February 2018 Permafrost 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 2011. The Bibliography is searchable at : www.coldregions.org.
Have a look for your favorite topic, location and/or author. For example, a search using “permafrost” and “Barrow” found 146 references dating back to at least 1952 and up to the more recent September 2015 Seventh Canadian Permafrost Conference.
The individual Monthly Permafrost Alerts are found on the US Permafrost Association website : http://www.uspermafrost.org/monthly-alerts.shtml.
2018 Permafrost Alert Sponsors
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2018025364 Wang Yibo (Lanzhou University, College of Earth and Environment Sciences, Lanzhou, China); Sun Zhe and Sun Yan. Effects of a thaw slump on active layer in permafrost regions with the comparison of effects of thermokarst lakes on the Qinghai-Tibet Plateau, China: Geoderma, 314, p. 47-57, illus. incl. 5 tables, geol. sketch map, 48 ref., March 15, 2018.
In this study, we monitored a thaw slump in the permafrost region of the Qinghai-Tibet Plateau in China, including its thaw settlement and solifluction creep characteristics, and analyzed the change in soil properties and hydrothermal process in the active layer. In addition, the change of the thaw slump active layer was compared with the change of the active layer in lakeshore areas, which were affected by thermokarst lakes, to study the relationship between thaw slump and thermokarst lake. Results showed that thaw slump solifluction creep displacement mainly occurred at the top 50 cm surface soil layer. Under the influence of the thaw slump, the active layer soil bulk density increases gradually along the slope; fine soil particles and soil organic carbon first deposit at the top 30-40 cm of the active layer at gentle slope area, and then are significantly leached at the slope bottom. Since the effect of thaw slump weakens the buffering effects of the active layer on heat transfer, the active layer gradually deepened along the slope and the ablation of the underlying ice-rich permafrost increased, which resulted in the increase of the thaw settlement. Concurrently, a large amount of thaw water from the thawed permafrost was released to the active layer, resulting in overland flow at the front part of the gentle slope area and ponding depression at the slope bottom. The active layer changes of the thaw slump and those of thermokarst lake shore were very similar. These results suggest that active layer soil properties were changed by thaw slump, leading to the increase in underlying permafrost ablation, causing large amounts of thaw water accumulating at poorly drained sites, to form sparse small-sized thermokarst lakes. For some large thermokarst lakes adjacent to a small thaw slump, lake coastal erosion caused the thaw slump, and further evolution of the thaw slump resulted in the changes of lakeshore active layer.
2018023794 Ala-aho, Pertti (University of Aberdeen, Northern Rivers Institute, United Kingdom); Soulsby, C.; Pokrovsky, O. S.; Kirpotin, S. N.; Karlsson, J.; Serikova, S.; Vorobyev, S. N.; Manasypov, R. M.; Loiko, S. and Tetzlaff, D. Using stable isotopes to assess surface water source dynamics and hydrological connectivity in a high latitude wetland and permafrost influenced landscape: Journal of Hydrology, 556, p. 279-293, illus. incl. sketch map, 110 ref., January 2018. Includes appendices.
Climate change is expected to alter hydrological and biogeochemical processes in high-latitude inland waters. A critical question for understanding contemporary and future responses to environmental change is how the spatio-temporal dynamics of runoff generation processes will be affected. We sampled stable water isotopes in soils, lakes and rivers on an unprecedented spatio-temporal scale along a 1700 km transect over three years in the Western Siberia Lowlands. Our findings suggest that snowmelt mixes with, and displaces, large volumes of water stored in the organic soils and lakes to generate runoff during the thaw season. Furthermore, we saw a persistent hydrological connection between water bodies and the landscape across permafrost regions. Our findings help to bridge the understanding between small and large scale hydrological studies in high-latitude systems. These isotope data provide a means to conceptualise hydrological connectivity in permafrost and wetland influenced regions, which is needed for an improved understanding of future biogeochemical changes.
2018023790 Deuerling, Kelly M. (University of Florida, Department of Geological Sciences, Gainesville, FL); Martin, Jonathan B.; Martin, Ellen E. and Scribner, Cecilia A. Hydrologic exchange and chemical weathering in a proglacial watershed near Kangerlussuaq, West Greenland: Journal of Hydrology, 556, p. 220-232, illus. incl. 1 table, sketch map, 76 ref., January 2018. Includes appendices.
The exchange of proglacial river water with active layer pore water could alter water chemical compositions in glacial outwash plains and oceanic solute fluxes. To evaluate effects of this exchange, we sampled Watson River and adjacent pore water during the 2013 melt season at two sandurs in western Greenland; one in Sandflugtdalen and the other near the confluence with Sondre Stromfjord. We measured temperature, specific conductivity, and head gradients between the river and bank over a week-long period at Sandflugtdalen, as well as sediment hydraulic conductivity and chemical compositions of waters from both sites. Specific conductivity of pore water is four to ten times greater than river water as solutes are concentrated from weathering reactions, cryoconcentration, and evaporation. Pore water compositions are predominantly altered by carbonate dissolution and sulfide mineral oxidation. High concentrations of HCO3 and SO4 result from solute recycling and dissolution of secondary Ca-Mg carbonate/sulfate salts initially formed by near-surface evaporation in the summer and at depth by freeze-in of the active layer and cryoconcentration in the winter. High hydraulic conductivity (10-5 to 10-4 m/s) and diurnal fluctuations of river stage during our study caused exchange of river and pore water immediately adjacent to the river channel, with a net loss of river water to the bank. Pore water >6 m from the river continuously flowed away from the river. Approximately 1-8% of the river discharge through the Sandflugtdalen was lost to the river bank during our 6.75 day study based on calculations using Darcy's Law. Although not sampled, some of this water should discharge to the river during low river stage early and late in the melt season. Elevated pore water solute concentrations in sandurs and water exchange at diurnal and seasonal frequency should impact fluxes of solutes to the ocean, although understanding the magnitude of this effect will require long-term evaluation throughout the melt season.
2018025660 Guo Donglin (Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China); Li Duo and Hua Wei. Quantifying air temperature evolution in the permafrost region from 1901 to 2014: International Journal of Climatology, 38(1), p. 66-76, illus. incl. 1 table, geol. sketch map, 76 ref., January 2018.
Permafrost is sensitive to climate change. In recent decades, a growing body of research has focused mainly on the study of permafrost thaw, but leaving the climate change in the permafrost region that has not been adequately assessed, which is of first importance for the research on permafrost thaw. Using gridded observations from the Climatic Research Unit (CRU), in conjunction with the European Centre for Medium-Range Weather Forecasts Reanalysis Interim (ERA-Interim) and Japanese 55-year Reanalysis (JRA-55) data, this study investigates characteristics of air temperature evolution in the region of permafrost throughout the 20th century. Results show that yearly air temperatures in the permafrost region of the Northern Hemisphere experienced a statistically significant warming, with trends of 0.13 °C decade-1 for 1901-2014 and 0.40 °C decade-1 for 1979-2014. Winter air temperatures showed the greatest increase during 1901-2014, while autumn air temperatures increased the most during 1979-2014. In addition, increases in air temperature in high-latitude permafrost sub-region are greater than those in high-elevation permafrost sub-region, and air temperatures in the permafrost sub-region of Mongolia have the largest trend from 1901 to 2014, followed by those in Russia, Alaska, Canada, and China. Air temperatures in the permafrost region increased 1.7 times more than temperatures globally from 1901 to 2014, and underwent an increase at a rate of 0.32 °C decade-1 during the period 1998-2014, when the global warming hiatus occurred with a trend of 0.06 °C decade-1. This implies that permafrost thaw may have continued during the global warming hiatus period. The close agreement between CRU data and ERA-Interim and JRA-55 reanalysis data indicates good reliability of air temperature evolution characteristics. These results provide information relevant to climate change in the permafrost region, and are useful for researching and understanding historical permafrost change. Abstract Copyright (2017), Royal Meteorological Society.
2018025848 Beer, Christian (Stockholm University, Department of Environmental Science and Analytical Chemistry, Stockholm, Sweden); Porada, Philipp; Ekici, Altug and Brakebusch, Matthias. Effects of short-term variability of meteorological variables on soil temperature in permafrost regions: The Cryosphere (Online), 12(2), p. 741-757, illus., 65 ref., 2018.
Effects of the short-term temporal variability of meteorological variables on soil temperature in northern high-latitude regions have been investigated. For this, a process-oriented land surface model has been driven using an artificially manipulated climate dataset. Short-term climate variability mainly impacts snow depth, and the thermal diffusivity of lichens and bryophytes. These impacts of climate variability on insulating surface layers together substantially alter the heat exchange between atmosphere and soil. As a result, soil temperature is 0.1 to 0.8 °C higher when climate variability is reduced. Earth system models project warming of the Arctic region but also increasing variability of meteorological variables and more often extreme meteorological events. Therefore, our results show that projected future increases in permafrost temperature and active-layer thickness in response to climate change will be lower (i) when taking into account future changes in short-term variability of meteorological variables and (ii) when representing dynamic snow and lichen and bryophyte functions in land surface models.
2018025849 Beniston, Martin (University of Geneva, Institute for Environmental Sciences, Geneva, Switzerland); Farinotti, Daniel; Stoffel, Markus; Andreassen, Liss M.; Coppola, Erika; Eckert, Nicolas; Fantini, Adriano; Giacona, Florie; Hauck, Christian; Huss, Matthias; Huwald, Hendrik; Lehning, Michael; López-Moreno, Juan-Ignacio; Magnusson, Jan; Marty, Christoph; Morán-Tejéda, Enrique; Morin, Samuel; Naaim, Mohamed; Provenzale, Antonello; Rabatel, Antoine; Six, Delphine; Stötter, Johann; Strasser, Ulrich; Terzago, Silvia and Vincent, Christian. The European mountain cryosphere; a review of its current state, trends, and future challenges: The Cryosphere (Online), 12(2), p. 759-794, illus. incl. 2 tables, 402 ref., 2018.
The mountain cryosphere of mainland Europe is recognized to have important impacts on a range of environmental processes. In this paper, we provide an overview on the current knowledge on snow, glacier, and permafrost processes, as well as their past, current, and future evolution. We additionally provide an assessment of current cryosphere research in Europe and point to the different domains requiring further research. Emphasis is given to our understanding of climate-cryosphere interactions, cryosphere controls on physical and biological mountain systems, and related impacts. By the end of the century, Europe's mountain cryosphere will have changed to an extent that will impact the landscape, the hydrological regimes, the water resources, and the infrastructure. The impacts will not remain confined to the mountain area but also affect the downstream lowlands, entailing a wide range of socioeconomical consequences. European mountains will have a completely different visual appearance, in which low- and mid-range-altitude glaciers will have disappeared and even large valley glaciers will have experienced significant retreat and mass loss. Due to increased air temperatures and related shifts from solid to liquid precipitation, seasonal snow lines will be found at much higher altitudes, and the snow season will be much shorter than today. These changes in snow and ice melt will cause a shift in the timing of discharge maxima, as well as a transition of runoff regimes from glacial to nival and from nival to pluvial. This will entail significant impacts on the seasonality of high-altitude water availability, with consequences for water storage and management in reservoirs for drinking water, irrigation, and hydropower production. Whereas an upward shift of the tree line and expansion of vegetation can be expected into current periglacial areas, the disappearance of permafrost at lower altitudes and its warming at higher elevations will likely result in mass movements and process chains beyond historical experience. Future cryospheric research has the responsibility not only to foster awareness of these expected changes and to develop targeted strategies to precisely quantify their magnitude and rate of occurrence but also to help in the development of approaches to adapt to these changes and to mitigate their consequences. Major joint efforts are required in the domain of cryospheric monitoring, which will require coordination in terms of data availability and quality. In particular, we recognize the quantification of high-altitude precipitation as a key source of uncertainty in projections of future changes. Improvements in numerical modeling and a better understanding of process chains affecting high-altitude mass movements are the two further fields that - in our view - future cryospheric research should focus on.
