May 2018 Permafrost Monthly Alert (PMA) Program
The U.S. Permafrost Association is pleased to
announce the availability of an updated searchable database on permafrost-related
publications. The American Geosciences Institute, with support from
the National Science Foundation, has “migrated” the previous Cold
Regions Bibliography to a new platform. Included are the US Permafrost
Association supported Monthly Permafrost Alerts dating back to 2012.
The Bibliography is searchable at : www.coldregions.org.
Entries in each category are listed in chronological
order starting with the most recent citation.
The individual Monthly Permafrost Alerts are found
on the US Permafrost Association website : http://www.uspermafrost.org/monthly-alerts.shtml.
2018 Permafrost Alert Sponsors
Browse by Reference Category:
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2018049605 Dupeyrat, Laure (Université Paris-Sud, Geosciences Paris Sud, Orsay, France); Hurault, Benoît; Costard, François; Marmo, Chiara and Gautier, Emmanuele. Satellite image analysis and frozen cylinder experiments on thermal erosion of periglacial fluvial islands: Permafrost and Periglacial Processes, 29(2), p. 100-111, illus. incl. 2 tables, 29 ref., June 2018.
Frozen islands in the Lena River, Siberia, experience rates of fluvial thermal erosion exceeding 10 m/year. The islands erode differentially, with rates of frontal retreat exceeding those on island sides. We define the erosion ratio (ER) between the front and sides to estimate this differential erosion. A GIS-based study of 19 islands from 1967 to 2010 indicated average erosion rates of 19.7 and 3.7 m/year for the island heads and sides, respectively. The average ER over the period was 4.7. An analytical model of local thermal erosion for a frozen cylinder of sand in a turbulent water flow is proposed, assuming an ablation process. Thermal erosion of 19 frozen cylinders was measured for water flows of different temperature and velocity in a cold chamber. As observed in the field, frontal erosion always exceeded lateral erosion, with an average ER of 1.6. The ER decreased with increasing temperature from 5 to 15°C. The higher value of ER in the field may be due to interactions with neighboring islands and banks. An empirical law including phase change and the process of erosion is proposed, and validates our model compared with previous laws that do not account for erosion. The erosion process enhances heat transfer. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018049607 Obu, Jaroslav (University of Oslo, Oslo, Norway); Kosutnik, Jure; Overduin, Paul P.; Boike, Julia; Blatnik, Matej; Zwieback, Simon; Gostincar, Petra and Mihevc, Andrej. Sorted patterned ground in a karst cave, Ledenica pod Hrusico, Slovenia: Permafrost and Periglacial Processes, 29(2), p. 121-130, illus. incl. 3 tables, 44 ref., June 2018.
Patterned ground is a characteristic periglacial landform in polar and alpine environments but has not been systematically studied in karst caves. Here we characterize the periglacial environment and sorted stripes within the Ledenica pod Hrusico ice cave, western Slovenia. The stripes were mapped, sediment depth and grain size were measured, and cave and outside air temperatures were monitored together with ground temperatures. Eleven sorted stripes of coarse limestone debris had developed on 1 m thick silt-rich sediment, underlain by limestone bedrock. Silt-rich cave sediments can accumulate as insoluble carbonate residue or during flood events, whereas coarse debris may result from frost shattering. Cold winter air entered the ice cave, but little air exchange occurred during summer, when the cave air temperature slowly rose to a maximum of 5°C. Winter temperature oscillations propagated efficiently to the snow-free cave floor. Fourteen freeze-thaw cycles were observed at the patterned-ground surface during winter 2015/2016 and may cause the differential frost heaving necessary for sediment sorting. Such periglacial conditions and mixtures of silty and coarse sediments can produce sorted patterns in karst caves. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018049606 Palmtag, Juri (Stockholm University, Department of Physical Geography, Stockholm, Sweden) and Kuhry, Peter. Grain size controls on cryoturbation and soil organic carbon density in permafrost-affected soils: Permafrost and Periglacial Processes, 29(2), p. 112-120, illus. incl. 4 tables, 30 ref., June 2018.
This meta-analysis aims to describe the relationship between grain size distributions and soil organic carbon (SOC) storage in mineral subsoil and SOC-enriched cryoturbated pockets in five areas of continuous permafrost that differ in glaciation history and soil parent materials. Our results show a positive relationship between the proportion of soil particles in fine-grained fractions (colloid to medium silt) and SOC storage. Finer textured soils had significantly higher SOC storage in mineral subsoil samples (not SOC-enriched through cryoturbation) than coarser textured soils. However, the process of SOC enrichment through cryoturbation was most pronounced in soils with coarser grain sizes in the range of coarse silt and very fine sand. Although fine-grained textures provide better physical and biochemical protection for soil organic matter, their strong cohesion reduces the mixing of soil horizons and the effectiveness of cryoturbation. A higher ratio of coarse silt to clay in samples was a good predictor of SOC enrichment through cryoturbation across soil samples, soil profiles and study areas. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018049603 Way, Robert G. (University of Ottawa, Department of Geography, Environment and Geomatics, Ottawa, ON, Canada) and Lewkowicz, Antoni G. Environmental controls on ground temperature and permafrost in Labrador, northeast Canada: Permafrost and Periglacial Processes, 29(2), p. 73-85, illus. incl. 4 tables, sketch map, 58 ref., June 2018.
Field data from 83 environmental monitoring stations across Labrador, 17 with permafrost, were used to analyze the interrelationships of key variables considered in the temperature at the top of permafrost model. Snow depth, not mean annual air temperature, was the strongest climatic determinant of mean temperatures at the ground surface and at the base of the annual freeze-thaw layer, and its variability was most closely related to land cover class. A critical late-winter snow depth of 70 cm or more was inferred to be sufficient to prevent the formation of permafrost at the monitoring sites, which meant that permafrost was absent beneath forest but present in some tundra, peatland and bedrock locations. Analyses showed no statistically significant relations identified between topographic indices and various station parameters, challenging their utility for regional modeling. Testing of several different land cover datasets for model parameterization gave errors in ground surface temperature ranging from ± 0.9 to 2.1°C. These results highlight the importance of local field data and emphasize the necessity of high-quality national-scale land cover datasets suitable for permafrost modeling. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018049604 Wu Xiaobo (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Nan Zhuotong; Zhao Shuping; Zhao Lin and Cheng Guodong. Spatial modeling of permafrost distribution and properties on the Qinghai-Tibet Plateau: Permafrost and Periglacial Processes, 29(2), p. 86-99, illus. incl. 4 tables, sketch map, 64 ref., June 2018.
Accurate information on the distribution of permafrost and its thermal and hydrological properties is critical for environmental management and engineering development. This study modeled the current state of permafrost on the Qinghai-Tibet Plateau (QTP), including the spatial distribution of permafrost, active-layer thickness (ALT), mean annual ground temperature (MAGT), depth of zero annual amplitude (DZAA) and ground-ice content using an improved Noah land surface model (LSM). The improved model was examined at a typical permafrost site and then applied to the entire QTP using existing gridded meteorological data and newly developed soil data. The simulated permafrost distribution and properties were validated against existing permafrost maps in three representative survey areas and with measurements from 54 boreholes. The results indicate that the Noah LSM with augmented physics and proper soil data support can model permafrost over the QTP. Permafrost was simulated to underlie an area of 1.113 ´ 106 km2 in 2010, accounting for 43.8% of the entire area of the QTP. The modeled regional average ALT and MAGT were 3.23 m and -1.56°C, respectively. Spatially, MAGT increases and DZAA becomes shallower from north to south. Thermally unstable permafrost (MAGT above -0.5°C) is predominant, accounting for 38.75% of the whole permafrost area on the QTP. Ice-rich permafrost was mainly simulated around lakes across the north-central QTP. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018047336 van der Bilt, Willem G. M. (University of Bergen, Department of Earth Science, Bergen, Norway); Rea, Brice; Spagnolo, Matteo; Roerdink, Desiree L.; Jorgensen, Steffen L. and Bakke, Jostein. Novel sedimentological fingerprints link shifting depositional processes to Holocene climate transitions in East Greenland: Global and Planetary Change, 164, p. 52-64, illus. incl. 1 table, sketch maps, 97 ref., May 2018.
The Arctic warms faster than any other region of our planet. Besides melting glaciers, thawing permafrost and decreasing sea-ice, this amplified response affects earth surface processes. This geomorphological expression of climate change may alter landscapes and increase the frequency and magnitude of geohazards like floods or mass-movements. Beyond the short span of sparse monitoring time series, geological archives provide a valuable long-term context for future risk assessment. Lake sediment sequences are particularly promising in this respect as continuous recorders of surface process change. Over the past decade, the emergence of new techniques that characterize depositional signatures in more detail has enhanced this potential. Here, we present a well-dated Holocene-length lake sediment sequence from Ammassalik Island on southeast Greenland. This area is particularly sensitive to regional shifts in the Arctic climate system due to its location near the sea-ice limit, the Greenland Ice Sheet and the convergence of polar and Atlantic waters. The expression of Holocene change is fingerprinted using physical (grain size, organic content, density), visual (3-D Computed Tomography) and geochemical (X-Ray Fluorescence, X-Ray Diffraction) evidence. We show that three sharp transitions characterize the Holocene evolution of Ymer Lake. Between 10 and 9.5 cal. ka BP, rapid local glacier loss from the lake catchment culminated in an outburst flood. Following a quiescent Holocene climatic optimum, Neoglacial cooling, lengthening lake ice cover and shifting wind patterns prompted in-lake avalanching of sediments from 4.2 cal. ka BP onwards. Finally, glaciers reformed in the catchment around 1.2 cal. ka BP. The timing of these shifts is consistent with the regional expression of deglaciation, Neoglacial cooling and Little Ice Age-type glacier growth, respectively. The novel multi-proxy approach applied in this study rigorously links depositional sediment signatures to surface processes and thereby provides a key step towards a process-based understanding of climate responses.
2018047012 Andrieux, Eric (Université de Bordeaux, De la Préhistoire à l'Actuel; Culture, Environnement et Anthropologie, Pessac, France); Bateman, Mark D. and Bertran, Pascal. The chronology of late Pleistocene thermal contraction cracking derived from sand wedge OSL dating in central and southern France: Global and Planetary Change, 162, p. 84-100, illus. incl. 3 tables, sketch maps, 85 ref., March 2018. Includes appendices.
Much of France remained unglaciated during the Late Quaternary and was subjected to repeated phases of periglacial activity. Numerous periglacial features have been reported but disentangling the environmental and climatic conditions they formed under, the timing and extent of permafrost and the role of seasonal frost has remained elusive. The primary sandy infillings of relict sand-wedges and composite-wedge pseudomorphs record periglacial activity. As they contain well-bleached quartz-rich aeolian material they are suitable for optically stimulated luminescence dating (OSL). This study aims to reconstruct when wedge activity took place in two regions of France; Northern Aquitaine and in the Loire valley. Results from single-grain OSL measurements identify multiple phases of activity within sand wedges which suggest that wedge activity in France occurred at least 11 times over the last 100 ka. The most widespread events of thermal contraction cracking occurred between ca. 30 and 24 ka (Last Permafrost Maximum) which are concomitant with periods of high sand availability (MIS 2). Although most phases of sand-wedge growth correlate well with known Pleistocene cold periods, the identification of wedge activity during late MIS 5 and the Younger Dryas strongly suggests that these features do not only indicate permafrost but also deep seasonal ground freezing in the context of low winter insolation. These data also suggest that the overall young ages yielded by North-European sand-wedges likely result from poor record of periglacial periods concomitant with low sand availability and/or age averaging inherent with standard luminescence methods.
