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15029660 Stepanova, V. A. (University of Toulouse, Toulouse, France); Pokrovsky, Oleg S.; Viers, J.; Mironycheva-Tokareva, N. P.; Kosykh, N. P. and Vishnyakova, E. K. Elemental composition of peat profiles in western Siberia; effect of the micro-landscape, latitude position and permafrost coverage: Applied Geochemistry, 53, p. 53-70, illus. incl. 3 tables, sketch map, 65 ref., February 2015. Includes appendices.
The concentrations of major and trace elements in the organic layer of peat soils across a 1800-km latitude profile of western Siberia were measured within various dominating ecosystems to evaluate the effect of landscape, latitude position and permafrost coverage on the peat chemical composition. In this study, peat core samples were collected every 10 cm along the entire length of the column, down to 3-4 m until the mineral horizon was reached. The peat samples were analyzed for major and trace elements using an ICP-MS technique following full acid digestion in a microwave oven. Depending on their concentration pattern along the peat column, several groups of elements were distinguished according to their general physico-chemical properties, mobility in soils, affinity to organic matter and plant biomass. Within similar ecosystems across various climate zones, there was a relatively weak variation in the TE concentration in the upper organic layer (green and brown parts of sphagnum mosses) with the latitude position. Within the intrinsic variability of the TE concentration over the peat column, the effects of climate, latitude position, and landscape location were not significantly pronounced. In different landscapes of the middle taiga, the peat columns collected in the fen zone, the low and mature forest, the ridge and the hollow did not demonstrate a statistically significant difference in most major and trace element concentrations over the full depth of the peat column. In live (green) parts and dead (brown) parts of sphagnum mosses from this climate zone, the concentrations of Mn, P, Ca and Cu decreased significantly with increasing moss net primary production (NPP) at various habitats, whereas the other elements exhibited no link with the NPP trends. The Al- and mineral horizon-normalized peat concentration profiles, allowing removal of the occasional contamination by the underlying mineral substrate and atmospheric dust, demonstrated a homogeneous distribution of TEs along the peat column among various climate zones in the non-permafrost regions but significantly non-conservative behavior in the discontinuous permafrost site. The peat deposits in the northern part of western Siberia potentially have very high release of metals to the surface waters and the riverine systems, depending on the persistence of the ongoing permafrost thaw and the increase in the thickness of the active layer. Abstract Copyright (2015) Elsevier, B.V.
DOI: 10.1016/j.apgeochem.2014.12.004
15029381 Hu Guanglu (Lanzhou Jiaotong University, School of Environmental and Municipal Engineering, Lanzhou, China); Fang Hongbing; Liu Guimin; Zhao Lin; Wu Tonghua; Li Ren and Wu Xiaodong. Soil carbon and nitrogen in the active layers of the permafrost regions in the Three Rivers' headstream: Environmental Earth Sciences, 72(12), p. 5113-5122, illus. incl. 2 tables, geol. sketch map, 42 ref., December 2014.
The pedogenesis, soil organic carbon (SOC), soil inorganic carbon (SIC), hot water-soluble organic carbon (WSOC) and total nitrogen (TN) of the active layers were examined beneath four typical vegetation communities in the permafrost regions in the Three Rivers' Headstream region in the Qinghai-Tibetan Plateau. In all soil areas, except for in the steppe, the SOC and TN showed rapidly decreasing trends with increasing depth. The highest SOC, WSOC and TN contents were found in the wet meadow, with contents in the eluviate layer being 180.9, 40.2 and 10.9 g kg-1, respectively. In the steppe, the average SOC, WSOC and TN at 180 cm depth were 6.2, 0.67 and 0.59 g kg-1, respectively. The SIC contents showed increasing trends with increasing depth in the soils of the steppe community. The correlation analysis suggested that the moisture and fine particle fractions positively correlated to SOC, TN and WSOC, while bulk density and pH negatively correlated to SOC, TN and WSOC. The SOC and TN were significantly related to bulk density. The SIC was positively correlated with pH but negatively correlated with SOC, TN and WSOC. The C/N ratios were negatively correlated with pH while positively correlated with SOC, TN and fine soil particles. The results suggest that the SOC in the wet meadow soils in the permafrost regions of Qinghai-Tibetan have the largest potential contributions to the emissions of greenhouse gases and cause future global warming. Copyright 2014 Springer-Verlag Berlin Heidelberg
DOI: 10.1007/s12665-014-3382-7
15027902 Scapozza, Cristian (Scuola Universitaria Professionale della Scizzera Italiana (SUPSI), Istituto di Scienze della Terra, Canobbio, Switzerland) and Laigre, Laetitia. The contribution of electrical resistivity tomography (ERT) in alpine dynamics geomorphology; case studies from the Swiss Alps: Géomorphologie: Relief, Processus, Environnement, 2014(1), p. 27-42 (French sum.), illus. incl. sects., sketch maps, 64 ref., March 2014.
