15016945 Bouchard, Frédéric (Institut National de la Recherche Scientifique, Centre Eau Terre Environnement, Quebec, QC, Canada); Francus, Pierre; Pienitz, Reinhard; Laurion, Isabelle and Feyte, Stéphane. Subarctic thermokarst ponds; investigating recent landscape evolution and sediment dynamics in thawed permafrost of northern Québec (Canada): in Environmental change in the Hudson and James Bay region, Canada (Keller, Wendel, editor; et al.), Arctic, Antarctic, and Alpine Research, 46(1), p. 251-271, illus. incl. 6 tables, sketch maps, 85 ref., February 2014. Includes appendix.

Although widely distributed throughout Arctic and subarctic regions, thermokarst ponds and lakes remain relatively unexplored regarding geomorphological changes in their catchments and their internal properties in relation to climate change over the past decades. This study synthesizes recent landscape evolution and modern sedimentology of limnologically diverse thermokarst ponds near southeastern Hudson Bay, Canada. Spatio-temporal analysis of permafrost mounds, thermokarst ponds, and vegetation surface areas over the past five decades revealed that the recent climate-induced decrease of permafrost-affected areas was not primarily compensated by thermokarst pond development, but rather by a remarkable increase in vegetation cover. These changes appeared to be modulated by topographical and hydrological gradients at the study site, which are associated with east-ward increasing thickness of postglacial marine deposits. At a more contemporary timescale, physico-chemical measurements made on sedimenting materials (sediment traps) and freshly deposited lacustrine sediments of selected thermokarst ponds revealed striking differences both among ponds and between the oxic epilimnion and the oxygen-depleted hypolimnion. These findings underscore the major influence of local landscape properties and oxycline development on pond sedimentology and geochemistry, such as the transport of detritic particles and the concentration of redox-sensitive elements.

DOI: 10.1657/1938-4246-46.1.251

15014466 Tananayev, N. I. (Russian Academy of Sciences, Siberian Division, P. Melnikov Permafrost Institute, Yakutsk, Russian Federation). Morfologiya i dinamika beregov krupnykh rek kriolitozony (na primere sredney Leny v rayone Yakutska) [Morphology and dynamics of big river shores in the permafrost zone (central Lena River near Yakutsk, as an example)]: Geomorfologiya, 2014(1), p. 81-92 (English sum.), illus. incl. 3 tables, sketch map, 34 ref., March 2014.

Major features of bank erosion within the middle course of the Lena River are related to the hydrological conditions of flowing water contact with different floodplain levels, and variations in floodplain lithology. Formative discharges of the spring freshet correspond to the frozen sandy strata of the high floodplain banks, thus promoting thermal erosion of the latter. Effectiveness of the thermal erosion increases with the increase in bank height and is highest for high floodplain and terrace levels. Morphology of the banks depends not on the rate of their washing out, but on the influx of the sediments at their base. The volume of eroded bank material exceeds the annual bedload runoff due to the large extent of the eroded bank within the studied Lena River reach.

15013370 Gangodagamage, Chandana (Los Alamos National Laboratory, Los Alamos, NM); Rowland, Joel C.; Hubbard, Susan S.; Brumby, Steven P.; Liljedahl, Anna K.; Wainwright, Haruko; Wilson, Cathy J.; Altmann, Garrett L.; Dafflon, Baptiste; Peterson, John; Ulrich, Craig; Tweedie, Craig E. and Wullschleger, Stan D. Extrapolating active layer thickness measurements across Arctic polygonal terrain using LiDAR and NDVI data sets: Water Resources Research, 50(8), p. 6339-6357, illus. incl. 2 tables, 85 ref., August 2014.

Landscape attributes that vary with microtopography, such as active layer thickness (ALT), are labor intensive and difficult to document effectively through in situ methods at kilometer spatial extents, thus rendering remotely sensed methods desirable. Spatially explicit estimates of ALT can provide critically needed data for parameterization, initialization, and evaluation of Arctic terrestrial models. In this work, we demonstrate a new approach using high-resolution remotely sensed data for estimating centimeter-scale ALT in a 5 km² area of ice-wedge polygon terrain in Barrow, Alaska. We use a simple regression-based, machine learning data-fusion algorithm that uses topographic and spectral metrics derived from multisensor data (LiDAR and WorldView-2) to estimate ALT (2 m spatial resolution) across the study area. Comparison of the ALT estimates with ground-based measurements, indicates the accuracy (r² = 0.76, RMSE ±4.4 cm) of the approach. While it is generally accepted that broad climatic variability associated with increasing air temperature will govern the regional averages of ALT, consistent with prior studies, our findings using high-resolution LiDAR and WorldView-2 data, show that smaller-scale variability in ALT is controlled by local eco-hydro-geomorphic factors. This work demonstrates a path forward for mapping ALT at high spatial resolution and across sufficiently large regions for improved understanding and predictions of coupled dynamics among permafrost, hydrology, and land-surface processes from readily available remote sensing data. Abstract Copyright (2014), . The Authors.

