, warmer soils, and increased active layer thaw depths. The greater variability in d7Li and [Li] in the south-facing rivers likely reflect the greater infiltration of melt water and enhanced water-rock interactions within the active layer.A similar magnitude of isotopic fractionation is observed between the low-lying regions of the Central Siberian Plateau (and catchments draining into the Viliui River), and catchments draining the Verkhoyansk Mountain Range into the Aldan River. This is in contrast to global rivers in non-permafrost terrains that drain high elevations or areas of rapid uplift, where high degrees of physical erosion promote dissolution of freshly exposed primary rock typically yielding low d7Lidiss, and low-lying regions exhibit high riverine d7Li values resulting from greater water-rock interaction and formation of secondary mineral that fractionates Li isotopes. Overall, the range of Li concentrations and d7Lidiss observed within the Lena River catchment are comparable to global rivers located in temperate and tropical regions. This suggests that cryogenic weathering features specific to permafrost regions (such as the continual exposure of fresh primary minerals due to seasonal freeze-thaw cycles, frost shattering and salt weathering), and climate (temperature and runoff), are not a dominant control on d7Li variations. Despite vastly different climatic and weathering regimes, the same range of riverine d7Li values globally suggests that the same processes govern Li geochemistry - that is, the balance between primary silicate mineral dissolution and the formation (or exchange with) secondary minerals. This has implications for the use of d7Li as a palaeo-weathering tracer for interpreting changes in past weathering regimes.
DOI: 10.1016/j.gca.2018.10.024
2019021509 Walvoord, Michelle A. (U. S. Geological Survey, Earth System Processes Division, Denver, CO); Voss, Clifford I.; Ebel, Brian A. and Minsley, Burke J. Development of perennial thaw zones in boreal hillslopes enhances potential mobilization of permafrost carbon: Environmental Research Letters, 14(1), Paper no. 015003, illus. incl. sketch map, 70 ref., January 2019.
Permafrost thaw alters subsurface flow in boreal regions that in turn influences the magnitude, seasonality, and chemical composition of streamflow. Prediction of these changes is challenged by incomplete knowledge of timing, flowpath depth, and amount of groundwater discharge to streams in response to thaw. One important phenomenon that may affect flow and transport through boreal hillslopes is development of lateral perennial thaw zones (PTZs), the existence of which is here supported by geophysical observations and cryohydrogeologic modeling. Model results link thaw to enhanced and seasonally-extended baseflow, which have implications for mobilization of soluble constituents. Results demonstrate the sensitivity of PTZ development to organic layer thickness and near-surface factors that mediate heat exchange at the atmosphere/ground-surface interface. Study findings suggest that PTZs serve as a detectable precursor to accelerated permafrost degradation. This study provides important contextual insight on a fundamental thermo-hydrologic process that can enhance terrestrial-to-aquatic transfer of permafrost carbon, nitrogen, and mercury previously sequestered in thawing watersheds. Copyright (Copyright) 2019 Not subject to copyright in the USA. Contribution of U.S. Geological Survey
DOI: 10.1088/1748-9326/aaf0cc
2019021424 Yang, Q. (Yunnan University, Department of Atmospheric Science, Laboratory of Atmospheric Environment and Processes in the Boundary Layer over the Low-Latitude Plateau Region, Kunming, China); Dan Li; Wu, J.; Jiang, R.; Dan, J.; Li Weidong; Yang, F.; Yang, X. and Xia, L. The improved freeze-thaw process of a climate-vegetation model; calibration and validation tests in the source region of the Yellow River: Journal of Geophysical Research: Atmospheres, 123(23), p. 13,346-13,367, illus. incl. 6 tables, sketch map, 61 ref., December 16, 2018.
The freeze-thaw process significantly impacts land surface processes in permafrost and influences the regional climate. In this study, the freeze-thaw process in the atmosphere-vegetation interaction model (AVIM) was improved by utilizing the universal soil hydrothermal coupling equations, and by introducing the freezing depression point-based freeze-thaw parameterization scheme to form a model known as the AVIM frozen soil model (AVIM_FSM). Then, the seasonal frozen soil observational data at Maqu station, located in the Yellow River source region, were used to calibrate the freeze-thaw-related parameters with an artificial intelligence particle swarm optimization method, and the model was validated. The results indicated that by improving the freeze-thaw process, the temporal variations in soil temperature and liquid water content simulated by the AVIM_FSM model agreed well with the observations. By calibrating the parameters, the deviations between the observations and corresponding simulations were reduced compared with those in the AVIM. Based on the AVIM_FSM, the physical mechanism of the freeze-thaw process was discussed, the different freeze-thaw parameterization schemes were compared, the related freeze-thaw process parameters were quantitatively evaluated, and the following was indicated: (1) the freeze-thaw process was mainly determined by radiation, sensible heat flux, and ice change in frozen soil; (2) the freezing depression point-based freeze-thaw parameterization scheme was superior to the empirical scheme, which can reasonably describe the freezing and thawing start dates with lower deviations; and (3) the particle swarm optimization algorithm can efficiently calibrate the freeze-thaw-related parameters and improve the simulation accuracy. Abstract Copyright (2018). The Authors.
DOI: 10.1029/2017JD028050
2019021423 Yang Kai (Lanzhou University, College of Atmospheric Sciences, Laboratory of Arid Climate Change and Disaster Reduction of Gansu Province, Lanzhou, China); Wang Chenghai and Li Shiyue. Improved simulation of frozen-thawing process in land surface model (CLM4.5): Journal of Geophysical Research: Atmospheres, 123(23), p. 13,238-13,258, illus. incl. 5 tables, sketch map, 52 ref., December 16, 2018.
Soil freezing-thawing cycle is a hallmark feature of the land surface over cold regions. Variations in soil moisture and temperature during frozen-thawing (FT) process are important for water and energy exchange between land and atmosphere. Results of regional simulations by Community Land Model version 4.5 (CLM4.5) over the Tibetan Plateau show that error of daily soil temperature is within 3°C and error of daily soil moisture is with 0.10 mm3/mm3 in FT process, averaged at 10 sites of whole Tibetan Plateau. Single-point simulations show that model biases partly attribute to uncertainties of initial condition and soil category data; excluding impacts of model setting, large biases of soil moisture still exist during soil thawing, and CLM4.5 fails to simulate the diurnal cycle of soil moisture in this period. Modifications of the FT parameterizations in CLM4.5 are proposed, which include (1) use of virtual temperature (Tv) instead of constant freezing point to determine occurring of phase change, (2) introduction of phase change efficiency (e) to optimize variation rate of soil temperature and moisture in FT process, and (3) consideration of inferred impacts of phase change on soil heat conduction. Single-point and global simulations show that compared to original parameterizations in CLM4.5, these modifications can reproduce the features of daily and diurnal variations in soil moisture and make simulation in FT process closer to the observations. Abstract Copyright (2018). American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2017JD028260
2019023302 Yi Peng (Hohai University, College of Hydrology and Water Resources, Nanjing, China); Luo Huan; Chen Li; Yu Zhongbo; Jin Huijun; Chen Xiaobing; Wan Chengwei; Aldahan, Ala Adin; Zheng, Minjie and Hu Qingfang. Evaluation of ground water discharge into surface water by using Radon-222 in the source area of the Yellow River, Qinghai-Tibet Plateau: Journal of Environmental Radioactivity, 192, p. 257-266, illus. incl. 3 tables, sketch maps, 62 ref., December 2018. Includes appendices.
Understanding hydrological processes in the Source Area of the Yellow River (SAYR), Qinghai-Tibet Plateau, is vital for protection and management of groundwater and surface water resources in the region. In situ water measurements of exchange rates between surface water and groundwater are, however, hard to conduct because of the harsh natural conditions of the SAYR. We here present an indirect method using in situ 222Rn measurements to estimate groundwater discharge into rivers and lakes in the SAYR. 222Rn was measured in rivers, lakes, groundwater and springs during three sampling periods (2014-2016), and the results indicate large variability in the concentration of the isotope. The data also indicate decreasing 222Rn trends in groundwater in the cold season (the Feb-2015 sampling period) which may be linked to frequency of capturing 222Rn in the frozen ground caused by geocryogenic processes. In addition, permafrost spatial extent and freeze-thaw processes have strongly affected the hydrological conditions in the region.
DOI: 10.1016/j.jenvrad.2018.07.003
2019021504 Haynes, K. M. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Connon, R. F. and Quinton, W. L. Permafrost thaw induced drying of wetlands at Scotty Creek, NWT, Canada: Environmental Research Letters, 13(11), Paper no. 114001, illus. incl. 2 tables, sketch maps, 32 ref., November 2018.
Northwestern Canada is one of the most rapidly warming regions on Earth. The scale and rapidity of recently observed warming-induced changes throughout this region indicate that it is particularly sensitive to climate warming and capable of rapid responses to perturbations. Unprecedented rates of permafrost thaw in the zone of discontinuous permafrost are transforming forests to wetlands, and changing the distribution and routing of water over the landscape as evidenced by recent increases in basin discharge. However, the impact of increasing basin discharge on basin water storage is not well understood. Water levels on a permafrost plateau, channel fen, and isolated and connected bogs were monitored from 2003-2017 in the Scotty Creek watershed, Northwest Territories. The water level in the channel fen did not significantly change over the period of study, sustained by inputs from the increasingly-connected network of bogs as permafrost barriers thawed. Bogs with varying levels of connection to the drainage network released from storage between 40 and 53 mm of water over the study period. The water level in the monitored isolated bog did not significantly change over this period. Estimates of moisture contributions derived directly from vertical permafrost thaw and from the lateral expansion of contributing areas account for 90% of the observed cumulative increase of 1043 mm in basin runoff between 1998-2012, leaving 109 mm of this increase unaccounted for. Increasing connectivity to the drainage network and transient wetland drainage at the landscape scale resulted from permafrost thaw-induced talik development. The similarity between the magnitude of wetland drainage and that of enhanced runoff suggests that increased connectivity of wetlands to the drainage network may contribute to increasing runoff from the Scotty Creek watershed. Permafrost thaw-induced land cover transition was found to have both short and long-term effects on runoff generation. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aae46c
2019021506 Jones, Benjamin M. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Farquharson, Louise M.; Baughman, Carson A.; Buzard, Richard M.; Arp, Christopher D.; Grosse, Guido; Bull, Diana L.; Günther, Frank; Nitze, Ingmar; Urban, Frank; Kasper, Jeremy L.; Frederick, Jennifer M.; Thomas, Matthew; Jones, Craig; Mota, Alejandro; Dallimore, Scott; Tweedie, Craig; Maio, Christopher; Mann, Daniel H.; Richmond, Bruce; Gibbs, Ann; Xiao, Ming; Sachs, Torsten; Iwahana, Go; Kanevskiy, Mikhail and Romanovsky, Vladimir E. A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff erosion in the Arctic: Environmental Research Letters, 13(11), Paper no. 115001, illus. incl. 1 table, sketch map, 59 ref., November 2018.
Eroding permafrost coasts are likely indicators and integrators of changes in the Arctic System as they are susceptible to the combined effects of declining sea ice extent, increases in open water duration, more frequent and impactful storms, sea-level rise, and warming permafrost. However, few observation sites in the Arctic have yet to link decadal-scale erosion rates with changing environmental conditions due to temporal data gaps. This study increases the temporal fidelity of coastal permafrost bluff observations using near-annual high spatial resolution (<1 m) satellite imagery acquired between 2008-2017 for a 9 km segment of coastline at Drew Point, Beaufort Sea coast, Alaska. Our results show that mean annual erosion for the 2007-2016 decade was 17.2 m yr-1, which is 2.5 times faster than historic rates, indicating that bluff erosion at this site is likely responding to changes in the Arctic System. In spite of a sustained increase in decadal-scale mean annual erosion rates, mean open water season erosion varied from 6.7 m yr-1 in 2010 to more than 22.0 m yr-1 in 2007, 2012, and 2016. This variability provided a range of coastal responses through which we explored the different roles of potential environmental drivers. The lack of significant correlations between mean open water season erosion and the environmental variables compiled in this study indicates that we may not be adequately capturing the environmental forcing factors, that the system is conditioned by long-term transient effects or extreme weather events rather than annual variability, or that other not yet considered factors may be responsible for the increased erosion occurring at Drew Point. Our results highlight an increase in erosion at Drew Point in the 21st century as well as the complexities associated with unraveling the factors responsible for changing coastal permafrost bluffs in the Arctic. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
DOI: 10.1088/1748-9326/aae471
2019021449 Chen Jie (Chinese University of Hong Kong, Institute of Space and Earth Information Science, Hong Kong, China); Liu Lin; Zhang Tingjun; Cao Bin and Lin Hui. Using persistent scatterer interferometry to map and quantify permafrost thaw subsidence; a case study of Eboling Mountain on the Qinghai-Tibet Plateau: Journal of Geophysical Research: Earth Surface, 123(10), p. 2663-2676, illus. incl. 2 tables, sketch maps, 69 ref., October 2018.
Permafrost thaw subsidence, a key indicator of permafrost degradation, remains poorly quantified or understood. It is particularly challenging to detect and measure surface subsidence due to the loss of subsurface ice over a large area because it usually develops gradually, over several years or decades. Here we utilize the persistent scatterer interferometric synthetic aperture radar (PSI) approach to remotely measure gradual surface subsidence on Eboling Mountain in the northeastern region of the Qinghai-Tibet Plateau, where thermal erosion gullies are well developed. Most of the previous multitemporal interferometric synthetic aperture radar studies on permafrost used the small baseline subset method. By contrast, the PSI approach benefits from the full spatial resolution and is less affected by temporal or geometric decorrelation. In the PSI analysis, we incorporate a piecewise elevation change model that includes periodic subsidence/uplift because of its seasonally varying components as well as its linear subsidence trends. Applying this permafrost-designated PSI algorithm to 17-L band ALOS-1 PALSAR images taken between 2006 and 2011, we find that both the thermal erosion gullies and the surrounding regions (within about 300 m) subside gradually. The subsidence trends range from 0.3 to 3 cm/yr. This suggests that permafrost areas near the gullies are more vulnerable to gradual thawing and degradation. This study demonstrates the potential of using PSI to study permafrost thaw processes and of assessing its impacts over vast areas on the Qinghai-Tibet Plateau and in the Arctic. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2018JF004618
2019024026 Zhang, Hui (University of Helsinki, Faculty of Biological and Environmental Sciences, Helsinki, Finland); Gallego-Sala, A. V.; Amesbury, Matthew J.; Charman, Dan J.; Piilo, Sanna R. and Valiranta, M. M. Inconsistent response of Arctic permafrost peatland carbon accumulation to warm climate phases: Global Biogeochemical Cycles, 32(10), p. 1605-1620, illus. incl. 3 tables, 97 ref., October 2018.
Northern peatlands have accumulated large carbon (C) stocks since the last deglaciation and during past millennia they have acted as important atmospheric C sinks. However, it is still poorly understood how northern peatlands in general and Arctic permafrost peatlands in particular will respond to future climate change. In this study, we present C accumulation reconstructions derived from 14 peat cores from four permafrost peatlands in northeast European Russia and Finnish Lapland. The main focus is on warm climate phases. We used regression analyses to test the importance of different environmental variables such as summer temperature, hydrology, and vegetation as drivers for nonautogenic C accumulation. We used modeling approaches to simulate potential decomposition patterns. The data show that our study sites have been persistent mid- to late-Holocene C sinks with an average accumulation rate of 10.80-32.40 g C m-2 year-1. The warmer climate phase during the Holocene Thermal Maximum stimulated faster apparent C accumulation rates while the Medieval Climate Anomaly did not. Moreover, during the Little Ice Age, apparent C accumulation rates were controlled more by other factors than by cold climate per se. Although we could not identify any significant environmental factor that drove C accumulation, our data show that recent warming has increased C accumulation in some permafrost peatland sites. However, the synchronous slight decrease of C accumulation in other sites may be an alternative response of these peatlands to warming in the future. This would lead to a decrease in the C sequestration ability of permafrost peatlands overall. Abstract Copyright (2018). American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2018GB005980
2019021450 Zipper, Samuel C. (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada); Lamontagne-Hallé, Pierrick; McKenzie, Jeffrey M. and Rocha, Adrian V. Groundwater controls on postfire permafrost thaw; water and energy balance effects: Journal of Geophysical Research: Earth Surface, 123(10), p. 2677-2694, illus. incl. 2 tables, 120 ref., October 2018.
Fire frequency and severity are increasing in high-latitude regions, but the degree to which groundwater flow impacts the response of permafrost to fire remains poorly understood. Here we use the Anaktuvuk River Fire (Alaska, USA) as an example for simulating groundwater-permafrost interactions following fire. We identify key thermal and hydrologic parameters controlling permafrost response to fire both with and without groundwater flow, and separate the relative influence of changes to the water and energy balances on active layer thickness. Our results show that mineral soil porosity, which influences the bulk subsurface thermal conductivity, is a key parameter controlling active layer response to fire in both the absence and presence of groundwater flow. However, including groundwater flow in models increases the perceived importance of subsurface hydrologic properties, such as the soil permeability, and decreases the perceived importance of subsurface thermal properties, such as the thermal conductivity of soil solids. Furthermore, we demonstrate that changes to the energy balance (increased soil temperature) drive increased active layer thickness following fire, while changes to the water balance (decreased groundwater recharge) lead to reduced landscape-scale variability in active layer thickness and groundwater discharge to surface water features such as streams. These results indicate that explicit consideration of groundwater flow is critical to understanding how permafrost environments respond to fire. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.