2018027996 Bouttes, Nathaelle (Université Bordeaux, Environnements et Paléoenvironnements Océaniques, Pessac, France); Swingedouw, Didier; Roche, Didier M.; Sanchez-Goni, Maria F. and Crosta, Xavier. Response of the carbon cycle in an intermediate complexity model to the different climate configurations of the last nine interglacials: Climate of the Past, 14(2), p. 239-253, illus. incl. 4 tables, 39 ref., 2018.
Atmospheric CO2 levels during interglacials prior to the Mid-Brunhes Event (MBE, ~ 430 ka BP) were around 40 ppm lower than after the MBE. The reasons for this difference remain unclear. A recent hypothesis proposed that changes in oceanic circulation, in response to different external forcings before and after the MBE, might have increased the ocean carbon storage in pre-MBE interglacials, thus lowering atmospheric CO2. Nevertheless, no quantitative estimate of this hypothesis has been produced up to now. Here we use an intermediate complexity model including the carbon cycle to evaluate the response of the carbon reservoirs in the atmosphere, ocean and land in response to the changes of orbital forcings, ice sheet configurations and atmospheric CO2 concentrations over the last nine interglacials. We show that the ocean takes up more carbon during pre-MBE interglacials in agreement with data, but the impact on atmospheric CO2 is limited to a few parts per million. Terrestrial biosphere is simulated to be less developed in pre MBE interglacials, which reduces the storage of carbon on land and increases atmospheric CO2. Accounting for different simulated ice sheet extents modifies the vegetation cover and temperature, and thus the carbon reservoir distribution. Overall, atmospheric CO2 levels are lower during these pre-MBE simulated interglacials including all these effects, but the magnitude is still far too small. These results suggest a possible misrepresentation of some key processes in the model, such as the magnitude of ocean circulation changes, or the lack of crucial mechanisms or internal feedbacks, such as those related to permafrost, to fully account for the lower atmospheric CO2 concentrations during pre-MBE interglacials.
2018025846 Gao Bing (China University of Geosciences, School of Water Resources and Environment, Beijing, China); Yang Dawen; Qin Yue; Wang Yuhan; Li Hongyi; Zhang Yanlin and Zhang Tingjun. Change in frozen soils and its effect on regional hydrology, upper Heihe Basin, northeastern Qinghai-Tibetan Plateau: The Cryosphere (Online), 12(2), p. 657-673, illus. incl. 2 tables, sketch map, 75 ref., 2018.
Frozen ground has an important role in regional hydrological cycles and ecosystems, particularly on the Qinghai-Tibetan Plateau (QTP), which is characterized by high elevations and a dry climate. This study modified a distributed, physically based hydrological model and applied it to simulate long-term (1971-2013) changes in frozen ground its the effects on hydrology in the upper Heihe basin, northeastern QTP. The model was validated against data obtained from multiple ground-based observations. Based on model simulations, we analyzed spatio-temporal changes in frozen soils and their effects on hydrology. Our results show that the area with permafrost shrank by 8.8 % (approximately 500 km2), predominantly in areas with elevations between 3500 and 3900 m. The maximum depth of seasonally frozen ground decreased at a rate of approximately 0.032 m decade-1, and the active layer thickness over the permafrost increased by approximately 0.043 m decade-1. Runoff increased significantly during the cold season (November-March) due to an increase in liquid soil moisture caused by rising soil temperatures. Areas in which permafrost changed into seasonally frozen ground at high elevations showed especially large increases in runoff. Annual runoff increased due to increased precipitation, the base flow increased due to changes in frozen soils, and the actual evapotranspiration increased significantly due to increased precipitation and soil warming. The groundwater storage showed an increasing trend, indicating that a reduction in permafrost extent enhanced the groundwater recharge.
2018025840 Liu Lin (Chinese University of Hong Kong, Earth System Science Programme, Hong Kong, China) and Larson, Kristine M. Decadal changes of surface elevation over permafrost area estimated using reflected GPS signals: The Cryosphere (Online), 12(2), p. 477-489, illus. incl. 3 tables, 41 ref., 2018.
Conventional benchmark-based survey and Global Positioning System (GPS) have been used to measure surface elevation changes over permafrost areas, usually once or a few times a year. Here we use reflected GPS signals to measure temporal changes of ground surface elevation due to dynamics of the active layer and near-surface permafrost. Applying the GPS interferometric reflectometry technique to the multipath signal-to-noise ratio data collected by a continuously operating GPS receiver mounted deep in permafrost in Barrow, Alaska, we can retrieve the vertical distance between the antenna and reflecting surface. Using this unique kind of observables, we obtain daily changes of surface elevation during July and August from 2004 to 2015. Our results show distinct temporal variations at three timescales: regular thaw settlement within each summer, strong interannual variability that is characterized by a sub-decadal subsidence trend followed by a brief uplift trend, and a secular subsidence trend of 0.26 ± 0.02 cm year-1 during 2004 and 2015. This method provides a new way to fully utilize data from continuously operating GPS sites in cold regions for studying dynamics of the frozen ground consistently and sustainably over a long time.
2018025844 Ran Youhua (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Li Xin and Cheng Guodong. Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai-Tibet Plateau: The Cryosphere (Online), 12(2), p. 595-608, illus. incl. 5 tables, 91 ref., 2018.
Air temperature increases thermally degrade permafrost, which has widespread impacts on engineering design, resource development, and environmental protection in cold regions. This study evaluates the potential thermal degradation of permafrost over the Qinghai-Tibet Plateau (QTP) from the 1960s to the 2000s using estimated decadal mean annual air temperatures (MAATs) by integrating remote-sensing-based estimates of mean annual land surface temperatures (MASTs), leaf area index (LAI) and fractional snow cover values, and decadal mean MAAT date from 152 weather stations with a geographically weighted regression (GWR). The results reflect a continuous rise of approximately 0.04 °C a-1 in the decadal mean MAAT values over the past half century. A thermal-condition classification matrix is used to convert modelled MAATs to permafrost thermal type. Results show that the climate warming has led to a thermal degradation of permafrost in the past half century. The total area of thermally degraded permafrost is approximately 153.76 ´ 104 km2, which corresponds to 88 % of the permafrost area in the 1960s. The thermal condition of 75.2 % of the very cold permafrost, 89.6 % of the cold permafrost, 90.3 % of the cool permafrost, 92.3 % of the warm permafrost, and 32.8 % of the very warm permafrost has been degraded to lower levels of thermal condition. Approximately 49.4 % of the very warm permafrost and 96 % of the likely thawing permafrost has degraded to seasonally frozen ground. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88, 97, 155, 185, 161, and 250 m, respectively. The degradation mainly occurred from the 1960s to the 1970s and from the 1990s to the 2000s. This degradation may lead to increased risks to infrastructure, reductions in ecosystem resilience, increased flood risks, and positive climate feedback effects. It therefore affects the well-being of millions of people and sustainable development at the Third Pole.
2018025843 Zwieback, Simon (University of Guelph, Department of Geography, Guelph, Canada); Kokelj, Steven V.; Günther, Frank; Boike, Julia; Grosse, Guido and Hajnsek, Irena. Sub-seasonal thaw slump mass wasting is not consistently energy limited at the landscape scale: The Cryosphere (Online), 12(2), p. 549-564, illus., 48 ref., 2018.
Predicting future thaw slump activity requires a sound understanding of the atmospheric drivers and geomorphic controls on mass wasting across a range of timescales. On sub-seasonal timescales, sparse measurements indicate that mass wasting at active slumps is often limited by the energy available for melting ground ice, but other factors such as rainfall or the formation of an insulating veneer may also be relevant. To study the sub-seasonal drivers, we derive topographic changes from single-pass radar interferometric data acquired by the TanDEM-X satellites. The estimated elevation changes at 12 m resolution complement the commonly observed planimetric retreat rates by providing information on volume losses. Their high vertical precision (around 30 cm), frequent observations (11 days) and large coverage (5000 km2) allow us to track mass wasting as drivers such as the available energy change during the summer of 2015 in two study regions. We find that thaw slumps in the Tuktoyaktuk coastlands, Canada, are not energy limited in June, as they undergo limited mass wasting (height loss of around 0 cm day-1) despite the ample available energy, suggesting the widespread presence of early season insulating snow or debris veneer. Later in summer, height losses generally increase (around 3 cm day-1), but they do so in distinct ways. For many slumps, mass wasting tracks the available energy, a temporal pattern that is also observed at coastal yedoma cliffs on the Bykovsky Peninsula, Russia. However, the other two common temporal trajectories are asynchronous with the available energy, as they track strong precipitation events or show a sudden speed-up in late August respectively. The observed temporal patterns are poorly related to slump characteristics like the headwall height. The contrasting temporal behaviour of nearby thaw slumps highlights the importance of complex local and temporally varying controls on mass wasting.
2018025249 Marcucci, Emma C. (Space Telescope Science Institute, Baltimore, MD); Hamilton, Christopher W. and Herrick, Robert R. Remote sensing evidence of lava-ground ice interactions associated with the Lost Jim Lava Flow, Seward Peninsula, Alaska: Bulletin of Volcanology, 79(12), Article 89, illus. incl. 1 table, sketch map, 84 ref., December 2017.
Thermokarst terrains develop when ice-bearing permafrost melts and causes the overlying surface to subside or collapse. This process occurs widely throughout Arctic regions due to environmental and climatological factors, but can also be induced by localized melting of ground ice by active lava flows. The Lost Jim Lava Flow (LJLF) on the Seward Peninsula of Alaska provides evidence of former lava-ground ice interactions. Associated geomorphic features, on the scale of meters to tens of meters, were identified using satellite orthoimages and stereo-derived digital terrain models. The flow exhibits positive- and mixed-relief features, including tumuli (N = 26) and shatter rings (N = 4), as well as negative-relief features, such as lava tube skylights (N = 100) and irregularly shaped topographic depressions (N = 1188) that are interpreted to include lava-rise pits and lava-induced thermokarst terrain. Along the margins of the flow, there are also clusters of small peripheral pits that may be the products of meltwater or steam escape. On Mars, we observed morphologically similar pits near lava flow margins in northeastern Elysium Planitia, which suggests a common formation mechanism. Investigating the LJLF may therefore help to elucidate processes of lava-ground ice interaction on both Earth and Mars. Copyright 2017 Springer-Verlag GmbH Germany, part of Springer Nature
2018022074 Pan Xicai (Chinese Academy of Sciences, Institute of Soil Science, Fengqiu Agro-ecological Experimental Station, Nanjing, China); Yu Qihao; You Yanhui; Chun Kwokpan; Shi, Xiaogang and Li, Yanping. Contribution of supra-permafrost discharge to thermokarst lake water balances on the northeastern Qinghai-Tibet Plateau: Journal of Hydrology, 555, p. 621-630, illus. incl. 2 tables, sketch map, 57 ref., December 2017. Includes appendices.
The seasonal hydrological mechanisms of two thermokarst lakes on the northeastern Qinghai-Tibet Plateau (QTP) were characterized by three-year intensive field observations and a water balance model. In three ice-free seasons, the supra-permafrost discharge contributed a mean ratio of over 170% of the precipitation. In the ice-cover seasons, the supra-permafrost discharge contribution varied between -20% and 22% of the water storage change. Results show that a large portion of the lake water storage change is because of the supra-permafrost discharge resulting from precipitation. Furthermore, a precipitation-subsurface runoff function is preliminarily identified in which the supra-permafrost discharge nonlinearly increased with more precipitation. Our results show that the recent lake expansion is linked with increasing supra-permafrost discharge dominated by precipitation. This study also suggests that we need to pay attention to the nonlinear increase of precipitation-controlled supra-permafrost discharge on the large lake expansion at the catchment scale in the QTP region, instead of only looking at the inputs (e.g., precipitation and river discharge) as shown in the previous studies.