2018046927 Coles, Anna E. (University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK, Canada) and McDonnell, J. J. Fill and spill drives runoff connectivity over frozen ground: Journal of Hydrology, 558, p. 115-128, illus. incl. 2 tables, 66 ref., March 2018.
Snowmelt-runoff processes on frozen ground are poorly understood at the hillslope scale. This is especially true for hillslopes on the northern Great Plains of North America where long periods of snow-covered frozen ground with very shallow slopes mask any spatial patterns and process controls on connectivity and hillslope runoff generation. This study examines a 4.66 ha (46,600 m2) hillslope on the northern Great Plains during the 2014 spring snowmelt season to explore hillslope runoff processes. Specifically, we explore the spatial patterns of runoff production source areas and examine how surface topography and patterns of snow cover, snow water equivalent, soil water content, and thawed layer depth - which we measured on a 10 m grid across our 46,600 m2 hillslope - affect melt water partitioning and runoff connectivity. A key question was whether or not the controls on connectivity are consistent with the fill and spill mechanism found in rain-dominated and unfrozen soil domains. The contrast between the slow infiltration rates into frozen soil and the relatively fast rates of snowmelt delivery to the soil surface resulted in water accumulation in small depressions under the snowpack. Consequently, infiltration was minimal over the 12 day melt period. Instead, nested filling of micro- and meso-depressions was followed by macro-scale, whole-slope spilling. This spilling occurred when large patches of ponded water exceeded the storage capacity behind downslope micro barriers in the surface topography, and flows from them coalesced to drive a rapid increase in runoff at the hillslope outlet. These observations of ponded water and flowpaths followed mapable fill and spill locations based on 2 m resolution digital topographic analysis. Interestingly, while surface topography is relatively unimportant under unfrozen conditions at our site because of low relief and high infiltrability, surface topography shows episodically critical importance for connectivity and runoff generation when the ground is frozen.
2018047011 Colombo, Nicola (University of Turin, Department of Earth Sciences, Turin, Italy); Salerno, Franco; Gruber, Stephan; Freppaz, Michele; Williams, Mark; Fratianni, Simona and Giardino, Marco. Impacts of permafrost degradation on inorganic chemistry of surface fresh water: Global and Planetary Change, 162, p. 69-83, illus. incl. 1 table, 189 ref., March 2018. Review.
Recent studies have shown that climate change is impacting the inorganic chemical characteristics of surface fresh water in permafrost areas and affecting aquatic ecosystems. Concentrations of major ions (e.g., Ca2+, Mg2+, SO42-, NO3-) can increase following permafrost degradation with associated deepening of flow pathways and increased contributions of deep groundwater. In addition, thickening of the active layer and melting of near-surface ground ice can influence inorganic chemical fluxes from permafrost into surface water. Permafrost degradation has also the capability to modify trace element (e.g., Ni, Mn, Al, Hg, Pb) contents in surface water. Although several local and regional modifications of inorganic chemistry of surface fresh water have been attributed to permafrost degradation, a comprehensive review of the observed changes is lacking. The goal of this paper is to distill insight gained across differing permafrost settings through the identification of common patterns in previous studies, at global scale. In this review we focus on three typical permafrost configurations (pervasive permafrost degradation, thermokarst, and thawing rock glaciers) as examples and distinguish impacts on (i) major ions and (ii) trace elements. Consequences of warming climate have caused spatially-distributed progressive increases of major ion and trace element delivery to surface fresh water in both polar and mountain areas following pervasive permafrost degradation. Moreover, localised releases of major ions and trace elements to surface water due to the liberation of soluble materials sequestered in permafrost and ground ice have been found in ice-rich terrains both at high latitude (thermokarst features) and high elevation (rock glaciers). Further release of solutes and related transport to surface fresh water can be expected under warming climatic conditions. However, complex interactions among several factors able to influence the timing and magnitude of the impacts of permafrost degradation on inorganic chemistry of surface fresh water (e.g., permafrost sensitivity to thawing, modes of permafrost degradation, characteristics of watersheds) require further conceptual and mechanistic understanding together with quantitative diagnosis of the involved mechanisms in order to predict future changes with confidence.
2018045591 Dean, Joshua F. (Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands); Middelburg, Jack J.; Röckmann, Thomas; Aerts, Rien; Blauw, Luke G.; Egger, Matthias; Jetten, Mike S. M.; Jong, Anniek E. E.; Meisel, Ove H.; Rasigraf, Olivia; Slomp, Caroline P.; Zandt, Michiel H. and Dolman, A. J. Methane feedbacks to the global climate system in a warmer world: Reviews of Geophysics, 56(1), p. 207-250, illus. incl. 1 table, 470 ref., March 2018.
Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios. Abstract Copyright (2018), . The Authors.
2018049602 Higgins, Kellina Leslie (Université de Montréal, Département de Géographie, Montreal, QC, Canada) and Garon-Labrecque, Marie-Ève. Fine-scale influences on thaw depth in a forested peat plateau landscape in the Northwest Territories, Canada; vegetation trumps microtopography: Permafrost and Periglacial Processes, 29(1), p. 60-70, illus. incl. 2 tables, 52 ref., March 2018.
The influence of vegetation and microtopography on fine-scale variability of thaw depth is largely unknown but potentially important for improving modeling of ecosystem-permafrost interactions. To elucidate their influence, we measured tree density, shrub cover and cryptogam presence (lichen and bryophyte) on forested permafrost peat plateaus in the discontinuous permafrost zone in the southern Northwest Territories, Canada. Greater tree density was associated with shallower thaw depth (approximately one quarter of the variance), whereas shrub cover had a negligible influence on thaw depth. Cryptogam species influenced thaw depth, with greater thaw depth associated with Sphagnum than with Cladonia (a difference on the order of 10%). Greater thaw depth occurred beneath hummocks than beneath hollows (a difference also on the order of 10%). Together, canopy cover, cryptogam species and microforms contribute to a variation of roughly half the variance in thaw depth in the peat plateau landscape. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018049601 Kaverin, Dmitry A. (Russian Academy of Sciences, Ural Branch, Komi Scientific Centre, Institute of Biology, Russian Federation); Melnichuk, Evgeniy B.; Shiklomanov, Nikolay I.; Kakunov, Nikolay B.; Pastukhov, Alexander V. and Shiklomanov, Alexey N. Long-term changes in the ground thermal regime of an artificially drained thaw-lake basin in the Russian European north: Permafrost and Periglacial Processes, 29(1), p. 49-59, illus. incl. sects., 3 tables, sketch map, 28 ref., March 2018.
Long-term (1982-1995) observations of the ground thermal regime of a drained thaw-lake basin in the Pechora Lowlands of the Russian European north revealed a high spatial and temporal variability in the ground temperature response to artificial drainage. The thermal response was controlled by the atmospheric climate and by evolution of the landsurface following drainage. Observed changes in permafrost conditions were related to three climatic subperiods identified from air and ground temperature trends. The first (1982-1984) was characterized by gradual ground cooling associated with partial formation of permafrost patches under the initial stage of formation of marshy meadows. The second (1985-1987) involved strong ground cooling, resulting in the formation of a subsurface permafrost layer beneath most of the basin. The third (1988-1995) was marked by a gradual increase in annual mean ground temperature, promoting partial permafrost degradation under marshy meadows and willow stands. Initially, newly aggraded permafrost remained under peat mounds and tundra meadows. The spatial pattern of permafrost change can be attributed to heterogeneous landsurface evolution and variable snow thickness. Four distinct ground temperature regimes are distinguished: (i) thawed ground, (ii) deep permafrost, (iii) unstable permafrost and (iv) stable permafrost. Abstract Copyright (2010), John Wiley & Sons, Ltd.
2018047015 Wang Taihua (Tsinghua University, Department of Hydraulic Engineering, Beijing, China); Yang Dawen; Qin Yue; Wang Yuhan; Chen Yun; Gao Bing and Yang Hanbo. Historical and future changes of frozen ground in the upper Yellow River basin: Global and Planetary Change, 162, p. 199-211, illus. incl. 4 tables, sketch maps, 81 ref., March 2018.
Frozen ground degradation resulting from climate warming on the Tibetan Plateau has aroused wide concern in recent years. In this study, the maximum thickness of seasonally frozen ground (MTSFG) is estimated by the Stefan equation, which is validated using long-term frozen depth observations. The permafrost distribution is estimated by the temperature at the top of permafrost (TTOP) model, which is validated using borehole observations. The two models are applied to the upper Yellow River Basin (UYRB) for analyzing the spatio-temporal changes in frozen ground. The simulated results show that the areal mean MTSFG in the UYRB decreased by 3.47 cm/10 a during 1965-2014, and that approximately 23% of the permafrost in the UYRB degraded to seasonally frozen ground during the past 50 years. Using the climate data simulated by 5 General Circulation Models (GCMs) under the Representative Concentration Pathway (RCP) 4.5, the areal mean MTSFG is projected to decrease by 1.69 to 3.07 cm/10 a during 2015-2050, and approximately 40% of the permafrost in 1991-2010 is projected to degrade into seasonally frozen ground in 2031-2050. This study provides a framework to estimate the long-term changes in frozen ground based on a combination of multi-source observations at the basin scale, and this framework can be applied to other areas of the Tibetan Plateau. The estimates of frozen ground changes could provide a scientific basis for water resource management and ecological protection under the projected future climate changes in headwater regions on the Tibetan Plateau.
2018046941 Wang Taihua (Tsinghua University, Department of Hydraulic Engineering, Beijing, China); Yang Hanbo; Yang Dawen; Qin Yue and Wang Yuhan. Quantifying the streamflow response to frozen ground degradation in the source region of the Yellow River within the Budyko framework: Journal of Hydrology, 558, p. 301-313, illus. incl. 6 tables, sketch maps, 76 ref., March 2018. Includes appendices.
The source region of the Yellow River (SRYR) is greatly important for water resources throughout the entire Yellow River Basin. Streamflow in the SRYR has experienced great changes over the past few decades, which is closely related to the frozen ground degradation; however, the extent of this influence is still unclear. In this study, the air freezing index (DDFa) is selected as an indicator for the degree of frozen ground degradation. A water-energy balance equation within the Budyko framework is employed to quantify the streamflow response to the direct impact of climate change, which manifests as changes in the precipitation and potential evapotranspiration, as well as the impact of frozen ground degradation, which can be regarded as part of the indirect impact of climate change. The results show that the direct impact of climate change and the impact of frozen ground degradation can explain 55% and 33%, respectively, of the streamflow decrease for the entire SRYR from Period 1 (1965-1989) to Period 2 (1990-2003). In the permafrost-dominated region upstream of the Jimai hydrological station, the impact of frozen ground degradation can explain 71% of the streamflow decrease. From Period 2 (1990-2003) to Period 3 (2004-2015), the observed streamflow did not increase as much as the precipitation; this could be attributed to the combined effects of increasing potential evapotranspiration and more importantly, frozen ground degradation. Frozen ground degradation could influence streamflow by increasing the groundwater storage when the active layer thickness increases in permafrost-dominated regions. These findings will help develop a better understanding of the impact of frozen ground degradation on water resources in the Tibetan Plateau.