DOI: 10.1029/2018JF004611
2019023262 Matsuoka, Norikazu (University of Tsukuba, Faculty of Life and Environmental Sciences, Tsukuba, Japan); Christiansen, Hanne H. and Watanabe, Tatsuya. Ice-wedge polygon dynamics in Svalbard; lessons from a decade of automated multi-sensor monitoring: Permafrost and Periglacial Processes, 29(3), p. 210-227, illus. incl. 1 table, 22 ref., September 2018.
Twelve years of continuous monitoring of diverse ground properties reveals the dynamics of three ice wedges and adjacent ground in a low-centered polygon area in Svalbard. The monitoring documented ground displacements, the timing of crack generation, ground thermal and moisture conditions from the surface to the top permafrost, and snow conditions. The focus is on seasonal ground deformation in and around ice-wedge troughs, interannual variability of ice-wedge activity and thermal thresholds for ice-wedge cracking. Seasonal ice-wedge activity is mainly associated with frost heave and thaw settlement, as well as thermal expansion and contraction. In mid- to late winter, temporary expansion and cracking of troughs by thermal contraction occurs during rapid cooling periods. Following intensive ground microcracking events, troughs show rapid expansion and in some cases major cracking in the frozen active layer. A common threshold for cracking is identified by a combination of ground surface cooling below -20°C and a thermal gradient steeper than -10°C m-1 in the upper meter of ground, indicating that cracking requires both a brittle frozen layer and rapid ground cooling. Our results highlight that in marginal thermal conditions for ice-wedge activity, the primary control on ice-wedge cracking is rapid winter cooling enhanced by minimum snow cover. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1985
2019023257 Messenzehl, Karoline (University of Bonn, Department of Geography, Bonn, Germany); Viles, Heather; Otto, Jan-Christoph; Ewald, Andreas and Dikau, Richard. Linking rock weathering, rockwall instability and rockfall supply on talus slopes in glaciated hanging valleys (Swiss Alps): Permafrost and Periglacial Processes, 29(3), p. 135-151, illus. incl. 3 tables, geol. sketch map, 33 ref., September 2018.
In high-alpine valleys undergoing glacier retreat, the spatial distribution of talus slopes and their sediments have been frequently used as a proxy for rockfall activity. However, within this 'sediment-dominated' research focus, the deglaciated source rockwalls are often portrayed in an oversimplified way. Here, we investigate 12 rockwall-talus systems in three glaciated hanging valleys in the Swiss Alps and explore the role of source rockwalls on the spatial pattern of talus slopes and their paraglacial rockfall activity. Data from field-based talus slope surveys, rockwall geotechnical studies, rock temperature monitoring, frost cracking modeling and GIS-based topoclimatic analyses are evaluated by ergodic reasoning in a principal component analysis to identify patterns of rockwall-talus systems with respect to their topoclimatic, rock mechanical and paraglacial controls. The results show that four main factors (frost cracking, permafrost probability, rockwall morphometry and mechanical preconditioning by rock mass strength and joint orientation) combine to dictate the paraglacial and spatial variability of sediment production, rockfall activity and block size. Our study demonstrates that more emphasis must be given to source rockwalls as their instability and weathering are directly linked to landform and material characteristics of talus deposits. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1976
2019023261 Opel, Thomas (University of Sussex, Department of Geography, Brighton, United Kingdom); Meyer, Hanno; Wetterich, Sebastian; Laepple, Thomas; Dereviagin, Alexander and Murton, Julian. Ice wedges as archives of winter paleoclimate; a review: Permafrost and Periglacial Processes, 29(3), p. 199-209, illus. incl. 1 table, 30 ref., September 2018.
Ice wedges are a characteristic feature of northern permafrost landscapes and grow mainly by snowmelt that refreezes in thermal contraction cracks that open in winter. In high latitudes the stable-isotope composition of precipitation (d18O and dD) is sensitive to air temperature. Hence, the integrated climate information of winter precipitation is transferred to individual ice veins and can be preserved over millennia, allowing ice wedges to be used to reconstruct past winter climate. Recent studies indicate a promising potential of ice-wedge-based paleoclimate reconstructions for more comprehensive reconstructions of Arctic past climate evolution. We briefly highlight the potential and review the current state of ice-wedge paleoclimatology. Existing knowledge gaps and challenges are outlined and priorities for future ice-wedge research are suggested. The major research topics are (1) frost cracking and infilling dynamics, (2) formation and preservation of the stable-isotope information, (3) ice-wedge dating, (4) age-model development and (5) interpretation of stable-isotope time series. Progress in each of these topics will help to exploit the paleoclimatic potential of ice wedges, particularly in view of their unique cold-season information, which is not adequately covered by other terrestrial climate archives. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1980
2019023258 Pruessner, Luisa (ETH Zurich, Laboratory of Hydraulics, Hydrology and Glaciology, Zurich, Switzerland); Phillips, Marcia; Farinotti, Daniel; Hoelzle, Martin and Lehning, Michael. Near-surface ventilation as a key for modeling the thermal regime of coarse blocky rock glaciers: Permafrost and Periglacial Processes, 29(3), p. 152-163, illus. incl. 1 table, sketch map, 44 ref., September 2018.
In a changing climate, ice-rich permafrost features such as rock glaciers will experience drastic changes. Modeling the heat transport through the blocky surface layer with its large interstitial pore spaces poses some challenges as various modes of non-conductive heat transport-advective forms in particular-can occur. Here, we show that the 1D physics-based model SNOWPACK can be used with a suitably adapted parameterization of ventilation to represent heat transport with reasonable accuracy. To do so, only one site-specific parameter, which is linked to the size of the pores in the blocky layer, is used. Inclusion of this ventilation parameterization is shown to be important for modeling the thermal regime at three experimental sites in the Swiss Alps. Furthermore, it could be shown that (i) snow depth dynamics exert a strong control on the thermal regime, (ii) the ice-content stratigraphy needs to be known precisely and (iii) the augmented heat flux through the blocky layer caused by ventilation in both snow and blocks is important. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1978
2019023260 Wetterich, Sebastian (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Schirrmeister, Lutz; Nazarova, Larisa; Palagushkina, Olga; Bobrov, Anatoly; Pogosyan, Lilit; Savelieva, Larisa; Syrykh, Liudmila; Matthes, Heidrun; Fritz, Michael; Günther, Frank; Opel, Thomas and Meyer, Hanno. Holocene thermokarst and pingo development in the Kolyma Lowland (NE Siberia): Permafrost and Periglacial Processes, 29(3), p. 182-198, illus. incl. 3 tables, sketch map, 25 ref., September 2018.
Ground ice and sedimentary records of a pingo exposure reveal insights into Holocene permafrost, landscape and climate dynamics. Early to mid-Holocene thermokarst lake deposits contain rich floral and faunal paleoassemblages, which indicate lake shrinkage and decreasing summer temperatures (chironomid-based TJuly) from 10.5 to 3.5 cal kyr BP with the warmest period between 10.5 and 8 cal kyr BP. Talik refreezing and pingo growth started about 3.5 cal kyr BP after disappearance of the lake. The isotopic composition of the pingo ice (d18O-17.1±0.6 ppm, dD -144.5±3.4 ppm, slope 5.85, deuterium excess -7.7±1.5 ppm) point to the initial stage of closed-system freezing captured in the record. A differing isotopic composition within the massive ice body was found (d18O-21.3±1.4 ppm, dD-165±11.5 ppm, slope 8.13, deuterium excess 4.9±3.2 ppm), probably related to the infill of dilation cracks by surface water with quasi-meteoric signature. Currently inactive syngenetic ice wedges formed in the thermokarst basin after lake drainage. The pingo preserves traces of permafrost response to climate variations in terms of ground-ice degradation (thermokarst) during the early and mid-Holocene, and aggradation (wedge-ice and pingo-ice growth) during the late Holocene. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1979
2019023259 Wolter, Juliane (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research Section, Potsdam, Germany); Lantuit, Hugues; Wetterich, Sebastian; Rethemeyer, J. and Fritz, Michael. Climatic, geomorphologic and hydrologic perturbations as drivers for mid- to late Holocene development of ice-wedge polygons in the western Canadian Arctic: Permafrost and Periglacial Processes, 29(3), p. 164-181, illus. incl. 4 tables, sketch map, 44 ref., September 2018.
Ice-wedge polygons are widespread periglacial features and influence landscape hydrology and carbon storage. The influence of climate and topography on polygon development is not entirely clear, however, giving high uncertainties to projections of permafrost development. We studied the mid- to late Holocene development of modern ice-wedge polygon sites to explore drivers of change and reasons for long-term stability. We analyzed organic carbon, total nitrogen, stable carbon isotopes, grain size composition and plant macrofossils in six cores from three polygons. We found that all sites developed from aquatic to wetland conditions. In the mid-Holocene, shallow lakes and partly submerged ice-wedge polygons existed at the studied sites. An erosional hiatus of ca 5000 years followed, and ice-wedge polygons re-initiated within the last millennium. Ice-wedge melt and surface drying during the last century were linked to climatic warming. The influence of climate on ice-wedge polygon development was outweighed by geomorphology during most of the late Holocene. Recent warming, however, caused ice-wedge degradation at all sites. Our study showed that where waterlogged ground was maintained, low-centered polygons persisted for millennia. Ice-wedge melt and increased drainage through geomorphic disturbance, however, triggered conversion into high-centered polygons and may lead to self-enhancing degradation under continued warming. Abstract Copyright (2018), John Wiley & Sons, Ltd.
DOI: 10.1002/ppp.1977
2019022619 Wang, Lingxiao (Ludwig-Maximilians-Universität München, Department of Geography, Munich, Germany); Marzahn, Philip; Bernier, Monique and Ludwig, Ralf. Mapping permafrost landscape features using object-based image classification of multi-temporal SAR images: ISPRS Journal of Photogrammetry and Remote Sensing, 141, p. 10-29, illus. incl. 9 tables, sketch map, 105 ref., July 2018.
Microwave imagery has a distinct advantage over optical imagery in high-latitude areas because it allows data to be acquired independently of cloud cover and solar illumination. Synthetic aperture radar (SAR)-based monitoring has become increasingly important for understanding the state and dynamics of permafrost landscapes at the regional scale. This study presents a permafrost landscape mapping method that uses multi-temporal TerraSAR-X backscatter intensity and interferometric coherence information. The proposed method can classify permafrost landscape features and map the two most important features in sub-arctic permafrost environments: permafrost-affected areas and thermokarst ponds. First, a land cover map is generated through the combined use of object-based image analysis (OBIA) and classification and regression tree (CART) analysis. An overall accuracy of 98% is achieved when classifying rock and water bodies, and an accuracy of 79% is achieved when discriminating between different vegetation types with one year of single-polarized acquisitions. Second, the distributions of the permafrost-affected areas and thermokarst ponds are derived from the classified landscapes. Permafrost-affected areas are inferred from the relationship between vegetation cover and the existence of permafrost, and thermokarst pond distributions are directly inherited from the land cover map. The two mapped features exhibit good agreement with manually delineated references. The proposed method can produce permafrost landscape maps in complex sub-arctic environments and improve our understanding of the effects of climate change on permafrost landscapes. This classification strategy can be transferred to other time-series SAR datasets, e.g., Sentinel-1, and other heterogeneous environments.
DOI: 10.1016/j.isprsjprs.2018.03.026
2019023053 Wu Leyang (China Pharmaceutical University, School of Life Science and Technology, Nanjing, China); Ali, Daniel C.; Liu Peng; Peng Cheng; Zhai Jingxin; Wang Ying and Ye Boping. Degradation of phenol via ortho-pathway by Kocuria sp. strain TIBETAN4 isolated from the soils around Qinghai Lake in China: PLoS One, 2018(e0199572), illus. incl. 3 tables, 47 ref., June 27, 2018.
Based on the feature of high-altitude permafrost topography and the diverse microbial ecological communities of the Qinghai-Tibetan Plateau, soil samples from thirteen different collection points around Qinghai lake were collected to screen for extremophilic strains with the ability to degrade phenol, and one bacterial strain recorded as TIBETAN4 that showed effective biodegradation of phenol was isolated and identified. TIBETAN4 was closely related to Kocuria based on its observed morphological, molecular and biochemical characteristics. TIBETAN4 grew well in the LB medium at pH 7-9 and 0-4% NaCl showing alkalophilicity and halophilism. The isolate could also tolerate up to 12.5 mM phenol and could degrade 5 mM phenol within 3 days. It maintained a high phenol degradation rate at pH 7-9 and 0-3% NaCl in MSM with 5 mM phenol added as the sole carbon source. Moreover, TIBETAN4 could maintain efficient phenol degradation activity in MSM supplemented with both phenol and glucose and complex water environments, including co-culture Penicillium strains or selection of non-sterilized natural lake water as a culture. It was found that TIBETAN4 showed enzymatic activity of phenol hydroxylase and catechol 1,2-dioxygenase after induction by phenol and the corresponding genes of the two enzymes were detected in the genome of the isolate, while catechol 2,3-dioxygenase or its gene was not, which means there could be a degradation pathway of phenol through the ortho-pathway. The Q-PCR results showed that the transcripts of both the phenol hydroxylase gene and catechol 1,2-dioxygenase gene were up-regulated under the stimulation of phenol, demonstrating again that the strain degraded phenol via ortho-degradation pathway.
DOI: 10.1371/journal.pone.0199572
2019021317 Mohammed, Aaron A. (University of Calgary, Department of Geoscience, Calgary, AB, Canada); Kurylyk, Barret L.; Cey, Edwin E. and Hayashi, Masaki. Snowmelt infiltration and macropore flow in frozen soils; overview, knowledge gaps, and a conceptual framework: Vadose Zone Journal, 17, 15 p., illus. incl. 2 tables, 124 ref., 2018.
Macropore flow in frozen soils plays a critical role in partitioning snowmelt at the land surface and modulating snowmelt-driven hydrological processes. Previous descriptions of macropore flow processes in frozen soil do not explicitly represent the physics of water and heat transfer between macropores and the soil matrix, and there is a need to adapt recent conceptual and numerical models of unfrozen macropore flow to account for frozen ground. Macropores remain air filled under partially saturated conditions, allowing preferential flow and meltwater infiltration prior to ground thaw. Nonequilibrium gravity-driven flow can rapidly transport snowmelt to depths below the frost zone or, alternatively, infiltrated water may refreeze in macropores and restrict preferential flow. As with unfrozen soils, models of water movement in frozen soil that rely solely on diffuse flow concepts cannot adequately represent unsaturated macropore hydraulics. Dual-domain descriptions of unsaturated flow that explicitly define macropore hydraulic characteristics have been successful under unfrozen conditions but need refinement for frozen soils. In particular, because pore connectivity and hydraulic conductivity are influenced by ice content, modeling schemes specifying macropore-matrix interactions and refreezing of infiltrating water are critical. This review discusses the need for research on the interacting effects of macropore flow and soil freeze-thaw and the integration of these concepts into a framework of coupled heat and water transfer. As a result, it proposes a conceptual model of unsaturated flow in frozen macroporous soils that assumes two interacting domains (macropore and matrix) with distinct water and heat transfer regimes.
DOI: 10.2136/vzj2018.04.0084
2019020582 Burkhart, Patrick A. (Slippery Rock University, Department of Geography, Geology, and the Environment, Slippery Rock, PA); Alley, Richard B.; Thompson, Lonnie G.; Balog, James D.; Baldauf, Paul E. and Baker, Gregory S. Savor the cryosphere: GSA Today, 27(8), p. 4-11, illus. incl. sketch maps, 45 ref., August 2017.
This article provides concise documentation of the ongoing retreat of glaciers, along with the implications that the ice loss presents, as well as suggestions for geoscience educators to better convey this story to both students and citizens. We present the retreat of glaciers-the loss of ice-as emblematic of the recent, rapid contraction of the cryosphere. Satellites are useful for assessing the loss of ice across regions with the passage of time. Ground-based glaciology, particularly through the study of ice cores, can record the history of environmental conditions present during the existence of a glacier. Repeat photography vividly displays the rapid retreat of glaciers that is characteristic across the planet. This loss of ice has implications to rising sea level, greater susceptibility to dryness in places where people rely upon rivers delivering melt water resources, and to the destruction of natural environmental archives that were held within the ice. Warming of the atmosphere due to rising concentrations of greenhouse gases released by the combustion of fossil fuels is causing this retreat. We highlight multimedia productions that are useful for teaching this story effectively. As geoscience educators, we attempt to present the best scholarship as accurately and eloquently as we can, to address the core challenge of conveying the magnitude of anthropogenic impacts, while also encouraging optimistic determination on the part of students, coupled to an increasingly informed citizenry. We assert that understanding human perturbation of nature, then choosing to engage in thoughtful science-based decision-making, is a wise choice. This topic comprised "Savor the Cryosphere," a Pardee Keynote Symposium at the 2015 Annual Meeting in Baltimore, Maryland, USA, for which the GSA recorded supporting interviews and a webinar.
DOI: 10.1130/GSATG293A.1
2019022320 Muster, Sina (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Roth, Kurt; Langer, Moritz; Lange, Stephan; Aleina, Fabio Cresto; Bartsch, Annett; Morgenstern, Anne; Grosse, Guido; Jones, Benjamin; Sannel, A. Britta K.; Sjoberg, Ylva; Günther, Frank; Andresen, Christian; Veremeeva, Alexandra; Lindgren, Prajna R.; Bouchard, Frédéric; Lara, Mark J.; Fortier, Daniel; Charbonneau, Simon; Virtanen, Tarmo A.; Hugelius, Gustaf; Palmtag, Juri; Siewert, Matthias B.; Riley, William J.; Koven, Charles D. and Boike, Julia. PeRL; a circum-Arctic permafrost region pond and lake database: Earth System Science Data (ESSD), 9(1), p. 317-348, illus. incl. 11 tables, 72 ref., 2017. Includes appendices.
Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i.e., waterbodies with surface areas smaller than 1.0 ´ 104 m2, have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5 m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6 m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1.4 ´ 106 km2 across the Arctic, about 17% of the Arctic lowland (< 300 m a.s.l.) land surface area. PeRL waterbodies with sizes of 1.0 ´ 106 m2 down to 1.0 ´ 102 m2 contributed up to 21% to the total water fraction. Waterbody density ranged from 1.0 ´ 10 to 9.4 ´ 101 km-2. Ponds are the dominant waterbody type by number in all landscapes representing 45-99% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost landscapes including detailed metadata are available at URL: https://doi.pangaea.de/10.1594/PANGAEA.868349.
DOI: 10.5194/essd-9-317-2017
|
|
2019023645 Linge, Henriette (University of Bergen, Department of Earth Science, Bergen, Norway); Matthews, John A.; Nesje, Atle; Fabel, Derek_D. and Xu, Sheng. 10Be surface exposure ages from relict talus-derived rock glacier lobes at Oyberget, Southern Norway [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 207-1, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Lobate, coarse rock-debris accumulations are found at 500-550 m a.s.l. beneath the south-facing wall of Oyberget (1225 m a.s.l.), upper Ottadalen, Southern Norway. The area is located inside the Younger Dryas margin of the Scandinavian Ice Sheet. Matthews et al. (2013, Permafrost and Periglacial Processes 24, 336-346) discussed whether these landforms are relict talus-derived rock glaciers or rock-slope failure accumulations, and concluded that the morphology is more consistent with the former. Three of the lobes were dated using Schmidt hammer surface exposure dating, yielding 10,340 ± 1280, 9920 ± 1385, and 8965 ± 1700 years, lobes 1, 2 and 3, respectively. The numerical ages are not compatible with the known, non-permafrost climatic conditions at the time. Two scenarios were suggested to explain the landform ages: (1) rapid early-Holocene paraglacial formation where residual glacial ice was buried by debris; or (2) a slower formation under permafrost conditions during an earlier interstadial with subsequent preservation beneath cold-based ice. 10Be surface exposure dating has been performed to test these two scenarios. Although both dating approaches rely on subaerial exposure, their measures of time rely on fundamentally different parameters affecting the rock surfaces - i.e. rate of chemical weathering versus accumulation of in situ cosmogenic nuclides. 10Be surface exposure dating of lobe 2 and 3 yields arithmetic mean ages of 10,142 ± 663 and 10,072 ± 1090 years (propagated 1-sigma analytical uncertainties). 10Be surface exposure dating further shows that the summit of Oyberget was ice free at 10,159 ± 599 years, whereas bedrock surfaces just up-valley of the lobes implies valley-floor deglaciation at 9042 ± 741 years. The similarity of the 10Be surface exposure ages from all four sites indicates that lobe formation and stabilization must have been very rapid, via paraglacial formation in the early Holocene, explicable by burial of residual ice in the valley by enhanced debris supply during deglaciation, possibly involving rock slope failure as well as talus material. The previous suggestion that the rock glaciers may have formed during the Mid-Weichselian, and survived beneath a cold-based ice sheet until renewed exposure during the early Holocene, is rejected.
2019020800 McKenzie, Jeffrey M. (McGill University, Department of Earth and Planetary Sciences, Montreal, QC, Canada); Walvoord, Michelle A.; Kurylyk, Barret L.; Bense, Victor F.; Fortier, Daniel; Spence, Chris and Grenier, Christophe. Is cryohydrogeology a catalyst for Arctic change? [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 84-12, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Climate change is transforming Arctic hydrologic systems and water resources with much of our knowledge based on data collected at or near the land surface from localized field studies or through remote sensing observations. While these studies yield extremely valuable information about shifts in surface water and ground ice distribution, river discharge, and soil moisture, the underpinnings of many of these water-related changes are linked to changing hydrogeologic conditions. Thawing of ancient permafrost is opening new subsurface pathways for groundwater flow, thereby altering fluxes and distribution of water, energy, and solutes. We identify different ways that these changes impact Northern society, including the potential for increased contaminant transport, modification to water resources, and enhanced rates of infrastructure (e.g. buildings and roads) damage. Further, as permafrost thaws it allows groundwater to transport carbon and nutrients from terrestrial to aquatic environments via progressively deeper subsurface flowpaths. Groundwater has the potential to catalyze a positive feedback on environmental change in the Arctic and is a critical component of the narrative of how the Arctic will respond to climate change, both physically and socially. Our presentation argues for the inclusion of cryohydrogeology, the study of groundwater in cold regions, within transdisciplinary Northern research initiatives.
2019018913 Mylroie, Joan R. (Mississippi State University, Department of Geosciences, Mississippi State, MS) and Mylroie, John E. Speleogenesis in the Quaternary; the present is not the key to the past [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 51-7, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Continental glaciations, as have occurred in the Quaternary, are rare in Phanerozoic earth history, prior major events being in the Late Ordovician, Early Devonian, Mississippian/Pennsylvanian boundary, and Permian. The rarity of glaciations is primarily caused by plate tectonics and the resultant infrequent episodic presence of continents at polar latitudes, and secondarily by climatic forcing (e.g. Melankovitch orbital variations). Speleogenesis under the conditions of rapidly changing glacioeustatic sea level, isostatic near and far field effects, atmospheric CO2 changes, glacial erosion and deposition, and fluctuating temperature and precipitation regimes is very different than the more stable conditions of most of Phanerozoic time. Cave development during earlier global glaciations is almost totally unrepresented in the modern rock record; paleokarst caves therefore reflect genesis at times of relative global climatic stability. While ice contact and proximity effects of ice excavation and deposition, permafrost, and extreme glacial melt water events on speleogenesis are obvious, global effects such as glacioeustasy and local climate changes are often not considered. The shift of the American Southwest from "pluvial" to arid conditions at the Pleistocene to Holocene transition, as also occurred in the Sahara Desert, indicate that even land-locked areas far from the glacial margin did not escape modification of speleogenetic rates and outcomes. Sea-level changes affected all coasts, and as a result of consequent base-level changes, areas deeper into continents. Do the caves we explore and study today reflect mostly fundamental processes common across geologic time, or are they overprinted by glacial and interglacial cycling that obscures those processes? Karst caves in the Quaternary have commonly survived multiple glaciations, and re-established flow paths from the past while simultaneously adjusting to new deranged landscapes. It is suggested that speleogenesis is a robust yet sensitive phenomena that produces karst caves that are a long duration, high fidelity record of earth processes.
2019023655 Patton, Annette I. (Colorado State University, Department of Geosciences, Fort Collins, CO); Rathburn, Sara L.; Capps, Denny M. and Brown, Ryan A. Landslide response to climate change in permafrost regions [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 207-11, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Rapid permafrost thaw in the arctic and subarctic increases hillslope susceptibility to landsliding by altering physical and hydrologic properties of hillslope materials, including reduced cohesion and increased hydraulic connectivity. In this presentation, we evaluate the fundamental processes that increase landslide frequency in regions of permafrost thaw and the short term topographic response of hillslopes to shallow-angle landslides. We synthesize remote analysis with field methods including surficial geologic mapping and time-series terrestrial lidar surveys of small (<0.5 km2) landslides in Denali National Park and Preserve, Alaska. Notably, landslides primarily occur in susceptible lithologies (unconsolidated glacial deposits and weathered felsic volcanics) and on hillslopes with a bimodal distribution of slope angles. These results suggest that permafrost or ice-related processes are generating landslides on shallow angles, while rainfall-dominated initiation occurs at steeper slope angles. These shallow landslides result in topographic signatures that influence snow accumulation for at least two years. We also use a review of the literature and analysis of primary data to address five questions of fundamental and practical importance and suggest three key areas for future research and primary data production to fill gaps in the understanding of landslide regimes in permafrost regions.
2019019052 Wolfe, Stephen A. (Geological Survey of Canada, Ottawa, ON, Canada); Morse, Peter D.; Neudorf, Christina M.; Kokelj, Steven V.; Lian, Olav B. and O'Neill, H. Brendan. Contemporary sand wedge development in eolian settings of seasonally frozen ground [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 120-1, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Contemporary sand wedges and sand veins occur within active and stabilized aeolian settings in seasonally frozen ground, in the extensive discontinuous permafrost zone in Northwest Territories, Canada. The region has a subarctic continental climate with 291 mm a-1 precipitation, -4.1°C mean annual air temperature, warm summers (July mean 17.0°C), and cold winters (January mean -26.6°C). Five years of continuous observations indicate that interannual variation in winter air temperature and snow cover conditions control ground thermal regimes. At sandy aeolian sites, thin snow cover and high thermal conductivity promote rapid freezing, high rates of ground cooling, and low near-surface ground temperatures (-15 to -25°C). Thermal contraction cracking occurs to depths of 1.2 m. Cracking potentials are high in sandy soils when air temperatures are <-30°C, mean freezing season air temperatures are ≤&eq;-17°C, and snow cover is <0.15 m thick. In contrast, surface conditions in peatlands maintain permafrost, but thermal contraction cracking does not occur because thicker snow cover and the thermal properties of peat prolong freezeback and maintain higher winter ground temperatures. Radiocarbon dating, optical dating, and stratigraphic observations differentiates sand wedge types and formation histories. Thermal contraction cracks beneath bare sandy terrain become infilled with surface and/or host material during the thaw season. Epigenetic sand wedges with available surface sand for infill develop within former beach sediments beneath an active aeolian sand sheet. Narrower and deeper syngenetic wedges developed within actively aggrading aeolian sand sheets, whereas wider and shallower antisyngenetic wedges developed in areas of active erosion. Thermal contraction cracking beneath vegetation-stabilized surfaces leads to crack infilling by host sediments and overlying organic materials, with resultant downturning and subsidence of adjacent strata due to lack of available sediment for infill. Sand wedge development in seasonally frozen ground with limited surface sediment availability can result in stratigraphy similar to ice-wedge and composite-wedge pseudomorphs. Therefore, caution is recommended when interpreting this suite of forms and inferring paleoenvironments.
2019020799 Wolfe, Stephen A. (Geological Survey of Canada, Ottawa, ON, Canada); O'Neill, H. Brendan and Spence, Chris. Broad-scale watershed responses associated with ground ice in permafrost [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 84-11, 1 ref., November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Changes in precipitation and temperature regimes are affecting water budgets globally. Climate warming in Arctic regions can result in additional inputs to the hydrologic cycle from ground ice melt as permafrost degrades. Knowledge of ground ice type and distribution is necessary to understand potential impacts on thermokarst processes and hydrological system responses to climate change. The Permafrost map of Canada is the primary source depicting ground ice for the entire country, but mapping is based on the extrapolation of limited field data to broad physiographic units (Heginbottom et al., 1995). To address this knowledge gap, we present new models of three ground ice types (massive, wedge, segregated) for Canada, and link ice type and abundance to observed thermokarst and hydrologic processes in major northern watersheds. We use an expert-system approach to model ground ice evolution over the last 17 ka in a GIS, accounting for broad-scale environmental changes. Ground ice of medium-to-high abundance occurs within about 45% of the continuous permafrost zone in Canada. All ice types are abundant in the western Arctic Ocean seaboard watershed, where there is evidence that intensive hillslope thermokarst processes can enhance the export of water, sediment and solutes to ocean waters. Abundant segregated ice in low-relief Hudson Bay seaboard watersheds results in wetland and shallow thaw lake thermokarst development, though the influence on streamflow remains undefined. The Mackenzie and Nelson River watersheds include large areas without permafrost and a lower fraction of terrain underlain by ice-rich ground. In these major basins, the hydrological response may be primarily through permafrost degradation that enhances subsurface flow pathways and increases baseflow. Reference: Heginbottom, J. A., Dubreuil, M. A., & Harker, P. A. C. (1995). Permafrost - Canada. Plate 2.1, MCR4177, National Atlas Information Service and Geological Survey of Canada, Ottawa, ON, Canada.
2019023007 Allen, Simon (University of Zurich, Department of Geography, Zurich, Switzerland); Frey, Holger; Huggel, Christian; Krautblatter, Michael; Haeberli, Wilfried; Chiarle, Marta and Geertsema, Marten. A technical guidance document for the assessment of glacier and permafrost hazards in mountain regions [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-13920, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Hazards relating to glaciers and permafrost are a threat to lives and livelihoods in many mountain regions. In view of rapid global warming and related changes in the mountain cryosphere, landscapes are evolving and new threats are emerging. Coupled with ongoing expansion of people and their infrastructure into high mountain valleys there is an increasing potential for societal losses and far-reaching disasters. Recognizing the need for a structured and comprehensive approach to hazard assessment underpinned by latest scientific understanding, the Joint Standing Group on Glacier and Permafrost Hazards in High Mountains (GAPHAZ) of the International Association of Cryospheric Sciences (IACS) and the International Permafrost Association (IPA) has produced a technical guidance document as a resource for international and national agencies, responsible authorities and private companies. Two core components were distinguished within an assessment framework; 1) Susceptibility and stability assessment: identifying where from, and how likely hazard processes are to initiate; 2) Impact assessment: identifying the potential threat from the hazard for downslope and downstream areas, and providing the scientific basis for decision making and planning. The guidance document provides several illustrative examples from the Peruvian Andes, demonstrating how the assessment framework can be applied in the case of cascading, chain reaction events. It is meant as a tool for experts in charge of hazard evaluations, reflecting current scientific state-of-the-art, but does not intend to replace the knowledge and experience required for such assessments. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-13920.pdf
2019023008 Altena, Bas (University of Oslo, Department of Geosciences, Oslo, Norway) and Kaab, Andreas. Daily cubesat imagery to observe and assess processes in the cryosphere [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14202, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The Planet constellation currently consist of 170+ high resolution optical cube-sats. This satellite constellation senses the globe with a daily revisit rate at a resolution of 3.7 meters in four bands. Apart from supporting the International Charter for Space and Major Disasters, their data is available and can be used for research on smaller events in the cryosphere. In this contribution we show some case studies to highlight the specific strong points of this constellation. The combination of high resolution imagery and daily coverage, makes this constellation ideal for monitoring of glacial lakes and drainage thereof. Supraglacial lake drainage can be monitored through a visual ruler and this is shown for an Alaskan glacier. The Planet constellation continuously points nadir, hence it does not need to be programmed to be pointed towards a site of interest. Consequently, unexpected events are recorded can be analyzed in retrospect. We show a case study of a crack propagation of marine terminating glaciers in British Columbia just prior to a major collapse of the calving front. Furthermore, data from the Planet constellation has a fast downlink and processing chain, thus typically data is available at the same day. This makes it possible to monitor the progress of moving ice afloat on rivers, its evolution over time is shown for a site in Siberia. The last case shows permafrost related rock fall analysis which can be done, examples are shown for the Alps or Scandinavia. The Planet constellation is another step forward in better recording of the Earth surface and especially useful for risk assessments in remote areas such as the cryosphere. With this contribution and this suit of case-studies we hope to motivate others to consider to use and explore this data. Hopefully leading to a better understanding of these processes and reduce the impact of natural hazards. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14202.pdf
2019022989 Amann, Florian (RWTH Aachen, Aachen, Germany); Kos, Andrew; Phillips, Marcia and Kenner, Robert. The Piz Cengalo Bergsturz and subsequent debris flows [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14700, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
On 27.12.2011 a rock volume of approximately 1.5 Million m3 failed catastrophically from the NE face causing a rock avalanche that travelled about 1.5 km down the Bondasca valley. Following the event, blue ice was observed on the vertical release scarp, leading to questions about the role of permafrost on the rock slope instability. In 2012, the ArgeAlp research project commenced focusing on geological and kinematic analysis, quantification of slope displacements using terrestrial radar interferometry and laser scanning, and analysis of ongoing rock fall activity Geological analysis showed that NE directed toppling was the dominant failure mechanism. Periodic measurements between 2012 and 2015 showed displacements of few cm/year. From 2015 to 2016 an increase in displacement rate was recognized with a further, major increase in rate between 2016 and 2017. The latter increase in displacement rate triggered the attention of the authorities in early August 2017. In addition to displacement measurements unambiguous warning signs were observed, characterized by a major increase in rock fall activity. The first major rock fall event occurred on the 21.08.2017 followed two days later by a catastrophic collapse with a volume of 3.15 Million m3 on 23.08.2017 at 9:30. Within a relatively short time after the catastrophic failure a series of debris flow events impacted the village of Bondo leading to its evacuation. This presentation summarizes the event history, geological investigations, displacement monitoring and provides key discussion points on potential factors that may have led to progressive failure, collapse of the Piz Cengalo NE rock slope and the mobility of the rock avalanche material. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14700.pdf
