October 2014 Permafrost Alert
The U.S. Permafrost Association, together with the American Geosciences Institute (AGI), is pleased to provide the following Permafrost Monthly Alerts (PMA). The AGI GeoRef service regularly scans the contents of over 3500 journals in 40 languages from the global geosciences literature, comprised of approximately 345 different sources. In addition to journals, special publications such as papers in proceedings and hard-to-find publications are provided. Each PMA represents a listing of the permafrost-related materials added to GeoRef during the previous month. Where available, a direct link to the publication is included, which provides access to the full document if you or your institution have a current online subscription.
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14091115 Wang Genxu (Chinese Academy of Sciences, Institute of Mountain Hazards and Environment, Laboratory of Mountain Surface Processes and Ecological Regulation, Chengdu, China); Mao Tianxu; Chang Juan and Du Jizeng. Impacts of surface soil organic content on the soil thermal dynamics of alpine meadows in permafrost regions; data from field observations: Geoderma, 232-234, p. 414-425, illus. incl. 4 tables, sketch map, 56 ref., November 2014.
The relationship between soil organic matter and soil temperature plays an important role in our understanding of the effect of climate change on the hydrological and carbon cycles in permafrost regions. Several studies have documented that the organic horizon thickness has profound buffering effects on soil temperature for both tundra and boreal forest ecosystems. In the present study, the alpine meadow ecosystem in the middle and low-latitude permafrost region of the Qinghai-Tibet Plateau (QTP) was selected to examine the impacts of surface soil organic matter on the thermal properties of deep soil. Based on the data obtained from more than 23 observation sites, the relationship between soil organic content and soil temperature dynamics in different seasons was determined. The findings indicate a strong positive exponential (in thawing period) and linear (in freezing period) relationship between surface soil organic content (SOC) and soil temperature dynamics in deep soil layers. The higher SOC at the surface soil layer is associated with a lower rate of soil temperature variation and a later onset time for the thaw-freeze transformation. In permafrost regions of the QTP, the greater lapse rate of soil temperature per 100 m of increased elevation resulted in more significant modification of the SOC and soil thermal relationship in alpine meadows than that in tundra and boreal ecosystems. The coupled soil organic matter, soil thermal and water relationships play an important role in the resilience of permafrost during climate changes. Abstract Copyright (2014) Elsevier, B.V.
14089204 Euskirchen, E. S. (University of Alaska, Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Edgar, C. W.; Turetsky, M. R.; Waldrop, M. P. and Harden, J. W. Differential response of carbon fluxes to climate in three peatland ecosystems that vary in the presence and stability of permafrost: Journal of Geophysical Research: Biogeosciences, 119(G8), p. 1576-1595, illus. incl. 3 tables, sketch map, 85 ref., August 2014.
Changes in vegetation and soil properties following permafrost degradation and thermokarst development in peatlands may cause changes in net carbon storage. To better understand these dynamics, we established three sites in Alaska that vary in permafrost regime, including a black spruce peat plateau forest with stable permafrost, an internal collapse scar bog formed as a result of thermokarst, and a rich fen without permafrost. Measurements include year-round eddy covariance estimates of carbon dioxide (CO2), water, and energy fluxes, associated environmental variables, and methane (CH4) fluxes at the collapse scar bog. The ecosystems all acted as net sinks of CO2 in 2011 and 2012, when air temperature and precipitation remained near long-term means. In 2013, under a late snowmelt and late leaf out followed by a hot, dry summer, the permafrost forest and collapse scar bog were sources of CO2. In this same year, CO2 uptake in the fen increased, largely because summer inundation from groundwater inputs suppressed ecosystem respiration. CO2 exchange in the permafrost forest and collapse scar bog was sensitive to warm air temperatures, with 0.5 g C m-2 lost each day when maximum air temperature was very warm (>&eq;29°C). The bog lost 4981 ± 300 mg CH4 m-2 between April and September 2013, indicating that this ecosystem acted as a significant source of both CO2 and CH4 to the atmosphere in 2013. These results suggest that boreal peatland responses to warming and drying, both of which are expected to occur in a changing climate, will depend on permafrost regime. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14089205 Gaglioti, Benjamin V. (University of Alaska, Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Mann, Daniel H.; Jones, Benjamin M.; Pohlman, John W.; Kunz, Michael L. and Wooller, Matthew J. Radiocarbon age-offsets in an arctic lake reveal the long-term response of permafrost carbon to climate change: Journal of Geophysical Research: Biogeosciences, 119(G8), p. 1630-1651, illus. incl. strat. cols., 1 table, geol. sketch maps, 89 ref., August 2014.
Continued warming of the Arctic may cause permafrost to thaw and speed the decomposition of large stores of soil organic carbon (OC), thereby accentuating global warming. However, it is unclear if recent warming has raised the current rates of permafrost OC release to anomalous levels or to what extent soil carbon release is sensitive to climate forcing. Here we use a time series of radiocarbon age-offsets (14C) between the bulk lake sediment and plant macrofossils deposited in an arctic lake as an archive for soil and permafrost OC release over the last 14,500 years. The lake traps and archives OC imported from the watershed and allows us to test whether prior warming events stimulated old carbon release and heightened age-offsets. Today, the age-offset (2 ka; thousand of calibrated years before A.D. 1950) and the depositional rate of ancient OC from the watershed into the lake are relatively low and similar to those during the Younger Dryas cold interval (occurring 12.9-11.7 ka). In contrast, age-offsets were higher (3.0-5.0 ka) when summer air temperatures were warmer than present during the Holocene Thermal Maximum (11.7-9.0 ka) and Bolling-Allerod periods (14.5-12.9 ka). During these warm times, permafrost thaw contributed to ancient OC depositional rates that were ~10 times greater than today. Although permafrost OC was vulnerable to climate warming in the past, we suggest surface soil organic horizons and peat are presently limiting summer thaw and carbon release. As a result, the temperature threshold to trigger widespread permafrost OC release is higher than during previous warming events. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14089180 Lamoureux, Scott F. (Queen's University, Department of Geography, Kingston, ON, Canada); Lafrenière, Melissa J. and Favaro, Elena A. Erosion dynamics following localized permafrost slope disturbances: Geophysical Research Letters, 41(15), p. 5499-5505, illus. incl. 1 table, sketch map, 36 ref., August 16, 2014.
Slope disturbances are key sources of sediment, and the impact and recovery of disturbance on downslope erosion is poorly understood. We measured the erosional response of varying extents of slope disturbance in small permafrost catchments for 5 years following disturbance by active layer detachments. Initial erosion rates increased with the size of disturbance, but subsequent fluxes depended on specific morphological evolution of disturbances. Varying degrees of (i) channel density within the disturbances, (ii) downstream channel connectivity, and (iii) geomorphic evolution of disturbances lead to significant differences in catchment response to disturbance. Our results indicate that new equilibrium states of sediment erosion are achieved within the most disturbed and channelized catchments and contribute to greater heterogeneity of erosion on the landscape. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14091139 Jessen, Soren (University of Copenhagen, Department of Geosciences and Natural Resource Management, Copenhagen, Denmark); Holmslykke, Hanne D.; Rasmussen, Kristine; Richardt, Niels and Holm, Peter E. Hydrology and pore water chemistry in a permafrost wetland, Ilulissat, Greenland: Water Resources Research, 50(6), p. 4760-4774, illus., 40 ref., June 2014.
Hydrological and geochemical processes controlling the pore water chemistry in a permafrost wetland, with loam overlain by sphagnum peat, were investigated. The vertical distributions of dissolved Cl, and of pore water d18O, appeared unrelated to ion freeze-out and isotope ice-water fractionation processes, respectively, dismissing solute freeze-out as a main control on the water chemistry. However, concentrations of major ions, others than Cl, generally increased with depth into the active layer. A conceptual model for water and solute movement in the active layer was derived. The model indicates upward diffusive transport of elements, released in the loam layer by mineral weathering, to the peat layer, in which lateral advective transport dominates. Active layer pore water and water of melted core sections of permafrost were of Ca-Mg-HCO3 type (1:1:4 stoichiometry) and were subsaturated for calcite and dolomite. The results are consistent with an annual cycling of inorganic carbon species, Ca and Mg, via cryogenic carbonate precipitation during fall freeze-up and their redissolution following spring thaw. Similarly, elevated Fe2+ concentrations appear to be related to cryogenic siderite formation. Pore water in the active layer showed high partial pressures of CO2, indicating the feasibility of bubble ebullition as a greenhouse gas emission pathway from permafrost wetlands. Elevated concentrations of geogenic trace elements (Ni, Al, and As) were observed, and the controlling geochemical processes are discussed. The conceptual model for water and solute movement was applied to quantify the contribution of released trace elements to a downstream lake in the permafrost catchment. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14084961 Li, Jianwei (University of Oklahoma, Department of Microbiology and Plant Biology, Norman, OK); Luo, Yiqi; Natali, Susan; Schuur, Edward A. G.; Xia, Jianyang; Kowalczyk, Eva and Wang, Yingping. Modeling permafrost thaw and ecosystem carbon cycle under annual and seasonal warming at an Arctic tundra site in Alaska: Journal of Geophysical Research: Biogeosciences, 119(G6), p. 1129-1146, illus. incl. 3 tables, 105 ref., June 2014. Includes appendices.
Permafrost thaw and its impacts on ecosystem carbon (C) dynamics are critical for predicting global climate change. It remains unclear whether annual and seasonal warming (winter or summer) affect permafrost thaw and ecosystem C balance differently. It is also required to compare the short-term stepwise warming and long-term gradual warming effects. This study validated a land surface model, the Community Atmosphere Biosphere Land Exchange model, at an Alaskan tundra site, and then used it to simulate permafrost thaw and ecosystem C flux under annual warming, winter warming, and summer warming. The simulations were conducted under stepwise air warming (2°C yr-1) during 2007-2011, and gradual air warming (0.04°C yr-1) during 2007-2056. We hypothesized that all warming treatments induced greater permafrost thaw, and larger ecosystem respiration than plant growth thus shifting the ecosystem C sink to C source. Results only partially supported our hypothesis. Climate warming further enhanced C sink under stepwise (6-15%) and gradual (1-8%) warming scenarios as followed by annual warming, winter warming, and summer warming. This is attributed to disproportionally low temperature increase in soil (0.1°C) in comparison to air warming (2°C). In a separate simulation, a greater soil warming (1.5°C under winter warming) led to a net ecosystem C source (i.e., 18 g C m-2 yr-1). This suggests that warming tundra can potentially provide positive feedbacks to global climate change. As a key variable, soil temperature and its dynamics, especially during wintertime, need to be carefully studied under global warming using both modeling and experimental approaches. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14084963 Pastick, Neal J. (Stinger Ghaffarian Technologies, Sioux Falls, SD); Jorgenson, M. Torre; Wylie, Bruce K.; Rose, Joshua R.; Rigge, Matthew and Walvoord, Michelle A. Spatial variability and landscape controls of near-surface permafrost within the Alaskan Yukon River basin: Journal of Geophysical Research: Biogeosciences, 119(G6), p. 1244-1265, illus. incl. 4 tables, sketch maps, 83 ref., June 2014.
The distribution of permafrost is important to understand because of permafrost's influence on high-latitude ecosystem structure and functions. Moreover, near-surface (defined here as within 1 m of the Earth's surface) permafrost is particularly susceptible to a warming climate and is generally poorly mapped at regional scales. Subsequently, our objectives were to (1) develop the first-known binary and probabilistic maps of near-surface permafrost distributions at a 30 m resolution in the Alaskan Yukon River Basin by employing decision tree models, field measurements, and remotely sensed and mapped biophysical data; (2) evaluate the relative contribution of 39 biophysical variables used in the models; and (3) assess the landscape-scale factors controlling spatial variations in permafrost extent. Areas estimated to be present and absent of near-surface permafrost occupy approximately 46% and 45% of the Alaskan Yukon River Basin, respectively; masked areas (e.g., water and developed) account for the remaining 9% of the landscape. Strong predictors of near-surface permafrost include climatic indices, land cover, topography, and Landsat 7 Enhanced Thematic Mapper Plus spectral information. Our quantitative modeling approach enabled us to generate regional near-surface permafrost maps and provide essential information for resource managers and modelers to better understand near-surface permafrost distribution and how it relates to environmental factors and conditions. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14086326 Shiklomanov, Nikolay I. (George Washington University, Department of Geography, Washington, DC); Streletskiy, Dmitry A.; Little, Jonathon D. and Nelson, Frederick E. Isotropic thaw subsidence in undisturbed permafrost landscapes: Geophysical Research Letters, 40(24), p. 6356-6361, illus. incl. sketch map, 30 ref., December 28, 2013.
Observations in undisturbed terrain within some regions of the Arctic reveal limited correlation between increasing air temperature and the thickness of the seasonally thawed layer above ice-rich permafrost. Here we describe landscape-scale, thaw-induced subsidence lacking the topographic contrasts associated with thermokarst terrain. A high-resolution, 11 year record of temperature and vertical movement at the ground surface from contrasting physiographic regions of northern Alaska, obtained with differential global positioning systems technology, indicates that thaw of an ice-rich layer at the top of permafrost has produced decimeter-scale subsidence extending over the entire landscapes. Without specialized observation techniques the subsidence is not apparent to observers at the surface. This "isotropic thaw subsidence" explains the apparent stability of active layer thickness records from some landscapes of northern Alaska, despite warming near-surface air temperatures. Integrated over extensive regions, it may be responsible for thawing large volumes of carbon-rich substrate and could have negative impacts on infrastructure. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
14090782 Morgenstern, A. (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Ulrich, M.; Günther, F.; Roessler, S.; Fedorova, I. V.; Rudaya, N. A.; Wetterich, S.; Boike, J. and Schirrmeister, L. Evolution of thermokarst in East Siberian ice-rich permafrost; a case study: Geomorphology, 201, p. 363-379, illus. incl. 3 tables, sketch maps, 48 ref., November 1, 2013. Includes appendices.
Thermokarst lakes and basins are major components of ice-rich permafrost landscapes in East Siberian coastal lowlands and are regarded as indicators of regional climatic changes. We investigate the temporal and spatial dynamics of a 7.5 km2, partly drained thermokarst basin (alas) using field investigations, remote sensing, Geographic Information Systems (GIS), and sediment analyses. The evolution of the thermokarst basin proceeded in two phases. The first phase started at the Pleistocene/Holocene transition (13 to 12 ka BP) with the initiation of a primary thermokarst lake on the Ice Complex surface. The lake expanded and persisted throughout the early Holocene before it drained abruptly about 5.7 ka BP, thereby creating a >20m deep alas with residual lakes. The second phase (5.7 ka BP to present) is characterized by alternating stages of lower and higher thermokarst intensity within the alas that were mainly controlled by local hydrological and relief conditions and accompanied by permafrost aggradation and degradation. It included diverse concurrent processes like lake expansion and stepwise drainage, polygonal ice-wedge growth, and the formation of drainage channels and a pingo, which occurred in different parts of the alas. This more dynamic thermokarst evolution resulted in a complex modern thermokarst landscape. However, on the regional scale, the changes during the second evolutionary phase after drainage of the initial thermokarst lakes were less intense than the early Holocene extensive thermokarst development in East Siberian coastal lowlands as a result of a significant regional change to warmer and wetter climate conditions. Abstract Copyright (2013) Elsevier, B.V.
14086593 Matthies, Romy (Newcastle University, School of Civil Engineering and Geosciences, Newcastle upon Tyne, United Kingdom); Sinclair, Sean A and Blowes, David W. The zinc stable isotope signature of waste rock drainage in the Canadian permafrost region: Applied Geochemistry, 48, p. 53-57, illus. incl. sketch map, 38 ref., September 2014. Includes appendices.
Leachate from a well-instrumented experimental-scale waste-rock pile (test pile) at the Diavik Diamond mine, Northwest Territories, was monitored. The well-characterized waste rock consists of granite, pegmatitic granite and biotite schist with an average total sulfur and carbonate carbon concentration of 0.053 and 0.027 wt.%, respectively. The leachate emerging from the southern basal drain of the waste rock pile has been monitored since 2007. The zinc stable isotope footprint was characterized alongside standard monitoring parameters during two field seasons, May to November 2011 and 2012. The pH ranged between 4.3 and 6.8 and carbonate alkalinity was low or undetectable (<35 mg L-1 CaCO3). The pH was governed by the oxidation of sulfide minerals and the dissolution of primary carbonate minerals and secondary Al and Fe oxyhydroxysulfates and hydroxides. Dissolved Al and Fe concentrations averaged 6.78 mg L-1 and 175 mg L-1, respectively. The main processes controlling Zn concentrations in the range of 0.4 and 4.7 mg L-1 (average = 2.2 mg L-1) were the oxidative dissolution of sphalerite (ZnS) and the attenuation by secondary Fe and Al hydroxides. Zinc isotopes were fractionated mass dependently. Zinc isotope ratios, ranging between -0.16 and +0.18 ppm (average = +0.05 ppm, n = 43) were consistent with values reported for sphalerite from other deposits. The deviations in isotope ratios (D = 0.36 ppm) were significant in comparison to analytical uncertainties (0.06 ppm). Zinc isotope ratios and concentrations were largely uncorrelated, suggesting that the processes affecting Zn mobility had little or no impact on the Zn isotope signature. These data suggest that the Zn isotope ratios of the waste-rock leachate may be used as a fingerprint to track anthropogenic, mine-derived Zn sources in an environment under fluctuating pH, temperature and ionic strength. Abstract Copyright (2014) Elsevier, B.V.
