Permafrost Monthly Alerts (PMAs)

2016106524 Henkner, Jessica (University of Tübingen, Department of Geosciences, Tubingen, Germany); Scholten, Thomas and Kühn, Peter. Soil organic carbon stocks in permafrost-affected soils in West Greenland: Geoderma, 282, p. 147-159, illus. incl. 6 tables, sketch map, 85 ref., November 15, 2016.

Little is known about soil organic carbon (SOC) stocks in permafrost-affected soils in Greenland. Generally, occurrence and stocks of SOC in permafrost-affected soils of the Arctic were underestimated for many years. Compared to the assumed dimension of the influence of carbon dynamics on climate change this knowledge should be substantially widened. A total of 155 soil samples were used to get a better understanding about SOC stocks, depth function and spatial distribution of SOC in permafrost-affected soils in a characteristic deglaciated valley in West Greenland southeast of Kangerlussuaq. The valley is characterized by a high variability of active layer thickness and pedo-variance mainly caused by topography. The average SOC stock of the Umimmalissuaq valley is 9.9 kg m^-2 in the upper 30 cm and around 30 kg m^-2 in the first meter, which is remarkably higher than regional predictions with 6-15.9 kg m^-2 in the first 100 cm. To account for spatial heterogeneity landscape units are developed which are most useful for grouping and predicting SOC stocks. The SOC store measured 14.2 kg m^-2 in the upper 30 cm, 11.5 kg m^-2 on north-facing slopes, and 8.4 kg m^-2 on south-facing slopes. Little SOC stocks with around 6 kg m^-2 were found under abrasion fields particularly on hilltops and moraine ridges. Soils on south-facing slopes usually have very low SOC stocks in deeper soil horizons except of organic rich horizons in rarely occurring paleosols. North-facing soils and valley bottom slopes generally have high SOC stocks of around 19 kg SOC m^-2 in soil horizons with a depth of 30-100 cm. In general, the main influencing parameter on SOC stocks is the soil organic matter input from the vegetative cover. The vegetative cover is mainly a result of topographic position and aspect related to the ice margin and katabatic winds. Soil moisture and high active layer may influence SOC stocks positively.

DOI: 10.1016/j.geoderma.2016.06.021

2016103486 Sedov, Sergey (Universidad Nacional Autónoma de México, Departamento de Edafología, Mexico); Rusakov, Alexey; Sheinkman, Vladimir and Korkka, Maria. MIS3 paleosols in the center-north of eastern Europe and Western Siberia; reductomorphic pedogenesis conditioned by permafrost?: in Dan H. Yaalon memorial issue (Stahr, Karl, editor; et al.), Catena (Giessen), 146, p. 38-47, illus. incl. 1 table, 40 ref., November 2016.

The MIS3 paleosol units comprise a prominent element of the loess-paleosol sequences throughout the Eurasian Loess Belt. To the north of the loess regions, the findings of MIS3 paleosols were few: it was supposed that geomorphic processes related to the extensive ice cover of the Last Glacial Maximum destroyed the earlier soil mantle. Recently, much smaller extent of continental ice in the east of Northern Europe and ice-free West Siberian Plain during MIS2 has been hypothesized, supposing preservation of MIS3 and earlier paleopedological records. We discovered in the center-north of European Russia (Upper Volga basin) and Western Siberia (Middle Ob basin), MIS3 paleosols within the Late Pleistocene alluvial and lacustrine sequences and correlated the studied profiles on the basis of macro- and micromorphological characteristics and radiocarbon datings of the paleosol organic materials. Paleosols are represented by hydromorphic profiles with Histic horizons and gleyic color pattern. Conspicuously, they are developed in the well drained geomorphic positions, where modern soils are non-gleyic. We suppose that the presence of permafrost was responsible for water logging and generation of reductomorphic soil environment. We further hypothesize a northern zone of MIS3 soil mantle, comprised of Histic and Reductaquic Cryosols different from synchronous Cambisols and Chernozems formed within loess sequences to the south.

DOI: 10.1016/j.catena.2016.03.022

2016108342 Peng, F. (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Key Laboratory of Desert and Desertification, Lanzhou, China); You, Q. G.; Xu, M. H.; Zhou, X. H.; Wang, T.; Guo, J. and Xue, X. Effects of experimental warming on soil respiration and its components in an alpine meadow in the permafrost region of the Qinghai-Tibet Plateau: European Journal of Soil Science, 66(1), p. 145-154, illus. incl. 3 tables, sketch map, 43 ref., January 2015.

The response of soil respiration (R_s) and its components (autotrophic [R_a] and heterotrophic respiration [R_h]) to climate warming is one of the uncertainties in ecosystem carbon (C) models. Here we conducted a warming experiment in an alpine meadow dominated by Koresbia in the permafrost region of the Qinghai-Tibet Plateau (QTP) to examine effects of warming on R_s and its components. Infrared heaters were used to simulate a 2°C warming of the surface soil temperature. Deep collars (50 cm to exclude root growth) were inserted into soil to measure R_h:R_a, which was calculated by subtracting R_h from R_s. Average R_s and its components (R_a and R_h) were significantly stimulated by 21.5, 27 and 15.6%, respectively, in warmed plots from January 2011 to October 2013. The contribution of R_h to R_s decreased in the warmed plots because of the smaller relative increase in R_h than in R_a. Annual soil C release increased by 263 and 247 g C m^-2 in 2011 and 2012, respectively. Stimulation in R_a and R_h was related to the significant increase in root biomass (0-50 cm) and in labile soil C in the deeper layer (40-50 cm). The temperature sensitivities (Q₁₀) of R_s and its components all increased with larger values in R_a, followed by R_s and R_h. Our results suggest a positive feedback between soil C release and climatic warming in the permafrost region of the QTP. Abstract Copyright (2014), British Society of Soil Science.

