2019042793 Cochand, Marion (Université Laval, Department of Geology & Geological Engineering and Centre for Northern Studies, Quebec City, QC, Canada); Molson, John and Lemieux, Jean-Michel. Groundwater hydrogeochemistry in permafrost regions: Permafrost and Periglacial Processes, 30(2), p. 90-103, illus. incl. 2 tables, 44 ref., June 2019.
This review paper provides a summary of the current state of knowledge regarding groundwater hydrogeochemistry in permafrost regions and presents expected impacts of permafrost degradation on groundwater quality. Using published case studies, the most practical monitoring approaches are reviewed, possible monitoring issues are highlighted, and links between groundwater chemistry signatures and associated flow systems in northern climates are identified. Hydrogeochemical characteristics of groundwater in permafrost regions depend on the same reactions as in nonpermafrost regions, but in acting as a confining layer, permafrost can affect groundwater chemistry by restricting recharge and limiting exchange of energy and mass between the ground surface, surface water and groundwater. Rock (mineral)-water interactions can also increase due to longer residence times. The impacts of climate change on groundwater quality in permafrost regions are thought to be linked to the loss of this confining layer. Various studies have reported significant modifications in shallow and deep groundwater contributions to surface water, marked by a decrease in dissolved organic carbon and an increase in total dissolved solids in stream water linked to declining permafrost coverage. Future studies related to hydrogeology in permafrost areas should include better in situ hydrogeochemical characterization of groundwater to assess its potential for future use as the climate warms. Abstract Copyright (2019), John Wiley & Sons, Ltd.
2019042795 Harrington, Jordan S. (University of Calgary, Department of Geoscience, Calgary, AB, Canada) and Hayashi, Masaki. Application of distributed temperature sensing for mountain permafrost mapping: Permafrost and Periglacial Processes, 30(2), p. 113-120, illus. incl. sketch map, 45 ref., June 2019.
Permafrost distribution in mountains is typically more heterogeneous relative to low-relief environments due to greater variability in the factors controlling the ground thermal regime, such as topography, snow depth, and sediment grain size (e.g., coarse blocks). Measuring and understanding the geothermal variability in high mountains remains challenging due to logistical constraints. This study presents one of the first applications of distributed temperature sensing (DTS) in periglacial environments to measure ground surface temperatures in a mountain permafrost area at much higher spatial resolution than possible with conventional methods using discrete temperature sensors. DTS measures temperature along a fibre-optic cable at high spatial resolution (i.e., ≤&eq;1 m). Its use can be limited by power supply and calibration requirements, although recent methodological developments have relaxed some of these restrictions. Spatially continuous DTS measurements at a studied rock glacier provided greater resolution of geothermal variability and facilitated the interpretation of bottom temperature of snowpack data to map patchy permafrost distribution. This research highlights the potential for DTS to be a useful tool for permafrost mapping, ground thermal regime interpretation, conceptual geothermal model development, and numerical model evaluation in areas of heterogeneous mountain permafrost. Abstract Copyright (2019), John Wiley & Sons, Ltd.
2019042792 Orgogozo, Laurent (Université de Toulouse, Géosciences Environnement Toulouse, Toulouse, France); Prokushkin, Anatoly S.; Pokrovsky, Oleg S.; Grenier, Christophe; Quintard, Michel; Viers, Jérôme and Audry, Stéphane. Water and energy transfer modeling in a permafrost-dominated, forested catchment of central Siberia; the key role of rooting depth: Permafrost and Periglacial Processes, 30(2), p. 75-89, illus. incl. 1 table, 34 ref., June 2019.
To quantify the impact of evapotranspiration phenomena on active layer dynamics in a permafrost-dominated forested watershed in Central Siberia, we performed a numerical cryohydrological study of water and energy transfer using a new open source cryohydrogeology simulator, with two innovative features: spatially distributed, mechanistic handling of evapotranspiration and inclusion of a numerical tool in a high- performance computing toolbox for numerical simulation of fluid dynamics, OpenFOAM. In this region, the heterogeneity of solar exposure leads to strong contrasts in vegetation cover, which constitutes the main source of variability in hydrological conditions at the landscape scale. The uncalibrated numerical results reproduce reasonably well the measured soil temperature profiles and the dynamics of infiltrated waters revealed by previous biogeochemical studies. The impacts of thermo-hydrological processes on water fluxes from the soils to the stream are discussed through a comparison between numerical results and field data. The impact of evapotranspiration on water fluxes is studied numerically, and highlights a strong sensitivity to variability in rooting depth and corresponding evapotranspiration at slopes of different aspect in the catchment. Abstract Copyright (2019), John Wiley & Sons, Ltd.
2019042796 Strand, Sarah M. (University Centre in Svalbard, Arctic Geology Department, Longyearbyen, Svalbard and Jan Mayen Islands) and Christiansen, Hanne H. Report from the International Permafrost Association; increasing regional activities on a global scale: Permafrost and Periglacial Processes, 30(2), p. 121-125, illus., 33 ref., June 2019.
2019042794 Weinstein, Yishai (Bar-Ilan University, Department of Geography and Environment, Ramat-Gan, Israel); Rotem, Dotan; Kooi, Henk; Yechieli, Yoseph; Sültenfuss, Jurgen; Kiro, Yael; Harlavan, Yehudit; Feldman, Mor and Christiansen, Hanne H. Radium isotope fingerprinting of permafrost; applications to thawing and intra-permafrost processes: Permafrost and Periglacial Processes, 30(2), p. 104-112, illus. incl. sketch map, 30 ref., June 2019.
Permafrost in circum-polar regions has been recently undergoing thawing, with severe environmental consequences, including the release of greenhouse gases and amplification of global warming. Although highly important, direct methods of tracking thawing hardly exist. In a research study conducted at Adventdalen, Svalbard, we identified a permafrost radioisotope fingerprint, and show that it can be used to track thawing. Ratios of long- to the shorter-lived radium isotopes are higher in ground ice than in active layer water, which we attribute to the permafrost closed system and possibly to the long residence time of ground ice in the permafrost. Also, daughter-parent 224Ra/228Ra ratios are lower in permafrost than in the active layer. These fingerprints were also identified in a local stream, confirming the applicability of this tool to tracing thawed permafrost in periglacial watersheds. A combination of radium isotope ratios and 3H allowed the identification of recent intra-permafrost segregation processes. The permafrost radium fingerprint should be applicable to other permafrost areas, which could assist in regional quantification of the extent of permafrost thawing and carbon emissions to the atmosphere. Abstract Copyright (2019), John Wiley & Sons, Ltd.
2019042789 Xu Fei (Harbin Institute of Technology, School of Energy Science and Engineering, Harbin, China); Song Wenyu; Zhang Yaning; Li Bingxi; Hu Yiran; Kim Yongsong and Fu Zhongbin. Water content variations during unsaturated feet-scale soil freezing and thawing: Cold Regions Science and Technology, 162, p. 96-103, illus., 42 ref., June 2019. Based on Publisher-supplied data.
In this study, we experimentally investigated the variations in water content during feet-scale soil freezing and thawing processes, and two particular water content variations were observed in the freezing and thawing processes. In the freezing process, experimental results revealed that the water content increased initially with an abrupt drop at temperatures close to the bulk water freezing point (T0=0°C). In the thawing process, two water content drops were observed at the initial and final stages of soil melting. In our opinion, the unusual increases and decreases in water contents are the results of state change between freezing and evaporation of pore water in top soil. Water content variations were calculated based on the initial water potential distribution by using two fitting functions, they agreed well with the unusual increases and decreases in the water contents, indicating that the unusual increases and decreases in the water content somehow related to the evaporation of pore water in top soil.
2019042698 Lu Jianguo (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Zhang Mingyi and Pei Wansheng. Hydro-thermal behaviors of the ground under different surfaces in the Qinghai-Tibet Plateau: Cold Regions Science and Technology, 161, p. 99-106, illus. incl. 2 tables, 30 ref., May 2019. Based on Publisher-supplied data.
The hydro-thermal properties of the ground affect the thermal regimes and surface energy balances. A field experiment in the Qinghai-Tibet Plateau was carried out to analyze the hydro-thermal boundaries, and the variations of the ground temperatures, volumetric unfrozen water contents and matric suctions for different surfaces (i.e., asphalt surface, concrete surface and natural gravel surface). The results show that the asphalt surface significantly changes the permafrost table and ground temperature. The mean annual temperature under the asphalt surface is 2.40°C higher than that under the concrete surface, and 2.77°C higher than that under the natural gravel surface. Therefore, the permafrost table under the asphalt surface is deeper than that under the natural gravel and concrete surfaces. In addition, the freezing and thawing processes of the ground under different surfaces are significantly different. Moreover, the volumetric unfrozen water content changes quickly near the ice-water phase transition zone, while the matric suction seldom changes until the volumetric unfrozen water reaches a certain value during the cold seasons, and the volumetric unfrozen water content dramatically changes due to the rainfall during the warm seasons. Furthermore, the volumetric unfrozen water content first decreases, and then increases with depth in the cross sections of the embankments during the cold seasons. The minimum volumetric unfrozen water content lies at the depth of 0.40 m for the natural gravel surface, and 0.90 m for the asphalt and concrete surfaces.
2019042695 Mao Yuncheng (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Li Guoyu; Ma Wei; Mu Yanhu; Wang Fei; Miao Jian and Wu Danze. Field observation of permafrost degradation under Mo'he Airport, northeastern China from 2007 to 2016: Cold Regions Science and Technology, 161, p. 43-50, illus. incl. 2 tables, sketch map, 35 ref., May 2019. Based on Publisher-supplied data.
The permafrost in the Da Xing'anling Mountains Northeastern China has experienced rapid and significant degradation due to climate warming and human activities during the last few decades. In this study, the permafrost degradation and freezing/thawing characteristics of the active layer at Mo'he airport were investigated through a ground temperatures data set collected over 10 years of measurements. During the monitoring period, thawing permafrost under the airport was observed, induced by climate warming, and thermal disturbance of airport construction and operation. The permafrost table under the blast pad declined considerably and varied from -9 m to -14 m, and from -4.5 m to -12 m under the natural site. The maximum depth of frost penetration at this airport shows a decreasing trend. The freezing duration of soil under the blast pad is shorter comparing with the natural ground surface, while its thawing duration is longer. The warming rates of permafrost at -10 m depth under the blast pad were 0.25-0.33°C/a, and those under the natural ground were 0.03°C/a and 0.15°C/a. The results provide valuable data for designing, construction and operation of the airport, and a reference for other airports construction in permafrost regions.
2019044529 Metrak, Monika (University of Warsaw, Biological and Chemical Research Center, Warsaw, Poland); Szwarczewski, Piotr; Binka, Krzysztof; Rojan, Elzbieta; Karasinski, Jakub; Gorecki, Grzegorz and Suska-Malawska, Malgorzata. Late Holocene development of Lake Rangkul (eastern Pamir, Tajikistan) and its response to regional climatic changes: Palaeogeography, Palaeoclimatology, Palaeoecology, 521, p. 99-113, illus. incl. 3 tables, sketch maps, 62 ref., May 1, 2019.
This study was aimed at collecting and examining a sediment core from Lake Rangkul (Eastern Pamir, Tajikistan) to better understand the lake's development and to assess past variations in climatic conditions in this particular area in comparison with data available from other lakes from the neighboring locations. For the purposes of this study, we performed detailed geochemical and palynological analyses on the sediment core taken from Lake Rangkul in 2014. Moreover, we obtained historical satellite and meteorological data and performed field tests for ground ice presence to identify trends in recent lake development. We distinguished 5 distinct stages over the past 2000 years of the lake's history that differ in geochemical and palynological characteristics. Despite the fact that Lake Rangkul is shallow and sensitive to various disturbances in sedimentation, the recorded stages are in accordance with general climatic trends observed for the Northern Hemisphere in the Late Holocene. Satellite data from the past 45 years shows a noticeable increase in the lake's area, which coincides with rising air temperatures. As the lake is located in the permafrost region with ground ice present immediately below the soil surface, its functioning is influenced by permafrost thawing, which will lead to future changes in the lake area and the distribution of surrounding wet meadows, used as pastures by local inhabitants.
2019036048 Bertran, Pascal (Institut National de Recherches Archeologiques Preventives, Bègles, France); Font, Marianne; Giret, Arnaud; Manchuel, Kevin and Sicilia, Deborah. Experimental soft-sediment deformation caused by fluidization and intrusive ice melt in sand: Sedimentology, 66(3), p. 1102-1117, illus., 70 ref., April 2019.
Identifying the driving mechanisms of soft-sediment deformation in the geological record is the subject of debate. Thawing of ice-rich clayey silt above permafrost was proved experimentally to be among the processes capable of triggering deformation. However, previous work has failed so far to reproduce similar structures in sand. This study investigates fluidization and intrusive ice formation from soil models in the laboratory. Experimental conditions reproduce the growth of ice-cored mounds caused by pore water pressure increase during freeze-back of sand in a permafrost context. Excess pore water pressure causes hydraulic fracturing and the development of water lenses beneath the freezing front. Later freezing of the water lenses generates intrusive ice. The main structures consist of sand dykes and sills formed when the increase in pore water pressure exceeds a critical threshold, and soft-sediment deformations induced by subsidence during ice melt. The combination of processes has resulted in diapir-like structures. The experimental structures are similar to those described in Pleistocene sites from France. These processes constitute a credible alternative to the seismic hypothesis evoked to explain soft-sediment deformation structures in other European regions subjected to Pleistocene cold climates. Abstract Copyright (2018), International Association of Sedimentologists.
2019044203 Stan, D. (University of Silesia, Faculty of Earth Sciences, Sosnowiec, Poland) and Stan-Kleczek, I. Geophysical approach to the study of a periglacial blockfield in a mountain area (Ztracene kameny, eastern Sudetes, Czech Republic); reply: Geomorphology, 328, p. 238-240, 42 ref., March 1, 2019. For reference to discussion see Uxa, T., et. al., Geomorphology, Vol. 328, p. 10-13, 2019; for reference to original see Stan, D., Stan-Kleczek, I., and Kania, I., Geomorphology, Vol. 293, p. 380-390, 2017.
2019044202 Uxa, Tomas (Charles University, Department of Physical Geography and Geoecology, Prague, Czech Republic); Krizek, Marek; Krause, David; Hartvich, Filip; Taborik, Petr and Kasprzak, Marek. Geophysical approach to the study of a periglacial blockfield in a mountain area (Ztracene kameny, Eastern Sudetes, Czech Republic); discussion: Geomorphology, 328, p. 231-237, illus. incl. 1 table, geol. sketch maps, 34 ref., March 1, 2019. For reference to original see Stan, D., Stan-Kleczek, I., and Kania, I., Geomorphology, Vol. 293, p. 380-390, 2017.
Stan et al. (2017) investigated the internal structure of two periglacial blockfields on the Ztracene kameny site, Eastern High Sudetes, Czech Republic, using electrical resistivity tomography and seismic refraction tomography and interpreted two high-resistivity and high-velocity zones as remnants of the Pleistocene permafrost. However, we believe that in reality no permafrost occurs on the site, and we provide alternate, non-permafrost interpretations of the geophysical measurements by Stan et al. (2017) that are well consistent with other evidences such as climate and topographic attributes of the blockfields, permafrost-disqualifying ground thermal regimes, and common characteristics of mid-latitude, low-altitude permafrost locations from elsewhere. We also rectify some misconceptions about the study site that are stated by Stan et al. (2017).
2019044331 Broder, Lisa (Stockholm University, Department of Environmental Science and Analytical Chemistry, Stockholm, Sweden); Andersson, August; Tesi, Tommaso; Semiletov, Igor and Gustafsson, Orjan. Quantifying degradative loss of terrigenous organic carbon in surface sediments across the Laptev and East Siberian Sea: Global Biogeochemical Cycles, 33(1), p. 85-99, illus. incl. sketch map, 80 ref., January 2019.
Ongoing permafrost thaw in the Arctic may remobilize large amounts of old organic matter. Upon transport to the Siberian shelf seas, this material may be degraded and released to the atmosphere, exported off-shelf, or buried in the sediments. While our understanding of the fate of permafrost-derived organic matter in shelf waters is improving, poor constraints remain regarding degradation in sediments. Here we use an extensive data set of organic carbon concentrations and isotopes (n = 109) to inventory terrigenous organic carbon (terrOC) in surficial sediments of the Laptev and East Siberian Seas (LS + ESS). Of these ~2.7 Tg terrOC about 55% appear resistant to degradation on a millennial timescale. A first-order degradation rate constant of 1.5 kyr-1 is derived by combining a previously established relationship between water depth and cross-shelf sediment-terrOC transport time with mineral-associated terrOC loadings. This yields a terrOC degradation flux of ~1.7 Gg/year from surficial sediments during cross-shelf transport, which is orders of magnitude lower than earlier estimates for degradation fluxes of dissolved and particulate terrOC in the water column of the LS + ESS. The difference is mainly due to the low degradation rate constant of sedimentary terrOC, likely caused by a combination of factors: (i) the lower availability of oxygen in the sediments compared to fully oxygenated waters, (ii) the stabilizing role of terrOC-mineral associations, and (iii) the higher proportion of material that is intrinsically recalcitrant due to its chemical/molecular structure in sediments. Sequestration of permafrost-released terrOC in shelf sediments may thereby attenuate the otherwise expected permafrost carbon-climate feedback. Abstract Copyright (2019), . The Authors.
2019044329 Lynch, Laurel M. (Cornell University, College of Agriculture and Life Sciences, Ithaca, NY); Machmuller, Megan B.; Boot, Claudia M.; Covino, Timothy P.; Rithner, Christopher D.; Cotrufo, M. Francesca; Hoyt, David W. and Wallenstein, Matthew D. Dissolved organic matter chemistry and transport along an Arctic tundra hillslope: Global Biogeochemical Cycles, 33(1), p. 47-62, illus. incl. 1 table, sketch map, 115 ref., January 2019.
Permafrost thaw is projected to restructure the connectivity of surface and subsurface flow paths, influencing export dynamics of dissolved organic matter (DOM) through Arctic watersheds. Resulting shifts in flow path exchange between both soil horizons (organic-mineral) and landscape positions (hillslope-riparian) could alter DOM mobility and molecular-level patterns in chemical composition. Using conservative tracers, we found relatively rapid lateral flows occurred across a headwater Arctic tundra hillslope, as well as along the mineral-permafrost interface. While pore waters collected from the organic horizon were associated with plant-derived molecules, those collected from permafrost-influenced mineral horizons had a microbial origin, as determined by fluorescence spectroscopy. Using high-resolution nuclear magnetic resonance spectroscopy, we found that riparian DOM had greater structural diversity than hillslope DOM, suggesting riparian soils could supply a diverse array of compounds to surface waters if terrestrial-aquatic connectivity increases with warming. In combination, these results suggest that integrating DOM mobilization with its chemical and spatial heterogeneity can help predict how permafrost loss will structure ecosystem metabolism and carbon-climate feedbacks in Arctic catchments with similar topographic features. Abstract Copyright (2019), . American Geophysical Union. All Rights Reserved.
2019044326 Martens, Jannik (Stockholm University, Department of Environmental Science and Analytical Chemistry, Stockholm, Sweden); Wild, Birgit; Pearce, Christof; Tesi, Tommaso; Andersson, August; Bröder, Lisa; O'Regan, Matt; Jakobsson, Martin; Skold, Martin; Gemery, Laura; Cronin, Thomas M.; Semiletov, Igor; Dudarev, Oleg V. and Gustafsson, Orjan. Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation: Global Biogeochemical Cycles, 33(1), p. 2-14, illus. incl. sketch map, 74 ref., January 2019.
Climate warming is expected to destabilize permafrost carbon (PF-C) by thaw-erosion and deepening of the seasonally thawed active layer and thereby promote PF-C mineralization to CO2 and CH4. A similar PF-C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (D14C, d13C, and lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS-L2-4-PC1). The sediment core reconstructs remobilization of permafrost carbon during the late Allerod warm period starting at 13,000 cal years before present (BP), the Younger Dryas, and the early Holocene warming until 11,000 cal years BP and compares this period with the late Holocene, from 3,650 years BP until present. Dual-carbon-isotope-based source apportionment demonstrates that Ice Complex Deposit-ice- and carbon-rich permafrost from the late Pleistocene (also referred to as Yedoma)-was the dominant source of organic carbon (66 ± 8%; mean ± standard deviation) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 ± 4.6 g·m-2·year-1) as in the late Holocene (3.1 ± 1.0 g·m-2·year-1). These results are consistent with late deglacial PF-C remobilization observed in a Laptev Sea record, yet in contrast with PF-C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF-C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of Ice Complex Deposit in response to future warming and sea level changes. Abstract Copyright (2018), . The Authors.
2019037738 Wang Xiqiang (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Chen Rensheng; Liu Guohua; Han Chuntan; Yang Yong; Song Yaoxuan; Liu Junfeng; Liu Zhangwen; Liu Xiaojiao; Guo Shuhai; Wang Lei and Zheng Qin. Response of low flows under climate warming in high-altitude permafrost regions in western China: Hydrological Processes, 33(1), p. 66-75, illus. incl. 3 tables, geol. sketch map, 53 ref., January 1, 2019.