2018045365 Connon, Ryan (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Devoie, Elise; Hayashi, Masaki; Veness, Tyler and Quinton, William. The influence of shallow taliks on permafrost thaw and active layer dynamics in subarctic Canada: Journal of Geophysical Research: Earth Surface, 123(2), p. 281-297, illus. incl. 2 tables, sketch map, 72 ref., February 2018.
Measurements of active layer thickness (ALT) are typically taken at the end of summer, a time synonymous with maximum thaw depth. By definition, the active layer is the layer above permafrost that freezes and thaws annually. This study, conducted in peatlands of subarctic Canada, in the zone of thawing discontinuous permafrost, demonstrates that the entire thickness of ground atop permafrost does not always refreeze over winter. In these instances, a talik exists between the permafrost and active layer, and ALT must therefore be measured by the depth of refreeze at the end of winter. As talik thickness increases at the expense of the underlying permafrost, ALT is shown to simultaneously decrease. This suggests that the active layer has a maximum thickness that is controlled by the amount of energy lost from the ground to the atmosphere during winter. The taliks documented in this study are relatively thin (<2 m) and exist on forested peat plateaus. The presence of taliks greatly affects the stability of the underlying permafrost. Vertical permafrost thaw was found to be significantly greater in areas with taliks (0.07 m year-1) than without (0.01 m year-1). Furthermore, the spatial distribution of areas with taliks increased between 2011 and 2015 from 20% to 48%, a phenomenon likely caused by an anomalously large ground heat flux input in 2012. Rapid talik development and accelerated permafrost thaw indicates that permafrost loss may exhibit a nonlinear response to warming temperatures. Documentation of refreeze depths and talik development is needed across the circumpolar north. Abstract Copyright (2018), . American Geophysical Union. All Rights Reserved.
2018045135 Cheng Bin (Chinese Academy of Sciences/Guangzhou Institute of Geochemistry, State Key Laboratory of Organic Geochemistry, Guangzhou, China); Xu Jianbing; Lu Zhenquan; Li Yonghong; Wang Weichao; Yang Shan; Liu Hu; Wang Ting and Liao Zewen. Hydrocarbon source for oil and gas indication associated with gas hydrate and its significance in the Qilian Mountain permafrost, Qinghai, northwest China: in Gas geochemistry; from conventional to unconventional domains (Wang Yunpeng, editor; et al.), Marine and Petroleum Geology, 89(Part 1), p. 202-215, illus. incl. strat. col., 6 tables, geol. sketch map, 56 ref., January 2018.
Since gas hydrate was sampled by drilling in the Qilian Mountain permafrost in 2008, to investigate the source of the gas hydrate and the relationship between gas hydrate and the concomitant oil and gas indication (OGI) have become an important research focus. The rocks bearing gas hydrate and OGI from the Middle Jurassic strata in the Qilian Mountain permafrost, Qinghai, Northwest China were extracted by organic solvent and thermally treated (300 °C and 400 °C) in vacuum glass tubes. The hydrocarbons from the extracts and cracked products of the rocks and the stable carbon isotope of the gas hydrocarbons were studied. The results showed that the OGIs can be classified into two types according to different biomarker characteristics. The I-type of OGIs, which suffered from the process of early biodegradation and later-hydrocarbon input and featured high concentrations of 17a(H)-diahopane and abb-regular steranes, mainly originated from the shallow source rocks of the Middle Jurassic strata, while the II-type one with a series of long-chain alkylnaphthalene may originate from the lower portion of Middle Jurassic or deeper source rocks than the Middle Jurassic strata. The adsorbed gas (300°C) of the Middle Jurassic rocks was very wet, had a normal carbon isotope sequence, and can be regarded as an organic thermogenic gas derived from Middle Jurassic source rocks. Comparing the adsorbed (300°C) and cracked (400 °C) gases from the rocks with gases from the gas hydrate and drilling core, we found they had similar stable carbon isotope distributions but different relative contents of methane (C1), ethane (C2), and propane (C3). The Middle Jurassic source rocks are mainly deposited in a freshwater paleo-environment, similar to the parent biomass of the gas hydrate and drilling core gas. The difference of the relative concentrations of C1-C3 may result from different formation processes between the adsorbed and cracked gases and the gas hydrate and drilling core gas. The II-type OGI, which possibly originated from deeper strata than the Middle Jurassic, were closely associated with the gas hydrate under the drilling well and had a similar parent biomass and depositional environment as the gas hydrate, showing they have a closely correlated hydrocarbon origin.
2018046692 Yu Wenbing (Chinese Academy of Sciences, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Lu Yan; Han Fenglei; Liu Yongzhi and Zhang Xuefu. Dynamic process of the thermal regime of a permafrost tunnel on Tibetan Plateau: Tunnelling and Underground Space Technology, 71, p. 159-165, illus., 24 ref., January 2018.
2018048829 Tao, Jing (University of Maryland, Earth System Science Interdisciplinary Center, College Park, MD); Reichle, Rolf H.; Koster, Randal D.; Forman, Barton A. and Xue, Yuan. Evaluation and enhancement of permafrost modeling with the NASA catchment land surface model: Journal of Advances in Modeling Earth Systems, 9(7), p. 2771-2795, illus. incl. 2 tables, 64 ref., November 2017.
Besides soil hydrology and snow processes, the NASA Catchment Land Surface Model (CLSM) simulates soil temperature in six layers from the surface down to 13 m depth. In this study, to examine CLSM's treatment of subsurface thermodynamics, a baseline simulation produced subsurface temperatures for 1980-2014 across Alaska at 9 km resolution. The results were evaluated using in situ observations from permafrost sites across Alaska. The baseline simulation was found to capture the broad features of interannual and intraannual variations in soil temperature. Additional model experiments revealed that (i) the representativeness of local meteorological forcing limits the model's ability to accurately reproduce soil temperature and (ii) vegetation heterogeneity has a profound influence on subsurface thermodynamics via impacts on the snow physics and energy exchange at surface. Specifically, the profile-average RMSE for soil temperature was reduced from 2.96 to 2.10°C at one site and from 2.38 to 2.25°C at another by using local forcing and land cover, respectively. Moreover, accounting for the influence of soil organic carbon on the soil thermal properties in CLSM leads to further improvements in profile-average soil temperature RMSE, with reductions of 16%-56% across the different study sites. The mean bias of climatological active layer thickness is reduced by 36%-89%, and the RMSE is reduced by 11%-47%. Finally, results reveal that at some sites it may be essential to include a purely organic soil layer to obtain, in conjunction with vegetation and snow effects, a realistic "buffer zone" between the atmospheric forcing and soil thermal processes. Abstract Copyright (2017), The Authors.
2018046414 de Klerk, Pim (Staatliches Museum für Naturkunde Karlsruhe, Karlsruhe, Germany); Theuerkauf, Martin and Joosten, Hans. Vegetation, recent pollen deposition, and distribution of some non-pollen palynomorphs in a degrading ice-wedge polygon mire complex near Pokhodsk (NE Siberia), including size-frequency analyses of pollen attributable to Betula: Review of Palaeobotany and Palynology, 238, p. 122-143, illus. incl. 3 tables, sketch maps, 107 ref., March 2017.
Vegetation distribution and pollen deposition were studied in a complex of degraded ice-wedge polygon mires near Pokhodsk (NE Siberia) in order to obtain insight in the relation between actual vegetation and pollen deposition in microtopographic landscape elements. Pollen surface samples with 1 m spacing were collected along a transect and compared with the vegetation at the sample quadrats, with the vegetation in the adjacent quadrats, and with the vegetation at larger distances. A clear regional pollen signal of plants growing outside the study plot was found in the large central depression for pollen types attributable to Comarum palustre, Betula, and Ericales. Local pollen values (i.e. exceeding the regional background deposition values) are restricted to quadrats where the associated taxa are present within 1 m distance (e.g. Comarum palustre, Betula and Rubus chamaemorus). Several plant taxa (e.g. Cyperaceae, Ericales, Pedicularis and Sphagnum) show both high and low pollen deposition values in quadrats where the taxa actually occur, indicating differential pollen production/deposition among specimens of the same taxon. A local signal of grasses and Salix is not noticeable and the pollen signal of these taxa is mainly attributable to plant specimens growing in a larger area. The non-pollen palynomorphs include principally testate amoebae, which dominate on the polygon ridges. Size-frequency analyses show that pollen attributable to dwarf Betula has in the NE Siberian Arctic a large morphological variation.
2018047828 Liu Jie (China University of Geosciences, Institute of Geophysics and Geomatics, Wuhan, China); Liu Jiangping; Cheng Fei; Wang Jing and Liu Xiaoxiao. Rock-physics models of hydrate-bearing sediments in permafrost, Qilian Mountains, China: Applied Geophysics, 14(1), p. 31-39, 23 ref., March 2017. Based on Publisher-supplied data.
Rock-physics models are constructed for hydrate-bearing sediments in the Qilian Mountains permafrost region using the K-T equation model, and modes I and II of the effective medium model. The K-T equation models the seismic wave propagation in a twophase medium to determine the elastic moduli of the composite medium. In the effective medium model, mode I, the hydrate is a component of the pore inclusions in mode I and in mode II it is a component of the matrix. First, the P-wave velocity, S-wave velocity, density, bulk modulus, and shear modulus of the sediment matrix are extracted from logging data. Second, based on the physical properties of the main components of the sediments, rockphysics model is established using the K-T equation, and two additional rock-physics models are established assuming different hydrate-filling modes for the effective medium. The model and actual velocity data for the hydrate-bearing sediments are compared and it is found that the rock-physics model for the hydrate-filling mode II well reproduces the actual data. Copyright 2017 Editorial Office of Applied Geophysics and Springer-Verlag Berlin Heidelberg
2018046285 Fomin, Yu. V. (Russian Academy of Sciences, Shirshov Institute of Oceanology, Moscow, Russian Federation); Zhmur, V. V. and Marchenko, A. V. Transient seawater inflow into seacoast aquifers: Water Resources, 44(1), p. 61-68, illus. incl. 1 table, 9 ref., January 2017.
The coastal zone of the sea is a boundary domain between seawater and land, making most processes within it to show specific features. Seawater can penetrate into aquifers in the land part of the shore through the underwater part of the sea-shore interface and move over considerable distances from the shoreline, mixing with fresh groundwater. This process is of critical importance for the construction of oil and gas pipelines in permafrost areas. Copyright 2017 Pleiades Publishing, Ltd.
2018049476 Stark, Nina (Virginia Polytechnic Institute and State University, Department of Civil and Environmental Engineering, Blacksburg, VA); Radosavljevic, Boris; Quinn, Brandon and Lantuit, Hugues. Application of portable free-fall penetrometer for geotechnical investigation of Arctic nearshore zone: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 54(1), p. 31-46, illus. incl. 1 table, geol. sketch maps, 72 ref., January 2017.