14086365 Matthiesen, H. (National Museum of Denmark, Conservation Department, Copenhagen, Denmark); Jensen, J. B.; Gregory, D.; Hollesen, J. and Elberling, B. Degradation of archaeological wood under freezing and thawing conditions; effects of permafrost and climate change: Archaeometry, 56(3), p. 479-495, illus. incl. 4 tables, sketch map, 34 ref., June 2014.
The degradation of archaeological wood at freezing and thawing temperatures is studied at the site of Qajaa in West Greenland through a combination of environmental monitoring, measurement of oxygen consumption and microscopy of wood samples. Permanently frozen wood is still very well preserved after 2-4000 years, while wood samples that thaw every summer show attack by soft rot and an average density loss of 0.1 g cm-3 (corresponding to 25% of the dry mass) over the past 27 years. Future increases in temperature may increase the decay rate significantly (Q10 = 4.2 at 0-10°C) but the effects on site depend on local hydrology. Abstract Copyright (2013), University of Oxford.
14091377 Oliva, Marc (University of Lisbon, Institute of Geography and Spatial Planning, Lisbon, Portugal); Gómez Ortiz, Antonio; Salvador, Ferran; Salvà, Montserrat; Pereira, Paulo and Geraldes, Miguel. Long-term soil temperature dynamics in the Sierra Nevada, Spain: Geoderma, 235-236, p. 170-181, illus. incl. chart, 3 tables, sketch map, 53 ref., December 2014.
Soil temperatures play a key role on the dynamics of geomorphological processes in periglacial environments. However, little is known about soil thermal dynamics in periglacial environments of semiarid mid-latitude mountains, where seasonal frost is dominant. From September 2006 to August 2012 we have monitored soil temperatures at different depths (2, 10, 20, 50 and 100 cm) in a solifluction landform located at 3005 m.a.s.l. in the summit area of the Sierra Nevada (South Spain). Mean annual temperatures in the first meter of the soil ranged from 3.6 to 3.9 °C while the mean annual air temperature at the nearby Veleta peak was 0.08 °C. Therefore, these data point out the inexistence of widespread permafrost conditions today in this massif. Seasonal frost controls the geomorphodynamics even in the highest lands. Climate conditions have shown a large interannual variability, as it is characteristic in a high mountainous Mediterranean environment. These variations are reflected in the patterns of soil thermal dynamics. The depth and duration of the frozen layer are strongly conditioned by the thickness of the snow cover. The date of the first significant snowfalls conditioned the beginning and rhythm of freezing of the soil. Wet years resulted in a thick snow cover which insulated the ground from external climate oscillations and favored a shallow frost layer (2008-2009, 2009-2010 and 2010-2011). On the other hand, years with low precipitations promoted deeper freezing of the soil down to 60-70 cm extending until late May or early June (2006-2007, 2007-2008 and 2011-2012). When snow melted a high increase of temperatures of 10-12 °C in few weeks was recorded at all depths. At this time of the year, periglacial activity is enhanced due to higher water availability and the existence of freeze-thaw cycles. These were recorded mostly in spring and autumn in the first 50 cm depth of the soil, ranging from 9.8 days (at 2 cm) to 3.7 days (at 50 cm). However, the inactivity of solifluction landforms suggests that the combination of present-day soil temperatures together with moisture conditions is not favorable to promote solifluction activity in the periglacial belt of the Sierra Nevada. Future climate scenarios point to a temperature increase and precipitation decrease in the area, which would entail deeper but shorter frozen soil layers. These conditions would not be favorable for active periglacial slope processes in the Sierra Nevada. Abstract Copyright (2014) Elsevier, B.V.
14088840 Allred, Kory (Northern Illinois University, Department of Geography, DeKalb, IL); Luo, Wei; Konen, Mike and Curry, B. Brandon. Morphometric analysis of ice-walled lake plains in northern Illinois; implications of lake elongation by wind-induced dual cycle currents: Geomorphology, 220, p. 50-57, illus. incl. 3 tables, sketch map, 39 ref., September 1, 2014. Includes appendices.
Ice-walled lake plains (IWLPs) are rounded, flat-topped mounds that formed in stagnant ice environments along the margins of the Laurentide Ice Sheet. We conducted detailed morphometric and statistical analyses of the shape, size, and orientation of more than 400 IWLPs identified from aerial photos aided with LiDAR data in DeKalb County, Illinois, USA. Lake elongation theories include extraterrestrial impact (e.g. the Carolina Bays), ice flow dynamics and crevasses, and wind induced currents that preferentially erode the shorelines perpendicular to the dominant wind direction. The results indicate that elliptical IWLPs with a perimeter greater than 3050 m have preferred orientations roughly normal to the paleo-wind direction as indicated by contemporaneous parabolic dunes located 50 km to the west. The orientations of the IWLPs with a perimeter less than 1220 m are scattered and show no apparent trend. The IWLP orientation is not related to ice flow dynamics or glacial crevasses because no statistically significant relationship exists with regard to the ice flow as proxied by the moraine direction. The orientation of large IWLPs in DeKalb County are consistent with wind-induced lake elongation observed in modern permafrost thaw lakes, suggesting that the prevailing wind also played an important role in controlling the orientation of IWLPs during the last glacial period and led to the preferred orientation we see today. Abstract Copyright (2014) Elsevier, B.V.
14089616 Kokelj, S. V. (Government of the Northwest Territories, Northwest Territories Geoscience Office, Yellowknife, NT, Canada); Lantz, T. C.; Wolfe, S. A.; Kanigan, J. C.; Morse, P. D.; Coutts, R.; Molina-Giraldo, N. and Burn, C. R. Distribution and activity of ice wedges across the forest-tundra transition, western Arctic Canada: Journal of Geophysical Research: Earth Surface, 119(F9), p. 2032-2047, illus. incl. 3 tables, sketch maps, 57 ref., September 2014.
Remote sensing, regional ground temperature and ground ice observations, and numerical simulation were used to investigate the size, distribution, and activity of ice wedges in fine-grained mineral and organic soils across the forest-tundra transition in uplands east of the Mackenzie Delta. In the northernmost dwarf-shrub tundra, ice wedge polygons cover up to 40% of the ground surface, with the wedges commonly exceeding 3 m in width. The largest ice wedges are in peatlands where thermal contraction cracking occurs more frequently than in nearby hummocky terrain with fine-grained soils. There are fewer ice wedges, rarely exceeding 2 m in width, in uplands to the south and none have been found in mineral soils of the tall-shrub tundra, although active ice wedges are found there throughout peatlands. In the spruce forest zone, small, relict ice wedges are restricted to peatlands. At tundra sites, winter temperatures at the top of permafrost are lower in organic than mineral soils because of the shallow permafrost table, occurrence of phase change at 0°C, and the relatively high thermal conductivity of icy peat. Due to these factors and the high coefficient of thermal contraction of frozen saturated peat, ice wedge cracking and growth is more common in peatlands than in mineral soil. However, the high latent heat content of saturated organic active layer soils may inhibit freezeback, particularly where thick snow accumulates, making the permafrost and the ice wedges in spruce forest polygonal peatlands susceptible to degradation following alteration of drainage or climate warming. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14089206 Peterse, Francien (Eidgenössische Technische Hochschule Zürich, Geological Institute, Zurich, Switzerland); Vonk, Jorien E.; Holmes, R. Max; Giosan, Liviu; Zimov, Nikita and Eglinton, Timothy I. Branched glycerol dialkyl glycerol tetraethers in Arctic lake sediments; sources and implications for paleothermometry at high latitudes: Journal of Geophysical Research: Biogeosciences, 119(G8), p. 1738-1754, illus. incl. 2 tables, sketch maps, 63 ref., August 2014.
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are analyzed in different lakes of the Mackenzie (Canadian Arctic) and Kolyma (Siberian Arctic) River basins to evaluate their sources and the implications for brGDGT-based paleothermometry in high-latitude lakes. The comparison of brGDGT distributions and concentrations in the lakes with those in river suspended particulate matter, riverbank sediments, and permafrost material indicates that brGDGTs in Arctic lake sediments have mixed sources. In contrast to global observations, distributional offsets between brGDGTs in Arctic lakes and elsewhere in the catchment are minor, likely due to the extreme seasonality and short window of biological production at high latitudes. Consequently, both soil- and lake-calibrated brGDGT-based temperature proxies return sensible temperature estimates, even though the mean air temperature (MAT) in the Arctic is below the calibration range. The original soil-calibrated MBT-CBT (methylation of branched tetraethers-cyclisation of branched tetraethers) proxy generates MATs similar to those in the studied river basins, whereas using the recently revised MBT'-CBT calibration overestimates MAT. The application of the two global lake calibrations, generating summer air temperatures (SAT) and MAT, respectively, illustrates the influence of seasonality on the production of brGDGTs in lakes, as the latter overestimates actual MAT, whereas the SAT-based lake calibration accounts for this influence and consequently returns more accurate temperatures. Our results in principle support the application of brGDGT-based temperature proxies in high-latitude lakes in order to obtain long-term paleotemperature records for the Arctic, although the calibration and associated transfer function have to be selected with care. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14086483 Gleeson, Tom (McGill University, Department of Civil Engineering, Montreal, QC, Canada); Moosdorf, Nils; Hartmann, Jens and Beek, L. P. H. A glimpse beneath Earth's surface; GLobal HYdrogeology MaPS (GLHYMPS) of permeability and porosity: Geophysical Research Letters, 41(11), p. 3891-3898, illus. incl. 1 table, sketch maps, 40 ref., June 16, 2014.
The lack of robust, spatially distributed subsurface data is the key obstacle limiting the implementation of complex and realistic groundwater dynamics into global land surface, hydrologic, and climate models. We map and analyze permeability and porosity globally and at high resolution for the first time. The new permeability and porosity maps are based on a recently completed high-resolution global lithology map that differentiates fine and coarse-grained sediments and sedimentary rocks, which is important since these have different permeabilities. The average polygon size in the new map is ~100 km2, which is a more than hundredfold increase in resolution compared to the previous map which has an average polygon size of ~14,000 km2. We also significantly improve the representation in regions of weathered tropical soils and permafrost. The spatially distributed mean global permeability ~10-15 m2 with permafrost or ~10-14 m2 without permafrost. The spatially distributed mean porosity of the globe is 14%. The maps will enable further integration of groundwater dynamics into land surface, hydrologic, and climate models. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14085180 Mishra, Umakant (Argonne National Laboratory, Environmental Science Division, Argonne, IL) and Riley, William J. Active-layer thickness across Alaska; comparing observation-based estimates with CMIP5 earth system model predictions: Soil Science Society of America Journal, 78(3), p. 894-902, illus. incl. 4 tables, sketch map, 55 ref., June 2014.
Predicted active-layer (AL) thicknesses of permafrost-affected soils influence earth system model predictions of C-climate feedbacks; yet, only a few observation-based studies have estimated AL thicknesses across large regions and at the spatial scale at which they vary. We used spatially referenced soil profile description data (n = 153) and environmental variables (topography, climate, and land cover) in a geographically weighted regression approach to predict the spatial variability of AL thickness across Alaska at a 60-m spatial resolution. The predicted AL thickness across Alaska ranged from 0.14 to 0.93 m, with a spatial average of 0.46 m and a coefficient of variation of 30%. The average prediction error and ratio of performance to deviation were 0.11 m and 1.8, respectively. Our study showed mean annual surface air temperature, land cover type, and slope gradient were primary controllers of AL thickness spatial variability. We compared our estimates with Coupled Model Intercomparison Project Phase 5 (CMIP5) earth system model predictions; those predictions showed large interquartile ranges in predicted AL thicknesses (0.35-4.4 m) indicating substantial overestimate of current AL thickness in Alaska, which might result in higher positive permafrost C feedback under future warming scenarios. The CMIP5 predictions of AL thicknesses spatial heterogeneity were unrealistic when compared with observations, and prediction errors were several times larger in comparison to errors from our observation-based approach. The coefficient of variability of AL thickness was substantially lower in CMIP5 predictions compared to our estimates when gridded at similar spatial resolutions. These results indicate the need for better process representations and representation of natural spatial heterogeneity due to local environment (topography, vegetation, and soil properties) in earth system models to generate a realistic variation of regional scale AL thickness, which could reduce the existing uncertainty in predicting permafrost C-climate feedbacks.
14085914 Song Yongchen (Dalian University of Technology, Key Laboratory of Ocean Energy Utilization and Energy Conversion of Ministry of Education, Dalian, China); Xue Kaihua; Zhao Jiafei; Lam, Weihaur; Cheng Chuanxiao; Yang Mingjun; Zhang Yi; Wang Dayong; Liu Weiguo and Liu Yu. In situ observation of hydrate growth habit in porous media using magnetic resonance imaging: Europhysics Letters, 101(3), Abstract 36004, February 2013. Based on Publisher-supplied data.
To investigate the growth law and microstructure of hydrates in sediments, the growth process of the tetrahydrofuran (THF) hydrate is observed in site using magnetic resonance imaging (MRI). The hydrate formation starts preferentially from the grain surface and then grows towards the liquid phase filling up the pore. In the final stage, the hydrate cements and stiffens the sediment. In this study, the cementing microstructure of the THF hydrate was directly observed in porous media. The extension of the observed behavior to methane hydrates gives implications for understanding their role in the seismic exploration and the stability of permafrost and seafloor. Copyright Copyright EPLA, 2013
14086673 Lysa, Astrid (Geological Survey of Norway, Trondheim, Norway); Larsen, Eiliv; Buylaert, Jan-Pieter; Fredin, Ola; Jensen, Maria A.; Kuznetsov, Denis; Murray, Andrew S.; Subetto, Dmitry A. and van Welden, Aurelien. Late Pleistocene stratigraphy and sedimentary environments of the Severnaya Dvina-Vychegda region in northwestern Russia: Boreas, 43(4), p. 759-779, illus. incl. sect., strat. cols., 1 table, sketch map, 66 ref., October 2014.
The Late Pleistocene stratigraphy from the Severnaya Dvina-Vychegda region of northwestern Russia is revised based on investigations of new localities, revisiting earlier localities, introduction of about 110 new OSL dates and burial depth corrections of earlier published OSL dates, in addition to six new radiocarbon dates. Most of the OSL samples studied here are from fluvial and subaquaeous sediments, which we found to be well bleached. Six chronostratigraphical units and their sedimentary environment are described, with the oldest unit consisting of pre-Eemian glacial beds. For the first time, Early Weichselian sediments are documented from the region and a fluvial environment with some vegetation and permafrost conditions is suggested to have persisted from the end of the Eemian until at least about 92 ka ago. The period in which a Middle Weichselian White Sea Lake could have existed is constrained to 67-62 ka, but as the lake level never reached the thresholds of the drainage basin, the lake probably existed only for a short interval within this time-span. Blocking and reversal of fluvial drainage started again around 21-20 ka ago when the Fennoscandian Ice Sheet advanced into the area, reaching its maximum 17-15 ka ago. At that time, an ice-dammed lake reached its maximum water level, which was around 135 m above present sea level. Drainage of the lake started shortly after 15 ka ago, and the lake was emptied within 700 years. Severe periglacial conditions, with permafrost and aeolian activity, prevailed in the area until about 10.7 ka. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14084962 Sobek, S. (Swiss Federal Institute of Aquatic Science and Technology, Kastanienbaum, Switzerland); Anderson, N. J.; Bernasconi, S. M. and Del Sontro, T. Low organic carbon burial efficiency in arctic lake sediments: Journal of Geophysical Research: Biogeosciences, 119(G6), p. 1231-1243, illus. incl. 3 tables, 50 ref., June 2014.
Many arctic landscapes are rich in lakes that store large quantities of organic carbon in their sediments. While there are indications of highly efficient carbon burial in high-latitude lakes, the magnitude and efficiency of carbon burial in arctic lake sediments, and thus their potential as carbon sinks, has not been studied systematically. We therefore investigated the burial efficiency of organic carbon (OC), defined as the ratio between OC burial and OC deposition onto the sediment, in seven contrasting lakes in western Greenland representing different arctic lake types. We found that the OC burial efficiency was generally low in spite of the differences between lake types (mean 22%, range 11-32%), and comparable to lakes in other climates with similar organic matter source and oxygen exposure time. Accordingly, post-depositional degradation of sediment organic matter was evident in the organic matter C:N ratio, d13C and d15N values during the initial ~50 years after deposition, and proceeds simultaneously with long-term changes in, e.g., productivity and climate. Pore water profiles of dissolved methane suggest that post-depositional degradation may continue for several centuries in these lakes, at very low rates. Our results demonstrate that the regulation of the sediment OC burial efficiency is no different in arctic lakes than in other lakes, implying that the efficiency of the carbon sink in lake sediments depends similarly on environmental conditions irrespective of latitude. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
14085368 Kojima, Yuki (Iowa State University, Department of Agronomy, Ames, IA); Heitman, Joshua L.; Flerchinger, Gerald N.; Ren Tusheng; Ewing, Robert P. and Horton, Robert. Field test and sensitivity analysis of a sensible heat balance method to determine soil ice contents: Vadose Zone Journal, 13(9), 10 p., illus. incl. 2 tables, 52 ref., September 2014.