DOI: 10.1111/ejss.12187

2016104922 Fiddes, J. (University of Zurich, Department of Geography, Zurich, Switzerland); Endrizzi, S. and Gruber, S. Large-area land surface simulations in heterogeneous terrain driven by global data sets; application to mountain permafrost: The Cryosphere (Online), 9(1), p. 411-426, illus. incl. 3 tables, 62 ref., 2015.

Numerical simulations of land surface processes are important in order to perform landscape-scale assessments of earth systems. This task is problematic in complex terrain due to (i) high-resolution grids required to capture strong lateral variability, and (ii) lack of meteorological forcing data where they are required. In this study we test a topography and climate processor, which is designed for use with large-area land surface simulation, in complex and remote terrain. The scheme is driven entirely by globally available data sets. We simulate air temperature, ground surface temperature and snow depth and test the model with a large network of measurements in the Swiss Alps. We obtain root-mean-squared error (RMSE) values of 0.64 °C for air temperature, 0.67-1.34 °C for non-bedrock ground surface temperature, and 44.5 mm for snow depth, which is likely affected by poor input precipitation field. Due to this we trial a simple winter precipitation correction method based on melt dates of the snowpack. We present a test application of the scheme in the context of simulating mountain permafrost. The scheme produces a permafrost estimate of 2000 km², which compares well to published estimates. We suggest that this scheme represents a useful step in application of numerical models over large areas in heterogeneous terrain.

URL: http://www.the-cryosphere.net/9/411/2015/tc-9-411-2015.pdf

2016104914 Günther, F. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Overduin, P. P.; Yakshina, I. A.; Opel, T.; Baranskaya, A. V. and Grigoriev, M. N. Observing Muostakh disappear; permafrost thaw subsidence and erosion of a ground-ice-rich island in response to arctic summer warming and sea ice reduction: The Cryosphere (Online), 9(1), p. 151-178, illus. incl. 3 tables, sketch maps, 125 ref., 2015.

Observations of coastline retreat using contemporary very high resolution satellite and historical aerial imagery were compared to measurements of open water fraction, summer air temperature, and wind. We analysed seasonal and interannual variations of thawing-induced cliff top retreat (thermo-denudation) and marine abrasion (thermo-abrasion) on Muostakh Island in the southern central Laptev Sea. Geomorphometric analysis revealed that total ground ice content on Muostakh is made up of equal amounts of intrasedimentary and macro ground ice and sums up to 87%, rendering the island particularly susceptible to erosion along the coast, resulting in land loss. Based on topographic reference measurements during field campaigns, we generated digital elevation models using stereophotogrammetry, in order to block-adjust and orthorectify aerial photographs from 1951 and GeoEye, QuickBird, WorldView-1, and WorldView-2 imagery from 2010 to 2013 for change detection. Using sea ice concentration data from the Special Sensor Microwave Imager (SSM/I) and air temperature time series from nearby Tiksi, we calculated the seasonal duration available for thermo-abrasion, expressed as open water days, and for thermo-denudation, based on the number of days with positive mean daily temperatures. Seasonal dynamics of cliff top retreat revealed rapid thermo-denudation rates of -10.2 ± 4.5 m a^-1 in mid-summer and thermo-abrasion rates along the coastline of -3.4 ± 2.7 m a^-1 on average during the 2010-2013 observation period, currently almost twice as rapid as the mean rate of -1.8 ± 1.3 m a^-1 since 1951. Our results showed a close relationship between mean summer air temperature and coastal thermo-erosion rates, in agreement with observations made for various permafrost coastlines different to the East Siberian Ice Complex coasts elsewhere in the Arctic. Seasonality of coastline retreat and interannual variations of environmental factors suggest that an increasing length of thermo-denudation and thermo-abrasion process simultaneity favours greater coastal erosion. Coastal thermo-erosion has reduced the island's area by 0.9 km² (24%) over the past 62 years but shrank its volume by 28 x 10⁶ m³ (40%), not least because of permafrost thaw subsidence, with the most pronounced with rates of >&eq;- 11 cm a^-1 on yedoma uplands near the island's rapidly eroding northern cape. Recent acceleration in both will halve Muostakh Island's lifetime to less than a century.

URL: http://www.the-cryosphere.net/9/151/2015/tc-9-151-2015.pdf

2016104911 Magnin, F. (Université de Savoie, Laboratoire Environnements, Dynamiques, Territoires, Montagnes (EDYTEM), Le Bourget-du-Lac, France); Deline, P.; Ravanel, L.; Noetzli, J. and Pogliotti, P. Thermal characteristics of permafrost in the steep alpine rock walls of the Aiguille du Midi (Mont Blanc Massif, 3842 m a.s.l): The Cryosphere (Online), 9(1), p. 109-121, illus. incl. 3 tables, 41 ref., 2015.

Permafrost and related thermo-hydro-mechanical processes are thought to influence high alpine rock wall stability, but a lack of field measurements means that the characteristics and processes of rock wall permafrost are poorly understood. To help remedy this situation, in 2005 work began to install a monitoring system at the Aiguille du Midi (3842 m a.s.l). This paper presents temperature records from nine surface sensors (eight years of records) and three 10 m deep boreholes (4 years of records), installed at locations with different surface and bedrock characteristics. In line with previous studies, our temperature data analyses showed that: micro-meteorology controls the surface temperature, active layer thicknesses are directly related to aspect and ranged from >2 m to nearly 6 m, and that thin accumulations of snow and open fractures are cooling factors. Thermal profiles empirically demonstrated the coexistence within a single rock peak of warm and cold permafrost (about -1.5 to -4.5 °C at 10 m depth) and the resulting lateral heat fluxes. Our results also extended current knowledge of the effect of snow, in that we found similar thermo-insulation effects as reported for gentle mountain areas. Thick snow warms shaded areas, and may reduce active layer refreezing in winter and delay its thawing in summer. However, thick snow thermo-insulation has little effect compared to the high albedo of snow which leads to cooler conditions at the rock surface in areas exposed to the sun. A consistent inflection in the thermal profiles reflected the cooling effect of an open fracture in the bedrock, which appeared to act as a thermal cutoff in the sub-surface thermal regime. Our field data are the first to be obtained from an Alpine permafrost site where borehole temperatures are below -4 °C, and represent a first step towards the development of strategies to investigate poorly known aspects in steep bedrock permafrost such as the effects of snow cover and fractures.