DOI: 10.1002/2013WR014283

15013308 Doran, Peter T. (University of Illinois at Chicago, Department of Earth and Environmental Sciences, Chicago, IL); Kenig, Fabien; Knoepfle, Jennifer Lawson; Mikucki, Jill A. and Berry Lyons, W. Radiocarbon distribution and the effect of legacy in lakes of the McMurdo dry valleys, Antarctica: Limnology and Oceanography, 59(3), p. 811-826, 52 ref., May 2014.

The water of the ice-covered lakes of the McMurdo Dry Valleys is derived primarily from glacial melt streams and to a lesser extent permafrost seeps and subglacial outflow. The result is a mixture of radiocarbon ages that reflect both the end-member water source and the biogeochemical processing of waters as they migrate to the lake-water column. Samples were collected from various locations within perennially ice-covered Antarctic lakes and the streams that feed them, and they were analyzed for radiocarbon abundance of organic and inorganic carbon. Stream gradient and length were shown to affect the degree of equilibration of water with the modern atmosphere prior to entering the lakes. Stream microbial mats assimilate inorganic carbon flowing over them. Seasonal ice-free "moat" water dissolved inorganic carbon (DIC) is largely dependent on the amount of meltwater input from streams (modern) vs. that from direct glaciers input (old). Under the ice cover, ¹⁴C ages of lake-water DIC and organic matter are dependent on lake history, composition, and quantity of particulate matter fallout. Bottom waters of the west lobe of Lake Bonney have a DIC age of » 27,000 ¹⁴C yr before present, which we believe are the most radiocarbon-deficient lake waters on Earth. Comparison of the radiocarbon profiles in the two lobes of Lake Bonney, along with previously published geochemical data, provides a new chronology of the evolution of these two waterbodies and shows that currently deep saline water is being displaced over the sill separating them.

DOI: 10.4319/lo.2014.59.3.0811

15013148 Vaughan, Jessica M. (University of Alberta, Edmonton, AB, Canada); England, John H. and Evans, David J. A. Glaciotectonic deformation and reinterpretation of the Worth Point stratigraphic sequence; Banks Island, NT, Canada: in Quaternary glaciations and sea level change in the Canadian Arctic; special theme in honour of the career of Professor John England (Evans, David J. A., editor; et al.), Quaternary Science Reviews, 91, p. 124-145, illus. incl. sects., sketch map, 91 ref., May 1, 2014.

Hill-hole pairs, comprising an ice-pushed hill and associated source depression, cluster in a belt along the west coast of Banks Island, NT. Ongoing coastal erosion at Worth Point, southwest Banks Island, has exposed a section (6 km long and »30 m high) through an ice-pushed hill that was transported » 2 km from a corresponding source depression to the southeast. The exposed stratigraphic sequence is polydeformed and comprises folded and faulted rafts of Early Cretaceous and Late Tertiary bedrock, a prominent organic raft, Quaternary glacial sediments, and buried glacial ice. Three distinct structural domains can be identified within the stratigraphic sequence that represent proximal to distal deformation in an ice-marginal setting. Complex thrust sequences, interfering fold-sets, brecciated bedrock and widespread shear structures superimposed on this ice-marginally deformed sequence record subsequent deformation in a subglacial shear zone. Analysis of cross-cutting relationships within the stratigraphic sequence combined with OSL dating indicate that the Worth Point hill-hole pair was deformed during two separate glaciotectonic events. Firstly, ice sheet advance constructed the hill-hole pair and glaciotectonized the strata ice-marginally, producing a proximal to distal deformation sequence. A glacioisostatically forced marine transgression resulted in extensive reworking of the strata and the deposition of a glaciomarine diamict. A readvance during this initial stage redeformed the strata in a subglacial shear zone, overprinting complex deformation structures and depositing a glaciotectonite »20 m thick. Outwash channels that incise the subglacially deformed strata record a deglacial marine regression, whereas aggradation of glaciofluvial sand and gravel infilling the channels record a subsequent marine transgression. Secondly, a later, largely non-erosive ice margin overrode Worth Point, deforming only the most surficial units in the section and depositing a capping till. The investigation of the Worth Point stratigraphic sequence provides the first detailed description of the internal architecture of a polydeformed hill-hole pair, and as such provides an insight into the formation and evolution of an enigmatic landform. Notably, the stratigraphic sequence documents ice-marginal and subglacial glaciotectonics in permafrost terrain, as well as regional glacial and relative sea level histories. The reinterpreted stratigraphy fundamentally rejects the long-established paleoenvironmental history of Worth Point that assumed a simple "layer-cake" stratigraphy including the type-site for an organically rich, preglacial interval (Worth Point Fm). Abstract Copyright (2014) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2013.11.005