Soil ice content impacts winter vadose zone hydrology. It may be possible to estimate changes in soil ice content with a sensible heat balance (SHB) method, using measurements from heat pulse (HP) sensors. Feasibility of the SHB method is unknown because of difficulties in measuring soil thermal properties in partially frozen soils. The objectives of this study were (i) to examine the SHB method for determining in situ ice content, and (ii) to evaluate the required accuracy of HP sensors for use in the SHB method. Heat pulse sensors were installed in a bare field to measure soil temperatures and thermal properties during freezing and thawing events. In situ soil ice contents were determined at 60-min intervals with SHB theory. Sensitivity of the SHB method to temperature, heat capacity, thermal conductivity, and time step size was analyzed based on numerically produced soil freezing and thawing events. The in situ ice contents determined with the SHB method were sometimes unrealistically large or even negative. Thermal conductivity accuracy and time step size were the key factors contributing to SHB errors, while temperature and heat capacity accuracy had less influence. Ice content estimated with a 15-min SHB time step was more accurate than that estimated with a 60-min time step. Sensitivity analysis indicated that measurement errors in soil temperature and thermal conductivity should be less than ±0.05°C and ±20%, respectively, but the error in the soil heat capacity could vary by ±50%. Thus, improving the accuracy of thermal conductivity measurements and using short time steps are required to accurately estimate soil ice contents with the SHB method.
14091077 Telfer, M. W. (Plymouth University, School of Geography, Earth and Environmental Sciences, Plymouth, United Kingdom); Mills, S. C. and Mather, A. E. Extensive Quaternary aeolian deposits in the Drakensberg foothills, Rooiberge, South Africa: Geomorphology, 219, p. 161-175, illus. incl. sketch maps, 95 ref., August 15, 2014.
Deposits of aeolian sand are known to have accumulated in periglacial environments during the cold phases of the late Quaternary. In many instances, however, they form low-relief topographic units which may not be readily identified without detailed field survey. This study aims to use a multidisciplinary approach, combining remotely sensed data analysis and field survey, to investigate the extent and palaeoenvironmental significance of sand ramps in the Drakensberg/Rooiberge foothills of South Africa. Analysis of Google EarthTM imagery has demonstrated that gully systems are a common component of the landscape, and heterogeneously distributed across the landscape. Field investigation confirmed the hypothesis that the gullies are mainly eroding into sand ramps of fine sands and very coarse silts which mantle many of the lower hillslopes of the region. These sand units include palaeosols and occasional gravel lags, but are otherwise remarkable for their homogenous composition, cross-bedding and the complete absence of clasts. Much of the sediment is thus interpreted as aeolian in origin. The deposits are sufficiently similar in many respects to the Masotcheni Formation, a late Quaternary colluvium which outcrops abundantly in the Drakensberg, to propose an assignation to this unit. However, an aeolian component in the Masotcheni has not previously been described. The distribution of aeolian accumulation in the region is consistent with southward transport during late Quaternary cold phases from a source on the Highveld to the north of the study area. The low relief and complex fluvial network in this region would concentrate sediment eroded from the Drakensberg/Rooiberge, which would subsequently be available for deflation when the balance between fluvial flow regime, seasonally frozen ground and north-westerly trade winds were optimal for aeolian entrainment. Deposition is primarily topographically controlled, and is in places sufficiently extensive that it may be better described as a discontinuous coversand. This study suggests that aeolian deposits may be overlooked in other environments subject to past periglacial landscape development, and develops a potential methodology by which this problem may be overcome. Abstract Copyright (2014) Elsevier, B.V.
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14085142 Connon, Ryan F. (Wilfrid Laurier University, Centre for Cold Regions and Water Science, Waterloo, ON, Canada); Quinton, William L.; Craig, James R. and Hayashi, Masaki. Changing hydrologic connectivity due to permafrost thaw in the lower Liard River valley, NWT, Canada: in Canadian Geophysical Union special issue 2014 (Carey, Sean, editor; et al.), Hydrological Processes, 28(14), p. 4163-4178, illus. incl. 6 tables, sketch map, 36 ref., July 1, 2014. Meeting: 2013 annual meeting of the Canadian Geophysical Union, May 27-30, 2013, Saskatoon, SK, Canada.
Flows from river basins in northwestern Canada have been rising in the last two decades as a result of climate warming. In the wetland-dominated basins that characterise the southern margin of permafrost, permafrost thaw and disappearance, and resulting land-cover change, is occurring at an unprecedented rate. The impact of this thaw on runoff generation in headwater basins is poorly understood. Permafrost thaw has the potential to fundamentally alter the cycling and storage of moisture inputs in this region by altering the type and relative proportions of the major land-cover types, such as peat plateaus, channel fens and flat bogs. This paper examines streamflow changes in the four Water Survey of Canada gauged river basins (152-2050 km2) in the lower Liard River valley, Northwest Territories, Canada, a region where permafrost thaw has produced widespread loss of forest and concomitant expansion of permafrost-free wetlands. Annual runoff in the lower Liard Valley increased by between 112 and 160 mm over the period of 1996-2012. The Mann-Kendall non-parametric statistical test and the Kendall-Theil robust line were used to ascertain changes in streamflow. Historical aerial photographs from 1977 and high-resolution satellite imagery (WorldView 2) from 2010 were used to measure the rate and pattern of permafrost thaw in a representative 6 km2 area of Scotty Creek. Permafrost thaw-induced land-cover change is both increasing the adjacency between runoff producing and transmitting land cover types and transforming certain land covers that store water into ones that produce runoff. This land-cover change was found to be the single most important factor (37-61 mm) contributing to the observed increase in river discharge. Other contributing factors include increases in plateau runoff contributing areas (20-32 mm), increases in annual effective precipitation depth (18-30 mm), contribution of water from the melt of ice within permafrost (9 mm) and increases in baseflow (0.9-6.8 mm). Although runoff has significantly (p < 0.05) increased in all four basins, the largest increases are in basins with a relatively high cover of flat bogs. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14084451 Briggs, M. A. (U.S. Geological Survey, Branch of Geophysics, Storrs, CT); Walvoord, M. A.; McKenzie, J. M.; Voss, C. I.; Day-Lewis, F. D. and Lane, J. W. Shrinking Arctic lakes are forming new local permafrost, but for how long? [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0547, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Using multiple physical, thermal, and geophysical methods over two summer seasons we have observed patchy permafrost aggradation within the recently receded margin of Twelvemile Lake, in the Yukon Flats of interior Alaska. However, recent rapid recession of Twelvemile Lake over tens of years is presumed to be linked to climate warming. The counterintuitive process of newly forming permafrost in a warming climate may be a result of ecological succession: discrete bands of brushy vegetation develop on the dried lakebed, reducing local summer soil temperatures and infiltration, and favoring the persistence of ground ice through multiple annual cycles. Using a modified version of the USGS code SUTRA to account for variably saturated flow and freeze/thaw dynamics, a suite of 1-D simulations were constructed to assess the relation of permafrost aggradation at Twelvemile Lake to ecosystem-driven effects. The changes simulated included reductions in recharge during the summer (plant transpiration/interception) and peak surface soil temperatures (albedo/shading). Simulations indicate that the system is strongly responsive to reductions in peak surface soil temperature. Permafrost aggradation began after 2 years with only a 1° C reduction; after 75 years saturated and unsaturated frozen materials on the order of 7 m thick were simulated when soil peak temperatures were reduced by 2° C. The absence of summer recharge alone did not support permafrost aggradation in the simulations, but did reduce time to permafrost equilibrium for the moderate 1° C reduction in peak temperatures while having less of an effect for the 2° C reduction model. Finally, when a predicted climate warming trend of 3° C/100 yr is imposed on the simulation of strongest cooling and infiltration reduction, the aggraded permafrost thaws completely after approximately 70 yr, and the seasonal freeze/thaw layer shallows thereafter. Therefore, local permafrost aggradation in response to lake recession within the discontinuous permafrost zone may affect local processes in the short term, but is likely to be overtaken by further warming within the next century.
14084453 Endalamaw, A. M. (International Arctic Research Center, Fairbanks, AK); Bolton, W. R.; Young, J. M.; Morton, D. and Hinzman, L. D. Toward improved parameterization of a meso-scale hydrologic model in a discontinuous permafrost, boreal forest ecosystem [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0549, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The sub-arctic environment can be characterized as being located in the zone of discontinuous permafrost. Although the distribution of permafrost is site specific, it dominates many of the hydrologic and ecologic responses and functions including vegetation distribution, stream flow, soil moisture, and storage processes. In this region, the boundaries that separate the major ecosystem types (deciduous dominated and coniferous dominated ecosystems) as well as permafrost (permafrost verses non-permafrost) occur over very short spatial scales. One of the goals of this research project is to improve parameterizations of meso-scale hydrologic models in this environment. Using the Caribou-Poker Creeks Research Watershed (CPCRW) as the test area, simulations of the headwater catchments of varying permafrost and vegetation distributions were performed. CPCRW, located approximately 50 km northeast of Fairbanks, Alaska, is located within the zone of discontinuous permafrost and the boreal forest ecosystem. The Variable Infiltration Capacity (VIC) model was selected as the hydrologic model. In CPCRW, permafrost and coniferous vegetation is generally found on north facing slopes and valley bottoms. Permafrost free soils and deciduous vegetation is generally found on south facing slopes. In this study, hydrologic simulations using fine scale vegetation and soil parameterizations - based upon slope and aspect analysis at a 50 meter resolution - were conducted. Simulations were also conducted using downscaled vegetation from the Scenarios Network for Alaska and Arctic Planning (SNAP) (1 km resolution) and soil data sets from the Food and Agriculture Organization (FAO) (approximately 9 km resolution). Preliminary simulation results show that soil and vegetation parameterizations based upon fine scale slope/aspect analysis increases the R2 values (0.5 to 0.65 in the high permafrost (53%) basin; 0.43 to 0.56 in the low permafrost (2%) basin) relative to parameterization based on coarse scale data. These results suggest that using fine resolution parameterizations can be used to improve meso-scale hydrological modeling in this region.
14084427 Fortier, R. (Laval University, Geology and Geological Engineering, Quebec, QC, Canada); Lemieux, J.; Molson, J. W.; Therrien, R.; Ouellet, M. and Bart, J. The Immatsiak network of groundwater wells in a small catchment basin in the discontinuous permafrost zone of northern Quebec, Canada; a unique opportunity for monitoring the impacts of climate change on groundwater [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
During a summer drilling campaign in 2012, a network of nine groundwater monitoring wells was installed in a small catchment basin in a zone of discontinuous permafrost near the Inuit community of Umiujaq in Northern Quebec, Canada. This network, named Immatsiak, is part of a provincial network of groundwater monitoring wells to monitor the impacts of climate change on groundwater resources. It provides a unique opportunity to study cold region groundwater dynamics in permafrost environments and to assess the impacts of permafrost degradation on groundwater quality and availability as a potential source of drinking water. Using the borehole logs from the drilling campaign and other information from previous investigations, an interpretative cryo-hydrogeological cross-section of the catchment basin was produced which identified the Quaternary deposit thickness and extent, the depth to bedrock, the location of permafrost, one superficial aquifer located in a sand deposit, and another deep aquifer in fluvio-glacial sediments and till. In the summer of 2013, data were recovered from water level and barometric loggers which were installed in the wells in August 2012. Although the wells were drilled in unfrozen zones, the groundwater temperature is very low, near 0.4 °C, with an annual variability of a few tenths of a degree Celsius at a depth of 35 m. The hydraulic head in the wells varied as much as 6 m over the last year. Pumping tests performed in the wells showed a very high hydraulic conductivity of the deep aquifer. Groundwater in the wells and surface water in small thermokarst lakes and at the catchment outlet were sampled for geochemical analysis (inorganic parameters, stable isotopes of oxygen (d18O) and hydrogen (d2H), and radioactive isotopes of carbon (d14C), hydrogen (tritium d3H) and helium (d3He)) to assess groundwater quality and origin. Preliminary results show that the signature of melt water from permafrost thawing is observed in the geochemistry of groundwater and surface water at the catchment outlet. Following synthesis of the available information, including a cryo-hydrogeophysical investigation in progress, a three-dimensional hydrogeological conceptual and numerical model of the catchment basin will be developed. According to different scenarios of climate change, the potential of using groundwater as a sustainable resource in northern regions will be assessed by simulating the present and future impacts of climate change on this groundwater system.
14088763 Grebenets, V. I. (Lomonosov Mosocw State University, Moscow, Russian Federation) and Streletskiy, D. A. Human-modified permafrost complexes in urbanized areas of the Russian North [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0871, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Economic development in permafrost regions is accompanied by modification of natural geocryological conditions. Drastic landscape transformations in urbanized areas on permafrost are characterized by changes of heat and moisture exchange in permafrost - atmosphere system, and by engineering and technogenic influence upon the frozen ground, leading to alteration of its physical, thermal and mechanical properties. In northern cities this leads to overall increase of ground temperature relative to undisturbed areas and intensification of hazardous cryogenic processes in areas under engineering development, which together leads to reduction in stability of geotechnical environment. For example, deformations of structures in Norilsk district, Northern Siberia, in the last 15 years, became much more abundant than those revealed throughout the previous 50 years. About 250 large buildings in the local towns were deformed considerably due to deterioration of geocryological conditions, about 100 structures were functioning in emergency state, and almost 50 nine- and five-storey houses, built in the 1960-80s, have been recently disassembled. Increase in accident risk for various facilities (water and oil pipelines, industrial enterprises, etc.) enhances the technogenic pressure on permafrost, leading to the new milestone of changes in permafrost characteristics, i.e. to creation of "another reality" of geocryological conditions. Social and natural factors dictate clustered spatial pattern of industrial development in permafrost regions. Cryogenic processes within the urban areas on permafrost are seldom similar with those under the natural conditions as intensity, duration and extent of the processes changes under technogenic impacts. Moreover, new cryogenic processes and phenomena may occur, which have not been typical for a given region. This makes mapping and characterization of these processes difficult task. Peculiar natural-technogenic geocryological complexes (NTGC) are formed in the urban territories, which are characterized by modified permafrost characteristics, by the new set of cryogenic processes, and by modified temperature trends. NTGC classification depends on initial natural settings and on type, intensity and duration of technogenic pressure. For instance, field reconnaissance of permafrost and geological conditions resulted in characterization of 17 NTGC types in Norilsk industrial area, 11 types in Yamburg Gas Condensate Field, Tazovsky Peninsula, and 32 types along gas and oil pipelines in the north of Western Siberia. Particular interest presents the dynamics of NTGC depending on the scale of urban system, on the set of its elements and on duration of technogenic impacts on permafrost. Important aspect is assessment of climate change impacts on structures and environment in various areas on permafrost.
14084454 Jones, C. (University of Alaska, Fairbanks, Institute of Arctic Research Center, Fairbanks, AK); Kielland, K. and Hinzman, L. D. Increased groundwater upwelling from changes in permafrost as a control on river ice thickness [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0550, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Tanana River flows through interior Alaska, a region characterized by discontinuous permafrost. Studies link degrading permafrost to increased winter river discharge due to increasing groundwater input. In winter, interior Alaskan rivers are exclusively fed by groundwater, which serves as an external source of heat. In fact, some portions of rivers fed by groundwater maintain thin ice throughout the winter, or remain altogether ice-free, despite very cold air temperatures. These ice conditions represent a significant danger to winter travellers who use rivers for wintertime travel, particularly in this largely roadless area. We developed a deterministic model to explore how fluctuations in groundwater discharge control ice thickness on the Tanana River. The model allows us to examine how local changes in groundwater characteristics affect ice dynamics by addressing two questions: 1) What are the dominant factors controlling seasonal ice dynamics on the Tanana River? 2) What are the rates of change in ice thickness resulting from observed and projected changes in these factors? Ice melt is amplified by increased hydraulic gradients, increased groundwater upwelling, increased air temperature, increased groundwater temperature, or increased snow depth. A warming climate in regions with discontinuous permafrost is expected to increase groundwater input into rivers, decrease the temperature gradient between the atmosphere and the ice/water interface, and increase snow depths. All these changes contribute to decreased ice thickness and thus more hazardous conditions for winter travellers. The model illustrates the physical mechanisms which corroborate reports from Alaskans that ice conditions have become more dangerous in the spring, and further suggests that permafrost degradation could contribute to the degradation of river ice in a warming climate.