URL: http://www.the-cryosphere.net/9/109/2015/tc-9-109-2015.pdf

2016104810 Karra, S. (Los Alamos National Laboratory, Computational Earth Science Group, Los Alamos, NM); Painter, S. L. and Lichtner, P. C. Three-phase numerical model for subsurface hydrology in permafrost-affected regions (PFLOTRAN-ICE v1.0): The Cryosphere (Online), 8(5), p. 1935-1950, illus., 44 ref., 2014. Includes appendices.

Degradation of near-surface permafrost due to changes in the climate is expected to impact the hydrological, ecological and biogeochemical responses of the Arctic tundra. From a hydrological perspective, it is important to understand the movement of the various phases of water (gas, liquid and ice) during the freezing and thawing of near-surface soils. We present a new non-isothermal, single-component (water), three-phase formulation that treats air as an inactive component. This single component model works well and produces similar results to a more complete and computationally demanding two-component (air, water) formulation, and is able to reproduce results of previously published laboratory experiments. A proof-of-concept implementation in the massively parallel subsurface flow and reactive transport code PFLOTRAN is summarized, and parallel performance of that implementation is demonstrated. When water vapor diffusion is considered, a large effect on soil moisture dynamics is seen, which is due to dependence of thermal conductivity on ice content. A large three-dimensional simulation (with around 6 million degrees of freedom) of seasonal freezing and thawing is also presented.

URL: http://www.the-cryosphere.net/8/1935/2014/tc-8-1935-2014.pdf

2016110988 Miller, Scot M. (Carnegie Institution for Science, Department of Global Ecology, Stanford, CA); Miller, Charles E.; Commane, Roisin; Chang, Rachel Y. W.; Dinardo, Steven J.; Henderson, John M.; Karion, Anna; Lindaas, Jakob; Melton, Joe R.; Miller, John B.; Sweeney, Colm; Wofsy, Steven C. and Michalak, Anna M. A multiyear estimate of methane fluxes in Alaska from CARVE atmospheric observations: Global Biogeochemical Cycles, 30(10), p. 1441-1453, illus. incl. 1 table, sketch map, 69 ref., October 2016.

Methane (CH₄) fluxes from Alaska and other arctic regions may be sensitive to thawing permafrost and future climate change, but estimates of both current and future fluxes from the region are uncertain. This study estimates CH₄ fluxes across Alaska for 2012-2014 using aircraft observations from the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) and a geostatistical inverse model (GIM). We find that a simple flux model based on a daily soil temperature map and a static map of wetland extent reproduces the atmospheric CH₄ observations at the statewide, multiyear scale more effectively than global-scale process-based models. This result points to a simple and effective way of representing CH₄ fluxes across Alaska. It further suggests that process-based models can improve their representation of key processes and that more complex processes included in these models cannot be evaluated given the information content of available atmospheric CH₄ observations. In addition, we find that CH₄ emissions from the North Slope of Alaska account for 24% of the total statewide flux of 1.74 ± 0.26 Tg CH₄ (for May-October). Global-scale process models only attribute an average of 3% of the total flux to this region. This mismatch occurs for two reasons: process models likely underestimate wetland extent in regions without visible surface water, and these models prematurely shut down CH₄ fluxes at soil temperatures near 0°C. Lastly, we find that the seasonality of CH₄ fluxes varied during 2012-2014 but that total emissions did not differ significantly among years, despite substantial differences in soil temperature and precipitation. Abstract Copyright (2016), . American Geophysical Union. All Rights Reserved.

DOI: 10.1002/2016GB005419

2016100058 Ewertowski, Marek W. (Adam Mickiewicz University, Faculty of Geographical and Geological Sciences, Poznan, Poland) and Tomczyk, Aleksandra M. Quantification of the ice-cored moraines' short term dynamics in the high Arctic glaciers Ebbabreen and Ragnarbreen, Petuniabukta, Svalbard: Geomorphology, 234, p. 211-227, illus. incl. 1 table, sketch maps, 86 ref., April 1, 2015. Includes appendices.

Extensive ice-cored moraine complexes are common elements, marking the last advance of many Svalbard glaciers. Sediment gravity flows are among the most dynamic processes, transforming these landforms. The short-term (yearly and weekly) dynamics of mass-wasting processes were studied in a cm-scale using repetitive topographic scanning. We monitored several active sites on the forelands of two glaciers, Ebbabreen and Ragnarbreen, both of which are located near Petuniabukta at the northern end of Billefjorden in Spitsbergen. The surveys indicate high dynamic rates of landforms' transformation. The mean annual volume loss of sediments and dead-ice for the most active parts of the moraines was up to 1.8 m a^-1. However, most of the transformation occurred during summer, with the short-term values of mean elevation changes as high as - 104 mm day^-1. In comparison, the dynamics of the other (i.e. non-active) parts of the ice-cored moraines were much lower, namely, the mean annual lowering (attributed mainly to dead-ice downwasting) was up to 0.3 m a^-1, whereas lowering during summer was up to 8 mm day^-1. Our results indicate that in the case of the studied glaciers, backwasting was much more effective than downwasting in terms of landscape transformation in the glacier forelands. However, despite the high activity of localised mass movement processes, the overall short-term dynamics of ice-cored moraines for the studied glaciers were relatively low. We suggest that as long as debris cover is sufficiently thick (thicker than the permafrost's active layer depths), the mass movement activity would occur only under specific topographic conditions and/or due to occurrence of external meltwater sources and slope undercutting. In other areas, ice-cored moraines remain a stable landsystem component in a yearly to decadal time-scale. Abstract Copyright (2015) Elsevier, B.V.