The Arctic is currently undergoing rapid changes with regard to sea ice extent permafrost thaw, and coastal erosion. In addition to hydrodynamic processes, the sediments in the Arctic nearshore zone are affected by freeze-thaw cycles, as well as an increase of abundant suspended sediment introduced by permafrost-induced mass movements, such as retrogressive thaw slumps, and increased river discharge. During the YUKON14 expedition to Herschel Island, Yukon, in situ geotechnical testing of nearshore zone sediments was conducted using a portable free-fall penetrometer. Approximately 200 sites were tested, and four different geotechnical signatures identified and grouped. Most locations were characterized by a soft sediment top layer that exhibited a noticeably lower sediment strength than the underlying sediment. In some cases, multiple layers of different sediment strength were detected in the upper meter of the seabed surface. The results were correlated to existing sediment grain size records and backscatter information from a phase measuring bathymetric sonar. Strong spatial variations in sediment type and stiffness were observed, as well as in abundance and thickness of a top layer of very soft and loose sediment. The geotechnical signatures were correlated to site-specific hydrodynamic conditions, morphology, and vicinity to thaw slumps.
2018046471 Chaudhary, Nitin (Lund University, Department of Physical Geography and Ecosystem Science, Lund, Sweden); Miller, Paul A. and Smith, Benjamin. Modelling Holocene peatland dynamics with an individual-based dynamic vegetation model: Biogeosciences, 14(10), p. 2571-2596, illus. incl. 5 tables, 101 ref., 2017.
Dynamic global vegetation models (DGVMs) are designed for the study of past, present and future vegetation patterns together with associated biogeochemical cycles and climate feedbacks. However, most DGVMs do not yet have detailed representations of permafrost and non-permafrost peatlands, which are an important store of carbon, particularly at high latitudes. We demonstrate a new implementation of peatland dynamics in a customized "Arctic" version of the LPJ-GUESS DGVM, simulating the long-term evolution of selected northern peatland ecosystems and assessing the effect of changing climate on peatland carbon balance. Our approach employs a dynamic multi-layer soil with representation of freeze-thaw processes and litter inputs from a dynamically varying mixture of the main peatland plant functional types: mosses, shrubs and graminoids. The model was calibrated and tested for a sub-Arctic mire in Stordalen, Sweden, and validated at a temperate bog site in Mer Bleue, Canada. A regional evaluation of simulated carbon fluxes, hydrology and vegetation dynamics encompassed additional locations spread across Scandinavia. Simulated peat accumulation was found to be generally consistent with published data and the model was able to capture reported long-term vegetation dynamics, water table position and carbon fluxes. A series of sensitivity experiments were carried out to investigate the vulnerability of high-latitude peatlands to climate change. We found that the Stordalen mire may be expected to sequester more carbon in the first half of the 21st century due to milder and wetter climate conditions, a longer growing season, and the CO2 fertilization effect, turning into a carbon source after mid-century because of higher decomposition rates in response to warming soils.
2018046467 Sapart, Célia J. (Utrecht University, Institute for Marine and Atmospheric Research Utrecht, Utrecht, Netherlands); Shakhova, Natalia; Semiletov, Igor; Jansen, Joachim; Szidat, Sonke; Kosmach, Denis; Dudarev, Oleg; van der Veen, Carina; Egger, Matthias; Sergienko, Valentine; Salyuk, Anatoly; Tumskoy, Vladimir; Tison, Jean-Louis and Rockmann, Thomas. The origin of methane in the East Siberian Arctic shelf unraveled with triple isotope analysis: Biogeosciences, 14(9), p. 2283-2292, illus., 63 ref., 2017.
The Arctic Ocean, especially the East Siberian Arctic Shelf (ESAS), has been proposed as a significant source of methane that might play an increasingly important role in the future. However, the underlying processes of formation, removal and transport associated with such emissions are to date strongly debated. CH4 concentration and triple isotope composition were analyzed on gas extracted from sediment and water sampled at numerous locations on the shallow ESAS from 2007 to 2013. We find high concentrations (up to 500 mM) of CH4 in the pore water of the partially thawed subsea permafrost of this region. For all sediment cores, both hydrogen and carbon isotope data reveal the predominant occurrence of CH4 that is not of thermogenic origin as it has long been thought, but resultant from microbial CH4 formation. At some locations, meltwater from buried meteoric ice and/or old organic matter preserved in the subsea permafrost were used as substrates. Radiocarbon data demonstrate that the CH4 present in the ESAS sediment is of Pleistocene age or older, but a small contribution of highly 14C-enriched CH4, from unknown origin, prohibits precise age determination for one sediment core and in the water column. Our sediment data suggest that at locations where bubble plumes have been observed, CH4 can escape anaerobic oxidation in the surface sediment.
2018047767 Schirrmeister, Lutz (Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Department of Periglacial Research, Potsdam, Germany); Schwamborn, Georg; Overduin, Pier Paul; Strauss, Jens; Fuchs, Margret C.; Grigoriev, Mikhail; Yakshina, Irina; Rethemeyer, Janet; Dietze, Elisabeth and Wetterich, Sebastian. Yedoma ice complex of the Buor Khaya Peninsula (southern Laptev Sea): Biogeosciences, 14(5), p. 1261-1283, illus. incl. 3 tables, strat. col., 100 ref., 2017.
The composition of perennially frozen deposits holds information on the palaeo-environment during and following deposition. In this study, we investigate late Pleistocene permafrost at the western coast of the Buor Khaya Peninsula in the south-central Laptev Sea (Siberia), namely the prominent eastern Siberian Yedoma Ice Complex (IC). Two Yedoma IC exposures and one drill core were studied for cryolithological (i.e. ice and sediment features), geochemical, and geochronological parameters. Borehole temperatures were measured for 3 years to capture the current thermal state of permafrost. The studied sequences were composed of ice-oversaturated silts and fine-grained sands with considerable amounts of organic matter (0.2 to 24 wt%). Syngenetic ice wedges intersect the frozen deposits. The deposition of the Yedoma IC, as revealed by radiocarbon dates of sedimentary organic matter, took place between 54.1 and 30.1 kyr BP. Continued Yedoma IC deposition until about 14.7 kyr BP is shown by dates from organic matter preserved in ice-wedge ice. For the lowermost and oldest Yedoma IC part, infrared-stimulated luminescence dates on feldspar show deposition ages between 51.1 ± 4.9 and 44.2 ± 3.6 kyr BP. End-member modelling was applied to grain-size-distribution data to determined sedimentation processes during Yedoma IC formation. Three to five robust end-members were detected within Yedoma IC deposits, which we interpret as different modes of primary and reworked unconfined alluvial slope and fan deposition as well as of localized eolian and fluvial sediment, which is overprinted by in situ frost weathering. The cryolithological inventory of the Yedoma IC preserved on the Buor Khaya Peninsula is closely related to the results of other IC studies, for example, to the west on the Bykovsky Peninsula, where formation time (mainly during the late Pleistocene marine isotope stages (MIS) 3 interstadial) and formation conditions were similar. Local freezing conditions on Buor Khaya, however, differed and created solute-enriched (salty) and isotopically light pore water pointing to a small talik layer and thaw-bulb freezing after deposition. Due to intense coastal erosion, the biogeochemical signature of the studied Yedoma IC represents the terrestrial end-member, and is closely related to organic matter currently being deposited in the marine realm of the Laptev Sea shelf.
2018047363 Amiri, Seyed Ali Ghoreishian (Norwegian University of Science and Technology, Trondheim, Norway); Grimstad, G.; Kadivar, M. and Nordal, S. Constitutive model for rate-independent behavior of saturated frozen soils: Canadian Geotechnical Journal = Revue Canadienne de Géotechnique, 53(10), p. 1646-1657, illus. incl. 4 tables, 31 ref., October 2016.
The mechanical behavior of frozen soils is strongly affected by the amount of ice. The amount of ice depends on the temperature and the applied mechanical stresses. The influence of ice content and temperature on the mechanical behavior and the coupling effects on the reverse direction can be mentioned as the main difference between frozen and unfrozen soils. In the light of this difference, an elastoplastic constitutive model for describing the stress-strain behavior of saturated frozen soils is proposed. By dividing the total stress into fluid pressure and solid phase stress, in addition to consideration of the cryogenic suction, the model is formulated within the framework of two-stress state variables. The proposed model is able to represent many of the fundamental features of the behavior of frozen soils, such as ice segregation phenomenon and strength weakening due to pressure melting. In the unfrozen state the model becomes a conventional critical state model. Typical predictions of the model for simulating the characteristic trends of the frozen soil behavior is described qualitatively. Model predictions are also compared with the available test results and reasonable agreement is achieved.