The increase in low flows (winter discharge and minimum monthly discharge), caused primarily by permafrost degradation, is common in high-latitude permafrost regions, whereas the dynamics of low flows in high-altitude permafrost regions remain largely unknown. Long-term discharge data from 28 unregulated catchments in western China were analysed, and the findings showed that winter discharge/minimum monthly discharge significantly increased (p ≤&eq; 0.1) in 82/82%, 55/64%, and 0/0% of the catchments in the higher-latitude mountain permafrost regions (Tienshan Mountains), mid-latitude mountain permafrost regions (Qilian Mountains), and mid- to low-latitude plateau permafrost regions (the source regions of the Yangtze and Yellow rivers), respectively. The differences in permafrost type and the distribution of permafrost and alpine cold desert (which is similar to tundra) were found to be the main causes for the different responses in the low flows. The rate of change of low flows (winter discharge and minimum monthly discharge) was negatively and linearly correlated with permafrost coverage when coverage was less than 40% of the catchment area, whereas the low flows changed only slightly when the permafrost coverage exceeded 40%. A significant thickening of the active layer increased the low flows in the lower permafrost-covered catchments, which are dominated by warm permafrost. However, in the higher permafrost-covered catchments with cold permafrost and a cold climate, only an increase in permafrost temperature (without a notable thickening of the active layer) occurred, resulting in non-significant changes in low flows. Abstract Copyright (2019), John Wiley & Sons, Ltd.
2019040582 Budantseva, Nadin A. (Moskovskiy Gosudarstvennyy Universitet imeni M. V. Lomonosova, Moscow, Russian Federation). Rekonstruktsiya zimney temperatury vozdukha v golotsene po stabil'nym izotopam iz ledyanykh zhil v rayone goroda Anadyr' [Reconstruction of winter air temperature in the Anadyr area during the Holocene based on stable isotopes in ground ice veins]: Led i Sneg = Ice and Snow, 59(1), p. 93-102 (English sum.), illus. incl. 3 tables, 26 ref., 2019.
The object of research is syncryogenic Holocene strata on the coast of the Onemen Bay, 2 km from the town of Anadyr. In July 2017, the outcrop of the first marine terrace uncovered by strong storms was examined. The stratigraphy of the outcrop was represented mainly by sandy loam (5-7 m thick) covered by peat (1-1.5 m) and underlain by sand. Numerous massive ice wedges were opened in the upper part of this outcrop. Along with that another outcropping of transect of a lake-marsh basin represented by a peat bog of 2-2.5 m thick underlain by sandy loam was also investigated. Ice wedges occur below the polygonal trenches. The present-day narrow ice wedges were found in the upper part of the peat bog. Two representative fragments of both the above outcrops were thoroughly examined. Radiocarbon dating had shown that accumulation of peat on surface of the first marine terrace started in early Holocene (about 8 ka BP). Accumulation of peatland within the lake-marsh basin was also dated to the beginning of the Holocene (about 9 ka BP). In the middle of the Holocene, it was most likely interrupted as a result of thermokarst processes and bogging of the surface. Formation of peatlands in Chukotka during the Holocene is known to be accompanied by active growth of the massive ice wedges inside them, so the age of the wedges studied by us was estimated as the beginning of the Holocene. The analysis of stable oxygen and hydrogen isotopes in the Holocene and the present-day ice wedges had allowed establishing mainly the atmospheric type of moisture feeding of the wedges (due to melted snow) and lack of noticeable isotope fractionation during the ice formation. It has been found that d18O and d2H values in the Holocene ice wedges were lower than in the present-day wedges and snow by an average 2-3 and 7-12 ppm, respectively. Paleotemperature reconstructions performed on the basis of isotope-oxygen data showed that the air temperature of the coldest winter month in the first half of the Holocene in the Onemen Bay area was lower than the present-day ones by an average 2-3°C, which is in a good agreement with the trend of rising winter temperatures throughout the Chukotka Peninsula, as well as in other areas of Eastern Siberia and Alaska.
2019040581 Neradovskiy, L. G. (Rossiyskaya Akademiya Nauk, Siberskoye Otdeleniya, Institut Merzlotovedeniya im. P. I. Mel'nikova, Yakutsk, Russian Federation). Otsenka ob'yemnoy l'distosti dispersnykh gruntov Tsentral'no-Yakutskoy nizmennosti po dannym georadiolokatsii [Assessment of ground ice volume in soils of the central Yakutia lowland based on ground-penetrating radar data]: Led i Sneg = Ice and Snow, 59(1), p. 81-92 (English sum.), illus. incl. 3 tables, 14 ref., 2019.
The previously unknown dependence between the volume ice content of frozen dispersed soils and their radiophysical properties (the speed of propagation and specific attenuation of the amplitude of electromagnetic waves) was studied in the layer of annual heat flows of Central Yakutia. The correlation between these characteristics determined in the laboratory and the method of discrete georadiolocation is established. The peculiarity of the connection is the sharp decline in the sensitivity of the propagation speed and the specific attenuation of electromagnetic waves in frozen dispersed soils with high volume ice content (more than 60%). In general, the specific attenuation of electromagnetic waves is more responsive to the change in the volume of ice content of frozen dispersed soils and, thus, it is more preferable to solve the problem of quantitative evaluation of this characteristic. The proposed method of reusable measurements of signals of georadiolocation with changing position and azimuth of antennas of georadars in the vicinity of the network points of geological and geophysical observations allows to estimate the average values of the propagation speed and specific attenuation of electromagnetic waves with an error of not more than 10%. Due to this, according to the equations of logistic functions it is possible to calculate the average values of volume ice content with an error of 7-11%. With this error, the picture of the probability distribution according to the georadiolocation values of the volume ice content in the averages is completely identical to the laboratory data. On this basis, the found regression equations are recommended to be used for the calculation of the speed of propagation and specific attenuation of electromagnetic waves of background or average values of the volume ice content of frozen dispersed soils of the annual heat transfer layer in any part of the ice complex of the Central Yakut lowland.
2019040580 Pozdniakov, S. P. (Moskovskiy Gosudarstvennyy Universitet imeni M. V. Lomonosova, Moscow, Russian Federation); Grinevskiy, S. O.; Dedyulina, Ye. A. and Koreko, Ye. S. Chuvstvitel'nost' rezul'tatov modelirovaniya sezonnogo promerzaniya k vyboru parametrizatsii teploprovodnosti snezhnogo pokrova [Sensitivity of seasonally frozen ground models to selected parameters of snow thermal conductivity]: Led i Sneg = Ice and Snow, 59(1), p. 67-80 (English sum.), illus., 18 ref., 2019.
The relationship between the results of calculations of the dynamics of the temperature regime of the in freezing and thawing soil profile with the heating effect of the snow cover is considered. To analyze this connection, two coupled models are used; the model of formation and degradation of snow cover in winter and the model of heat transfer and soil moisture transport in underlying vadoze zone profile. Parametrization of the influence of the snow cover, which at each calculated moment of time has the current average density and depth, on the dynamics of the temperatures of the soil profile is due to the use of its specific thermal resistance, which depends on its current depth and the thermal conductivity coefficient. The coefficient of thermal conductivity of the snow cover is related with its density using six different published empirical relationships. Modeling of heat transfer in freezing and thawing soil is carried out on the example of the field site for monitoring the thermal regime located on the territory of the Zvenigorod Biological Station of Moscow State University. It is shown that the well-known relationships give similar curves for the dynamics of the depth of seasonal freezing, including the degradation of the seasonal freezing layer in the spring period, with the same dynamics of the snow cover. However, the maximum penetration depth of the zero isothermal differs significantly for different snow conductivity-snow density relationships. The tested six relationships were divided into three groups. Minimal freezing is provided by the Sturm model and the effective medium model. The average and rather poorly differentiating freezing from each other is given by the Pavlov, Osokin et al. and Jordan relationships. The greatest value of the freezing depth is obtained with using Pavlov's relationship with a temperature correction.
2019035824 Hogstrom, Elin (Austrian Polar Research Institute, Vienna, Austria); Heim, Birgit; Bartsch, Annett; Bergstedt, Helena and Pointner, Georg. Evaluation of a MetOp ASCAT-derived surface soil moisture product in tundra environments: Journal of Geophysical Research: Earth Surface, 123(12), p. 3190-3205, illus. incl. 3 tables, sketch maps, 65 ref., December 2018.
Satellite-derived surface soil moisture data are available for the Arctic, but detailed validation is still lacking. Previous studies have shown low correlations between in situ and modeled data. It is hypothesized that soil temperature variations after soil thaw impact MetOp ASCAT satellite-derived surface soil moisture (SSM) measurements in wet tundra environments, as C band backscatter is sensitive to changes in dielectric properties. We compare in situ measurements of water content within the active layer at four sites across the Arctic in Alaska (Barrow, Sagwon, Toolik) and Siberia (Tiksi), taken in the spring after thawing and in autumn prior to freezing. In addition to the long-term measurement fields, where sensors are installed deeper in the ground, we designed a monitoring setup for measuring moisture very close to the surface in the Lena River Delta, Siberia. The volumetric water content (VWC) and soil temperature sensors were placed in the moss organic layer in order to account for the limited penetration depth of the radar signal. ASCAT SSM variations are generally very small, in line with the low variability of in situ VWC. Short-term changes after complete thawing of the upper organic layer, however, seem to be mostly influenced by soil temperature. Correlations between SSM and in situ VWC are generally very low, or even negative. Mean standard deviation matching results in a comparably high root-mean-square error (on average 11%) for predictions of VWC. Further investigations and measurement networks are needed to clarify factors causing temporal variation of C band backscatter in tundra regions. Abstract Copyright (2018). The Authors.
2019044316 Beel, Casey R. (Queen's University, Department of Geography and Planning, Kingston, ON, Canada); Lamoureux, Scott F. and Orwin, John F. Fluvial response to a period of hydrometeorological change and landscape disturbance in the Canadian high arctic: Geophysical Research Letters, 45(19), p. 10446-10455, illus. incl. sketch map, 49 ref., October 16, 2018.
Records of fluvial suspended sediment fluxes are sensitive indicators of hydrometeorological and permafrost change. Here we document the watershed-scale suspended sediment flux response to a period of hydrometeorological change and landscape disturbance in two High Arctic rivers. Net in-channel and extra-channel sediment storage and changing hydrometeorological conditions dampen the downstream transport of increased sediment delivery from localized permafrost slope disturbances. Our results show that the impact of permafrost disturbance is likely a smaller effect than a shift toward a pluvially (rainfall) dominated hydrological regime in these environments. Suspended sediment transport is energy limited under contemporary hydrometeorological conditions, and the transition from a nival to pluvial dominated flow and sediment transfer regime will likely accelerate landscape change in the High Arctic. Abstract Copyright (2018), American Geophysical Union. All Rights Reserved.
2019035883 Knutsson, Roger (Lulea University of Technology, Department of Civil Environmental and Natural Resources Engineering, Lulea, Sweden); Viklander, Peter; Knutsson, Sven and Laue, Jan. How to avoid permafrost while depositing tailings in cold climate: Cold Regions Science and Technology, 153, p. 86-96, illus. incl. 4 tables, sketch map, 50 ref., September 2018. Based on Publisher-supplied data.
Managing tailings deposition in cold climate requires specific measures not to create permafrost. The risk of generating permafrost due to tailings deposition exists even in regions where permafrost would naturally not occur. Material being frozen during winter might not fully thaw in the following summer due to added height of the tailings on the surface. Such embedded layers of permafrost should be avoided especially close to tailing dams. Main reasons are to prevent impermeable layers in tailings facilities, and to reduce the risk of having implications if such layers thaw during warmer summers causing increase in pore water pressure, reduced effective stress, and increased water content. This paper presents a numerical study on the effects of tailings deposition in cold regions in relation to the potential formation of permafrost. Various deposition rates, schedules and tailings properties were evaluated. One-dimensional heat conduction analyses were performed with a temperature scenario representing a mine district in northern Sweden. Results show, that the thickness of permafrost layers increase with increased deposition rate and with increased water content. It was also shown that wet and loose tailings must be deposited in short periods during summer to avoid permafrost generation. In the case of dry and dense tailings more time is available for deposition in order not to cause aggradation of permafrost in the deposit. These findings can help mining operation to set up deposition schedules for tailings facilities in cold climate. For known tailings properties, results can be used to identify periods of the year when, and how much, tailings can be deposited in critical areas of a deposit in order to avoid permafrost formation.
2019035882 Yu Xiaobo (Huazhong University of Science & Technology, School of Civil Engineering & Mechanics, Wuhan, China); Liu Huabei; Sun Rui and Yuan Xiaoming. Improved Hardin-Drnevich model for the dynamic modulus and damping ratio of frozen soil: Cold Regions Science and Technology, 153, p. 64-77, illus. incl. 5 tables, 19 ref., September 2018. Based on Publisher-supplied data.
The Hardin-Drnevich model is frequently employed in the seismic ground response analysis, but the original model cannot be directly applied to frozen soils, the dynamic properties of which are functions of the soil temperature. Resonant column tests were carried out and empirical correction factors were proposed to revise the model. The improved model was applied to the seismic ground response analysis of a permafrost site, and the influences of the variations of the correction factors were analyzed. The resonant column test results indicated that soil temperature had large influences on the shear modulus and damping ratio, while in the range investigated in this study, the effect of the degree of saturation was not significant. The proposed correction factors properly fitted the test results in the present and previous studies, but the correction factors varied considerably even for the same category of clayey or silty or sandy soils. Compared with the correction factors for the modulus reduction curve and damping curve, the correction factor for the maximum shear modulus had a larger effect on the seismic ground response of a permafrost site. In the seismic response analyses, the response spectral values at the ground surface were generally larger if the investigated site was assumed to be non-frozen.
2019035001 Ci Zhijia (Chinese Academy of Sciences, Research Center for Eco-Environmental Sciences, Beijing, China); Peng Fei; Xue Xian and Zhang Xiaoshan. Temperature sensitivity of gaseous elemental mercury in the active layer of the Qinghai-Tibet Plateau permafrost: Environmental Pollution (1987), 238, p. 508-515, illus. incl. sketch map, 64 ref., July 2018.
Soils represent the single largest mercury (Hg) reservoir in the global environment, indicating that a tiny change of Hg behavior in soil ecosystem could greatly affect the global Hg cycle. Climate warming is strongly altering the structure and functions of permafrost and then would influence the Hg cycle in permafrost soils. However, Hg biogeochemistry in climate-sensitive permafrost is poorly investigated. Here we report a data set of soil Hg (0) concentrations in four different depths of the active layer in the Qinghai-Tibet Plateau permafrost. We find that soil Hg (0) concentrations exhibited a strongly positive and exponential relationship with temperature and showed different temperature sensitivity under the frozen and unfrozen condition. We conservatively estimate that temperature increases following latest temperature scenarios of the IPCC could result in up to a 54.9% increase in Hg (0) concentrations in surface permafrost soils by 2100. Combining the simultaneous measurement of air-soil Hg (0) exchange, we find that enhanced Hg (0) concentrations in upper soils could favor Hg (0) emissions from surface soil. Our findings indicate that Hg (0) emission could be stimulated by permafrost thawing in a warmer world.
2019044021 Olson, Christine (Desert Research Institute, Reno, NV); Jiskra, M.; Biester, H.; Chow, J. and Obrist, Daniel. Mercury in active-layer tundra soils of Alaska; concentrations, pools, origins, and spatial distribution: Global Biogeochemical Cycles, 32(7), p. 1058-1073, illus. incl. 1 table, sketch map, 110 ref., July 2018.
Tundra soils serve as major sources of mercury (Hg) input to the Arctic Ocean via river runoff and coastal erosion; yet little information is available on tundra soil Hg concentrations, pool sizes, origins, and dynamics. We present a detailed investigation of Hg in the active layer (upper ~100 cm subject to seasonal thaw) of tundra soils across 11 sites in Alaska. Soil Hg concentrations in organic horizons (151 ± 7 mg/kg) were in the upper range of temperate soil organic horizons, and concentrations in mineral horizons (98 ± 6 mg/kg) were much higher than in temperate soils. Soil Hg concentrations declined from inland to coastal sites, in contrast to a hypothesized northward increase expected because of proximity to coastal atmospheric mercury depletion events. Principle component analyses and elemental ratios results show that exogenic sources dominated over geogenic sources-in A-horizons (66 ± 4%) and mineral B-horizons (51 ± 1%). 14C age-dating suggested recent origins of Hg in surface soils but showed that mineral soils (more than 7,300 years old) must have accumulated atmospheric inputs across millennia leading to high soil concentrations and pools. We estimated a total Northern Hemisphere active-layer tundra soil Hg pool of 184 Gg (range of 136 to 274 Gg), suggesting a globally important Hg storage pool. Tundra soils are subject to seasonal thaw and freeze dynamics, thereby providing large inputs to rivers, lakes, and the Arctic Ocean. Understanding processes that mobilize Hg from tundra soils will be critical to understanding future Arctic wildlife and human Hg exposures. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.
2019035470 Xie Zhenghui (Chinese Academy of Sciences, Institute of Atmospheric Physics, Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Beijing, China); Liu Shuang; Zeng Yujin; Gao Junqiang; Qin Peihua; Jia Binghao; Xie Jinbo; Liu Bin; Li Ruichao; Wang Yan and Wang Longhuan. A high-resolution land model with groundwater lateral flow, water use, and soil freeze-thaw front dynamics and its applications in an endorheic basin: Journal of Geophysical Research: Atmospheres, 123(14), p. 7204-7222, illus. incl. 3 tables, 63 ref., July 27, 2018.
Human water regulation, groundwater lateral flow, and the movement of frost and thaw fronts (FTFs) affect soil water and thermal processes, as well as energy and water exchanges between the land surface and atmosphere. Reasonable representation of these processes in land surface models is very important to improving the understanding of land-atmosphere interactions. In this study, mathematical descriptions of groundwater lateral flow, human water regulation, and FTFs were synchronously incorporated into a high-resolution community land model, which is then named the Land Surface Model for Chinese Academy of Sciences (CAS-LSM). With a series of atmospheric forcings and high-resolution land surface data from the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) program, numerical simulations of the period 1981-2013 using CAS-LSM with 1-km resolution were conducted for an endorheic basin, the Heihe River Basin in China. Compared with observations, CAS-LSM reproduced the distributions of groundwater, evapotranspiration, and permafrost reasonably and well matched the temporal changes in ground temperature, heat fluxes, and FTFs. Results illuminate the temporal and spatial characteristics of frozen soil and the changes in the land-atmosphere exchange of carbon, water, and energy. The permafrost and seasonally frozen soil were distinguished. In the seasonally frozen areas, the maximum soil frost depth increased by 0.65 mm/year within natural areas and decreased by 2.12 mm/year in human-dominated areas. The active layer thickness increased 8.63 mm/year for permafrost. In the permafrost zone evapotranspiration and latent heat flux increased, and the sensible heat flux declined. In the human-dominated areas water use raised the latent heat flux and reduced the sensible heat flux, net ecosystem exchange, and streamflow recharging to the eco-fragile region in the lower reaches. Results suggested that the land surface model CAS-LSM is a potential tool for studying land surface processes, especially in cold and arid regions experiencing human interventions. Abstract Copyright (2018). American Geophysical Union. All Rights Reserved.
2019038917 Bertran, Pascal (Institut National de Recherches Archeologiques Preventives (INRAP), Begles, France); Andrieux, Eric; Bateman, Mark; Font, Marianne; Manchuel, Kevin and Sicilia, Deborah. Features caused by ground ice growth and decay in late Pleistocene fluvial deposits, Paris Basin, France: Geomorphology, 310, p. 84-101, illus. incl. 1 table, geol. sketch maps, 96 ref., June 2018.
Last Glacial fluvial sequences in the Paris Basin show laminated lacustrine deposits OSL and radiocarbon dated to between 24.6 and 16.6 ka in one site and overlying alluvial sandy gravel. A thermokarst origin of the lakes is supported by abundant traces of ground ice, particularly ice wedge pseudomorphs beneath the lacustrine layers and synsedimentary deformation caused by thaw settlement. The features include brittle deformation (normal and reverse faults) resulting from ground subsidence owing to ice melting and ductile deformations caused by slumping of the sediments heaved by the growth of ice-cored mounds. These correspond to lithalsas (or lithalsa plateaus) and/or to open system pingos. At least two generations of thermokarst are recorded and may reflect the millennial climate variability typical of the Last Glacial. The structures studied in quarries are associated with an undulating topography visible in 5-m DEMs and a spotted pattern in aerial photographs. The search for similar patterns in the Paris Basin indicates that many other potential thermokarst sites exist in the Last Glacial terrace (Fy) of rivers located north of 48°N when they cross the lower Cretaceous sands and marls. In some sites, the presence of organic-poor, fine-grained deposits presumably of lacustrine origin was confirmed by borehole data. The site distribution coincides broadly with that already known for ice wedge pseudomorphs. This study provides new evidence of permafrost-induced ground deformations in France and strongly suggests that thermokarst played a significant and probably largely underestimated role in the genesis of Late Pleistocene landscapes.
2019038919 Imaizumi, Fumitoshi (Shizuoka University, Faculty of Agriculture, Shizuoka, Japan); Nishiguchi, Takaki; Matsuoka, Norikazu; Trappmann, Daniel and Stoffel, Markus. Interpretation of recent Alpine landscape system evolution using geomorphic mapping and L-band InSAR analyses: Geomorphology, 310, p. 125-137, illus. incl. 6 tables, sketch maps, 101 ref., June 2018.
Alpine landscapes are typically characterized by inherited features of past glaciations and, for the more recent past, by the interplay of a multitude of types of geomorphic processes, including permafrost creep, rockfalls, debris flows, and landslides. These different processes usually exhibit large spatial and temporal variations in activity and velocity. The understanding of these processes in a wide alpine area is often hindered by difficulties in their surveying. In this study, we attempt to disentangle recent changes in an alpine landscape system using geomorphic mapping and L-band DInSAR analyses (ALOS-PALSAR) in the Zermatt Valley, Swiss Alps. Geomorphic mapping points to a preferential distribution of rock glaciers on north-facing slopes, whereas talus slopes are concentrated on south-facing slopes. Field-based interpretation of ground deformation in rock glaciers and movements in talus slopes correlates well with the ratio of InSAR images showing potential ground deformation. Moraines formed during the Little Ice Age, rock glaciers, and talus slopes on north-facing slopes are more active than landforms on south-facing slopes, implying that the presence of permafrost facilitates the deformation of these geomorphic units. Such deformations of geomorphic units prevail also at the elevation of glacier termini. For rock cliffs, the ratio of images indicating retreat is affected by slope orientation and elevation. Linkages between sediment supply from rock cliffs and sediment transport in torrents are different among tributaries, affected by relative locations between sediment supply areas and the channel network. We conclude that the combined use of field surveys and L-band DInSAR analyses can substantially improve process understanding in steep, high-mountain terrain.