2019022988 Angelopoulos, Michael (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Westermann, Sebastian; Overduin, Pier Paul; Faguet, Alexey; Olenchenko, Vladimir and Grosse, Guido. Heat and salt flow in subsea permafrost modelled with CryoGRID2 [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-15864, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Degradation of sub-aquatic permafrost can impact offshore infrastructure, affect coastal erosion and release large quantities of methane, which may reach the atmosphere and function as a positive feedback to climate warming. The degradation rate depends on the duration of inundation, warming rate, sediment characteristics, the coupling of the bottom to the atmosphere through bottom-fast ice, and brine injections into the sediment. We apply the Cryo-GRID2 model, coupled to a salt diffusion model, to near-shore subsea permafrost thawing offshore of the Bykovsky Peninsula in Siberia. We model permafrost through multiple settings, including 1) terrestrial permafrost, 2) shallow sea with ice grounding, and 3) shallow offshore sea (<=5.3 m depth) without ice grounding. The model uses a terrestrial permafrost temperature of -10°C at the depth of zero annual amplitude, based on borehole observations, and a coastal erosion rate of 0.5 m/year, based on historical remote sensing imagery dating back to 1951. The seawater salinity prior to ice formation is based on a series of conductivity, temperature, and depth (CTD) measurements from summer 2017, as well as from Soil Moisture and Ocean Salinity (SMOS) satellite data. Water depth is available from echo-sounding surveys made in parallel with floating electrode electrical resistivity surveys in summer 2017. The model outputs are compared to the depth of the ice-bearing permafrost table (IBPT) determined from an electrical resistivity survey perpendicular to the shoreline. The floating electrode survey was combined with a terrestrial resistivity survey to show the transition from undisturbed terrestrial permafrost to submerged permafrost. The geoelectric surveys show a gently inclining IBPT table perpendicular to the coastline, which can be explained by a decreasing rate of degradation with increasing period of inundation. As the inundation period increases, the diffusive (heat and salt) gradients become less steep. The IBPT is located 20 m below the seabed 300 m offshore, which corresponds to 600 years of coastal erosion and an average IBPT degradation rate of 0.33 m per decade. The modelling results show an IBPT 18 m below the seabed and salty sediment up to 14 m below the seabed 300 m offshore. Therefore, the modelling results agree, at least qualitatively, with the sediment state inferred from the geoelectric data. Coupled heat and salt diffusion produces profiles of temperature and salt concentration in sediment as a function of time. The inclusion of salt flow in thermal models is particularly important in shallow waters where cryotic sediments form due to negative benthic water temperatures or ice grounding, because the depressed freezing point produced by salt diffusion can delay or prevent ice formation in the sediments and enhance the IBPT degradation rate. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-15864.pdf
2019023011 Bartsch, Annett (Zentralanstalt für Meteorologie und Geodynamik, Vienna, Austria); Grosse, Guido; Kaab, Andreas; Westermann, Sebastian; Strozzi, Tazio; Wiesmann, Andreas; Duguay, Claude; Seifert, Frank Martin; Obu, Jaroslav; Nitze, Ingmar; Heim, Birgit; Haas, Antonie and Widhalm, Barbara. Examining environmental gradients with satellite data in permafrost regions; the current state of the ESA DUE GlobPermafrost initiative [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-16612, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Permafrost cannot be directly detected from space, but many surface features of permafrost terrains and typical periglacial landforms are observable with a variety of EO sensors ranging from very high to medium resolution at various wavelengths. In addition, landscape dynamics associated with permafrost changes and geophysical variables relevant for characterizing the state of permafrost, such as land surface temperature or freeze-thaw state can be observed with space-based Earth Observation. Suitable regions to examine environmental gradients across the Arctic have been defined in a community white paper (Bartsch et al. 2014). These transects have been revised and adjusted within the DUE GlobPermafrost initiative of the European Space Agency. The ESA DUE GlobPermafrost project develops, validates and implements Earth Observation (EO) products to support research communities and international organisations in their work on better understanding permafrost characteristics and dynamics. Prototype product cases will cover different aspects of permafrost by integrating in situ measurements of subsurface properties and surface properties, Earth Observation, and modelling to provide a better understanding of permafrost today. The project will extend local process and permafrost monitoring to broader spatial domains, support permafrost distribution modelling, and help to implement permafrost landscape and feature mapping in a GIS framework. It will also complement active layer and thermal observing networks. Both lowland (latitudinal) and mountain (altitudinal) permafrost issues are addressed. The status of the Permafrost Information System and first results will be presented. Prototypes of GlobPermafrost datasets include: Modelled mean annual ground temperature by use of land surface temperature and snow water equivalent from satellites Land surface characterization including shrub height, land cover and parameters related to surface roughness Trends from Landsat Time series over selected transects For selected sites: subsidence, ground fast lake ice, land surface features and rock glacier monitoring Bartsch, Annett; Allard, Michel; Biskaborn, Boris Kolumban; Burba, George; Christiansen, Hanne H.; Duguay, Claude R.; Grosse, Guido; Gunther, Frank; Heim, Birgit; Hogstrom, Elin; Kaab, Andreas; Keuper, Frida; Lanck-man, Jean-Pierre; Lantuit, Hugues; Lauknes, Tom Rune; Leibman, Marina O.; Liu, Lin; Morgenstern, Anne; Necsoiu, Marius; Overduin, Pier Paul; Pope, Allen; Sachs, Torsten; Sejourne, Antoine; Streletskiy, Dmitry A.; Strozzi, Tazio; Ullmann, Tobias; Ullrich, Matthias S.; Vieira, Goncalo; Widhalm, Barbara (2014): Requirements for monitoring of permafrost in polar regions - A community white paper in response to the WMO Polar Space Task Group (PSTG), Version 4, 2014-10-09. Austrian Polar Research Institute, Vienna, Austria, 20 pp, hdl:10013/epic.45648.d001 [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-16612-1.pdf
2019023005 Bergstedt, Helena (University Salzburg, Interfaculty Department of Geoinformatics, Salzburg, Austria); Bartsch, Annett; Duguay, Claude and Zwieback, Simon. Temporal and spatial dependencies of microwave scattering mechanisms in high latitudes across scales [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-12787, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Permafrost and seasonal frost affect large parts of the Earth's surface, and are especially important features in high latitudes. Remote sensing has been utilized for Arctic research in numerous fields of study including Hydrology, Snow Science, Ecology and Geocryology. In permafrost research, microwave remote sensing has found many applications from deriving water bodies dynamics to surface state (freeze/thaw) distribution. Freeze/thaw determination requires the analysis of time series and is based on the assumption that backscatter changes uniformly over time for different landscape types when temperatures drop below zero degrees Celsius (autumn) or snow starts to melt (spring). In this study, we utilize C-band active microwave remote sensing datasets of different spatial and temporal resolutions (scatterometer and synthetic aperture radar (SAR)) together with ground temperature time series from the Global Terrestrial Network for Permafrost-Database (GTN-P) to characterize deviating patterns related to freeze/thaw. We explore issues of scale dependencies in freeze-thaw information derived from Advanced Scatterometer (ASCAT) and Advanced Synthetic Aperture Radar (ASAR) data. We also examine the implications of winter-time variability of backscatter time series for snow characteristics and freeze-thaw algorithms using Analysis of Covariance (ANCOVA) of near-surface temperature measurements and ASCAT backscatter time series. We found landscape type specific differences between datasets of differing spatial and temporal resolutions. Distinct differences were found for lake-rich landscapes during autumn, likely caused by lake-ice formation and forest dominated areas during spring. This lead us to further explore the influence of lake ice formation and break-up on backscatter signals using ASCAT and Sentinel-1 datasets. A further issue are winter-time backscatter variations which differ between continuous and non-continuous permafrost. The variations may relate to, for example, rain-on-snow events in warmer areas and a lower representativeness of coarse backscatter data in less homogeneous and warmer areas. Together, these results highlight spatial and temporal patterns in microwave backscatter time series which are essential for freeze/thaw determination. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-12787.pdf
2019022994 Bertone, Aldo (University of Pavia, Earth and Environmental Science, Italy); Callegari, Mattia; Cuozzo, Giovanni; Marin, Carlo; Notarnicola, Claudia; Seppi, Roberto and Zucca, Francesco. A novel methodology to classify rock glaciers using Sentinel-1 data [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-1197, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Rock glaciers are the most common geomorphological evidence of permafrost in alpine regions and are characterized by creeping processes that generate a downstream displacement, with speed rates ranging from a few cm to more than 1 meter per year. This displacement varies from year to year and seasonally and is influenced by several environmental factors. The slope instability related to rock glacier and permafrost dynamics is monitored for a proactive management of natural hazards. Moreover, as permafrost is sensitive to climate change, observing its dynamics is a key issue in alpine environment. Remote sensing is a modern technology to study remote areas at a large spatial scale and variable time scales. Airborne and satellite data, integrated with ground techniques such as GPS or UAV, can be used to detect and monitor rock glaciers, in order to inventory them and to study their activity. In this work we propose a novel automatic methodology to detect the rock glacier activity by exploiting Sentinel-1 SAR multitemporal images, with the aim to update and refine an existing inventory developed in South Tyrol (Eastern Alps, Italy). South Tyrol is an alpine region characterized by a widespread presence of rock glaciers, which were recently inventoried using remote sensing and field observations. In this inventory, the rock glacier activity was defined by visual interpretation of the available data. As in alpine areas the winter snow cover restricts the number of usable SAR images, making difficult the use of the multitemporal interferometry, we detected the terrain deformation by using amplitude and coherence information from Sentinel-1 data. In order to take into account, the ground changes (e.g. snowfall), we computed the amplitude variation between each pair of images,within each rock glacier. The pairs of images with a low variation in amplitude were then used for the classification. Subsequently, in order to detect the status of the rock glaciers (i.e. active or inactive), we addressed the coherence information. A low coherence inside the rock glacier area suggest that the landform has changed between the pairs of images, and this provide a good probability that the landform is active (i.e. in motion). This information is exploited in an unsupervised way using an expectation maximization algorithm to classify active and inactive rock glaciers. The new methodology developed enabled us to automatically define the activity status of rock glaciers. Of the 1542 landforms already inventoried in South Tyrol, 1147 have been re-classified by using our methodology. The number of rock glaciers has shown an agreement of about 84% with the existing inventory, of which 245 rock glaciers were listed as active. To validate the proposed methodology, the results were compared with an independent dataset of active landforms classified by the interpretation of geomorphic evidences visible in a digital orthophoto and a DTM from 2006. The unsupervised classification shows an agreement with the validation dataset of 74%, confirming the applicability of the new methodology. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-1197.pdf
2019020416 Bussmann, Ingeborg (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Germany); Damm, Ellen; Grosse, Guido; Overduin, Paul and Fedorova, Irina. Methane oxidation under ice-cover conditions in Siberian lakes, rivers, and coastal waters [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-4505, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Permafrost thaw affects global climate, the land surface and coastal structures. Under subaquatic conditions, permafrost thaw is often more rapid than on land. The thaw depth below water bodies (taliks) and changes in biogeochemical gradients are difficult to predict. The influence of taliks and biogeochemical gradients on the production and release of the greenhouse gases methane and carbon dioxide is not clear yet. Although our research in this region has produced multi-decadal data sets, most of our knowledge on the methane cycle pertains only to the summer. We focus on water bodies in the Lena Delta region, including thermokarst ponds, lakes, lagoons and the marine shoreface. For most of the year, however, ice covers these water bodies, creating a barrier between the water column and the atmosphere, and changing benthic conditions. It is therefore important to assess methane-related processes during the ice-covered season. In spring 2017 we investigated the Lena Delta and Tiksi Bay at the end of winter, while still ice-covered. Thirty ice cores of different water bodies were obtained by Kovacs ice corer. The in situ temperature of the ice cores was measured immediately afterwards. Methane oxidation rates were determined with radio tracer method in melted ice core samples. Analyses of methane concentration and further hydrochemical analyses are on their way. Initial results indicate rather low activities of methane oxidation in the ice cores, but active biological processes in the water below. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-4505.pdf
2019022999 Chen Yating (Beijing Normal University, College of Climate Change and Earth System Science, Beijing, China); Moore, John C. and Zhang Zhihua. Mitigation of carbon loss in circum-Arctic permafrost region through stratospheric aerosol geoengineering implement [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-6042, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Climate warming as a result of human activities causes permafrost region to thaw and release carbon to the atmosphere, representing the permafrost starts to shift from a carbon sink to a carbon source. Geoengineering, the deliberate large-scale manipulation of earth's energy balance in order to mitigate global warming, is an attractive proposition for mitigating carbon losses in circum-Arctic permafrost region. We use soil temperature data from seven earth system models and NCSCD's soil carbon data to predict the spatial-temporal variation of carbon stocks in permafrost region under RCP4.5 scenario and stratospheric aerosol Geoengineering (G4) from the Geoengineering Model Intercomparison Project between 2020-2090. The prediction is based on PInc-Panther approach and we have made some improvements for more detailed analysis. The effect of Geoengineering to mitigate permafrost thaw and reduce carbon loss is evaluated, and the rebound effect after Geoengineering stopped is discussed. We calculate emissions for the period 2020-2070 come from surface soils less than 3 m deep, as a result, a 66±22 Pg carbon loss in permafrost area under RCP4.5 and a 40±34 Pg carbon loss under G4 scenario. G4 reduces nearly 40% of carbon loss and 18% of methane emissions relative to the RCP45 scenario between 2020-2070. By 2090, due to the rebound effect, total carbon losses are 91±27 Pg under RCP4.5 and 82±32 Pg under G4 scenario. These estimates may be low because the thermokarst and deeper Yedoma deposits hadn't been taken into account and the model we used provides some possible sources of bias. Despite this, Geoengineering has played a role in mitigation of carbon loss in circum-Arctic permafrost region. In addition, by monthly analysis, we find the dominant month of Geoengineering is October and November. At 1-2 m and 2-3 m depths, G4 reduces carbon losses by 16% and 19% relative to RCP45, but in the 0-1 m, the role of G4 is not obvious. Thus the major contribution of Geoengineering has been to mitigate the deepening of permafrost degradation. By 2090, we predict a 6%-45% decrease in permafrost area and a 11-78 cm increase in active layer thickness. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-6042-1.pdf
2019022797 Clarke, Charlotte (University of Southampton, Geography and Environment, Southampton, United Kingdom); Alsos, Inger; Edwards, Mary; Bjune, Anne; Hughes, Paul; Gielly, Ludovic; Lammers, Youri; Mangerud, Jan; Haflidason, Haflidi and Svendsen, John Inge. Ancient DNA from northern Eurasian lakes reveals community dynamics of vascular plants over the past 25,000 years [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-1145, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Ancient DNA (aDNA) recovered from sediments in the Arctic and Subarctic has proved a useful new tool for studying change in terrestrial ecosystems over time. The cold and relatively dry conditions of the Arctic and Subarctic appear to be ideal for the preservation of extra-cellular (i.e. "environmental") DNA, particularly within permafrost and/or lake sediments. While the focus of work to date that uses aDNA retrieved from sediments has been vascular plants, information on bryophyte, invertebrate and vertebrate taxa has also been retrieved from sites in northern regions. We evaluate the potential of sedimentary ancient DNA (sedaDNA) to detect plant diversity and community dynamics over the past 25,000 years from lakes in the Eurasian Arctic. How DNA is recruited into lake sediments remains poorly understood, yet DNA retrieval may be related to features such as sediment quality, catchment size and inflowing streams. Here, we present sedaDNA records from lakes in northern Norway and the Polar Urals, which differ greatly in terms of their catchment size, sedimentary characteristics and glacial histories. The glacial finger lake (Bolshoye Shuchye) in the Polar Urals has a large and topographically catchment and clay-rich sediments, both of which may contribute to the rich DNA flora obtained. We obtained nearly 12 million sequence reads of 167 plant taxa from 153 lake-sediment samples, providing a level of ecological detail rarely obtained. Although displaying similar trends, the DNA record shows several features that the pollen stratigraphy failed to detect, including a turnover in grass genera over the Late Pleistocene to Holocene transition, the persistence of a diverse arctic-alpine forb flora into the Holocene and a diverse and variable bryophyte flora through time. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-1145.pdf
2019022852 Colucci, Renato Roberto (Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine, Department of Earth System Sciences and Environmental Technology, Basovizza, Italy). Glaciers and ice caves as interconnected features in the geomorphological evolution of the landscape of high karstic environments [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14865, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Glaciers and ground ice occurrence in high elevated karstic areas of the world have generally been seen and studied as separated aspects of the same topic: the mountain cryosphere. If mountain glaciers are considered to be sensitive indicators of climate variability, the lesser known part of the cryosphere is actually represented by high altitude ice caves, namely natural caves formed in bedrock (karstic massifs, but lava tubes as well) where perennial accumulation of ice is preserved. Being part of ground ice, ice caves are commonly considered as sporadic permafrost phenomena. The real distribution and the size of ground ice in mountain areas of the world remain still unknown, although recent studies suggest that the number of ice caves in the Alps could reach several thousand of units, thus representing a possible important source of freshwater storage in high altitude karstic areas. A critical topic in ice cave studies is the understanding of how the internal environment interacts with the external one and how these systems react to changes in thermal conditions and external ice cover. New insights on the fluid-dynamic behaviour of ice caves can be given by numerical methods thus improving and integrating the information that could be obtained from standard experimental measurements. This, in turns, could also lead to a more refined interpretation of the size and evolution of the paleocryosphere of such areas during colder glacial or warmer interglacial phases in order to improve the interpretation of the hydrological functioning of these areas with great impact on the geomorphological evolution of the landscape. A case study from the Southern Alps will be presented where a multidisciplinary research on past and present evolution of the cryosphere is undertaken. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14865-2.pdf