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2018048419 Bartsch, Annett (Zentralanstalt für Meteorologie und Geodynamik, Vienna, Austria); Grosse, Guido; Kääb, Andreas; Westermann, Sebastian; Strozzi, Tazio; Wiesmann, Andreas; Duguay, Claude; Seifert, Frank Martin; Obu, Jaroslav; Nitze, Ingmar; Heim, Birgit; Haas, Antoni and Widhalm, Barbara. Examining environmental gradients with remotely sensed data; the ESA globpermafrost project [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9701, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Permafrost cannot be directly detected from space, but many surface features of permafrost terrains and typical periglacial landforms are observable with a variety of EO sensors ranging from very high to medium resolution at various wavelengths. In addition, landscape dynamics associated with permafrost changes and geophysical variables relevant for characterizing the state of permafrost, such as land surface temperature or freeze-thaw state can be observed with space-based Earth Observation. Suitable regions to examine environmental gradients across the Arctic have been defined in a community white paper (Bartsch et al. 2014). These transects have been updated within the ESA DUE GlobPermafrost project. The ESA DUE GlobPermafrost project develops, validates and implements Earth Observation (EO) products to support research communities and international organisations in their work on better understanding permafrost characteristics and dynamics. Prototype product cases will cover different aspects of permafrost by integrating in situ measurements of subsurface properties and surface properties, Earth Observation, and modelling to provide a better understanding of permafrost today. The project will extend local process and permafrost monitoring to broader spatial domains, support permafrost distribution modelling, and help to implement permafrost landscape and feature mapping in a GIS framework. It will also complement active layer and thermal observing networks. Both lowland (latitudinal) and mountain (altitudinal) permafrost issues are addressed. The selected transects and first results will be presented. This includes identified needs from the user requirements survey, a review of existing land surface products available for the Arctic as well as prototypes of GlobPermafrost datasets, and the permafrost information system through which they can be accessed. Bartsch, Annett; Allard, Michel; Biskaborn, Boris Kolumban; Burba, George; Christiansen, Hanne H.; Duguay, Claude R.; Grosse, Guido; Gunther, Frank; Heim, Birgit; Hogstrom, Elin; Kaab, Andreas; Keuper, Frida; Lanckman, Jean-Pierre; Lantuit, Hugues; Lauknes, Tom Rune; Leibman, Marina O; Liu, Lin; Morgenstern, Anne; Necsoiu, Marius; Overduin, Pier Paul; Pope, Allen; Sachs, Torsten; Sejourne, Antoine; Streletskiy, Dmitry A.; Strozzi, Tazio; Ullmann, Tobias; Ullrich, Matthias S.; Vieira, Goncalo; Widhalm, Barbara (2014): Requirements for monitoring of permafrost in polar regions - A community white paper in response to the WMO Polar Space Task Group (PSTG), Version 4, 2014-10-09. Austrian Polar Research Institute, Vienna, Austria, 20 pp, hdl:10013/epic.45648.d001 [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048385 Bartsch, Annett (Zentralanstalt für Meteorologie und Geodynamik, Vienna, Austria); Pointner, Georg; Leibmann, Marina; Dvornikov, Yuri and Khomutov, Artem. Circumpolar patterns of ground-fast lake ice and landscape development [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9626, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Shallow lakes in the Arctic are often associated with thermokarst processes which are characteristic for permafrost environments. They partially or completely freeze-up during winter time what can be observed from space using Synthetic Aperture Radar (SAR) data. Spatial patterns of ground-fast and floating ice relate to geomorphological and hydrological processes, but no circumpolar account of this phenomenon is currently available due to challenges when dealing with the varying observation geometry typical for SAR. An approach using ENVISAT ASAR Wide Swath data (approximately 120 m resolution) has been developed supported by bathymetric measurements in Siberia and eventually applied across the entire Arctic for late winter 2008. In total about 2 Million lake objects have been analyzed considering the boundaries of the Last Glacial Maximum, permafrost zones and soil organic carbon content. Distinct patterns of ground-fast lake ice fraction can be found across the Arctic. Clusters of variable fractions of ground-fast ice occur especially in Yedoma regions of Eastern Siberia and Alaska. This reflects the nature of thaw lake dynamics. Analyses of lake depth measurements from several sites (Alaskan North Slope, Richards Island in Canada, Yamal Peninsula and Lena Delta) suggest that the used method yields the potential to utilize ground-fast lake ice information over larger areas with respect to landscape development, but results need to be treated with care, specifically for larger lakes and along river courses. A combination of general lake features and ground-fast ice fraction may lead to an advanced understanding of landscape patterns and development. Ground-fast ice fraction information may support to some extent the identification of landscape units, for example areas of adjacent lakes with similar patterns (terraces) or areas with mixed ground-fast fractions which indicate different lake development stages. This work was supported by the Austrian Science Fund under Grant [I 1401] and the Russian Foundation for Basic Research Grant 13-05-91001-ANF-a (Joint Russian-Austrian project COLD-Yamal). [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043392 Berteni, Francesca (Universita di Brescia, Dipartimento di Ingegneria Civile, Architettura, Territorio, Ambiente e di Matematica (DICATAM), Brescia, Italy) and Grossi, Giovanna. Water erosion and climate change in a small alpine catchment [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10391, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
A change in the mean and variability of some variables of the climate system is expected to affect the sediment yield of mountainous areas in several ways: for example through soil temperature and precipitation peak intensity change, permafrost thawing, snow- and ice-melt time shifting. Water erosion, sediment transport and yield and the effects of climate change on these physical phenomena are the focus of this work. The study area is a small mountainous basin, the Guerna creek watershed, located in the Central Southern Alps. The sensitivity of sediment yield estimates to a change of condition of the climate system may be investigated through the application of different models, each characterized by its own features and limits. In this preliminary analysis two different empirical mathematical models are considered: RUSLE (Revised Universal Soil Loss Equation; Renard et al., 1991) and EPM (Erosion Potential Method; Gavrilovic, 1988). These models are implemented in a Geographical Information System (GIS) supporting the management of the territorial database used to estimate relevant geomorphological parameters and to create different thematic maps. From one side the geographical and geomorphological information is required (land use, slope and hydrogeological instability, resistance to erosion, lithological characterization and granulometric composition). On the other side the knowledge of the weather-climate parameters (precipitation and temperature data) is fundamental as well to evaluate the intensity and variability of the erosive processes and estimate the sediment yield at the basin outlet. Therefore different climate change scenarios were considered in order to tentatively assess the impact on the water erosion and sediment yield at the small basin scale. Keywords: water erosion, sediment yield, climate change, empirical mathematical models, EPM, RUSLE, GIS, Guerna [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048302 Carrivick, Jonathan L. (University of Leeds, School of Geography, Leeds, United Kingdom) and Heckmann, Tobias. Short-term geomorphological evolution of proglacial systems [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6900, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Proglacial systems are amongst the most rapidly changing landscapes on Earth, as glacier mass loss, permafrost degradation and more episodes of intense rainfall progress with climate change. This presentation addresses the urgent need to quantitatively define proglacial systems not only in terms of spatial extent but also in terms of functional processes. It firstly provides a critical appraisal of prevailing conceptual models of proglacial systems, and uses this to justify compiling data on rates of landform change in terms of planform, horizontal motion, elevation changes and sediment budgets. These data permit us to produce novel summary conceptual diagrams that consider proglacial landscape evolution in terms of a balance of longitudinal and lateral water and sediment fluxes. Throughout, we give examples of newly emerging datasets and data processing methods because these have the potential to assist with the issues of: (i) a lack of knowledge of proglacial systems within high-mountain, arctic and polar regions, (ii) considerable inter- and intra-catchment variability in the geomorphology and functioning of proglacial systems, (iii) problems with the magnitude of short-term geomorphological changes being at the threshold of detection, (iv) separating short-term variability from longer-term trends, and (v) of the representativeness of plot-scale field measurements for regionalization and for upscaling. We consider that understanding of future climate change effects on proglacial systems requires holistic process-based modeling to explicitly consider feedbacks and linkages, especially between hillslope and valley-floor components. Such modeling must be informed by a new generation of repeated distributed topographic surveys to detect and quantify short-term geomorphological changes. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048104 Cochand, Marion (Université Laval, Département de Géologie et de Génie Géologique, Quebec, QC, Canada); Molson, John; Barth, Johannes A. C.; van Geldern, Robert; Lemieux, Jean-Michel; Fortier, Richard and Therrien, René Hydrogeochemical characterisation of groundwater in a small watershed in a discontinuous permafrost zone [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4474, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Impacts of climate change can already be seen in northern regions. However, the influence of increasing temperature and permafrost degradation on groundwater dynamics is still poorly understood. This study aims to improve knowledge on hydrogeological interactions in degrading permafrost environments using hydrogeochemical characterisation of groundwater. This study is being conducted in a small 2-km2 watershed, in a discontinuous permafrost zone located close to the Inuit community of Umiujaq, on the eastern shore of Hudson Bay in northern Québec, Canada. Two aquifers are being investigated, an unconfined shallow sandy aquifer located in the upper part of the watershed, and a deeper confined aquifer in sands and gravels located below the permafrost mounds. Precipitation, stream and surface water as well as ice-rich permafrost lenses were also sampled during field investigations. Various hydrogeochemical tracers including major ions, water stable isotopes (d18OH2O and d2HH2O), carbon phases (DIC, DOC, POC), their stable carbon isotopes (d13C) and dating tracers (radiocarbon, tritium-helium and CFC/SF6) were analyzed. This characterisation has contributed to further understanding groundwater origin, evolution and residence time in the watershed. Preliminary results show that groundwater has a mainly Ca-HCO3 geochemical signature, typical for young and poorly evolved water. Furthermore, sample mineralisation is low, and is likely linked to limited bedrock weathering caused by short residence times, slow reaction rates as well as low levels of dissolved CO2 due to suppressed biological activity in the catchment. Inter-annual variation of major ions in the deeper aquifer is low. All groundwater samples have significant tritium concentrations, around 8.5 TU, reflecting modern recharge. Ice-rich permafrost lenses within the top four meters of permafrost have a water stable isotope signature close to modern precipitation and groundwater. This indicates that either recharge conditions of permafrost ice were similar to current conditions, or freeze-thaw cycles have drawn modern water into the permafrost mounds. The stream appears to be fed by groundwater exfiltrating at the base of permafrost mounds in the lower part of the watershed. Linking this hydrogeochemical characterisation to groundwater and thermal modelling at the watershed and permafrost mound scales will improve our knowledge on hydrogeological interactions in degrading permafrost environments. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043383 Deluigi, Nicola (University of Lausanne, Institute of Earth Surface Dynamics (IDYST), Lausanne, Switzerland); Lambiel, Christophe and Kanevski, Mikhail. Data analysis and mapping of the mountain permafrost distribution [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10372, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