DOI: 10.1016/j.geomorph.2015.01.023

2016100048 Sessford, Evangeline G. (University Centre in Svalbard, Department of Arctic Geology, Longyearbyen, Norway); Strzelecki, Mateusz C. and Hormes, Anne. Reconstruction of Holocene patterns of change in a high Arctic coastal landscape, southern Sassenfjorden, Svalbard: Geomorphology, 234, p. 98-107, illus. incl. 1 table, geol. sketch map, 48 ref., April 1, 2015.

Abrupt shifts in sediment supply, relative sea level, permafrost regime, glacier state, snow cover and sea ice conditions associated with Holocene climate changes control processes operating on High Arctic coasts and make reconstructions of their past evolution a significant research challenge. This study attempts to describe the development of the coastal zone in southern Sassenfjorden, Svalbard, throughout the Holocene focusing on the styles of adjustment to major landscape changes. Five marine terraces (MT1-5) are identified and assessed. Spatial and chronological analysis suggests that the highest terrace, MT5, is pre-LGM (Last Glacial Maximum) and that MT4-3 underwent rapid uplift (151 and 11.4 mm/year, respectively) shortly prior to 11 061 ± 174 cal. yr BP and became fully terrestrial by 9100 years ago (as indicated by emergence rates) during the Holocene Thermal Maximum (HTM). Uplift rates for MT2-1 slowed to 5 and 2 mm/year, respectively, with suggested emergence between 7200 and 6800 cal. yr BP. A final 2 m uplift of the relict alluvial plain probably happened during the Medieval Warm Period (1200-950 cal. yr BP). Most recent coastal development (AD 1912-2012) is characterised by episodes of coastal erosion on the cliff and progradation of the Noiselva delta. Interactions between sea ice, snow cover, permafrost, wind and wave regimes are assessed to understand their implications on future coastal development in a warming climate. Abstract Copyright (2015) Elsevier, B.V.

DOI: 10.1016/j.geomorph.2014.12.046

2016104805 Barnhart, Katherine R. (University of Colorado at Boulder, Department of Geological Sciences, Boulder, CO); Overeem, I. and Anderson, R. S. The effect of changing sea ice on the physical vulnerability of Arctic coasts: The Cryosphere (Online), 8(5), p. 1777-1799, illus. incl. sketch maps, 68 ref., 2014.

Sea ice limits the interaction of the land and ocean water in the Arctic winter and influences this interaction in the summer by governing the fetch. In many parts of the Arctic, the open-water season is increasing in duration and summertime sea-ice extents are decreasing. Sea ice provides a first-order control on the physical vulnerability of Arctic coasts to erosion, inundation, and damage to settlements and infrastructures by ocean water. We ask how the changing sea-ice cover has influenced coastal erosion over the satellite record. First, we present a pan-Arctic analysis of satellite-based sea-ice concentration specifically along the Arctic coasts. The median length of the 2012 open-water season, in comparison to 1979, expanded by between 1.5 and 3-fold by Arctic Sea sector, which allows for open water during the stormy Arctic fall. Second, we present a case study of Drew Point, Alaska, a site on the Beaufort Sea, characterized by ice-rich permafrost and rapid coastal-erosion rates, where both the duration of the open-water season and distance to the sea-ice edge, particularly towards the northwest, have increased. At Drew Point, winds from the northwest result in increased water levels at the coast and control the process of submarine notch incision, the rate-limiting step of coastal retreat. When open-water conditions exist, the distance to the sea ice edge exerts control on the water level and wave field through its control on fetch. We find that the extreme values of water-level setup have increased consistently with increasing fetch.

URL: http://www.the-cryosphere.net/8/1777/2014/tc-8-1777-2014.pdf

2016106496 Liu Jiankun (Beijing Jiaotong University, School of Civil Engineering, Beijing, China); Chang Dan and Yu Qianmi. Influence of freeze-thaw cycles on mechanical properties of a silty sand: Engineering Geology, 210, p. 23-32, illus. incl. 6 tables, 27 ref., August 5, 2016.

Freeze-thaw cycling is a very common phenomenon in seasonally frozen soil areas and it will affect the mechanical properties of soils which should be taken into account for geotechnical engineering. To study the variation of mechanical properties of seasonally frozen soils, fine-grained silty sand was compacted in the lab and was then exposed to a maximum of 12 closed-system freeze-thaw cycles. The stress-strain curve, failure strength, elastic modulus, cohesion and angle of internal friction were measured for samples before and after the freeze-thaw cycles. The mechanical properties were considerably affected by the number of freeze-thaw cycles, whereas the influence of cooling temperature was not obvious. The highest decrease rate of elastic modulus was about 26%-45% and for failure strength it reached at 32%-45% compared to the unfrozen soil which did not experience the freeze-thaw cycles. The cohesion decreased after the first few freeze-thaw cycles and then kept nearly stable after about 9-12 cycles while the internal friction angle decreased at first and then increased during the freeze-thaw cycles, reaching the minimum values at about the 7 cycles. The method of significance was used to analyze the influence of different factors. Results showed that the number of freeze-thaw cycles had significant influence on the mechanical properties and the cooling temperature had less influence. The normalized stress-strain relationship considering the influence of freeze-thaw cycling as well as confining pressure was established and can predict the stress-strain relation well compared with the experimental data.

DOI: 10.1016/j.enggeo.2016.05.019

2016106378 Ling Ma (Chinese Academy of Sciences, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Jilin Qi; Fan Yu and Xiaoliang Yao. Experimental study on variability in mechanical properties of a frozen sand as determined in triaxial compression tests: Acta Geotechnica (Berlin), 11(1), p. 61-70, illus. incl. 2 tables, 22 ref., February 2016.