2019022883 Crichton, Katherine (University of Cardiff, School of Earth and Ocean Sciences, United Kingdom). Permafrost carbon controls d13CO2 during glacial termination T2 as well as T1; the importance of ice sheet size for land carbon stock [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-9107, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Paleo-data from glacial terminations provide us with a means of testing hypotheses on the processes controlling climate variability. During the last glacial termination, the concentration of CO2 in the atmosphere rose by around 80ppm between 18ka to 10ka BP. A significant drop in d13CO2 occurred in the early deglaciation, indicating a light carbon-13 source. We had previously shown that we could reproduce the evolution of CO2 and d13CO2 in the atmosphere during the last glacial termination (T1) in our model (CLIMBER-2), with a key component being permafrost-related soil carbon dynamics. During the penultimate glacial termination (T2, »140ka to 128ka BP), data shows a rise of CO2 of the same magnitude as T1, but a different evolution of d13CO2, especially so at the onset of the termination. In this work I will present simulations of T2, in which modelled CO2 and d13CO2 show a good agreement with data, as with T1. The size of ice sheets during the glacial maximum and the role of orbital forcing are essential in explaining the data evolution. The model successfully reproduces the previously unexplained 0.3 ppm difference between Last Glacial Maximum and Penultimate Glacial Maximum d13CO2, which I suggest is due to permafrost carbon and ice sheet interaction. This has implications for the interpretation of ocean d13C data. These simulations imply a system which does not require an AMOC shut down to promote a rise in atmospheric CO2 at the onset of these deglaciations, but does require the gradual release of carbon from the deep Southern Ocean to result in a complete glacial termination. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-9107-3.pdf
2019022666 Gasser, Thomas (International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria); Kechiar, Mehdi; Ciais, Philippe; Burke, Eleanor; Kleinen, Thomas; Zhu, Dan; Huang, Ye; Ekici, Altug and Obersteiner, Michael. Path-dependent reduction in emission budgets caused by permafrost CO2 and CH4 release [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14234, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Emission budgets are defined as the cumulative amount of anthropogenic CO2 emission compatible with a global temperature change target. The simplicity of the concept has made it attractive to policy-makers, yet it relies on a linear approximation of the global carbon-climate system's response to anthropogenic CO2 emissions. Here, we investigate how emission budgets are impacted by inclusion of CO2 and CH4 emissions caused by permafrost thaw, a non-linear process of the Earth system with some degree of irreversibility. We use the compact Earth system model OSCAR v2.2.1 and a new permafrost carbon emulator calibrated on four state-of-the-art land surface models that show a realistic representation of high-latitude processes: JSBACH, ORCHIDEE-MICT, and two versions of JULES. We investigate the "exceedance" and "avoidance" approaches for estimating emission budgets, as defined and used for the fifth IPCC assessment report. The exceedance approach is the only approach that complex Earth system models can follow, and we find that it only partially accounts for the effect of permafrost carbon release. We therefore discard this approach, as it is not suited for estimating budgets when slow non-linear and irreversible processes are involved. Following the avoidance approach, the emission budget for staying below 2°C (with a 50% chance) is reduced by 100 [20-270] GtCO2 if net negative emissions prove feasible, by 150 [30-340] GtCO2 if they do not, and by 190 [50-400] GtCO2 if the target is overshot by 0.5 C. This corresponds to reductions in the remaining budget of 8% [1-25%], 13% [2-35%], and 16% [3-44%], respectively. The fact that this permafrost-induced reduction depends on the emission scenario proves that emission budgets are made path-dependent by the inclusion of permafrost carbon release. Besides, our results also show that the effect of permafrost carbon release on emission budgets cannot be evaluated by naively subtracting cumulative permafrost emissions to existing budgets that do not include this process. Doing so disregards the complex dynamics of the coupled carbon-climate system. The specific contribution of CH4 emissions from permafrost is also investigated. We find it is path-dependent as well, since it amounts to 5% to 35% of the total permafrost effect, depending on the temperature target and the way this target is met. In overshooting scenarios, CH4 plays a less important role, because the target is met later on, and CH4 is a relatively short-lived greenhouse gas. Finally, for the 1.5 C target, reductions in the remaining budget range from 10% to more than 100%, indicating the budget may already have been exceeded. This would condemn humankind to removing more CO2 from the atmosphere than it will emit in the future, if this target is ever to be reached. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14234.pdf
2019023003 Heinrich, Georg (University of Graz, Department for Geography and Regional Sciences, Graz, Austria); Resch, Gernot; Prinz, Rainer; Bavay, Mathias and Schöner, Wolfgang. Applying the SNOWPACK model for permafrost investigations at Hoher Sonnblick, Austria [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-7970, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The overarching aim of the ATMOperm project is to improve the understanding of the impacts of atmospheric extreme events on the thermal state of the active layer using a combined measurement and modelling approach as the basis for a long-term permafrost monitoring strategy. For this purpose, the Sonnblick Observatory at the summit of Hoher Sonnblick (3106 m a.s.l.) is particularly well-suited due to its extensive permafrost monitoring (i.a., three 20 m deep boreholes equipped with temperature sensors since 2007) and comprehensive long-term atmospheric monitoring network. For the investigation of the impact of atmospheric extreme events on the active layer thickness (ALT), the one-dimensional physical based SNOWPACK model from the Swiss WSL Institute for Snow and Avalanche Research SLF (WSL/SLF) is used to determine the mass and energy exchange between the snow, the atmosphere and the soil. Manual snow depth measurements during 2016/2017 close to the location of the boreholes serve as basis for model calibration. For other years without snow depth measurements, the calibrated model will be evaluated in terms of snow disappearance date which can be inferred from borehole temperature measurements close to the surface. In a next step, the unknown soil properties will be calibrated based on the temporal evolution of error-corrected borehole temperatures in order to accurately represent the ALT. The calibrated model will then be driven by atmospheric input in order to investigate particular extreme cases such as the high summer temperatures in 2003. As errors in the measured ground temperatures would further propagate into misleading modeling results, we will first highlight the importance of post-processing and correction of the borehole temperature measurements. In this respect, the quality and reliability of the measured ground temperature data at the study site is improved and a novel methodological framework for the post-processing of the borehole temperature data is developed and presented. Moreover, we will show first results concerning model calibration and its evaluation and further analyze the modelled active layer thickness for selected observed extreme cases. Finally, we will discuss our strategy in investigating long-term changes in the mean state of the active layer and associated extreme events. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-7970-4.pdf
2019022985 Kneier, Fabian (Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Periglacial Research, Germany); Overduin, Pier Paul; Langer, Moritz; Boike, Julia and Grigoriev, Mikhail N. Reconstructing surface temperature trends during the last 200-300 years from permafrost borehole temperature records [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-1060, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Palaeotemperature reconstructions are valuable palaeoclimate indicators and important tools for the understanding of interactions in the climate system. They form a basis for models identifying the impact of various processes within the past and future climate system. Siberia is a region with large organic carbon reserves stored in permafrost (perennially frozen ground). Temperatures in this region are thus important as a driver for a positive feedback to the global climate. Local temperature histories in the ice-rich permafrost areas of the Russian Arctic are either sparse or based on proxy data with potential seasonal biases. Borehole temperature reconstructions are sensitive to the temperature signal throughout the year and available in regions for which no other records exist. This study used two inversion methods, particle swarm optimization and a least squares technique, to retrieve temperature histories of the last 200-300 years in the Laptev Sea region from two permafrost borehole temperature records. The retrieved histories were compared to larger scale reconstructions from the region. Distinct differences in the histories between the Lena Delta and western Laptev Sea sites were found, notably a one-century delay of warming and a three decade delay in peak warming in the western Laptev Sea. The local permafrost surface temperatures at Sardakh Island (central Lena Delta) resembled the circum-Arctic regional average trends. At Mamontov Klyk (western Laptev Sea) this was the case only for the most recent decade. In contrast, the Mamontov Klyk history was more similar to northern hemispheric mean trends. A rapid recent warming of synoptic scale was consistently observed at both sites. Differences in the past temperature trends between the sites may be caused by regionally differing environmental influences, such as atmospheric circulation and sea ice coverage. The reconstructed magnitude of temperature changes is consistent with warming greater than mean Arctic temperature trends. In conclusion, reconstruction from shallow permafrost boreholes provides short-scale temperature histories in the coastal tundra of the remote Arctic (resolved at annual to multi-decadal scale). As local differences from the circum-Arctic average--including later warming and higher warming magnitude--were shown to exist in this region, our results provide a basis for local surface temperature record parameterization of climate models and of permafrost models in particular. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-1060.pdf
2019022656 Knoblauch, Christian (University of Hamburg, Institute of Soil Science, Hamburg, Germany); Beer, Christian; Liebner, Susanne; Schütt, Alexander; Grigoriev, Mikhail N. and Pfeiffer, Eva-Maria. Importance of methane production for the greenhouse gas budget of thawing permafrost on climate relevant time scales [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-10583, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Permafrost in circum-arctic soils stores as much carbon as the global atmosphere. Permafrost thaw liberates organic matter, which is mineralized by microorganisms to carbon dioxide (CO2) and methane (CH4). The release of these greenhouse gases (GHGs) may form a positive feedback to atmospheric CO2 and CH4-concentrations and accelerate climate change. Methane, which has 28 to 45 times the global warming potential (GWP) of CO2 (100 years time scale), is formed by microorganisms in anoxic, water-saturated soils. Current studies indicate that permafrost thaw at the bottom of well drained (oxic) soils cause a higher formation of GHGs than in water saturated (anoxic) soils since more CO2 is formed under oxic conditions and only small amounts of CH4 are formed from permafrost organic matter under anoxic conditions. Here we show through 7-year laboratory incubations, molecular analysis and in-situ CH4-flux measurements that low CH4-production from Siberian permafrost organic matter is due to the lack of active methanogens. Equal amounts of organic carbon are mineralized to CO2 and CH4 under anoxic conditions after an active methanogenic community has established. An organic carbon decomposition model, calibrated with the collected long-term incubation data, predicts that 11.3% of initial permafrost carbon may be released as CO2 under oxic conditions until 2100 but only 1.7% and 2.2% as CO2 and CH4 under anoxic conditions, respectively. However, if considering the higher GWP of CH4, the production of CO2-C equivalents is more than twice as high under anoxic conditions. Field measurements of CH4-fluxes from recently thawed permafrost deposits in northeast Siberia demonstrated that thawed Pleistocene Yedoma sediments, although water saturated, did not release any CH4. Furthermore, no CH4-production could be observed in anoxic short-term (33 days) laboratory incubations. In contrast, if Pleistocene Yedoma sediments were mixed with surface material by thermo-erosion of Yedoma outcrops, CH4-fluxes of up to 180 mg m-2 d-1 were observed. The latter high CH4-fluxes are likely due to priming of thawing permafrost organic matter with active methanogenic communities from the surface soils. The presented data indicate that low CH4-production rates in short term incubations and recently thawed Pleistocene Yedoma sediments are due to a low abundance of methanogenic microorganisms that will increase over longer periods or by priming with methanogenic communities from surface soils. On longer, climate relevant time scales, GHG production from thawing permafrost organic matter will be higher under water-saturated conditions if considering the higher GWP of CH4. These findings challenge the current view of a higher permafrost carbon-climate feedback from well drained soils. Improved predictions on GHG fluxes from thawing permafrost require a better understanding of the distribution of water-saturated and well drained soils and on the change of soil hydrology in response to permafrost thaw on a circum-arctic scale. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-10583.pdf
2019020290 Köster, Egle (University of Helsinki, Institute for Atmospheric and Earth System Research/Forest Sciences, Helsinki, Finland); Berninger, Frank; Köster, Kajar; Aaltonen, Heidi; Zhou, Xuan; Zhang-Turpeinen, Huizhong; Prokushkin, Anatoly and Pumpanen, Jukka. Fire caused changes in CO2 and CH4 fluxes in Siberian permafrost forests [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-7070, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
About 70% (more than 520 million ha) of the world's boreal forests are situated in Russian Federation. It is estimated that these forest contain about 119 Pg of carbon, of which about 75% is stored in soils and forest floor material. This gives a significant role to the boreal forest of this region in global C balance. Generally these high latitude ecosystems are C sinks, as they absorb atmospheric carbon dioxide (CO2) through photosynthesis, and methanotrophic microorganisms of these well-drained and dry soils consume methane (CH4). Climate change induced rising air temperatures and precipitation rates in boreal ecosystems are changing the fire regimes (intervals, severity, intensity, etc.). Main impacts of the fire to the forest ecosystems are reported to be the changes in soil physical and chemical characteristics, vegetation stress, and degradation of permafrost and increased depth of active layer. Changes in these characteristics should consequently have an impact on the dynamics of CO2 and CH4 fluxes. We have studied the changes in CO2 and CH4 fluxes in boreal forest areas in central Siberia with permafrost base. The main aim was to estimate how time since the last forest fire influences the soil CO2 and CH4 fluxes in permafrost areas. We compared the fire chronosequence of areas (last fire occurred in 2015, 1993 and 1960) to a control area that had no fire for at least 100 years. We estimated the significance of experimental factors such as time since fire, soil temperature, soil moisture, depth of active layer, living and dead tree biomass and biomasses of grasses and mosses to influence the GHG fluxes across a fire chronosequence. The soils in our study acted as source of CO2 and sinks of CH4. The Obtained results confirm that the impacts of a forest fire on CO2 and CH4 fluxes are long-lasting in Siberian boreal forests - lasting even more than 50 years. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-7070.pdf
2019020294 Koster, Kajar (University of Helsinki, Institute for Atmospheric and Earth System Research, Department of Forest Sciences, Helsinki, Finland); Koster, Egle; Aaltonen, Heidi; Zhou, Xuan; Berninger, Frank and Pumpanen, Jukka. Forest fires and their effect on soil carbon turnover; comparison of permafrost and non-permafrost areas from Canada [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-6182, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Boreal forests, which cover 15% of the Earth's land area, are a crucial part of the climate system as they contain approximately 60% of the carbon (C) bound in global forest biomes and approximately 12-13% of the organic C stocks in the world's soils. The presence of permafrost (about 24% of the land in the Northern Hemisphere) makes these high latitude ecosystems especially vulnerable to changing climate The soil organic matter (SOM) pool in boreal forests is a particularly important C storage, with a long turnover time ranging from several decades to millennia. Even small changes in the turnover of soil C stocks there may reverse the terrestrial carbon sink into a source with consequent increase in the atmospheric CO2 concentrations. Fire is one of the most important natural disturbances in the boreal forest, strongly influencing boreal forest structure and function. Thus it is important to study the response of arctic forest soils to rising temperature and increased fire frequency and the present and future role of arctic forests in the global C cycle. In this study, we characterise the post-fire C dynamics (CO2 efflux, soil C content, soil C turnover times) along a fire chronosequences in northern boreal forests of north-western Canada. Our study areas were located along the Klondike Highway (non-permafrost areas) and Dempster Highway (permafrost areas), in Northwest Territories and Yukon, Canada. In the summer of 2015, four different study areas (each with a different time since the last stand replacing forest fire), were established both in permafrost areas and non-permafrost areas. The fire chronosequence in permafrost areas consisted areas with last forest fire in years 2012, 1990 and 1969, and fourth area was a control which had no fire for at least 100 years. The fire chronosequence in non-permafrost areas consisted areas with last forest fire in years 2013, 1969 and 1950, and a control area (no fire for at least 100) years. The dates of the fires were determined from the Yukon and Northwest Territories fire maps. At each fire chronosequence we established three 150 meter-long-lines with three sample plots along each line at 50 meter intervals. The lines were spaced by at least a few hundred meters from each other. We thus had nine sample plots per age class. The total C contents in the first 30 cm of the topsoil were lowest in newly burned areas and in general total soil C content was higher in areas with permafrost. Same trends were observed when soil CO2 effluxes were analyzed. The values were significantly lower in in newly burned areas and when permafrost and non-permafrost areas were compared the areas with permafrost were shoving about 1.5x higher values than non-permafrost areas. Thus, all in all soil C turnover time had no significant difference when permafrost and non-permafrost areas were compared. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-6182.pdf
2019020470 Lemaire, Morgane (Université Lille-CNRS, Physique des Lasers Atomes et Molécules, Lille, France); Chazallon, Bertrand; Pirim, Claire and Desmedt, Arnaud. Formation of gas hydrates from vapour deposition of nitrogen and water; an in-situ study by Raman spectroscopy [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-16389, 9 ref., 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Gas hydrates possess a potential for useful applications in many technical and industrial applications in the fields of energy and environmental research [1]. They can be found in a variety of natural environments such as hydrate-bearing marine sediments, the permafrost or even atmospheric aerosols [2]. Nitrogen-bearing clathrates occur naturally on Earth where they form small crystals of air-clathrates embedded in the ice matrix in polar ice core [3]. They are potentially astrophysical players in the formation of nebulae [4], comets [5] and of outer solar system planets [6]. For instance, Enceladus is expected to feature a combination of conditions favourable to clathrate production with the availability of large quantities of water, low temperature in the interior or at the surface, and a large pressure gradient from the surface to the interior of the planet. Therefore, a large amount of gas species (such as N2, CO, CO2, etc.) might be trapped in clathrate forms either during vapour re-deposition after gas plume ejections at the pole or within a high pressure-low-temperature environment such as that found within the ocean of the planet interior. Trapping of gases in clathrates might also explain the possible noble gas deficiencies detected in planetary environments [7]. In this work, in-situ micro-Raman spectroscopy, adapted to investigate gas hydrate [8], is used to study the formation of clathrates from thin films obtained by vapour deposition of nitrogen and water vapor at low pressure (10-2 - 103 mbar) and low temperature (77-200K). Sequential deposition consists in the condensation of (a) H2O and then (b) N2. An amorphous thick ice film (amorphous solid water) is first observed at 80K and characterized spectroscopically by Raman. Then nitrogen gas is injected into the sample chamber. During heating process (with 10 K increments), the amorphous film transforms into crystalline ice over a temperature range of 60 K. The nitrogen molecules are enclosed in the amorphous porous ice structure and become encaged into a N2-clathrate structure above 150K, revealed by the Raman signatures of guest partitioning in the water cages as evidenced in the nitrogen hydrate [9]. Co-deposition consists in the simultaneous deposition of nitrogen and water vapor at some specific gas-mixing ratio and temperature conditions of 80K. In this case, no clathrates could be observed and most N2 trapped initially into ASW is released during ice crystallization. [1] E.D. Sloan, Nature, 426, 353-363, (2003) [2] E.D. Sloan, C.A. Koh, 3rd ed.; Taylor & Francis-CRC Press: Boca Raton, FL, (2008) [3] H. Shoji, C.C. Jr. Langway, Nature 298, 548-550, (1982) [4] F. Hersant et al., Astrophys. J., 554, 391-407, (2001) [5] S. Lectez et al., Astrophys. J. Lett., 805: L1 (4pp), (2015) [6] A. Bouquet et al., Geophysical Res. Lett., 42, 1334-1339, (2015) [7] O. Mousis et al., Astrophys. J. Lett., 740, L9, (2011) [8] B. Chazallon et al., Gas Hydrates: Fundamentals, Characterization and Modeling: D. Broseta et al., Eds.; Wiley-ISTE: London, Vol. 1, pp 63-112, (2017) [9] C. Petuya et al., J. Phys. Chem. C. 2017, ASAP. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-16389.pdf