The Electrical Resistivity Tomography (ERT) is a method based on the study of the capacity of the subsurface to resist to an electrical current. The data processing based on forward and inverse modelling process allows obtaining tomographies of the electrical resistivities distribution in the ground. This helps to determine the nature of the subsurface, its rough porosity, the presence of water and/or ice and thus to characterise the environments of deposition. Three study cases were chosen in the Swiss Alps to illustrate the potentialities of this method for studying landforms in mountain dynamic environments: the first one concerns the study of permafrost distribution in a high altitude talus slope in the Valais Alps; the second one analyses the architecture of fluvial deposits in the Rhone River flood-plain and the last one considers the geometry of the Cimadera landslide located in the Ticino Canton. Through these three study cases, some specific aspects concerning both the prospecting strategy of complex and heterogeneous landforms and the interpretation, namely modelling based on conceptual models, are highlighted and lead to formulate some recommendations when using this method.
15028169 Ahumada, A. L. (Fundación Miguel Lillo, Instituto de Geología de Cuaternario y Paleoclimas, San Miguel de Tucuman, Argentina); Páez, S. V. and Ibáñez Palacios, G. P. Los glaciares de escombros en la sierra de Aconquija, Argentina [The rock glaciers of the Aconquija Range, Argentina]: Acta Geológica Lilloana, 25(1-2), p. 49-68 (English sum.), illus. incl. 3 tables, sketch map, 60 ref., 2013.
An inventory of rock glaciers in the Aconquija Range, Argentina, is presented here. 246 intact rock glaciers (area: 16.46 km2) and 16 debris-covered glaciers (area: 1.17 km2) have been recognized in three major basins and 15 sub-basins of the studied area, covering a total of 17.63 km2. Most of the intact rock glaciers are located on the eastern slope of the Aconquija Range. Their fronts are mainly exposed to the south, showing a strong dependence on solar radiation. The lower limit of mountain permafrost in the Aconquija Range is marked by the occurrence of intact rock glaciers at 4000±200 meters above sea level. The average annual temperature [2°C] at this height would indicate permafrost of azonal type.
15029376 Ghobadi, M. H. (Bu-Ali Sina University, Department of Geology, Hamedan, Iran) and Torabi-Kaveh, M. Assessing the potential for deterioration of limestones forming Taq-e Bostan monuments under freeze-thaw weathering and karst development: Environmental Earth Sciences, 72(12), p. 5035-5047, illus. incl. 3 tables, geol. sketch map, 47 ref., December 2014.
One of the most famous cultural heritage sites in Iran is the Taq-e Bostan world heritage site (northeast of Kermanshah city). This site includes three monuments that all have been carved on limestone. Limestone is sensitive to dissolution and freeze-thaw weathering. Hence, to assess the deterioration of the limestone, field studies and a number of laboratory tests were performed. During the field survey, types of karren forming a group of karstic surface features were observed. These features have made uneven rock surfaces. Formation of the karren near the monuments can be considered as a serious threat. In another part of this article, some index properties, such as weight loss, porosity, Brazilian tensile strength and point load index, were determined for the two series of rock samples in fresh and freeze-thaw conditions. Based on the results, the percentage of weight loss and porosity changes in the tested samples was low. It was found that the index properties of rocks treated with freeze-thaw decrease in varying levels with respect to initial values. The results showed that these variations are due to the deterioration of calcite cement filling microcracks of the rocks in the first place and increase in the porosity of the rocks after recurrent freezing and thawing in the second place. Statistical analyses were developed for predicting the percentage loss values in the index properties after freeze-thaw cycles. There were statistically direct strong relationships between the porosity and the weight loss parameters with the number of freeze-thaw cycles (exponential function with R 2 = 0.94 and linear function with R 2 = 0.97, respectively). In addition, there were inverse linear relationships between Brazilian tensile strength and point load index with the number of freeze-thaw cycles (R 2 = 0.96 and R 2 = 0.93, respectively). On the basis of the obtained results, the monument stones are at risk of deterioration, and it is imperative to take protective treatment measures in this regard. The authors have proposed some physical and chemical preservation methods for the protection of the monuments. Copyright 2014 Springer-Verlag Berlin Heidelberg
DOI: 10.1007/s12665-014-3373-8
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15027504 ElMasri, B. (University of Illinois, Atmospheric Sciences, Urbana-Champaign, IL); Barman, R. and Jain, A. K. The interaction between biogeophysical and biogeochemical processes and their feedback on permafrost soil carbon stocks [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51L-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Our current understanding of the full suite of processes and their responses to recent warming in terrestrial high-latitudes are far from complete. While continued research on development of more detailed Earth system models (ESMs) is essential to understand the interactions and feedbacks between vegetation, soils and climate change in the Northern high latitudes (NHL), one of the major challenges is the treatment of the biophysical and biogeochemical processes and feedback in the ESM and their impact on soil organic carbon. We used a land surface model, the Integrated Science Assessment Model (ISAM), which coupled carbon-nitrogen biogeochemical and energy and hydrology biogeophysical processes, to investigate the effects of feedbacks between the biogeochemical and biogeophysical processes on the model estimated soil organic carbon (SOC) for the NHL permafrost region. We not only focused on recent improvement in the ISAM biogeophysical processes that are deemed important for the high latitude soils/snow; such as deep soil column, modulation of soil thermal and hydrological properties, wind compaction of snow, and depth hoar formation; on permafrost SOC, but also biogeochemical processes; such as dynamic phenology and root distribution, litter carbon decomposition rates and nitrogen amount remaining; on soil biogeochemistry. We selected multiple sites representative of different high latitude biomes to calibrate and evaluate the model. We then carried out several ISAM model simulations to study the effects of feedbacks between biogeochemical and biogeophysical processes on SOC. Our model analysis shows that including the biogeophysical processes alone could increase modeled Northern high-latitude permafrost carbon by about 30% compared to measurements. Accounting for the biogeochmical processes further improve the NHL soil carbon. This study demonstrates that improvements in biogeophysical or biogeochemical processes alone does not help to improve the modeled SOC, instead we emphasis on the importance of biogeophysical and biophysical processes and feedbacks between them in modeling permafrost carbon stocks.