Large uncertainty exists in soil testing due to the randomness in sampling and system errors, especially in tests on frozen soils. In order to reduce the randomness and improve the test accuracy, the sample preparation method is improved to obtain more homogeneous samples. The standard Chinese sand is used as the soil. An environmental material test apparatus with three-point temperature control was used. Four temperatures and four confining pressures are used for the triaxial compression tests, which makes 16 combinations. For each combination, five repeat tests were carried out to examine the scattering of the mechanical properties of the frozen sand. It is found that under a certain confining pressure, the scattering increased with the increase in temperature and vice versa. Under a certain combination of temperature at -0.5 °C and confining pressure of 10 MPa, the stress-strain curves are so different that similarity in the curves does not exist. This phenomenon is not scattering because sample randomness or system errors cannot explain it any more and is therefore called variability. It is attributed to pressure melting, pressure crush of soil particles as well as severe phase changes caused by small temperature variations. The difference in the test results is considered as an inherent feature of frozen soils. Strength and strain energy are used, along with temperature and confining pressure to analyze the cause of variability. This work shows that further work must be carried out to develop an optimum testing program in order to make a reasonable analysis for engineering constructions in which frozen soils are involved. Copyright 2015 Springer-Verlag Berlin Heidelberg

DOI: 10.1007/s11440-015-0391-y

2016102775 Gao Yongheng (Chinese Academy of Sciences, Institute of Mountain Hazards and Environment, Chengdu, China); Zeng Xiaoyang; Xie Qingyan and Ma Xingxing. Release of carbon and nitrogen from Alpine soils during thawing periods in the eastern Qinghai-Tibet Plateau: Water, Air and Soil Pollution, 226(7), Article 226:209, 39 ref., July 2015. Based on Publisher-supplied data.

Soil thawing can affect the turnover of soil carbon (C) and nitrogen (N) and their release into the atmosphere. However, little has been known about the release of C and N during the thawing of alpine soils in the Qinghai-Tibet Plateau. This study investigated the effects of soil thawing on the release of CO₂, CH₄, and N₂O from alpine peatland soils and alpine meadow soils through an indoor experiment and determined the changes in the dissolved organic C (DOC), dissolved organic N (DON), NO₃^--N, NH₄⁺-N, and NO₂^--N concentrations in the soils after soil thawing. The freeze-thaw treatments were performed by incubating the soil columns at mild (-5 °C) and severe (-15 °C) for 14 days, and then at 5 °C for 18 days. The control columns were incubated at 5 °C. During thawing, the cumulative CO₂ emissions from the severely frozen alpine peatland soils and alpine meadow soils were 36 and 85 % higher than those from the control soils, and the cumulative N₂O emissions were 3.9 and 5.8 times higher than those from the control soils. However, the thawing after mild freezing produced no significant effects. The two freezing temperatures significantly increased the release of CH₄ from the alpine peatland soils, but the thawing of the severely frozen soils reduced the CH₄ uptake of the alpine meadow soils by 27 %. After the severely frozen alpine peatland soils thawed, the concentrations of DOC, DON, NO₃^--N, NH₄⁺-N, and NO₂^--N increased significantly, but NO₂^--N showed no significant changes for the alpine meadow soils. After thawing with mild freezing, DOC in the alpine peatland soils and NH₄⁺-N, NO₂^--N, and DOC in the alpine meadow soils showed no significant changes. This study indicates that the potential for release of C and N from alpine soils during thawing periods strongly depends on the freezing temperature and soil types. Copyright 2015 Springer International Publishing Switzerland

DOI: 10.1007/s11270-015-2479-2

2016108015 Li Shuangyang (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Lai Yuanming; Pei Wansheng; Zhang Shujuan and Zhong Hua. Moisture-temperature changes and freeze-thaw hazards on a canal in seasonally frozen regions: Natural Hazards, 72(2), p. 287-308, illus. incl. 2 tables, 41 ref., June 2014.

Freeze-thaw action is a complex moisture-heat-mechanics interaction process, which has caused prevailing and severe damages to canals in seasonally frozen regions. Up to now, the detailed frost damage mechanism has not been well disclosed. To explore the freeze-thaw damage mechanism of the canal in cold regions, a numerical moisture-heat-mechanics model is established and corresponding computer program is written. Then, a representative canal in the northeast of China is taken as an example to simulate the freeze-thaw damage process. Meanwhile, the robustness of the numerical model and program is tested by some in situ data. Lastly, the numerical results show that there are dramatic water migration and redistribution in the seasonal freeze-thaw variation layer, causing repetitive frost heave and thaw settlement, and tension-compression stresses. Therefore, the strengths of soil are reduced after several freeze-thaw cycles. Further, the heavy denudation damage and downslope movement of the canal slope would be quite likely triggered in seasonally frozen regions. These zones should be monitored closely to ensure safe operation. As a preliminary study, the numerical model and results in this paper may be a reference for design, maintenance, and research on other canals in seasonally frozen regions. Copyright 2014 Springer Science+Business Media Dordrecht