2019035294 Lu Wenjun (Hohai University, State Key Laboratory of Hydrology, Water Resources and Hydraulic Engineering, Nanjing, China); Wang Weiguang; Shao, Quanxi; Yu Zhongbo; Hao Zhenchun; Xing Wanqiu; Yong Bin and Li Jinxing. Hydrological projections of future climate change over the source region of Yellow River and Yangtze River in the Tibetan Plateau; a comprehensive assessment by coupling RegCM4 and VIC model: Hydrological Processes, 32(13), p. 2096-2117, illus. incl. 4 tables, sketch map, 113 ref., June 30, 2018.
Understanding climate change impacts on hydrological regime and assessing future water supplies are essential to effective water resources management and planning, which is particularly true for the Tibetan Plateau (TP), one of the most vulnerable areas to climate change. In this study, future climate change in the TP was projected for 2041-2060 by a high-resolution regional climate model, RegCM4, under 3 representative concentration pathways (RCPs): 2.6, 4.5, and 8.5. Response of all key hydrological elements, that is, evapotranspiration, surface run-off, baseflow, and snowmelt, to future climate in 2 typical catchments, the source regions of Yellow and Yangtze rivers, was further investigated by the variable infiltration capacity microscale hydrological model incorporated with a 2-layer energy balance snow model and a frozen soil/permafrost algorithm at a 0.25°´0.25° spatial scale. The results reveal that (a) spatial patterns of precipitation and temperature from RegCM4 agree fairly well with the data from China Meteorological Forcing Dataset, indicating that RegCM4 well reproduces historical climatic information and thus is reliable to support future projection; (b) precipitation increase by 0-70% and temperature rise by 1-4°C would occur in the TP under 3 RCPs. A clear south-eastern-north-western spatial increasing gradient in precipitation would be seen. Besides, under RCP8.5, the peak increase in temperature would approach to 4°C in spring and autumn in the east of the TP; (c) evapotranspiration would increase by 10-60% in 2 source regions due to the temperature rise, surface run-off and baseflow in higher elevation region would experience larger increase dominantly due to the precipitation increase, and streamflow would display general increases by more than 3% and 5% in the source regions of Yellow and Yangtze rivers, respectively; (d) snowmelt contributes 11.1% and 16.2% to total run-off in the source regions of Yellow and Yangtze rivers, respectively, during the baseline period. In the source region of Yangtze River, snowmelt run-off would become more important with increase of 17.5% and 18.3%, respectively, under RCP2.6 and RCP4.5 but decrease of 15.0% under RCP8.5. Abstract Copyright (2018), John Wiley & Sons, Ltd.
2019035284 Tetzlaff, Doerthe (University of Aberdeen, School of Geosciences, Northern Rivers Institute, Aberdeen, United Kingdom); Piovano, Thea; Ala-Aho, Pertti; Smith, Aaron; Carey, Sean K.; Marsh, Philip; Wookey, Philip A.; Street, Lorna E. and Soulsby, Chris. Using stable isotopes to estimate travel times in a data-sparse Arctic catchment; challenges and possible solutions: Hydrological Processes, 32(12), p. 1936-1952, illus. incl. 6 tables, sketch map, 102 ref., June 15, 2018.
Use of isotopes to quantify the temporal dynamics of the transformation of precipitation into run-off has revealed fundamental new insights into catchment flow paths and mixing processes that influence biogeochemical transport. However, catchments underlain by permafrost have received little attention in isotope-based studies, despite their global importance in terms of rapid environmental change. These high-latitude regions offer limited access for data collection during critical periods (e.g., early phases of snowmelt). Additionally, spatio-temporal variable freeze-thaw cycles, together with the development of an active layer, have a time variant influence on catchment hydrology. All of these characteristics make the application of traditional transit time estimation approaches challenging. We describe an isotope-based study undertaken to provide a preliminary assessment of travel times at Siksik Creek in the western Canadian Arctic. We adopted a model-data fusion approach to estimate the volumes and isotopic characteristics of snowpack and meltwater. Using samples collected in the spring/summer, we characterize the isotopic composition of summer rainfall, melt from snow, soil water, and stream water. In addition, soil moisture dynamics and the temporal evolution of the active layer profile were monitored. First approximations of transit times were estimated for soil and streamwater compositions using lumped convolution integral models and temporally variable inputs including snowmelt, ice thaw, and summer rainfall. Comparing transit time estimates using a variety of inputs revealed that transit time was best estimated using all available inflows (i.e., snowmelt, soil ice thaw, and rainfall). Early spring transit times were short, dominated by snowmelt and soil ice thaw and limited catchment storage when soils are predominantly frozen. However, significant and increasing mixing with water in the active layer during the summer resulted in more damped steam water variation and longer mean travel times (~1.5 years). The study has also highlighted key data needs to better constrain travel time estimates in permafrost catchments. Abstract Copyright (2018), John Wiley & Sons, Ltd.
2019035521 Zheleznyak, Il'ya I. (Rossiyskaya Akademiya Nauk, Institut Prirodnykh Resursov, Ekologii i Kriologii, Chita, Russian Federation) and Stetyukha, Vladimir A. Raschet truby iz polimernogo materiala pod deystviyem vneshney nagruzki v skvazhine v massive mnogoletnemerzlykh porod [Numerical analysis of a polymer pipe affected by load pressure in a borehole drilled into the permafrost]: Izvestiya Ural'skogo Gosudarstvennogo Gornogo Universiteta = Izvestiya of the Ural State Mining University, 51(3), p. 121-125 (English sum.), illus. incl. 1 table, 18 ref., 2018.
Relevance of the work is related to the peculiarities of loading the pipe with external pressure in a vertical well located in the rock mass of permafrost. Its results are aimed at ensuring operational reliability and efficiency of geotechnological, engineering-geological and hydro-geological wells. Purpose of this work is to evaluate the ability of a pipe made of polymer material to bear a load. Methodology of research. The working conditions of a vertical pipe made of polymer material in wells of various purposes are examined with consideration of the main climatic and geocryological factors typical of the northern part of cryolithic zone of the Zabaikalye Territory. Additional load is set by an external action caused by freezing of water in a closed annular space accompanied by deformation of the pipe when it is compressed by ice. Methods of thermodynamics were used to study the processes. The stressed-deformed state of an elastic model of the pipe made of polymer material is studied. In determining internal efforts, the LIRA software application was used. Results. The problem of nonlinear heat and mass transfer in the conditions of permafrost is solved. The pipe is calculated for strength and stability under conditions of its compression by ice in annular space. The dependence of the pipe supporting capacity on its diameter, thickness of the ice layer in the annular space and the characteristics of the material is established. The combination of parameters which can lead to loss of stability of the pipe or to its destruction is defined. Conclusion. The necessity of the development of special sizes of pipes with a specified wall thickness is justified. This ensures their stability at loading with external pressure when water freezes in the annular space in terms of negative temperatures of the host geological terrain.
2019041289 Arzhanov, M. M. (Russian Academy of Sciences, Obukhov Institute of Atmospheric Physics, Moscow, Russian Federation) and Mokhov, I. I. Stability of continental relic methane hydrates for the Holocene climatic optimum and for contemporary conditions: Doklady Earth Sciences, 476(2), p. 1163-1167, illus., 15 ref., October 2017. Original Russian Text: M.M. Arzhanov, I.I. Mokhov, 2017, published in Doklady Akademii Nauk, 2017, Vol. 476, No. 4, pp. 456-460.
Modelling of the thermal regime of permafrost soils has made it possible to estimate the stability of methane hydrates in the continental permafrost in the Northern Eurasian and North American regions with the risk of gas emissions into the atmosphere as a result of possible dissociation of gas hydrates in the Holocene Optimum and under contemporary climatic conditions [1, 2]. Copyright 2017 Pleiades Publishing, Ltd.
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2019042887 Akerman, Hans Jonas (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden). Monitoring of the active layer, at Kapp Linne, Svalbard 1972-2018 [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-18844, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The active layer has been monitored in the vicinity of Kapp Linne (78°03'42" 13°37'07"), Svalbard during the period 1972-2018. The sites differ in elevation, distance from the sea, vegetation cover, substrate and active periglacial processes. From 1994, the International Permafrost Association "CALM" standard grids, with measurement within 100´100 m squares, has been applied. Microclimate and soil temperatures have been monitored by data logger covering levels from 2 m above to 7 m below the ground at one of the sites. The macroclimate is covered by complete data series from the nearby weather station at Kapp Linne, covering the period 1912 to 2018. A number of periglacial processes, especially slope processes, are monitored parallel with the active layer. The mean active layer for the sites varies between 1.13 m and 0.43 m. The deepest active layer is found in the exposed, well drained raised beach ridges and the shallowest in the bogs. The interannual variability during the observation period do not correlate well with the MAAT but better with the summer climate, June-August mean or DDT. The data clearly illustrate colder summers during the period 1972 to 1983 and after 1983 steadily increasing summer temperatures. The active layer follows the same general pattern with good correlations. There are several surface indications as a response to the deepening active layer especially in the bogs. Thermokarst scars appear frequently and a majority of the palsa like mounds and pounus have disappeared. A drastic change in the vegetation on the bogs has also occurred, from dry heath to wet Carex-vegetation. In summary the observations from Kapp Linne 1972-2018 are; A clear trend towards milder and longer summers, A clear trend of a deeper active layer, All sites show a similar pattern, The bogs are getting strikingly wetter, the Palsa-like mounds in the bog sites are disappearing, The slow slope processes are getting accelerated, Thermokarst depressions and scars are appearing in a small scale at all sites, Soil temperatures are increasing at all levels down to 7 m. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042895 Andreassen, Karin (Arctic University of Norway, Department of Geology, Centre for Arctic Gas Hydrate, Environment and Climate, Tromso, Norway); Patton, Henry; Vadakkepuliyambatta, Sunil; Serov, Pavel; Hubbard, Alun and Winsborrow, Monica. Methane-leaking Arctic pingo-like features [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-18780, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Large-scale releases of methane from thawing gas hydrates and permafrost is a major concern in a warming Arctic, yet the processes, sources and fluxes involved remain unconstrained. Recent studies from the Barents Sea and Russian Arctic have indicated that giant craters both on the seafloor and on land are imprints of massive methane expulsions from collapsing pingo-like features. Here we combine state-of-the-art marine geophysics with high-resolution ice sheet numerical modelling to investigate how advance and retreat of successive ice sheets of the Barents and Kara Sea areas have influenced deeper hydrocarbon sources, fluid flow plumbing and methane storage and release systems. Case studies will be presented to elucidate the evolution of craters and pingo-like features within different Arctic settings and environments, and to evaluate the sensitivity of methane release to future climate warming. Our new understanding has implications for the prediction of greenhouse gas release from a warming Arctic and the retreating Greenland and Antarctic ice sheets. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042889 Becht, Michael (Catholic University of Eichstätt-Ingolstadt, Physical Geography, Eichstaett, Germany); Heckmann, Tobias; Haas, Florian; Pfeifer, Norbert; Marzeion, Ben; Labuhn, Inga; Disse, Markus; Chiogna, Gabriele and Erschbamer, Brigitta. Sensitivity of alpine geosystems to climate change since 1850; introducing the SEHAG research unit [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-15424, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
In recent years, a multitude of scientific studies has succeeded in verifying the existence of significant climate changes, in particular since the end of the Little Ice Age (c. 1850) and during the last fifty years. Mountain regions are disproportionately affected by global warming and changing precipitation conditions; temperatures in the Alps, for example, have increased by more than twice the global average in recent decades. While some consequences of changing hydrometeorological conditions are clearly visible (the demise of Alpine glaciers has become an emblematic manifestation of climatic change in public perception), others are not well documented and understood. Debris flows, for example, have been shown to react to permafrost degradation, increasing frequency of heavy rain, or to declining debris production in different studies. Together with contingent factors, system-internal dynamics and the interaction of hydrological and geomorphic processes further complicate the investigation of the reaction of geosystem components to climate change. Finally, it is unclear to what extent changes in system components (glaciers, permafrost, surface runoff and river discharge, geomorphic processes on hillslopes, etc.) will propagate through the geosystem to form a catchment-scale response. These research problems are tackled by the SEHAG (SEnsitivity of High Alpine Geosystems to climatic change since c. 1850; funded by DFG and FWF) research unit in three Central Alpine catchments (Kauner-tal/Austria, Horlachtal/Austria and Martelltal/Italy). The SEHAG consortium and its collaborators aim to make use of existing hydrometeorological data and dynamically downscaled reanalysis data to better characterise local climatic change, e.g. changes in the magnitude and frequency of hydrometorological events. These data will drive models that reconstruct glacier dynamics and extent, surface runoff and river discharge within three time slices (1850-1920, 1920-1980, 1980-present). Geomorphic and vegetational changes will be reconstructed using historical aerial and terrestrial photographs by means of stereo- and monophotogrammetric techniques. Such photographs are being retrieved from different historical archives; the first time slice coincides with the emergence of both photography and Alpine tourism. During the project period, present-day rates of hydrological and geomorphic processes, vegetation colonisation and development will be measured in the field, partially continuing existing data series. Results will inform historical geomorphological and landcover maps, quantify changing rates of geomorphic processes, sediment yield and delivery, and assess sediment connectivity. Finally, we will combine information on geomorphic activity, sensitivity to climate change, and connectivity: Where and when active and/or sensitive parts of the catchment are coupled to the channels, we expect a (more) pronounced response related to sediment transfer within the valley, and sediment yield; conversely, a lack of connectivity might buffer the propagation of changes and mitigate the catchment scale response. The understanding of changes and their propagation in the past will help to better estimate the consequences of future changes. A second project phase will be dedicated to the prediction of system trajectories in the decades to come. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042888 Beylich, Achim A. (Geomorphological Field Laboratory (GFL), Selbustrand, Norway) and Laute, Katja. Denudational processes, source-to-sink fluxes and sedimentary budgets under changing climate and anthropogenic impacts in selected drainage basin systems in central Norway and eastern Spain [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-1969, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Climate change, human activities and other perturbations (like, e.g., fires, earthquakes) are likely to influence existing patterns of weathering, erosion, transport and deposition of material across defined landscape components and units. While it is still a challenge to develop an improved understanding of how such changes interact and affect slope and fluvial processes, the connectivity within landscapes and between slope and fluvial systems, as well as contemporary denudation rates, source-to-sink fluxes, and sedimentary budgets, this kind of quantitative analyses promise to be an efficient framework to assess the impact of environmental changes and disturbances to sediment dynamics and to evaluate landscape sensitivity. The current knowledge on drivers and rates of contemporary sediment dynamics and denudation forms the basis for understanding and predicting the consequences of ongoing and accelerated environmental changes. Ongoing GFL research activities on drivers and quantitative rates of contemporary sediment dynamics and chemical and mechanical denudation in selected drainage basin systems in central Norway and eastern Spain are presented. The upper Driva drainage basin in central Norway (Oppdal) is situated in a cold climate and mountainous environment, has year-round discharge with a nival runoff regime, and the temporal variability of sediment transfers, runoff and fluvial transport are largely controlled by thermally and/or pluvially determined events. Our investigations include detailed geomorphological and permafrost mapping combined with the detailed statistical analysis of meteorological data and the continuous observation and year-round monitoring of sediment transfers, runoff and fluvial transport using a range of different techniques in different selected tributary systems of the upper Driva drainage basin. The Pou Roig and Quisi catchment systems in eastern Spain (Calpe) are located in a Mediterranean, partly mountainous and/or anthropogenically affected environment. Sediment transfers, the intermittent runoff and fluvial transport are almost entirely controlled by pluvial events. Our investigations in this study area include detailed geomorphological mapping combined with the detailed statistical analysis of meteorological data and the observation and monitoring of sediment-transfer, runoff and fluvial transport events using a combination of different observation, monitoring and sampling techniques. Our results on controls and the spatio-temporal variability of chemical and mechanical denudation within the two study regions contribute to an advanced understanding of key drivers and rates of contemporary sediment dynamics and denudation in different morphoclimatic environments, and provide the basis for improved predictions of possible effects of climate change and anthropogenic impacts on contemporary denudation rates in different morphoclimatic regions. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042879 Bobrik, Anna (Lomonosov Moscow State University, Department of Soil Science, Moscow, Russian Federation); Petrzhik, Natalia; Timofeeva, Maria and Petrov, Dmitry. Distribution of soil organic carbon along the bioclimatic and permafrost transect from the south taiga to the south tundra of West Siberia [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-463, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Understanding the heterogenity in carbon exchange in terrestrial ecosystems in different permafrost zones is a significant step towards understanding the global carbon cycle. The aim of our study was to assess variability in the soil organic carbon pool and CO2 efflux from the soils in south taiga, north taiga, forest tundra and south tundra zones of West Siberia (Russia). The special grids (100 m*100 m, 121 points of measurements) have been used on all sites. The south tundra research site (Urengoy) is located in continuous permafrost zone (N67°48'; E76°69'). Soils of this research site are characterized by low active layer thickness, CO2 efflux and content of microbial carbon (August 2016). The spatial distribution of CO2 efflux and content of water-extractable organic carbon are strongly correlated with hypsometric levels (r=-0,33, and r=-0,42 respectively, p-level <0,05) in tundra ecosystems. The forest-tundra research site (Urengoy Gas Field) is located in continuous permafrost zone (N66°18', E76°54' The average active layer thickness was 85 10 cm (August 2015). CO2 efflux from peatland soil was low and characterized by high variability. The average content of total organic carbon was high (29.58±5.02). The north taiga research site (Nadym) is located in discontinuous permafrost zone (N65°18', E72°52'). The average active layer thickness was 163±8 cm (August 2015). The CO2 efflux from the peatlands was low (202±37 mg carbon dioxide/m2hr) and characterized by high spatial and temporal variability. The upper horizons of the peatland soils statistically differed from those of the bog in the contents of the total (31.88±3.02 and 37.96±2.00 The south taiga research site (Tumen) is located in seasonal permafrost zone (N57°19', E64°58'). The CO2 efflux from the forest soils was low (170±37 mg carbon dioxide/m2hr) and characterized by high spatial variability (June 2018). All other investigated parameters (environmental parameters, as well as contents of the total, labile and microbial carbon) are characterized by high spatial variability. Despite the wide array of changes in both physical (soil temperature, soil moisture) and biological conditions (vegetation composition, content of labile and microbial soil carbon), our results showed that soil CO2 flux did not vary significantly throughout transect (south taiga-north taiga-forest tundra-south tundra). But depth of permafrost table differed significantly. It explains the necessity of adequate assessment of the spatial variability on the active layer thickness as a significant factor influencing regional CO2 emission. This research has been financially supported by the project No. -1181.2018.5 (grant of the President of Russian Federation). [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042862 Bogorodskii, Petr (Arctic and Antarctic Research Institute, St. Petersburg, Russian Federation); Ermokhina, Kseniya and Kustov, Vasilii. Onset of thermal convection in a permafrost layered ground cover [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-15207, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