15027495 Heim, B. (Alfred Wegener Institute, Periglacial Research, Potsdam, Germany); Bartsch, A.; Elger, K. K.; Rinke, A.; Matthes, H.; Zhou, X.; Klehmet, K.; Buchhorn, M.; Soliman, A. S. and Duguay, C. R. DUE Permafrost; a circumpolar remote sensing service for permafrost; evaluation case studies and intercomparison with regional climate model simulations [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0393, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The objective of the ESA Data User Element DUE Permafrost project (URL: https://www.ipf.tuwien.ac.at/permafrost/) was to establish a Remote Sensing Service for permafrost applications. Permafrost has been addressed as one of the Essential Climate Variables (ECVs) in the Global Climate Observing System (GCOS). Permafrost is a subground phenomenon but Earth Observation can provide permafrost-related indicators and geophysical parameters used in modelling and monitoring. Climate and permafrost modelers as well as field investigators are associated users including the International Permafrost Association (IPA). URL: http://www.page21.eu/ The ESA DUE Permafrost project (2009-2012) developed a suite of remote sensing products indicative for the subsurface phenomenon permafrost: Land Surface Temperature (LST), Surface Soil Moisture (SSM), Surface Frozen and Thawed State (Freeze/Thaw), Terrain, Land Cover, and Surface Water. Snow parameters (Snow Extent and Snow Water Equivalent) are being developed through the DUE GlobSnow project (Global Snow Monitoring for Climate Research, 2008-2011). The final DUE Permafrost remote sensing products cover the years 2007 to 2011 with a circumpolar coverage (north of 50°N). The products were released in 2012, to be used to analyze the temporal dynamics and map the spatial patterns of permafrost indicators. Further information is available at www.ipf.tuwien.ac.at/permafrost. The remote sensing service also supports the FP7 funded project PAGE21 - Changing Permafrost in the Arctic and its Global Effects in the 21st Century, URL: http://www.page21.eu/. The primary programme providing various ground data for the evaluation is the Global Terrestrial Network for Permafrost (GTN-P) initiated by the International Permafrost Association (IPA). Ground data ranges from active layer- and snow depths, to air-, ground-, and borehole temperature data as well as soil moisture measurements and the description of landform and vegetation. The involvement of scientific stakeholders and the IPA, and the ongoing evaluation of the remote sensing derived products make the DUE Permafrost products accepted by the scientific community. The Helmholtz Climate Initiative REKLIM (Regionale KlimaAnderungen/Regional climate change) is a climate research program where regional observations and process studies are coupled with model simulations (URL: http://www.reklim.de/en/home/). The ESA DUE Permafrost User workshops initiated the use of the DUE time series within the REKLIM framework for inter-comparison experiments in order to assist the evaluation of calculated parameter fields of models. Within the REKLIM framework we spatio-temporally compare the geophysical surface parameters simulated by regional climate models with the spatio-temporal variability of Earth Observational remote sensing products. Earth Observational remote sensing products are: DUE Permafrost, DUE GlobSnow (URL: http://www.globsnow.info) and the MODIS albedo product (MOD 43). We show intercomparison substudies on simulated fields of surface temperature and ground frozen, non-frozen state simulated by the regional climate models HIRHAM for the circumpolar domain and COSMO-CLM for Central Siberia.
15027516 Saleska, S. R. (University of Arizona, Ecology & Evolutionary Biology, Tucson, AZ); McCalley, C. K.; Woodcroft, B. J.; Hodgkins, S. B.; Mondav, R.; Wehr, R. A.; Kim, E.; Crill, P. M.; Rich, V. I.; Chanton, J. and Tyson, G. W. Shifting microbial communities dynamically mediate the effect of permafrost thaw on isotopic composition of atmospheric methane [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B54B-07, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Increasing methane (CH4) emission from thawing permafrost is expected to increase atmospheric methane concentrations and constitute an important positive feedback to climate change. However, the dependence of this feedback on ecological changes in the microbial communities that produce CH4 is largely unknown. To study the effects of microbial community ecology on isotopic composition of atmospheric CH4, we combined high frequency measurements of the carbon isotopic signatures of CH4 emissions with microbial community profiling via 16S rRNA amplicon sequencing along a permafrost thaw gradient in northern Sweden. We found that different stages of thaw were associated with different microbial communities and isotopic compositions. Early thaw microbial communities were dominated by methanogens with hydrogenotrophic metabolism, emitting isotopically light CH4 (d13C ~ -80ppm), while communities in fully thawed environments contained a greater proportion of methanogens utilizing acetoclastic pathways, and emitted CH4 that was less depleted in 13C (d13C ~ -65ppm). To assess the potential global implications of the observed thaw-induced changes in microbial metabolism and associated CH4 isotope dynamics, we used a simple box model of atmospheric mixing. We found that if thaw-induced patterns in CH4 isotopes generally match our observations, then CH4 emissions from thawing permafrost will likely produce shifts in the isotopic composition of global atmospheric CH4. These changes will be more negative than those typically assumed by current atmospheric model-based inversion studies, which assume that the carbon isotopic signature of biogenic CH4 emissions is fixed at -60 or -65ppm. This isotopic difference would lead to a 2-4 fold overestimation of the amount of CH4 released from thawing permafrost and a corresponding underestimation of emissions from non-wetland sources. We conclude that microbial community ecology may be a significant but neglected mechanism in the effect of permafrost thaw on atmospheric composition.