DOI: 10.1007/s11069-013-1021-3

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2016100943 Ekwurzel, Brenda (Union of Concerned Scientists, Washington, DC); Yona, Leehi; Natali, Susan; Holmes, Robert Max and Schuur, Edward. Arctic council nations could encourage development of climate indicator; flux to the atmosphere from Arctic permafrost carbon [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract PA31D-07, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Permafrost regions store almost twice the carbon in the atmosphere (Tarnocai et al 2009). As climate warms a proportion of this carbon will be released as carbon dioxide and methane. The Arctic Council may be best suited to harness international scientific collaboration for policy relevant knowledge about the global impacts of permafrost thaw. Scientists in Arctic Council and observer states have historically collaborated on permafrost research (e.g. Permafrost Carbon Network, part of Study of Environmental Arctic Change (SEARCH) project). This work increased knowledge of permafrost carbon pool size and vulnerability. However, data gaps persist across the Arctic. Despite gaps, numerous studies directly inform international policy negotiations aiming to stay below 2°C. Some suggest "permafrost carbon feedback" may comprise 3 to 11% of total allowed emissions through 2100 under a RCP4.5 (Schaefer et al 2014). Understanding and accounting for future permafrost atmospheric carbon release requires science and policy coordination that the Arctic Council could incentivize. For example, Council nations could convene scientists and stakeholders to develop a Permafrost-Climate Indicator providing more direct decision support than current permafrost indicators, and identify research needed for a periodic estimate of Arctic permafrost CO₂ and CH₄ emissions. This presentation covers current challenges scientists and policymakers may face to develop a practical and robust Permafrost Climate Indicator. For example, which timescales are most appropriate for international emissions commitments? Do policy-relevant timescales align with current scientific knowledge? What are the uncertainties and how can they be decreased? We present likely strengths and challenges of a Permafrost Climate Indicator co-developed by scientists and stakeholders. Potential greenhouse gas atmospheric flux from Arctic permafrost carbon may be greater than some nations' United Nations emissions reductions commitments. Investing in better understanding greenhouse gas emissions from thawing permafrost is relevant for all nations and essential to setting global emission targets.

2016100946 Zubrzycki, Sebastian (University of Hamburg, Hamburg, Germany). Two years of CarboPerm; achievements and further steps of an interdisciplinary Russian-German project on the formation, turnover and release of carbon in Siberian permafrost landscape [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract PA33A-2175, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Permafrost-affected soils of the northern hemisphere have accumulated large pools of soil organic carbon (SOC) since continuous low temperatures in the permafrost prevented organic matter (OM) decomposition. According to recent estimates these soils contain 1300 ± 200 Pg of SOC, or about twice as much the carbon within the global vegetation. Rising arctic temperatures will likely result in increased permafrost thawing with the consequence of increased mobilization and degradation of formerly frozen OM. This degradation process will presumably result in an increased formation of trace gases such as methane and carbon dioxide which can be released to the atmosphere. Rising trace gas concentrations due to permafrost thawing would thereby induce a positive feedback on climate warming. CarboPerm, is a joint German-Russian research project funded by the German Federal Ministry of Education and Research. It comprises multi-disciplinary investigations on the formation, turnover and release of SOC in Siberian permafrost. It aims to gain increased understanding of how permafrost-affected landscapes will respond to global warming and how this response will influence the local, regional and global trace gas balance. CarboPerm strengthens permafrost research in underrepresented areas which are hardly accessible to international researchers. The obtained results improve our understanding of the future development of the sensitive and economically relevant arctic permafrost regions. With this contribution we want to inform the interested community about the new knowledge resulting from results of all scientific work packages: (i) the origin, properties, and dynamics of fossil carbon, (ii) the age and quality of organic matter, (iii) the recent carbon dynamics in permafrost landscapes, (iv) the microbial transformation of organic carbon in permafrost, and (v) process-driven modeling of soil carbon dynamics in permafrost areas.

2016105914 Murphy, Karen Anne (U. S. Fish and Wildlife Service, Washington, DC) and Reynolds, Joel. Shrinking sea ice, thawing permafrost, bigger storms, and extremely limited data; addressing information needs of stakeholders in western Alaska through participatory decisions and collaborative science [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract PA11C-03, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Communities, Tribes, and decision makers in coastal western Alaska are being impacted by declining sea ice, sea level rise, changing storm patterns and intensities, and increased rates of coastal erosion. Relative to their counterparts in the contiguous USA, their ability to plan for and respond to these changes is constrained by the region's generally meager or non-existent information base. Further, the information needs and logistic challenges are of a scale that perhaps can be addressed only through strong, strategic collaboration. Landscape Conservation Cooperatives (LCCs) are fundamentally about applied science and collaboration, especially collaborative decision making. The Western Alaska LCC has established a process of participatory decision making that brings together researchers, agency managers, local experts from Tribes and field specialists to identify and prioritize shared information needs; develop a course of action to address them by using the LCC's limited resources to catalyze engagement, overcome barriers to progress, and build momentum; then ensure products are delivered in a manner that meets decision makers' needs. We briefly review the LCC's activities & outcomes from the stages of (i) collaborative needs assessment (joint with the Alaska Climate Science Center and the Alaska Ocean Observing System), (ii) strategic science activities, and (iii) product refinement and delivery. We discuss lessons learned, in the context of our recent program focused on 'Changes in Coastal Storms and Their Impacts' and current collaborative efforts focused on delivery of Coastal Resiliency planning tools and results from applied science projects. Emphasis is given to the various key interactions between scientists and decision makers / managers that have been promoted by this process to ensure alignment of final products to decision maker needs.

2016105915 Druckenmiller, Matthew L. (Rutgers University, New Brunswick, NJ); Wiggins, Helen V.; Eicken, Hajo; Francis, Jennifer Ann; Huntington, Henry and Scambos, Ted A. Supporting decisions through the study of environmental Arctic change (SEARCH) program; a history and way forward [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract PA13A-2179, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

The Study of Environmental Arctic Change (SEARCH), ongoing since the early-2000s, aims to develop scientific knowledge to help society understand and respond to the rapidly changing Arctic. Through collaboration with the research community, funding agencies, national and international science programs, and other stakeholders, SEARCH facilitates research activities across local-to-global scales, with increasing emphasis on addressing the information needs of policy and decision-makers. This talk will explore the program's history, spanning its earliest efforts to understand interrelated atmospheric, oceanic, and terrestrial changes in the Arctic to more recent objectives of providing stakeholder-relevant information, such as community-wide summaries of the expected arctic summer sea ice minimum or up-to-date information on sea ice conditions to Alaska Native walrus hunters in the Bering and Chukchi Seas. We will discuss SEARCH's recent shift toward a "Knowledge to Action" vision and implementation of focused Action Teams to: (1) improve understanding, advance prediction, and explore consequences of changing arctic sea ice; (2) document and understand how degradation of near-surface permafrost will affect arctic and global systems; and (3) improve predictions of future land-ice loss and impacts on sea level. Tracking and evaluating how scientific information from such research reaches stakeholders and informs decisions are critical for interactions that allow the research community to keep pace with an evolving landscape of arctic decision-makers. Examples will be given for the new directions these Action Teams are taking regarding science communication and approaches for research community collaboration to synthesize research findings and promote arctic science and interdisciplinary scientific discovery.