15016938 Fillion, Marie-Ève (Université Laval, Centre d'Études Nordiques, Quebec City, QC, Canada); Bhiry, Najat and Touazi, Mustapha. Differential development of two palsa fields in a peatland located near Whapmagoostui-Kuujjuuarapik, northern Québec, Canada: in Environmental change in the Hudson and James Bay region, Canada (Keller, Wendel, editor; et al.), Arctic, Antarctic, and Alpine Research, 46(1), p. 40-54, illus. incl. 1 table, sketch maps, 75 ref., February 2014.

Macrofossil analysis of the peat and topographic surveys of two palsa fields (Fields 3 and 4) within a permafrost peatland located in subarctic Quebec was conducted to trace the factors that contributed to their differential development. The two palsa fields are visibly different in terms of their geomorphology, ecology, and hydrology. According to our results, the evolution of the two fields was largely synchronous in terms of the respective trophic conditions. Moreover, the climate certainly played a significant role in the evolution of this ecosystem. For example, the cooling of the Neoglacial period would have favored the ombrotrophication of both sites, whereas the Little Ice Age conditions would have contributed to palsa formation. Despite the synchronous changes within the two fields, significant differences were also noted. These include the rate of peat accumulation, the number of species found in the peat monoliths, and the presence or absence of forest cover during the ombrotrophic phase. The topography of the underlying substrate would also have influenced the hydrological conditions. For example, a light slope toward the northwest engendered a faster trophic impoverishment in Field 4. In addition, streaming water in Field 3 favored the preservation of wet and rich conditions that triggered the following changes: more diverse vegetation, the significant accumulation of peat, and the formation of higher palsas.

DOI: 10.1657/1938-4246-46.1.40

15016937 Holmquist, James R. (University of California at Los Angeles, Department of Ecology and Evolutionary Biology, Los Angeles, CA); MacDonald, Glen M. and Gallego-Sala, Angela. Peatland initiation, carbon accumulation, and 2 ka depth in the James Bay Lowland and adjacent regions: in Environmental change in the Hudson and James Bay region, Canada (Keller, Wendel, editor; et al.), Arctic, Antarctic, and Alpine Research, 46(1), p. 19-39, illus. incl. 6 tables, sketch map, 80 ref., February 2014. Includes appendix.

Peatlands surrounding Hudson and James Bays form the second largest peatland complex in the world and contain major stores of soil carbon (C). This study utilized a transect of eight ombrotrophic peat cores from remote regions of central and northern Ontario to quantify the magnitude and rate of C accumulation since peatland initiation and for the past 2000 calendar years before present (2 ka). These new data were supplemented by 17 millennially resolved chronologies from a literature review covering the Boreal Shield, Hudson Plains, and Taiga Shield bordering Hudson and James Bays. Peatlands initiated in central and northern Ontario by 7.8 ka following deglaciation and isostatic emergence of northern areas to above sea level. Total C accumulated since inception averaged 109.7±(std. dev.) 36.2 kg C m^-2. Approximately 40% of total soil C has accumulated since 2 ka at an average apparent rate of 20.2±6.9 g C m^-2 yr^-1. The 2 ka depths correlate significantly and positively with modern gridded climate estimates for mean annual precipitation, mean annual air temperature, growing degree-days >0°C, and photosynthetically active radiation integrated over days >0°C. There are significantly shallower depths in permafrost peatlands. Vertical peat accumulation was likely constrained by temperature, growing season length, and photosynthetically active radiation over the last 2 ka in the Hudson Bay Lowlands and surrounding regions.