15027502 Sasai, T. (Nagoya University, Nagoya, Japan); Yamada, D.; Aiba, K.; Setoyama, Y.; Hayashi, M.; Kotani, A.; Ohta, T.; Murakami, K.; Kato, S.; Saigusa, N. and Nasahara, K. Analyzing a relationship between permafrost and carbon cycle over Siberia using the diagnostic-type biosphere model [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51I-0410, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
A climate filed in high latitude region is largely affected by global warming, and the cryosphere specific environmental changes (e.g., temperature increases and permafrost melting) would drastically change water and energy cycles in terrestrial biosphere via plant and soil microbe activities. We estimated NEP and the exposed permafrost carbon over Siberia using the biosphere model, BEAMS to understand an influence of the permafrost thawing on the terrestrial carbon cycle. The cryosphere unique process introduced into BEAMS are 1) multi-layer soil water and energy transport with soil water freezing and thawing, 2) soil respiration restriction by physical buffering effect of snow carbon pool, 3) increment of soil carbon exposed by permafrost thawing, and 4) microbe biomass dependence on carbon decomposition.The model validation demonstrated that GPP, NEP, soil water contents and temperature estimations have a good agreement with ground observations. We simulated carbon, water and energy cycles over Siberia region at 10km grid resolution using satellite observations from 2001 to 2010. As a result, the Siberian ecosystem played a role of carbon sink (+266.5 TgC/year), and recently had been growing larger sink (+6.0TgC/year). In the eastern Siberia, the active layer thickness was increased by global warming, leading that the total amount of exposed permafrost carbon is 3.3 ~ 8.4 times larger than cumulative NEP for 10 years (0.27TgC/years). In future, the Siberian ecosystem might shift to the large carbon source by releasing the carbon to atmosphere.
15027499 Busey, R. (University of Alaska, Fairbanks, AK); Bolton, W. R.; Cherry, J. E. and Hinzman, L. D. Characterization of an active thermal erosion site, Caribou Creek, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0403, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The goal of this project is to estimate volume loss of soil over time from this site, provide parameterizations on erodibility of ice rich permafrost and serve as a baseline for future landscape evolution simulations. Located in the zone of discontinuous permafrost, the interior region of Alaska (USA) is home to a large quantity of warm, unstable permafrost that is both high in ice content and has soil temperatures near the freezing point. Much of this permafrost maintains a frozen state despite the general warming air temperature trend in the region due to the presence of a thick insulating organic mat and a dense root network in the upper sub-surface of the soil column. At a rapidly evolving thermo-erosion site, located within the Caribou-Poker Creeks Research Watershed (part of the Bonanza Creek LTER) near Chatanika, Alaska (N65.140, W147.570), the protective organic layer and associated plants were disturbed by an adjacent traditional use trail and the shifting of a groundwater spring. These triggers have led to rapid geomorphological change on the landscape as the soil thaws and sediment is transported into the creek at the valley bottom. Since 2006 (approximately the time of initiation), the thermal erosion has grown to 170 meters length, 3 meters max depth, and 15 meters maximum width. This research combines several data sets: DGPS survey, imagery from an extremely low altitude pole-based remote sensing (3 to 5 meters above ground level), and imagery from an Unmanned Aerial System (UAS) at about 60m altitude.