2018022087 Tian Zhengchao (China Agricultural University, Department of Soil & Water Sciences, Beijing, China); Ren Tusheng; Kojima, Yuki; Lu Yili; Horton, Robert and Heitman, Joshua L. An improved thermo-time domain reflectometry method for determination of ice contents in partially frozen soils: Journal of Hydrology, 555, p. 786-796, illus. incl. 4 tables, 64 ref., December 2017. Includes appendices.
Measuring ice contents (qi) in partially frozen soils is important for both engineering and environmental applications. Thermo-time domain reflectometry (thermo-TDR) probes can be used to determine qi based on the relationship between qi and soil heat capacity (C). This approach, however, is accurate in partially frozen soils only at temperatures below -5°C, and it performs poorly on clayey soils. In this study, we present and evaluate a soil thermal conductivity (l)-based approach to determine qi with thermo-TDR probes. Bulk soil l is described with a simplified de Vries model that relates l to qi. From this model, qi is estimated using inverse modeling of thermo-TDR measured l. Soil bulk density (rb) and thermo-TDR measured liquid water content (ql) are also needed for both C-based and l-based approaches. A theoretical analysis is performed to quantify the sensitivity of C-based and l-based qi estimates to errors in these input parameters. The analysis indicates that the l-based approach is less sensitive to errors in the inputs (C, l, ql, and rb) than is the C-based approach when the same or the same percentage errors occur. Further evaluations of the C-based and l-based approaches are made using experimentally determined qi at different temperatures on eight soils with various textures, total water contents, and rb. The results show that the l-based thermo-TDR approach significantly improves the accuracy of qi measurements at temperatures ≤&eq;-5°C. The root mean square errors of l-based qi estimates are only half those of C-based qi. At temperatures of -1 and -2°C, the l-based thermo-TDR approach also provides reasonable qi, while the C-based approach fails. We conclude that the l-based thermo-TDR method can reliably determine qi even at temperatures near the freezing point of water (0°C).
2018025453 Guo Donglin (Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China); Wang Huijun and Wang Aihui. Sensitivity of historical simulation of the permafrost to different atmospheric forcing data sets from 1979 to 2009: Journal of Geophysical Research: Atmospheres, 122(22), p. 12,269-12,284, illus. incl. 4 tables, 56 ref., November 27, 2017.
Numerical simulation is of great importance to the investigation of changes in frozen ground on large spatial and long temporal scales. Previous studies have focused on the impacts of improvements in the model for the simulation of frozen ground. Here the sensitivities of permafrost simulation to different atmospheric forcing data sets are examined using the Community Land Model, version 4.5 (CLM4.5), in combination with three sets of newly developed and reanalysis-based atmospheric forcing data sets (NOAA Climate Forecast System Reanalysis (CFSR), European Centre for Medium-Range Weather Forecasts Re-Analysis Interim (ERA-I), and NASA Modern Era Retrospective-Analysis for Research and Applications (MERRA)). All three simulations were run from 1979 to 2009 at a resolution of 0.5° ´ 0.5° and validated with what is considered to be the best available permafrost observations (soil temperature, active layer thickness, and permafrost extent). Results show that the use of reanalysis-based atmospheric forcing data set reproduces the variations in soil temperature and active layer thickness but produces evident biases in their climatologies. Overall, the simulations based on the CFSR and ERA-I data sets give more reasonable results than the simulation based on the MERRA data set, particularly for the present-day permafrost extent and the change in active layer thickness. The three simulations produce ranges for the present-day climatology (permafrost area: 11.31-13.57 ´ 106 km2; active layer thickness: 1.10-1.26 m) and for recent changes (permafrost area: -5.8% to -9.0%; active layer thickness: 9.9%-20.2%). The differences in air temperature increase, snow depth, and permafrost thermal conditions in these simulations contribute to the differences in simulated results. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2018025454 Guo Donglin (Chinese Academy of Sciences, Institute of Atmospheric Physics, Beijing, China) and Wang Huijun. Simulated historical (1901-2010) changes in the permafrost extent and active layer thickness in the Northern Hemisphere: Journal of Geophysical Research: Atmospheres, 122(22), p. 12,285-12,295, illus., 56 ref., November 27, 2017.
A growing body of simulation research has considered the dynamics of permafrost, which has an important role in the climate system of a warming world. Previous studies have concentrated on the future degradation of permafrost based on global climate models (GCMs) or data from GCMs. An accurate estimation of historical changes in permafrost is required to understand the relations between changes in permafrost and the Earth's climate and to validate the results from GCMs. Using the Community Land Model 4.5 driven by the Climate Research Unit - National Centers for Environmental Prediction (CRUNCEP) atmospheric data set and observations of changes in soil temperature and active layer thickness and present-day areal extent of permafrost, this study investigated the changes in permafrost in the Northern Hemisphere from 1901 to 2010. The results showed that the model can reproduce the interannual variations in the observed soil temperature and active layer thickness. The simulated area of present-day permafrost fits well with observations, with a bias of 2.02 ´ 106 km2. The area of permafrost decreased by 0.06 (0.62) ´ 106 km2 decade-1 from 1901 to 2009 (1979 to 2009). A clear decrease in the area of permafrost was found in response to increases in air temperatures during the period from about the 1930s to the 1940s, indicating that permafrost is sensitive to even a temporary increase in temperature. From a regional perspective, high-elevation permafrost decreases at a faster rate than high-latitude permafrost; permafrost in China shows the fastest rate of decrease, followed by Alaska, Russia, and Canada. Discrepancies in the rate of decrease in the extent of permafrost among different regions were mostly linked to the sensitivity of permafrost in the regions to increases in air temperatures rather than to the amplitude of the increase in air temperatures. An increase in the active layer thickness of 0.009 (0.071) m decade-1 was shown during the period of 1901-2009 (1979-2009). These results are useful in understanding the response of permafrost to a historical warming climate and for validating the results from GCMs. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2018025450 Qin Yanhui (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Tonghua; Zhao Lin; Wu Xiaodong; Li Ren; Xie Changwei; Pang Qiangqiang; Hu Guojie; Qiao Yongping; Zhao Guohui; Liu Guangyue; Zhu Xiaofan and Hao Junming. Numerical modeling of the active layer thickness and permafrost thermal state across Qinghai-Tibetan Plateau: Journal of Geophysical Research: Atmospheres, 122(21), p. 11,604-11,620, illus. incl. 8 tables, geol. sketch maps, November 16, 2017.
The dynamics of permafrost (including the permafrost thermal state and active layer thicknesses (ALT)) across the Qinghai-Tibetan Plateau (QTP) have not been well understood on a large scale. Here we simulate the ALT and permafrost thermal state using the Geophysical Institute Permafrost Lab version 2 (GIPL2) model across the QTP. Based on the single-point simulations, the model is upscaled to the entire QTP. The upscaled model is validated with five investigated regions (IRs), including Wenquan (WQIR), Gaize (GZIR), Aerjin (AEJIR), Xikunlun (XKLIR), and Qinghai-Tibetan Highway (G109IR). The results show that the modified GIPL2 model improves the accuracy of the permafrost thermal state simulations. Due to our simulated results on the QTP, the average ALT is of 2.30 m (2.21-2.40 m). The ALT decreases with an increase in the altitude and decreases from the southeast to the northwest. The ALT is thin in the central QTP, but it is thick in the high-elevation mountain areas and some areas surrounding glaciers and lakes. The largest ALT is found in the border areas between permafrost and seasonally frozen ground regions. The simulated results of the MAGT (the mean annual ground temperature) indicate that most of the permafrost is substable, which is sensitive to climate warming. The simulated results would be of great significance on assessing the impacts of permafrost dynamics on local hydrology, ecology, and engineering construction. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2018025449 Zhu Xiaofan (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Tonghua; Li Ren; Xie Changwei; Hu Guojie; Qin Yanhui; Wang Weihua; Hao Junming; Yang Shuhua; Ni Jie and Yang Cheng. Impacts of summer extreme precipitation events on the hydrothermal dynamics of the active layer in the Tanggula permafrost region on the Qinghai-Tibetan plateau: Journal of Geophysical Research: Atmospheres, 122(21), p. 11,549-11,567, illus. incl. 5 tables, geol. sketch map, 93 ref., November 16, 2017.
The characteristics of long-term variation for extreme precipitation events were analyzed at the Tanggula site in the continuous permafrost regions of the Qinghai-Tibetan Plateau (QTP). In addition, the impacts of extreme precipitation events in summer on soil thermal-moisture dynamics were also investigated. The results showed that local extreme precipitation indices fluctuated significantly and that the trend magnitudes of local very wet days (R95p), annual total wet-day precipitation (PRCPTOT), number of heavy precipitation days (R10mm), maximum length of dry spell (CDD), and simple daily intensity index (SDII) were larger than those of the western QTP, other regions of China, and even the global average. The freeze-thaw cycling in the local active layer occurred from October to the next September during 2006 to 2014. The influence of extreme precipitation event in summer on local soil hydrothermal conditions could reach soil depths up to 105 cm or so, and these were more pronounced than with light or moderate precipitation events. Soil temperature reacted more promptly to local extreme precipitation events than did soil moisture. The rate at which local soil temperature fell after an extreme precipitation event was greater than the rate of increasing temperature on nonprecipitation days. Moreover, the amount of precipitation received during extreme precipitation events had a greater effect on local soil moisture and temperature than duration time for these events. Consecutive extreme precipitation events with a longer duration time did not necessarily to have a greater effect than a single precipitation event with a shorter duration. Finally, the thawing process of active layer and local water migration modes could also affect the response of soil hydrothermal conditions to an extreme precipitation event to a large extent. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2018023265 Cao Wei (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Sheng Yu; Wu Jichun; Li Jing; Chou Yaling and Li Jinping. Simulation analysis of the impacts of underground mining on permafrost in an opencast coal mine in the northern Qinghai-Tibet Plateau: Environmental Earth Sciences, 76(20), Article 711, illus. incl. 1 table, 38 ref., October 2017.
Based on two-dimensional heat-conduction equations with a phase-change component, this study investigates the impact of underground mining on the permafrost environment in an opencast coal mining pit. The dynamics of the maximum thawed and freezing depths at different depths around a borehole wall are determined. The spatial distributions of these dynamics are also determined at different locations of the wall profile. The results show that (1) the maximum freezing depth tends to increase over 100 years; (2) the maximum thawed depth increases along a borehole wall over 100 years. In particular, the maximum thawed depth increases faster near the junctions of permafrost and seasonally frozen soil; (3) due to the small cross section of mining laneways, coal mining does not cause rapid increases in permafrost temperature around borehole walls. Once disturbance to permafrost around a borehole wall decreases, the once-insignificant effect of temperature will become more obvious. Underground mining does have some impacts on permafrost surrounding borehole walls, but it does not cause large areas of deformation due to thermal disturbance. Copyright 2017 Springer-Verlag GmbH Germany
2018019507 Delpupo, Caroline (Instituto Federal de Minas Gerais, Conselheiro Lafaiete, Brazil); Schaefer, Carlos Ernesto Goncalves Reynaud; Roque, Mariane Batalha; Faria, Andre Luiz Lopes; da Rosa, Katia Kellem; Thomazini, Andre and de Paula, Mayara Daher. Soil and landform interplay in the dry valley of Edson Hills, Ellsworth Mountains, continental Antarctica: Geomorphology, 295, p. 134-146, illus. incl. 5 tables, geol. sketch map, 40 ref., October 15, 2017.