2019023004 Lenz, Josefine (Alfred Wegener Institute, Germany); Jones, Benjamin M.; Wetterich, Sebastian; Tjallingii, Rik; Fritz, Michael; Arp, Christopher D.; Rudaya, Natalia and Grosse, Guido. Small lake-large impact? Sedimentary records from Northern Alaska reveal lake expansion history and carbon dynamics [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-9163, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Thermokarst lakes are characteristic and dynamic landscape features of ice-rich permafrost environments. Our study of sedimentary records and shoreline expansion of Peatball Lake on the Alaska Arctic Coastal Plain reveals 1,400 years of thermokarst activity. While Peatball Lake likely initiated from a remnant pond of a drained lake basin, the catchment is likewise characterized by mid to late Holocene aged drained basins and remnants of Pleistocene and early Holocene aged uplands. As the lake expanded through lateral permafrost degradation, the sediment source has changed as indicated by internal-lake variability in sediment deposition. Reversed radiocarbon ages show recycling of "old" carbon and degraded organic matter became redeposited in the lake basin resulting in nutrient-poor sublittoral deposits. Our sedimentary records reflect the complexity of depositional environments in thermokarst lakes due to spatio-temporal changes in lake and catchment morphology as well as the impact of thermokarst lake activity on carbon storage of periglacial landscapes. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-9163.pdf
2019022662 MacDougall, Andrew (St. Francis Xavier University, Earth Sciences, Antigonish, NS, Canada). Estimating the effect of the permafrost carbon feedback on carbon budgets using a perturbed parameter ensemble approach [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-2827, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The permafrost carbon pool holds a mass of carbon over double that which was present in the pre-industrial atmosphere. As climate warms and permafrost thaws a fraction of this carbon is expected to be released to the atmosphere, increasing the atmospheric CO2 concentration and producing a positive feedback to climate change. The Paris Agreement to limit climate warming is framed in terms of temperature targets that should avoided, the 1.5° and 2.0°C targets. These targets can be translated into a cumulative total of fossil fuels that can be burned over all time compatible with the target--a 'carbon budget'. The theoretical underpinning of carbon budgets relies on a compensation mechanism of oceanic origin. The land carbon pools play no fundamental role in in the compensation mechanism. Thus the permafrost carbon feedback (and other land feedbacks) could have a non-linear effect on to final carbon budget. Here we use a perturbed parameter ensemble of an intermediate complexity climate model with temperature tracking to assess the likely effects of the permafrost carbon feedback on final carbon budgets. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-2827.pdf
2019020410 Mollenhauer, Gesine (Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI), Marine Geochemie, Bremerhaven, Germany); Winterfeld, Maria; Hefter, Jens; Grotheer, Hendrik and Pittauer, Daniela. No evidence for 20th century acceleration in mobilization of ancient carbon from thawing permafrost in the Lena River catchment [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-16406, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Release of carbon from thawing permafrost in high northern latitudes is a potential positive feedback in a warming climate, particularly since large quantities of carbon-rich organic matter have been stored in the permafrost soils for many millennia. Thawing of permafrost is expected to make this ancient organic matter bioavailable resulting in increased emissions of greenhouse gases. Thawing of permafrost may also result in increased transport of particulate organic matter through river systems to the ocean, where parts of this organic matter may escape remineralization and will be buried in marine sediments. This process might have accelerated over the past century in a warming Arctic with more frequent thaw slumping and increased river discharge. We therefore studied short sediment cores that were recovered off two of the main branches of the Lena River Delta, receiving the suspended matter transported from the mainly permafrost covered catchment of this great Russian Arctic river. The cores were recovered in 2013 from water depths of approximately 15 m and dated using 210Pbxs and 137Cs. The sediment records cover the past 70 to 120 years. We obtained compound-specific radiocarbon ages of aquatic (C16 n-alkanoic acids) and terrigenous (C28 n-alkanoic acids) biomarkers extracted from these cores. Besides, we analysed the geochemical composition of the sediment. Our results reveal that throughout the records' length, the age at deposition of the terrigenous biomarkers remained constant, while that of the aquatic biomarker decreased in the most recent decades. We will discuss these findings in context of the increases in Lena River discharge observed since the late 1980s. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-16406.pdf
2019022869 Mollenhauer, Gesine (Alfred-Wegener-Institut für Polar- und Meeresforschung (AWI), Marine Geochemie, Bremerhaven, Germany); Winterfeld, Maria; Meyer, Vera; Köhler, Peter; Dummann, Wolf; Grotheer, Hendrik; Lembke-Jene, Lester; Hefter, Jens; McIntyre, Cameron; Wacker, Lukas; Haghipour, Negar; Gersonde, Rainer and Tiedemann, Ralf. Mobilization of old terrestrial carbon caused by permafrost thawing, sea-level rise and ice-sheet melting during the last deglaciation [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14719, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The last deglaciation was characterized by rising concentrations in atmospheric CO2 (CO2atm) and a decrease in its radiocarbon content (D14Catm). Mobilization of 14C-depleted terrestrial organic carbon, which was previously frozen in extensive boreal permafrost soils, might have contributed to both changes. Since parts of this potentially mobilized organic carbon was reburied in marine sediments, records of accumulation of terrigenous biomarkers and their compound-specific radiocarbon ages can provide insights into the timing of, and controls on permafrost decomposition. We present data from marine sediment cores covering the last deglaciation that were retrieved from key locations potentially receiving terrigenous material mobilized from hotspot areas of permafrost thaw. In the North Pacific, we studied two cores off the Amur River draining into the Okhotsk Sea, and one core from the Northeastern Bering Sea adjacent to the Bering shelf (one of the largest shelf areas flooded during the deglaciation), which receives input from the Yukon River. During the Last Glacial Maximum these catchments were completely covered with permafrost. Today, the Amur drainage basin is free of permafrost while the Yukon catchment is covered by discontinuous permafrost. Besides, we investigated one core from the northwestern Black Sea as a record of terrigenous material released from the thawing European tundra. All sites show distinct deglacial maxima in accumulation of old terrigenous biomarkers (5-20 kyr old at the time of deposition). In the Black Sea, one early maximum of terrigenous organic matter accumulation occurred during HS1. In the North Pacific region, two more pronounced maxima occurred later during meltwater pulses suggesting that sea-level rise remobilized old terrestrial carbon from permafrost on the flooded shelves. Sea-level rise thus likely caused abrupt decomposition events across the Okhotsk and Bering shelves. We extrapolate our localized findings to an overall potential carbon release during deglaciation of 285 Pg C from coastal erosion in the Arctic Ocean and the related permafrost decomposition. By analysing some idealized scenarios using the global carbon cycle model BICYCLE we estimate the impact of carbon release from thawing permafrost on the atmosphere. We find that it might have accounted for a deglacial rise in CO2atm of up to 15 ppm, and to a decline in D14Catm of 15ppm. These results, if to abrupt changes restricted to the three peak events as supported by our data, might have contributed particularly to abrupt changes in CO2atm and D14Catm, corresponding to 15-20% of both, the observed rise in CO2atm of »90 ppm, and the residual in D14Catm that is unexplained by changes in the 14C production rate. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14719.pdf
2019022657 Oh, Youmi (Purdue University, Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN); Lau, Maggie C. Y.; Onstott, Tullis C.; Medvigy, David and Zhuang, Qianlai. Impacts of permafrost dynamics and nitrogen deposition on high affinity methanotrophy and net methane fluxes in the pan-Arctic terrestrial ecosystems [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-8722, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Arctic soils constitute an important methane (CH4) source to the atmosphere. Mechanistic CH4 models indicate that CH4 emissions from the Arctic may be doubled by 2100, as temperature increases and permafrost thaws. However, recent field studies have documented a surprisingly strong and consistent CH4 sink in Arctic mineral soils. This overlooked CH4 sink is likely due to the activity of novel CH4-oxidizing bacteria, or high-affinity methanotroph (HAM), that can survive and oxidize CH4 at atmospheric CH4 concentrations. Our early study further shows that nitrogen deposition and permafrost thaws affect the CH4 sink. However, the distinctive physiology of HAM has not been represented in existing regional methane simulations. Also, the mechanistic CH4 models consistently overestimate methane emissions relative to observation-based atmospheric inversions in the Arctic. We recently developed a site-level mechanistic CH4 model, eXplicit High Affinity Methanotroph model (XHAM) that includes HAM-specific physiology and microbial biomass change. The model was tested against soil core-thawing experiments and field-based measurements of methane fluxes and was compared to conventional mechanistic methane models. Our simulations show that high-affinity methanotrophy can be important in affecting net methane fluxes. Simulations without this process overestimate methane emissions. The model accurately simulated CH4 uptake for four arctic sites, but has not considered the effects of labile carbon, nitrogen deposition, and permafrost thaw. Thus, we incorporate XHAM model into a methane biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to quantify the role of this mineral CH4 sink in the regional methane budget. TEM couples carbon, nitrogen, water, and heat processes in terrestrial ecosystems to simulate CO2 and CH4 cycles. Using the XHAM-TEM, we tend to: 1) reconcile the discrepancy in the overall CH4 emission quantification by current mechanistic CH4 models and atmospheric inversions; 2) examine how the mineral CH4 sink will change due to soil temperature and moisture as well as CH4 production associated with thawing permafrost; and 3) quantify the reduction of the CH4 sink due to nitrogen deposition effects. Our preliminary results show that sparsely- vegetated mineral soils of tundra ecosystems explain 60% of the discrepancy of the methane budget estimates between mechanistic methane models and atmospheric inversions. We also find that the mineral CH4 sink strongly depends on atmospheric CH4 concentrations and soil moisture while nitrogen deposition has a moderate effect. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-8722-1.pdf
2019022661 Palmtag, Juri (Stockholm University, Department of Physical Geography, Stockholm, Sweden); Hugelius, Gustaf; Kuhry, Peter and Siewert, Matthias. Landscape partitioning and burial processes of soil organic matter in permafrost-affected soils [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-1206, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Soils in the northern high latitude regions are a key component in the global carbon cycle, with important feedbacks on climate (Hugelius et al., 2014). As the storage of soil organic matter in permafrost soils represents an enormous carbon sink in the past and a potentially relevant carbon source in a warmer future, knowledge about total stocks and factors controlling organic matter pools are of utmost importance for our understanding of climate change feedbacks (Davidson et al., 2006). A significant fraction of the soil organic matter in permafrost soils (permanently frozen ground) is buried by cryoturbation and preserved because of reduced decomposition rates under low temperatures (Bockheim, 2007). Since soil organic carbon (SOC) pools have large regional and landscape-level variability, with mean SOC 0-100 cm storage among our study sites ranging from 4.8 kg C m 2 to 30.0 kg C m 2 (Palmtag et al., 2015), detailed SOC inventories from across the northern permafrost region are needed to assess potential remobilization of SOC with permafrost degradation. This study provides: High-resolution land cover and landform classification data on total SOC storage from contrasting regions of continuous permafrost (Russia and Greenland) highlighting the need to consider numerous factors as topography, geomorphology, land cover, etc. in the assessment of landscape-level and regional SOC stock estimates. Insight into the effect of grain size distributions in permafrost soils on burial mechanisms through cryoturbation. References: Bockheim, J. G., 2007: Importance of cryoturbation in redistribution organic carbon in permafrost-affected soils. Soil Sci. Soc. Am. J., 71, 1335-1342. Davidson, E. A. et al., 2006: Temperature sensitivity of soil carbon decomposition and feedbacks to climate change. Nature, 440, 165-173. Hugelius, G. et al., 2014: Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps. Biogeosciences, 11, 6573-6593. Palmtag, J. et al., 2015: Storage, landscape distribution and burial history of soil organic matter in contrasting areas of continuous permafrost. AAAR, 47, 71-88. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-1206-2.pdf
2019022660 Petrov, Dmitry (Lomonosov Moscow State University, Department of Soil Science, Moscow, Russian Federation); Goncharova, Olga and Bobrik, Anna. Factors of spatial variability of soil properties in the south tundra of West Siberia (Russia) [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-547, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Soil efflux of carbon dioxide--an important parameter that can indicate the functioning of terrestrial ecosystems. For correct estimation of the process and to identify the factors affecting it, the study of soil CO2 emissions should be made with taking into account its spatial and temporal variability. Objective: Identification and quantification of the main factors of spatial heterogeneity of properties and parameters of functioning of soils, which are formed in different environmental conditions of continuous permafrost zone of Western Siberia. This area is characterized by severe climatic conditions: a long winter, the average annual air temperature of about -4,7°, precipitation varies from 200 to 350 mm per year. Investigations were carried out on the complex permafrost-affected soils and peat permafrost-affected soils. Ten-meter transects were established with step of 1 meter in both ecosystems. At each points of transects once a day within a week were measured: carbon dioxide efflux (closed chamber method), volumetric moisture and temperature at 10 cm depth. In the laboratory the pH, the total, labile and microbial carbons were measured for each point. Average CO2 efflux for all study period on cryogenic soil was 68±30 mg CO2/(m2 hr). The average daily temperature of the upper 10 cm layer was 8,0-8,5° on frost boil and 5,0-6,5° on permafrost-affected soil. Volumetric moisture was 42,3%. Many determined performance in the frost boil ecosystem was heavily dependent on the order in which the elements of the landscape studied. Identification and quantification of factors in the area, such as temperature, vegetation, carbon dioxide emission etc., varies greatly from a typical tundra ecosystem to frost boil. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-547.pdf
2019020341 Protsenko, Elizaveta (Norwegian Institute for Water Research (NIVA), Oslo, Norway); Kristiansen, Trond; Yakushev, Evgeniy; Wallhead, Philip; Varpe, Oystein; Yakubov, Shamil and Zagovenkova, Anastasia. Modeling the local effects of sub-sea permafrost degradation on Arctic marine biogeochemistry [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-19072, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Methane is a strong greenhouse gas and its emission from thawing permafrost could cause an accelerating effect on global warming and acidification in the ocean. To better understand the consequences for Arctic marine environments, we use a complex biogeochemical model to explore the local effects of methane seeps caused by permafrost thawing. Permafrost found in the outer part of Eastern Siberian Arctic Shelf (ESAS) has mostly degraded and represents an area where methane fluxes are very high. For that reason, we focus on simulating the biogeochemical changes in the water column resulting from methane seeps for the ESAS region. Bubbles from a single seep area tend to dissolve at about the same depth above the seafloor, resulting in the formation of methane-rich layers within the water column. At the same time, parts of ESAS are seasonally covered by ice, serving as an almost impermeable lid for methane fluxes and promoting the formation of methane-rich layers in the surface waters. To explore the state of the water column we use a 1D Ice-Pelagic-Benthic transport model (IPBM) coupled to the biogeochemical models Bottom RedOx Model (BROM) and the European Regional Seas Ecosystem Model (ERSEM). The chosen region is located within the Laptev Sea area. In the current stage, we use a data known from a literature to adjust ERSEM and therefore represent roughly a composition of a local ecosystem, while BROM provides estimations for the methane biogeochemistry. IPBM makes it possible to set a source of methane within a sediment column and track it through sediments, water, and ice domains. The results show some local impacts of the subsea methane source on marine biogeochemistry on seasonal timescales and the importance of accounting for the methane source from the permafrost. As subsea permafrost thawing is expected to continue over the coming decades, our modeling approach may also be useful for parameterizing long-term impacts on Arctic marine biogeochemistry. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-19072.pdf