15027496 Farquharson, L. M. (University of Alaska Fairbanks, Department of Geology, Fairbanks, AK); Grosse, G.; Romanovsky, V. E.; Jones, B. M.; Arp, C. D. and McGuire, A. D. Spatial distribution of thermokarst landforms across Arctic Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0394, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Arctic Alaska is characterized by widespread past and present thaw of ice rich permafrost and subsequent thermokarst development. Variations in ice content and distribution, and topography across Arctic Alaska result in thermokarst landform diversity. Thermokarst causes a number of biogeochemical and ecological shifts that include changes in soil carbon dynamics, nutrient cycling, vegetation composition, wildlife habitat, and fresh water availability. Ongoing climate change may lead to an increase in thermokarst landscape features. Thus, a better understanding of the current temporal and spatial dynamics of thermokarst is needed in order to project its future dynamics. Understanding how vulnerable Arctic Alaska is to future thermokarst development is critical for resource management, industry development, and subsistence hunting. We focused on the distribution of thermokarst landforms among ten study sites aligned with the NSF CALON (Towards a Circum-Arctic Lakes Observation Network) project in Arctic Alaska. Sites represent diverse substrates including eolian silt, eolian sand, marine sand, deltaic, and marine silt. We conducted thermokarst landform mapping and spatial and morphometric analyses using high-resolution aerial photography, an interferometric synthetic aperture radar derived digital elevation model (IfSAR DEM), and hydrographic layers from the National Land Cover Database derived from Landsat-7. Non-lake thermokarst landforms were visually mapped and hand digitized using aerial photographs and the IfSAR DEM. Initial results show thermokarst forms are most prevalent in marine silt areas with up to 99% of study areas affected by thermokarst activity. Eolian sand areas are the least thermokarst affected (mean of 57%). Drained thermokarst lake basins, thermokarst lakes, and areas affected by thermokarst pit formation were the dominant thermokarst landforms, covering up to 70%, 54%, and 8% of the landscape. The number of overlapping lake and basin generations was used as a proxy for landscape dynamics over the Holocene. Thermokarst was most advanced in marine silt and marine sand, where up to five overlapping generations of thermokarst lake basins were identified. We also used depth of drained thermokarst lake basins relative to adjacent uplands as a proxy for maximum subsidence and an indicator for average ground ice content. Subsidence is greatest within areas of eolian silt (mean of 20 m). In contrast, marine silts exhibit a mean subsidence of 4.5 m. This difference can be attributed in part to the large size and depth of syngenetic ice wedges in eolian silt, compared to shallower epigenetic ice wedges in marine silts. Our preliminary data show that thermokarst landform distribution, the extent of thermokarst activity, and the depth of maximum subsidence vary across Arctic Alaska and that surficial geology is an important controlling factor. We plan to use these data to parameterize and validate the Alaska Thermokarst Model currently being developed as a component of the Integrated Ecosystem Model for Alaska and Northwest Canada.
15027501 Gibbs, A. (U. S. Geological Survey, Santa Cruz, CA); Richmond, B. M.; Palaseanu, M.; Erikson, L. H.; Jones, B. M. and Brock, J. C. Remote sensing of the Arctic Coast of Alaska using airborne lidar data [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0406, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
As part of a U.S. Geological Survey assessment of coastal change hazards, over 11,000 km2 of airborne lidar elevation data were collected along the Arctic coast of Alaska between 2009 and 2012. Data coverage includes the barrier islands and mainland coast between Icy Cape and the U.S.-Canadian border, from the shoreline to ~1.5 km inland. Data coverage extends further inland to around 3 km on the Barrow Peninsula and along the coast of the Teshekpuk Lake Special Area (TLSA) where coastal erosion rates are among the highest in the world (> 18 m/yr). Nominal point density is 1.5 m and vertical accuracy is better than 30 cm. Data were not collected over most river deltas or large embayments, with the exception of Admiralty Bay, Smith Bay (Ikpikpik Delta), Kogru River, and the Fish Creek portion of Colville River delta. The primary use of the lidar data is to establish a modern shoreline position to be used for change analyses with historical shoreline positions. However, the lidar DEM provides a wealth of topographic and intensity data that can be used for morphological mapping of the remote Arctic coast. This is one of the first comprehensive lidar datasets collected in a continuous permafrost environment. Many periglacial landscape features, such as patterned ground, ice-wedge polygons, and thermokarst lakes and former lake basins (recent and relict) are discernible in the dataset. Traditional coastal landscape features including shoreline position, beach width, slope, and bluff height and morphology are also distinct. Here we present an overview of the dataset and an assessment of methodologies developed for characterizing and classifying a variety of landscape features including overall complexity, geometry and morphology of polygonal tundra (polygon spacing, high center vs. low center), coastal bluff morphology (vertical or overhanging, convex vs. concave), drainage patterns and hydrologic connectivity. We also investigate the dataset to estimate offsets between ellipsoid and sea-level elevations, which is necessary for evaluating the vulnerability of the coast to inundation associated with storm surge, sea-level rise, oil spills and other marine-associated hazards.
15027570 Herreid, S. (UAF, Fairbanks, AK) and Pellicciotti, F. A simple D model of supraglacial debris cover evolution [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C22A-06, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Mountain glaciers around the world are covered by some amount of supraglacial debris which alters the glacier melt regime. As glaciers shrink, and permafrost thaws, valley walls previously supported by ice and frozen ground become subject to erosion and rock failure and therefore cause an increase of supraglacial rock deposition. Additionally, sustained negative mass balance favors an increase in englacial debris emergence. While the relative contribution of these two processes is not entirely understood, it has been assumed that debris cover is increasing in association with a warming climate. Change in debris cover extent measured in the Alaska Range, the Swiss Alps and the Nepalese Himalaya support this assumption and show an increase in the percentage of debris covered area. Here we present a simple empirical model for evolving 2D debris covered area using data that is (potentially) easy to obtain: a digital elevation model, satellite derived surface temperature, and geologic maps. We solve independently for valley wall sourced debris deposits and ablation-dominated medial moraine debris sourced both from valley wall detritus buried under accumulated ice and englacial bedrock plucking. Currently, model calibration is required for each rock unit surrounding a glacier. We will use the results from detailed analysis of individual glaciers to gauge the accuracy of more generalized, regional scale solutions.