DOI: 10.1657/1938-4246-46.1.19

15016941 McLaughlin, Jim (Ontario Ministry of Natural Resources, Ontario Forest Research Institute, Sault Ste. Marie, ON, Canada) and Webster, Kara. Effects of climate change on peatlands in the far north of Ontario, Canada; a synthesis: in Environmental change in the Hudson and James Bay region, Canada (Keller, Wendel, editor; et al.), Arctic, Antarctic, and Alpine Research, 46(1), p. 84-102, illus. incl. 8 tables, sketch maps, 150 ref., February 2014.

The Hudson Bay Lowlands (HBL) is the largest peatland complex in North America. More than 75% of the HBL occurs in Ontario, where the provincial government mandates that ecosystem carbon storage and sequestration be considered in land-use planning. Accomplishing this task requires identifying carbon indicators and assessing their responses to changing ecosystem processes, such as succession, permafrost thaw, and evapotranspiration (ET). Therefore, we synthesized information on peat carbon indicators and ecosystem process from the literature. Findings indicate that the long-term carbon accumulation, carbon dioxide (CO2) sequestration, peat depth, and peatland age were similar (p>0.10) between dry and wet peatland features. Furthermore, CO₂ sequestration displayed the highest variability and ponds were net CO₂ emitters. Recent carbon accumulation, CH₄ emission, and ET were highest (p<0.01) in wet features, with CH₄ emission displaying wide variation. Increased active layer thickness (105±92 cm per 100 years) in permafrost was the most variable ecosystem process analyzed in this study, while variation in permafrost loss (53±23% per 100 years) was similar to that of carbon accumulation and ET rates. Processes creating wet and pond conditions may increase landscape-scale CO₂ and CH₄ emissions to the atmosphere, weakening peatland carbon sinks. Dry conditions may reduce CH₄ emissions but potentially increase peatland susceptibility to fire. Knowledge of these changes should be useful for climate change vulnerability and adaptation assessments for large landscapes. However, better understanding of variability in CO₂ sequestration, CH₄ emission, and permafrost dynamics is required to design such assessments for small landscapes.

DOI: 10.1657/1938-4246-46.1.84

15012621 Wetterich, Sebastian (Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research, Research Unit Potsdam, Department of Periglacial Research, Potsdam, Germany); Tumskoy, Vladimir; Rudaya, Natalia; Andreev, Andrei A.; Opel, Thomas; Meyer, Hanno; Schirrmeister, Lutz and Hüls, Matthias. Ice Complex formation in Arctic East Siberia during the MIS 3 interstadial: Quaternary Science Reviews, 84, p. 39-55, illus. incl. 2 tables, sketch map, 102 ref., January 15, 2014.

A continuous 15 m long sequence of Ice Complex permafrost (Yedoma) exposed in a thermo-cirque at the southern coast of Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Dmitry Laptev Strait) was studied to reconstruct past landscape and environmental dynamics. The sequence accumulated during the Marine Isotope Stage 3 (MIS3) Interstadial between >49 and 29 ka BP in an ice-wedge polygon. The frozen deposits were cryolithologically described and sampled on a vertical bluff between two ice wedges. According to sedimentological and geochronological data, the section is subdivided into three units which correlate with environmental conditions of the early, middle, and late MIS3 period. Palynological data support this stratification. The stable isotope signature of texture ice in the polygon structure reflects fractionation due to local freeze-thaw processes, while the signature of an approximately 5 m wide and more than 17 m high ice wedge fits very well into the regional stable-water isotope record. Regional climate dynamics during the MIS3 Interstadial and local landscape conditions of the polygonal patterned ground controlled the Ice Complex formation. The sequence presented here completes previously published MIS3 permafrost records in Northeast Siberia. Late Quaternary stadial-interstadial climate variability in arctic West Beringia is preserved at millennial resolution in the Ice Complex. A MIS3 climate optimum was revealed between 48 and 38 ka BP from the Ice Complex on Bol'shoy Lyakhovsky Island. Abstract Copyright (2014) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2013.11.009

15012650 Ballantyne, Colin K. (University of Saint Andrews, School of Geography and Geosciences, St. Andrews, United Kingdom); Sandeman, Graeme F.; Stone, John O. and Wilson, Peter. Rock-slope failure following late Pleistocene deglaciation on tectonically stable mountainous terrain: Quaternary Science Reviews, 86, p. 144-157, illus. incl. 1 table, sketch map, 135 ref., February 15, 2014.