2019020468 Riedo, Andreas (Leiden University, Leiden Observatory, Leiden, Netherlands); Wiesendanger, Reto; Tulej, Marek; Wurz, Peter and Ehrenfreund, Pascale. Chemical analysis of permafrost samples using a miniature LIMS system designed for in situ chemical analysis of solids on planetary surfaces [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-13086, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The detection of extinct or extant life on planetary surfaces is of high interest to planetary research. Mars is, due to its history, one of the most promising planetary objects to find traces of life, potentially in its sub-surface. However, due to the harsh environmental conditions at which instrumentation is typically operated on a planetary surface the detection thereof becomes extremely challenging. Therefore, simple and robust instrumentation with improved figures of merit and extended measurement capabilities are of high interest for future space exploration missions. In this contribution the measurement capabilities of our miniature laser ablation ionisation mass spectrometer (LIMS) system is demonstrated, on the basis of measurements conducted on Mars-relevant analogue material. The LIMS instrument is designed for quantitative and sensitive chemical (elements and isotopes) in situ analysis of the solids on planetary surfaces [1-3]. It consists of a miniature reflectron-type time-of-flight (RTOF) mass analyser (160 mm x O 60 mm) to which a femtosecond laser system (l = 775 nm, t » 190 fs, pulse energy ≤&eq; 1 mJ) is coupled for ablation and ionisation of sample material (laser ablation craters with diameter of about 10 - 20 mm) [1]. The Mars analogue materials used in this study are permafrost samples with a high abundance in biomass that were collected at different depths (»0.5 m, »1.5 m, »3.0 m) of an unique surface position in the Yedoma region, Russia. To develop an optimal measurement protocol, we conducted parametric studies on the samples, including the application of various laser irradiances and number of applied laser shots per single surface position. Furthermore, part of the sample material was heated up (3 h, > 100°C) i) to investigate the impact of heat on the chemical composition of such materials and ii) to cross-check if the LIMS system is sensitive enough to identify modifications in the chemical composition. One of the major findings in this campaign was, that the carbon content was highly reduced relative to the other detected species. Measurements conducted on both the raw and heat-treated sample material are discussed in detail and compared with each other. References: [1] A. Riedo, M. Neuland, S. Meyer, M. Tulej and P. Wurz, "Coupling of LMS with a fs-laser ablation ion source: elemental and isotope composition measurements", J. Anal. At. Spectrom., 28, 2013, 1256-1269. [2] M. Tulej, A. Neubeck, M. Ivarsson, A. Riedo, M.B. Neuland, S. Meyer and P. Wurz, "Chemical composition of micrometer-sized filaments in an aragonite host by a miniature laser ablation/ionization mass spectrometer", Astrobiol., 15, 2015, 669 - 682. [3] A. Neubeck, M. Tulej, M. Ivarsson, C. Broman, A. Riedo, S. McMahon, P. Wurz and S. Bengtsson, "Mineralogical determination in situ of a highly heterogeneous material using a miniaturized laser ablation mass spectrometer with high spatial resolution", Int. J. Astrobiol., 15, 2016, 133-146. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-13086.pdf
2019022658 Rinnan, Riikka (University of Copenhagen, Department of Biology, Copenhagen, Denmark); Kramshoj, Magnus; Albers, Christian; Holst, Thomas and Elberling, Bo. Reactive hydrocarbon emissions from thawing permafrost [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-2053, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Thawing permafrost has been identified as a potentially large source of greenhouse gases, CO2 and methane. However, some of the carbon from the vast deposits in permafrost may also be released as other climate-relevant gases such as volatile organic compounds (VOC). It is known that soils act both as sources and sinks of VOCs, and that these compounds can be biologically produced and slip out as side products of fermentation. Once in the atmosphere, VOCs participate in oxidation reactions with potential impacts on the lifetime of methane, and they also contribute to formation of secondary organic aerosol, with cooling impact on climate. We conducted a laboratory experiment using proton transfer reaction-time of flight-mass spectrometry (PTR-TOF-MS) to measure VOCs in real time while letting permafrost samples thaw. We also incubated permafrost samples together with active layer soils sharing the flask headspace but no direct contact to assess whether this would impact the amount or composition of the compounds released. We observed that thawing permafrost soils are a significant source of a large range of VOCs. However, the active layer soils showed a strong capacity for VOC uptake. With mineralization assays using 14C-labelled VOCs, we identified that the VOC uptake was largely due to microbial mineralization of the compounds to CO2. The environmental controls and the climatic relevance of the studied processes will be discussed. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-2053.pdf
2019022987 Schröder, Tanja (Technical University Munich, Munich, Germany) and Krautblatter, Michael. One decade of permafrost monitoring at the Zugspitze (Germany/Austria) [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-7540, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Mechanical and thermal properties of frozen rock slopes determine its stability and due to permafrost degradation, impose an increasing risk on people and infrastructure in high mountain regions. Electrical resistivity tomography (ERT) became the dominating major tool for temporal and spatial permafrost monitoring. Electric resistivity of frozen rock is highly temperature sensitive and can differentiate between frozen and unfrozen conditions (Krautblatter et al., 2010). Here we present results from one decade of ERT-based permafrost monitoring at the Zugspitze, assessing monthly spatial variations of permafrost distribution and quantitative information on rock temperature. We hypothesize a link between seasonal and long-term climate variance, permafrost temperature development and its spatial variability. Long term geophysical monitoring allows the validation of calculated rock temperatures from ERT-measurements. ERT-measurement are conducted along two transects in the main and side gallery of the Kammstollen adjacent to the Zugspitze north face. Derived rock/permafrost temperatures are based on laboratory calibration of electric resistivities to rock temperatures for Wetterstein limestone by Krautblatter et al. (2010). Two high-resistivity bodies along the investigation area reach resistivity values >&eq;104:5 Wm (@-0.5°C), indicating frozen rock, displaying a core section with resistivities >&eq;104:7 Wm (@-2°C) (Krautblatter et al., 2010). Seasonal variability is seen by laterally aggrading and degrading marginal sections (Krautblatter et al., 2010), showing an areal alternation between ~1,500 to >3,000 m2 in the core. External climate forcings affect rock temperatures with a signal propagation time of ~2-5 months. Short-term influences by cleft/pore water percolating through highly fractured zones via conductive heat transport cause the breakthrough of water passage into the core section from summer forward accounting for local warming of adjacent rock masses. Our preliminary results are: Rock/permafrost temperatures calculated from measured resistivities are in good accordance with locally measured and interpolated rock temperatures from the LfU borehole at the Zugspitze summit. Thus indicating a validation of permafrost/rock temperatures via geoelectric measurements. Calculated temperatures from ERT-data show a phase shift of ~2 (past Tair,max) to ~5 month (past Tair,0°C) compared to measured air temperatures. This time span equates the time needed by the climate signal to propagate through the rock wall via conductive energy transport resulting in recession and readvance of the zero-curtain in rock. The areal extend of the frozen rock mass shows a seasonal alternation between 35 to 60% of the entire investigation area in conformity with the variability of measured resistivities. Here we aim to assess the relationship between apparent resistivities, the ground thermal regime and meteorological forcings over an entire decade in steep rock wall permafrost. Based on time lapse ERT and meteorological data we present an approach to build a coupled thermo-geophysical model for conductive heat transfer in permafrost/frozen rock undergoing seasonal freeze-thaw cycles and long-term climatic change. Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. & Kemna, A. (2010): Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps). J. Geophys. Res. 115: F02003. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-7540-1.pdf
2019022664 Skeeter, Wesley (University of British Columbia, Vancouver, Canada); Christen, Andreas; Henry, Greg and Lantz, Trevor. Growing season carbon balance of a permafrost peatland in the Mackenzie River delta [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-11748, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Terrestrial Arctic landscapes are currently a net greenhouse gas sink, but climate warming and permafrost disturbances are anticipated to weaken or offset this sink in the future. The issue is further complicated in Arctic wetlands where methane (CH4) emissions disproportionately offset carbon dioxide (CO2) uptake. To study the sensitivity of CO2 and CH4 fluxes to various environmental controls (temperature, permafrost depth, water table), we continuously measured growing season trace gas exchange at a peatland site in the Mackenzie River delta, NWT, Canada (69.37234497°N, 134.8810577°W). Fluxes were measured using an eddy covariance on a floating platform at a height of 2.87 m from June 23 to September 13, 2017. The site is characterized by low center polygonal terrain and continuous permafrost, with Sphagnum sp., Equisetum sp., and Carex sp. in the polygons and Salix sp. present along the polygon rims. Active layer thickness increased from 20 cm to 51 cm over the season. Mean water table depth was 12 cm, ranging from 19 cm in mid-July to 6 cm in late-August. Neural network models were used identify factors most strongly influencing the fluxes and to gap fill the time series. Photon flux density and soil temperatures were found to be the strongest controls over CO2 fluxes. Manual chamber measurements of soil respiration suggest the polygon rims emit more CO2 per unit area than polygon centers. CH4 emissions were influenced by non-linear interactions between multiple factors including wind speed, photon flux density, active layer depth, and water table depth. The mean growing season CO2 flux was -1.76±0.31 g CO2 m-2 d-1, peaking in mid-July with minimal uptake after late August. Mean CH4 flux was 48.7±2.44 mg CH4 m-2 d-1, also peaking in July but displaying a more muted seasonal trend and high variability on short timescales. Accounting for the 100-year global warming potential of CH4, daily growing season fluxes are estimated to be -0.40±0.29 g CO2 eq. m-2 d-1. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-11748.pdf
2019023014 Slettebo, Isak (University of Bergen, Bergen, Norway); Christiansen, Casper and Lee, Hanna. Peak-summer CO2 balance in a thawing permafrost peat mire in northern Norway [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-19769, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Arctic and boreal soils store approximately twice the amount of carbon currently present in the atmosphere. These regions are currently warming twice as fast as the rest of the world, and models project that about 10% of their soil carbon is vulnerable for release to the atmosphere as CO2 or methane (CH4) as the permafrost thaws this century. Methane has a global warming potential 25 times that of CO2 over a 100-year time period, but due to overall greater efflux, CO2 is expected to dominate the climate forcing from permafrost carbon emissions. However, these projections are still relatively uncertain with more observations needed in order to determine the quantity and timing of greenhouse gas emissions from remote permafrost regions. In this study, we use the eddy covariance (EC) method to quantify peak-summertime (7 July to 6 August, 2017) CO2 and surface energy balance on a peat mire with actively thawing permafrost. Our study site is located in Finnmark, northernmost Norway (69 N), and the area consists of large palsas, which are peat plateaus containing intact permafrost within their thick organic mounds. As the permafrost thaws, the palsas degrade, and they eventually collapse into inundated wetlands. The steep hydrological gradient going from dry palsa mounds and into inundated thaw-ponds drastically alters the local carbon cycle. Therefore, in addition to using an EC tower measuring the CO2 balance on a catchment scale, we also quantify the small-scale greenhouse gas emissions using a series of well-replicated static chambers deployed along the hydrological permafrost thaw gradient. Together, the main goals of our study are i) to estimate the net peak-summertime CO2 balance at a degrading palsa mire ecosystem under permafrost thaw, ii) to evaluate the EC method by considering the surface energy balance, and iii) to compare the EC method and the chamber method for carbon flux measurements by upscaling chamber measurements to the whole catchment. Our study adds to similar but scarce research on the permafrost-carbon climate feedback. The palsa mires in Fennoscandia define the westernmost edge of the Eurasian permafrost zone, and ground temperatures here are generally higher than in other vast permafrost regions. This suggests that changes observed in Fennoscandia today might reveal what lies ahead for similar ecosystems in the much colder and larger areas in, for example, Russia. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-19769.pdf
2019023012 Steiner, Matthias (Technical University of Vienna, Research Group Geophysics, Department of Geodesy and Geoinformation, Vienna, Austria); Maierhofer, Theresa and Flores-Orozco, Adrian. Constraining Refraction Seismic Tomography (RST) by means of Ground-Penetrating Radar (GPR) models for an improved spatial characterization of alpine permafrost [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-17277, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
In frame of the ATMOperm project funded by the Austrian Academy of Sciences, we conducted a series of Refraction Seismic Tomography (RST) and Ground Penetrating Radar (GPR) surveys at the summit of Hoher Sonnblick (3106 m.a.s.l., Austria) with the objective to determine the internal structures and distribution of mountain permafrost. RST permits to solve for variations in the velocity of seismic waves, typically related to lithological interfaces; yet the contrasting P-wave velocities (Vp) for frozen and unfrozen materials allow to map permafrost rocks and to quantify the active-layer thickness in an imaging framework. However, the interpretation of the seismic results may be challenging as an increase in the Vp may be caused not only by frozen rocks, but also by lithological changes. In particular at the Hoher Sonnblick, changes in the seismic velocity with depth are associated with the contact between highly fractured rocks in the near surface and less compacted materials at depth. Hence, further information is required to improve the interpretation of the seismic results. Due to the significant differences in the electrical properties between frozen and unfrozen materials, and the possibility to collect data with contactless instruments with high spatial resolution and in short periods of time, GPR is a well-established method in permafrost investigations. Hence, we present here the application of GPR to enhance imaging results obtained from RST surveys in alpine permafrost. Besides the processing of GPR data, analysis through numerical models was conducted for a proper interpretation of the radargrams. In a second step, structural information obtained from the processed radargrams was used to refine the initial model for the tomographic inversion of the RST data. The impact of the complementary information was quantified by statistical analysis of the inversion results obtained using an ensemble of different initial models and different inversion algorithms (Hole, Rayfract, PyGimli). For a further investigation regarding the benefit of complementary GPR data we created numerical models with different layer depths and varying electromagnetic properties of the layers. Based on these models we computed synthetic radargrams and synthetic seismic data (travel times). The synthetic RST imaging results allowed for a better understanding of the influence of GPR measurement configurations (e.g. continuous and point-wise measurements) and the limitations of this joint processing approach. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-17277.pdf
2019022663 Sun Wenbin (Beijing Normal University, College of Global Change and Earth System Science, Beijing, China) and Ji Duoying. Simulated temporal and spatial variations of Tibet Plateau permafrost carbon during 1960-2009 [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-4312, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The Tibet Plateau has the largest permafrost regions in the middle and low latitudes and contains about 160±87 PgC soil organic carbon, which accounts for 10% of global permafrost soil organic carbon stocks, although its area accounts for 5% of global permafrost area, approximately. Under global warming, the microbial decomposition in thawing permafrost reduces the soil carbon stocks and releases the greenhouse gases, while the enhanced primary production of vegetation can increase soil carbon stocks. Here we use six land surface models from Permafrost Carbon Network Model Intercomparison Project (PCN-MIP) to analyze permafrost extent and related terrestrial carbon changes over the Tibet Plateau, including the active layer thickness (ALT), vegetation and soil carbon stocks, gross primary production (GPP) and soil respiration. The results show that Tibet Plateau permafrost has degraded during 1960-2009 with the declining rates ranging from 900 to 2400 km2 yr-1, although the simulated permafrost area at 1960 has a value of 8.47±4.92 million square kilometers showing large uncertainty. Moreover, annual maximum ALT of the permafrost has increased from 1.48±0.35 m in 1960 to 1.51±0.44 m in 2009, and the increasing trends range from 0.2 to 1.2 cm yr-1. Most models simulate increased soil and vegetation carbon stocks with warming during 1960-2009, soil and vegetation carbon stocks changed by -30.8-25.34 gCm2 yr-1 and -1.67-9.27 gCm2 yr-1 during the same period. Until 2009, average soil carbon stock was 4.49±2.56 gCm2 and average vegetation carbon stock was 0.12 0.18 gCm2 in the Tibet Plateau permafrost region. The increasing trends of GPP range from 0.24 to 2.20 gCm2 yr-2, and the soil respiration trends range from -0.13 to 0.58 gCm2 yr-1 between the models. The different sensitivities of GPP to increase in atmospheric CO2, and respiration to increase in warming are the dominant causes of large uncertainties of the simulated Tibet Plateau soil carbon stocks. This study indicates that more emphasis should be put on improving contemporary land surface models to better simulate climate and environmental change over the Tibet Plateau. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-4312-1.pdf
2019022993 Wani, John Mohd (Indian Institute of Technology (IIT) Roorkee, Department of Civil Engineering, Roorkee, India); Thayyen, Renoj J.; Ojha, Chandra Shekhar Prasad and Gruber, Stephan. Inferring permafrost occurrence from surface energy balance and miniature temperature data (MTD) loggers in Cold-Arid Himalaya [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-11929, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Cold-arid regions of the Himalaya is suspected to have significant permafrost cover. However, studies are in its infancy stage and characteristics, extent and governing energy regimes of Himalayan permafrost need to be established. Studies were initiated in a cryosphere experimental catchment of National Institute of Hydrology, Roorkee located in the upper Ganglass catchment, in Ladakh, India. The results of energy balance studies carried out from September 2015 to August 2016 are presented in this paper. The in-situ measurements of radiation components i.e. incoming and outgoing shortwave and longwave radiation and meteorological data such as air temperature, wind speed, and direction, relative humidity are used to estimate the surface energy balance (SEB) at a high elevation (4700 m a.s.l.) cold-arid site. The SEB estimate is undertaken by the bulk aerodynamic method. The study has been further strengthened by installing 26 GeoPrecision miniature temperature data (MTD) loggers (24 M-Log5W simple in soil/debris and 2 M-Log5W cable in bedrock) between 4700 and 5600 m a.s.l in the upper Ganglass catchment in August 2016. For the period (Sep-2015 to Aug-2016) at 4700 m a.s.l elevation, the net radiation component was dominant (76%) followed by sensible (14%) and latent heat fluxes (9%). The ground heat flux is limited to 1% of the total flux. The mean annual air temperature (MAAT) during the period was equal to -2.65 C. The total precipitation measured by non-recording rain gauge equals 99.4 mm w.e. during the study period and the precipitation dates were limited to 20 days in a year. A comparison of observed radiation and meteorological variables with other regions of the world show that the study site/region at Ladakh have a very low relative humidity (RH) in the range of 40% compared to 70% in the Alps. This results in the reduced amount of incoming longwave radiation and strongly negative net longwave radiation e.g., an average of approximately (-)90 Wm-2 compared to (-)40 Wm-2 in the Alps. Hence, the high elevation cold-arid region land surfaces are overall colder than the locations with more RH such as the Alps. Further, it is appreciated that the increase in direct incoming shortwave radiation leads to more radiation received by sun-exposed slopes than shaded ones in comparable areas and wet places such as meadows, etc. experience increased cooling as a result of stronger evaporation. The logger data shows very low mean annual ground surface temperature (MAGST) for the period September 2016 to August 2017 and varies between -10.0°C and +2.1°C. 21 loggers distributed across 15.7 km2 catchment recorded negative MAGST which suggest significant permafrost areas in the catchment. This study indicates that the permafrost is a significant cryospheric component in the region and highlight the need for further studies. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-11929.pdf