The main relief units from the dry valley of Edson Hills, Ellsworth Mountains, Antarctica (79°49'12.4"/83°40'16.1"), were assessed, emphasizing the analysis of soil and landform interplay. Soil morphological, physical, and chemical properties; salinity; surface boulder weathering (frequency and feature); classification; and weathering stages were analyzed. Three distinct landforms summarize the geomorphology of the dry valley of Edson Hills, Ellsworth Mountains: (i) periglacial features like slightly creeping debris-mantled slopes, steep debris-mantled slopes, patterned grounds, and thermokarst; (ii) glacial features like hummocky moraines, lateral moraines (supraglacial), lakes, kettle hole (proglacial), cirques infill (subglacial), horn, and arete (erosional glacial); and (iii) nonglacial features like scree slopes and talus deposits. All these glacial and periglacial features are related to the West Antarctica ice sheet variations. Soils in the dry valley of Edson Hills are pedologically poorly developed. However, the degree of development in soils associated with patterned ground and moraine systems is remarkable. All soils present desert pavement owing to the action of severe aeolian erosion. In addition, soils accumulate salts depending on the local drainage conditions. The most expressive soil classes among the studied soils were Typic Haploturbel and Typic Anhyorthel, especially because of: (i) a general trend of ice-cemented permafrost occurrence in lower portions of the landscape, particularly in the patterned ground area and in the hummocky moraine; and (ii) the presence of dry permafrost in higher positions of the landscape, in relief units such as in debris-mantled slopes and talus deposits. Thus, a close relationship among soil characteristics and landforms were observed in the dry valley of Edson Hills.
2018027706 Malakhova, Valentina V. (Institute of Computational Mathematics and Mathematical Geophysics, Novosibirsk, Russian Federation) and Eliseev, Alexey V. The role of heat transfer time scale in the evolution of the subsea permafrost and associated methane hydrates stability zone during glacial cycles: Global and Planetary Change, 157, p. 18-25, illus. incl. 1 table, 57 ref., October 2017. Includes appendices.
Climate warming may lead to degradation of the subsea permafrost developed during Pleistocene glaciations and release methane from the hydrates, which are stored in this permafrost. It is important to quantify time scales at which this release is plausible. While, in principle, such time scale might be inferred from paleoarchives, this is hampered by considerable uncertainty associated with paleodata. In the present paper, to reduce such uncertainty, one-dimensional simulations with a model for thermal state of subsea sediments forced by the data obtained from the ice core reconstructions are performed. It is shown that heat propagates in the sediments with a time scale of ~ 10-20 kyr. This time scale is longer than the present interglacial and is determined by the time needed for heat penetration in the unfrozen part of thick sediments. We highlight also that timings of shelf exposure during oceanic regressions and flooding during transgressions are important for simulating thermal state of the sediments and methane hydrates stability zone (HSZ). These timings should be resolved with respect to the contemporary shelf depth (SD). During glacial cycles, the temperature at the top of the sediments is a major driver for moving the HSZ vertical boundaries irrespective of SD. In turn, pressure due to oceanic water is additionally important for SD >&eq; 50 m. Thus, oceanic transgressions and regressions do not instantly determine onsets of HSZ and/or its disappearance. Finally, impact of initial conditions in the subsea sediments is lost after ~ 100 kyr. Our results are moderately sensitive to intensity of geothermal heat flux.
2018019558 Popescu, Razvan (University of Bucharest, Research Institute, Bucharest, Romania); Vespremeanu-Stroe, Alfred; Onaca, Alexandru; Vasile, Mirela; Cruceru, Nicolae and Pop, Olimpiu. Low altitude permafrost research in an overcooled talus slope-rock glacier system in the Romanian Carpathians (Detunata Goala, Apuseni Mountains): Geomorphology, 295, p. 840-854, illus. incl. 2 tables, sketch maps, 41 ref., October 15, 2017.
Ground and air temperature monitoring, geophysical soundings and dendrological investigations were applied to a basaltic talus slope-rock glacier system from Detunata site in the Apuseni Mountains (Western Romanian Carpathians) to verify the presence of sporadic permafrost at 1020-1110 m asl, well below the regional limit of mountain permafrost. The near 0°C mean annual ground surface temperatures imposed by the large negative annual thermal anomalies of the ground (up to 7.4°C), together with the high resistivity values and the occurrence of trees with severe growth anomalies, support the presence of permafrost at this location. Temperature measurements and ground air circulation experiments proved that the so-called "chimney effect" is the main process favoring the ground overcooling and allowed for the construction of a model of ground air circulation in complex morphology deposits. The texture and porosity of the debris were quantified along with the local morphology in order to evaluate their role upon the chimney circulation. The debris porosity was found to be very high promoting intense ground overcooling during the cold season, including the periods of high snow cover due to the development of snow funnels. It efficiently reduces the heat transfer during summer thus contributing essentially to permafrost preservation. In compound morphologies, the depressed and low-lying features are the cold zones subjected to winter overcooling and summer chill, while the high-positioned and convex-up landforms become warm air evacuation features with positive thermal anomalies. Tree-ring measurements showed that the growth of cold-affected trees is higher during colder intervals (years to decades) probably as a consequence of the weakened katabatic air outflow during cooler summers. The dendrological analysis of multi-centennial spruces and their growth rates also provided palaeoclimatic inferences for the last 200 years.
2018021418 Hu Guojie (Chinese Academy of Sciences, Cryosphere Research Station on Qinghai-Xizang Plateau, Lanzhou, China); Zhao Lin; Wu Xiaodong; Li Ren; Wu Tonghua; Xie Changwei; Pang Qiangqiang and Zou Defu. Comparison of the thermal conductivity parameterizations for a freeze-thaw algorithm with a multi-layered soil in permafrost regions: Catena (Giessen), 156, p. 244-251, illus. incl. 4 tables, sketch map, 49 ref., September 2017.
Soil thermodynamic properties are critical for determining the soil freezing and thawing depths of active layers which is highly important for the hydrology and energy balances of permafrost regions. Here, three soil thermal conductivity parameterizations were evaluated against detailed field measurements at two field sites in the permafrost region of Qinghai-Xizang (Tibet) Plateau (QXP). The results revealed that the comprehensive parameterization based on different schemes for calculating soil thermal conductivity is relatively close to the measured values in unfrozen soil, and Johansen's parameterization is the best in the frozen soil. Then, we first combined three thermal conductivity parameterizations with a freeze-thaw algorithm to simulate freezing and thawing depths of multi-layered soil. The analysis showed that the average percentage difference between the observed and calculated soil thawing depth values for the Johansen's and comprehensive parameterization was 10.42% and 8.49% at Tanggula (TGL) and Xidatan (XDT), receptively. It indicated that the comprehensive parameterization with freeze-thaw algorithm simulated the soil thawing depth more similarly to the observed data for multi-layered soil. These findings can also be incorporated into other land surface, hydrological or ecosystem models to simulate the freeze-thaw cycles in permafrost regions.
2018021426 Szymanski, Wojciech (Jagiellonian University, Department of Pedology and Soil Geography, Cracow, Poland). Chemistry and spectroscopic properties of surface horizons of Arctic soils under different types of tundra vegetation; a case study from the Fuglebergsletta coastal plain (SW Spitsbergen): Catena (Giessen), 156, p. 325-337, illus. incl. 8 tables, sketch map, 88 ref., September 2017.
Detailed studies of soil organic matter (SOM) are currently very important, especially in the permafrost-affected soils of the High Arctic, as many of these soils contain quite a large amount of SOM, which may be very susceptible to decomposition due to climate change. The main objective of this study was to determine the chemistry and spectroscopic properties of surface horizons (O, A, AC) of High Arctic soils under different types of tundra vegetation in the eastern part of the Fuglebergsletta coastal plain (Hornsund area, SW Spitsbergen) in the context of SOM susceptibility to decomposition due to climate change. The obtained results indicate that soils covered with wet moss and ornithocoprophilous tundra vegetation exhibits significantly higher carbon and nitrogen content in comparison with soils covered with lichen-heath, polygonal, and geophytic initial tundra vegetation. Despite differences in the elemental composition of all the soil surface horizons, the mean C/N ratio for the studied horizons is low and similar (i.e. from 9 to 14). This indicates that C/N ratio is not a good indicator of degree of organic matter decomposition for the High Arctic soils occurring in areas affected by seabirds. A high E4/E6 ratio (i.e. ratio of UV-Vis absorbance measured at 472 nm and 664 nm and often called humification index) for NaOH-soluble humic substances indicates that the humic substances present in the studied surface horizons of soils covered with wet moss, ornithocoprophilous, and lichen-heath tundra vegetation are characterized by a low degree of humification. The Fourier transform infrared (FTIR) spectroscopy data indicate a prevalence of aromatic rings over aliphatic chains in the surface horizons of Cryosols under polygonal, geophytic initial, and lichen-heath tundra vegetation. Surface horizons of soils covered with wet moss and ornithocoprophilous tundra vegetation types exhibit a prevalence of aliphatic chains over aromatic rings. Such soils, which occupy about one third of the studied area, may act as carbon sources in the context of the emission of greenhouse gases into the atmosphere if the global air temperature will still rise. On the other hand, SOM from the surface horizons of soils covered with polygonal and geophytic initial tundra vegetation and occupying about 40% of the studied area, exhibits low potential susceptibility to decomposition.
2018019351 Evans, Sarah G. (University of Colorado Boulder, Department of Geological Sciences, Boulder, CO) and Ge, Shemin. Contrasting hydrogeologic responses to warming in permafrost and seasonally frozen ground hillslopes: Geophysical Research Letters, 44(4), p. 1803-1813, illus., 73 ref., February 28, 2017.
Seasonally frozen ground (SFG) and permafrost underlay approximately half of the land surface in the Northern Hemisphere. It is anticipated that climate warming will degrade both types of frozen ground, altering groundwater discharge to streams. While the effects of permafrost degradation on groundwater discharge have been analyzed, quantification of how groundwater discharge in degrading permafrost differs from that in SFG is lacking. This study simulates coupled groundwater and heat transport under freeze-thaw conditions for four representative hillslopes underlain by either continuous permafrost or SFG and compares groundwater discharge outputs under projected warming scenarios over decadal scales. Model results show that without warming there is more groundwater discharge in hillslopes with SFG than permafrost. After a century of warming, groundwater discharge increases for both kinds of frozen ground, but permafrost experiences a larger increase than SFG. These findings have implications for aquatic ecosystems and prioritizing water resource planning. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
2018024267 Clay, P. (Richard Hale School, Department of Earth Science, Hertford, United Kingdom). The origin of relic cryogenic mounds at East Walton and Thompson Common, Norfolk, England: Proceedings of the Geologists' Association, 126(4-5), p. 522-535, illus. incl. sect., 4 tables, geol. sketch map, 37 ref., October 2015. Available from: Geological Society London, Library, London, United Kingdom.
Contemporary pingo and lithalsa mounds are features which develop exclusively within cold climate environments in areas of continuous and discontinuous permafrost. The presence of pingo and lithalsa remnants as rampart enclosed ponds has been documented across temperate areas of the Northern Hemisphere and has been used to establish the extent of former permafrost. Two sites thought to be remnants of hydraulic pingo forms were investigated at East Walton and Thompson Common(s) in order to establish a precise origin. Through Ground Penetrating Radar and Electrical Resistivity Tomography the structure of ramparts and hollows has been investigated and interpreted. Linking this with physical and ground invasive techniques and a consideration of the hydrogeological setting it was apparent that the two sites had different origins. The topography, geology and hydrogeology of the East Walton area are a stereotypical setting for the development of hydraulic pingos. In contrast, the development of features within the Lowestoft Till and weathered Chalk Formations at Thompson Common implies that forms resulted from the heave of material through segregation ice lens growth. This has led to the creation of a model at East Walton which documents the development of remnant pingo ramparts and the strata which result. It is proposed that this model can be used in the study of similar landforms.