A significant part of the Arctic soil, as a rule, is year-round under a moss cover, to which a layer of snow is added in winter. Moss and snow have high insulation properties and consist of a skeleton (organic and ice, respectively) and air-saturated pores, thus forming one system connected by thermal and dynamic interaction. However, in the presence of a temperature gradient, convection may occur within such a system, which significantly reduces the thermal resistance of the layers and, thereby, influences the upper soil layers temperature regime. Our work is aimed to studying the occurrence of convective instability in a system of two porous layers with thermally insulated outer boundaries for conditions that approximately correspond to the moss-snow cover of the arctic deserts of the Bolshevik Isl. (Severnaya Zemlya Archipelago). The solution of the Rayleigh-Darcy problem is obtained by the small parameter method, with expanding the perturbation amplitudes of the vertical velocity and air temperature in rows in even powers of the dimensionless wavenumber. When the ratio of the thickness of the lower layer (moss) to the total thickness of the layers (moss and snow) is h (0<h<1), the critical Rayleigh numbers for the system Ra are functions of the ratio of polynomials of the 1st and 3rd degree relative to h, the coefficients of which are the ratio of the moss and snow characteristics: air permeability K, thermal conductivity k and thermal diffusivity x. The limiting cases h=0 and h=1 correspond to the transition to a single-layer system with the properties of moss and snow, for which Ra=3K/(kx) and Ra=3; respectively. The dependence of the convective instability threshold on variations of the typical species composition and properties of the vegetation and snow cover of the studied territory, parameterized according to measurements and literature data, is estimated. The qualitative differences of the considered problem are shown in comparison with the similar task for homogeneous liquids. A general procedure for solving the Rayleigh-Darcy problem in the long-wave approximation for a multilayer porous system is formulated, which considers the glaciological aspect of problem. Based on theoretical and experimental data, it was concluded that it is necessary to take into account the contribution of convection in layers of moss and snow to thermal, mass and gas exchange between soil and atmosphere. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042847 Callegaro, Alice (Institute for the Dynamics of Environmental Processes, Scienze Ambientali, Informatica e Statistica, Venezia Mestre, Italy); Lodi, Rachele; Spolaor, Andrea; Gabrieli, Jacopo and Barbante, Carlo. Persistent organic pollutants analysis in environmental matrices from polar areas [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-395, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Persistent organic pollutants (POPs) are organic chemical substances of scientific concern, widely produced in the form of pesticides, industrial chemicals and unintentional by-products. POPs retain particular physicochemical properties and structures such that they have the ability, with a long-range "grasshopper effect" transport, to travel over great distances and reach the polar areas through oceanic and atmospheric pathways. Once discharged into the environment, these contaminants persist for exceptionally long periods of time, and, due to their lipophilic characteristics, have the tendency to bioaccumulate in the biological fatty tissues, with negative impacts and toxic effects on multiple organisms, including humans. This work moves towards the study of polar areas pollution with two approaches, considering the contamination of remote areas (Antarctica) and the possible remobilisation of past accumulated POPs into the sea because of permafrost thawing (Arctic), one of the most problematic tipping point due to climate change. In order to analyse POPs in different environmental matrices, permafrost active layer and ice samples has been collected in different locations: Ny-Alesund-Svalbard Islands (permafrost), Yukon Coast-Canada (permafrost) and Dome C-Antarctica (ice core). Samples are treated with different analytical methods in order to detect different groups of POPs, such as polychlorobiphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and polybrominated diphenyl ethers (PBDEs). Prior to handling procedure, samples are spiked with internal isotope-labelled standards. Permafrost samples are firstly freeze-dried and homogenised. Then, accelerated solvent extraction is performed with a mixture of dichloromethane and hexane, followed by solid phase extraction clean-up. Ice samples treatment starts with melting at a low temperature, followed by a pre-concentration step with Oasis HLB cartridges. Then, samples are eluted with dichloromethane and hexane in order to extract the analytes. Both permafrost and ice eluates are spiked with a recovery standard and finally injected into a 6890A gas chromatographer coupled with a 5975C MSD (Agilent Tech.), that performs the identification and quantification of diverse classes of molecules. The main outcome is the achievement of a complete and detailed newsworthy POPs dataset, that allows the comparison with other literature studies about POPs contamination in Antarctic and Arctic regions. Moreover, the integration between Canadian and Svalbard data has no precedent for permafrost as environmental matrix for POPs analysis. Finally, this results positively impact on the local societies, that would have new insigths on the thawing permafrost issue, becoming aware about this problem from the organic pollution point of view. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042892 Carey, Joanna (Babson College, Division of Math & Science). Arctic land cover change alters silica retention in terrestrial biomass and export rates to aquatic systems [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-6330, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Human activities exert an unprecedented reach on the biosphere, a reach that is strengthening in many respects due to climate change. There is a growing body of evidence highlighting that human activities have a direct impact on the global silica cycle. In addition to river damming and nutrient over-enrichment, land cover change is another important way by which humans are altering silica exports from terrestrial to aquatic systems. Understanding the controls on silica exports from terrestrial systems has direct implications for silica availability and carbon cycling in coastal receiving waters, due to the reliance of diatoms on silica. Due to rapid climatic warming, the Arctic is undergoing land cover change in the form of shrub expansion, increasing extent and frequency of wildfires, extended growing season length, and northern migration of the treeline. Moreover, permafrost thaw alters watershed hydrology by deepening flowpath lengths and soil-water interaction times. All of these changes are likely to alter rates of silica exchange between terrestrial and aquatic ecosystems. This talk will synthesize recent findings from the Alaskan Arctic demonstrating how rapid climate warming and associated shifts in watershed land cover and hydrology is altering silica cycling in terrestrial and freshwater aquatic systems. We will present evidence demonstrating that shrub expansion and wildfire both serve to increase the amount of silica sequestered in land plants, strengthening the magnitude of the terrestrial silica pump at local scales. Conversely, degradation of permafrost results and deepening of the active layer increases total silica exports from terrestrial systems via rivers at larger regional scales. It remains to be seen whether small-scale increases in silica retention via land plants can offset larger-scale silica releases from thawing permafrost over time. I will also address the implications of these results in the context of the global silica cycle. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042886 Chaudhary, Nitin (University of Oslo, Department of Geosciences, Oslo, Norway); Westermann, Sebastian; Lamba, Shubhangi; Shurpali, Narasinha; Schugers, Guy; Miller, Paul A. and Smith, Benjamin. Peatland carbon dynamics at different scales across the pan-Arctic using an improved modelling approach [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-5605, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The majority of northern peatlands were initiated during the Holocene around 8-12 thousand years ago . Owing to their mass imbalance, they have sequestered huge amounts of carbon in the terrestrial ecosystem . Distribution of soil organic carbon is widespread and uneven across the pan-Arctic . Recent syntheses have filled some existing gaps [2, 4]; however, the extent and remoteness of many locations pose challenges to develop a reliable regional carbon accumulation estimate. In this work, we combined three published peat basal age datasets [1, 5, 6] with some independent measurements [2, 4, 7] to form a most up-to-date peat basal age surface for the pan-Arctic region which we then used to constrain the model in order to reduce the current and future uncertainties related to the northern peatlands carbon cycle. We employed an individual- and patch- based dynamic global vegetation model (LPJ-GUESS) [7, 8] with dynamic peatland and permafrost functionality to quantify the long-term carbon accumulation rates and to assess the effects of historical and projected climate change on peatland carbon balance. We divided our analysis into two parts- the carbon accumulation changes detected within observed peatland boundary  and at pan-Arctic scale under two contrasting scenarios (RCP8.5 and RCP 2.6). Our results are largely consistent with published long-term carbon accumulation rates. We found that peatlands would continue to act as carbon sink under both scenarios but their sink capacity would substantially reduce under RCP8.5 scenario after 2050. The 286 sites within the observed boundary showed similar behaviour as pan-Arctic scale but their carbon sink capacity would be further strengthened under RCP 2.6. Additionally, areas, where peat production was initially hampered by permafrost and low productivity, would accumulate more carbon because of the initial warming, moisture-rich environment due to permafrost thaw, higher precipitation and elevated CO2 levels. On the other hand, areas which experience reduced precipitation rates and without permafrost will lose more carbon in the near future, particularly, peatlands located in the European region and between 45-55 N latitude. References: 1. MacDonald et al., Rapid Early Development of Circumarctic Peatlands and Atmospheric CH4 and CO2 Variations. Science, 2006; 2. Yu et al., Sensitivity of Northern Peatland Carbon Dynamics to Holocene Climate Change, in Carbon Cycling in Northern Peatlands. 2009; 3. Yu, et al., Holocene peatland carbon dynamics in the circum-Arctic region: An introduction. Holocene, 2014; 4. Loisel, et al., A database and synthesis of northern peatland soil properties and Holocene carbon and nitrogen accumulation. Holocene, 2014; 5. Gorham, et al., Temporal and spatial aspects of peatland initiation following deglaciation in North America. Quaternary Science Reviews, 2007; 6. Korhola, et al., The importance of northern peatland expansion to the late-Holocene rise of atmospheric methane. Quaternary Science Reviews, 2010; 7. Chaudhary, et al., Modelling Holocene peatland dynamics with an individual-based dynamic vegetation model. Biogeosciences, 2017; 8. Chaudhary, et al., Modelling past, present and future peatland carbon accumulation across the pan-Arctic region. Biogeosciences, 2017; 9. Xu, J. R., et al., PEATMAP: Refining estimates of global peatland distribution based on a meta-analysis. Catena, 2018. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042859 Cui Aihong (Hong Kong Baptist University, Department of Geography, Hong Kong, China); Li Jianfeng; Zhou Qiming; Wu Guofeng and Li Qingquan. Global hydrological drought measurement using GRACE terrestrial water storage deficit [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-12218, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Hydrological droughts bring about great losses in agriculture, ecosystem and socioeconomics, so it is important to establish hydrological models or indicators to describe the occurrence, severity and duration of drought. But it remains challenging to obtain the whole relevant hydrological variables (e.g.., surface water, soil moisture, and groundwater) on the appropriate temporal and spatial scales. Now the Gravity Recovery and Climate Experiment (GRACE) satellite observations can provide realistic spatiotemporal variations of vertically integrated measurement of water storage (groundwater, glacier ice, soil moisture, surface water, snow water equivalent, permafrost, etc.) at large research area. Here we present a new GRACE-derived index (GNSI) to investigate drought conditions and evaluate its applicability. We obtain the Release-05 GRACE terrestrial water storage data from the University of Texas Center for Space Research and precipitation data in the high spatial resolution from the version 4.02 of the gridded Climatic Research Unit Time-series dataset from March 2002 to December 2016. We choose July 2010 in which drought occurred in many countries as an example to evaluate the performances of the drought indices. The GNSI and Standardized Precipitation Index (SPI) reach good agreement in the spatial distribution of drought conditions in south China, northern India, western Russia, middle Europe, west side of South America and Western Australia. However, the intensities among the two indices in some regions are different, such as in the middle of China, United States and Greenland. In the middle of China, the GNSI detects more normal area while SPI captures some dry conditions. In the northern part of the United States, the GNSI reveals two obvious drought regions whereas the SPI does not. Furthermore, GNSI is compared with SPI at different time scales. The GNSI shows time lag about three months compared with SPI. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042846 de Vrese, Philipp (Max Planck Institute for Meteorology, Land in the Earth System, Hamburg, Germany); Brovkin, Victor and Kleinen, Thomas. Permafrost degradation in the representative concentration pathway RCP8.5 [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-14371, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Almost a quarter of the ice-free terrestrial area in the northern hemisphere is underlain by permafrost, i.e. ground whose temperature remains below the freezing point for a period of at least two years. But with global temperatures rising, these areas are loosing in size, especially as temperatures in the Arctic region increase twice as fast as the global mean. If the radiative forcing follows the RCP8.5 trajectory, it is only a question of time until permafrost has largely vanished. Permafrost-affected soils have accumulated vast pools of organic carbon since the temperatures and the availability of liquid water that are characteristic for permafrost strongly inhibit the decomposition of organic material. In the northern hemisphere, these soils contain about 1300-1700 gigatons of carbon, which is more than all carbon held by global vegetation and Earth's atmosphere combined. When permafrost thaws, the degradation of the newly available organic material results in an increased formation of trace gases which will be released into the atmosphere, further increasing the green-house effect, hence temperatures. Thus, permafrost degradation has the potential to form an important positive feedback on climate warming, especially if a large fraction of the decomposing soil carbon is released in form of CH4 rather than the less potent CO2, and is considered an important tipping element in the climate system. For the range of the RCP8.5 trajectory, we investigate the long-term permafrost degradation corresponding to a given radiative forcing level, the resulting trace-gas emissions, i.e. CO2 and CH4 emissions due to the decomposition of soil organic material, and their potential to contribute to a positive feedback. For this, we use an adapted version of JSBACH, the land-surface component of the Max-Planck-Institute for Meteorology's Earth System Model. In addition to the standard version of the model, we include the advanced soil physics, which represent the melting and freezing of water in the soil, and an improved characterization of the effect that soil organic material has on the soil thermal and hydrological properties. Furthermore, we use a new soil carbon model that represents the vertical structure of the organic material and accounts for depth dependent decomposition rates. Finally, we include a diagnostic wetland scheme and a scheme representing the formation and transport of gases in the soil, which allows us to determine the release of CH4 and CO2 to the atmosphere. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042894 Dolven, Knut Ola (University of Tromso, Department of Geosciences, Centre for Arctic Gas Hydrate, Environment and Climate, Tromso, Norway) and Ferré, Bénédicte. Long-term multi-variable time series of seep sites offshore West Spitsbergen [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-14264, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The West Svalbard continental margin is an area of prominent methane seepage where shallow gas accumulation and release of methane gas to the water column have been observed. Methane release has been linked to both gas hydrate dissociation, melting permafrost, and vertical migration from deeper gas reservoirs, and the exact cause of seepage is still not fully understood (e.g. Sahling et al., 2014). Several factors have been suggested to affect the methane release, such as seasonal fluctuations in bottom water temperatures and pressure changes due to ocean tides (Berndt et al., 2014; Romer et al., 2016). Investigations of methane release in the area are mostly based on point measurements acquired when sea and ice conditions allow for ship access, making both long and short term monitoring challenging. To shed more light on the temporal nature of the seep sites offshore Western Svalbard, two ocean observatories equipped with a wide array of instruments were deployed from June 2015 to May 2016 at 250 and 90 m depth where thousands of methane seeps have been observed. The time-series highlight rapid and drastic changes in methane concentration up to several hundreds of nmol/kg within a few hours. The main driver for these rapid changes is the ocean currents and observations indicate that seepage persisted throughout the whole annual cycle. High concentrations of methane (up to 1400 nmol/kg) were observed during periods of calm winds and ocean conditions, suggesting that the available energy for ocean mixing impacted the distribution of the methane. A decreased methane concentration in winter was not correlated with decreasing ocean temperatures and no relationship was found between the methane concentration and changes in hydrostatic pressure. The research is part of the Centre for Arctic Gas Hydrate, Environment and Climate (CAGE) and is supported by the Research Council of Norway through its Centres of Excellence funding scheme grant No. 223259 and UiT. Berndt, C., et al. (2014). Temporal Constraints on Hydrate-Controlled Methane Seepage off Svalbard. Science, 343(6168):284-287. Romer, M., et al. (2016). Tidally controlled gas bubble emissions: A comprehensive study using long-term monitoring data from the NEPTUNE cabled observatory offshore Vancouver Island. Geochemistry, Geophysics, Geosystems, 17(9):3797-3814. Sahling, H. et al. (2014). Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification. Biogeosciences, 11(21):6029-6046. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042848 Douglas, Thomas A. (Cold Regions Research and Engineering Laboratory, Biogeochemical Sciences, Fort Wainwright, AK) and Blum, Joel. Tracking mercury from the snowpack through spring melt in a High Arctic watershed near Utqiagvik, Alaska [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-4635, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Mercury (Hg) is a bioaccumulative toxin that has been found at high concentrations in snow and ice at Arctic coastal locations. It is likely that atmospheric deposition is the source of this elevated Hg but the ultimate fate of snowpack Hg is largely unknown. To investigate this, we measured mercury (Hg) and major ion concentrations and Hg stable isotope ratios of snowpack and melt water through spring melt runoff for two years at a site near Utqiagvik (formerly Barrow), Alaska. We also collected peat and permafrost sediment cores for Hg concentration and Hg stable isotope measurements. The field site is a small (2.5 ha) watershed on the Arctic coastal plain. The area is known to be exposed to Arctic Mercury Depletion Events (AMDEs) with Hg concentrations in snow and sea ice sometimes approaching 1,000 ng/L. AMDEs are unique high Arctic atmospheric events in which reactive halogens in air, snow, and sea ice facilitate oxidation of atmospheric Hg and deposition to the snowpack. In late winter prior to snow melt (April) and during snowmelt runoff (May and June) in 2008 and 2009, we made more than 10,000 snow depth measurements and 80 snowpack water equivalent measurements in the watershed. Snowpack, meltwater, and runoff from a small stream were sampled and analyzed for total dissolved Hg, major ions, and stable oxygen and hydrogen isotopes. Airborne LiDAR and and high resolution GPS surveys allowed delineation of the watershed area. Based on our variety of samples we identified an "ionic pulse" of mercury and major ions in snowmelt runoff during both seasons. Total dissolved Hg in runoff was 14.3 (±0.7) mg/ha in 2008 and 8.1 (±0.4) mg/ha in 2009. This is five to seven times higher than what has been reported from lower latitudes. We calculate 78% of snowpack Hg was exported with snowmelt runoff in 2008 and 41% in 2009. Hg stable isotope measurements indicate the majority of Hg in snow melt originated as gaseous elemental mercury (Hg(0)) and was likely oxidized in the snowpack by reactive halogens. 75% of the Hg exported from our watershed in snow melt came from non-AMDE sources while we attribute 25% to AMDEs. Our Hg stable isotope analyses indicate Hg was deposited directly to the snowpack as GEM (Hg(0)) and converted to Hg(II) in the snowpack by reactive halogens. We surmise the halogen rich snowpack facilitated oxidation and retention of gaseous elemental Hg. This Hg comprises the majority of the mercury that remains until snowmelt and discharged into surface meltwaters of our Arctic coastal ecosystem. Projected future warming in the Arctic will produce an increasingly dynamic sea ice regime with more first year ice and open sea ice leads. This will likely enhance the source of reactive halogens, promote GEM oxidation, and lead to greater Hg deposition to coastal and marine snowpacks. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042852 Duvillard, Pierre-Allain (Université Grenoble Alpes-Université Savoie Mont-Blanc, France); Ravanel, Ludovic; Marcer, Marco and Schoeneich, Philippe. Are damages to infrastructure at high elevation in the French Alps related to permafrost warming? [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-5979, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Ski resorts have been extensively developed in the French Alps over the past four decades and several hundred ropeway transport systems have been installed on permafrost. Due to current climatic change, the vulnerability to destabilization of these infrastructures may increase. There is indeed a high risk for developing instabilities. A better understanding of the processes involved is thus needed. This study investigates the relation between permafrost and infrastructure stability, trying to understand the evolution of this phenomenon over the past decades. This was done by following a two steps analysis in the framework of the EU POIA Project PermaRisk. First, the infrastructure elements built on modelled permafrost areas were inventoried at the French Alps scale in order to get an overview of the possible vulnerabilities. Then, this study presents a detailed historical inventory of damage to infrastructure over the past three decades in different geomorphologic contexts. Overall, in the French Alps, there are about thousand infrastructure elements located in permafrost areas. In this study, 12 infrastructures (24 infrastructures elements) were identified as having been affected by repeated instances of disruption and deterioration and most of the damage recorded were in areas where permafrost degradation was fully expected (ice-rich terrain at relatively low elevations). Infrastructure recovery costs may be significantly high, making this issue a relevant process to be took into account in the design process. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042855 Fischer, Mauro (University of Bern, Institute of Geography, Geomorphology, Natural Hazard and Risk Research, Bern, Switzerland) and Keiler, Margreth. Implications of the rapid disappearance of Glacier du Sex Rouge (western Swiss Alps) for local multi-hazard and risk assessment at Les Diablerets [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13610, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
This case study presents preliminary results of an in-depth application of state-of-the-art multi-hazard and risk assessment strategies (see e.g. Schaub 2015) to identify and assess present and future impacts, vulnerabilities and risks related to the currently observed rapid changes of the high-mountain cryosphere in the catchment of Glacier du Sex Rouge. Glacier du Sex Rouge, a very small and rapidly shrinking glacier in the western Swiss Alps, is projected to completely disappear around 2030. The current glacier bed topography has been investigated based on close meshed ground penetrating radar (GPR) surveys and shows a trough-shaped structure, i.e. an overdeepening confined to all sides formed by past glacier erosion. Evidence for the potential formation of a future new lake can already be observed at the location of today's glacier terminus during summer. The possible lake formation might change the hazard and risk potential for population and infrastructure in the area of Les Diablerets (1162 m a.s.l., a village situated 6 km from Glacier du Sex Rouge) or even further down-valley. Impact waves triggered due to rock fall from the steep northwest face of Oldehore/Becca d'Audon (3123 m a.s.l.) with occurring permafrost could potentially overtop the lake's rock dam and initiate a flood wave which might--considering the notable amount of loose debris currently accumulated in the forefield of Glacier du Sex Rouge--develop into a debris-flow by sediment entrainment along its flow path. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042900 Fleischer, Fabian (University of Salzburg, Department of Geography and Geology, Salzburg, Austria); Otto, Jan-Christoph and Hölbling, Daniel. Change of debris cover on glaciers of the Eastern Alps, Austria [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-15276, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Debris cover on glaciers influences climate-glacier dynamics by controlling surface energy and mass balance of glaciers. In effect, glacier flow dynamics and glacier melt are strongly influenced by superficial debris. Debris input is a result of bedrock weathering and rockfall processes at the surrounding rockfaces, which are often affected by permafrost conditions. Changes in air temperatures, permafrost melt, as well as increased release of fresh rock faces due to melt down of glaciers in the accumulation zone can lead to increased rockfall activity and contribute to more debris input. Additionally, negative mass balances may lead to an enhanced melt-out of englacial debris in the ablation zone and consequently to an increase in debris cover. Thus, debris cover of glaciers can represent a signal of ongoing effects of climate change in mountain areas. In the European Alps a strong increase of mean air temperatures has been observed within the last 35 years, which led to corresponding negative mass balances and an acceleration of glacier melt rates throughout the region. Following this trend, debris cover of glaciers should have increased as well. In order to test this hypothesis we assessed the temporal evolution of supraglacial debris cover on glaciers of the Eastern Alps, Austria. We mapped debris cover on 255 glaciers utilizing a ratio-based threshold classification method with Landsat data at three time steps between 1996 and 2015. Results were compared with manually mapped debris covers from orthophotos for accuracy assessment. We found no general trend towards an increase in the total debris-covered area, but observed an increase in relative debris cover. More than 18% of the glaciers exhibited a continued increase in debris-covered area within the period of observation, however many glaciers displayed varying changes of supraglacial debris. We relate this to an up-glacier rise in debris cover due to increasing debris input and a concurrent intense retreat of the debris-covered glacier front. Both processes seem to vary with time and have a high variability among individual glaciers. The investigated glaciers of the Eastern Alps are much smaller and are located at lower elevations compared to other studies on debris-covered glaciers in other mountain regions, like the Himalayas. In contrast to larger glaciers at higher elevations, negative mass balances do not lead to an increase in debris cover on the majority of glaciers in the Eastern Alps. Whereas, debris covers on many high altitude glaciers of the Himalayas often leads to a stagnation of the glacier terminus and subsequent debris cover area increase with time. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042853 Frey, Holger (University of Zurich, Department of Geography, Zurich, Switzerland); Allen, Simon; Manchado, Alberto Muñoz Torrero; Emmer, Adam; Huggel, Christian and Kashyap, Divya. Developing a framework for the management of glacial risks in India [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-9182, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Natural catastrophes and disasters in high mountain areas often consist of chains of interacting processes rather than isolated ones. Different components of the environmental system react to changes in climatic conditions on differing temporal and spatial scales, leading to new and often historically unprecedented hazards. At the same time, rising population, expanding settlements and growing infrastructure in many mountain ranges worldwide increasingly expose human lives and assets to these hazards, exacerbating resulting risks. As such, the design and implementation of flexible and adaptive risk management strategies are essential prerequisites for sustainable development in the future. Recently, the Standing Group on Glacier and Permafrost Hazards (GAPHAZ) of the International Association of Cryospheric Sciences and International Permafrost Association (IACS/IPA) published a guideline document for the assessment and mapping of glacier and permafrost related hazards. These guidelines propose future oriented and scenario based hazard assessment procedures by applying physically based numerical models for the simulation of related, cascading processes, which is a relatively new field of research. In parallel, mitigation of climate-related risks in recent years has undergone a shift in focus from engineering centered hazard prevention approaches towards more holistic, risk oriented management strategies. Besides structural mitigation measures, such approaches also consider different types of non-structural measures for lowering the risks by reducing exposure and vulnerability, or aiming at increased resilience. In this contribution, we present the development of a framework for the management of glacier related hazards and risks in India--a work supported by the Global Programme Climate Change of the Swiss Agency for Development and Cooperation. In a first step, a review of existing data on glacial lakes and related hazards and risks is undertaken, aiming at the development of nationwide glacial lake hazard inventory. This will provide the basis for prioritising where on-ground mitigation efforts may eventually be focussed. In parallel, a group of scientific experts is expanding on existing guidelines and experiences with hazard and risk management in other countries with glaciated mountain ranges. Building on such international best practices and at the same time reflecting regional specifics of the Indian Himalayas (and particularly the priority areas identified), guidelines for glacier related hazard and risk assessments in India, with a special focus on risks of glacial lake outburst floods (GLOFs), will be drafted. These guidelines will be accompanied by a report on integrated risk management options, including suggested structural and non-structural measures. Semi-final versions of these guidelines will be discussed during participatory workshops in close cooperation with National Disaster Management Authority (NDMA) of India, the group of scientific experts and other stakeholders. By following this procedure, we want to guarantee that the guidelines will fully benefit from the international scientific state-of-the art knowledge and experience, and at the same time consider the specifics of the Indian Himalayas and eventually be tailored to the identified particular needs of this region. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042882 Goncharova, Olga (Lomonosov Moscow State University, Soil Science, Moscow, Russian Federation); Matyshak, Georgy; Bobrik, Anna; Tarkhov, Matvey; Timofeeva, Maria; Sefilian, Anna; Petrov, Dmitry and Ryzhova, Irina. Hot spots and leading factors of the spatial distribution of organic and inorganic carbon fluxes on a wetland complex; three days in the palsa life (West Siberia, Russia) [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-7843, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Northern ecosystems are crucial to the global carbon cycle because they are rich in organic carbon, which has built up in frozen soils, litter, and peat (Schuur et al., 2008). Although climate change is expected to lead to permafrost thawing and an increase in greenhouse gas fluxes between soils and the atmosphere (Koven et al., 2011), the regulating factors of organic matter decomposition and translocation in the seasonally thawed active layer, however, are insufficiently understood to confidently predict the feedback of thawing permafrost to global warming. The aim of this study was to identify hot spots and leading factors of the spatial distribution of organic and inorganic carbon fluxes on a wetland complex of North West Siberia. The study included a simultaneous measurement of some labile indicators of soils and natural waters, as well as environmental factors for a single small area of palsa and surrounding wetlands (august 2016, 2017, and 2018). The research area is located in the discontinuous permafrost zone in the northern taiga of West Siberia, Russia. Palsa, the object of this study, is 1 m high above the surrounding wetlands and is about 30 m in diameter. It is flat with a slight slope and abrupt edge to the bogs. Typical vegetation is various lichens and mosses, dwarf birch, sedge. The average thickness of peat is 30 cm. The test points were arranged in circles: central, middle, edge of the palsa and wetland (without permafrost) near the palsa. The interannual variability of weather conditions determined the difference in soil temperature, the active layer thickness, and the CO2 efflux. However, all the patterns of spatial distribution of these indicators were identical. The minimum active layer thickness was at the middle part of the peatland, and the maximum was in the center and on the edge. The minimum soil temperatures were observed in the middle part of palsa, in areas with shallow permafrost. In the same part, the minimum values of CO2 efflux from the soil surface and CO2 concentrations in the suprapermafrost layer were also noted. Directly near the edge of the palsa, high values of dissolved organic carbon (DOC) (up to 90 mg/l) and CO2 concentration (headspace equilibration method, up to 17000 ppm) in bog water were recorded. With increasing distance from the palsa CO2 and DOC concentration decreased. We assume that such variations in CO2 flux and DOC concentrations are due to its lateral transport in the soil, especially in the suprapermafrost layer. Thus, the peatland edge is a hot spot of carbon exchange between soil, natural waters and the atmosphere. And the redistribution of carbon flux depends largely on the topography of the permafrost table. This research was supported by the Russian Foundation for Basic Research (Grant 18-04-00952). References Koven, C. D., Ringeval, B., Friedlingstein, P., et al., 2011. Permafrost carbon-climate feedbacks accelerate global warming. Proceedings of the National Academy of Sciences 108: 14769-14774. Schuur, E. A. G., Bockheim, J., Canadell, J. G. et al., 2008. Vulnerability of permafrost carbon to climate change: implications for the global carbon cycle. BioScience 58(8): 701-714. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042877 Grau, Oriol (Center for Ecological Research and Forestry Application, Catalonia, Spain); Margalef, Olga; Joosten, Hans; Fernández, Pere Roc; Dorrepaal, Ellen; Keuper, Frida; Richter, Andreas; Sardans, Jordi and Peñuelas, Josep. Impacts of fast vs. slow permafrost thaw on nitrogen and phosphorus availability in a subarctic palsa mire [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13493, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Subarctic permafrost peatlands are particularly sensitive to climate warming. The progressive degradation of permafrost in these ecosystems promotes the decomposition of old organic matter in deep soil layers and re-activates the cycling of C and nutrients. Several studies reported that thawing of permafrost in subarctic peatlands increases nitrogen (N) availability for plants and microbes, ecosystem productivity as well as CH4 and CO2 emissions. Very little is known, however, about phosphorus (P) availability after permafrost degradation and about possible changes of C:N:P ratios in soil and vegetation. In June 2018 we collected soil samples from several palsas (peat mounds with a permafrost core) at Stordalen (Abisko, 68°N, Sweden). We sampled at four different depths: two above the active layer (5-10 and 40-45 cm) and two in the permafrost (70-75 and 95-100 cm). We incubated the samples at 0.1°C (thaw front temperature) and 10.5°C (summer rooting zone soil temperature) over 120 days, similar to the length of the growing season. These two temperatures simulated slow vs. fast thawing of permafrost, which are associated with a deepening of the active layer or with a complete disappearance of the permafrost, respectively. We determined total C, N and P, available P, Hedley P and available N from pre-incubation and incubated samples. The availability of P was highest near the surface of the palsa in pre-incubation samples, and lower at deeper layers; the N:P ratio was consistently higher at deeper layers. The samples exposed to 10.5°C showed a very significant increase in N and P availability and a decrease in N:P ratio. Our results indicate that in intact, oligotrophic palsa the relative availability of P might be higher than that of N, whereas the opposite may apply after permafrost thawing. Such shift in relative nutrient availability is crucial to understand changes in stoichiometry in the soil and vegetation, in ecosystem productivity, C fixation and ecosystem functioning when palsas in subarctic mires collapse by permafrost thaw. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042881 Hashemi, Joshua (San Diego State University, Global Change Research Group, San Diego, CA); Arndt, Kyle; Kalhori, Aram; Zona, Donatella and Oechel, Walter. Carbon loss vulnerability to climate change in Arctic wetland soils [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-548, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Arctic warming continues to occur at an unprecedented rate, causing increased methane (CH4) and carbon dioxide (CO2) emissions in an environment that has been a long-term carbon sink. Warming in these regions destabilizes large soil carbon deposits, making the Arctic particularly vulnerable to positive feedback amplification. Sub-surface CO2 and CH4 production and consumption outside of the growing season is one of the least studied and most debated positive feedbacks on Arctic warming. Recently, Arctic soils have been recognized to emit significant amounts of CH4 and CO2 in the cold season, particularly during shoulder periods when air and surface soil temperatures are below freezing, and subsurface temperatures remain unfrozen (referred to as the "zero-curtain"). This is associated with the presence of an unfrozen anoxic soil layer, warmer than surrounding soil temperatures, where microbes are active well into the winter. Higher soil water content, which is correlated to larger CH4 emissions, further extends the duration of unfrozen soil. Given that the effects of climate change are particularly intense during the cold season (e.g. the duration of the zero-curtain is increasing over the last decade) and ecosystem hydrology is shifting, gaining an increased understanding of soil carbon cycling during non-growing seasons is of vital importance to refine predictions of Arctic carbon sensitivity in a changing climate. To this purpose, this study records year-round, continuously measurements of soil carbon (CH4 and CO2) concentration (in-situ) at different soil layers to understand how thawing of the active layer and permafrost will ultimately affect soil carbon production, storage and release to the atmosphere. We show evidence that soil carbon is biogenically produced in the fall shoulder period, well after the surface has frozen in Arctic ecosystems. Data obtained will help to better understand carbon dynamics in the soil column throughout the year and importantly, during non-growing seasons. This dataset is crucial in understanding cold season emissions and identifying trends in soil-atmospheric interplay in the Arctic. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042901 Hauck, Christian (University of Fribourg, Department of Geosciences, Fribourg, Switzerland). Geophysical monitoring techniques to observe alpine permafrost degradation; a 20-years perspective [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-4195, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The application of geophysical techniques has a long tradition in permafrost research, however, the use of standard techniques such as geoelectrics or seismics for operational monitoring purposes in permafrost terrain started much more recently. The longest time series available reach now almost two decades, which makes them suitable for analysis of spatio-temporal changes and corresponding processes in a climate related context. Within this time period, significant changes in the permafrost characteristics, such as active layer deepening and ground ice loss, have been observed in several European mountain permafrost environments. From the variety of geophysical techniques, especially electrical methods such as Electrical Resistivity Tomography (ERT) are cost-effective and logistically feasible for application in high mountain terrain, because a fixed installation of electrodes is cheap, robust and ensures an exact repetition of measurement geometry over several years. Besides, it poses no danger to the environment, nor does it affect the surface and subsurface characteristics. However, geophysical monitoring data require different filtering and inversion algorithms than data from individual surveys. Furthermore, the resulting electrical resistivities (or P-wave velocities in the case of seismic monitoring) have to be related to physical properties such as ice/water content or temperature in a consistent way for the whole time series and their spatial distribution in the tomogram. In this contribution, several of the existing approaches will be reviewed by showing some examples from the longest geophysical time series available in European mountains. The results highlight not only the feasibility of long-term geophysical monitoring in permafrost terrain, but also the clear degradation trend of permafrost occurrences during the past two decades. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042893 Hömberg, Annkathrin (Universitat Bayreuth, Umweltgeochemie, Bayreuth, Germany); Knorr, Klaus-Holger; Obst, Martin and Schaller, Jörg. Increased silicon availability in fen peat; dissolution of Fe-phosphates and changes in DOC quality under oxic conditions [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-2269, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
A recent study showed elevated carbon dioxide (CO2) and methane (CH4) concentrations in peatland soils under increased Silicon (Si) availability. In another recent study, Si was furthermore shown to mobilize nutrients such as phosphorus (P) into the soil solution of permafrost soils by dissolution of iron (Fe)-phosphates. The mechanism is conjectured either to be found in the dissolution of Fe-phosphates releasing P into the soil solution which stimulates microbial respiration or in a direct influence of Si on the organic matter quality which in turn would have the same effect. To elucidate possible causes of these observed effects, we conducted incubation experiments under addition of Si and/or iron oxyhydroxides (FeOOH) and measured CH4 and CO2 formation rates. In another batch experiment we added amorphous Si to fen peat material and incubated this for two days on a rotating shaker. The suspended organic matter was then used for an X-ray absorption spectroscopy (XAS) analysis at the C1s and the Fe2p edge. We hypothesized that [I] there is a difference in the effects on respiration rates between oxic and anoxic conditions, entailing the existence or absence of oxidized Fe respectively. Moreover we expected [II] a higher concentration of P and Fe and dissolved organic carbon (DOC) under high Si availability caused by dissolution of colloidal Fe-phosphates and [III] changes in the DOC quality, which might explain or instead be explained by the differences in respiration measured under field conditions in another study. We did not find any effect of Si addition under strictly anoxic conditions, however significantly higher CO2 and CH4 respiration rates under initially oxic conditions. In the two day experiment significantly higher concentrations of P and Fe and marginally not significantly higher concentrations of DOC were found. Using XAS we assume a dissolution of Fe-phosphates and a change in the organic matter quality that is to say smaller peak areas of quinones and carboxyl-groups under high Si availability. A hypothetical model of explanation was developed: Si leads to a fast dissolution of Fe-phosphates, thereby increases the nutrient availability in the incubations and thus leads to an increased degradation particularly of oxidized parts of the OM like quinones and carboxyl-groups. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042869 Ilinskiy, Dmitry (Moscow Institute of Physics and Technology, Laboratory of Geophysical Reseach of Arctic and Continental Margins, Dolgoprudny, Russian Federation); Ganzha, Oleg; Roginskiy, Konstantin and Lobkovskiy, Leopold. Towards implementation of seabed seismological network in Laptev Sea and mega seeps geo-structural study by 3D active nodal array [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-11116, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The current studies were conducted during the 73th scientific cruise to the Laptev Sea as part of the Russian Academy of Science Arctic Research Program onboard of R/V "Academic Mstislav Keldysh". The network of broad band ocean bottom seismometers (BB OBS) with long term autonomy was installed in order to investigate the Laptev Sea seismic regime and its possible relation to the Laptev Sea shelf permafrost degradation; to detect and locate active tectonic faults and microplate boundaries within the investigation area and to perform deep sounding of the Laptev Sea earth crust by using tele-seismic events. The previous studies showed that the degradation of permafrost in the Russian Arctic seas represents one of the major fast-growing sources of methane emission at the Northern hemisphere. Such phenomenon dramatically affects the present-day climate change and global warming, especially in the Northern hemisphere. There are many observations in the Laptev Sea (mostly with multi-beam echo sounders) of so-called Mega Seeps, which are exhibited as methane gas chimney rising from the seafloor to the sea surface. Year to year observations in the Laptev Sea show a significant growth of the number of existing Mega seeps and their size. The imaging of the seafloor deep structure in the vicinity of the Mega seeps is an extremely important for understanding Mega Seep gas roots and genesis. The deployed array of 4C self-popup nodes and active seismic source was used to solve this problem. This was the first 3D/4C seabed seismic survey performed in the Russian sector of the Arctic. The design of BB OBSs used for the current installation sustains more than one year of permanent recording and is based on previously developed self-popup OBS designed by the Russian Company GNS (OBS GNS). BB OBS has molecular electronic broad band seismometer (100 sec-50 Hz frequency range) while also preserves all new advanced features of GNS OBS. GNS OBS were employed for active seismic seabed study of mega seep structure. The presentation outlines the description of seabed instruments, survey details and results obtained during the performed marine studies. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042878 Jones, Eleanor Louise (University of Sheffield, Department of Geography, Sheffield, United Kingdom); Hodson, Andy; Thornton, Steve; Redeker, Kelly; Bak, Ebbe; Finster, Kai and Wynn, Peter. Biogeochemistry of a degrading ice-wedge polygon in the High Arctic [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-16214, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Rising air temperatures and melting ground ice in the High Arctic can cause marked changes in the hydrology and redox conditions in the active layer of ice-wedge polygons. As the ice wedges melt, the polygon rims collapse into the troughs, and the ice-wedge polygons degrade from low-centred to high-centred. This degradation drains water from the polygon centres, with implications for the soil biogeochemistry. We compared the active layer and upper permafrost (transient layer) of a high-centred polygon at Revneset, Svalbard, to ascertain the impact of ice-wedge polygon degradation on the biogeochemical processes. We highlight ice wedge polygon degradation to be associated with controlling methane release dynamics to the atmosphere. We obtained replicate cores from the high-centred polygon, extracted the porewaters of the cores, measured the aqueous and solid phase chemistry, and incubated the sediments anaerobically for 111 days. Our results revealed that both the active layer and the upper permafrost were rich in organic carbon (up to 38% of the dry sediment mass). This is characteristic of peat formed under anaerobic conditions, implying that these sediments were deposited in a stagnant, low-centred ice-wedge polygon. The upper permafrost sediments supported the prevalence of anaerobic conditions; methane concentrations in the porewaters were high (up to 560 mmol l-1), and the low concentrations of aqueous iron and sulphate coupled with higher pyrite concentrations were indicative of iron- and sulphate-reduction. Concentrations of carbon dioxide were relatively low (~2000 mmol l-1). This implies that the upper permafrost has preserved the stagnant, anaerobic conditions present during peat formation. In contrast, the active layer was hydrologically-flushed, with a low or fluctuating water table preventing the maintenance of a highly-reducing environment. Carbon dioxide concentrations were high (~4000 mmol l-1). The low concentrations of iron and sulphate, and high d34S values of sulphate, provide evidence for iron-reduction and sulphate-reduction. Methane was not detected in the active layer porewaters, indicating that conditions were not conducive to methanogenesis, or that methanotrophy predominated. Despite the absence of methane in the active layer porewaters, the thawed incubated upper permafrost and active layer sediments produced up to 15 nmol CH4 ml-1 day-1, suggesting that methanogenesis exceeded methanotrophy under anaerobic conditions. Permafrost thaw is predicted to cause poorly-drained, low-centred polygons to degrade to well-drained, high-centred polygons. Our biogeochemical data from a high-centred polygon active layer support decreased net methanogenesis upon degradation, with continued iron- and sulphate-reduction. This is in contrast to the reducing methanogenic environment preserved below in the upper permafrost. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042861 Kemna, Andreas (University of Bonn, Institute of Geosciences and Meteorology, Geophysics Section, Germany). Imaging the frozen subsurface; geoelectrical signatures for the diagnosis of thawing permafrost systems [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-18713, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The seemingly gradual thawing of permafrost regions due to global warming involves transitions in hydrologic and mechanical states of the subsurface that can lead to natural hazards such as rock slope failure and rapid increase in greenhouse gas emissions. Therefore, a better understanding of the couplings, dynamics and feedbacks of the underlying thermo-hydro-mechanical (THM) processes is of high societal interest. Due to the typically high spatiotemporal variability of the key state variables, i.e. temperature and ice versus (liquid) water content, in permafrost systems--on top of given geological heterogeneity--geophysical methods have been widely used in permafrost studies. In particular geoelectrical methods have been shown to provide pertinent information on subsurface state and, if applied in a time-lapse manner, process dynamics given their sensitivity to ice-water phase transitions. Electrical resistivity tomography (ERT) has almost developed into a routine imaging tool with numerous applications both in (sub)arctic and high-mountain permafrost. However, given the multiple petrophysical controls on resistivity, thermal state characterization based on resistivity alone suffers from inherent ambiguities and strongly relies on calibrated resistivity-temperature relationships. Moreover, resistivity is not directly sensitive to water flow, which due to advective heat transport is one of the key controls on the complex process dynamics in thawing permafrost systems. These limitations have more recently prompted interest in both combining data from different geophysical methods, e.g., resistivity and seismic data, to overcome ambiguities and improve resolution, as well as to explore the potential of complementary geoelectrical methods for permafrost characterization and monitoring. Among the latter, in particular the induced polarization (IP) and the self-potential (SP) methods hold promise. Results of first laboratory and field studies indicate that the spectral IP (SIP) response of frozen soils and rocks is strongly affected by the characteristic electrical polarization response of ice, suggesting potential of the SIP method for an improved imaging and quantification of ice content in permafrost regions. The SP method, on the other hand, offers direct sensitivity to (melt)water flow, which in thawing permafrost systems is typically characterized by complex spatiotemporal patterns. First SP monitoring attempts at a high-mountain permafrost site revealed strong SP signal variations correlated with the seasonal thawing and refreezing of the ground. Although promising, the use of both (S)IP and SP methods in permafrost environments, in particular for long-term monitoring, is technically challenging. The various successful field applications to date demonstrate the high potential of the different geoelectrical methods for characterizing and monitoring permafrost systems in a non-invasive manner with relatively high spatial and temporal resolution. The provided information on system state and dynamics offers new opportunities for an adequate parameterization and calibration of THM process models and, as a consequence, improved predictive understanding of cryospheric environments under the impact of global warming. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042872 Knoblauch, Christian (University of Hamburg, Institute of Soil Science, Hamburg, Germany); Schütt, Alexander and Pfeiffer, Eva-Maria. Carbon dioxide and methane production and release from eroding permafrost deposits of northeast Siberia [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-11184, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Permafrost thaw liberates formerly frozen organic carbon, which is decomposed by microorganisms to carbon dioxide (CO2) and methane (CH4). The release of these greenhouse gases (GHG) from soils may form a positive feedback to atmospheric CO2 and CH4 concentrations and accelerate climate change. Quantifying the contribution of CO2 and CH4 from permafrost, which is thawing at the bottom of the seasonal thaw layer (active layer) is challenging, since GHG fluxes from the surface of permafrost affected soils originate from both the active layer and the thawing permafrost below. Incubation studies with thawed permafrost material are used to quantify the potential formation of CO2 and CH4 after permafrost thaw. However, it is unclear how far the results from such laboratory studies, that do not consider a wide range of environmental parameters, represent GHG production under in situ conditions and how far the results from laboratory incubations may be related to in situ GHG fluxes. We here present data on CO2 and CH4 fluxes from non-vegetated thawing ice-rich permafrost deposits (Yedoma) in an active thaw slump at the banks of the Lena River, northeast Siberia. To evaluate how far data from laboratory studies may be used to calculate in situ fluxes, the same thawing permafrost material was incubated at constant temperature. Mean in situ CO2 fluxes in July ranged between 0.5 and 2.7 g CO2-C m-2 d-1, which is in the higher range of the very few reports of CO2 fluxes from Siberian Yedoma deposits. Methane fluxes were substantially lower with mean rates between 6.5-23.3 mg CH4-C m-2 d-1. However, while all sites were clear sources for CO2, three sites were CH4 neutral. The absence of CH4 emissions could be explained by CH4 oxidation in the unsaturated surface soil at one site and by the absence of CH4 production in two other sites, likely due to a lack of an active CH4 producing microbial community in the recently thawed permafrost. Methane represented less than 1% of total GHG fluxes. Based on the mean GHG fluxes, only about 1% of the thawed permafrost carbon was emitted over one thawing season as CH4 and CO2 into the atmosphere. Aerobic laboratory incubations substantially overestimated in situ CO2 fluxes by a factor of 1.3 to 6.4 (mean 3.9 1.9) while potential CO2 fluxes from anaerobic incubations were only 1.7 0.5 higher than under in situ conditions. In contrast, in situ CH4 fluxes were generally significantly higher than upscaled laboratory fluxes with a mean ratio between in situ and laboratory fluxes of 0.4 0.5. The low CH4 production in short term laboratory incubations is explained by a disturbance of the methanogenic community during sample preparation. The presented data indicate that despite relatively high GHG fluxes only a minor fraction of thawing permafrost carbon is decomposed to CO2 and CH4 in one thawing season and that data from short term incubations substantially overestimate in situ CO2 fluxes while underestimating CH4 production. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042843 Li Rongxing (Tongji University, College of Surveying and Geo-Informatics, Shanghai, China); Lu Ping; Hao Tong; Qiao Gang; Chen Lemin; Han Jiangping; Zheng Wuan; Ren Xiaochun; Meng Xianglian and Zhang Yinsheng. Initial result of large scale permafrost ALT estimation in Tibetan Plateau through InSAR and modeling techniques [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-12121, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Permafrost, as one of the major elements of cryosphere, is very sensitive to global climate change. Changes of permafrost not only affect regional and global water circulation, carbon deposit and climate warming, but also influence ground ecological, geophysical, and biogeochemical processes in cold regions. The permafrost region of the Tibetan Plateau is the highest and largest permafrost area in the middle and low latitudes of the world. This study aims to use InSAR and modelling techniques to monitor the active layer thickness (ALT) of permafrost in Tibetan Plateau. The surface seasonal and annual deformation patterns were analysed using data of the C-band Sentinel-1 and the L-band ALOS satellites and the processing techniques of D-InSAR, PS-InSAR and SBAS. On the other hand, several permafrost modelling methods, including the Stefan model and multi-layer GIPL2 model, were tested and their parameter sensitivities were analyzed. Large scale remote sensing products such as MODIS derived land surface temperatures (LSTs) and ground observations such as soil thermal parameters were combined to carry out the modelling process. Surface deformation and temperature profiles from the in-situ borehole monitoring along the 1956 km (including 550 km permafrost) Qinghai-Tibet railway, from Xining to Lhasa, is being used for validation. At this point, the estimation from the InSAR technique is in a general agreement with the in-situ measurements in the test region. Future work includes the extension of the model to fit the InSAR data, and the goal is to build an InSAR based permafrost ALT map of Tibet Plateau. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042884 Lu, Zhengyao (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Miller, Paul A.; Zhang, Qiong; Warlind, David; Nieradzik, Lars; Sjolte, Jesper; Li, Qiang and Smith, Benjamin. Vegetation migration and terrestrial carbon variation in past warm and cold climates [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-4740, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
About one-third of the current anthropogenic carbon dioxide (CO2) emissions are absorbed by the terrestrial biosphere. The uncertainty as to how this uptake might respond to projected future climate change can be constrained by knowledge of its behavior during glacial-interglacial cycles. Previous investigations of the vegetation and land carbon storage during the glacial period suggested a reduction of forests, productivity and biomass. Nevertheless, an evaluation based on a historical warm period is needed to better understand the implications for the future, and to understand the roles of temperature, moisture and CO2 concentration (pCO2) in the climate transition, which are currently still poorly understood. Consistent with paleo-vegetation and carbon cycle-related reconstructions, here we show the vegetation migration and terrestrial carbon variation in both past cold and warm climates, simulated by the Dynamic Global Vegetation Model LPJ-GUESS. We find that the vegetation extent is mainly determined by temperature anomalies, especially in a cold climate, while precipitation forcing is limited on a regional scale to shape vegetation patterns. The pCO2 change controls the global carbon balance with higher pCO2 linking to higher vegetation coverage, an enhanced terrestrial carbon sink and increased terrestrial carbon storage. Our results indicate a coherent transfer of carbon from ocean and permafrost/peat to biosphere and atmosphere from cold to warm climate scenarios. We further highlight the importance of expansion of the terrestrial ecosystem carbon stock in slowing atmospheric pCO2 growth. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042902 Maierhofer, Theresa (Technical University of Vienna, Vienna, Austria); Aigner, Lukas; Hilbich, Christin; Hauck, Christian and Flores-Orozco, Adrian. Spectral induced polarization for permafrost environments in the Swiss and Austrian Alps; improvement of data quality and first applications/results [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-16749, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Warming of permafrost regions with associated increase in the active layer thickness and decrease in ice content has been detected worldwide. The electrical resistivity tomography (ERT) method is already used to assess the spatial distribution of permafrost and its temporal changes. Especially ice-rich permafrost, commonly associated with a significant increase in the electrical resistivity, is detectable with ERT. However, in many cases the interpretation of the subsurface electrical resistivity is ambiguous, since air and ice exhibit similar electrical resistivity values. Therefore, additional information is needed to improve the quantification of the ice content within the subsurface. We therefore extend the investigation of electrical conduction mechanisms by taking into account the capacitive properties of the subsurface by means of induced polarization (IP) measurements. Moreover, IP measurements were conducted over a broad range of frequencies (in the so-called spectral IP (SIP)), to assess the frequency dependence of the IP. Eight representative permafrost sites distributed over the entire Swiss Alps and one site located in the Austrian Central Alps have been chosen to test the applicability of the method. The selected study areas are long-term permafrost monitoring sites and provide comprehensive geophysical data and temperatures for validation. The sites range from rock glaciers and talus slopes with high ice content to bedrock permafrost with lower ice contents. Here we focus on IP imaging results for data collected at 1 Hz for all field sites. Additionally, we present SIP imaging results collected over the frequency range from 0.1-225 Hz for a specific site in the Valais Alps, the Lapires site, a large north-facing talus slope at 2600 m altitude. For the quantification of data error, measurements were conducted as normal and reciprocal pairs. We also present field techniques used to enhance data quality at high frequencies through the deployment of shielded and separated cables. Our results show that SIP anomalies agree with ice-rich permafrost as delineated from borehole data. Thus, spatial variations in the SIP response might permit to distinguish between ice- and air-filled pores, improving the interpretation of ERT. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042896 Manasypov, Rinat (Tomsk State University, BIO-GEO-CLIM Laboratory, Tomsk, Russian Federation); Pokrovsky, Oleg and Shirokova, Liudmila. Latitudinal gradient of carbon, macro- and microelements in components of thermokarst lake ecosystems, western Siberia [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-961, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Thermokarst lakes in the permafrost zone have an important biospheric climate regulation function and simultaneously serve as indicators of current climate changes and possible increased anthropogenic load. Therefore, a detailed and comprehensive assessment of the biogeochemical status of the components (bottom sediments-lake water-macrophytes) of the thermokarst lake ecosystems of Western Siberia, and their response to current environmental changes and anthropogenic impacts, as well as interpretation of the role of macrophytes as markers of these processes are an important scientific goal. In this study, the model dominant macrophytes were taken (Menyanthes trifoliata L., Carex aquatilis Wahlenb s. str.) for a study of their element composition. Samples were treated in a four-step chemical digestion procedure (full dissolution via acid attack) for major and trace element analysis. Element concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). Our results show that the total concentrations of chemical elements in macrophytes growing in the continuous permafrost zone (northern part) are higher than in the discontinuous permafrost zone (middle part) and increasing in the isolated permafrost zone (southern part). This can be due to two factors: 1) the proximity of the Kara Sea, the influence of marine aerosols; 2) the difference in substrates, namely, the decrease in the thickness of the peat deposit from the south to the north of Western Siberia. The mineral horizon in the tundra zone lies closer to the surface and to the seasonal-thawed layer, whereby more elements can be absorbed by plant roots. Support from the RSF (RNF) grant No. 17-77-10067 "Balance of carbon, macro- and microelements in conjugate components of thermokarst lake ecosystems in the Arctic zone of the Russian Federation (Western Siberia)". [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042883 Margalef, Olga (Center for Ecological Research and Forestry Application (CREAF), Cerdanyola del Valles, Spain); Grau, Oriol; Joosten, Hans; Fernàndez, Pere Roc; Dorrepaal, Ellen; Richter, Andreas; Checa, Eva; Girbau, Marta; Laguna, Clara; Bogdanovic, Ivana; Canarini, Alberto; Sardans, Jordi and Peñuelas, Josep. Irreversible changes in phosphorus cycling driven by permafrost thaw in subarctic palsa mires [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13568, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Phosphorus (P) is an essential element for life and limits productivity in many terrestrial and aquatic ecosystems. Histosols contain a large amount of P because of their high content of organic matter and effective adsorption processes. Climate warming promotes the degradation of permafrost and increases decomposition leading to unprecedented geochemical changes in Carbon (C) and Nitrogen (N) cycles. To assess the effect of permafrost thaw on P cycling, we determined available P, Hedley P fractions and phosphatase activity across a thawing gradient in a palsa mire complex at Stordalen (Abisko, 68°N, Sweden). We analysed three site types in a space-for-time approach (palsa, transition zone and collapsed palsa) at four different depths (5-10, 40-45, 70-75 and 95-100 cm). Available or relatively labile P were higher in surface samples compared to deep peat in the palsa and collapsed sites. The main P fraction of these samples was organic P and P bound to Iron (Fe) and Aluminum (Al) (NaOH-Porg), which made up between 40 and 70% of total P. The collapsed palsa sites had a lower proportion of P in these fractions and higher organic and inorganic available P, as well as phosphatase activity--especially in surface samples--suggesting that increased temperature, microbial activity and redox changes contribute to transforming Fe-Al bound P into other forms. Total P (TP) in deep layers (>50 cm) is dramatically reduced (between 15 and 30%) after permafrost thaw. In contrast, in surface samples (5-10 cm) TP increased by 60% suggesting an important change in the depth profile of this nutrient related to permafrost disappearance. The described changes indicate a major increase in P availability for plant and microbes after permafrost thaw, and a lower storage capacity for P in deep peat layers. P mobilization in subarctic peatlands after permafrost thaw may thus result in lower surface N/P ratios, and changes in ecosystem productivity and C fixing capacity. Permafrost thaw and associated changes in hydrology and underground circulation in areas with discontinuous permafrost may play an important role in the release of P and its interaction with C, N, Al and Fe cycles. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042850 Martens, Jannik (Stockholm University, Department of Environmental Science and Analytical Chemistry (ACES), Sweden); Wild, Birgit; Andersson, August; Semiletov, Igor; Shakhova, Natalia; Dudarev, Oleg V.; Kosmach, Denis; Charkin, Alexander; Romankevich, Evgeny; Vetrov, Alexander; Lobkovsky, Leopold; Belyaev, Nikolay and Gustafsson, Orjan. The Circum-Arctic Shelf Sediment CArbon DatabasE (CASSCADE); first analysis of spatial patterns and fluxes of terrestrial carbon input to the Arctic Ocean [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-5454, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The circum-Arctic shelves are the main receptors of sediments and organic carbon (OC) from the surrounding Arctic permafrost region. Arctic rivers discharge about 33 Tg OC to the Arctic Ocean every year. Substantial amounts of terrigenous OC (14 Tg) are also annually released from Arctic permafrost by coastal erosion, yet with much larger uncertainties. While a large fraction of terrigenous OC in the Arctic Ocean is degraded to CO2 and CH4, a yet poorly constrained amount is re-buried in shelf sediments. The first Circum-Arctic Shelf Sediment CArbon DatabasE (CASSCADE)--an international collaboration compiling data on OC concentrations, isotopes (d13C, D14C) and sediment fluxes from the published literature as well as from yet unpublished records--permits to quantify the patterns of large-scale terrigenous OC releases to the Arctic Ocean. The current CASSCADE version includes 4,300 values of OC concentrations, ~1,500 d13C values and 52 stations with known sediment accumulation rates. A preliminary estimate is that the Circum-Arctic shelf sediments of the Beaufort, Chukchi, East Siberian, Laptev, Kara and Barents Seas sequester about 30 Tg terrigenous OC per year. An overwhelming part (83%) of this input occurs on the East Siberian Arctic Shelf (ESAS), likely reflecting a combination of input from its large rivers and erosion along the coastlines of the Laptev and East Siberian Seas. Other areas with more stable coasts yield significantly lower shares (e.g. Kara Sea only 3%) despite large river discharges. Compared to estimates of the influx from Arctic rivers and coastal erosion, this inverse receptor approach implies that about 57% of the terrigenous OC is re-buried and 43% of that OC is degraded, which translates into an atmospheric flux of 20 Tg per year. Climate change is expected to cause large-scale permafrost thaw and increase the release of OC to the Arctic Ocean in the near future, a feedback that could amplify both land-ocean transfer of OC and the emission of climate-susceptible greenhouse gases [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042897 Meyer, Rena (University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark); Hoyer, Anne-Sophie; Sonnenborg, Torben O. and Piotrowski, Jan A. Subglacial groundwater flow under the Scandinavian ice sheet in southern Denmark during the Weichselian glaciation and its impact on ice-movement dynamics [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13335, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Groundwater is the main source of drinking water supply in Denmark. In southern Denmark, deep Miocene aquifers are increasingly considered as a resource of pristine high quality groundwater. Groundwater in these aquifers is up to several thousands of years old and the recharge conditions experienced significant changes in the past. Understanding the groundwater history is important to ensure sustainable groundwater use and protection from potential contamination. In this study we investigate large-scale changes in the groundwater flow system in southern Denmark during the Quaternary glacial/interglacial cycles with focus on the last (Weichselian) glaciation. Using a finite-difference groundwater flow model (MODFLOW) and a detailed geological representation we show that during the Weichselian glaciation groundwater flow patterns, directions and depths experienced a full reorganization in relation to the interglacial (modern) time as a result of high potentiometric heads imposed by the ice sheet. Of special interest are the feedback mechanisms between the groundwater flow and the ice sheet dynamics. Our simulations show that the drainage capacity of the ice-sheet bed was insufficient to evacuate all the meltwater from the glacier sole as groundwater flow, both under permafrost and no-permafrost conditions. This suggests a widespread decoupling of the ice sheet from the bed and high ice movement velocities by enhanced basal sliding on a layer of pressurized meltwater, which is in turn consistent with the presence of fast-flowing ice streams along the southern fringe of the Scandinavian Ice Sheet during the Last Glacial Maximum. To stabilize the ice sheet, the glacial system generated a system of deep tunnel valleys that drained the excess meltwater to the ice fore-field. Our study illustrates the advantages of a coupled palaeo-hydrological and glacio-geological approach in deciphering the behavior of past ice sheets and their impact on shaping the Earth's surface. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042903 Mollaret, Coline (University of Fribourg, Department of Geosciences, Fribourg, Switzerland); Wagner, Florian; Hilbich, Christin and Hauck, Christian. Alpine permafrost field applications of a petrophysical joint inversion of refraction seismic and electrical resistivity data to image the subsurface ice content [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-14974, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Electrical Resistivity Tomography (ERT) is one of the most commonly used geophysical methods for permafrost monitoring. Ice can be well distinguished from liquid water due to its different electrical properties. However, this method has also limitations as it requires to solve an inverse problem which is usually underdetermined and has no unique solution. To reduce the uncertainties and improve the interpretability of the inversion model, geophysical methods are usually combined with ground truth measurements and/or other geophysical methods. High mountain regions are often characterised by unsaturated and frozen ground conditions. The pore space in the subsurface can therefore be filled with air, ice and/or liquid water. But ice and air are both materials characterized by very high electrical resistivity and are consequently hard to distinguish using ERT alone. Ice can, however, be well distinguished from air from their P-wave velocity properties (3500 m/s vs 330 m/s). This is why Refraction Seismic Tomography (RST) is a suitable supplementary geophysical method to be combined with ERT to assess ice or liquid water content and their respective spatio-temporal variabilities. To fully exploit two geophysical datasets for improvement of the reliability of the results and reduce the occurrence of inversion artefacts, several possibilities to combine the independent data sets exist. Wagner et al. (2019) successfully developed a petrophysical joint inversion scheme to determine the liquid water, ice, air and rock contents using the general framework for joint inversions provided in pyGIMLI (Rucker et al., 2017). Synthetic data sets have been used to validate the general applicability of the approach. In this contribution, we apply this joint inversion scheme to several field data sets, which span a large range of conditions from ice-rich permafrost (rock glacier) to ice-poor permafrost sites. In a first step, we use the petrophysical equations (Archie's law and time-averaging equation) employed by Hauck et al. (2011) in the so-called 4-phase model (4PM). The joint inversion results demonstrate the possibility to estimate a plausible porosity, in addition to air, water and ice contents. In a second step, we extend the joint inversion approach to other petrophysical equations, better representing the diversity of field site substrates. The sensitivities of the different parameters are analysed and the calculated water and ice contents are discussed in relation with the active layer thickness and temperature data set, when available. Hauck, C., Bottcher, M., & Maurer, H., 2011: A new model for estimating subsurface ice content based on combined electrical and seismic datasets. The Cryosphere, 5, 453-468. Rucker, C., Gunther, T., & Wagner, F. M., 2017: pyGIMLi: An open-source library for modelling and inversion in geophysics. Computers and Geosciences, 109, 106-123. Wagner, F., Mollaret, C., Gunther, T., Kemna, A., & Hauck, C., 2019: Quantitative imaging of permafrost through petrophysical joint inversion of seismic refraction and electrical resistivity data, Geophysical Journal International, submitted. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042857 Morino, Costanza (Université de Nantes, Laboratoire de Planétologie et Géodynamique, CNRS UMR6112, Nantes, France); Conway, Susan J.; Balme, Matthew R.; Saemundsson, Thorsteinn; Helgason, Jon Kristinn; Jordan, Colm; Hillier, John and Argles, Tom. A morphometric approach to reveal the effects of ground-ice thaw on rapid mass movements in northern Iceland [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-14845, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Permafrost degradation is one of the main controlling factors of slope instabilities in glacial and periglacial environments (e.g., Gruber and Haeberli, 2007). In permafrost terrains, ground ice can occur in pores, cavities, voids in soils or rocks, and its thaw can cause slope failures. A plethora of studies exists on the destabilisation of bedrock slopes due to permafrost degradation (e.g., Harris et al., 2001; Magnin et al., 2015). However, the role of thawing ground ice in conditioning and controlling the dynamics of rapid mass movements involving loose deposits is not well constrained, and has been rarely explored through geomorphometric analysis. In this research, we investigate two landslides induced by ground-ice thaw in Iceland, whose source materials comprised ice-cemented talus deposits. We apply quantitative terrain analysis using high-resolution DEMs to describe and quantify the morphometric characteristics of these landslides. Our morphometric approach allows us to show that different dynamic processes were involved during both failures due to the presence of ground ice. This caused the movement to evolve during the failure event, changing the mobility and trajectories of the landslides. Improving our knowledge on this type of landslides through morphometric analysis is important, as it can aid in assessing their hazard and in predicting similar rapid mass movements in comparable settings. References: Gruber, S. and Haeberli, W., 2007. Permafrost in steep bedrock slopes and its temperature-related destabilization following climate change. Journal of Geophysical Research: Earth Surface, 112(F2). Harris, C., Davies, M. C. and Etzelmuller, B., 2001. The assessment of potential geotechnical hazards associated with mountain permafrost in a warming global climate. Permafrost and Periglacial Processes, 12(1), 145-156. Magnin, F., Deline, P., Ravanel, L., Noetzli, J. and Pogliotti, P., 2015. Thermal characteristics of permafrost in the steep alpine rock walls of the Aiguille du Midi (Mont Blanc Massif, 3842 m asl). The Cryosphere, 9(1), 109-121. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042856 Muskett, Reginald (University of Alaska Fairbanks, Geophysical Institute, Fairbanks). Measuring l-frequency polarimetric SAR volume scattering penetration on lowland tundra on Arctic periglacial and permafrost terrains [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-3714, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Geodetic methods to measure centimeter to millimeter-scale changes using aircraft- and spacecraft deployed Synthetic Aperture RADAR (SAR) cannot ignore volume scattering. Backscatter and coherence at L-frequency and others possess both surface and volumetric scattering. On lowland tundra underlain by permafrost, volume scattering is the dominant backscatter mechanism. Measurement of the L-frequency penetration depth for evaluation of mass balance (i.e. gain or loss and transport) through permafrost thaw-degradation with erosion is necessary. UAVSAR L-frequency Full Polarimetry Cross-Pole HHVV (polarization rotation, i.e. HH send and VV receive) confirms the dominance of volume scattering on lowland tundra (RADAR-soft target, low bulk density) whereas surface scattering (HHHH or VVVV, no rotation) dominates on river channel deposits, rock outcrops and metal objects (RADAR-hard targets, high density). HHHH, HHVV and VVVV combined in 3-Channels illustrates that the sigma-naught polarizations are coming from the ground surface and subsurface (snow, above ground vegetation, root zone and soil volumes). With full Polarimetry-SAR information on the depth (i.e. depths) of penetration are within the two-way travel time polarizations. Validating and verifying L-frequency multi-polarization volume scattering penetration depth on lowland tundra calls for a new field validation experiment. Knowing this parameter is of vital importance as a reference, i.e. a benchmark, in near-term and decadal-term monitoring of the mass balance of carbon, soil and water. Reference: Muskett, R. R. (2018), To Measure the Changing Relief of Arctic Rivers: A Synthetic Aperture RADAR Experiment in Alaska, Journal of Geoscience and Environment Protection, 6 (9), 207-222. doi: 10.4236/gep.2018.69016. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042864 Obremska, Milena (Polish Academy of Science, Institute of Geological Science, Warsaw, Poland); Slowinski, Michal; Avirmed, Dashtseren; Adiya, Saruulzaya; Lucow, Dominika; Mroczkowska, Agnieszka; Lamentowicz, Mariusz and Szczucinski, Witold. Vegetation, permafrost and climate variability; 1600 years of fire history in North Eastern Mongolia [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-17415, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