2019023009 Westergaard-Nielsen, Andreas (University of Copenhagen, Institute for Geosciences and Natural Resource Management, Department for Geography, Denmark); Karami, Mojtaba; Hansen, Birger; Westermann, Sebastian and Elberling, Bo. Evaluating permafrost vulnerability in Greenland using satellite temperature data [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-14841, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
The stability of permafrost in the Arctic is important for stable infrastructure in populated areas as well as for conserving the substantial quantities of stored carbon at northern latitudes. Important feedback mechanisms degrading the permafrost could be accelerated due to climate warming. It is therefore important to locate areas with vulnerable permafrost near communities, as well as mapping the extent of permafrost zones to assess the magnitude of potential degradation. Currently, we lack detailed mapping of permafrost in Greenland. Temperature datasets in Greenland are based on measurements biased towards low-lying coastal regions, or downscaled reanalysis data that is either dependent of these measurements or calibrated to the Greenlandic ice-sheet temperature regime. Here we show the applicability of 15 years of satellite-derived (MODIS) land surface temperatures as a fully independent dataset, with the potential to capture important local temperature trends and features such as inversion layers. We have corrected the satellite-based land surface temperature data for cloud cover contamination and present the validation of the temperatures across the ice-free part of Greenland. The corrected temperature data is used as the primary input to a steady-state permafrost model. We estimate that a limited extent of the permafrost in Green-land is highly vulnerable; however, the likely changes are observed where most people live today. We show the importance of high spatial resolution (1 km) data to guide local decision-making, and since Greenland represents significant climate gradients of north/south coast/inland/distance to large ice-sheets, the methods and conclusions are relevant in an upscaling to most Arctic areas. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-14841.pdf
2019022659 Wilkerson, Jordan (Harvard University, Department of Chemistry, Cambridge, MA). Significant permafrost nitrous oxide emissions observed on a regional scale [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-9898, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
As the planet warms, greenhouse gas emissions from thawing permafrost can potentially increase the net radiative forcing on our climate structure. However, knowledge about Arctic N2O emissions is sparse, and the fluxes are typically assumed to be negligible. Increasing evidence suggests emissions from permafrost thaw may be a significant source of N2O particularly through thermokarst features and cryoturbated peat circles. This evidence, though, is either based on lab experiments or in situ chamber studies, which have extremely limited spatial coverage. Consequently, it has not been confirmed to what extent these high emissions are representative of broader Arctic regions. Using an airborne eddy covariance flux technique, we measured N2O fluxes over the North Slope of Alaska in August 2013. From these measurements, we directly show that large areas of this Arctic region have significant N2O emissions. If our measurements represent other thermokarst/permafrost laden regions, N2O from permafrost composes 10% of the global, natural N2O budget. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-9898-1.pdf
2019022665 Yang, Ji-Woong (Seoul National University, School of Earth and Environmental Sciences, Seoul, South Korea); Ahn, Jinho; Kim, Kyungmin; Lee, Taekyu; Han, Sangyoung; Kim, Ji-Hoon; Go, Iwahana; Jang, Youngjoon; Ryu, Yeongjun; Kim, Yongwon; Fedorov, Alexander and Douglas, Thomas. Greenhouse gases (CO2, CH4, and N2O) entrapped in Alaskan and Siberian ice wedges; a direct evidence of the microbial activity within ground ice [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-11773, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
Ice wedge are one of the dominant components of massive ground ice in terrestrial permafrost. Due to repetitive thermal cracking and the downward infiltration of snowmelt and soil pore waters, ice wedge contains organic and inorganic compounds and microbes. Previous culture-based microbial sequencing assays discovered microorganisms the ice wedges, however, these studies did not address whether the microorganisms are active within ice matrix in subfreezing temperatures. Here we present preliminary results of greenhouse gas (GHG) measurements in gas enclosed in Pleistocene-aged ice wedges from central Siberia (Cyuie, Churapcha, and Syrdakh) and Alaska (Fox Permafrost Tunnel). Our results show the GHG mole fractions ranging from 0.5-18% CO2 70-13284 ppm CH4, 20-40451 ppb N2O in the Fox tunnel, Alaska. We measured 8.2-13.8% CO2, 1.3-22.5 ppm CH4, 1959 80988 ppb N2O in Churapcha, 7.4-13.2% CO2, 11.0-91.2 ppm CH4, 74 5539 ppb N2O in Cyuie, and 5.1-10.7% CO2, 3.3-9.1 ppm CH4, 405 13987 ppm N2O in the Syrdakh ice wedge. We found no clear evidence that the observed GHGs were produced by abiotic processes. Molar ratios of d(N2/Ar)of the enclosed air and bubble shapes the ice wedges studied in this study were created mainly by snow (and/or hoar) compaction without melting. Stable carbon isotope ratios of CO2 (d13C-CO2) from the four ice wedges indicate a biogenic origin of the CO2. Geologic CH4 production is unlikely due to low temperature condition. Inverse relationship between CH4 and N2O mixing ratios is observed in all sites, providing further evidence of microbial methanogenesis due to the inhibitory effect of N-oxides on methanogens. Further study is needed to determine whether microbial nitrification and denitrification existed in the past. Our results demonstrate that aerobic and anaerobic respiration occurred within the ground ice. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-11773-3.pdf
2019020293 Zhang-Turpeinen, Huizhong (University of Eastern Finland, Department of environmental and biological sciences, Kuopio, Finland); Kivimaenpaa, Minna; Prokushikin, Anatoly; Berninger, Frank; Koster, Kajar and Pumpanen, Jukka. Biogenic volatile organic compound emissions from forest floor along a fire chronosequence on permafrost in Central Siberia, Russia [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-13194, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
While the boreal terrestrial ecosystems and the underlying permafrost are experiencing pronounced climate warming, boreal forests may also face to more occurrences of wild fires and longer fire seasons. Fire event has long-term effects on ecosystems and biological processes of boreal forest. Thawing permafrost soils and increase in the active layer depth after a fire event could induce substantial BVOC emissions, because of the large amount of available decomposing litter and soil organic matter in boreal forest. Biogenic volatile organic compounds (BVOCs) indirectly affect climate by acting as precursors to tropospheric O3 and longer lifetime methane, and are associated with the formation of secondary organic aerosols, which further effect on cloud condensation nuclei formation. The aim of this study was to investigate the quality and quantity of BVOC emissions from arctic permafrost soil in boreal forest. We also aimed to assess how the combination of fire disturbance, vegetation communities shifting and environmental factors would affect the emissions. The study was executed in July of 2016 in Tura of Central Siberia, Russia. BVOCs were sampled from Siberian larch forest floor with a fire chronosequence that encompassed three age classes since the last fire occurred: (i) in 2 years ago, (ii) 23 years ago, and (iii) at least 100 (>100) year ago. A total of 83 BVOC compounds were detected, composing of isoprene, 40 monoterpenes, 27 sesquiterpenes and 15 other VOCs from all the samples. The emissions of BVOC in sum and in compound species varied in large ranges through ages and forest areas. There were significant differences in isoprene emissions between areas. There was no difference in monoterpene fluxes between the areas. A significant difference in sesquiterpene fluxes was observed between the > 100-year-old and 2-year-old areas. The emissions of other VOCs were significantly higher in the control areas than those in the other areas. The highest BVOC emissions from the forest floor were measured in the 23-year-old stand, while the forest floor was acted as a source of BVOC emissions in all forest age classes. The bare soil from the most recently burnt stand and the lichen from the control stand were identified as a sink of isoprene. The shrubs and decomposing litter material were contributing large amount of monoterpenes and sesquiterpenes, while the new vegetated ground plants in the 2-year-old forest areas were sinks of BVOCs. We confirm that vegetation on the forest floor was the most dominating source and controlling factor for BVOC emissions. We observed that the forest succession over time in post fire years was playing a significant affecting factor to BVOC sources. We suggest that wild fire and consequent permafrost thawing have both direct and indirect effects on the BVOC emissions within a century time perspective. The longer period field observation and systematic samplings in the central Siberian larch forest are highly recommended for better understanding the relations of fire disturbance, forest succession and BVOC exchanges with the global warming scheme. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-13194-1.pdf
2019022986 Zwieback, Simon (University of Guelph, Department of Geography, Guelph, Canada); Westermann, Sebastian; Langer, Moritz; Boike, Julia; Marsh, Philip and Berg, Aaron. Can satellite soil moisture retrievals improve permafrost monitoring? [abstr.]: in European Geosciences Union general assembly 2018, Geophysical Research Abstracts, 20, Abstract EGU2018-5519, 2018. Meeting: European Geosciences Union general assembly 2018, April 8-13, 2018, Vienna, Austria.
In permafrost regions, there is a strong coupling between a soil's moisture content and its thermal dynamics. However, dynamic changes in soil moisture have not been given much attention in permafrost monitoring, partially due to a previous shortage of observations. The questions hence arises: can novel remotely-sensed soil moisture estimates improve permafrost monitoring? Data assimilation seems a promising avenue, as it can improve the predicted temperatures and soil moisture by exploiting their complex, model-predicted coupling while accounting for uncertainties in both modelled and observed soil moisture. To explore its potential benefit, we conduct synthetic and real-world (Radarsat-2 soil moisture estimates over the Mackenzie River Delta Uplands, Canada) data assimilation experiments. We use an Ensemble Kalman Filter to ingest surface soil moisture into the state-of-the art CryoGrid-3 permafrost model, which has a flexible two-layer hydrology scheme. We address two questions. Where can surface soil moisture information improve modelled temperatures? We find that it mainly does so for porous, organic soils, but not for mineral soils. As organic soils dry, the cooling effect by the insulating soil wins out over the competing warming effect induced by decreasing evaporation. Surface soil moisture observations thus provide valuable information on deeper soil temperatures, a finding that is largely consistent with field observations. In mineral soils, by contrast, the thermal conductivity decreases much less upon drying, and surface soil moisture provides little information on deeper soil temperatures. How big are the improvements in organic soils? In our synthetic experiments, we find that estimates of the active layer thickness improve by up to a factor of two (down to 10 cm) upon assimilation, even when soil moisture observations are of limited precision. The modelled soil temperatures improve throughout the entire profile, with the largest improvements below 10 cm. We will compare those synthetic results with the Radarsat-2 observations. We conclude that satellite soil moisture information can help to reduce one major uncertainty in permafrost monitoring. We predict that advances in remote sensing and models will improve our knowledge of active layer and permafrost dynamics, not just of the water and energy balance, but also of ecological and biogeochemical processes. [Copyright Author(s) 2018. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2018/EGU2018-5519.pdf
2019016021 DelGreco, Jessica L. (University of New Hampshire Main Campus, Durham, NH); Herrick, Christina; Varner, Ruth K.; McArthur, Kellen J.; McCalley, Carmody K.; Garnello, Anthony; Finnell, Daniel; Anderson, Samantha M.; Crill, Patrick M. and Palace, Michael W. Four years of UAS imagery reveals vegetation change due to permafrost thaw [abstr.]: in AGU 2017 fall meeting, American Geophysical Union Fall Meeting, 2017, Abstract B43G-2218, December 2017. Meeting: American Geophysical Union 2017 fall meeting, Dec. 11-15, 2017, New Orleans, LA.
Warming trends in sub-arctic regions have resulted in thawing of permafrost which in turn induces change in vegetation across peatlands. Collapse of palsas (i.e. permafrost plateaus) has also been correlated to increases in methane (CH4) emissions to the atmosphere. Vegetation change provides new microenvironments that promote CH4 production and emission, specifically through plant interactions and structure. By quantifying the changes in vegetation at the landscape scale, we will be able to understand the impact of thaw on CH4 emissions in these complex and climate sensitive northern ecosystems. We combine field-based measurements of vegetation composition and high resolution Unmanned Aerial Systems (UAS) imagery to characterize vegetation change in a sub-arctic mire. At Stordalen Mire (1 km ´ 0.5 km), Abisko, Sweden, we flew a fixed-wing UAS in July of each year between 2014 and 2017. High precision GPS ground control points were used to georeference the imagery. Seventy-five randomized square-meter plots were measured for vegetation composition and individually classified into one of five cover types, each representing a different stage of permafrost degradation. With this training data, each year of imagery was classified by cover type. The developed cover type maps were also used to estimate CH4 emissions across the mire based on average flux CH4 rates from each cover type obtained from flux chamber measurements collected at the mire. This four year comparison of vegetation cover and methane emissions has indicated a rapid response to permafrost thaw and changes in emissions. Estimation of vegetation cover types is vital in our understanding of the evolution of northern peatlands and its future role in the global carbon cycle.
2019022442 Kellerer-Pirklbauer, Andreas (University of Graz, Department of Geography and Regional Science, Graz, Austria); Kaufmann, Viktor and Rieckh, Matthias. Mass balance of a highly active rock glacier during the period 1954 and 2016 [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11992, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Active rock glaciers are creep phenomena of permafrost in high-relief terrain moving slowly downwards and are often characterized by distinct flow structures with ridges and furrows. Active rock glaciers consist of ice and rock material. The ice component might be either congelation (refreezing of liquid water) or sedimentary ("glacier") ice whereas the rock material might be either of periglacial or glacial origin. The formation period of rock glaciers lasts for centuries to millennia as judged from relative or absolute dating approaches. The input of ice and debris onto the rock glacier mass transport system over such long periods might change substantially over time. Long-term monitoring of mass transport, mass changes and nourishment processes of rock glaciers are rare. In this study we analyzed on a decadal-scale mass transport (based on photogrammetric and geodetic data; series 1969-2016), mass changes (geodetically-based mass balance quantification; series 1954-2012), and mass input (based on optical data from an automatic digital camera; series 2006-2016) onto the Hinteres Langtal Rock Glacier. This rock glacier is 900 m long, up to 300 m wide, covers an area of 0.17 km2 and is one of the most active ones in the Eastern European Alps. Mass transport rates at the surface indicate relatively low mean annual surface velocities until the beginning of this millennium. A first peak in the horizontal surface velocity was reached in 2003/04 followed by a period of deceleration until 2007/08. Afterwards the rates increased again substantially from year to year with maximum values in 2014/15 (exceeding 6 m/a). This increase in surface velocities during the last decades was accompanied by crevasse formation and landslide activities at its front. Mass changes show for all six analysed periods between 1954 and 2012 a clear negative surface elevation change with mean annual values ranging from -0.016 to -0.058 m/a. This implies a total volume decrease of -435,895 m3 (averaging to -7515 m3/a) over the 58-year period at the rock glacier system. The only area of substantial surface elevation gain was during all periods the rock glacier front indicating a rock glacier advance. Mass input onto the rock glacier transport system was assessed analysing 2044 terrestrial images taken automatically between September 2006 and August 2016 from the main rooting zone of the rock glacier. Results indicate that neither snow and ice nor rock material have been transported in large quantities to the rock glacier system during the 10 year monitoring period. Notable mass movement events have been detected only six times. Perennial snow patches in the rooting zone of the rock glacier only survived on average every second summer. We conclude that the rates of rock glacier mass transport and volumetric losses of the rock glacier are far higher than debris and ice input. This rock glacier is clearly in a state of detachment from its nourishment area and prone to starvation which will eventually lead to rock glacier inactivation. This is a feasible fate for many currently active rock glaciers in the European Alps. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11992.pdf
2019022441 Luetscher, Marc (Austrian Academy of Sciences, Interdisciplinary Mountain Research, Austria); Moseley, Gina and Edwards, R. Lawrence. Dating the demise of permafrost in south-western Britain with cryogenic cave carbonates [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-11991, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Achieving a robust reconstruction of the evolution of permafrost in space and time is essential to characterize landscape dynamics in response to climate change. Because of erosion processes affecting surface sediments, access to potential archives of past permafrost is, however, limited. Cryogenic cave carbonates (CCCcoarse), which form by segregation of solutes during the freezing of cave water, provide a unique opportunity to investigate temporal changes in the regional permafrost distribution of southwestern Britain. CCCcoarse samples were found in Reservoir Hole and Wookey Hole, two extensive subhorizontal cave systems in the Mendip Hills (Somerset, UK). The samples comprise loose calcite spherolites, 1-5 mm in diameter, deposited on flowstones and/or breakdown blocks between 50 and 200 m below the ground surface. The cave passages are poorly ventilated and the modern temperatures averages ca. 11°C. Nine MC-ICPMS U-series analyses reveal ages clustering around 30.9±0.1, 29.4±0.1 and 14.7±0.1 ka, consistent with rapid climate changes associated with transitions into interstadials. We examine the significance of these ages with respect to the local hydrology and conclude that the area was exposed to widespread permafrost during the late Pleistocene, largely inhibiting groundwater recharge. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
URL: http://meetingorganizer.copernicus.org/EGU2017/EGU2017-11991.pdf
2019017171 Tarka, Robert (Uniwersytet Wroclawski, Instytut Nauk Geologicznych, Wroclaw, Poland) and Olichwer, Tomasz. Hydrogeochemiczna i regionalna charakterystyka wystepowania wod termalnych na Spitsbergenie [Hydrogeochemical and regional characteristics of thermal waters in Spitsbergen]: in XVIII sympozjum Wspolczesne problemy hydrogeologii (Stasko, Stanislaw, editor; et al.), Przeglad Geologiczny, 65(11/1), p. 1019-1024 (English sum.), illus. incl. 1 table, 19 ref., 2017. Meeting: XVIII sympozjum Wspolczesne problemy hydrogeologii, Nov. 8-10, 2017, Wojanow, Poland.
On Spitsbergen there are four areas of occurrence of thermal spring waters. The studies of these waters have a long history dating back to the nineteenth century. Outflows of thermal waters are associated with tectonic discontinuities, where sub-permafrost waters can flow to the surface area. The maximum temperatures of discharged thermal water exceed 25°C. The chemical composition of thermal waters from northern Spitsbergen derived from relict seawater, which is then modified by rain waters, waters of melting permafrost and contemporary sea waters. On the other hand, on the southern Spitsbergen thermal waters are characterized by a lower mineralization and there are contemporary waters involved in the deep circulation. Thermal waters with low mineralization are mainly multi-ions with dominate type bicarbonate-chloride-sodium-calcium. Thermo-mineral waters belong mainly to the types of chloride-sodium and chloride-bicarbonate-sodium.
URL: https://www.pgi.gov.pl/dokumenty-pig-pib-all/publikacje-2/przeglad-geologiczny/2 ...
|
The 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 