2016109498 McAlpin, David B. (University of Alaska Fairbanks, Fairbanks, AK); Meyer, F. J.; Darrow, M. M.; Gong, W. and Daanen, R. P. Using SAR interferometry to assess infrastructure hazards from frozen debris lobes in northern Alaska [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract IN11A-1770, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Frozen debris lobes (FDLs) are slow-moving earth flows along permafrost-affected slopes. FDLs consist of soil, rock, debris, and potentially ice, although only preliminary surface investigations have been conducted on these features thus far. Within the corridor of the 667 km Dalton Highway in Alaska's Brooks Range, we have identified 43 FDLs, with 23 occurring less than one mile upslope of the Dalton Highway and the Trans-Alaska Oil Pipeline (TAP), which runs parallel to the Dalton Highway. Due to their proximity to the highway and pipeline, FDLs pose significant risks to these key infrastructure assets. The closest FDL to the highway, FDL-A, is less than 41.5 m from the embankment when measured in August 2014, and could encroach upon the Dalton Highway/TAP within one year. Upon reaching the highway, FDLs could significantly impede the flow of essential goods and services to the oil and gas fields on the North Slope, creating severe economic losses. This study addresses the following two research goals: In an initial step, we assessed the performance of InSAR for FDL analysis as a function of data resolution, season, and vegetation cover. We were able to conclude that moderate resolution SAR systems are sufficient for monitoring FDLs during winter, when top surfaces are frozen and slopes are moving more consistently. In summer, however, surface flows show stronger spatial variation, and higher resolution sensors are required to preserve coherence and examine details. Subsequently, we began a long-term analysis of FDL behavior using SAR acquisitions over the last 20 years, expanded to include more recent data from the high-resolution TerraSAR-X sensor. We calculated flow parameters from the InSAR data and combined them with geological information from field measurements to perform a geophysical analysis of FDLs and assess their hazard potential. Our preliminary results show that (1) FDLs have been progressively moving down slope since the 1990s; (2) the down slope movement rates of FDLs vary significantly (up to a factor of 4) throughout the seasons with fastest flow typically occurring in late fall, and slowest motion being observed in the February-March timeframe; and (3) the surface motion of FDLs also varies significantly in space, with stronger spatial variation in summer than in winter.

2016109358 Sterckx, Arnaud (Laval University, Quebec City, QC, Canada); Lemieux, Jean Michel and Vaikmae, Rein. The impact of glaciations and glacial processes on groundwater flow dynamics; a numerical investigation [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H51I-1515, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Numerical models are widely used to investigate the impact of glaciations on groundwater flow systems because they can simulate complex glacial processes. However, it isn't clear which of these processes are relevant to adequately capture groundwater flow dynamics. Given the complexity of representing these processes in a numerical model and the paucity of field data available for their validation, it is of prime interest to assess how they impact groundwater flow and if any of these processes could be neglected. In order to assess the specific impact of glacial processes on groundwater flow dynamics, those processes were included in the numerical model FEFLOW and simulations were conducted in a simple conceptual model representing a 21 ky glacial cycle in a sedimentary basin. The following processes have been simulated: subglacial recharge, linear and non-linear compaction of the porous medium under the weight of the ice, isostasy, proglacial lakes, as well as permafrost. Solute transport was simulated along with groundwater flow to track groundwater originating from the ice-sheet. To interpret the results, a base case scenario considering only subglacial recharge was selected and compared with the other scenarios, where individual glacial processes were simulated. When comparing the results at the end of the simulations, it appears that most of the aforementioned glacial processes don't lead to a significant difference in meltwater distribution with respect to the base case. Only hydromechanical coupling brings some noticeable change. Conversely, the type and the value of the boundary condition applied at the base of the ice-sheet play a major role in groundwater flow dynamics. The presence of confining hydrogeological units also seems to be a key to understand the long-term effect of glaciations. These results suggest that some of the glacial processes may be neglected for the simulation of groundwater flow dynamics during a glacial period.

2016109248 Anh Phuong Tran (Lawrence Berkeley National Laboratory, Berkeley, CA); Dafflon, Baptiste; Hubbard, Susan S.; Bisht, Gautam; Peterson, John; Ulrich, Craig; Romanovsky, Vladimir E.; Kneafsey, Timothy J. and Wu, Yuxin. Coupled monitoring and inverse modeling to investigate surface-subsurface hydrological and thermal dynamics in the Arctic tundra [abstr.]: in AGU 2015 fall meeting, American Geophysical Union Fall Meeting, 2015, Abstract H13E-1596, December 2015. Meeting: American Geophysical Union 2015 fall meeting, Dec. 14-18, 2015, San Francisco, CA.