We are faced with negative changes concerning social and the natural environment induced the degradation of permafrost, which is related to recent global warming. Thawing permafrost affects the hydrological cycle, geomorphological processes, as well as vegetation changes. Mongolia territory is by about 63% within permafrost zone. Therefore, it is important to understand the dynamic of the process and controlling factors responsible for the permafrost degradation. We studied two peatlands Khar Zurkhnii Khukh Nuur in the Khentii mountain range (NE Mongolia). This part of Mongolia is characterized by the occurrence of the forest-steppe mosaic in the area of discontinuous permafrost. We aimed to reconstruct dependence between vegetation composition, fire regime shift and timing of permafrost degradation during the last 1600 years from two peat archive. For this purpose, we worked on peat archive and used multi-proxy analysis (pollen, plant macrofossils, testate amoebae, Cladocera, macro-charcoal, and geochemistry). Two profiles: 36-cm (KH-1) and 55-cm (KH-2) have been extracted from two nearby peatlands, which are only 1 km away. Chronology of the KH-1 core was based on 6 AMS 14C dates, 137Cs, and 210Pb analyses, while the second core KH-2 was based on 11 AMS 14C dates. Respectively, the core KH-1 covers the last 250 years and the core KH-2 covers the last 1600 years. Our first results indicate a strong relationship between degradation permafrost, droughts, vegetation forest-steppe mosaic composition and fire regime shifts, which caused intensified erosion in the catchment. Palaeoecological and geochemical data allowed tracing the dynamics of degradation permafrost and impact of fire regime shifts on the ecosystems, both triggered by recent and past climate changes. The research was funded by the National Science Centre (Poland) - grants 2017/01/X/ST10/01216 [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042870 Pointner, Georg (b.geos GmbH, Korneuburg, Austria); Bartsch, Annett; Widhalm, Barbara; Hugelius, Gustaf and Wagner, Julia. Exploitation of Sentinel satellite data to characterize Arctic river catchments [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13504, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Across broad spatial and temporal scales, riverine and coastal dissolved organic carbon (DOC) dynamics are linked to the characteristics of river catchments (e.g. its soils and sediments, topography, vegetation and permafrost). Datasets to support spatial analyses, to provide characteristics of river catchments across the Arctic are required. C-band SAR has shown to be of value for identifying wetlands, shallow water bodies, soil organic carbon content in the upper meter, snow melt patterns and recently also vegetation height in tundra. With Sentinel-1 which consists of two twin satellites, it is possible to monitor Arctic river catchments and their properties with high temporal and spatial resolutions. Several Arctic river catchments have been selected and compared, grouped by permafrost and landcover characteristics exploiting the ESA DUE GlobPermafrost Permafrost Information System (part of APGC - Arctic Permafrost Geospatial Data Centre hosted by the Alfred Wegener Institute for Polar Research) in a first step. In combination with in situ observation, algorithms for the extraction of spatio-temporal properties of Arctic river catchments were developed. This includes transfer of methods developed for the predecessor ENVISAT ASAR to Sentinel-1. To facilitate cross-disciplinary analyses, the data will be eventually combined with GIS-data on human settlements and infrastructure within the HORIZON2020 project Nunataryuk (led by AWI). [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042873 Rethemeyer, Janet (University of Cologne, Geology and Mineralogy, Cologne, Germany); Wischhöfer, Philipp; Melchert, Jan Olaf; Stolz, Alexander; Dewald, Alfred and Knoblauch, Christian. Ancient carbon release from degrading, ice-rich permafrost deposits in NE Siberia; evidence from radiocarbon analysis of CO2 [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-17425, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Deep permafrost deposits that developed during the last glacial period and early Holocene in unglaciated lowlands of the circum-arctic region have been a carbon sink for millennia. This significant carbon pool is now being degraded because of increasing ground temperatures that particularly affect the ice-rich sediments in the Yedoma domain, also called ice complex deposits. The loess-like Yedoma deposits that still cover an area of about 1 million km2 contain large syngenetic ice-wedges resulting in very high ground-ice contents (50-80% of the ground volume). This makes them particularly prone to disturbances such as thermokarst and thermo-erosion processes causing ground subsidence and sediment relocations processes by which the previously frozen organic matter is exposed to microbial decomposition. The complexity of processes and changes taking place in the thermokarst landscape complicates the prediction of greenhouse gas emissions resulting from the mineralization of the organic carbon (OC) stored in Yedoma deposits. To investigated the degradability of OC in thermokarst-affected Yedoma deposits, we designed a model study on a retrogressive thaw slump in the Lena River Delta (NE Siberia). The thawing of the ice wedges in the Yedoma exposed the sedimentary OC in the form of thaw mounds and mixes ancient and younger sediments, which contain ancient and younger organic matter of different age and stage of degradation. Using molecular sieves coupled with respiration chambers as well as depth- samplers, we collected CO2 at different locations on the thaw slump for radiocarbon analysis providing information on different carbon sources (ancient, young) released from the different study sites. Additionally, we incubated sediment samples to identify substrates released preferentially. Higher 14C contents of the bulk OC in the near-surface sediment compared to the underlying sediment in two thaw mounds indicated the input of younger substrates potentially derived from younger sedimentary units or leachate of the ice wedges. Likewise, younger layers at another site suggest admixtures of Holocene active-layer material. These younger substrates are preferentially mineralized resulting in relatively high 14C contents of the CO2 collected with respirations chambers compared to bulk OC. Using depth samplers installed near the still frozen ground (50-60 cm) we collected very old CO2, which has similar 14C concentrations like the bulk sedimentary OC, indicating that the ancient (up to 30,000 yr BP old) Yedoma OC is mineralized if no younger substrates are available. This observation is confirmed by first 14CO2 results of incubation experiments. Variable 14CO2 results for three successive years further suggest that considerable changes are taking place in the sediment due to the rapid erosion of the thaw slump causing continuous sediment displacement, the formation of cracks, and the development of a sparse vegetation on the bare sediments. This in turn most probably caused changes in soil temperature, moisture, oxygen and nutrient contents (to be analysed) mirrored by younger CO2 emissions at some sites. Overall the 14CO2 results reveal the complexity of the different deposits and of effects that may take place during their thawing complicating the prediction of future greenhouse gas releases from thawing Yedoma. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042874 Richter, Lea (University of Massachusetts Lowell, Earth, Environmental, and Atmospheric Studies, LOWELL, Lowell, MA); Obrist, Daniel and Yang, Yu. Temperature dependency of methanotrophs in Arctic tundra soils [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-17812, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
After carbon dioxide (CO2), atmospheric methane (CH4) is the most relevant greenhouse gas affected by anthropogenic activities globally. Methane is the most abundant organic gas in the atmosphere and has a global warming potential that is 25 times that of CO2. Climate warming in the arctic is occurring at an unprecedented rate, close to double that of lower latitudes, potentially increasing mineralization of organic carbon stored in soils and thawing permafrost and possibly enhancing CH4 production by methanogenic activity. On the other hand, there also is indication of enhanced CH4 consumption (methanotrophic activity), in particular drained upland soils that has the potential to offset CH4 production and even lead to soils to be net sinks of atmospheric CH4. Methanogenic and methanotrophic microorganisms are ubiquitous throughout world soils, and both organisms have well-documented correlations of activity with soil temperature and moisture. However, temperature and moisture responses of methanotrophs are poorly constrained in arctic soils, in particular near freezing and thawing temperatures that characterize arctic soils during much of the year. This study assessed CH4 production and consumption rates, along with the production of CO2, in laboratory experiments using high-resolution flux chambers in arctic tundra soils between temperatures from -5°C to 5°C. Results show that CO2 production strongly increased with temperature, with a strong step increases above freezing temperatures. CO2 production showed a pronounced hysteresis effect whereby production was higher during decreasing temperatures (i.e. during freezing) compared to the same temperatures during thawing of soils. For methane, thawing soils showed some methane production (methanogenesis) upon thawing around the freezing points, possibly owed to anoxic microsites in the soils. Thereafter, soils consistently turned into net CH4 sinks, with higher net uptake during re-freezing of soils compared to the same temperatures upon thawing. Methanotrophy was observed at temperatures as low as -2°C after which fluxes reached near-zero. Both upper and deeper soils (A and B horizons) were predominantly CH4 sinks under oxic condition, and A-Horizon soils showed much larger fluxes, both of CH4 uptake and CO2 production, compared to B-Horizon soils, by about a factor 10, consistent with higher organic carbon contents. This study shows sensitive thresholds for CO2 production and CH4 consumption in Arctic soils near freezing temperatures, with pronounced hysteresis effects of fluxes during freezing and thawing processes. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042851 Rutkowski, Clara (University of Salzburg, Department of Geography and Geology, Salzburg, Austria); Strauss, Jens; Lenz, Josefine; Mothes, Sibylle and Lang, Andreas. Mercury in deep ice-rich permafrost deposits of Siberia [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-4284, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The ice-rich permafrost in Siberia ('Yedoma') is extra prone to thawing due to Arctic warming resulting in an increased sediment input from coastal shorelines and river floodplains to the Laptev Sea. Freeze-locked deposits including hazardous heavy metals are now entering the Arctic Ocean. Shallow Arctic soil layers often show high levels of mercury (Hg). In this study, we determined Hg concentrations from various deposits in Siberia's deep permafrost soil. We explored linkages between sediment properties and the Hg enrichment in order to assess a first deep Hg inventory in Pleistocene permafrost down to 36 m below surface. Sediment material from seven sites of different permafrost degradation states on Bykovsky Peninsula (Northern Yakutia) and in the Yukechi Alas region (Central Yakutia) were analysed for Hg content using a Direct Mercury Analyzer (DMA-80), based on photometric absorption. Total carbon and organic carbon and grain size distribution were investigated as sediment property parameters. First results reveal a Hg concentration from 0.86 to 34.52 g/kg and a significant correlation of Hg to organic and inorganic carbon. Moreover, Hg concentrations are higher in the sandier sediment of the North-Yakutian Bykovsky Peninsula than in the siltier sediment of the South-Yakutian Yukechi Alas, which is counter intuitive and may well be explained by proximity to the ocean. This case study showed that the deep permafrost sediments, frozen since millennia, contain Hg. Even though it might not be an alarming amount it could re-enter the recent biogeochemical cycles after thaw with ongoing Arctic warming. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042898 Smith, Will D. (Newcastle University, Department of Geography, Newcastle upon Tyne, United Kingdom) and Dunning, Stuart. Automatic identification of supraglacial debris expansion using Google Earth engine; a new tool for glacier monitoring [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-1162, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
As glacial environments lose ice mass due to increasing atmospheric temperatures, more bedrock is exposed with deceasing binding permafrost. Debris supply rates increase and large failures (debatably) become more commonplace. This suite of increased subaerial supply, along with thinning and frontal retreat allowing englacial debris emergence, results in expanding extents of supraglacial debris cover. These debris additions affect glacial dynamics through melt regime modification, and potential chemical and physical changes to supraglacial, englacial and subglacial hydrology. Here we present a first tool that identifies supraglacial debris additions and debris cover expansion through efficient cloud based processing. We use the Google Earth Engine platform to quantify supraglacial debris expansion, utilising the large collection of optical satellite imagery from Landsat 4, 5, 7, and 8. This array of data allows investigation of debris expansion and its slope v's glaciological causes from 1982 until the present day to be undertaken. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042880 Startsev, Viktor (Russian Academy of Sciences, Siberian Branch, Institute of Biology of Komi Scientific Centre, Syktyvkar, Russian Federation) and Dymov, Alexey. Organic matter of main soils of the subpolar Ural [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-493, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The Subpolar Ural is the southern border of the permafrost spread in the European North East of Russia. Soil is one of the most important components of the functioning of ecosystems, so the study of various aspects of soil cover is an important task of soil science. Many experts highlight the special role of organic matter (OM) in the evolution of soils formed in mountain regions. Amphiphilic properties of soil organic matter (SOM) characterize its ability to interact with water, migration opportunities. The content and nature of the carbon distribution of water-soluble organic matter affects the formation of the chemical composition of soils, participates in the cycles of transfer of various nutrients. The object of the study was the soil formed in the Northern part of the national park "Yugyd va", the Kozhim river basin (Subpolar Urals). Were investigated soils of mountain-forest, subalpine, alpine tundra vegetation belts and soils with permafrost icy rocks. A total of 16 soil pits were studied. The study of soil organic matter was performed using the method of densimetric fractionation, chromatography of hydrophobic interaction and assessment of the content of water-soluble organic matter. The analysis of densimetric fractions of organic matter soils of the Subpolar Urals revealed that the basis of organic matter is a heavy organomineral HF>1.6 fraction (56-99% mass.). However, the main pool of organic carbon is found in light fractions of organic matter. Maximum concentrations of carbon are characterized by a light fraction of OPOM<1.6 (45%). It is shown that occluded organic matter is better preserved than free plant residues. This fact may be a characteristic feature of the soils of the northern mountainous regions. The conducted research by the method of hydrophobic interaction chromatography revealed that soils formed in different high-altitude belts have differences in the amphiphilicity of organic matter. In the soils of the subalpine belt is dominated by the hydrophilic fraction. Soils of mountain-forest, alpine tundra belts and soils with permafrost icy rocks are characterized by the maximum content of hydrophobic fractions. In the studied soils, hydrophilic compounds of the first fraction (aliphatic compounds) predominate in the composition of labile soil organic matter) and fifth fraction organics (combined with Fe and Al). As a result of the research it was found that the maximum carbon content of water-soluble organic compounds characterized by organic horizons. The largest carbon content of water-soluble organic matter in the litter is characterized by the soils of the subalpine belt (up to 17.3 mg/g), in mineral horizons--soils of the alpine tundra belt (up to 2.2 mg/g). The nitrogen content of water-soluble compounds has similar regularities. Analysis of the fraction of carbon of water-soluble organic matter from total carbon showed that in the soils of the soils with permafrost icy rocks there is an increase in water-soluble organic compounds in the lower horizons. The research was carried out with the financial support of the project RFBR No. 18-34-00618. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042867 Teshebaeva, Kanayim (Free University of Amsterdam, Amsterdam, Netherlands) and van Huissteden, Ko. Quantifying shallow and deep permafrost changes from Sentinel-1 data [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-12110, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Widespread thawing of permafrost in the northern Eurasian continent cause severe problems for infrastructure and global climate. We test the potential of Sentinel-1 SAR imagery to enhance detection of permafrost surface changes in the Siberian lowlands of the northern Eurasian continent at Kytalyk research station site and Yamal peninsula site. We used InSAR time-series technique to detect seasonal surface movements related to permafrost active layer changes. Preliminary InSAR results for Yamal test site show up to 60 mm/yr of seasonal active layers changes and linked to anthropogenic impact on the permafrost surface changes in the area. These changes are due to ongoing gas and oil exploration of the Yamal peninsula. At Kytalyk test site we derived up to 20 mm/yr of seasonal active layer changes. These seasonal ground displacement patterns align well with lithology and reflect the thaw of yedoma plateaus. These results suggest that the ice-rich yedoma sediments may be subject to much larger volume loss by thaw. There is abundant evidence of small-scale runoff channels and erosion on many yedoma surfaces by which the surface subsides. The eroded material is deposited as slope material on the side slopes of the plateaus and possibly slow creep of the ice-rich material occurs. This study shows the potential of Sentinel-1 data in detection of seasonal permafrost surface changes in Siberian lowlands. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042845 Thomas, Zoe (University of New South Wales, Australia); Jones, Richard; Turney, Chris; Bradshaw, Corey; Bird, Michael I.; Fogwill, Christopher; Golledge, Nicholas; Palmer, Jonathan; Kershaw, Peter; Wilmshurst, Janet; Muscheler, Raimund and Cox, Peter. Tipping cascades in polar regions drove global change during early last interglacial warming [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-14095, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Irreversible shifts of large-scale components of the Earth system (so-called 'tipping elements') are a concern for pace and severity of future climate change. Positive feedbacks within the climate system can amplify change, with interactions between certain sub-systems including sea ice, permafrost, boreal forests, and ice sheets and sea level, playing important roles in the trajectories of the high latitudes in particular. Since instrumental records do not capture the full range of past or projected climate scenarios, natural archives from warmer periods in the past can be used to identify responses to forcing and modes of climate variability, which provides a comparison to long-term projected simulations. The Last Interglacial (129-116 kyr BP)--the warmest interglacial of the last 800 kyr--was the most recent period during which global temperatures were close to 21st Century projections; this period therefore represents a potentially useful analogue for future change. Compared with pre-industrial times, average global temperatures were up to 2°C higher, with warming amplified over polar latitudes and comparable atmospheric concentrations of greenhouse gases. While models of Last Interglacial climate tend to agree with available proxy records in terms of the direction of change, they largely underestimate the magnitude; regional maximum Last Interglacial summer temperature anomalies in the high Arctic range up to 8°C warmer than present day. Quantifying and documenting qualitative regional changes from climate and environmental records during the Last Interglacial can potentially offer insights into future mechanisms and feedbacks that could have global impacts. A potentially important aspect is the inter-connection among various Earth-system feedbacks that may result in 'domino dynamics', where the tipping of one sub-system into a different state can trigger the collapse of an inter-connected sub-system. Here we synthesise the nature and timing of selected high-latitude Last Interglacial tipping elements including sea ice, boreal forest extent, permafrost, ocean circulation, and ice sheets/sea level, focussing on the timescale of onset and recovery and reviewing the thresholds and feedbacks that likely operated at that time. Despite chronological uncertainties, we find that the palaeoclimate evidence indicates early high latitude warming and impacts throughout the Earth System, with slow recovery (back to levels prior to the Last Interglacial) on the order of millennia. Our synthesis demonstrates the high sensitivity of these tipping elements to climate warming, and suggests that immediate-future climates are precariously susceptible to analogous tipping cascades. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042858 Volovinsky, Innokenty (Lomonosov Moscow State University, Moscow, Russian Federation); Arkhipova, Maria; Victorov, Alexey; Orlov, Timofey and Zverev, Andrey. The stochastic modeling of the thermokarst dynamics during the gas pipeline operation within a frozen peatlands (Nadym region case study) [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-2704, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The widespread development of pipeline transport within the permafrost zone entails the development of risks  and makes us look for new methods for assessing the dangers and natural risk. The aim of the present research is a probabilistic modeling and empirical verification of anthropogenically-initiated thermokarst processes models in a pipeline stripe. We developed stochastic model for the homogenous conditions , . The model assumptions are: 1. The thermokarst depressions appear in a limited strip adjacent to the linear structure; the emergence of thermokarst depressions occurs independently of each other. 2. The initiated thermokarst in the zone of the linear structure can be approximately considered as an ellipse with the ratio of the semiaxes lengths. 3. Due to the thermal abrasion effect, the growth of the linear dimensions of thermokarst depressions occurs independently of other depressions, and it is directly proportional to the density of heat loss. Implications of the model: - the distribution of distances between the centers of thermokarst depressions along the pipeline must fit to an exponential distribution. - the distribution of the depression areas and the distribution of the projections of the depressions on the pipeline and the perpendicular to the pipeline must fit to a lognormal distribution. We chose two parts of gas pipeline in Western Siberia, near Nadym city. The first part of pipeline is located at a convex peat bog-moss-lichen peatlands, the second one is small topsy shrub-sphagnum-lichen peatlands. The active layer thickness is 0.5 to 2 meters thick. To determine thermokarst depressions we use a satellite image WorldWiew 2 (06.07.2018) and field researches. There were done detecting thermokarst depressions and fitting projections to pipeline and perpendicular to pipeline to empirical distribution. For the most of samples, we have confirmed the initial hypothesis that the distributions of the distances between the centers of the lakes in the projection on the linear structure corresponded to the exponential distribution. The areas of the lakes and the lengths of the projections on the linear structure and perpendicular to the linear structure were confirmed to be lognormal at a significance level of 0.99. The resulting model makes it possible to proceed to solving the problem of probabilistic risk assessment of damage to a linear structure with foci of initiated thermokarst. The research was held with the support of RGO-RFBR project 17-5-41141 References J. Hjort, O. Karjalainen, J. A. Aalto, S. Westermann, V. Romanovsky, F. Nelson, B. Etzelmuller, M. Luoto. Degrading permafrost puts Arctic infrastructure at risk by mid-century. Nature Communications, 2018. T. V. Orlov, A. V. Zverev, S. A. Sadkov, E. G. Panchenko. Some aspects of empirical verification of stochastic model of the human caused thermokarst using remote sensing data; 15th International Multidisciplinary Scientific GeoConference SGEM 2015, Book1 Vol. 2, 2015. pp. 711-716. A. S. Victorov, T. V. Orlov, V. N. Kapralova, O. N. Trapeznikova, S. A. Sadkov, A. V. Zverev. Stochastic modelling and natural risk assessment of current lacustrine thermokarst for existing and planned engineering structures; Natural Hazards and Risk Research in Russia. Spinger.2018. pp. 219-240 [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042860 Weber, Ute (Helmholtz Gemeinschaft, Bonn, Germany) and Schuetze, Claudia. MOSES; a novel observing system for highly dynamic events [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13650, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