The ages of 31 postglacial rock-slope failures (RSFs) in Scotland and NW Ireland, derived from 89 cosmogenic isotope exposure ages, are employed to analyse the temporal pattern of failure and its relationship to the timing of deglaciation, rates of glacio-isostatic crustal uplift and periods of rapid climate change. RSF ages span almost the whole period since ice-sheet retreat, from 18.2 ± 1.2 ka to 1.7 ± 0.2 ka, or from 17.1 ± 1.0 ka to 1.5 ± 0.1 ka, depending on the production rate used in ¹⁰Be age calculation, but catastrophic failure of rock slopes was ~4.6 times more frequent prior to ~11.7 ka than during the Holocene. 95% of dated RSFs at sites deglaciated during retreat of the last ice sheet occurred within ~5400 years after deglaciation, with peak RSF activity 1600-1700 years after deglaciation. This time lag is inferred to represent (1) stress release initiated by deglacial unloading, leading to (2) time-dependent rock mass strength degradation through progressive failure plane development, and ultimately (3) to either spontaneous kinematic release or failure triggered by some extrinsic mechanism. By contrast, 11 dated RSFs at sites reoccupied by glacier ice during the Younger Dryas Stade (YDS) of ~12.9-11.7 ka exhibit no clear temporal pattern, suggesting that glacial reoccupance during the YDS was ineffective in preconditioning a renewed cycle of enhanced RSF activity. Comparison of timing of individual RSFs with that of deglaciation and rapid warming events at ~14.7 ka and ~11.7 ka suggests that glacial debuttressing, enhanced joint water pressures during deglaciation and thaw of permafrost ice in rock joints could have triggered failure in only a small number of cases. Conversely, the timing of maximum RSF activity following ice-sheet deglaciation corresponds broadly with maximum rates of glacio-isostatic crustal uplift, suggesting that the two are linked by enhanced seismic activity. A seismic failure trigger is consistent with full-slope failure at all sites where failure planes are clearly defined. Our results indicate that numerous RSFs must have occurred in areas that were reoccupied by glacier ice during the YDS, but have not been identified because runout debris was removed by YDS glaciers. More generally, they provide the first reliably-dated body of evidence to support the view that retreat of the last ice sheets in tectonically-stable mountainous terrain initiated a period of enhanced rock slope failure due to deglacial unloading and probably Lateglacial seismic activity, implying that most undated RSFs in such areas are probably of Lateglacial or very early Holocene age. They also demonstrate, however, that a low frequency of RSF activity extended throughout the Holocene. Abstract Copyright (2014) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2013.12.021

15016230 Schleusner, Philipp (Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, Potsdam, Germany); Biskaborn, Boris K.; Kienast, Frank; Wolter, Juliane; Subetto, Dmitry and Diekmann, Bernhard. Basin evolution and palaeoenvironmental variability of the thermokarst Lake El'gene-Kyuele, Arctic Siberia: Boreas, 44(1), p. 216-229, illus. incl. strat. col., 2 tables, sketch map, 83 ref., January 2015.

Thermokarst lakes are a widespread feature of the Arctic tundra, in which highly dynamic processes are closely connected with current and past climate changes. We investigated late Quaternary sediment dynamics, basin and shoreline evolution, and environmental interrelations of Lake El'gene-Kyuele in the NE Siberian Arctic (latitude 71°17'N, longitude 125°34'E). The water-body displays thaw-lake characteristics cutting into both Pleistocene Ice Complex and Holocene alas sediments. Our methods are based on grain size distribution, mineralogical composition, TOC/N ratio, stable carbon isotopes and the analysis of plant macrofossils from a 3.5-m sediment profile at the modern eastern lake shore. Our results show two main sources for sediments in the lake basin: terrigenous diamicton supplied from thermokarst slopes and the lake shore, and lacustrine detritus that has mainly settled in the deep lake basin. The lake and its adjacent thermokarst basin rapidly expanded during the early Holocene. This climatically warmer than today period was characterized by forest or forest tundra vegetation composed of larches, birch trees and shrubs. Woodlands of both the HTM and the Late Pleistocene were affected by fire, which potentially triggered the initiation of thermokarst processes resulting later in lake formation and expansion. The maximum lake depth at the study site and the lowest limnic bioproductivity occurred during the longest time interval of ~7 ka starting in the Holocene Thermal Maximum and lasting throughout the progressively cooler Neoglacial, whereas partial drainage and an extensive shift of the lake shoreline occurred ~0.9 cal. ka BP. Correspondingly, this study discusses different climatic and environmental drivers for the dynamics of a thermokarst basin. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1111/bor.12084