In Alpine environments mountain permafrost is defined as a thermal state of the ground and corresponds to any lithosphere material that is at or below 0 C for, at least, two years. Its degradation is potentially leading to an increasing rock fall activity, rock glacier accelerations and an increase in the sediment transfer rates. During the last 15 years, knowledge on this phenomenon has significantly increased thanks to many studies and monitoring projects. They revealed a spatial distribution extremely heterogeneous and complex. As a consequence, modelling the potential extent of the mountain permafrost recently became a very important task. Although existing statistical models generally offer a good overview at a regional scale, they are not always able to reproduce its strong spatial discontinuity at the micro scale. To overcome this lack, the objective of this study is to propose an alternative modelling approach using three classification algorithms belonging to statistics and machine learning: Logistic regression (LR), Support Vector Machines (SVM) and Random forests (RF). The former is a linear parametric classifier that commonly used as a benchmark classification algorithm to be employed before using more complex classifiers. Non-linear SVM is a non-parametric learning algorithm and it is a member of the so-called kernel methods. RF are an ensemble learning method based on bootstrap aggregating and offer an embedded measure of the variable importance. Permafrost evidences were selected in a 588 km2 area of the Western Swiss Alps and serve as training examples. They were mapped from field data (thermal and geoelectrical data) and ortho-image interpretation (rock glacier inventorying). The dataset was completed with environmental predictors such as altitude, mean annual air temperature, aspect, slope, potential incoming solar radiation, normalized difference vegetation index and planar, profile and combined terrain curvature indices. Aiming at predicting the permafrost occurrence where it is unknown, the mentioned supervised learning techniques inferred a classification function from labelled training data (pixels of permafrost absence and presence). A particular attention was given to the pre-processing of the dataset, with the study of its complexity and the relation between permafrost data and employed environmental variables. The application of feature selection techniques completed this analysis and informed about redundant or valueless predictors. Classification performances were assessed with AUROC on independent validation sets (0.81 for LR, 0.85 with SVM and 0.88 with RF). At the micro scale obtained permafrost maps illustrate consistent results compared to the field reality thanks to the high resolution of the dataset (10 meters). Moreover, compared to classical models, the permafrost prediction is computed without recurring to altitude thresholds (above which permafrost may be found). Finally, as machine learning is a non-deterministic approach, mountain permafrost distribution maps are presented and discussed with corresponding uncertainties maps, which provide information on the quality of the results. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043425 Downer, Charles (U. S. Army Engineer Research and Development Center, Vicksburg, MS) and Wahl, Mark. Conceptualizing peatlands in a physically-based spatially distributed hydrologic model [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10458, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
In as part of a research effort focused on climate change effects on permafrost near Fairbanks, Alaska, it became apparent that peat soils, overlain by thick sphagnum moss, had a considerable effect on the overall hydrology. Peatlands represent a confounding mixture of vegetation, soils, and water that present challenges for conceptualizing and parametrizing hydrologic models. We employed the Gridded Surface Subsurface Hydrologic Analysis Model (GSSHA) in our analysis of the Caribou Poker Creek Experimental Watershed (CPCRW). GSSHA is a physically-based, spatially distributed, watershed model developed by the U.S. Army to simulate important streamflow-generating processes (Downer and Ogden, 2004). The model enables simulation of surface water and groundwater interactions, as well as soil temperature and frozen ground effects on subsurface water movement. The test site is a 104 km2 basin located in the Yukon-Tanana Uplands of the Northern Plateaus Physiographic Province centered on 65°10'N latitude and 147°30'W longitude. The area lies above the Chattanika River floodplain and is characterized by rounded hilltops with gentle slopes and alluvium-floored valleys having minimal relief (Wahrhaftig, 1965) underlain by a mica schist of the Birch Creek formation (Rieger et al., 1972). The region has a cold continental climate characterized by short warm summers and long cold winters. Observed stream flows indicated significant groundwater contribution with sustained base flows even during dry periods. A site visit exposed the presence of surface water flows indicating a mixed basin that would require both surface and subsurface simulation capability to properly capture the response. Soils in the watershed are predominately silt loam underlain by shallow fractured bedrock. Throughout much of the basin, a thick layer of live sphagnum moss and fine peat covers the ground surface. A restrictive layer of permafrost is found on north facing slopes. The combination of thick moss and peat soils presented a conundrum in terms of conceptualizing the hydrology and identifying reasonable parameter ranges for physical properties. Various combinations of overland roughness, surface retention, and subsurface flow were used to represent the peatlands. The process resulted in some interesting results that may shed light on the dominant hydrologic processes associated with peatland, as well as what hydrologic conceptualizations, simulation tools, and approaches are applicable in modeling peatland hydrology. Downer, C. W., Ogden, F. L., 2004. GSSHA: Model to simulate diverse stream flow producing processes. J. Hydrol. Eng. 161-174. Rieger, S., Furbush, C. E., Schoephorster, D. B., Summerfield, H., Jr., Geiger, L. C., 1972. Soils of the Caribou-Poker Creeks Research Watershed, Interior Alaska. Hanover, New Hampshire. Wahrhaftig, C., 1965. Physiographic Divisions of Alaska. Washington, DC. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048320 Hendrickx, Hanne (Ghent University, Geography, Belgium); Delaloye, Reynald; Nyssen, Jan and Frankl, Amaury. Investigating talus slope geomorphology as impacted by permafrost thaw (Valais, Switzerland); stipulating a research framework [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6934, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Climate change is altering temperature regimes and precipitation patterns worldwide. In the European Alps, atmospheric temperatures have risen twice as fast as the global average since 1900, while precipitation regimes are changing as well. Snow cover duration and extent has significantly decreased in the Swiss Alps, mainly due to earlier spring melt and rise in winter temperatures. Moreover, future projections predict a continuation of these trends. Spatial distribution and thermal properties of permafrost are highly influenced by ground surface conditions (snow and vegetation) and air temperature. Climate induced permafrost degradation is, therefore, expected. While alpine permafrost research has mainly focused on rock glaciers, less attention has been given to talus slopes. The latter are subjected to different kinds of slope processes such as debris flows, solifluction, permafrost creep, avalanches and rock fall. These processes are especially effective under a changing periglacial climate. Therefore, it is important to study permafrost distribution in these talus slopes, since it is believed to have large influence on slope stability. In this study, permafrost distribution will be mapped on several talus slope segments (10-40 ha) using geomorphological evidence, temperature data and measuring electrical resistivity tomography (ERT) profiles in addition to already existing data. The current dynamics of the study area will be studied by constructing detailed 3D models, using ground based and aerial photography (Unmanned Aerial Vehicles, UAV) and the Structure-from-Motion method (SfM). The resulting Digital Elevation Models (DEM) will be used to quantify and understand the current geomorphological processes acting on these talus slopes. Historical aerial and terrestrial photographs will be used to give an idea about the magnitude and frequency of past geomorphic processes (e.g. debris flows). Historical and current dynamics can then be compared and contrasted with permafrost occurrence. By doing so, this study will answer following question: To which extent will climate-induced permafrost degradation impact geomorphological processes on talus slopes?. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043301 Hohensinn, Roland (Eidgenössische Technische Hochschule Zürich, Institute of Geodesy and Photogrammetry, Switzerland) and Geiger, Alain. Rapid detection of small movements with GNSS Doppler observables [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9433, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
High-alpine terrain reacts very sensitively to varying environmental conditions. As an example, increasing temperatures cause thawing of permafrost areas. This, in turn causes an increasing threat by natural hazards like debris flow (e.g. rock glaciers) or rockfalls. The Institute of Geodesy and Photogrammetry is contributing to alpine mass-movement monitoring systems in different project areas in the Swiss Alps. A main focus lies on providing geodetic mass-movement information derived from GNSS static solutions on a daily and a sub-daily basis, obtained with low-cost and autonomous GNSS stations. Another focus is set on rapidly providing reliable geodetic information in real-time i.e. for an integration in early warning systems. One way to achieve this is the estimation of accurate station velocities from observations of range rates, which can be obtained as Doppler observables from time derivatives of carrier phase measurements. The key for this method lies in a precise modeling of prominent effects contributing to the observed range rates, which are satellite velocity, atmospheric delay rates and relativistic effects. A suitable observation model is then devised, which accounts for these predictions. The observation model, combined with a simple kinematic movement model forms the basis for the parameter estimation. Based on the estimated station velocities, movements are then detected using a statistical test. To improve the reliablity of the estimated parameters, another spotlight is set on an on-line quality control procedure. We will present the basic algorithms as well as results from first tests which were carried out with a low-cost GPS L1 phase receiver. With a u-blox module and a sampling rate of 5 Hz, accuracies on the mm/s level can be obtained and velocities down to 1 cm/s can be detected. Reliable and accurate station velocities and movement information can be provided within seconds. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043385 Koehl, Mathieu (Université de Strasbourg-CNRS-Institut National des Sciences Appliquees de Strasbourg, Strasbourg, France); Eschbach, David; Grussenmeyer, Pierre; Schmitt, Laurent and Guillemin, Samuel. Diachronic 3D modelling to monitor fluvial morphodynamics in a restored hydrosystem (Upper Rhine, Rohrschollen island) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10377, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The Rohrschollen artificial island is a Natural Reserve located 8 km South-East the city of Strasbourg. The island results from several engineering works (correction and canalization) lead on the reach since the beginning of the 19th century to improve flood control, agriculture, navigation and to produce hydropower. Consequently, the main channel of the island (called old channel) was upstream disconnected, hydromorphological functioning was altered (narrowing and clogging, decreasing of morphodynamics and of surface water-groundwater exchanges...) and specific alluvial biodiversity declined drastically. In the framework of a LIFE+ European program, an ambitious restoration project was carried out by the city of Strasbourg with the aims to restore hydromorphological dynamics and improve typical ecological characteristics of the hydrosystem: bedload dynamics, channel mobility, surface water-groundwater exchanges and renewal of pioneer ecosystems... . To achieve these objectives, a new upstream channel was dug in the floodplain and a large floodgate was built in order to reconnect the old channel with the Rhine. Water input is about 2 m3.s-1 and could attain a maximum of 80 m3.s-1 during Rhine's floods. This new hydrological dynamics allowed to recover dynamic floods and high morphological activities, especially on the new channel which was intentionally undersized. As part of the partnership between the LIVE laboratory and the INSA of Strasbourg, a monitoring of fluvial morphodynamics was carried out, based on a diachronic 3D modelling survey. Focused on three bending sectors of the channel, the initial state was realized in 2014, before the first flood, by a geo-referenced 3D model recorded by Terrestrial Laser Scanning (TLS) and panoramic images. This method was used as a 3D digital reference model and setup by differential GNSS techniques. The long-term diachronic monitoring was based on terrestrial photogrammetry surveys followed by dense matching techniques after each flood. This low cost method has the advantage to be very fast in the acquisition. Bathymetrical data were collected by tacheometry and total station on the whole channel. Based on a diachronic comparison of the obtained models, morphological changes were analyzed and volumes of eroded/deposed sediments were quantified in detailed morphological budgets (elementary 20 m long sections). The 3D models will be complementary with other field techniques like the tracking of passive integrated transponders, active layer evolution and floodplain deposition survey. The results show the interest of the diachronic 3D modelling methods to estimate the intensity of the morphodynamic adjustments of the restored hydrosystem. These methods allows to (i) refine the understanding of the river dynamics on fine scale (sections), (ii) quantify sedimentary budgets on large scale (channel) and, (iii) predict evolutionary perspectives on the middle term. The PICO reports the various stages of the implementation of a topographic survey of the channel as well as an overview of the obtained results, in particular a morphological diachronic comparison of the channel. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043169 Lehmkuhl, Frank (RWTH Aachen University, Department of Geography, Aachen, Germany). Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-7922, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