15027505 Jammet, M. (University of Copenhagen, Department of Geosciences and Natural Resource Management, Center for Permafrost, Copenhagen, Denmark); Friborg, T. and Crill, P. M. Relative importance of lake methane emissions in a subarctic peatland landscape depends on spring ice thaw [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B52B-04, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Lakes and ponds are abundant features of northern landscapes where the presence of permafrost and peat prevents water drainage. Northern lakes have been recently argued to be globally significant emitters of methane (CH4), partially offsetting the vegetation carbon sink. Besides, they are likely to play a role in degrading permafrost landscapes as sites of carbon remineralization from adjacent peatlands. Few studies have been published on Arctic lake CH4 dynamics, and even fewer took an integrative ecosystem approach, comparing vegetated area and open-water system within the same catchment Because of a high temporal and spatial variability, lake-atmosphere CH4 exchanges are notoriously difficult to measure. The eddy covariance (EC) method allows for continuous monitoring and integration of all emissions pathways (ebullition, diffusion, plant-mediated transport). We present here one year of ecosystem-scale data from the Stordalen mire (68°N, 19°E) near Abisko in Northern Sweden, where an eddy covariance system is used in an innovative way to quantify the importance of CH4 emissions from a shallow lake (average depth < 1.5m) in a palsa mire landscape. The EC system is situated so that it measures either a terrestrial fen surface or a lake surface depending on wind direction which, in Stordalen, is dominated by flow from only two directions. During the ice-free season from June to October 2012, fen emissions clearly dominated with a daily CH4 flux that averages 5 times higher than the lake emissions. During Spring thaw in May 2013, we captured a protracted CH4 burst from the lake. The daily rates of emission from the lake at this time were higher than the summer maxima observed from both quadrants. In mid-summer, the lake CH4 emissions were much lower than those from the vegetated quadrant: the lake becomes a significant contributor to landscape CH4 emissions with the addition of the ice thaw period to the annual CH4 budget. A large spring degassing occurred over 15 days with an average efflux of 212 mg.m-2.d-1. After the spring burst, lake fluxes decreased to very low background values. Most likely the ice thaw burst released CH4 which had been stored in the lake, sediments and ice during winter. Such an event was not observed in the vegetated quadrant which displayed a low but continuous efflux during the winter season (average estimated at 30 mg.m-2.d-1). While the fen keeps a connection with the atmosphere during the winter via diffusion through the snow and plant stems, the lake is isolated from the atmosphere during the winter. Spring degassing indicates there are CH4 sources that are active during the cold period which cannot be released before the connection with the atmosphere is re-established. Our main result is consistent with recent subarctic studies indicating the importance of spring thaw to the annual CH4 flux from seasonally ice-covered lakes. However due to very low lake fluxes in summer the fen surfaces release more CH4 on an annual scale.
15027497 Mard Karlsson, J. (, Stockholm, Sweden); Lyon, S. W. and Destouni, G. Thermokarst lake size-distribution across time in northwestern Siberia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0400, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Thermokarst lakes are dependent on permafrost, and changes in thermokarst lake size and number have been reported for ice-rich continuous and discontinuous regions. Thermokarst lakes and wetlands dominate the peat-forming lowlands of the Nadym and Pur River basins in northwestern Siberia, and warming during the last decades has initiated fluctuations in the number and total area of lakes in these basins. Lake size distribution and abundance is important to assess the role of lakes in regional and global biogeochemical processes. In this study we use remote sensing (Landsat images) to help distinguish spatially explicit changes due to permafrost thaw from year 1973, through 1987-1988 to 2007-2009. The results show both increase and decrease in lake area and abundance over time. However, the size-distribution of thermokarst lakes, in the size ranges of our investigation, has not changed as permafrost thaws over the three time periods. The distribution is thus relatively time-invariant with regard to the included lake sizes (mostly >&eq;10ha), which are at the upper size and cutoff end of a possible power law distribution. The latter may extend further over several orders of magnitude of smaller lake sizes that have not been investigated here. However, the distribution time invariance found here persists also when extending the investigated sizes to an order of magnitude smaller lake sizes (down to 1ha lakes) and is important for interpreting the implications of changes in thermokarst lakes in periods of permafrost change.
15027515 Martinez-Cruz, K. C. (University of Alaska Fairbanks, Institute of Northern Engineering, Water and Environmental Research Center, Fairbanks, AK); Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Anthony, P. and Thalasso, F. Aerobic methane oxidation in alaskan lakes along a latitudinal transect [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B54B-05, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Methane (CH4) is the third most important greenhouse gas in the atmosphere, after carbon dioxide and water vapor. Boreal lakes play an important role in the current global warming by contributing as much as 6% of global atmospheric CH4 sources annually. On the other hand, aerobic methane oxidation (methanotrophy) in lake water is a fundamental process in global methane cycling that reduces the amount of CH4 emissions to the atmosphere. Several environmental factors affect aerobic methane oxidation in the water column both directly and indirectly, including concentration of CH4 and O2, temperature and carbon budgets of lakes. We analyzed the potential of aerobic methane oxidation (PMO) rates in incubations of water collected from 30 Alaskan lakes along a north-south transect during winter and summer 2011. Our findings showed an effect of CH4 and O2 concentrations, temperature and yedoma thawing permafrost on PMO activity in the lake water. The highest PMO rates were observed in summer by lakes situated on thawing yedoma permafrost, most of them located in the interior of Alaska. We also estimated that 60-80% of all CH4 produced in Alaskan lakes could be taken up by methanotrophs in the lake water column, showing the significant influence of aerobic methane oxidation of boreal lakes to the global CH4 budget.