Quantitative characterization of the soil surface-subsurface hydrological and thermal processes is essential as they are primary factors that control the biogeochemical processes, ecological landscapes and greenhouse gas fluxes. In the Artic region, the surface-subsurface hydrological and thermal regimes co-interact and are both largely influenced by soil texture and soil organic content. In this study, we present a coupled inversion scheme that jointly inverts hydrological, thermal and geophysical data to estimate the vertical profiles of clay, sand and organic contents. Within this inversion scheme, the Community Land Model (CLM4.5) serves as a forward model to simulate the land-surface energy balance and subsurface hydrological-thermal processes. Soil electrical conductivity (from electrical resistivity tomography), temperature and water content are linked together via petrophysical and geophysical models. Particularly, the inversion scheme accounts for the influences of the soil organic and mineral content on both of the hydrological-thermal dynamics and the petrophysical relationship. We applied the inversion scheme to the Next Generation Ecosystem Experiments (NGEE) intensive site in Barrow, AK, which is characterized by polygonal-shaped arctic tundra. The monitoring system autonomously provides a suite of above-ground measurements (e.g., precipitation, air temperature, wind speed, short-long wave radiation, canopy greenness and eddy covariance) as well as below-ground measurements (soil moisture, soil temperature, thaw layer thickness, snow thickness and soil electrical conductivity), which complement other periodic, manually collected measurements. The preliminary results indicate that the model can well reproduce the spatiotemporal dynamics of the soil temperature, and therefore, accurately predict the active layer thickness. The hydrological and thermal dynamics are closely linked to the polygon types and polygon features. The results also enable the quantification of the role of organic material in hydrological - thermal processes in the Arctic region.

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2016108620 Riedel, M. (Geological Survey of Canada, Sidney, BC, Canada); Villinger, H.; Asshoff, K.; Kaul, N. and Dallimore, S. R. Temperature measurements and thermal gradient estimates on the slope and shelf-edge region of the Beaufort Sea, Canada: Open-File Report - Geological Survey of Canada, Rep. No. 7725, 143 p., illus. incl. tables, 2015.

In situ temperature measurements were conducted at 63 gravity-core stations during the 2013 expedition with the CCGS Sir Wilfrid Laurier in the Canadian Beaufort Sea. Outriggers attached to the outside of the gravity core-barrel were used to mount portable miniature temperature loggers (MTL) for down-core in situ temperature measurements. Several sub-regions were investigated during the expedition including two shelf-slope crossings, three mud volcano-type expulsion features, as well as two canyon sites. The last site visited was at the Gary Knolls, just east of the Mackenzie Trough at water depths of less than 100 m. Overall, temperature data obtained from the MTLs were of high quality at most stations and the data acquisition technique was proven to be robust and easy to adapt in the Arctic. However, depth determination for each logger position remains the largest challenge as no additional pressure sensor was used with the MTLs. Instead, depths were estimated based on the apparent core penetration and the geometry of the outriggers. The most significant result from this work is the discovery of the very large apparent geothermal gradients associated with the two expulsion features (EF) Coke Cap and the mud volcano at 420 m water depth. Temperatures measured within the top 2.5 meter below seafloor suggest geothermal gradients of up to 2.94°C/m (Station 96, 420m EF) and 1.37 °C/m (Station 58, Coke Cap EF). Away from the centre of the EFs, thermal gradients decrease to values of 0.5°C/m for Station 99 at the 420 m EF, and 0.92°C/m at Station 21 at the Coke Cap EF. Temperature data across the slope-shelf transect and the two transects across the canyon heads did not reveal considerable geothermal gradients, but show a water-depth dependent trend in temperature. From deep to shallow water, temperature appear to decrease until the most negative temperature values are found on the shelf itself at water depths of 100 m (-1.2 to -1.4°C). Overall, data from the top 1.0 to 1.5 meter below seafloor are likely affected by seasonal variations in the water column temperature and may not be used to define geothermal gradients. With an optimal full penetration of the core barrel, the deepest temperature data are from 2.3 mbsf, which limits the accuracy of the estimated geothermal gradients as only few data points (2-4) can be used in the calculations.

DOI: 10.4095/296570

2016110848 Bedekar, Vivek (S. S. Papadopulos and Associates); Morway, Eric D.; Langevin, Christian D. and Tonkin, Matthew J. MT3D-USGS; Version 1, A U. S. Geological Survey release of MT3DMS updated with new and expanded transport capabilities for use with MODFLOW: Techniques and Methods (Reston, VA), Rep. No. TM 06-A53, 69 p., illus. incl. 15 tables, 60 ref., 2016. (Prepared in collaboration with S.S. Papadopulos & Associates, Inc.).

MT3D-USGS, a U.S. Geological Survey updated release of the groundwater solute transport code MT3DMS, includes new transport modeling capabilities to accommodate flow terms calculated by MODFLOW packages that were previously unsupported by MT3DMS and to provide greater flexibility in the simulation of solute transport and reactive solute transport. Unsaturated-zone transport and transport within streams and lakes, including solute exchange with connected groundwater, are among the new capabilities included in the MT3D-USGS code. MT3D-USGS also includes the capability to route a solute through dry cells that may occur in the Newton-Raphson formulation of MODFLOW (that is, MODFLOW-NWT). New chemical reaction Package options include the ability to simulate inter-species reactions and parent-daughter chain reactions. A new pump-and-treat recirculation package enables the simulation of dynamic recirculation with or without treatment for combinations of wells that are represented in the flow model, mimicking the above-ground treatment of extracted water. A reformulation of the treatment of transient mass storage improves conservation of mass and yields solutions for better agreement with analytical benchmarks. Several additional features of MT3D-USGS are (1) the separate specification of the partitioning coefficient (K_d) within mobile and immobile domains; (2) the capability to assign prescribed concentrations to the top-most active layer; (3) the change in mass storage owing to the change in water volume now appears as its own budget item in the global mass balance summary; (4) the ability to ignore cross-dispersion terms; (5) the definition of Hydrocarbon Spill-Source Package (HSS) mass loading zones using regular and irregular polygons, in addition to the currently supported circular zones; and (6) the ability to specify an absolute minimum thickness rather than the default percent minimum thickness in dry-cell circumstances. Benchmark problems that implement the new features and packages test the accuracy of new code through comparison to analytical benchmarks, as well as to solutions from other published codes. The input file structure for MT3D-USGS adheres to MT3DMS conventions for backward compatibility: the new capabilities and packages described herein are readily invoked by adding three-letter package name acronyms to the name file or by setting input flags as needed. Memory is managed in MT3D-USGS using FORTRAN modules in order to simplify code development and expansion.

DOI: 10.3133/tm6A53

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