14084441 Kanevskiy, M. Z. (University of Alaska, Fairbanks, Fairbanks, AK); Shur, Y.; Fortier, D.; Jorgenson, T.; Stephani, E. and Strauss, J. Extreme rates of riverbank erosion of the high bluff formed by the ice-rich syngenetic permafrost (yedoma), Itkillik River, northern Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0536, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Riverbank erosion in areas underlain by ice-rich permafrost is strongly affected by the processes of thawing of ground ice, which include (1) thermal erosion, and (2) thermal denudation. Thermal erosion is a process of combined thermal and mechanical action of moving water, which results in simultaneous thawing of frozen soil and its removal by water. Thermal erosion can cause block collapse of eroded banks. Thermal denudation is a process of thawing of frozen soils exposed in the bluff due to solar energy and consequent removal of thawed soils by gravity. Studies of riverbank and coastal erosion revealed that the highest rates of erosion are typical of bluffs composed by yedoma (ice- and organic-rich syngenetically frozen silty deposits). Yedoma deposits can be up to 50 m thick, and they contain huge ice wedges up to 10 m wide. Since 2006, we have studied the process of riverbank erosion of the 35 m high exposure of yedoma along the Itkillik River in northern Alaska. Based on five measurements of the areas occupied by wedge ice in panoramic photographs taken in 2006, 2007, 2011, and 2012, the average wedge-ice volume makes 61% of the entire exposed bluff. The total volumetric ground ice content of the Itkillik yedoma, including wedge, segregated and pore ice, is 85%. We detect three main stages of the riverbank erosion for the study site and other similar sites in the areas of ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. The first stage includes formation of thermoerosional niches; development of sub-vertical cracks and block-fall collapse of cornices; and thawing and disintegration of blocks of ground ice and frozen soil in the water. All these processes are accompanied by thermal denudation of the exposed bluff. On August 16, 2007, a big portion of the bluff fell down along the crack sub-parallel to the bluff. As a result, the vertical wall more than 65 m long entirely formed by the wedge ice was exposed. This block-fall affected the area of approximately 800 m2, and the volume of frozen soil and ice involved in the block-fall was about 15,000 m3. The riverbank retreat due to thermal erosion and/or thermal denudation, measured from August 2007 to August 2011, varied from less than 10 to almost 100 m. An estimated retreat rate average for the whole 680 m long bluff was 11.4 m/year, but for the most actively eroded central part of the bluff (150 m long) it was 20.3 m/year, ranging from 16 to 24 m/year. During these 4 years, about 650,000 m3 of ice and organic-rich frozen soil were transported to the river from the retreating bank (more than 160,000 m3/year). Analysis of aerial photographs (1948-1979) and satellite images (1974-2013) showed that the riverbank was relatively stable till July 1995, when the Itkillik River changed its course and triggered extremely active thermal erosion. The total retreat of the riverbank in 1995-2010 varied from 180 to 280 m, which means that the average retreat rate for the most actively eroded part of the riverbank reached almost 19 m/year. Such a high rate of riverbank erosion over a long time period has not been reported before for any permafrost regions of Eurasia and North America.
14084440 Kumar, J. (Oak Ridge National Laboratory, Knoxville, TN); Bisht, G.; Liljedahl, A.; Mills, R. T.; Karra, S.; Painter, S. L. and Thornton, P. E. Modeling active layer and permafrost dynamics of ice wedge polygon dominated Arctic ecosystems [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0535, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost soils contains vast stock of frozen organic carbon. As warming climate accelerates the thaw of the permafrost, increasing amount of organic matter is exposed to respiration leading to release of carbon to the atmosphere in the form of CO2 and CH4. Permafrost thermal dynamics play a key role influencing hydrologic and biogeochemical processes in these ecosystems. Large areas of Arctic landscape are covered by the patterned ground features created by repeated freezing and thawing of soil underlain by aerially continuous permafrost. These microtopographic features in the landscape controls the local surface-subsurface hydrology and thermal regimes through differential transport of heat and water. Study of these interacting thermal-hydrologic-biogeochemical in permafrost soils are further complicated by the complex topography and heterogeneity of subsurface. We have developed and applied a coupled multiscale-multiphase-multicomponent surface-subsurface flow and reactive transport model PFLOTRAN for modeling of thermal-hydrologic-biogeochemical processes in permafrost soils. We study the permafrost thermal dynamics, role of microtopography in local scale hydrology at the Department of Energy's Next Generation Ecosystem Experiment (NGEE) - Arctic field sites near Barrow, Alaska. High resolution LiDAR data is used to represent the microtopography at sub-meter resolution in PFLOTRAN. Long term simulations have been conducted at the field sites informed by the observations from field and laboratory campaigns to study and understand the hydrologic and biogeochemical processes in these Arctic ecosystems.
14084425 Liljedahl, A. (University of Alaska, Fairbanks, Fairbanks, AK); Daanen, R. P.; Frost, G. V.; Matveyeva, N.; Necsoiu, M.; Raynolds, M. K.; Romanovsky, V. E. and Walker, D. A. Observed ice wedge degradation at multiple continuous permafrost locations and their simulated effects on watershed scale hydrology [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Wetlands and ice wedge polygon mires occupy a significant portion of Arctic terrestrial landscapes, a region that is important to the global climate system. The different types of ice wedge polygon networks, i.e. low- and high-centered, with and without well-developed troughs, can have major effects on the hydrologic cycle, which ultimately impacts the regional exchange of energy and carbon. Here we present multiple locations of ice wedge degradation observed in the continuous permafrost zones of North America and Eurasia. The subsequent ground subsidence has resulted in major surface water alterations across decadal time periods, some presenting much more rapid permafrost degradation than the typical pan-arctic models predict. Informed by analyses of high-resolution imagery, our model experiments explore the hydrologic impacts of the different stages of landscape-scale hydrologic connectivity. The observed degradation of ice wedges has major effects on watershed hydrology that typical variations in climate forcing alone are unable to produce. Not accounting for the ground subsidence at sub-meter spatial scales undermines the effectiveness of any regional scale projections of water, energy and carbon.
14088781 Loranty, M. M. (Colgate University, Geography, Hamilton, NY) and Berner, L. T. Vegetation controls on carbon, water, and energy dynamics with implications for permafrost thaw [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC22D-05, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Changes in ecosystem structure and function characterized by climate induced alterations in vegetation communities will exert strong influence on the fate of permafrost carbon via controls on surface energy partitioning. These controls are likely to occur both directly through changes in ground heat fluxes and indirectly through climate feedbacks associated with changes in albedo and evapotranspiration. Larch forests of northeastern Siberia constitute the largest ecosystem type underlain by continuous permafrost and therefore warrant considerable attention in this regard. Here we report observations of carbon, water, and energy fluxes made using the static chamber method for three understory vegetation communities in a mature northeastern Siberian larch forest. We find that carbon and water fluxes tend to increase in magnitude with NDVI, with carbon fluxes exhibiting net uptake during the growing season in vegetation communities dominated by deciduous shrubs. Communities characterized by a combination of evergreen and deciduous shrubs and mosses, or by lichens we find lower water fluxes and carbon neutrality. In the case of lichens, water fluxes are low while surface and soil temperatures as well as thaw depths are relatively high. These results illustrate the potential for vegetation to influence permafrost dynamics through controls on surface energy partitioning. While our results stem from a relatively small spatial scale, they are a relevant analog for large-scale shifts in arctic and boreal vegetation communities as well as changes in successional dynamics associated with changing disturbance regimes, particularly fire.
14084422 Lyon, S. W. (Stockholm University, Stockholm, Sweden). Developing a mechanistically consistent picture of permafrost influence on hydrologic response [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-01, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In regions experiencing permafrost thaw, catchment structure is a dynamic factor mediating hydrologic response. Predicting how this mediation will manifest is difficult since there are myriad potential hydrologic consequences from thawing permafrost such as changes to the connectivity of the aquifer system and the amount of water available for groundwater storage. For example, despite similar climate evolution and permafrost degradation over the past century, contrasting trends can be seen in the magnitude and timing of flood peaks and the mean summer discharge regionally across northern Sweden. Complementing hydrological change information with observations and detailed modeling provides a more mechanistically consistent picture of the hydrologic response impacts due to thawing permafrost. This is particularly relevant with regards to the timing of water flows that control the cycling of Carbon and other biogeochemicals within subarctic environments. As such, there is a clear added value in considering coupled process-functional changes in complement to the absolute hydrologic changes that integrate and, thus, may mask subsystem shifts in hydrologic responses (amount and timing).
14088764 Marchenko, S. S. (University of Alaska, Fairbanks, Fairbanks, AK); Wisser, D. and Romanovsky, V. E. Modeling of permafrost dynamics in northern Eurasia; implications to permafrost carbon pool [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0872, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
A recent estimate indicates that the total soil organic carbon is stocked in permafrost contains as much as 50 percent of the global belowground organic carbon pool (Tarnocai et al., 2009). Carbon stocked in permafrost is now regarded as one of the most important carbon-climate feedbacks because of the size of the carbon pool and the intensity of climate change at high latitudes (Schuur et al., 2009). Increasing soil temperatures, and the deepening of the active layer as a result of increasing air temperatures and changing snow dynamics will have implications for the cycling of carbon in peatlands and for the fluxes of carbon and methane to the atmosphere and to the hydrosphere, as biogeochemical processes in peatlands are partly controlled by the freeze/thaw state of the (peat) soil. To investigate how changes in these factors influence permafrost dynamics in the Arctic, we developed a Geophysical Institute Permafrost Lab (GIPL) permafrost dynamics model. This model simulates soil temperature dynamics and depth of seasonal freezing and thawing by solving a non-linear heat equation with phase change numerically. We assess the changes in permafrost characteristics in Northern regions of Eurasia using a large scale, grid-based permafrost model that simulates the distribution of soil temperature and active layer dynamics, permafrost thawing and freezing, using a five-model composite projection derived from IPCC climate models outputs of future climate for the next century. The model takes into account the geographic distribution of organic soils and peatlands, vegetation cover and soil properties, and is tested against a number of permafrost temperature records for the last century. Despite the slower rate of soil warming in peatland areas and a slower degradation of permafrost under peat soils, a considerable volume of peat (approximately 20% of the total volume of peat in Northern Eurasia) could be thawed by the end of the current century. The potential release of carbon and the net effect of this thawing will depend on the balance between increased productivity and respiration, and will be mitigated by peat moisture. Consistent with observations for the recent decades and with other model simulations of soil temperatures under future climate conditions, we find a widespread degradation of permafrost in Northern regions by the end of the century. The model results indicate 1,200 cubic km of seasonally unfrozen soils within the two upper meters across 10,800,000 quadratic km of northern Eurasian permafrost domain during the last two decades of the 20th century. Our projections have shown that unfrozen volume of soil within two upper meters increases to 3,500 cubic km by 2050 and to 9,500 cubic km by the last decade of the 21st century due to active layer deepening. According to this specific climate scenario, the area of permafrost with active layer shallower than 2 m in depth could decrease from 10,800,000 quadratic km in 2000 to 9,000,000 quadratic km by 2050 and to 6,000,000 quadratic km by the end of current century.
14084423 Marsh, P. (Wilfrid Laurier University, Waterloo, Canada); Yang, D. and Shi, X. Changes in permafrost hydrology at the Arctic treeline in the Western Canadian Arctic [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The climate of the Western Canadian Arctic has undergone dramatic changes, with warming air temperature and decreasing winter and summer precipitation, over the last 50 years. This has resulted in changes to permafrost in this region, including a deepening of the active layer as well as melting of massive ice layers that result in changes in ice wedge polygons and lake drainage, with obvious changes in surface drainage patterns. In addition, north of the treeline there is an ongoing change from tundra to shrub tundra, with impacts on snow cover, soil moisture and surface energy balance and permafrost. These changes would be expected to have a significant impact on hydrology. This paper will outline past changes in climate and permafrost in this region of continuous permafrost, and discuss the observed impacts of these changes on hydrology, including earlier snowmelt runoff, earlier rainfall runoff during the later stages of melt, and decreases in summer runoff. In addition, we will outline a new research project that is using detailed observations along with high resolution modelling to consider the complex interactions between climate, snow, vegetation, permafrost and hydrology.
14084429 Minsley, B. J. (U. S. Geological Survey, Crustal Geophysics and Geochemistry Science Center, Denver, CO); Wellman, T. P.; Walvoord, M. A.; Voss, C. I. and Revil, A. Predicting the geophysical response to changes in permafrost associated with lake talik evolution [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-08, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Hydrologic processes are tightly coupled with permafrost systems in cold regions. Here, we focus on the use of geophysical measurements to help characterize changes in permafrost associated with groundwater flow and lake talik development. Simulations of talik formation using the SUTRA groundwater simulator with freeze-thaw physics are conducted for different climate, lake size, and lake-groundwater relation scenarios over a 1,000 year period. Simulations are based on watersheds in the Yukon Flats region of Alaska, where recent airborne and ground-based geophysical data have been acquired. We build on the SUTRA simulations by predicting the geophysical response to these different scenarios, which helps to guide the interpretation of existing geophysical data, and to plan for future field campaigns by evaluating the sensitivity of different types of surveys to physical property changes of interest. Analyzing the geophysical response to hydrologic simulations involves three steps: (1) development of a physical property relationship between SUTRA state variables and bulk geophysical properties, (2) forward simulation of different types of geophysical data, and (3) inversion of simulated geophysical data under realistic assumptions of data errors. This work focuses on the use of electrical and electromagnetic geophysical methods, which are sensitive to the electrical resistivity structure in the subsurface. We have adapted existing models of electrical properties in variably saturated media to describe variations in resistivity as a function of ice saturation and temperature output at each time step of the SUTRA simulations. Forward and inverse modeling of simulated airborne geophysical data indicate sensitivity to changes in lake talik geometry both spatially and as a function of time. We will compare simulated geophysical results with field data from the Yukon Flats area, and discuss the ability to resolve specific features of interest based on forward and inverse modeling results.
14084442 Morton, D. (University of Alaska, Fairbanks, Arctic Region Supercomputing Center, Fairbanks, AK); Bolton, W. R.; Young, J. and Hinzman, L. D. Application of a catchment characterization hydrologic model for exploring parameter sensitivities in a boreal forest, discontinuous permafrost ecosystem [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0537, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Many of the expected climate-driven changes in sub-arctic ecosystems, such as increased temperature and precipitation, decreased permafrost extent, tree-line expansion and vegetation composition, have been identified as potential mechanisms that may lead to shifts in the Arctic Ocean freshwater budget. Understanding the feedback mechanisms of the water cycle are paramount, in that small changes may result in dramatic threshold changes in the hydrology, ecology and surface energy balance. As part of a study on how vegetation water use and permafrost dynamics impact stream flow in the boreal forest discontinuous permafrost zone, we are integrating a vegetation water use model and a simple, first-order, non-linear hydrological model, utilizing a Bayesian analysis approach to fully account for and propagate uncertainty through this modeling system. With an overall goal of improving parameterizations of large-scale hydrological models, we are constructing a simple and portable hydrologic model within a Bayesian framework. Thus, uncertainty associated with the evaporation (E), transpiration (T), precipitation (P), and streamflow (Q) submodels will be propagated into the final hydrology model. An immediate application of the modeling system will be used to explore the hydrological impacts of different vegetation distributions found in the boreal forest. In this work, we describe the basic structure of this flexible, object-oriented model and test its performance against collected basin data from headwater catchments of varying permafrost extent and ecosystem structure (deciduous versus coniferous vegetation). We will also do analyses to assess model sensitivity to each parameter (E, T, P, Q) and to different climate scenarios. This model is a major advancement for hydrological models that will aid in assessing sources of uncertainty in boreal hydrological systems.
14088779 Natali, S. (Woods Hole Research Center, Falmouth, MA); Kholodov, A. L.; Spektor, V.; Bunn, A. G.; Schade, J. D.; Loranty, M. M.; Mann, P. J.; Zimov, N.; Davydov, S.; Berner, L. T.; Webb, E.; Heard, K.; Shin, S.; Spawn, S. and Han, P. Permafrost carbon pools in a larch-dominated watershed in northeast Siberia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC22D-03, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
As the climate warms, the large pool of carbon (C) stored in permafrost is at risk of being thawed, decomposed, and transferred to the atmosphere, which may shift the arctic region from a C sink to a source by the end of the 21st century. Despite the importance of permafrost C as a potential positive feedback to climate change, large uncertainties remain in estimating the size of the frozen C pool. Measurements of plant, soil and permafrost C stocks, particularly in under-sampled regions of Siberia, are needed to help constrain estimates of the current C pool size and the potential magnitude of climate feedbacks. Here we present above- and below-ground C stocks from a larch (Larix cajanderi) dominated sub-catchment in northeast Siberia. This fire-prone system is underlain by Pleistocene-aged loess deposits. The high ice (50-90%) and organic matter content of these yedoma deposits, makes this region particularly vulnerable to ground subsidence and highly relevant in terms of permafrost-climate feedbacks. We sampled thawed and frozen soil horizons from 24 permafrost cores to 1-m depth, as well as from two 15-m-deep permafrost cores, and estimated ice content and C pools across the depth profiles. These permafrost samples were collected at 10 sites where we also quantified stand characteristics including larch biomass and density, understory plant composition, organic matter depth, and thaw depth. These results will help constrain estimates of permafrost C stocks by linking above- and below-ground C dynamics and evaluating spatial variability in permafrost C pools across the landscape.