MOSES (Modular Observation Solutions for Earth Systems) is a novel observing system developed by the Helmholtz Centres in the research field "Earth and Environment". It is designed to unravel the impact of short-term events on the long-term development of Earth and environmental systems. Heat waves and droughts, hydrologic extremes, abrupt permafrost thaw and ocean eddies are in the focus of this event-oriented observation and research initiative. Although it is well known that the Global Change affects the Earth and environment at many different time and length scales, currently, only very limited knowledge is available on the importance of such distinct dynamic events. MOSES is being developed to close this gap. The investigation of the long-term effects of these events is most acute as the impact of global and climate change on society becomes increasingly evident: The increase in extreme weather events is under intense debate, Arctic warming is accelerating and marine circulations and ecosystems are undergoing rapid change. The Helmholtz Association is investing 30 million Euros to implement the new research facility, which is designed as a 'system of systems'. During the implementation phase from 2017 to 2021, the participating centres develop, miniaturise and automate sensor and measuring systems, which are combined into specific observation modules. These record energy, water, greenhouse gas and nutrient cycles on the land surface, in coastal regions, in the ocean, in snow and ice regions, and in the atmosphere - but especially the interactions between Earth compartments. MOSES campaigns and the resulting data sets aim at improving predictions of Earth and environmental change and at supporting the development of societal adaptation strategies. The mobile infrastructure also represents an important addition to existing monitoring networks and satellite missions, which are mostly designed for long-term, large-scale environmental observation. Examples include ICOS (Integrated Carbon Observation System), LTER (Long-Term Ecological Research) or TERENO (Terrestrial Environmental Observatories). First MOSES test campaigns started in summer 2018 and will be continued during the next three years with various scientific partners. Homepage: www.moses-helmholtz.de [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042875 Wenger, Angelina (Stockholm University, Stockholm, Sweden); Gustafsson, Orjan; Holmstrand, Henry; Steinbach, Julia; Semiletov, Igor; Shcherbakova, Kseniya; Kosmach, Denis and Shakhova, Natalia. Characterization of elevated methane in a long seawater transect on the outer East Siberian Sea [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-17933, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The East Siberian Arctic Shelf (ESAS) has a large inventory of buried carbon and methane (CH4) as part of and below subsea permafrost. Warming of this system by geothermal heat and by overlying seawater throughout the Holocene, recently amended by Anthropocene warming, has brought subsea permafrost towards the point of thaw. There have been extensive observations of strongly elevated CH4 concentrations in ESAS seawater over the recent decade. However, there are still large uncertainties from what part of the subsea system the released methane originates, and also about the large-scale geographical variations. This study presents methane observations from the 2014 SWERUS-C3 cruise along an east-west transect of the outer East Siberian Sea (ESS). Surface ocean methane concentrations were regularly above the atmospheric equilibrium concentration, with seawater concentrations in a ESS hotspot region reaching up to 460 nM. The observations include 13C stable isotope observation in an active ebullition site. Understanding the sources and spatial distribution of the methane releases will aid in understanding the composition and functioning of the subsea permafrost/methane system and help us move toward predictive capacity of how the methane evasions will develop into the future. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042876 Wild, Birgit (Stockholm University, Department of Environmental Science and Analytical Chemistry, Stockholm, Sweden); Andersson, August; Tesi, Tommaso; Pipko, Irina; Dudarev, Oleg V.; Semiletov, Igor; Shakhova, Natalia and Gustafsson, Orjan. Transport and degradation of permafrost and peat carbon in large Siberian rivers [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13860, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Permafrost and peat deposits of northern high latitudes contain large amounts of organic carbon that will be increasingly thawed and remobilized as temperatures rise. Part of the carbon may be degraded to CO2 and CH4 at the site of thaw, potentially amplifying climate warming. Another part will be released into aquatic systems, removed from active cycling by sediment sequestration or degraded during transport, thereby inducing a carbon-climate feedback translocated up to thousands of kilometers away from its origin. This lateral carbon transfer is difficult to constrain, but represents an important component of the high latitude carbon cycle and an opportunity to monitor permafrost thaw across heterogeneous catchments in a warming climate. In a recent study, we used long-term records of 13C and 14C in the four largest Siberian rivers Ob, Yenisey, Lena and Kolyma to show that permafrost- and peat-derived carbon represents on average only 17% of total fluvial dissolved and particulate organic carbon (DOC, POC). Considering the vast extent of permafrost and peat deposits in the river catchments, these findings may indicate rapid degradation of terrestrially derived carbon during river transport. In this follow-up study, we employed a high-spatial resolution dataset of POC, DOC and dissolved inorganic carbon (DIC) to assess the fluvial transport and degradation of permafrost- and peat-derived carbon along the Ob and Lena rivers. Both rivers showed decreasing POC concentrations towards the river mouths and increasing offsets between the 13C contents of POC and potential carbon sources, supporting the degradation or sedimentation of a large POC fraction. In the Ob, DIC concentrations decreased while DOC concentrations and CO2 oversaturation of surface waters compared to the atmosphere increased. The Lena in contrast showed no consistent change in DOC or DIC concentrations and only slight CO2 oversaturation. Taken together, these findings support the degradation of terrestrially derived carbon during river transport and release of the resulting CO2 to the atmosphere, but also indicate substantial differences in land-river-atmosphere carbon fluxes between river catchments, possibly related to differences in climate, permafrost extent or soil properties. Our data will be combined with atmospheric observations of CO2 along the rivers as well as 14C source apportionment of DOC and POC to quantify the contribution of different organic carbon sources to both rivers across their heterogeneous catchments and assess its fate during transport. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042865 Xie Hongyu (China University of Geosciences, School of Water Resources and Environment, Beijing, China); Jiang Xiaowei; Wan Li; Wang Xusheng and Tang Han. The influence of groundwater regime by seasonally frozen soils [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-5424, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Seasonally freezing and thawing processes occur in approximately 50% of the land area in the Northern Hemisphere and play a significant role in some hydrological processes. In the last several decades, there are numerous numerical studies of hydrological processes in seasonally frozen soils, however, numerically modeling of considering water movement in both unsaturated and saturated zones still remains a challenge. Based on this scientific problem, we chose the climate condition in New Brunswick, Canada as a typical seasonally frozen ground and used the SHAW model to simulate the vertical freezing-induced water movement and resulting water table decline during a complete freezing period in different water table depths and soil textures. According to the numerical results, as water table depth increases, the upward flux towards the freezing front and the water table decline both decreases significantly, which are determined by the lower unsaturated hydraulic conductivity and smaller hydraulic gradient. Moreover, compared with coarse-texture soils (i.e. sand and loam), fine-texture soils (i.e. silt and clay) lead to larger freezing-induced upward flow and water table decline because of the soil water characteristics, which are different from Harlan's (1973) theoretical results based on simulation with limited time duration. Therefore, this research enhances understanding on the coupling of atmospheric conditions, soil water and groundwater in seasonally frozen regions. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042849 Yu Lupeng (Linyi University, School of Resources and Environmental Sciences, Linyi, China); Roskin, Joel and Greenbaum, Noam. Aeolian-fluvial interactions stabilize desert in the Qaidam Basin [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-19084, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Desert and dunefield evolution is usually considered to be mainly controlled by palaeoclimatic changes, especially precipitation changes. Accordingly, desert evolution records could be applied to reconstruct paleoclimatic changes. We noticed many cycles of dune sand and fluvial/flood-relevant sediments in and around the Tiekui Desert dunefield (TKD), eastern Qaidam Basin (QB), NE Qinghai-Tibetan Plateau, indicating that Aeolian-Fluvial Interactions (AFI), predominantly the damming of watercourses by dune (dune-damming), might have had a major impact on dunefield evolution. Here we apply OSL dating to establish the chronology of the AFIs in the TKD. Based on 120 OSL ages, records of AFIs since ca. 140 ka were reconstructed. Most of the AFIs developed with the onset of deglaciation periods, i.e. transition periods from cold to warm stages, e.g., MIS 2-1, MIS 3b-3a, MIS 5b-5a, MIS 5d-5c, and MIS 6-5e. During glacier or cold periods, the flows were very limited or absent, and the TKD dunes remobilized, expanded and buried the shrunken streams and their floodplains. When deglaciation started, the meltwater from glaciers and permafrost in the source regions increased sharply, and precipitation also increased in early Holocene, however, the increased flow had no drainage patterns to cross the TKD. This caused floods in the TKD, which were finally blocked by large dunes, forming dune-dammed lakes. As long as dunes were mobile, dune movement maintained the dune dams and possibly advanced into water bodies. These processes hindered the forward migration of lakes and the re-establishment of drainage systems. With time, these water bodies elevated ground water levels, deposited fine grain sediments, and increased vegetation cover. These AFI processes reduced sand mobility and led to dune stabilization. Once the TKD was mostly stabilized, aeolian activities significantly decreased and drainage systems began to develop. Then rivers deeply incised into the accumulated AFI sediments, which significantly lowered the groundwater levels. With the drop of groundwater level and decreased precipitation during the arid late Holocene, desert restarted to active. To summarize, AFI processed directly controlled the growth of the TKD, while the climatic changes, i.e. glacial-interglacial cycles, controlled the occurrence of AFI. This study stresses the importance of surface processes for the geomorphology and paleoenvironmental evolution. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042844 Yumashev, Dmitry (Lancaster University, Pentland Centre for Sustainability in Business, Lancaster, United Kingdom); Hope, Chris; Schaefer, Kevin; Riemann-Kampe, Kathrin; Iglesias-Suarez, Fernando Fernando; Jafarov, Elchin; Burke, Eleanor; Young, Paul; Elshorbany, Yasin and Whiteman, Gail. Climate policy implications of nonlinear decline of Arctic land permafrost, snow and sea ice [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-15815, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Arctic feedbacks accelerate climate change and could jeopardise mitigation efforts. A release of carbon to the atmosphere from thawing permafrost results in a positive feedback. Similarly, the loss of sea ice and land snow increases solar absorption in high latitudes, creating a positive albedo feedback. A constant albedo feedback and zero permafrost feedback have been the legacy values used in nearly all climate policy studies. However, observations and models show that both feedbacks are nonlinear with the permafrost feedback being the stronger of the two. Here we use novel dynamic emulators of complex physical models in the integrated assessment model PAGE-ICE to estimate the impacts of including these nonlinear Arctic feedbacks on the global climate and economy under a range of scenarios consistent with the Paris Agreement. In most scenarios the combination of the two nonlinear feedbacks causes extra warming globally compared with their legacy values. The permafrost carbon feedback is increasingly positive in warmer climates while the albedo feedback is either similar to or weaker than the legacy values. The combination of these two factors increases the mean discounted economic effect of climate change by 4.1% ($25 trillion) under the 1.5°C scenario, 5.6% ($34 trillion) under the 2°C scenario, 4.8% ($67 trillion) under levels of mitigation consistent with the current national pledges. Our findings support the need for more proactive mitigation measures to keep global temperature rise below 2°C. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042890 Zabelina, Svetlana (Russian Academy of Sciences, N. Laverov Federal Center for Integrated Arctic Research, Freshwater and Marine Ecosystems Laboratory, Russian Federation); Klimov, Sergei; Shirokova, Liudmila; Chupakov, Artem; Pokrovsky, Oleg and Guérin, Frederic. Features of methane emission in wetland during permafrost thawing [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-13532, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The specificity of the continental part of the Arctic latitudes is large areas covered by wetlands. Huge masses of slightly decomposed organic substance (peat) are conserved in permafrost. The modern climatic changes and development of northern territories lead to intensifying of cryolithozone degradation process. The thawing of permafrost is accompanied by the thermokarst lakes formation and the withdrawal of ancient organic carbon from frozen soils in the form of carbon dioxide and methane, which is one of the most serious environmental threats in the global climate change scenario. Tundra landscape complexes have an important climate-regulating function at the biosphere level, but it is still not properly taken into account when drawing up global models of climate changes and carbon balance. Quantifying methane emissions from discontinuous permafrost is an important task. This paper presents the first results of a dissolved methane concentrations study in water of 54 thermokarst water bodies of Bolshezemelskaya tundra (BZT) at different stages of formation. Direct measurements of methane flux from the surface of 8 lakes using a floating chamber were carried out, and a diffusion flux of methane from the lakes surface was calculated on the basis of water surface methane concentration, wind speed and gas transfer coefficient. The research results have shown that all the studied water bodies were oversaturated with CH4. Concentrations of CH4 in lakes varied from 0.081 to 106.1 mol l-1. The highest CH4 concentrations were observed in subsidence, different from lakes with high concentrations of DOC, mineralization, and microelement composition. The diffusion methane flux from the subsidence and depression 11-30 times exceeded that from the thermokarst lakes surface. Measured with the floating chamber, methane fluxes from the surface water bodies were 1-2 orders of magnitude higher than those calculated. Significant and abrupt increase of methane flux in air samples from the chamber on a number of lakes indicates registering by the chamber of a bubble stream from the bottom of a lake. Methane emissions by means of bubble transfer ranged from 19 to 99%. Thus, depressions, subsidence, as well as small reservoirs (<100 m2), are characterized by the highest concentrations of CH4, DOC. They are not represented on existing maps and databases of world lakes, and contain 3-70 times higher methane compared to large lakes. Methane emissions from small water bodies should be included in the methane flux assessment system from the Arctic tundra territory. All the more so as their contribution to total surface coverage of BZT area will increase, both as a result of climate warming and with an increase of anthropogenic load. The reported study was funded by MES of Russia under the theme number 0409-2015-0140, the project of the RSF 15-17-10009, RFBR_(Arctic resources) according to the research project No. 18-05-70087. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042842 Zhang Tingjun (Lanzhou University, College of Earth and Environmental Sciences, Lanzhou, China) and Mu Cuicui. Understanding permafrost carbon cycle over the Third Pole regions in a warming climate [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-2703, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The Third Pole Regions are experiencing a rapid warming during the past several decades as indicated by air temperature increase, glacier retreats, significant changes in spring phenology, vegetation greening, increase in permafrost temperatures and active layer thickness. These changes play an important role in ecosystem evolution and substantial impact on carbon exchange between the active layer and the atmosphere. The Third Pole regions have the largest areas of mountain permafrost terrain in the mid- and low- latitudes in the northern hemisphere. Mountain permafrost regions are mainly characterized with complex topography, which can greatly affect climatic conditions and pedogenesis, thus further influencing soil organic carbon (SOC) densities and leading to large uncertainties of SOC stocks estimates. SOC stored in the Third Pole regions is very sensitive to global warming due to relatively high temperatures, thin thickness and unstable thermal states of permafrost. Decomposition of SOC with temperature increasing can enhance CO2 and CH4 emissions, which is a potentially important feedback to climate warming. Here we highlight what we know, as well as an important knowledge gap in our understanding of differences in permafrost carbon cycling in the Arctic and Third Pole regions. We also summarize new work focused on improving our understanding of greenhouse gas dynamics in these regions. It is essential for creating a comprehensive database of soil carbon data in permafrost regions of the Third pole, which allow future studies to better synthesize existing observations. It needs to conduct a data synthesis of long-term greenhouse gas emissions, including winter emissions, which may account for a large fraction of total greenhouse gas emissions in permafrost regions. The biogeochemical dynamics of mountain permafrost carbon cycling in the Third pole regions require studies due mainly to higher temperatures and thermal instability of permafrost than the Arctic regions. It needs to improve the observation technology, such as aircraft observation, which will allow the measurements of inland water-air and thermokarst-affected gas exchange. It is still unclear to predict the effect of carbon sink and source in the Third Pole due to some uncertainties in permafrost degradation such as distributions of thermokarst landscapes. A better understanding of mountain permafrost carbon cycling and underlying environmental drivers will help scientists predict the future feedback of greenhouse gas emissions to climate change. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042866 Zhu, Zhiliang. Monitoring surface and subsurface change in permafrost landscape in Northern Alaska with in-situ and remote sensing methods [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-18356, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
Much of Northern Alaska ecosystems is underlain with permafrost that is experiencing a sustained warming trend. Measuring environmental changes including permafrost thawing is difficult due to logistic reasons in the boreal and Arctic conditions. Over four years (2014-2017), we used in-situ geophysical instruments to collect permafrost measurements including depth of active layer, moisture content, and change in subsurface structure as the result of permafrost thaw and refreezing. The geophysical methods we used included electrical resistivity tomography (ERT), nuclear magnetic resonance (NMR), and manual probing (MP). The data were collected at sample sites in both north and south of Fairbanks, Alaska, each of the sample site was a transect approximately 100 meters in length. Of the sample sites, 20 of them included all of the above methods (ERT, NMR, MP). In this study, we linked land surface observations (such as surface temperature, albedo, water cover) derived from Landsat at the similar time windows as the subsurface data on the 20 sample sites. The analysis characterized above-surface landscape changes in relation to the below-surface measurements. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042841 Zhu Liping (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, China) and Peng Ping. Construction and data integration of field observation system for environmental change of the Third Pole and Silk Road [abstr.]: in European Geosciences Union general assembly 2019, Geophysical Research Abstracts, 21, Abstract EGU2019-6495, 2019. Meeting: European Geosciences Union general assembly 2019, April 7-12, 2019, Vienna, Austria.
The Tibetan Plateau, which is called as the Third Pole region, is the most concerned high mountain area in the world. It is called as "Asian water tower" because of its widespread glaciers, rivers and lakes which may exert huge influence on the lower reaches. Most part of the Silk Road economic belt is located within the arid area of Central Asia, with the surface water resources being strongly influenced by the high mountain ice melt water from the Third Pole area. Under the condition of global climate change, the water tower effect of the Third Pole region not only changes the water resources and environmental conditions of the region itself, but also has an obvious influence on the economic development mode of the Silk Road economic belt. For the lack of long-term monitoring data of regional climate and environmental changes in the Tibetan Plateau and the Silk Road economic belt, and insufficiency of the researches for the reasons derived of nature/human activities, a three-dimensional observation system is being constructed to serve the Third Pole environmental change and the development of the Silk Road. This observation system, based upon the High-cold region Observation Research Network and the field stations of the Central Asian Ecological Center of the Chinese Academy of Sciences, is making the technical specification for observations of land surface process and environmental changes, perfecting the observation and research contents of environmental change elements, constructing new observation stations, integrating the in site network monitoring and remote sensing data, and establish a multi-source climate and environmental element assimilation database based on the scale transformation. This system will serve to clarify the impact process and extent of natural change/human activity on environmental changes in the Third Pole area and the Silk Road. Through 5 years observation research and data integration, the system will produce the observational data set of meteorological, atmospheric environment, lake hydrology and ecological community index in the study area. Based on the satellite remote sensing image interpretation and in site observation data verification, a series of data products will be established, such as meteorological elements, lake water storage and water quality, surface vegetation biomass, permafrost distribution and glacier area and ice volume change in typical area of the Tibetan Plateau. The data will be managed on an observation data system, which provides the functions of remote control of instruments, real-time transmission of in site observation data and monitoring scene, on-line data quality control, data query and statistics and visual output. [Copyright Author(s) 2019. CC Attribution 4.0 License: https://creativecommons.org/licenses/by/4.0/legalcode]
2019042188 Friedrich, Anke M. (University of Munich, Department of Earth and Environmental Sciences, Munich, Germany). Identification of coseismic rupturing in the absence of a "free-face" based on textural evidence within non-lithified deposits [abstr.]: in Geological Society of America, 2018 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 50(6), Abstract no. 279-1, November 2018. Meeting: Geological Society of America, 2018 annual meeting & exposition, Nov. 4-7, 2018, Indianapolis, IN.
Paleoseismological studies often yield rates of active faulting and seismic hazards that are lower than those estimates based on seismological or geodetic data. A number of causes have been postulated for this phenomenon. An additional problem might lie within the intrinsic definition of what constitutes an active or potentially active fault. Paleoseismological criteria to identify a fault as active or potentially active require the presence of a free-face, i.e., a discrete offset of the earth's surface across a fault. Small faults or the ends of large rupture segments--which yield more distributed deformation--are typically excluded from seismic hazard assessments. Debates are raging over whether deformational features constitute coseismic-rupture-related damage or were due to non-seismic mechanisms such as creep or permafrost. Evans and Bradbury (Geology, 2007) suggested the mapping of textural evidence in near-surface deposits as an urgently needed tool for paleoseismologists and structural geologists. Paleoseismological studies of smaller-offset faults may provide such opportunities. Based on results by Küler et al. (Int. J. Earth Sci., 2018), I further analysed the damage pattern developed in a non-lithified Holocene coarse-clastic deposit above Devonian basement across a gentle surface scarp (intracontinental Europe), which had been under severe critique by reviewers. Analysis was based on the relationship between inter- and intraclast-fractures and statistically significant populations of rotated clasts. Analytical mapping yields textural and structural evidence for near-surface seismogenic rupturing: hundreds of systematically rotated, then fractured gravels in a 30-m-wide damage zone indicate particulate to cataclastic flow mechanisms, and deformation at high strain-rates consistent with the regional tectonic stress field. Results indicate that the clasts were first rotated then fractured. The sense of gravel rotation invokes an elastic rebound mechanism, which affected the underlying basement rocks. Coseismic strain may have been transmitted across the basement-sediment interface kinematically, and it then was effectively dissipated in the sediment by fracture branching. The thicker the sediment-cover above basement, the more effective the energy-dissipation by fracturing. Mixed-gravel textures furnish a high-resolution paleoseismological inventory to extend mappable limits of active faults, which will result in improved earthquake magnitude, hazard, and zoning estimates.
2019040007 Cuozzo, Nicolas (University of Washington, Department of Earth and Space Sciences, Seattle, WA); Sletten, Ronald; Hu, Yan and Teng, Fang-Zhen. Using magnesium isotopes to understand chemical weathering in permafrost environments: in Goldschmidt abstracts 2018, V.M. Goldschmidt Conference - Program and Abstracts, 28, 2018. Meeting: Goldschmidt 2018, Aug. 12-17, 2018, Boston, MA.
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