2018024253 Murton, Julian B. (University of Sussex, Department of Geography, Brighton, United Kingdom); Bowen, David Q.; Candy, Ian; Catt, John A.; Currant, Andrew; Evans, John G.; Frogley, Michael R.; Green, Christopher P.; Keen, David H.; Kerney, Michael P.; Parish, David; Penkman, Kirsty E. H.; Schreve, Danielle C.; Taylor, Sheila; Toms, Phillip S.; Worsley, Peter and York, Linda L. Middle and late Pleistocene environmental history of the Marsworth area, south-central England: Proceedings of the Geologists' Association, 126(1), p. 18-49, illus. incl. sect., 14 tables, geol. sketch map, 152 ref., February 2015. Available from: Geological Society London, Library, London, United Kingdom.
To elucidate the Middle and Late Pleistocene environmental history of south-central England, we report the stratigraphy, sedimentology, palaeoecology and geochronology of some deposits near the foot of the Chiltern Hills scarp at Marsworth, Buckinghamshire. The Marsworth site is important because its sedimentary sequences contain a rich record of warm stages and cold stages, and it lies close to the Anglian glacial limit. Critical to its history are the origin and age of a brown pebbly silty clay (diamicton) previously interpreted as weathered till. The deposits described infill a river channel incised into chalk bedrock. They comprise clayey, silty and gravelly sediments, many containing locally derived chalk and some with molluscan, ostracod and vertebrate remains. Most of the deposits are readily attributed to periglacial and fluvial processes, and some are dated by optically stimulated luminescence to Marine Isotope Stage (MIS) 6. Although our sedimentological data do not discriminate between a glacial or periglacial interpretation of the diamicton, amino-acid dating of three molluscan taxa from beneath it indicates that it is younger than MIS 9 and older than MIS 5e. This makes a glacial interpretation unlikely, and we interpret the diamicton as a periglacial slope deposit. The Pleistocene history reconstructed for Marsworth identifies four key elements: (1) Anglian glaciation during MIS 12 closely approached Marsworth, introducing far-travelled pebbles such as Rhaxella chert and possibly some fine sand minerals into the area. (2) Interglacial environments inferred from fluvial sediments during MIS 7 varied from fully interglacial conditions during sub-stages 7e and 7c, cool temperate conditions during sub-stage 7b or 7a, temperate conditions similar to those today in central England towards the end of the interglacial, and cool temperate conditions during sub-stage 7a. (3) Periglacial activity during MIS 6 involved thermal contraction cracking, permafrost development, fracturing of chalk bedrock, fluvial activity, slopewash, mass movement and deposition of loess and coversand. (4) Fully interglacial conditions during sub-stage 5e led to renewed fluvial activity, soil formation and acidic weathering.
2018021286 Yang Yugui (China University of Mining and Technology, State Key Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou, China). Experimental theoretical investigaitons on the deformation characteristic of frozen silt in underground engineering: The Electronic Journal of Geotechnical Engineering, 19(BUNDLE I), p. 1883-1894, illus., 16 ref., 2014. WWW.
A series of triaxial compressive tests of frozen silt has been conducted at -8°C. The nonlinear characteristic of the stress-strain curves for both axial and volumetric strains prior to failure was also analyzed. The constitutive equation for frozen silt is developed within the framework of the endochronic theory of plasticity. By defining intrinsic time and the softening and hardening function, then introducing them into endochronic equation, the constitutive equation of frozen silt is derived to reproduce the elastoplastic process according to experiment data and intrinsic time equation. The numerical schemes are examined for efficiency in the modeling the deformation process under triaxial compression. It is found that the endochronic theory, in which two groups of internal state variables are used to describe the mechanical features, could well predict the complicated deformation characteristic of frozen soil.
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2018025722 Nyland, Kelsey Elizabeth. Climate- and human- induced land cover change and its effects on the permafrost system in the Lower Yenisei River of the Russian Arctic: 88 p., illus. incl. 2 tables, geol. sketch map, 64 ref., Master's, 2015, George Washington University, Washington, DC.
Climate warming is occurring at an unprecedented rate in the Arctic, seriously impacting sensitive environments, and triggering land cover change. These changes are compounded by localized human influences. This work classifies land cover change for the Lower Yenisei River, identifies those changes that were climate- and anthropogenic-induced, and discusses the implications for the underlying permafrost system. This is accomplished using a modified version of the "Landsat dense time stacking" methodology for three time periods spanning 29 years that are representative of Russian socio-economic transitions during the mid- to late-1980s (1985-1987), the early 2000s (2000-2002), and the contemporary 2010s (2012-2014). The classified area includes three cities indicative of different post-Soviet socio-economic situations, including continued population and infrastructure decline (Igarka), a relatively stable community (Dudinka), and a community receiving local reinvestment (Norilsk). The land cover classification, in tandem with regional climate reanalysis data, enabled climate- and anthropogenic- induced changes to be identified, characterized, and quantified. Climatic changes within the natural environments have produced a steady greening effect throughout the study area, as well as an increase in large lake abundance, indicative of permafrost degradation. Pollution, in close proximity to heavy industrial activity, caused a secondary plant succession process. The results of this work provide both map products that can be applied to future research in this region, as well as insights into the impacts of the warming climate and human presence on sensitive Arctic environments.
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2018023504 Beylich, Achim A. (Geological Survey of Norway (NGU), Trondheim, Norway). The I.A.G./A.I.G. SEDIBUD (SEDIment BUDgets in cold environments) Program (2005-2017); key activities and outcomes [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2981, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Amplified climate change and ecological sensitivity of high-latitude and high-altitude cold climate environments has been highlighted as a key global environmental issue. Projected climate change in largely undisturbed cold regions is expected to alter melt-season duration and intensity, along with the number of extreme rainfall events, total annual precipitation and the balance between snowfall and rainfall. Similarly, changes to the thermal balance are expected to reduce the extent of permafrost and seasonal ground frost and increase active-layer depths. These combined effects will undoubtedly change Earth surface environments in cold regions and will alter the fluxes of sediments, solutes and nutrients. However, the absence of quantitative data and coordinated analysis to understand the sensitivity of the Earth surface environment are acute in cold regions. Contemporary cold climate environments generally provide the opportunity to identify solute and sedimentary systems where anthropogenic impacts are still less important than the effects of climate change. Accordingly, it is still possible to develop a library of baseline fluvial yields and sedimentary budgets before the natural environment is completely transformed. The SEDIBUD (Sediment Budgets in Cold Environments) Program, building on the European Science Foundation (ESF) Network SEDIFLUX (Sedimentary Source-to-Sink Fluxes in Cold Environments, since 2004) was formed in 2005 as a new Program (Working Group) of the International Association of Geomorphologists (I.A.G./A.I.G.) to address this still existing key knowledge gap. SEDIBUD (2005-2017) has currently about 400 members worldwide and the Steering Committee of this international program is composed of eleven scientists from ten different countries. The central research question of this global program is to: Assess and model the contemporary sedimentary fluxes in cold climates, with emphasis on both particulate and dissolved components. Research carried out at 56 defined SEDIBUD key test sites (selected catchment systems) varies by scientific program, logistics and available resources, but typically represent interdisciplinary collaborations of geomorphologists, hydrologists, ecologists, permafrost scientists and glaciologists with different levels of detail. SEDIBUD has developed a key set of primary research data requirements intended to incorporate results from these varied projects and allow quantitative analysis across the program. Defined SEDIBUD key test sites provide field data on annual climatic conditions, total discharge and particulate and dissolved fluxes and yields as well as information on other relevant denudational Earth surface processes. A number of selected key test sites are providing high-resolution data on climatic conditions, runoff and solute and sedimentary fluxes and yields, which - in addition to the annual data - contribute to the SEDIBUD metadata database. To support these coordinated efforts, the SEDIFLUX manual and a set of framework papers and book chapters have been produced to establish the integrative approach and common methods and data standards. Comparable field-datasets from different SEDIBUD key test sites are analyzed and integrated to address key research questions of the SEDIBUD program as defined in the SEDIBUD working group objective. A key SEDIBUD synthesis book was published in 2016 by the group and a synthesis key paper is currently in preparation. Detailed information on all SEDIBUD activities, outcomes and published products is found at URL: http://www.geomorph.org/sedibud-working-group/. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021888 Canario, Joao (Universidade de Lisboa, Instituto Superior Tecnico, Lisboa, Portugal); Santos, Margarida C.; Vieira, Goncalo and Vincent, Warwick F. Tracking permafrost soil degradation through sulphur biogeochemical tracers [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4139, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Canada Rising temperatures are contributing to the rapid degradation of Arctic permafrost soils. Several studies have been using some biogeochemical tracers as indicators of the organic matter degradation although fewer attention has been given to sulphur. In fact, the chemistry of this element is of environmental importance because it plays a key role in the degradation of natural organic matter and influences the partitioning, speciation and fate of other trace elements. To better understand the role of sulphur in biogeochemical processes in permafrost soils several campaigns were undertaken in the Canadian subarctic region of Kuujjuarapik-Whapmagoostui and Umiujaq (QC) as a part of the Canadian ADAPT and the Portuguese PERMACHEM projects. In four sites along those regions soil samples were collected and pore water were extracted. Dissolved sulphur compounds (sulphide and sulphate) were determined in water samples while in soils particulate sulphides, pyrite and elemental sulphur were quantified by voltammetry. Organic sulphur compounds were identified using 33SssNMR and X-ray diffraction both in powder and single crystal analysis were used to identify crystalline sulphides. Finally, subsamples of soils and water samples were analysed for total particulate and dissolved organic carbon. The results showed that sulphur composition depends largely on the origin of permafrost soils. In soils originated from organic-rich palsas, the proportion of organic sulphur (% of the total) is higher than 50%, while in mineral lithalsa soils the opposite was found. In both cases the origin of sulphur was mainly from plant organic matter degradation. The combined structural and chemical analysis allowed the identified different stages of soil degradation by determined the ratio between inorganic and organic sulphur species and by following the different NMR and XRD spectra. These preliminary results pointed to the importance of the sulphur biogeochemistry in permafrost soils and provide a good toll in permafrost degradation biogeochemical studies. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018020093 Ebrahimi, Ali (ETH Zurich, Biogeochemistry and Pollutant Dynamics, Zurich, Switzerland) and Or, Dani. Mechanistic modeling of thermo-hydrological processes and microbial interactions at pore to profile scales resolve methane emission dynamics from permafrost soil [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-3911, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The sensitivity of the Earth's polar regions to raising global temperatures is reflected in rapidly changing hydrological processes with pronounced seasonal thawing of permafrost soil and increased biological activity. Of particular concern is the potential release of large amounts of soil carbon and the stimulation of other soil-borne GHG emissions such as methane. Soil methanotrophic and methanogenic microbial communities rapidly adjust their activity and spatial organization in response to permafrost thawing and a host of other environmental factors. Soil structural elements such as aggregates and layering and hydration status affect oxygen and nutrient diffusion processes thereby contributing to methanogenic activity within temporal anoxic niches (hotspots or hot-layers). We developed a mechanistic individual based model to quantify microbial activity dynamics within soil pore networks considering, hydration, temperature, transport processes and enzymatic activity associated with methane production in soil. The model was the upscaled from single aggregates (or hotspots) to quantifying emissions from soil profiles in which freezing/thawing processes provide macroscopic boundary conditions for microbial activity at different soil depths. The model distinguishes microbial activity in aerate bulk soil from aggregates (or submerged parts of the profile) for resolving methane production and oxidation rates. Methane transport pathways through soil by diffusion and ebullition of bubbles vary with hydration dynamics and affect emission patterns. The model links seasonal thermal and hydrologic dynamics with evolution of microbial community composition and function affecting net methane emissions in good agreement with experimental data. The mechanistic model enables systematic evaluation of key controlling factors in thawing permafrost and microbial response (e.g., nutrient availability, enzyme activity, PH) on long term methane emissions and carbon decomposition rates in the rapidly changing polar regions. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018023666 Fernández, Jesús Ruiz (University of Oviedo, Centro de Cooperación y Desarrollo Territorial (CeCodet), Oviedo, Spain); Oliva, Marc; Menéndez, Susana del Carmen Fernández; Hernández, Cristina García; Duarte, Rosa Ana Menéndez; Ondicol, Ramón Pellitero; Alberti, Augusto Pérez and Schimmelpfennig, Irene. Glacial evolution in King George and Livingston Islands (Antarctica) since the last glacial maximum based on cosmogenic nuclide dating and glacier surface reconstruction; CRONOANTAR project [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4818, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