In the cold and continental areas of Central and High Asia periglacial landform assembles, sediment structures and processes are mainly influenced and determined by the existence of soil humidity during the freeze-thaw cycles. This results in cryogenic processes and periglacial landforms such as earth hummocks, patterned ground or solifluction. The distribution of rock glaciers as clear indicators of permafrost is also determined by rock fall or moraine debris composed of large boulders (e.g. granite). Periglacial features and landforms have been used to reconstruct past climatic conditions, e.g. relict involutions and ice-wedge casts provide evidence for the distribution of former permafrost, e.g. for the Last Glacial Maximum. Past temperatures, e.g. mean annual air temperatures, can be estimated from these periglacial features. Examples from late Holocene solifluction activity in the Altai, Khangai, and northeastern Tibetan Plateau show different intensity of solifluction processes during the late Holocene and Little Ice Age by decrease of temperature and more soil humidity. The distribution of past permafrost in some regions is still a matter of debate due to different interpretations of sediment structures: Sometimes features described as ice-wedge casts may be caused by roots or desiccation cracks due to drying of clay rich sediments. Seismically deformed unconsolidated deposits (seismites) can also be misinterpreted as periglacial involutions. The lack of certain landform assemblages and sediment structures does not necessarily mean that the area had no permafrost as moisture conditions also to a large degree govern periglacial landform generation and not only temperature. They can be ordered in Central Asia as follows (from highest moisture availability to lowest): solifluction-rock glacier-permafrost involutions-ice wedge casts-sand wedge casts. Reference: LEHMKUHL, F. (2016): Modern and past periglacial features in Central Asia and their implication for paleoclimate reconstructions. Progress in Physical Geography 40: 369-391. DOI:10.1177/0309133315615778 [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043307 Ploum, Stefan (Sveriges Lantbruksuniversitet, Sweden); Lyon, Steve; Teuling, Ryan and van der Velde, Ype. Soil thaw effects on river discharge recessions of a subarctic catchment [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9449, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Thawing permafrost in circumpolar regions is likely to change subsurface hydrology. In high latitude areas continuous permafrost is expected to partially thaw leading to sporadic permafrost with deeper groundwater flow paths. Moreover, freeze-thaw cycles of the shallow subsurface are likely to increase. River discharge recession analysis can be particularly useful to understand the hydrological effects of a thawing Arctic. Here we examine river discharge recessions of the Abiskojokka, a 560 km2 watershed with sporadic permafrost, using a river discharge record of 30 years (1985 - 2015). Snow observation records were used to separate river recessions in snowmelt and snowfree periods. We found significant differences between recessions during the snowmelt and snowfree seasons. During the snowmelt, recessions were close to linear (b=1.11), while during the snowfree period, recessions were more non-linear (b=1.54). Typically, non-linearity has been found to increase with discharge magnitude, while we observed the opposite (snowfree periods tend to have lower discharges than the snowmelt periods). We explain these contrasting results by hypothesizing that increased connectivity (increasing magnitude and number of water flow paths) between groundwater and stream leads to higher non-linearity. In temperate catchments without frozen soils, connectivity tends to increase with increasing discharge. In contrast, in Arctic systems, where soils are frozen, connectivity between groundwater and stream is limited. Therefore, thawing of frozen soils is expected to increase connectivity and thus non-linearity of river discharges. We tested this hypothesis with a detailed analysis of all spring flood recessions. Years with cold soil temperatures (b=1.08) and years with a below median snowpack depth were found to have progressively linear slopes (b=1.08 and 1.01 respectively). On the other hand, years with warm soil conditions show increasingly non-linear recessions (b=1.67). Although limited in spatial extent, these results further support our connectivity hypothesis, which predicts increasing non-linearity of river discharges (higher discharge peaks and lower low flows under the same precipitation regime) as permafrost thaws. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048180 Scapozza, Cristian (University of Applied Sciences and Arts of Southern Switzerland (SUPSI), Department for Environment Constructions and Design, Canobbio, Switzerland); Bruder, Andreas; Domenici, Mattia; Lepori, Fabio; Pera, Sebastian; Pozzoni, Maurizio; Rioggi, Stefano and Colombo, Luca. Monitoring mountain lakes in a changing Alpine cryosphere; the Lago Nero project (Ticino, Switzerland) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-6208, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Mountain lakes and their catchments of the Alpine cryosphere are facing global pressures including climate warming and deposition of atmospheric pollutants. Due to their remoteness, often low buffer capacities and sensitive biotic communities, alpine lake catchments are particularly well suited as sentinels of environmental change. Lago Nero is the object of an intensive survey, aimed at developing predictive models of catchment-wide ecosystem responses to environmental change (Bruder et al. 2016). Lago Nero is located at the head of Val Bavona (Canton Ticino, southern Switzerland), in a southwest-facing catchment, with altitude ranging from 2385 to 2842 m asl. The substrate is dominated by gneissic bedrock with patches of grassy vegetation and shallow soils. The catchment is snow-covered approximately from November to May. For a similar period, the lake is ice-covered. Lago Nero is an oligotrophic, soft-water lake with a surface of approximatively 13 ha and a maximal depth of 73 m. According to the regional model of potential permafrost distribution in the southern Swiss Alps (Scapozza & Mari 2010), the presence of discontinuous permafrost is probable in almost the entire surface of the catchment covered by loose debris. A direct evidence of permafrost occurrence is the presence of a small active/inactive rock glacier in the south-eastern part of the catchment (front altitude: 2560 m asl). Monitoring of the site began in summer 2014, with an initial phase aimed at developing and testing methodologies and at evaluating the suitability of the catchment and the feasibility of the monitoring program. The intensive survey at Lago Nero measures a wide array of ecosystem responses, including runoff quantity and chemistry, catchment soil temperature (also on the rock glacier) and composition of terrestrial vegetation. Sampling frequency depends on the parameter measured, varying from nearly continuous (e.g. runoff and temperature) to five-year intervals (e.g. soil and vegetation). First results suggest that Lago Nero is particularly sensitive to changes in the cryosphere, particularly concerning thickness of snow cover, snowmelt date and duration, and length of ice-free period of the lake surface. Probable storage of ground ice during the 1966-1985 period (deduced from the nearby Basòdino Glacier) and its significant melting in the last decades may explain the high amounts of sulphur measured in the outflow of the rock glacier. High levels of sulphur are likely to have ecological effects on the sensitive biota of the Lago Nero catchment, for instance by retarding the recovery from past acidification. REFERENCES Bruder A., Lepori F., Pozzoni M., Pera S., Scapozza C., Rioggi S., Domenici M. & Colombo L. (2016). Lago Nero - a new site to assess the effects of environmental change on high-alpine lakes and their catchments. In: S. Kleemola & M. Forsius (eds.), 25th Annual Report 2016. Convention on Long-range transboundary air pollution. Reports of the Finnish Environments Institute 29: 52-56. Scapozza C. & Mari S. (2010). Catasto, caratteristiche e dinamica dei rock glacier delle Alpi Ticinesi. Bollettino della Societa ticinese di Scienze naturali 98: 15-29. [URL: http://repository.supsi.ch/2152/] [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018045058 Schwamborn, Georg (Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung, Potsdam, Germany); Stapel, Janina G.; Mangelsdorff, Kai; Walz, Josefine; Knoblauch, Christian; Wetterich, Sebastian and Schirrmeister, Lutz. Soil carbon unlocked from MIS 5 to MIS 1 aged North Siberian permafrost; state and fate of decomposition [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10255, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
At Bol'shoy Lyakhovsky, New Siberian Archipelago, multiple permafrost cores were obtained providing a Late Quaternary environmental record with deposits from marine isotope stages MIS 5 to MIS 1. This exceptionally long record is used to evaluate the stored potential of the freeze-locked organic matter (OM) to serve as substrate provider for greenhouse gas producing microorganisms. We relate modern signals of OM degradation from MIS 1 deposits to previous glacial-time deposits (MIS 4 and MIS 3) and to interglacial deposits (MIS 5), which may serve as an analogue for a future Arctic warmer than modern. From the oldest to the youngest, the composite record includes re-frozen MIS 5 lake deposits (sandy silt), floodplain deposits (sandy silt) from MIS 4, Ice Complex (i.e. Yedoma) deposits from MIS 4 to 3 (sandy silt), and alas deposits (sandy silt) from a drained and re-frozen thermokarst basin with MIS 1 ages. Whereas glacial-time deposits (MIS 4 and MIS 3) are fairly ice-rich with a median at 43 wt% ice content, interglacial deposits (MIS 5 and MIS 1) are moderately ice-rich with a median at 31 wt% ice content. In terms of total organic carbon content glacial-time deposits have moderate values with a median at 2.4 wt% and interglacial deposits have low values with a median at 0.4 wt%. Deposits from MIS 4 and MIS 3 possess an increased aliphatic character and therefore higher OM quality in terms of biodegradation compared to deposits from MIS 5 and MIS 1. The strongest primal and future substrate potential is stored within the glacial-time deposits, especially in those layers deposited during environmental conditions with increased moisture. The interstadial MIS 3 deposits hold the highest concentrations of pore-water acetate, which serve as optimal substrate for greenhouse gas generating microorganisms once it is unlocked from the perennially frozen ground. MIS 3 deposits also contain the highest concentrations of organic acids ester-bound to the organic matrix, implying an increased and still stored future substrate pool. In contrast, interglacial MIS 5 deposits are distinctly depleted in both primal and future substrate pools, whereas MIS 1 substrates are partly depleted in that sense. Incubation experiments reveal that moderate CO2 and low CH4 concentrations can be generated from the deposits (after 285 days at 4°C). MIS 4 and MIS 3 deposits produce markedly higher amounts of aerobic and anaerobic CO2 than MIS 5 deposits. CH4 production was only observed in MIS 5 and in a few MIS 1 samples. This points to the fact that greenhouse gas production potentials depend on particular soil properties and environmental conditions during OM deposition and the degree of degradation prior to incorporation into permafrost. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043462 Tanarro, Luis M. (Universidad Complutense de Madrid, Madrid, Spain); Palacios, David; Andres, Nuria; Fernández, Jose M. and Zamorano, Jose J. Surface morphology and dynamic of debris-covered and rock glaciers in the Trollaskagi Peninsula (northern Iceland) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10534, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The Trollaskagi peninsula is located in north central Iceland, between the meridians of 19°30'W and 18°10'W, limited by the Skagafjordur fiord to the west and the Eyjafjordur fiord to the east, jutting out into the North Atlantic to latitude 66°12'N and linked to the central Icelandic highlands to the south. There are over a hundred debris-covered and rock glaciers at its valley heads, some of which have been studied in detail regarding their dynamics and activity (vid. summary in Andres et al. 2016). This work analyses block displacements and changes in the surface morphology of the Fremri-Grjotardalur rock glacier (65°43'N 19°W, 1,245 m) and the Holadalsjokull debris-covered glacier (65°42'N; 18°57'W, 1,330 m), located in the centre of Trollaskagi peninsula. A Digital Photogrammetric WorkStation-Digi3d.NET-(DPWS Digi3d) has been used in this study to compare the evolution of these landforms in aerial photographs taken at different years (1946, 1980, 1985 and 1994) and a 2000 orthophoto. In our study, we have obtained high-accuracy multitemporal stereo-models (RMSExyz between 0.153 and 0.251 m) by using DPWS Digi3d. The 3D digital stereo-photogrammetric restitution of aerial photographs from the years 1980 and 1994 allows us to compare high resolution digital elevation models (derived from contour lines at 2 m interval) and obtain location differences of geomorphological surface features (ridges, transverse and longitudinal furrows, front and lateral crests, flow lines, thermokarst depressions) and many control points in large blocks. The results obtained of surface horizontal and vertical displacements of large blocks for the period 1980-1994 at the Holadalsjokull debris-covered glacier show an average velocity of 0.33 m yr 1 and -0.72 m respectively. However, the results obtained of the displacement of lateral and front crests reveal an advance of 14.84 m for the period 1946-2000 (0.27 m yr 1). Between 1980 and 1994 these features have only been displaced by 2.8 m, indicating a velocity lower than 0.20 m yr 1. The limited advance of the crests seems to be related to a process of surface lowering, as they show a decrease of their average altitude by 0.6 m (0.04 m yr 1). The results obtained at the Fremri-Grjotardalur rock glacier show that the horizontal displacement of blocks is very low, less than 0.2 m yr 1, with a decrease in their average altitude by 0.37 m. The low rates of block displacement and monitored features, as well as the important process of surface lowering observed in these landforms, may indicate that widespread melting is the most important activity occurring at the debris-covered and rock glaciers in Trollaskagi. Beside the slow movement at the Holadalsjokull debris-covered glacier and the lack of movement at Fremri-Grjotardalur, no changes have occurred in their surface morphology in the last 54 years, except for the formation of some depressions due to collapse in the former. Research funded by Deglaciation project (CGL2015-65813-R), Government of Spain References Andres, N., Tanarro, L. M., Fernandez, J. M. and Palacios, D. 2016. The origin of glacial alpine landscape in Trollaskagi Peninsula (North Iceland). Cuadernos de investigacion Geografica, 42 (2): 341-368. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043422 Tanarro, Luis M. (Universidad Complutense de Madrid, Madrid, Spain); Palacios, David; Zamorano, Jose J. and Andres, Nuria. Detailed geomorphological mapping of debris-covered and rock glaciers in the Holar area, Trollaskagi Peninsula (northern Iceland) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-10451, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Most studies conducted on rock and debris-covered glaciers only include simplified geomorphological maps representing main units (ridges, furrows, front, and thermokarst depressions). The aim of this study is to develop a detailed geomorphological mapping of the Holadalsjokull debris-covered glacier (65°42'N; 18°57'W) and the Fremri-Grjotardalur rock glacier (65°43'N; 19°W), located near Holar, a village in the central area of the Trollaskagi peninsula (northern Iceland). The mapping process has been conducted using standard stereo-photointerpretation of aerial photographs and stereo-plotting of a topographic map at 1:2000 scale. Also, landforms have been represented in different transects. Lastly, the geomorphological map has been designed using the elevation digital model, and a 3D pdf file has been generated, allowing for better viewing and understanding the different units and their modelling. The geomorphological mapping of the Holadalsjokull debris-covered glacier and the Fremri-Grjotardalur rock glacier represents the prominent walls of their valley heads and their summits, which form a flat highland at 1,200-1,330 metres above sea level, covered by blockfield and patterned ground features. Rockfall and slide landforms are common processes at the foot of these 100-170 metre-high cirque-walls. Debris-covered glaciers and rock glaciers are born right under these walls, building up a spoon-shaped hollow around glacial ice, surrounded by young moraine ridges at their fronts. The dominant features in the Holadalsjokull debris-covered glacier are large longitudinal ridges and furrows, stretching over 1.5 km in length in the central and western areas. Medium-sized thermokarst depressions (between 15-40 metres in diameter), often running parallel to the furrows, dot the surface of the debris-covered glacier. Parallel alternate ridges and furrows can be seen near the snout. Ridges are rugged and fall around 30-40 metres, with over 30 degree slopes, whereas furrows have smoother hillsides. The snout of the debris-covered glacier is around 900 m high. Several units of rock glaciers from different overlapping ages can be distinguished in the Fremri-Grjotardalur cirque. Deep and meandering furrows have developed in the contact areas between the main lobes. The lobes of the youngest rock glaciers, located at the cirque head, reach a length of between 0.5 km and 1 km. Their morphology changes from their rooting zone, with alternate smooth furrows and ridges extending towards their front, where steep ridges and furrows appear, and ends in a steep front between 896 and 922 m high. These rock glaciers overlap one another on a fossil rock glacier, rising another 400 m until they reach a height of 850 m. Research funded by Deglaciation project (CGL2015-65813-R), Government of Spain [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048428 Walvoord, Michelle (U. S. Geological Survey, Lakewood, CO); Voss, Clifford; Ebel, Brian and Minsley, Burke. Evaluating permafrost thaw vulnerabilities and hydrologic impacts in boreal Alaska (USA) watersheds by integrating field data and cryohydrogeologic modeling [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9722, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Permafrost environments undergo changes in hydraulic, thermal, chemical, and mechanical subsurface properties upon thaw. These property changes must be considered in addition to alterations in hydrologic, thermal, and topographic boundary conditions when evaluating shifts in the movement and storage of water in arctic and sub-arctic boreal regions. Advances have been made in the last several years with respect to multiscale geophysical characterization of the subsurface and coupled fluid and energy transport modeling of permafrost systems. Ongoing efforts are presented that integrate field data with cryohydrogeologic modeling to better understand and anticipate changes in subsurface water resources, fluxes, and flowpaths caused by climate warming and permafrost thawing. Analyses are based on field data from several sites in interior Alaska (USA) that span a broad north-south transition from continuous to discontinuous permafrost. These data include soil hydraulic and thermal properties and shallow permafrost distribution. The data guide coupled fluid and energy flow simulations that incorporate pore-water liquid/ice phase change and the accompanying modifications in hydraulic and thermal subsurface properties. Simulations are designed to assess conditions conducive to active layer thickening and talik development, both of which are expected to affect groundwater storage and flow. Model results provide a framework for identifying factors that control the rates of permafrost thaw and associated hydrologic responses, which in turn influence the fate and transport of carbon. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018043283 Westermann, Sebastian (University of Oslo, Department of Geosciences, Oslo, Norway); Obu, Jaroslav; Aalstad, Kristoffer; Bartsch, Annett and Kaab, Andreas. ESA GlobPermafrost; mapping the extent and thermal state of permafrost with satellite data [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-9396, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The ESA GlobPermafrost initiative (2016-2019) aims at developing, validating and implementing information products based on remote sensing data to support permafrost research. Mapping of permafrost extent and ground temperatures is conducted at 1 km scale using remotely sensed land surface temperatures (MODIS), snow water equivalent (ESA GlobSnow) and land cover (ESA CCI landcover) in conjunction with a simple ground thermal model (CryoGrid 1). The spatial variability of the ground thermal regime at scales smaller than the model resolution is explicitly taken into account by considering an ensemble of realizations with different model properties. The approach has been tested for the unglacierized land areas in the North Atlantic region, an area of more than 5 million km2. The results have been compared to in-situ temperature measurements in more than 100 boreholes, indicating an accuracy of approximately 2.5 °C. Within GlobPermafrost, the scheme will be extended to cover the entire the circum-polar permafrost area. Here, we provide an evaluation of the first prototype covering "lowland" permafrost areas north of 40 latitude (available on www.globpermafrost.info in early 2017). We give a feasibility assessment for extending the scheme to global scale, including both mountain and Antarctic permafrost. Finally, we discuss the potential and limitations for estimating changes of permafrost extent on decadal timescales. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018048877 Burkov, P. (National Research Tomsk Polytechnic University, Tomsk, Russian Federation); Yan'nan, Van and Burkova, S. Stress-strain analysis of pipelines laid in permafrost: in XX international scientific symposium of students, postgraduates and young scientists on Problems of geology and subsurface development, IOP Conference Series. Earth and Environmental Science, 43(1), 012080, illus., 11 ref., September 2016. Meeting: International scientific symposium; Problems of geology and subsurface development, April 4-8, 2016, Tomsk, Russian Federation.
Increasing reliability of pipelines becomes a real challenge at all stages: design, construction and operation of pipeline systems. It is very important to determine the behaviour of the constructed pipeline under the operational and environmental loads using the design model in accordance with that one adopted in the rules and regulations. This article presents the simulation of pipeline in permafrost. The evaluation of the stress-strain state is given herein and the areas of the stress concentration are detected with the account for different loads occurred during the pipeline operation. Information obtained from the assessment of the stress-strain state of the pipeline allows determining sections in pre-emergency state (even before damages) and take all the necessary measures for eliminating them, thus increasing the pipeline system reliability. It is shown that the most critical pipeline cross-section is observed at the point of transition from one environment to another. The maximum strains decrease the level of the pipeline reliability. The finite element model is presented to determine the pipeline sections in pre-emergency state. Copyright Published under license by IOP Publishing Ltd
2018048876 Chukhareva, N. (Tomsk Polytechnic University, Tomsk, Russian Federation); Rudachenko, A. and Chekhlov, A. Measures to limit subsidence of underground oil pipeline in insular permafrost: in XX international scientific symposium of students, postgraduates and young scientists on Problems of geology and subsurface development, IOP Conference Series. Earth and Environmental Science, 43(1), 012079, illus. incl. 1 table, 8 ref., September 2016. Meeting: International scientific symposium; Problems of geology and subsurface development, April 4-8, 2016, Tomsk, Russian Federation.
In this paper optimal solutions to limit the subsidence of underground oil pipeline in insular permafrost are proposed. Copyright Published under license by IOP Publishing Ltd
2018048839 Iskorkina, A. A. (National Research Tomsk Polytechnic University, Institute of Natural Resources, Tomsk, Russian Federation); Isaev, V. I. and Fomin, A. N. Influences of Neo-Pleistocene permafrost on thermal history of petromaternal Lower Jurassic Togur suite (Tomsk region): in XX international scientific symposium of students, postgraduates and young scientists on Problems of geology and subsurface development, IOP Conference Series. Earth and Environmental Science, 43(1), 012009, illus. incl. 4 tables, geol. sketch maps, 10 ref., September 2016. Meeting: International scientific symposium; Problems of geology and subsurface development, April 4-8, 2016, Tomsk, Russian Federation.
Based on paleotemperature modeling, evaluation of Neo-Pleistocene permafrost rock thickness impact on geothermal regime of the petromaternal Togur deposits has been performed within the territory of oil fields of the Tomsk region (the southeast of Western Siberia). It has been stated that paleopermafrost with the thickness of about 300 m must be considered for appropriate reconstruction of geothermal history of petromaternal rocks in the southeast areas of West Siberia. This condition is relevant to a consistent consideration of thermal history of maternal deposits in course of assessment of resources by a volumetric-genetic method. Copyright Published under license by IOP Publishing Ltd
2018048869 Strokova, L. A. (Tomsk Polytechnic University, Tomsk, Russian Federation) and Teterin, E. A. Identification and assessment of geohazards affecting pipelines and urban areas: in XX international scientific symposium of students, postgraduates and young scientists on Problems of geology and subsurface development, IOP Conference Series. Earth and Environmental Science, 43(1), 012051, illus. incl. 2 tables, 8 ref., September 2016. Meeting: International scientific symposium; Problems of geology and subsurface development, April 4-8, 2016, Tomsk, Russian Federation.
The paper addresses methods and criteria of risk assessment associated with land subsidence threatening pipelines, buildings, and constructions. Currently, there are some practical issues relating to geohazards that should be taken into account while constructing a pipeline. The article provides comparison data on the effects of Spitak earthquake and the natural disaster in Neftegorsk in terms of geohazards impact on the pipeline systems. The suggested risk assessment procedure embraces a wide range of aspects: from soil properties to economic and management issues. Copyright Published under license by IOP Publishing Ltd
2018046269 Chen, L. (Tohoku University, Institute of Fluid Science, Sendai, Japan); Yamada, H.; Kanda, Y.; Sasaki, H.; Okajima, J.; Iga, Y.; Komiya, A. and Maruyama, S. Study of methane hydrate as a future energy resource; low emission extraction and power generation: in 2016 international conference on New energy and future energy systems (Kyriakopoulos, Grigorios L., editor), IOP Conference Series. Earth and Environmental Science, 40(1), Paper no. 012074, illus., 18 ref., August 2016. Meeting: 2016 international conference on New energy and future energy systems, Aug. 19-22, 2016, Beijing, China.
With the fast increase of world energy consumption in recent years, new and sustainable energy sources are becoming more and more important. Methane Hydrate is one promising candidate for the future energy supply of humankind, due to its vast existence in permafrost regions and near-coast seabed. This study is focused on the effective low emission utilization of methane hydrate from deep seabed. The Nankai Trough of Japan is taken as the target region in this study for methane hydrate extraction and utilization system design. Low emission system and power generation system with CCS (Carbon Capture and Sequestration) processes are proposed and analyzed for production rate and electricity generation efficiency problem study. It is found that the gas production price can reach the current domestic natural gas supply price level if the production rate can be improved. The optimized system is estimated to have power efficiency about 35%. In addition, current development and analysis from micro-to-macro scale methane hydrate production and dissociation dynamics are also discussed into detail in this study. Copyright Published under licence by IOP Publishing Ltd
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