14084428 O'Donnell, J. A. (National Park Service, Arctic Network, Fairbanks, AK); Aiken, G.; Walvoord, M. A. and Butler, K. Using dissolved organic matter (DOM) composition to detect permafrost thaw in Arctic and boreal watersheds [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-07, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost thaw can profoundly alter hydrology and carbon dynamics in northern high-latitude regions. Thawing of permafrost has been detected through monitoring of borehole temperatures and active layer thickness (ALT), but these measurements have limited spatial inference and primarily reflect local conditions. Remote sensing analyses have been useful for detecting thermokarst features, yet have limited application in upland forests or in ice-poor regions not susceptible to ground subsidence. Analysis of stream discharge time-series (e.g. recession flow analysis) can be a powerful tool for detecting watershed-scale changes in ALT, but long-term hydrologic data is sparse in many northern regions. Given the large pool of organic carbon (C) in permafrost soils, most research has focused on how permafrost thaw impacts C released to the atmosphere. However, permafrost thaw may also modify the lateral flux of C from terrestrial to aquatic systems, often through increasing groundwater discharge to stream flow. Here, we present data from arctic (n=36) and boreal rivers (n=60) of Alaska to address the question: can DOM character in rivers be used as a tool for detecting permafrost thaw in high-latitude watersheds? We hypothesize that the chemical composition of DOM is sensitive to permafrost configuration as a control on (1) groundwater transit times, (2) microbial processing, and (3) stabilization in mineral soils. Using measurements of DOM optical properties, chemical fractionation, and 14C-DOC, we distinguished DOM character between supra- and sub-permafrost aquifers. DOM transported from supra-permafrost soils to rivers is subject to seasonal thawing and re-freezing of the active layer. DOC concentrations peaked during spring snowmelt (7.5 to 41.7 mgC L-1), when frozen soils confine subsurface flow to organic-soil horizons, and declined during summer (2.6 to 27.3 mgC L-1), when soils of the active layer thaw. D14C-DOC in three boreal rivers also declined seasonally, reflecting a positive relationship between thaw depth and DOC age. In a complimentary lab experiment, we observed increases in SUVA254 (an index of DOM aromaticity) from near-surface soil (2.28 ± 0.27 L mgC-1 m-1) to deeper, more decomposed organic-soil horizons (3.86 ± 0.60 L mgC-1 m-1), indicating the importance of substrate and microbial processing on DOM production. Riverine DOM originating in sub-permafrost aquifers (as determined from winter flow, springs, and spring-fed streams) was characterized by low DOC concentrations (0.6 to 5.8 mgC L-1), low SUVA254 values (0.7 to 2.9 L mgC-1 m-1), a high percentage of hydrophilic compounds (16 to 44%), low D14C-DOC (-46 to -24ppm), and in some instances, high DON concentrations and protein-like fluorophores. Under projected thawing scenarios, model simulations predict a decline in groundwater discharge from supra-permafrost aquifers coinciding with increased discharge from sub-permafrost aquifers. Our findings suggest that measurements of DOM character may be a useful tool for detecting these changes in watershed hydrology with ongoing and future permafrost thaw.
14084426 Painter, S. L. (Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM); Moulton, J. D.; Wilson, C. J.; Atchley, A. L.; Berndt, M.; Coon, E.; Gangodagamage, C.; Garimella, R.; Miller, T. A. and Short, L. S. Microtopography-resolving simulations of surface and subsurface hydrology in thawing and topographically evolving permafrost regions [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-05, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Simulating the hydrologic system in degrading permafrost regions is challenging because of the potential for topographic evolution and associated drainage network reorganization as permafrost thaws and massive ground ice melts. The critical process models required for simulating hydrology in permafrost affected regions include subsurface thermal hydrology of freezing/thawing soils, thermal processes within ice wedges, mechanical deformation processes, overland flow, and surface energy balances including snow dynamics. A new simulation tool, the Arctic Terrestrial Simulator (ATS), is being developed to simulate those coupled processes. Overland flow with freezing of ponded water is represented with a new non-isothermal extension of the diffusion wave equation. Moisture dynamics in the subsurface is represented by a three-phase, non-isothermal extension of Richards equation. The subsurface and surface non-isothermal flow models are coupled with a surface energy balance and a single-layer snow model. A vertical grid displacement algorithm based on calculated melt volumes of massive ground ice is used in place of more expensive soil geomechanics calculations to represent topographic evolution. Highly parallel simulations using high-resolution digital elevation maps of the polygonal patterned ground landscape at the Barrow Environmental Observatory illustrate the strong feedbacks among the processes. Challenges and potential approaches to parameterizing, initializing, and building confidence in the complex coupled models will also be discussed. This work was supported by LANL Laboratory Directed Research and Development Project LDRD201200068DR and by the The Next-Generation Ecosystem Experiments (NGEE Arctic) project. NGEE-Arctic is supported by the Office of Biological and Environmental Research in the DOE Office of Science.
14084450 Quinton, W. L. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Sonnentag, O.; Connon, R. and Chasmer, L. The growth of permafrost-free bogs at the southern margin of permafrost, 1947-2010 [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0546, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In the high-Boreal region of NW Canada, permafrost occurs predominantly in the form of tree-covered peat plateaus within a permafrost-free and treeless terrain dominated by flat bogs. This region is experiencing unprecedented rates of thaw. Over the last several decades, such thaw has significantly expanded the permafrost-free, treeless terrain at the expense of the plateaus. This rapid change in land-cover has raised concerns over its impact on northern water resources, since remotely sensed data and ground observations indicate that the two major land-covers in this region have very different hydrological functions. Peat plateaus have a limited capacity to store water, a relatively large snowmelt water supply and hydraulic gradients that direct excess water into adjacent permafrost-free wetlands. As such, the plateaus function primarily as runoff generators. Plateaus also obstruct and redirect water movement in adjacent wetlands since the open water surfaces of the latter occupy an elevation below the permafrost table. By contrast, bogs are primarily water storage features since they are surrounded by raised permafrost and therefore less able to exchange surface and near-surface flows with the basin drainage network. Accurate estimate of the permafrost and permafrost-free areas is needed for accurate predictions of basin runoff and storage. This study examines the perimeter-area characteristics of bogs and permafrost plateaus, using fractal geometry as a basis for quantifying these properties. Image analyses are applied to aerial photographs and satellite imagery of Scotty Creek, NWT over the period 1947-2010. Preliminary analyses suggest that the expanding bogs and shrinking permafrost plateaus behave as fractals, meaning that their perimeter-area characteristics can be described by simple power equations. The area-frequency characteristics of bogs and plateaus have a hyperbolic distribution with relatively few large bogs and plateaus and numerous small ones. The bogs and plateaus have different fractal dimensions, since bogs evolve from small, simple (i.e. circular) shapes to large, complex shapes, while thaw transforms plateaus from large and complex shapes to small, simple ones. It is concluded that the size distributions of plateaus and bogs are not random but predictable. The variation in plateau edge length per unit basin area over the 1947-2010 period is demonstrated. A maximum value of the ratio was reached when permafrost covered 45-65% of the basin. Permafrost thaw driven by energy advection from adjacent bogs would therefore be greatest when the coverage of plateaus is in this range.
14084455 Rivière, A. (University of Calgary, Department of Geoscience, Calgary, AB, Canada); Anne, J. and Goncalves, J. A combined experimental and numerical study of pore water pressure variations in sub-permafrost groundwater [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0551, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The past few decades have seen a rapid development and progress in research on past and current hydrologic impacts of permafrost evolution. In permafrost area, groundwater is subdivided into two zones: supra-permafrost and sub-permafrost which are separated by permafrost. Knowledge of the sub-permafrost aquifers is often lacking due to the difficulty to access those systems. The few available data show that this aquifers are generally artesian below the continuous permafrost. In the literature, there are two plausible explanations for the relatively high pore pressures in the sub-permafrost aquifer; the recharge related to the ice sheet melting and the expulsion of water related to the ice expansion. In this study, we investigated areas where ice sheets have never developed like in the Paris basin region. The ice expansion induces also soil surface uplift. Our study focuses on modifications of pore water pressure in the sub-permafrost aquifer and the soil surface motion during the permafrost development (freezing front deepening). To fill in the gaps to the field data availability, we developed an experimental approach. Experimental design was undertaken at the Laboratory M2C (Universite de Caen-Basse Normandie, CNRS, France). The device consisted in a 2 m2 box insulated at all sides except on the top where a surface temperature was prescribed. The box is filled with silty sand of which hydraulics and thermal parameters are known. Soil temperatures, pore water pressure and soil motion are continuously recorded at different elevations in the sand-box. We developed a two-dimensional transient fully coupled heat and water transport model to simulate thawing and freezing processes taking into account the phase change (Latent heat effects). The balance equations are solved using of a finite difference numerical scheme. Experimental results are used to verify the implementation of the hydro-mechanical processes in our numerical simulations. Experimental and numerical approaches allowed us to verify and quantify the fact that the pressures induced by the ice volumetric expansion are translated into overpressure generated in sub-permafrost groundwater and a soil surface uplift.
14088756 Semiletov, I. P. (University Alaska, Fairbanks, International Arctic Research Center, Fairbanks, AK); Shakhova, N. E.; Pipko, I.; Repina, I.; Pugach, S.; Dudarev, O. and Charkin, A. Acidification of the shallow Arctic seas as biogeochemical consequences of permafrost degradation [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0860, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
There is increasing concern about consequences of ocean acidification from the increasing atmospheric carbon dioxide driven shifts toward lower seawater pH The largest pH changes in this century are anticipated in the surface waters of the Arctic ocean (Orr et al., 2005; Steinacher et al., 2009). Concurrently, aragonite undersaturation might occur locally and become widespread as atmospheric CO2 increases to more than 450ppm (Olafsson et al., 2009). However, the ocean acidification effects induced by increasing Arctic land-shelf export of fluvial and erosional organic carbon (OC) and its oxidation are unknown. Here we show that massive net redistribution of old OC from thawing permafrost to the East-Siberian Arctic Seas (ESAS) and its consequent remineralization drives acidification over the ESAS which represents the broadest and shallowest shelf of the World Ocean. From top to the bottom the ESAS waters were observed to be undersaturated with respect to aragonite and calcite, and thus potentially corrosive to CaCO3 for the shelf sediments and benthic ecosystems. Our multiyear all-seasonal results (1999-2011) demonstrate how the net ecosystem metabolism of the Siberian shelves, which is the net balance of autotrophic (photosynthesis and net community production) and heterotrophic (respiration and remineralization) processes, is likely to function as the heterotrophic dominated ecosystem. CO2 outgassing from the East Siberian Arctic Shelf (ESAS) is quantified using multi-year eddy-correlation flux measurements. It is shown that the ESAS is currently a source of atmospheric CO2. A continuing warming adds more terrestrial OC to the Arctic Shelf Seas, which increases pCO2, as the same time as decreased transparency lowers primary production, which reduce consumption of CO2 (and increase acidification effects). This effect results in a positive feedback by outgassing CO2 over the Siberian Shelf , which comprises one half of the entire shelf area. This multi-year study (1994-2011) is supported by the Russian Foundation for Basic Research, the NOAA OAR Division, the US NSF, and the Far Eastern Branch of the Russian Academy of Sciences. The International Siberian Shelf Study cruise-2008 was supported by the Wollenberg Foundation and the Sweden Research Polar Secretariat.
14088762 Streletskiy, D. A. (George Washington University, Department of Geography, Washington, DC) and Grebenets, V. I. Urban landscapes on permafrost; Oganer case study [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0870, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Norilsk with a population of 205,000 is by far the biggest city ever built on permafrost. Oganer, located near Norilsk is the latest administrative unit of the city with a population of about 7,000 people. It was originally designed as a satellite city for about 50-80 thousand workers and their families. Idea of a satellite city became apparent in mid-80th, when Norilsk was unable to grow to extent needed to accommodate large workforce. Located in a valley, the city was already surrounded by two metallurgy plants and steep mountains slopes. The only direction of city limit extension was east, but the area was previously occupied by garages and barracks resulting in deterioration of cold permafrost and decrease in high bearing capacity of the ground required for construction of large residential houses. Oganer was built 8 km east from the Norilsk, where initial geologic survey shown close location of bedrock to the surface making possible construction of large structures on permafrost. First houses were built in 1986 according to the passive principle of construction on permafrost. Additional geologic surveys in Oganer revealed that original bedrock extent is quite small and subsequent construction had to deal with ice-reach (40-60%) permafrost in fine-grained sediments (silt and clay). The change in economic direction in the beginning of 1990s resulted in population outmigration from Norilsk, so Oganer originally planned as a large 5-district city was never complete. Presently, it is represented by only one district, with several 9-storey tall buildings which were never complete. Despite that mean annual temperature is -9.7 C, permafrost temperature is relatively warm -1..-3 C. High permafrost temperature, presence of ground ice and large bodies of tabular ground ice in the area made construction quite challenging. In the paper we demonstrate how climate and various construction practices and designs used in the city modified natural landscapes, and how periglacial processes, such as thermokarst and frost heave in turn reacted on those changes affecting roads, utility lines, buildings and structures.
14084438 Westermann, Sebastian (University of Oslo, Oslo, Norway) and Etzelmuller, Bernd. Permafrost thawing and increased winter discharge in northern Norway; is there a connection? [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0533, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Trends of increasing winter river discharge have been observed in many areas in the Arctic. Spatially distributed modeling of the ground thermal regime in conjunction with multi-decadal time series of discharge measurements provides the opportunity to investigate the role of permafrost thaw as contributing factor to such changes. In Northern Norway, there exist a number of gauged watersheds in permafrost regions for which 30- to 100-year records of discharge measurements are available. Numerical simulations of the evolution of the ground temperature regime have been performed at 1 km resolution with the transient permafrost model CryoGrid 2 (Westermann et el. 2013) for the last 50 years for an area of approximately 55,000 km2. As an example, we present the Iesjohka watershed, located at 69.5°N with a size of approximately 2000 km2. It extends across the boundary between permafrost-free coastal regions and more continental plains dominated by discontinuous permafrost, and features a variety of landcover types including organic-rich palsa mires. During summer, the Iesjohka has an average discharge of 20 to 50 m3/s, while the typical winter discharge is on the order of a few m3/s. Since the beginning of measurements in 1974, the average discharge in the winter months November to February and the annual minimum discharge have more than doubled, while CryoGrid 2 simulations show that permafrost has crossed the thawing threshold in a large part of the watershed between 1980 and 2010. In 2013, degradation of palsas and collapses of peat plateaus have been observed at many places along a 50 km transect through the watershed, transforming comparatively dry areas underlain by permafrost in permafrost-free water-saturated mires. Similar increases of the winter discharge have been observed for other permafrost watersheds in Northern Norway, thus suggesting a causal relationship between permafrost thaw and increased winter discharge. To further investigate this hypothesis, we analyze trends of other environmental factors influencing the winter discharge, such as winter rain and snow melt events, as well as summer precipitation determining soil moisture prior to ground freezing. We present a conceptual model how degradation of palsas and peat plateaus could contribute to an increased winter discharge.
14088758 Zyryanov, V. (Russian Academy of Sciences, V.N.Sukachev Institute of Forest, Krasnoyarsk, Russian Federation); Tchebakova, N. M.; Nakai, Y.; Zyryanova, O.; Parfenova, E. I.; Matsuura, Y. and Vygodskaya, N. Comparison of CO2 fluxes in a larch forest on permafrost and a pine forest on non-permafrost soils in central Siberia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0863, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Inter-annual and seasonal variations of energy, water and carbon fluxes and associated climate variables in a middle taiga pine (Pinus sylvestris) forest on warm sandy soils and a northern taiga larch (Larix gmelini) forest on permafrost in Central Siberia were studied from eddy covariance measurements obtained during growing seasons of 1998-2000 and 2004-2008 (except 2006) respectively. Both naturally regenerated after fire forests grew in different environments and differed by their tree stand characteristics. The pure Gmelin larch stand was 105 yr old, stem density of living trees was about 5480 trees/ha, LAI was 0.6 m2/m2, biomass (dry weight) was 0.0044 kg/m2, with average diameter of the trees at breast height 7.1 cm and mean tree height 6.8 m. The pure Scots pine stand was 215 yr old, stand structure was relatively homogenous with a stem density of 468 living trees/ha, LAI was 1.5 m2/m2, biomass (dry weight) was 10.7 kg/m2, with average diameter of the trees at breast height 28 cm and mean tree height 23 m. The climatic and soil conditions of these ecosystems were very distinctive. The habitat of the larch forest was much colder and dryer than that of the pine forest: the growing season was 1 month shorter and growing-degree days 200°C less and winters were about one month longer and colder with January temperature -37°C versus -23°C; annual precipitation was 400 mm in the larch versus 650 mm in the pine forest and maximal snow pack was 40 cm vs 70 cm. The soils were Gelisols with permafrost table within the upper 1 m in the larch stand and Pergelic Cryochrept, alluvial sandy soil with no underlying permafrost. Average daily net ecosystem exchange (NEE) was significantly smaller in the larch ecosystem - (-3-6) mmol/m2s compared to that in the pine forest (-7-8) mmol/m2s, however daily maximal NEE was about the same. Seasonal NEE in the larch forest on continuous permafrost varied from -53 to -107 and in the pine forest on non-permafrost from -180 to -245 gC/m2season. Our maximal net CO2 uptake was close to that of a Gmelin larch forest on the continuous permafrost in eastern Siberia characterized by 6 mmol/m2s in the mid-summer. Compared to a L. cajanderi forest on sandy soil within a wide flooded valley of Lena River characterised by the flux of (-10-18) mmol/m2s, our fluxes were 3 times less. Seasonal carbon dioxide exchange in our Gmelin larch ecosystem appeared to be the weakest among Siberian and other boreal ecosystems studied worldwide we found in literature.