15013147 Evans, David J. A. (Durham University, Department of Geography, Durham, United Kingdom); England, John H.; La Farge, Catherine; Coulthard, Roy D.; Lakeman, Thomas R. and Vaughan, Jessica M. Quaternary geology of the Duck Hawk Bluffs, southwest Banks Island, Arctic Canada; a re-investigation of a critical terrestrial type locality for glacial and interglacial events bordering the Arctic Ocean: in Quaternary glaciations and sea level change in the Canadian Arctic; special theme in honour of the career of Professor John England (Evans, David J. A., editor; et al.), Quaternary Science Reviews, 91, p. 82-123, illus. incl. sect., 1 table, geol. sketch map, 97 ref., May 1, 2014.

Duck Hawk Bluffs, southwest Banks Island, is a primary section (8 km long and 60 m high) in the western Canadian Arctic Archipelago exposing a long record of Quaternary sedimentation adjacent to the Arctic Ocean. A reinvestigation of Duck Hawk Bluffs demonstrates that it is a previously unrecognized thrust-block moraine emplaced from the northeast by Laurentide ice. Previous stratigraphic models of Duck Hawk Bluffs reported a basal unit of preglacial fluvial sand and gravel (Beaufort Fm, forested Arctic), overlain by a succession of three glaciations and at least two interglacials. Our observations dismiss the occurrence of preglacial sediments and amalgamate the entire record into three glacial intervals and one prominent interglacial. The first glacigenic sedimentation is recorded by an ice-contact sandur containing redeposited allochthonous organics previously assigned to the Beaufort Fm. This is overlain by fine-grained sediments with ice wedge pseudomorphs and well-preserved bryophyte assemblages corresponding to an interglacial environment similar to modern. The second glacial interval is recorded by ice-proximal mass flows and marine rhythmites that were glacitectonized when Laurentide ice overrode the site from Amundsen Gulf to the south. Sediments of this interval have been reported to be magnetically reversed (>780 ka). The third interval of glacigenic sedimentation includes glacifluvial sand and gravel recording the arrival of Laurentide ice that overrode the site from the northeast (island interior) depositing a glacitectonite and constructing the thrust block moraine that comprises Duck Hawk Bluffs. Sediments of this interval have been reported to be magnetically normal (<780 ka). The glacitectonite contains a highly deformed melange of pre-existing sediments that were previously assigned to several formally named, marine and interglacial deposits resting in an undeformed sequence. In contrast, the tectonism associated with the thrust block moraine imparted pervasive deformation throughout all underlying units, highlighted by a previously unrecognized raft of Cretaceous bedrock. During this advance, Laurentide ice from the interior of Banks Island coalesced with an ice stream in Amundsen Gulf, depositing the interlobate Sachs Moraine that contains shells as young as »24 cal ka BP (Late Wisconsinan). During deglaciation, meltwater emanating from these separating ice lobes deposited outwash that extended to deglacial marine limit (11 m asl) along the west coast of Banks Island. Our new stratigraphic synthesis fundamentally revises and simplifies the record of past Quaternary environments preserved on southwest Banks Island, which serves as a key terrestrial archive for palaeoenvironmental change. Abstract Copyright (2014) Elsevier, B.V.