CRONOANTAR brings together researchers from Spain, Portugal, France and United Kingdom with the objective of spatially and temporally reconstruct the deglaciation process at the two largest islands in the South Shetlands Archipelago (Maritime Antarctica), since the Global Last Glacial Maximum. Glacier retreat in polar areas has major implications at a local, regional and even planetary scale. Global average sea level rise is the most obvious and socio-economically relevant, but there are others such as the arrival of new fauna to deglaciated areas, plant colonisation or permafrost formation and degradation. This project will study the ice-free areas in Byers and Hurd peninsulas (Livingston Island) and Fildes and Potter peninsulas (King George Island). Ice-cap glacier retreat chronology will be revealed by the use of cosmogenic isotopes (mainly 36Cl) on glacially originated sedimentary and erosive records. Cosmogenic dating will be complemented by other dating methods (C14 and OSL), which will permit the validation of these methods in regions with cold-based glaciers. Given the geomorphological evidences and the obtained ages, a deglaciation calendar will be proposed and we will use a GIS methodology to reconstruct the glacier extent and the ice thickness. The results emerging from this project will allow to assess whether the high glacier retreat rates observed during the last decades were registered in the past, or if they are conversely the consequence (and evidence) of the Global Change in Antarctica. Acknowledgements This work has been funded by the Spanish Ministry of Economy, Industry and Competitiveness (Reference: CTM2016-77878-P). [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018019942 Hrbacek, Filip (Masaryk University, Brno, Czech Republic) and Uxa, Tomas. Modelling of active layer thickness evolution on James Ross Island in 2006-2015 [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2637, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Antarctic Peninsula region has been considered as one of the most rapidly warming areas on the Earth. However, the recent studies (Turner et al., 2016; Oliva et al., 2017) showed that significant air temperature cooling began around 2000 and has continued until present days. The climate cooling led to reduction of active layer thickness in several parts of Antarctic Peninsula region during decade 2006-2015, but the information about spatiotemporal variability of active layer thickness across the region remains largely incoherent due to lack of active layer temperature data from deeper profiles. Valuable insights into active layer thickness evolution in Antarctic Peninsula region can be, however, provided by thermal modelling techniques. These have been widely used to study the active layer dynamics in different regions of Arctic since 1990s. By contrast, they have been employed much less in Antarctica. In this study, we present our first results from two equilibrium models, the Stefan and Kudryavtsev equations, that were applied to calculate the annual active layer thickness based on ground temperature data from depth of 5 cm on one site on James Ross Island, Eastern Antarctic Peninsula, in period 2006/07 to 2014/15. Study site (Abernethy Flats) is located in the central part of the major ice-free area of James Ross Island called Ulu Peninsula. Monitoring of air temperature 2 m above ground surface and ground temperature in 50 cm profile began on January 2006. The profile was extended under the permafrost table down to 75 cm in February 2012, which allowed precise determination of active layer thickness, defined as a depth of 0°C isotherm, in period 2012 to 2015. The active layer thickness in the entire observation period was reconstructed using the Stefan and Kudryavtsev models, which were driven by ground temperature data from depth of 5 cm and physical parameters of the ground obtained by laboratory analyses (moisture content and bulk density) and calculations from ground heat flux measurement (thermal conductivity and thermal capacity). Model results were validated using the reference active layer thicknesses from the summer seasons of 2012/13 to 2014/15 with very good accuracy of 0 to 4 cm and -4 to 1 cm for the Stefan and the Kudryavtsev models, respectively. Average active layer thickness on Abernethy Flats varied between 62 cm (Stefan model) and 60 cm (Kudryavtsev model) in period 2006/07-2014/15. Both models showed average active layer thinning of -1.3 cm.year-1 (Stefan model) and -2.3 cm.year-1 (Kudryavtsev model). Maximum active layer thickness was predicted in summer season 2008/09, reaching 75 cm (Stefan model) and 83 cm (Kudryavtsev model), while the minimum active layer thickness was observed in summer season 2009/10 when both models predicted 36 cm. Our results show that both models are well suited for conditions of Antarctica because their accuracy is in the order of the first centimetres. The nine-year series confirmed thinning of active layer in this part of Antarctic Peninsula region, which was mainly related to variability of summer air temperature. References: Turner, J., Lu, H., White, I., King, J. C., Phillips, T., Scott Hosking, J. Bracegirdle, T. J., Marshall, G. J., Mulvaney, R., Deb, P., 2016. Absence of 21st century warming on Antarctic Peninsula consistent with natural variability. Nature 535, doi: 10.1038/nature18645. Oliva, M., Navarro, F., Hrbacek, F., Hernandez, A., Nyvlt, D., Perreira, P., Ruiz-Fernandez, J., Trigo, R., in press. Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere. Science of Total Environment. dx.doi.org/10.1016/j.scitotenv.2016.12.030 [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021882 Johansson, Emma (Swedish Nuclear Fuel and Waste Management Company, Stockholm, Sweden) and Lindborg, Tobias. The GRASP project; a multidisciplinary study of hydrology and biogeochemistry in a periglacial catchment area [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4130, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The Arctic region is sensitive to global warming, and permafrost thaw and release of old carbon are examples of processes that may have a positive feedback effect to the global climate system. Quantification and assumptions on future change are often based on model predictions. Such models require cross-disciplinary data of high quality that often is lacking. Biogeochemical processes in the landscape are highly influenced by the hydrology, which in turn is intimately related to permafrost processes. Thus, a multidisciplinary approach is needed when collecting data and setting up field experiments aiming at increase the understanding of these processes. Here we summarize and present data collected in the GRASP, Greenland Analogue Surface Project. GRASP is a catchment-scale field study of the periglacial area in the Kangerlussuaq region, West Greenland, focusing on hydrological and biogeochemical processes in the landscape. The site investigations were initiated in 2010 and have since then resulted in three separate data sets published in ESSD (Earth system and Science Data) each one focusing on i) meteorological data and hydrology, ii) biogeochemistry and iii) geometries of sediments and the active layer. The three data-sets, which are freely available via the PANGAEA data base, enable conceptual and coupled numerical modeling of hydrological and biogeochemical processes. An important strength with the GRASP data is that all data is collected within the same, relatively small, catchment area. This implies that measurements are more easily linked to the right source area or process. Despite the small catchment area it includes the major units of the periglacial hydrological system; a lake, a talik, a supra- and subpermafrost aquifer and, consequently, biogeochemical processes in each of these units may be studied. The new data from GRASP is both used with the aim to increase the knowledge of present day periglacial hydrology and biogeochemistry but also in order to predict consequences within these subjects of future climate change. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018019972 Kholmyanskii, Mikhail (All-Russian Research Institute for Geology and Mineral Resources of the World Ocean, St. Petersburg, Russian Federation); Vladimirov, Maksim; Snopova, Ekaterina and Kartashev, Aleksandr. Cryolithozone of western Arctic shelf of Russia [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2693, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
We propose a new original version of the structure of the cryolithozone of west Arctic seas of Russia. In contrast to variants of construction of sections and maps based on thermodynamic modeling, the authors have used electrometric, seismic, and thermal data including their own profile measurements by near-field transient electromagnetic technique and seismic profile observations by reflection method. As a result, we defined the spatial characteristics of cryolithozone and managed to differentiate it to several layers, different both in structure and formation time. We confirmed once again that the spatial boundary of cryolithozone, type and thickness of permafrost, chilled rocks and thawed ground are primarily determined by tectonic and oceanographic regimes of the Arctic Ocean and adjacent land in different geological epochs. Permafrost formed on the land in times of cold weather, turn to submarine during flooding and overlap, in the case of the sea transgression, by marine sediments accumulating in the period of warming. We have been able to establish a clear link between the permafrost thickness and the geomorphological structure of the area. This can be explained by the distribution of thermodynamic flows that change the temperature state of previously formed permafrost rocks. Formation in the outer parts of the shelf which took place at ancient conversion stage can be characterized by the structure: permafrost table - consists of rocks, where the sea water with a temperature below 0°C has replaced the melted ice; middle horizon - composed of undisturbed rocks, and the rocks chilled through the lower sieving underlay; As a result of the interpretation and analysis of all the available data, the authors created a map of types of cryolithozone of the Western Arctic shelf of Russia. The following distribution areas are marked on the map: single-layer cryolithozone (composed of sediments upper Pleistocene and Holocene); monosyllabic relict permafrost; two-layer relict permafrost; three-layered cryolithozone (composed of Holocene rocks and two-layer relict mainly from permafrost rocks); three-layer cryolithozone (composed of Holocene rocks and two-layer relict mainly from chilled rocks); post-cryogenic thawed sediments. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018023579 Kuznetsova, Elena (Norwegian University of Science and Technology, Civil and Environmental Engineering, Trondheim, Norway). Multi-disciplinary approach in volcanic areas; case study of Kamchatka, far east of Russia [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-3598, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Volcanic ash is associated with a considerable proportion of the Earth's land surface. At the same time, it is estimated that 15% of the land surface is affected by permafrost and glacial ice. As a consequences volcanic ash may play an important role in the aggradation and degradation of cold regions (Kellerer-Pirklbauer et al., 2007; Froese et al., 2008). An understanding of the influence of volcanic ash on these frozen areas allows for more accurate prediction of their stability in the future and provides a better knowledge of the factors affecting past climates, soils and soil stability. Vital to making accurate predictions is an understanding of the thermal properties of volcanic ash (Juen et al., 2013). For example, even for the same region of Kamchatka in eastern Russia volcanic ash may have not only different ages, different chemical composition of the glass, but also different weathering stages, mineralogical composition, and water saturation, furthermore, these ashes may be permanently frozen or unfrozen, all of which may affect their thermal properties (Kuznetsova & Motenko, 2014). These differences might be the reason why the critical thickness of tephra, at which the effect on ice and snow is rather insulating than ablative, for the volcanic material from different volcanoes may vary so much. The determined values of critical thickness deviate from 24 mm reported by Driedger (1980) for the glaciers at Mt. St. Helens, USA, and by (Manville et al., 2000) for tephra erupted in 1996 by Mt. Ruapehu, New Zealand, to <5.5 mm for tephra from the 1947 eruption of Hekla volcano and from Villarica volcano, Chile, reported by Kirkbride and Dugmore (2003) and by Brock et al. (2007). So far the reasons of disparity are not known. Ayris and Delmelle (2012) assumed that the particle size and porosity might be the reason. Taking into considerations that during ablation period tephra covering the glaciers is wet, thermal conductivity of this material should not be overlooked (Kuznetsova et al., 2012). Of particular importance in understanding the thermal behavior of frozen soils is a knowledge of their unfrozen water content. In the glacier interlayers the unfrozen water between ice and particles can work as lubricants to modify the stress transfer at the contacts between ice-particle and particle-particle through indirect influence on relaxing the interaction between particles and ice (Moore, 2014). The paper discusses the application of multidisciplinary research on volcanic material covering permafrost and glaciers in volcanic areas. In cold environments, volcanic ash is widely used in different science disciplines in process-based studies examining paleoclimate reconstruction; the influence of permafrost aggradation and degradation; influence of tephra on snow and ice ablation; glacier fluctuations, volcanic glass weathering and new minerals formation (e.g. allophane, palagonite). The special properties of volcanic ash are critically reviewed particularly in relation to recent research in Kamchatka in the Far East of Russia. Of particular importance are the thermal properties and the unfrozen water contents of ash layers and the rate at which the weathering of volcanic glass takes place. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018023574 Kuznetsova, Elena (Norwegian University of Science and Technology, Civil and Transport engineering, Trondheim, Norway). Properties of volcanic soils in cold climate conditions [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-3591, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Layers of volcanic ash and the Andosol soils derived from them may play an important role in preserving snow and ice as well as developing permafrost conditions in the immediate vicinity of volcanoes of high elevation or those situated at high latitudes, and land areas, often distant from volcanic activity that are either prone to permafrost or covered by snow and ice, but are affected by the deposition of subaerial ash. The special properties of volcanic ash that are responsible are critically reviewed particularly in relation to recent research in Kamchatka in the Far East of Russia. Of particular importance are the thermal properties and the unfrozen water contents of ash layers and the rate at which the weathering of volcanic glass takes place. Volcanic glass is the most easily weathered component of volcanic ejecta (Shoji et al., 1993; Kimble et al., 2000). There are many specific environmental conditions, including paleoclimate and present-day climate, the composition of volcanic tephra and glaciation history, which cause the differences in weathering and development of volcanic ash soils (Zehetner et al., 2003). The preservation of in situ, unweathered, and unaltered surficial ash-fall deposits in the cold regions has important implications for paleoclimate and glacial history. Ash-fall deposits, which trap and preserve the soils, sediments, and landforms on which they fall, can be used to resolve local climate conditions (temperature and moisture) at the ash site during ash-fall deposition. The preservation of detailed sedimentary features (e.g. bedding in the ash, sharpness of stratigraphic contacts) can tell us about their post-depositional history, whether they have been redeposited by wind or water, or overridden by glaciers (Marchant et al., 1996). Weathering of volcanic glass results in the development of amorphous clay minerals (e.g. allophane, opal, palagonite) but this takes place much slower in cold than under warmer climate conditions. Only few studies on weathering of volcanic ash and developing volcanic soils under cold climatic conditions were carried out, especially in areas with permafrost (Bäumler, 2003). Most of research on volcanic permafrost soils was done in Yukon (Canada), Kamchatka (Russia), and Antarctica, or on seasonal frost in mountain area in Iceland, Japan, New Zealand, and Ecuador. Soils of Iceland and Antarctica are used as terrestrial analogs to Martian soils (Gooding & Keil, 1978; Allen et al., 1981). The review of existing data demonstrates that there is a strong correlation between the thermal conductivity, the water-ice content, and the mineralogy of the weathered part of the volcanic ash, enhanced amount of amorphous clay minerals (allophane, palagonite) increase the proportion of unfrozen water and decrease thermal conductivity (Kuznetsova et al., 2012, 2013; Kuznetsova & Motenko, 2014), and amorphous silica does not alter to halloysite or other clay minerals even in ashes of Early Pleistocene age (Kamchatka) or Miocene and Pliocene deposits (Antarctica) due to cold temperatures. The significance of these findings is discussed in relation to the reconstruction of past climates and the influence of volcanic ash on permafrost aggradation and degradation, snow and ice ablation, and the development of glaciers. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021864 Leibman, Marina (Russian Academy of Sciences, Siberian Branch, Earth Cryosphere Institute, Tyumen, Russian Federation); Kizyakov, Alexandr; Khomutov, Artem; Dvornikov, Yury; Babkina, Elena; Arefiev, Stanislav and Khairullin, Rustam. Are pre-crater mounds gas-inflated? [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-4085, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Gas-emission craters (GEC) on Yamal peninsula, which occupied minds of researches for the last couple of years since first discovered in 2014, appeared to form on the place of specifically shaped mounds. There was a number of hypotheses involving pingo as an origin of these mounds. This arouse an interest in mapping pingo thus marking the areas of GEC formation risk. Our field research allows us to suggest that remote-sensing-based mapping of pingo may result in mix up of mounds of various origin. Thus, we started with classification of the mounds based on remote-sensing, field observations and survey from helicopter. Then we compared indicators of mounds of various classes to the properties of pre-crater mounds to conclude on their origin. Summarizing field experience, there are three main mound types on Yamal. (1) Outliers (remnant hills), separated from the main geomorphic landform by erosion. Often these mounds comprise polygonal blocks, kind of "bay-dzherakh". Their indicators are asymmetry (short gentle slope towards the main landform, and steep slope often descending into a small pond of thermokarst-nivation origin), often quadrangle or conic shape, and large size. (2) Pingo, appear within the khasyrei (drain lake basin); often are characterized by open cracks resulting from expansion of polygonal network formed when re-freezing of lake talik prior to pingo formation; old pingo may bear traces of collapse on the top, with depression which differs from the GEC by absence of parapet. (3) Frost-heave mounds (excluding pingo) may form on deep active layer, reducing due to moss-peat formation and forming ice lenses from an active layer water, usually they appear in the drainage hollows, valley bottoms, drain-lake basins periphery. These features are smaller than the first two types of mounds. Their tops as a rule are well vegetated. We were unable to find a single or a set of indicators unequivocally defining any specific mound type, thus indicators of pre-crater mounds are still debatable. Our hypothesis initially does not involve pingo origin of pre-crater mounds for several reasons, among which were the initial depth (70 m) and width (18 m) of the crater void, frozen walls and bottom, no traces of sub-lake talik, an important control for pingo formation, and more. Pre-crater mounds are closer to frost-heave mounds in size (4-7 m high and 30-60 m in diameter). Yet frost-heave mounds like palsa or lithalsa have segregated ice lenses closer to the surface, total thickness of these lenses is equal to the height of the mound. Pre-crater mounds have at least 20 m of tabular ground ice in the section that has no manifestation in the mound height or diameter. All above-mentioned leads to the conclusion that pre-crater mounds form because of gas inflation rather than regular frost heave process involving moisture migration towards the freezing front. This research is supported by Russian Science Foundation Grant 16-17-10203. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021967 Leopold, Matthias (University of Western Australia, School of Agriculture and Environment, Crawley, West. Aust., Australia); Schorghofer, Norbert and Yoshikawa, Kenji. Permafrost on tropical Maunakea volcano, Hawaii [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5866, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
Maunakea volcano on Hawaii Island is known for one of the most unusual occurrences of sporadic permafrost. It was first documented in two cinder cone craters in the 1970's near the summit of the mountain where mean annual air temperatures are currently around +4 deg. Our study investigates the current state of this permafrost, by acquiring multi-year ground temperature data and by applying electrical resistivity tomography and ground penetrating radar techniques along several survey lines. Both of the previously known ice bodies still exist, but one of them has dramatically shrunken in volume. Based on current warming trends it might disappear soon. In addition insolation modelling, temperature probing, and geomorphological indicators were used to prospect for additional permafrost bodies on the wider summit region, however, none was found. It seems that permafrost preferentially appears in the interiors of cinder cones, even though there are exterior slopes that receive less sunlight annually. We hypothesis that snow cover with its high albedo, and a layer of coarse boulders where cold air settles in the pore space during calm nights, play a significant role in cooling the subsurface. Due to the relatively simple setting, the study site is an ideal model system and may also serve as an analogue to Mars. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021970 Leopold, Matthias (University of Western Australia, Crawlwy, West. Aust., Australia) and Schorghofer, Norbert. Lake Waiau and Puupohaku; two unusual lakes on Maunakea volcano, Hawaii [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5874, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
High mountain lakes are often a valuable buffer for water availability throughout the year. This is especially the case in alpine deserts like the high alpine areas of the Hawaiian Volcanoes above 3000 m altitude, since the porous and coarse cinder material and basalt boulders do not favor water storage. Puupohaku (~4,000 m asl), a cinder cone near the summit of Maunakea volcano, Hawaii, has a sporadic pond of water and also nearby Lake Waiau is perched within a cinder cone known as Puuwaiau (~3600 m asl) which makes it the highest lake on the Hawaiian Islands. With only 210 mm annual precipitation mostly caused by single storm events, and a potential evaporation of up to 5 mm/d, permanent water sources are extremely rare in this environment. Several hypotheses were discussed as a possible cause for perching the water in this environment such as an impermeable permafrost base, a massive block of lava or clay layers. We applied geomorphic mappings and electric resistivity tomography to portray the shallow subsurface in the vicinity of the two water bodies. We also used current and unpublished older temperature loggings to evaluate the thermal regime around the lakes. Based on our results, specific electric resistivity values are too low and ground temperatures are too high to be interpreted either as ice rich permafrost or basaltic massive rock. Much more, fine grained material such as ash and its clay-rich weathering products likely cause the perched water table at both study sites. At Lake Waiau we discovered a layer of high electric conductivity that may constitute a significant water reservoir outside of the lake and further be responsible for perching the water towards the lake. Understanding the nature of the two permanent water bodies will help to manage the sensitive alpine environment which includes several endemic species. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018023456 Opel, Thomas (University of Sussex, Department of Geography, Permafrost Laboratory, Brighton, United Kingdom); Wetterich, Sebastian; Meyer, Hanno; Dereviagin, Alexander Yu.; Fuchs, Margret C. and Schirrmeister, Lutz. Ground-ice stable isotopes and cryostratigraphy reflect late Quaternary palaeoclimate in the northeast Siberian Arctic (Oyogos Yar Coast, Dmitry Laptev Strait) [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2862, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
To reconstruct palaeoclimate and palaeoenvironmental conditions in the Northeast Siberian Arctic, we studied late Quaternary permafrost deposits at the Oyogos Yar coast (Dmitry Laptev Strait). New infrared stimulated luminescence ages for distinctive floodplain deposits of the Kuchchugui Suite (112.5± 9.6 kyr) and thermokarst lake deposits of the Krest Yuryakh Suite (102.4± 9.7 kyr), respectively, provide new substantial geochronological data and shed light on the landscape history of the Dmitry Laptev Strait region during the Marine Isotope Stage (MIS) 5. Ground ice stable-isotope data are presented together with cryolithological information for eight cryostratigraphic units and are complemented by data from nearby Bol'shoy Lyakhovsky Island. Our combined record of ice-wedge stable isotopes as proxy for past winter climate conditions covers the last about 200 thousand years and is supplemented by texture-ice stable isotopes which contain annual climate conditions overprinted by freezing processes. Our ice wedge stable-water isotope data indicate substantial variations in Northeast Siberian Arctic winter climate conditions during the late Quaternary, in particular between Glacial and Interglacial but also over the last millennia to decades. Stable isotope values of Ice Complex ice wedges indicate cold to very cold winter temperatures about 200 kyr ago (MIS7), very cold winter conditions about 100 kyr ago (MIS5), very cold to moderate winter conditions between about 60 and 30 kyr ago, and extremely cold winter temperatures during the Last Glacial Maximum (MIS2). Much warmer winter conditions are reflected by extensive thermokarst development during the MIS5c and by Holocene ice-wedge stable-isotopes. Modern ice-wedge stable isotopes are most enriched and testify the recent winter warming in the Arctic. Hence, ice-wedge based reconstructions of changes in winter climate conditions add substantial information to those derived from palaeoecological proxies stored in permafrost and allow for distinguishing between seasonal trends of past climate dynamics. Future progress in ice-wedge dating and an improved temporal resolution of ice-wedge derived climate information may help to fully explore the palaeoclimatic potential of ice wedges. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018019855 Papanicolaou, A. N. Thanos (University of Tennessee at Knoxville, Department of Civil and Environmental Engineering, Knoxville, TN). A probabilistic model for sediment entrainment; the role of bed irregularity [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2407, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