14088773 Bruhwiler, L. (NOAA, Earth System Research Laboratory, Boulder, CO). Arctic permafrost and carbon climate feedbacks [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21F-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Vast stores of organic carbon are thought to be frozen in Arctic soils; as much as 1,700 PgC, several times the amount emitted by fossil fuel use to date and about equal to known coal reserves. If mobilized to the atmosphere, this carbon would have significant impacts on global climate, especially if emitted as CH4, a gas that is about 25 times more potent a greenhouse gas per mass than CO2 over a century timescale. Arctic temperatures have been increasing rapidly over the last several decades, with melting of ice both on sea and land, sometimes at surprisingly fast rates. Human activities in the Arctic are sure to expand as the climate moderates, and one of the challenges confronting our ability to predict the future global climate is understanding the potential evolution of trace gas budgets in the Arctic. Bottom-up estimates from flux towers and chamber studies over the past several decades imply that the Arctic is taking up more CO2 and emitting more CH4. Atmospheric network observations do not currently support long-term increases in CH4 emissions, although inter-annual variability due to year-to-year temperature changes is seen in the atmospheric data. Small changes in CO2 uptake are difficult to detect given the overwhelming dominance of the fossil fuel emissions in the CO2 budget. A commitment to long-term monitoring of greenhouse gases using both regionally representative bottom-up measurements and top-down atmospheric network observations in the Arctic is fundamental to our ability to detect early changes in carbon emissions, as well as to evaluate and test models that predict future carbon cycle climate feedbacks.
14088782 Spektor, V. (Russian Academy of Sciences, Melnikov Permafrost Institute, Yakutsk, Russian Federation); Kholodov, A. L.; Spawn, S.; Schade, J. D.; Natali, S.; Davydov, S.; Bulygina, E. and Khokhlova, G. Permafrost organic matter study in the Lower Kolyma Lowland (eastern Siberia) based on drilling record [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC22D-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In 2012-2013, a complex study of perennially frozen mineral soils of MIS 3-2 and MIS 1 as well as soils of modern active layer was conducted on the Kolyma River Lowland (North-East Russia) in the vicinity of town Chersky (N68°44' E161°23'). For this investigation, five boreholes, ranging from 13 to 22 m in depths, were drilled on different elevations on yedoma surface, thermokarst depression (alas), and modern floodplain of the Kolyma River. The study focuses on reconstruction of environmental conditions during and after the formation of Pleistocene Ice complex (yedoma). Special attention is drawn to extent of transformation of organic matter by TOC, %N, C/N, d13C, d15N, and enzyme analysis corresponding to changes of climate established by spore and pollen analysis and AMS 14C dates. For instance, the deepest silt layers (15 m) from the BH 12/1 drilled in yedoma near Chersky are characterized by a pollen complex peculiar to open landscapes with domination of gramineous and mixed herbs associations, formed in the conditions of severe climate. AMS 14 C dates attest that its formation took place ca. 42 kyr (MIS 3). Along the profile of the BH 12/1, %N varies between 0.1-0.11, %C is 0.5-1.59, C/N ratio is 10-19.8, d13C/12C is -26.4...-41.7, d15N/14N is 2.3-4.5.
14089489 Corbett, Lee B. (University of Vermont, Department of Geology, Burlington, VT); Kelly, Meredith A.; Osterberg, Erich C.; Axford, Yarrow and Lasher, G. Everett. Glacial sediments and landscape chronology in Thule, northwestern Greenland [abstr.]: in Geological Society of America, Northeastern Section, 49th annual meeting, Abstracts with Programs - Geological Society of America, 46(2), p. 44, 2014. Meeting: Geological Society of America, Northeastern Section, 49th annual meeting, March 23-25, 2014, Lancaster, PA.
To study the glacial history of Thule, northwestern Greenland, we conducted surficial geologic mapping, excavated soil pits and stratigraphic sections, sampled boulders for cosmogenic nuclide analysis, and collected shells from marine deposits for radiocarbon dating. The Thule land surface is covered by at least two till units. The till covering the majority of the landscape is dense, has a clay-rich matrix, and contains permafrost features such as sorted circles. Boulders in the clay-rich till show evidence for long-lived subaerial weathering. Preliminary minimum limiting 10Be exposure ages from boulders at the surface of this till are 21.7, 26.4, and 28.3 ka. A second till unit covers a small area of land (~20 km2) north of Thule in a bowl-shaped depression adjacent to a large fjord and outlet glacier. This till unit has a sandy matrix, a hummocky surface, and contains numerous moraines; boulders contained within it have fresh surfaces and no permafrost land surface features are visible. Preliminary minimum limiting 10Be exposure ages from boulders in this unit are 11.7 and 26.9 ka. Excavation of stratigraphic sections in stream channels near the moraines indicates that the sandy till overlies shell-rich marine sediments. Based on the spread of exposure ages, we hypothesize that boulders in the clay-rich till contain inherited 10Be. They may have been deposited during an earlier glaciation and then preserved beneath cold-based ice. The sandy till likely represents a later period of ice advance, perhaps one that was predominately confined to the fjords since its spatial extent is limited. This later re-advance may have incorporated both fresh and reworked rock material, leading to the disparate exposure ages. Since the sandy till overlies marine sediments, the re-advance may post-date the Last Glacial Period and the marine high-stand. Future work will focus on obtaining more detailed landscape chronology. We will perform multi-isotope cosmogenic analysis of boulders in both till units in order to study exposure/burial history and to determine the timing of the re-advance that deposited the sandy till. We will also use radiocarbon dating of marine shells to provide a maximum limiting estimate for the age of the re-advance.
14089482 Longo, William M. (Brown University, Department of Geological Sciences, Providence, RI) and Huang, Yongsong. Alkenones and polycyclic aromatic hydrocarbons record temperature and fire in northeastern Alaskan lakes [abstr.]: in Geological Society of America, Northeastern Section, 49th annual meeting, Abstracts with Programs - Geological Society of America, 46(2), p. 42, 2014. Meeting: Geological Society of America, Northeastern Section, 49th annual meeting, March 23-25, 2014, Lancaster, PA.
The Arctic is warming twice as fast as the rest of the globe and undergoing shifts in ecological disturbance regimes. These changes threaten to destabilize vast permafrost carbon reservoirs and are potential positive feedbacks to global climate change. To predict the consequences of continued arctic warming we must develop a baseline for past climate variability and its associated feedbacks using proxy records from geological archives. The goal of this research was to develop and apply two lacustrine organic geochemical proxies (alkenones and polycyclic aromatic hydrocarbons) in northeastern Alaska (NE AK) to better understand the region's climate and fire history. To develop alkenone paleothermometry in NE AK we applied our new method for alkenone analysis which uses a poly(trifluoropropylmethylsiloxane) stationary phase with gas chromatography-flame ionization detection (GC-FID). The method separated 16 alkenones from NE AK lakes and revealed 4 novel alkenones that went undetected with traditional methods. Analysis of water column particulates revealed that several indices of alkenone unsaturation were well correlated with in situ lake water temperature, allowing for a robust UK37 temperature calibration (UK37=0.022T-0.764; R2=0.86; p<0.01; n=60). Our application of the calibration to a sediment core from Lake E5, AK (68.38°N, 149.37°E), yielded a 5 kyr early summer water temperature record that shows 2-3°C of variability, slight warming in the last century and general agreement with other arctic records including a recent 2,000 year temperature synthesis [Kaufman, D. S. et al. Recent warming reverses long-term arctic cooling. Science 325,1236-9 (2009)]. Fire records from NE AK are sparse, however recent studies suggest summer temperature is a dominant variable controlling the occurrence and severity of fire in the region. The Anaktuvuk River Fire (68.99°N, 150.28°E) occurred in 2007 and doubled the area burned in the Alaskan arctic tundra for the last 50 years. This major event was recorded by polycyclic aromatic hydrocarbons (PAHs) in the sedimentary record of Dimple Lake, motivating further investigation of the PAH fire proxy in NE AK. Together, alkenones and PAHs compliment traditional proxy records from the region and enhance our understanding of the region's fire and climate history.
14084456 Berman, S. L. (Clark University, Graduate School of Geography, Worcester, MA); Frey, K. E.; Griffin, C. G. and Zimov, N. Thermokarst lake carbon storage and transport near Cherskiy, northeast Siberia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0552, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Thermokarst lakes are prevalent features across the pan-Arctic landscape. As the Arctic climate warms further, thermokarst lakes currently situated in continuous permafrost will likely increase in size and number. Shifting lake distributions may have significant impacts on the land-atmosphere exchange of carbon, as these lakes act as reservoirs and conduits that store and transport carbon and other organic material across the landscape. Using field data collected in the Kolyma River basin in the continuous permafrost region near Cherskiy, Northeast Siberia, we investigate the carbon dynamics of four thermokarst lakes in the Y4 watershed, a small, upland drainage area. Through bathymetric mapping of these four lakes, total lake volume was calculated. Depth profiles of temperature, specific conductivity, pH, and dissolved oxygen were collected across horizontal transects and subsequently integrated with these total volume measurements to determine physical characteristics of the lakes. Additionally, water samples were collected at various stations and depths for analyses of dissolved organic carbon (DOC) and chromophoric dissolved organic matter (CDOM). With these physical and biogeochemical measurements in concert, we investigated the ability for these lakes to store and transport carbon through the Y4 watershed. Furthermore, detailed knowledge of CDOM concentrations in these lakes provides an understanding of the lability and molecular weight of the organic matter as well as potential light transmittance through the water column. This watershed area provides a representative example of the potential for thermokarst lakes in yedoma regions to process and move carbon across the landscape and ultimately to larger systems such as the Kolyma River basin. This baseline characterization of regional lakes will lead to a better understanding of how further warming and permafrost instability may impact the carbon dynamics of thermokarst lakes and ultimately how they function in the broader biogeochemical and hydrological systems throughout the region.
14084424 Boike, J. (Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute, Potsdam, Germany); Langer, M.; Fedorova, I.; Muster, Sina; Kutzbach, Lars and Cresto Aleina, Fabio. It's all about water; from small scale hydrologic processes in ice wedge polygonal tundra and thermokarst lakes to larger scale river runoff (Lena River Delta, Siberia) [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C52A-03, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Lena River Delta in Northern Yakutia forms one of the largest deltas in the Arctic and its catchment area (2 430 000 km2) is one of the largest in the whole of Eurasia. The Lena River distributes water and sediment in four main channels before discharging in total about 30 km3 of water through the delta into the Arctic Ocean every year and its discharge has been observed to be increasing. The goal of this presentation is to characterize the hydrologic processes that are strongly affected by a transient climate component- the permafrost. Permafrost plays a major role for storage and release of water to rivers and surface and subsurface water bodies. Conversely, the coupled water and heat fluxes in the atmosphere and below ground have a marked influence on the permafrost's thermal regime. Our study site, the Lena River Delta, is also one of the coldest and driest places on Earth, with mean annual air temperatures of about -13 °C, a large annual air temperature range of about 44 °C and summer precipitation usually less than 150 mm. Very cold continuous permafrost of about -8.6 °C (11 m depth) underlays the area between about 400 and 600 m below surface and since 2006 the permafrost has warmed than 1 °C at 10.7 m. Roughly half of the land surface is dominated by wet surfaces, such as polygons, ponds and thermokarst lakes. This contribution summarizes past and ongoing research on hydrologic processes across spatial scales, from microtopographic processes of polygonal tundra to regional scale deltaic processes to assess short and long term changes in water fluxes. We quantify unfrozen water in soils, streams and river discharges and water bodies' storage at larger scales. Water bodies were mapped using optical and radar satellite data with resolutions of 4 m or better, Landsat-5 TM at 30 m and the MODIS water mask at 250 m resolution. Ponds, i. e. water bodies with surface are smaller than 104 m, make over 95 % of the total number of water bodies and are not resolved in Landsat-scale land cover classifications. Ponds are generally well mixed and experience high water temperatures up to 23 °C during the summer and are, therefore, hotspots for biological activity and CO2 emission. The ponds in the study area freeze completely in winter, whereas the deeper thermokarst lakes do not freeze to the bottom, with implications for coupling of the permafrost to the atmosphere. These deep thermokarst lakes are thermally stratified during winter and reach maximum water temperatures of up to 19 °C during summer. The summer water balance at the catchment scale was found to be mainly controlled by vertical fluxes (precipitation and evapotranspiration). On the other hand, redistribution of storage water due to lateral fluxes takes place within the microtopography of polygonal tundra. The long-term summer storage (precipitation minus evapotranspiration) from 1958-2011 indicates a reasonably balance on the polygonal tundra with an average surplus of 5 mm, but it is also characterized by high interannual variability due to precipitation input. During negative water balance years where evapotranspiration exceeds precipitation, shallower water bodies dry out. The extent of wetlands and water bodies will shift with changes in vertical water fluxes as well as permafrost warming and thaw. Thus, water bodies can serve as sentinels of environmental change and we present applicable remote-sensing observations and upscaling methods
14084446 Bolton, W. R. (International Arctic Research Center, Fairbanks, AK); Busey, R.; Hinzman, L. D. and Peckham, S. D. Simulation of water and land-surface feedbacks in a polygonal tundra environment [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0541, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Arctic, including Alaska, is currently experiencing an unprecedented degree of environmental change. Increases in both the mean annual surface temperature and precipitation have been observed. The combination of the recent increase in air temperature and precipitation have led to "unstable" or "warm" permafrost conditions. This warm and unstable permafrost condition is particularly sensitive to changes in both the surface energy and water balances. The observed climatic changes are expected to continue into the next century. As such, most of the current or expected changes (related to climate, permafrost, and vegetation distributions) will be experienced in areas underlain with warm, unstable permafrost. Themokarst topography forms whenever ice-rice permafrost thaws and the ground subsides into the resulting voids. Extensive areas of active thermokarst activity are currently being observed in these warm, unstable permafrost environments. The important processes involved with thermokarsting include surface ponding, surface subsidence, changes in drainage patterns and related erosion. In this study, we will present results from the ERODE (URL: http://csdms.colorado.edu/wiki/Model:Erode ) model in selected areas of the Department of Energy Next Generation Ecosystem Experiments (NGEE Arctic) project field site, located near Barrow, Alaska. The area selected for simulation is located in a polygonal tundra landscape with varying degrees of thermokarst degradation. The goal of this modeling study is to better understand and quantify the development of thermokarst features in the polygonal tundra environment, emphasizing the resulting feedbacks and connections between hydrologic processes and a dynamic surface topography. This unique application of a landscape evolution model may provide valuable information related to the rates and spatial extent of thermokarst development in response to degrading permafrost.
14088757 Chernykh, D. (Russian Academy of Sciences, Pacific Oceanological Institute, Vladivostok, Russian Federation); Shakhova, N. E.; Semiletov, I. P.; Yusupov, V.; Salomatin, A.; Kosmach, D. and Meluzov, A. Temporal variability of methane fluxes in the coastal methane hot spot on the East Siberian Arctic shelf [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0861, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Among Arctic reservoirs, subsea permafrost, hydrates, and associated methane (CH4) deposits are the most worrisome due to high heat transfer from rapidly warming shallow Arctic seas. Destabilization of subsea permafrost results in increasing permeability for gaseous CH4 long preserved in seabed deposits within and beneath permafrost. This process manifests as extensive CH4 ebullition, driving significantly elevated CH4 aqueous concentrations. To investigate the temporal variability of bubble-induced fluxes and document bubble-borne CH4 releases from the study area, we conducted a sonar survey in the coastal area of the Laptev Sea in April 2012. Backscattering cross-sections of the bubbles emitted from 39 seeps were recorded, using a portable single-beam sonar mounted at the edge of a hole made in fast ice. Bubbles were also recorded using a submerged autonomous vehicle equipped with a high-speed, high-resolution digital video camera, and were observed visually through 1-day-old ice. Calibration of sonar data was performed in-situ using a gas tank deployed to the sea floor that emitted gas at known rates. Winter data showed high variability of bubble-induced fluxes in the study area, deviating towards higher rates observed in this area in summer.
14084437 Cuo, L. (Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Beijing, China); Zhao, L. and Zhou, B. The influence of frozen soil change on water balance in the upper Yellow River Basin, China [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0532, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Yellow River supports 30% of China's population and 13% of China's total cultivated area. About 35% of the Yellow River discharge comes from the upper Yellow River Basin. Seasonally frozen, continuous and isolated permafrost soils coexist and cover the entire upper Yellow River Basin. The spatial distribution of various frozen soils is primarily determined by the elevation in the basin. Since the past five decades, air temperature has increased by a rate of 0.03 C/year in the upper Yellow River Basin. Many studies reported the conversions of continuous to isolated permafrost soil, permafrost soil to seasonally frozen soil and the thickening of the active layer due to rising temperature in the basin. However, very few studies reported the impact of the change of frozen soil on the water balance in the basin. In this study, the Variable Infiltration Capacity (VIC) model is applied in the upper Yellow River Basin to study the change of frozen soil and its impact on the water balance. Soil temperature and soil liquid content measured up to 3 m below ground surface at a number of sites in the upper Yellow River Basin and the surroundings are used to evaluate the model simulation. Streamflow is also calibrated and validated using historical streamflow records. The validated VIC model is then used to investigate the frozen soil change and the impact of the change on water balance terms including surface runoff, baseflow, evapotranspiration, soil water content, and streamflow in the basin.