15027513 Osman, M. (Augustana College, Department of Geology, Rock Island, IL); Varner, R. K.; Palace, M. W.; Wik, M.; Crill, P. M. and Lang, A. Employing passive acoustics as a temporally precise monologue for constraining ebullitive methane fluxes in warming subarctic lakes [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B53B-0458, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Systematic difficulties in capturing the large spatial and temporal variability of ebullition (bubbling) has promoted a broad range of uncertainty in our understanding of the role of lakes as key emitters of atmospheric methane (CH4). With the projected warming and ongoing thawing of high-latitude frozen peatlands abundant in small lakes and ponds, there is an increasing need for methods that provide high-temporal resolution delineating precisely when and under what circumstances ebullitive fluxes occur. Employing the well-established Minnaert resonance formula as a reliable proxy for bubble volume, we designed a system of passive acoustic hydrophone sensors calibrated to continuously record ebullition from lakes at 160 kbits/sec. We present here the results of three summer field seasons (2011-2013) of acoustic and manual bubble flux measurements from four subarctic lakes situated in discontinuous permafrost regions of northern Sweden and Alaska. Results show trends similar to prior lake measurements in the subarctic. We found wide variation in CH4 concentrations, spanning between 0.10 to 95.16%. Fluxes ranged from 0-279.72 mg CH4 m-2 d-1 and averaged 12.03 mg CH4 m-2 d-1 (n = 401) over the three year period. High resolution time series analysis of our measurements will be compared alongside standard meteorological parameters such as atmospheric pressure, temperature, rainfall, water table, wind speed, and radiative inputs to infer dominant external forcings on ebullition. Radiocarbon and 13C/12C ratios of bubble samples collected from Swedish lakes in July 2013 are to be subsequently analyzed for age, transport, and production mechanisms.
15027509 Townsend-Small, A. (University of Cincinnati, Cincinnati, OH); Hinkel, K. M.; Arp, C. D.; Beck, R. A.; Frey, K. E.; Grosse, G.; Jones, B. M.; Kim, C.; Lenters, J. D. and Liu, H. Variations in methane concentration and isotopic composition in a broad survey of lakes in Arctic Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B53B-0446, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
Increasing methane emissions from thawing permafrost may represent a positive feedback to climate warming. Lakes are hotspots for permafrost thaw in summer due to low albedo, and warm, saturated sediments may mobilize a larger portion of thawed organic carbon as methane versus carbon dioxide than terrestrial soils. Thawing permafrost may also accelerate methane emissions via the release of previously trapped natural gas. As part of the Circumarctic Lakes Observation Network (CALON), we have measured dissolved methane and carbon dioxide concentrations and stable isotope composition of methane (carbon-13 and deuterium) in approximately 65 lakes across a latitudinal and longitudinal gradient in Arctic Alaska, with sampling conducted twice a year (April and August) for the past two years. We have two north-to-south sampling transects, one western transect starting in Barrow, AK and heading south to about 70 degrees N, and the other eastern transect heading south from Teshekpuk Lake to the Toolik Lake area. Methane concentrations were an average of ~500 times higher under ice than in open-water conditions, with average under-ice concentrations of about 25 micromoles per liter versus 50 nanomoles per liter in open water. It was also expected that southern lakes would have higher concentrations of methane in summer, consistent with the observed latitudinal temperature gradient. However, the highest methane concentrations were found in lakes in the western portion of the study domain, with no latitudinal trend. Total dissolved methane concentrations observed in summer 2012 ranged from 10 nanomoles per liter to 121 micromoles per liter in the western transect, and 7 nanomoles per liter to 1 micromole per liter in the eastern transect. Stable isotopic analyses indicated that many of the western transect lakes have thermogenic methane, such as that derived from fossil fuel formations. Longer-term sampling will help to indicate whether climate warming causes an increase in biological methane production and/or accelerates the release of thermogenic methane. We are also seeking collaborations with international partners to expand our sampling beyond Alaska to the rest of the terrestrial Arctic.