A generalized probabilistic model is developed in this study to predict sediment entrainment under the incipient motion, rolling, and pickup modes. A novelty of the proposed model is that it incorporates in its formulation the probability density function of the bed shear stress, instead of the near-bed velocity fluctuations, to account for the effects of both flow turbulence and bed surface irregularity on sediment entrainment. The proposed model incorporates in its formulation the collective effects of three parameters describing bed surface irregularity, namely the relative roughness, the volumetric fraction and relative position of sediment particles within the active layer. Another key feature of the model is that it provides a criterion for estimating the lift and drag coefficients jointly based on the recognition that lift and drag forces acting on sediment particles are interdependent and vary with particle protrusion and packing density. The model was validated using laboratory data of both fine and coarse sediment and was compared with previously published models. The study results show that for the fine sediment data, where the sediment particles have more uniform gradation and relative roughness is not a factor, all the examined models perform adequately. The proposed model was particularly suited for the coarse sediment data, where the increased bed irregularity was captured by the new parameters introduced in the model formulations. As a result, the proposed model yielded smaller prediction errors and physically acceptable values for the lift coefficient compared to the other models in case of the coarse sediment data. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018021992 Tang Liyun (Xi'an University of Science & Technology, School of Architecture and Civil Engineering, Xi'an 710054, Shaanxi, China); Yang Gengshe; Xi Jiami; Jia Hailiang; Qiu Peiyong and Wang Ke. A new method for measuring unfrozen water content of frozen soil based on soil resistivity [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-5919, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
In the field of permafrost engineering, in order to determine the unfrozen water content of frozen soil in a more economical and quick way, a resistivity-based method is proposed to predict the unfrozen water content by building the relationship of resistivity (r), water content (q) and temperature (T) through laboratory experiments. In the experiments, advanced Mile soil sample boxes are used to shape groups of soil samples with an initial water content of 5%, 10%, 15%, 20% and 25% separately. The experiment is composed of two parts. In the first part, oven drying method is used to dry the soil sample until the water content is less than 1%, and the resistivity of samples is continuously measured for each decrease of 0.5g water in soil samples; the relationship between water content (r) and resistivity (q) at normal temperatures is established and expressed as a r-q mode, which accords with power function. In the second part, the freezing method is used to freeze soil samples. When soil samples' temperature decreases from 0°C to -25°C, the resistivity of samples is continuously measured for each decrease of 0.1°C; the relationship between resistivity (r) and temperature (T) at minus degrees is established and expressed as a r-T mode, which accords with power function. The r-q model at normal temperature is introduced to indirectly reflect the r-qu model at negative degree of temperature, which has been verified through a series of experiments with the NMR method. Combined with the r-T mode at minus degree of temperature, the relationship between unfrozen water content and temperature is deduced and established as qu-T model. By contrastive analysis, the accuracy to measure unfrozen water content with the resistivity-based method is validated by the NMR method, which is used to obtain the relationship between the unfrozen water contents and temperature. Based on the research results, the surface model related to resistivity, temperature and unfrozen water content is built by MATLAB programming, and can be used to predict the unfrozen water content in practical projects. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018019962 Wu, Zi (University of California, Irvine, Department of Civil and Environmental Engineering, Irvine, CA); Foufoula-Georgiou, Efi; Parker, Gary; Singh, Arvind; Fu Xudong and Wang Guangqian. Burial effects on bedload tracer transport [abstr.]: in European Geosciences Union general assembly 2017, Geophysical Research Abstracts, 19, Abstract EGU2017-2677, 2017. Meeting: European Geosciences Union general assembly 2017, April 23-28, 2017, Vienna, Austria.
The gradual burial of tracer particles during bedload transport is a recently identified physical source of super-diffusion. It remains unclear, however how exactly this burial effect is related to the possible regimes of anomalous diffusion. In this paper we incorporate the mechanism of tracer burial into the active layer formulation for bedload transport, enabling an analytical treatment of the problem. The deduced equation governing the active layer is shown to be an advection-diffusion equation (ADE) with a sink term, and the increase of tracer concentration in the substrate layer underneath is driven by a corresponding source term which corresponds precisely to the sink term of the active layer. The solution for the variance of the tracer plume is analytically determined by calculating the relevant concentration moments based on the solved concentration distribution. It is shown that when substrate burial is accounted for, there will generally be a normal diffusion regime at very short time scales and a sub-diffusion regime at very large time scales. The appearance and characteristics of a super-diffusion regime during intermediate time scales will depend on relations among particle diffusion coefficient, burial frequency, and the virtual streamwise velocity for the tracer plume. This is in contrast to the single normal diffusion regime obtained for bedload transport when the burial process is not considered. [Copyright Author(s) 2017. CC Attribution 3.0 License: https://creativecommons.org/licenses/by/3.0/legalcode]
2018019170 Chang Qixin (China University of Geosciences, Wuhan, China); Sun Ziyong; Ma Rui; Long Xiang; Hu Yalu and Li Jieyue. Using isotopic and geochemical tracers to determine the contribution of glacier meltwater to streamflow in a headwater catchment of Heihe River basin, Northwestern China [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 34183, Final Number: H32A-05, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019137 Guillon, Sophie (Universite du Quebec a Montreal, GEOTOP, Montreal, QC, Canada); Barbecot, Florent; Larocque, Marie; Pinti, Daniele Luigi and Pili, Eric. Impact of snow cover and frozen soil on groundwater recharge [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 33127, Final Number: H23A-05, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019128 Kurylyk, Barret L. (University of Calgary, Calgary, AB, Canada); Hayashi, Masaki; Quinton, William L. and Voss, Clifford I. Simulated thaw development of a peat plateau-bog complex in a discontinuous permafrost region, Northwest Territories [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 33330, Final Number: H22A-02, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019119 Lamhonwah, Daniel (Queen's University, Kingston, ON, Canada); Lafreniere, Melissa J.; Lamoureux, Scott F. and Wolfe, Brent B. The impacts of thermal perturbation and permafrost disturbances on runoff pathways and stream water quality, Cape Bounty, Melville Island, Nunavut [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 33006, Final Number: H21A-05, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019129 McManus, Allison (Wilfrid Laurier University, Waterloo, ON, Canada); Baltzer, Jennifer Lynn and Quinton, William L. Implications of galling herbivory on ground thaw through shrub-soil heat transfers within Canada's northern boreal forest [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 34621, Final Number: H22A-03, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019120 Morrison, Matthew Q. (University of Waterloo, Waterloo, ON, Canada); Macrae, Merrin L.; Petrone, Richard M. and Fishback, LeeAnn. Hungry ponds in a thawing world; variations in subarctic pond runoff quality and quantity depend on peatland moisture and frost conditions [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 35338, Final Number: H21A-06, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019117 Peters, Daniel L. (Environment Canada, Victoria, BC, Canada); Turner, Kevin W.; Hille, Erika C.; Wrona, Fred and Kokelj, Steven V. Arctic tundra lakes in a region impacted by permafrost disturbance; application of isotope signatures for enhanced hydrological understanding [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 36247, Final Number: H14B-0210, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019121 Quinton, William L. (Wilfrid Laurier University, Waterloo, ON, Canada); Connon, Ryan; Craig, James R. and Hanisch, Jessica. Hydrologic response of a bog cascade with a dynamic contributing area in discontinuous permafrost [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 35398, Final Number: H21A-07, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
2018019122 Van Opstal, Stacey (Wilfrid Laurier University, Waterloo, ON, Canada) and Quinton, William L. Root network impact on soil thermal conductivity and active layer thaw [abstr.]: in Joint assembly AGU-GAC-MAC-CGU; abstracts listing--Reunion conjointe AGC-AGU-AMC-UGC, Abstract Volume (Geological Association of Canada), 38, Abstract 35295, Final Number: H21A-08, 2015. Meeting: Joint assembly of the American Geophysical Union, Geological Association of Canada, Mineralogical Association of Canada, and Canadian Geophysical Union, May 3-7, 2015, Montreal, QC, Canada.
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2018025829 Ruppel, Carolyn D. (U. S. Geological Survey, Reston, VA). Gas hydrate in nature: Fact Sheet - U. S. Geological Survey, Rep. No. FS 2017-3080, 4 p., illus. incl. sect., sketch maps, 5 ref., January 2018.
Gas hydrate is a naturally occurring, ice-like substance that forms when water and gas combine under high pressure and at moderate temperatures. Methane is the most common gas present in gas hydrate, although other gases may also be included in hydrate structures, particularly in areas close to conventional oil and gas reservoirs. Gas hydrate is widespread in ocean-bottom sediments at water depths greater than 300-500 meters (m; 984-1,640 feet [ft]) and is also present in areas with permanently frozen ground (permafrost). Several countries are evaluating gas hydrate as a possible energy resource in deepwater or permafrost settings. Gas hydrate is also under investigation to determine how environmental change may affect these deposits.
2018025828 Ruppel, Carolyn D. (U. S. Geological Survey, Reston, VA). The U. S. Geological Survey's Gas Hydrates Project: Fact Sheet - U. S. Geological Survey, Rep. No. FS 2017-3079, 4 p., illus., 6 ref., January 2018.
The Gas Hydrates Project at the U.S. Geological Survey (USGS) focuses on the study of methane hydrates in natural environments. The project is a collaboration between the USGS Energy Resources and the USGS Coastal and Marine Geology Programs and works closely with other U.S. Federal agencies, some State governments, outside research organizations, and international partners. The USGS studies the formation and distribution of gas hydrates in nature, the potential of hydrates as an energy resource, and the interaction between methane hydrates and the environment. The USGS Gas Hydrates Project carries out field programs and participates in drilling expeditions to study marine and terrestrial gas hydrates. USGS scientists also acquire new geophysical data and sample sediments, the water column, and the atmosphere in areas where gas hydrates occur. In addition, project personnel analyze datasets provided by partners and manage unique laboratories that supply state-of-the-art analytical capabilities to advance national and international priorities related to gas hydrates.
2018023343 McWade, T. L. (Carleton University, Ottawa, ON, Canada); Morse, P. D.; Gruber, S. and Wolfe, S. A. Identification, classification, and distribution of retrogressive creeping slumps, Lac de Gras region, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 8197, 120 p., illus. incl. tables, 14 ref., 2017.
The purpose of this Open File is to identify and map a locally common yet unclassified set of landforms first observed during summer 2015 fieldwork in continuous permafrost of the Lac de Gras region of Northwest Territories. Quantitative and qualitative data extracted from 152 landforms using aerial photographs and LiDAR data were used to describe and quantify the general form. The landforms exhibit a continuous depression situated several meters behind and parallel to a steep, curvilinear hillslopes, beneath which is a gentle footslope. The hillslopes appear to incise the margins of till blanket deposits, and the footslopes are covered with boulders. According to morphological characteristics, the mapped landforms were divided into three classes, interpreted as early, late, and final stages of an apparent time-transgressive landform evolution. Based on extracted morphological characteristics and field observations the landforms have been tentatively termed retrogressive creeping slumps.
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