14084447 Daanen, R. P. (Alaska Division of Geological and Geophysical Surveys, Fairbanks, AK); Darrow, M. M. and Hubbard, T. Frozen debris lobe stability, a function of thermal and hydrological processes [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0542, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Frozen debris lobes (FDL) are mass wasting hill slope features found in a region of continuous permafrost in the south-central Brooks Range, near Wiseman, AK. Permafrost temperatures vary with landscape position and elevation but are relatively mild at -1.3 C in the Dietrich River valley. FDL-A, one of the most prominent features due to its movement rate, size and proximity to the Dalton Highway, moves as a flow mainly during summer months, and sliding within a shear zone from 20.2 to 22.8 meters below the lobe surface occurs year round. During drilling we observed the presence of artesian groundwater at various depths near mid-slope in the center line of FDL-A. Artesian water found in the boring may be associated with shear planes in the frozen sediment. In addition, cracks are ubiquitous on the surface, which may be linked to FDL-A's movement and are a likely pathway for liquid water to enter permafrost where it builds liquid water pressure. In this presentation we discuss the physics associated with the observation of liquid water in frozen ground and its implications for potential geologic hazards of this and other FDL's along the Dalton Highway. We also show ground thermal data for the past year on FDL-A. This analysis indicates that there is a relationship between thermal and hydrological processes in permafrost hill slope terrain, and therefore climate change is a crucial factor in the dynamics of FDL's.
14088759 Epstein, H. E. (University of Virginia, Charlottesville, VA); Frost, G. V.; Walker, D. A. and Matyshak, G. Feedbacks between tall shrubland development and active layer temperatures in northwest Siberian Arctic tundra [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC21D-0866, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Permafrost soils are a globally significant carbon store, but changes in permafrost thermal regime observed in recent decades across much of the Arctic suggest that permafrost carbon balance is likely to change with continued climate warming. Critical to changes in permafrost carbon balance in a warmer world, however, are feedbacks between changes in the composition and density of surface vegetation, and the thermal state of permafrost. Shrub expansion has been widely observed in the northwest Siberian Low Arctic, but the magnitude and direction of shrub-induced impacts to permafrost temperature and stability remain poorly understood. Here we evaluate changes to active layer properties and thermal regime that occur during tall shrubland development (shrubs > 1.5 m height) within a northwest Siberian landscape dominated by well-developed, small-scale patterned ground features (e.g., non-sorted circles). We measured the annual time-series of soil temperature at 5 cm and 20 cm depth, and the structural attributes of vegetation at patterned-ground microsites across four stages of tall shrubland development: low-growing tundra lacking erect shrubs, newly-developed shrublands, mature shrublands, and paludified shrublands. Mean summer soil temperatures declined with increasing shrub cover and moss thickness, but winter soil temperatures increased with shrub development. Shrubland development strongly attenuated cryoturbation, promoting the establishment of complete vegetation cover and the development of a continuous organic mat. Increased vegetation cover, in turn, led to further reduced cryoturbation and an aggrading permafrost table. These observations indicate that tall shrub expansion that is now occurring in patterned-ground landscapes of the northwest Siberian Arctic may buffer permafrost from atmospheric warming, and increase carbon storage in these systems at least in the short term.
14084444 Heikoop, J. M. (Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos, NM); Newman, B. D.; Hudak, M.; Gard, M.; Altmann, G.; Throckmorton, H. and Wilson, C. J. Deployment of indicator of reduction in soils (IRIS) probes in Arctic drained thaw lake basins and drainages; time integrated signals of soil saturation and redox [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0539, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Climate driven warming and degradation of permafrost may lead to changes in the hydrology of low gradient regions like the North Slope of Alaska. Hydrologic changes will affect the saturation and redox state of soils in drained thaw lake basins (DTLBs), interlake areas, and associated drainages. These changes are being investigated at the Barrow Environmental Observatory (BEO) and surroundings as part of the Next Generation Ecosystem Experiment - Arctic project. As a complement to traditional redox and aqueous chemistry measurements, the use of indicator of reduction in soils (IRIS) probes is being assessed as a simple and cost-effective way to monitor redox changes. The probes consist of PVC sheets coated with a ferrihydrite paint. Under reducing conditions iron on these probes will partially dissolve. The amount of dissolution can be quantified by image analysis and related in a semi-quantitative fashion to redox conditions in the soils. IRIS probes have been successfully utilized in numerous temperate settings to demonstrate, for example, the presence of reducing soils for wetlands delineation. Test probes were installed in saturated soils for 48 hours in July, 2013. After 48 hours, minor reductive dissolution of ferrihydrite was observed. No sulfide precipitation was noted. As such, probes were installed in quadruplicate at 14 locations representing primarily outlet drainages from different-aged DTLBs and interlake areas. In each case, the probes were installed to refusal at the frost table within the active layer overlying the permafrost. IRIS probes were deployed adjacent to arrays of rhizon samplers used for soil pore water sampling so that time-integrated IRIS probe results can be compared to chemical results (a snapshot in time) obtained at the beginning and end of the monitoring period (probes will be extracted in September). Image analysis will employ LANL's GENIE technology. Field measurements of ferrous iron in water samples showed significant redox variation both between locations and with depth at each location. Values were lowest in surface waters (as low as zero mg/L) and were generally higher in soil pore water with values up to approximately 7 mg/L. Correlations between percentage iron removal from the IRIS probes and ferrous iron and other redox sensitive species will be presented. If correlations are significant, redox couples (ammonia/nitrate, Fe(II)/Fe(III), sulfide/sulfate) will be used to estimate Eh and to develop an empirical relationship for the use of IRIS probes in the BEO and surrounding environs.
14084448 Lessels, Jason S. (University of Aberdeen, School of Geosciences, Aberdeen, United Kingdom); Tetzlaff, D.; Carey, S. K. and Soulsby, C. Keeping it simple; a conceptual model of DOC dynamics in a subarctic alpine catchment [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0544, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Understanding hydrological processes in subarctic alpine catchments characterised with discontinuous permafrost is important in order to understand carbon exports. Subarctic catchments have large storages of carbon in organic and permafrost soils. Active layer depth is one of the largest controlling factors of the release of dissolved organic carbon (DOC) due to its control on runoff pathways. Therefore, any change of this depth will affect the amount of DOC mobilised from these catchments. Simple low parameterised conceptual models offer the ability to characterise hydrological processes and linked DOC dynamics without introducing many of the uncertainties linked to high parameterised models. Lumped models can also be used to identify sources of DOC within catchments. Here, we investigate hydrological sources, flow pathways and consequently DOC dynamics in the Granger Basin, Canada, a subarctic alpine catchment using data collected from 2001 to 2008. The catchment is distinguished by aspect dependant discontinuous permafrost and seasonal frost, compounded further by differences in soil and vegetation types. Applying a simple low parameterised conceptual model allowed identification of the dominant flow paths of the main hydrological response units. The results showed that it was necessary to include active layer dynamics combined with aspect to represent the hydrological and DOC dynamics. The model provides information on the effect of climatic conditions on DOC releases. By identifying the key flow paths and relating these to spring freshet DOC exports over multiple years it is possible to gain an insight of the how climatic changes might affect hydrological processes within subarctic catchments.
14084436 Roux, N. (Université de Versailles Saint-Quentin-en-Yvelines, Versailles, France); Costard, F. and Grenier, C. F. Experimental and numerical simulations of heat transfers between flowing water and a horizontal frozen porous medium [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0531, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In permafrost-affected regions, hydrological changes due to global warming are still under investigation. But yet, we can already foresee from recent studies that for example, the variability and intensity of surface/subsurface flow are likely to be affected by permafrost degradation. And the feedback induced by such changes on permafrost degradation is still not clearly assessed. Of particular interest are lake and river-taliks. A talik is a permanently unfrozen zone that lies below rivers or lake. They should play a key role in these interactions given that they are the only paths for groundwater flow in permafrost regions. Thus heat transfers on a regional scale are potentially influenced by groundwater circulation. The aim of our study is therefore to investigate the evolution of river taliks. We developed a multidisciplinary approach coupling field investigation, experimental studies in a cold room and numerical modeling. In Central Yakutia, Siberia, where permafrost is continuous, we recently installed instruments to monitor ground temperature and water pressure in a river talik between two thermokarst lakes. We present here the coupling of numerical modeling and laboratory experiments in order to look after the main parameters controlling river-talik installation. In a cold room at IDES, where a metric scale channel is filled with sand as a porous medium, we are able to control air, water and permafrost temperature, but also water flow, so that we can test various parameter sets for a miniaturized river. These results are confronted with a numerical model developed at the LSCE with Cast3m (www-cast3m.cea.fr), that couples heat and water transfer. In particular, expressions for river-talik heat exchange terms are investigated. A further step will come in the near future with results from field investigation providing the full complexity of a natural system. Keywords: Talik, River, Numerical Modeling, Cold Room, Permafrost.
14084443 Rushlow, C. R. (Idaho State University, Pocatello, ID) and Godsey, S. Arctic hillslope hydrologic response to changing water storage conditions [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0538, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Solute transport from terrestrial to aquatic environments depends on dynamics of water storage and flux. In the arctic, these dynamics are related to changes in permafrost and hydrological conditions that vary with climate across multiple scales. In order to predict the continued trajectory of arctic landscape and ecosystem evolution, observed changes to the hydrologic regime and riverine nutrient fluxes require properly scaled, mechanistic explanations. We address this issue at the hillslope scale by quantifying hydrologic response to changing storage as part of a collaborative effort to understand the coupled hydrology and biogeochemistry of arctic hillslopes. Hillslopes underlain by continuous permafrost experience gradual, summer-season increases in potential water storage through active layer thaw, as well as stochastic changes in available water storage as soil moisture conditions change due to storm events, evapotranspiration, and subsurface flow. Preferential flowpaths called water tracks are ubiquitous features draining arctic hillslopes and are the focus of our study. We predict that water track hydrologic response to precipitation is a function of snowmelt or storm characteristics and available storage. We hypothesize that the ratio of runoff to precipitation will decrease as available storage increases, whether due to the seasonal increase in active layer thaw, or an extended dry period. Intensive snow and thaw depth surveys on a water track on the hillslopes of the Upper Kuparuk River watershed in northern Alaska during May to June 2013 reveal that snow persisted one week longer in a water track than the adjacent hillslope, and thus active layer thaw initiated earlier on the adjacent hillslope. Despite this earlier thaw timing, thaw depth in the water track exceeded that on the non-track hillslope within five days of being uncovered. Thaw, and thus subsurface storage, in water tracks remained greater than the rest of the hillslope for at least the subsequent two months. Deeper thaw coupled with a slight topographic depression in the water tracks relative to the adjacent hillslopes generates a hydraulic gradient that directed water not only downslope, but also across slope into the water tracks. We expected that steeper hydraulic gradients across slope and into water tracks would increase hillslope soil water contributions and increase the specific conductivity of water flowing through the water track. We also expect hillslope contributions to scale with water track catchment characteristics such as drainage area and slope. We test these hypotheses by monitoring water table fluctuations in gridded wells on the hillslope and in our six intensive study sites throughout the summer. Our results provide direct evidence that active layer thaw and the timing and amount of precipitation are important controls on water and solute flux from arctic hillslopes. Depending on the magnitude of climate-induced changes to these controls, there will likely be important consequences for downslope ecosystems.
14088780 Shakhova, N. E. (University of Alaska, Fairbanks, International Arctic Research Center, Fairbanks, AK); Semiletov, I. P.; Sergienko, V.; Lobkovsky, L. I.; Dmitrevsky, N.; Salyuk, A.; Yusupov, V.; Salomatin, A.; Karnaukh, V.; Chernykh, D.; Kosmach, D.; Ananiev, R.; Meluzov, A.; Nicolsky, D. and Panteleev, G. New result on methane emissions from the East Siberian Arctic Shelf [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract GC22D-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Methane release from thawing Arctic permafrost is one of the few carbon-climate mechanisms that could change projected climate forcing substantially in this century. Venting of methane to the atmosphere in the East Siberian Arctic Shelf, the world's largest yet shallowest shelf, was recently shown to be ubiquitous. Here we report results of multi-year investigations performed in the coastal East Siberian Arctic Shelf (ESAS), where invasion of relatively warm seawater occurred most recently. Observational data and simulation of the warming effect of seawater on subsea permafrost suggest that disintegrating subsea permafrost allows formation of migration pathways for methane bubbles released from the sea floor. Sonar data collected in the coastal area and in the mid-outer shelf area together with data, obtained using high-resolution high-speed video camera, enabled area-weighted methane fluxes to be estimated. New factors controlling spatial and temporal variability of methane fluxes on the ESAS were found. In the outer shelf, it was shown that methane releases from the seabed via strong flare-like ebullition that produces fluxes much greater than on the shallow shelf, where largely frozen sediments restrict fluxes. The coastward progression of thawing subsea permafrost in a warming Arctic could potentially result in a significant increase in methane emissions from the East Siberian Arctic Shelf.
14084445 Skurikhin, A. N. (Los Alamos National Laboratory, Los Alamos, NM); Gangodagamage, C.; Rowland, J. C. and Wilson, C. J. Recognition and characterization of networks of water bodies in the Arctic ice-wedge polygonal tundra using high-resolution satellite imagery [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0540, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Arctic lowland landscapes underlain by permafrost are often characterized by polygon-like patterns such as ice-wedge polygons outlined by networks of ice wedges and complemented with polygon rims, troughs, shallow ponds and thermokarst lakes. Polygonal patterns and corresponding features are relatively easy to recognize in high spatial resolution satellite imagery by a human, but their automated recognition is challenging due to the variability in their spectral appearance, the irregularity of individual trough spacing and orientation within the patterns, and a lack of unique spectral response attributable to troughs with widths commonly between 1 m and 2 m. Accurate identification of fine scale elements of ice-wedge polygonal tundra is important as their imprecise recognition may bias estimates of water, heat and carbon fluxes in large-scale climate models. Our focus is on the problem of identification of Arctic polygonal tundra fine-scale landscape elements (as small as 1 m - 2 m width). The challenge of the considered problem is that while large water bodies (e.g. lakes and rivers) can be recognized based on spectral response, reliable recognition of troughs is more difficult. Troughs do not have unique spectral signature, their appearance is noisy (edges are not strong), their width is small, and they often form connected networks with ponds and lakes, and thus they have overlapping spectral response with other water bodies and surrounding non-water bodies. We present a semi-automated approach to identify and classify Arctic polygonal tundra landscape components across the range of spatial scales, such as troughs, ponds, river- and lake-like objects, using high spatial resolution satellite imagery. The novelty of the approach lies in: (1) the combined use of segmentation and shape-based classification to identify a broad range of water bodies, including troughs, and (2) the use of high-resolution WorldView-2 satellite imagery (with resolution of 0.6 m) for this identification. The approach starts by segmenting water bodies from an image, which are then categorized using shape-based classification. Segmentation uses combination of pan sharpened multispectral bands and is based on the active contours without edges technique. The segmentation is robust to noise and can detect objects with weak boundaries that is important for extraction of troughs. We then categorize the segmented regions via shape based classification. Because segmentation accuracy is the main factor impacting the quality of the shape-based classification, for segmentation accuracy assessment we created reference image using WorldView-2 satellite image of ice-wedge polygonal tundra. Reference image contained manually labelled image regions which cover components of drainage networks, such as troughs, ponds, rivers and lakes. The evaluation has shown that the approach provides a good accuracy of segmentation and reasonable classification results. The overall accuracy of the segmentation is approximately 95%, the segmentation user's and producer's accuracies are approximately 92% and 97% respectively.
14084439 Wellman, T. P. (U. S. Geological Survey, Colorado Water Science Center, Lakewood, CO); Minsley, B. J.; Voss, C. I. and Walvoord, M. A. Understanding response times and groundwater flow dynamics of thaw zone (talik) evolution below lakes in the Yukon Flats, Alaska, USA [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0534, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In cold regions, hydrologic systems possess seasonal and perennial ice-free zones (taliks) within areas of permafrost that control and are enhanced by groundwater flow. Simulation of talik development that follows lake formation in watersheds modeled after those in the Yukon Flats of interior Alaska (USA) provides insight on the coupled interaction between groundwater flow and ice distribution. The SUTRA groundwater simulator with freeze-thaw physics is used to examine the effect of climate, lake size, and lake-groundwater relations on talik formation. Considering a range of these factors, simulated times for a through-going sub-lake talik to form through 90 m of permafrost range from ~200 to >1,000 years (vertical thaw rates <0.1-0.5 m yr-1). Seasonal temperature cycles along lake margins impact supra-permafrost flow and late-stage cryologic processes. Warmer climate accelerates complete permafrost thaw and enhances seasonal flow within the supra-permafrost layer. Prior to open talik formation, sub-lake permafrost thaw is dominated by heat conduction. When hydraulic conditions induce upward or downward flow between the lake and sub-permafrost aquifer, thaw rates are greatly increased. The complexity of ground-ice and water-flow interplay, together with anticipated warming in the arctic, underscores the utility of coupled groundwater-energy transport models in evaluating hydrologic systems impacted by permafrost.
14084573 Lin Guoqing (University of Chinese Academy of Sciences, Beijing, China); Guo Huadong; Li Xinwu and Zhang Lu. Research on the temporal-spatial changes of near-surface soil freeze/thaw cycles in China based on sadiometer: in 35th international symposium on Remote sensing of environment (ISRSE35) (Guo Huadong, editor; et al.), IOP Conference Series. Earth and Environmental Science, 17(1), Paper no. 012142, illus. incl. sketch maps, 5 ref., 2014. Meeting: 35th international symposium on Remote sensing of environment, April 22-26, 2013, Beijing, China.