15027536 Wong, G. J. (Dartmouth College, Earth Sciences, Hanover, NH); Osterberg, E. C.; Hawley, R. L.; Caughey, S. K.; Courville, Z.; Howley, J.; Lutz, E. and Overly, T. B. Coast-to-interior gradients and recent trends in physical and chemical properties of near-surface snow and firn in northwest Greenland [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C13B-0677, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The Greenland Ice Sheet (GIS), which holds enough ice to raise global sea levels by approximately 7 m, is a major driver of Arctic and global climate. Observations over the past two decades have documented changes including notable increases in ice discharge, significant warming in coastal regions, and expanded areal extent of annual surface melt (e.g., Rignot and Thomas, 2002; Mote, 2007; Hanna and others, 2008). In contrast, observations document little change in temperature or accumulation in the central regions of the ice sheet (Hanna and others, 2008, 2011). The 1120 km-long Greenland Inland Traverse (GrIT), between Thule Air Base in northwest Greenland and Summit Station in central Greenland, is a logistics traverse that follows a nearly identical route taken by Carl Benson and the US Army Snow, Ice and Permafrost Research Establishment (SIPRE) between 1952 and 1955 (Benson, 1962). Observations from the SIPRE and GrIT traverses provide two snapshots of surface conditions across the northwest region of the GIS separated by 56 years. Hawley and others (in review) observe an increase in snow accumulation rates along the GrIT traverse route based on internal reflecting horizons in radar data dated with firn cores, with larger accumulation increases observed in the coastal region near Thule. Here we expand upon the analysis of Hawley and others (in review) by determining coast-to-interior gradients in snow accumulation, density, hardness (Rammsonde), and snow chemistry using samples from 18 snow pits and 3 firn cores collected during the 2010 and 2011 GrIT traverses. Snow pit and firn core samples were analyzed for trace element (23Na, 24Mg, 27Al, 32S, 39K, 44Ca, 47Ti, 51V, 52Cr, 55Mn, 56Fe, 59Co, 63Cu, 66Zn, 75As, 88Sr, 111Cd, 133Cs, 138Ba, 139La, 140Ce, 141Pr, 208Pb, 209Bi, 238U) concentrations and stable water isotope ratios (dD, d18O), and were dated by seasonal oscillations in chemical concentrations and isotope ratios. We compare the GrIT data to those of Benson to determine changes in physical parameters over the past 56 years. Firn cores collected from coastal (2Barrel; 76.9317° N, 63.1467° W) and interior (Galen, 74.4223° N, 39.2943° W; Owen, 72.6° N, 38.5° W) locations along the traverse provide a multi-decadal context to the snow pit snapshots, and allow us to investigate temporal trends in accumulation. Furthermore, we utilize climate reanalysis data to investigate associated changes over the past half-century in surface temperature, atmospheric circulation (e.g., North Atlantic Oscillation) and sea ice extent.
15027498 Gangodagamage, C. (Los Alamos National Laboratory, Los Alamos, NM); Rowland, J. C.; Skurikhin, A. N.; Wilson, C. J.; Brumby, S. P.; Painter, S. L.; Gable, C. W.; Bui, Q.; Short, L. S.; Liljedahl, A.; Hubbard, S. S.; Wainwright, H. M.; Dafflon, B.; Tweedie, C. E.; Kumar, J. and Wullschleger, S. D. Spatial and spectral characterization, mapping, and 3D reconstructing of ice-wedge polygons using high resolution LiDAR data [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51H-0402, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
In landscapes with ice-wedge polygons, fine-scale land surface characterization is critically important because the processes that govern the carbon cycle and hydrological dynamics are controlled by features on the order of a few to tens of meters. To characterize the fine-scale features in polygonal ground in Barrow, Alaska, we use high-resolution LiDAR-derived topographic data (such as elevation, slope, curvature, and a novel "directed distance (DD)" to develop quantitative metrics that allow for the discretization and characterization of polygons (formed by seasonal freeze and thaw processes). First, we used high resolution (0.25 m) LiDAR to show that the high and low centered polygon features exhibit a unique signature in the Fourier power spectrum where the landscape signature on freeze and thaw process (~ 5 to 100 m) is super imposed on the coarse scale fluvial eroded landscape (rudimentary river network) signature. We next convolve LiDAR elevations with multiscale wavelets and objectively choose appropriate scales to map interconnected troughs of high- and low-centered polygons. For the ice wedges where LiDAR surface expressions (troughs) are not well developed, we used a Delaunay triangulation to connect the ice-wedge network and map the topologically connected polygons. This analysis allows us to explore the 3D morphometry of these high- and low-centered polygons and develop a supervised set of ensemble characteristic templates for each polygon type as a function of directed distance (DD). These templates are used to classify the ice-wedge polygon landscape into low-centered polygons with limited troughs, and high- and low-centered polygons with well-developed trough network. We further extend the characteristic templates to polygon ensemble slopes and curvatures as a function of DD and develop a classification scheme for microtopographic features including troughs, rims, elevated ridges, and centers for both high-centered and low-centered polygon. Finally, we show that the developed topographic template curves can be used to synthetically generate 3D model domain polygonal discretizations and characterizations and to predict ice wedge degradation levels--all using commonly available high resolution remotely sensed data where high-resolution LiDAR data is unavailable.
15027560 McGraw, M. (Southeastern Louisiana University, Hammond, LA) and Walker, H. J. Calculating lake morphology in the Colville River delta, Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract C21D-0680, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.
The morphology and surface area of a lake can be determined using simple mathematical formulas. These formulas can be plugged into a Geographic Information System (GIS) and used to calculate the circularity, smoothness, compactness and orientation of a lake or pond in remotely sensed imagery. The calculated output can then be used to differentiate circular lakes from elongated lakes, lakes with smooth shorelines from those with complex shorelines, and lake orientation; such information can then be used to classify and quantify different types of lakes in complex environments such as river deltas. The Colville River delta is located on the North Slope of Arctic Alaska. Previous studies have classified the delta's 230,000+ lakes into five types: 1. thermokarst (thaw) lakes, 2. oriented lakes, 3. perched lakes, 4 channel lakes and 5. ice-wedge polygon ponds. This study uses 2004 aerial photography and 2011 satellite imagery to quantify the different types of lake in the delta.
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