Near-surface soil freeze-thaw cycles (NSC) would have dramatic influences on hydrologic processes, ecosystem and engineering operations. Passive microwave remote sensing (PMRS) has been a powerful tool for detecting the changes of NSC. The research on NSC based on large-scale and long-time series PMRS data is still rare. In this research, we used the decision tree to extract daily soil freeze/thaw states derived from Special Sensor Microwave/Imager (SSM/I) data from 1988 to 2008. 7-day moving average method was employed to extract the yearly area-averaged frozen days, freeze/thaw onset date of each pixel and frozen pixels from 1988 to 2008. Through analysis of the results above, we found that about 3/4 of the land surface experienced the NSC every year, and less than 4% was always in frozen states which mainly distributed in snow mountains of Qinghai-Tibet Plateau. The changes of NSC in most part of China were seasonal variations, and changed significantly during a year. The general trends of these changes are later freeze onset dates, earlier thaw onset dates, fewer freeze days and longer growing season. Our research would have contributed to understanding near-surface earth systems and extreme environmental events such as the dust emission in semi-arid and arid regions of East Asia. Copyright Published under licence by IOP Publishing Ltd
14084449 Newman, B. D. (Los Alamos National Laboratory, Earth and Environmental Sciences Division, Los Alamos, NM); Throckmorton, H.; Heikoop, J. M.; Altmann, G.; Cohen, L. R.; Gard, M.; Hudak, M.; Perkins, G. and Wilson, C. J. Using deuterium and Oxygen-18 to understand multi-scale hydrology of an Arctic landscape near Barrow, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C53A-0545, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The hydrology of Arctic landscapes is driven by multiple water sources including rainfall, snowmelt, and melting subsurface ice. Geomorphologic controls are also important at small scales where patterned ground affects surface/subsurface water connections and mixing in the active layer. Larger scale features such as drained thaw lake basins and river/stream drainage channels integrate the smaller scale hydrologic systems and can indicate dominant sources/processes which need to be better understood for large scale modeling of linked Arctic water/carbon systems. This presentation discusses the use of deuterium and oxygen-18 stable isotope analyses of water samples at the patterned ground/drained thaw lake basin/ drainage channel scales to identify and quantify water source contributions and understand how small scale hydrological variations are transferred to larger scale systems. We conducted multi-scale synoptic sampling for stable isotopes in July and September, 2013 near Barrow, Alaska as part of the DOE Office of Science Next Generation Ecosystem Experiment (NGEE-Arctic) project. Surface waters, shallow subsurface water (<10 cm), and deeper subsurface water (at the frost line) were sampled to evaluate lateral and vertical distributions of the stable isotopes and their hydrological implications. We also collected a series of precipitation and surface water samples with time from the melt period in June through active layer development into September. These isotope data will help define how contributions from the various sources change over time.
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14084903 Hu, K.; Chen, Z. and Issler, D. R. Determination of geothermal gradient from borehole temperature and permafrost base for exploration wells in the Beaufort-Mackenzie Basin: Open-File Report - Geological Survey of Canada, Rep. No. 6957, 23 p., illus. incl. tables, strat. cols., 32 ref., 2014.
Geothermal gradient is a useful parameter for constraining models of heat flow and petroleum generation in sedimentary basins. This report documents geothermal gradient values for the exploration wells that were used to construct a geothermal gradient map for the Beaufort-Mackenzie Basin. First-order, linear geothermal gradients were calculated for 259 Beaufort-Mackenzie petroleum exploration wells using subsurface temperature data obtained during well testing and logging. Geothermal gradients were determined by applying a least-square fit to the deep temperature data with the requirement that they intersect the mapped base of permafrost at an assumed temperature of 0 °C. Geothermal gradient values were quality-assessed based on the quality and quantity of the individual temperature points used for the calculations and the quality of the fit to the data as represented by the coefficient of determination. Results are displayed graphically as plots of temperature versus depth with respect to fitted linear geothermal gradients for specific well locations. Examples are used to illustrate some anomalous temperature data that have been excluded from the calculation of geothermal gradient. For example, anomalously low DST temperature values in gas zones can be attributed to the Joule-Thomson effect related to gas expansion caused by the pressure drop that accompanies flow. Calculated geothermal gradients vary from approximately 15 °C/km to 48 °C/km across the Beaufort-Mackenzie Basin, and a large fraction of the basin is characterized by typical sedimentary basin geothermal gradients of 25 °C/km to 35 °C/km (> 200 wells).
14091523 Pelletier, B. R. and Medioli, B. E., compilers. Environmental atlas of the Beaufort coastlands: Open-File Report - Geological Survey of Canada, Rep. No. 7619, 271 p., illus. incl. block diags.; environmental geology maps; biogeographic maps; geologic maps, 4 ref., 2014. Supercedes Environmental atlas of the Beaufort Coastlands, 2000. Maps at scales of 1:7,500,000; 1:6,000,000; 1:4,000,000; 1:3,000,000; and 1:2,000,000.
The Beaufort Coastlands, lying adjacent to the southeastern Beaufort Sea, include the northern basin of the Mackenzie River drainage area. These lands are home to more than 7500 people, most of whom are aboriginal residents. Natural conditions, particularly the climate, seriously affect the livelihood of these Arctic dwellers in both a beneficial and calamitous manner. For example, fair conditions can introduce a bountiful wildlife harvest everywhere, but a harsh climate can forestall both land and marine migrations and interfere with hunting activities. This latter event may produce a low yield of much-needed animal resources. Reports on climate warming are based on observations of a shrinking volume of sea ice, and the drilling records and instrument readings that show a deepening summer thaw of permafrost. Several years of continuous thermistor records, during the last two decades of the 20th century, fully attest to these warming phenomena. These signs of change are not catastrophic at present, nor is the debate on their origin entirely resolved. The period of time in which the warming effect is taking place, as well as its projected length and intensity, are also unknown. In the matter of slope stability, human livelihoods and wildlife habitats can be adversely affected. Therefore it is essential that many aspects of the terrain such as slope failure, coastal processes involving erosion, coastal retreat, and weather elements including precipitation, air temperatures and wind variables be monitored daily and monthly. To be most useful in monitoring exercises, hazardous natural events and changes to the environment must be recorded concurrently. Wildlife on land, marine mammals at sea and on the ice, and the fisheries and their harvests are the entities that must be included in these environmental studies because of their essential role in the welfare of aboriginal people, as well as their ecological relationships. More than four million birds visit the area each year for purposes of migratory staging, nesting and feeding. These activities occur along the coastal zone and the lower waterways that empty into the Beaufort Sea, mainly where wetlands, sandbars, inlets, headlands and cliffs provide habitats for avian existence. The entire community of birds must also be considered in plans designed to protect both inland and coastal living niches. It is essential that contingency planning be continued, or introduced in regions that must be protected. This Atlas is designed to serve as a background for such studies that will be beneficial for the occupants and visiting users of this varied suite of habitats. The infrastructure of the Coastlands must be maintained, expanded and protected due to the growing population. Such necessities as transportation and communications corridors must undergo a similar protective attention in order that the safety and security of the region is maintained. Roads, cable routes and fuel transportation lines all require safe rights-of-way; therefore, to address these potential exigencies and the demand for utilities, the need for safe routes are included in the overall hazards-avoidance plans. These practices will require a cadre of professional and technical specialists, and a pool of workers prepared to perform assignments as required. Such a work force will require considerable background information, some of which is provided in this Atlas.
14084927 Williamson, M. C.; Percival, J. B.; Behnia, P.; Harris, J. R.; Peterson, R. C.; Froome, J.; Fenwick, L.; Rainbird, R. H.; Bédard, J. H.; McNeil, R. J.; Day, S. J.; Kingsbury, C. G.; Grunsky, E.; McCurdy, Martin W.; Sheperd, J.; Hillary, E. M. and Buller, G. Environmental and economic impact of oxide-sulphide gossans, Northwest Territories and Nunavut: Open-File Report - Geological Survey of Canada, Rep. No. 7486, 10 p. 1 sheet, illus. incl. tables, 20 ref., 2014. Includes 1 poster.
The poster presents an overview of the objectives and preliminary results of the Geological Survey of Canada's Arctic Gossans activity over a 2-year period from April 2011 to December 2013. The poster was presented at a GSC manager's retreat held in September 2013 as a means to communicate preliminary results and collect feedback prior to project closure in March 2014. This report describes the scientific contributions of participants and collaborators in each part of the study: remote predictive mapping, mineralogy, geochemistry and stream sediment sampling for heavy mineral separations and geochemical analyses. Natural sulphide-rich gossans located in the Canadian Arctic constitute first order economic targets, and are often detected using Earth Observation data. A case in point is the High Lake Cu-Zn sulphide deposit in Nunavut, originally discovered in the 1950s by recognition of kilometer-scale gossans. At High Lake, sulphide-rich mounds are located in intensely fractured bedrock or glacial deposits and form local topographic highs (Petch, 2005). The naturally-occurring alteration zones and acidic lakes are clearly visible on Google Earth(Copyright) (67.37972, -110.84361). The mineralogy and geochemistry of these gossans are indicative of a complex acid rock generation process in which freeze-thaw cycles and chemical weathering ensure a continuous degradation of sulfide-rich rocks, and expose reactive gossanous soil. Based on these observations and the results of previous field campaigns in Nunavut, the following scientific hypothesis was formulated: Arctic gossans constitute analogues of how mine waste will behave in a permafrost environment. They are natural laboratories that record the processes leading to potentially acid generating mine tailings and mine waste rock in a permafrost environment, such as oxidation, metal recycling, deposition, sorting and burial. The following research objectives were proposed as a preamble to test this hypothesis: 1. Locate oxide-sulphide gossans using remote predictive mapping (RPM) techniques. 2. Measure the spectral signatures of surficial materials at key locations to improve the accuracy of remote predictive maps. 3. Map and sample surface materials of alteration zones and host rocks. 4. Determine the stratigraphy, mineralogy, and geochemistry of deposits to document facies and origin. 5. Integrate the results from 1-4 with stream sediment geochemical data.
14085238 Weary, David J. (U. S. Geological Survey) and Doctor, Daniel H. Karst in the United States; a digital map compilation and database: Open-File Report - U. S. Geological Survey, Rep. No. OF 2014-1156, 23 p., illus. incl. geol. sketch maps, 25 ref., 2014.
This report describes new digital maps delineating areas of the United States, including Puerto Rico and the U.S. Virgin Islands, having karst or the potential for development of karst and pseudokarst. These maps show areas underlain by soluble rocks and also by volcanic rocks, sedimentary deposits, and permafrost that have potential for karst or pseudokarst development. All 50 States contain rocks with potential for karst development, and about 18 percent of their area is underlain by soluble rocks having karst or the potential for development of karst features. The areas of soluble rocks shown are based primarily on selection from State geologic maps of rock units containing significant amounts of carbonate or evaporite minerals. Areas underlain by soluble rocks are further classified by general climate setting, degree of induration, and degree of exposure. Areas having potential for volcanic pseudokarst are those underlain chiefly by basaltic-flow rocks no older than Miocene in age. Areas with potential for pseudokarst features in sedimentary rocks are in relatively unconsolidated rocks from which pseudokarst features, such as piping caves, have been reported. Areas having potential for development of thermokarst features, mapped exclusively in Alaska, contain permafrost in relatively thick surficial deposits containing ground ice. This report includes a GIS database with links from the map unit polygons to online geologic unit descriptions.
14084948 Duchesne, C.; Riseborough, D. W. and Smith, S. L. Air and near surface ground temperatures, indices and summary statistics from 1993 to 2012 for the Mackenzie Valley Corridor, Northwest Territories: Open-File Report - Geological Survey of Canada, Rep. No. 7392, 91 p., illus. incl. tables, 2014. This publication supercedes Geological Survey of Canada - Open-File Report, No. 7392, 2013.
Since the early 1990s the Geological Survey of Canada has maintained a network of air and ground surface temperature monitoring sites along a transect in the Mackenzie corridor stretching from the outer Mackenzie Delta to northern Alberta. Data collected from these sites have been utilized to investigate the relationship between air and ground surface temperature for a range of terrain, vegetation and climatic conditions throughout the region. This report presents the data collected up to 2012.
14084892 Konopczak, A. M.; Manson, G. K. and Couture, N. J. Variability of coastal change along the western Yukon coast: Open-File Report - Geological Survey of Canada, Rep. No. 7516, 81 p., illus. incl. tables, 100 ref., 2014.
Because the Yukon coast along the Beaufort Sea has the highest ground ice contents in the Canadian Arctic and, in addition, faces the direction of most effective storms, this section of coast is considered to be highly vulnerable to the effects of climate change. In order to gain insight into the regional coastal dynamics, a quantification of coastal change was undertaken that allowed the determination of spatial and temporal variability of coastal change along a 35 km long section of coast, stretching from Komakuk to the international border. Shorelines from several years between 1951 and 2009 were digitized from georeferenced aerial photographs and an ortho-rectified SPOT image. Shoreline change statistics were subsequently calculated using the Digital Shoreline Analysis System (DSAS) extension for Esri ArcGIS. Theodolite and real-time kinematic GPS data that was collected during several surveys between 1991 and 2012 at two Geological Survey of Canada (GSC) monitoring sites (Border site and Komakuk site) were analysed to provide higher temporal resolution of coastal change for the last two decades. Additionally, the field survey data enabled an assessment to be made of the contribution of geomorphic variables (i.e. beach slope, beach width, cliff slope, absolute cliff height, relative cliff height) towards explaining changes of coastal erosion. According to the findings, the mean annual erosion along the western Yukon coast has been -1.2±0.4 m/a over the entire period of study, with the rates decreasing through time from -1.4±0.6 m/a between 1951 and 1972, to -1.2±0.5 m/a between 1972 and 2009. However, site specific investigations show that there are differences in the mean erosion rates and in temporal trends. To the west at the Border site, the mean annual erosion rate is -1.3±0.3 m/a, and the rates have recently accelerated, while at Komakuk in the east of the study area, the mean annual erosion rate is -0.9±0.2 m/a, with the rates decelerating over time. A comparison of these findings to erosion rates from the Alaskan Beaufort Sea coast indicates that there is a general spatial pattern of decreasing erosion rates from the west to the east. The quantified erosion rates also enabled the calculation of mean annual land loss between 1951 and 2009, which amounted to 4.5 ha/a. An analysis of the influence of shore profile parameters on mean annual erosion rates showed a statistically significant correlation between beach widths and erosion rates (r=0.84) at the Border site. There is also a strong but insignificant correlation between absolute cliff heights and erosion rates at the Border, but no correlations of shore profile parameters with erosion could be distinguished for the Komakuk site.
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14084882 Wolfe, S. A. and Kerr, D. E. Surficial geology, Yellowknife area, Northwest Territories, parts of NTS 85-J/7, NTS 85-J/8, NTS 85-J/9 and NTS 85-J/10: Geological Survey of Canada, Canadian Geoscience Map, Geological Survey of Canada, Ottawa, ON, Canada, Rep. No. 183, 1 sheet (French sum.), illus. incl. glacial geology map, 1:25,000, 7 ref., 2014. ISBN: 978-1-100-23415-1.
Yellowknife Bay was covered by the Laurentide Ice Sheet, with generally southwestward ice flow, during the Late Wisconsinan glaciation until about 10,000 BP. With ice retreat, Glacial Lake McConnell inundated the area, which was replaced by ancestral Great Slave Lake as water levels declined. Surficial geology includes widely-exposed bedrock, and a dominance of fine-grained sediments within low-lying areas deposited within deep glaciolacustrine and shallow post-glacial lake settings. Other sediments include extensive subaqueous outwash deposits of sand and gravel, re-sorted at the surface by wave-action. Wave-washed bedrock is also common, with occasional perched boulders on bedrock and little if any exposed till. Vegetation consists mainly of open to dense forests of black spruce, jack pine, and paper birch mixed with marshes, fens and peat bogs in low-lying areas. Permafrost is extensively discontinuous in the area, occurring within most organic deposits as well as alluvial and glaciolacustrine sediments.
14084873 St-Onge, D. A. and Kerr, D. E. Reconnaissance surficial geology, MacAlpine Lake, south half, Nunavut, NTS 66-L: Geological Survey of Canada, Canadian Geoscience Map, Geological Survey of Canada, Ottawa, ON, Canada, Rep. No. 142, 1 sheet (French sum.), glacial geology map, 1:125,000, 2014. ISBN: 978-1-100-22358-2. Preliminary edition.
Preliminary surficial geology studies, through aerial photograph interpretation and limited legacy data, were undertaken in the south half of the MacAlpine Lake map area to provide an improved understanding of distribution and nature of surficial sediments, and regional glacial history. Widespread streamlined till, hummocky till with kettle lakes and till veneer which may exhibit small transverse ridges locally, are common across the map area. Some tills are dissected by north-northwestward trending glaciofluvial corridors consisting of eskers, ice-contact sediments, and locally zones of scoured bedrock and lags of till veneer. Isolated glacial lakes of variable extent were formed by ponding of meltwater, and their sediments are now characterized by shallow thermokarst lakes. In the northwest map area, a large moraine complex formed perpendicular to ice flow. It consists of till, major moraine ridges, and glaciofluvial outwash sediments forming part of the western segment of a significant end moraine system referred to as the MacAlpine Moraine. Drumlins and crag-and-tails record a regional north-northwestward ice flow during the last glaciation. Active eolian activity can occur adjacent to rivers which have reworked and deposited alluvial sediments.
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