DOI: 10.1016/j.quascirev.2014.03.011

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15014838 Hausmann, Helmut (Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria); Krainer, Karl; Brückl, Ewald; Blöschl, G.; Chirico, G. B.; Komma, J.; Illnar, R. and Eipeldauer, S. Sediment quantification and ground water storage in an alpine permafrost catchment [abstr.]: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 35, February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Also published in Third European conference on Permafrost (EUCOP III), Svalbard, Norway, June 13-17, 2010, p. 56, 2010. Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014839 Hausmann, Helmut (Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria); Krainer, Karl; Brückl, Ewald; Chirico, G. B.; Blöschl, G.; Eipeldauer, S.; Illnar, R. and Komma, J. Wie beeinflusst Permafrost den Abfluss? Erste Ergebnisse des Einzugsgebietes Krummgampental, Otztaler Alpen [Is permafrost affected by drainage? Preliminary results from Krummgampen Valley, Otztal Alps] [abstr.]: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 36, February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Also published in GeoAlp, Vol. 7, p. 93-108, 2010. Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014834 Hausmann, Helmut (Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria); Krainer, Karl; Brückl, Ewald; Rogger, M.; Chirico, G. B. and Blöschl, G. Sediment and water storage in an Alpine permafrost catchment area, Krummgampen Valley, Otztal Alps, Austria: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 18-21, 41 ref., February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014833 Hausmann, Helmut (Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria); Krainer, Karl and Brückl, Ewald. Mapping and modelling of permafrost using seismic refraction and ground surface temperatures, Krummgampen Valley, Otztal Alps, Austria: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 13-17, 72 ref., February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014837 Hausmann, Helmut (Vienna University of Technology, Institute of Geodesy and Geophysics, Vienna, Austria); Krainer, Karl; Staudinger, M. and Brückl, Ewald. Continous recording of seismic signals in alpine permafrost [abstr.]: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 34, February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Also published in Geophysical Research Abstracts, Vol. 11, abstract no. EGU2009-10330, 2009. Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014831 Krainer, Karl (University of Innsbruck, Institute for Geology and Paleontology, Innsbruck, Austria) and Hausmann, Helmut, editors. Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report: Austrian Academy of Sciences, Austria, 58 p., illus., February 2013. ISBN: 978-3-7001-7384-7 (International Strategy for Disaster Prevention, final report 2007-2011). Includes appendices; individual papers are cited separately.

The aim of this project is the quantitative assessment of alpine permafrost in a well-defined catchment area, the impact of permafrost on climate warming and the establishment of a hydrological model to understand the associated changes. The multi-disciplinary project combines methods from geology, hydrology, meteorology, geodesy and geophysics to investigate permafrost in unconsolidated sediments and their consequences on the hydrological regime. The appearance of permafrost is indicated by active rock glacier, patterned ground, sorted stripes, outcrops of frozen ground and the high frequency of rock falls. Beside of the previous investigated rock glaciers Reichenkar (Stubai Alps, Tyrol), Kaiserbergtal and Olgrube (Otztal Alps, Tyrol) we selected a study area in the Krummgampen valley (Glockturm-Weiseespitze, Otztal Alps) to investigate the impact of permafrost on the hydrological regime. First we use existing models and geomorphologic mapping to estimate the local permafrost distribution. On this basis we select areas for the seismic mapping and the measurements of ground temperature (BTS). Afterwards we use these field observations to model the lateral and vertical permafrost distribution. To assess the sediment volume and hydrologic relevant parameters we use further geophysical methods. The major aims for the hydrological investigations are as following: (a) Establishment of a numerical stream flow model using the permafrost and sediment distribution maps, (b) Monitoring of relevant meteorological, hydrologic parameters such as discharge, precipitation and temperature, (c) Calibration of the numerical model by the field data.

DOI: 10.1553/ISDR-22s1

15014832 Krainer, Karl (University of Innsbruck, Institute for Geology and Paleontology, Innsbruck, Austria); Kellerer-Pirklbauer, A.; Kaufmann, V.; Lieb, G. K.; Schrott, L. and Hausmann, Helmut. Permafrost research in Austria; history and recent advances: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 5-12, 97 ref., February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014835 Rogger, M. (Vienna University of Technology, Institute for Hydraulic Engineering and Water Resources Management, Vienna, Austria); Chirico, G. B.; Hausmann, Helmut; Krainer, Karl; Brückl, Ewald and Blöschl, G. Impact of mountain permafrost on flow path and runoff response in a high alpine catchment: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 22-27, 82 ref., February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

15014841 Rogger, M. (Vienna University of Technology, Institute for Hydraulic Engineering and Water Resources Management, Vienna, Austria); Hausmann, Helmut; Krainer, Karl; Brückl, Ewald and Blöschl, G. Distributed hydrological modelling in a permafrost catchment; on the value of geophysical information [abstr.]: in Permafrost in Austria; impact of climate change on alpine permafrost and related hydrological effects; final report (Krainer, Karl, editor; et al.), Austrian Academy of Sciences, Austria, p. 38, February 2013. (International Strategy for Disaster Prevention, final report 2007-2011). Also published in Geophysical Research Abstracts, Vol. 15, 2013. Accessed on Oct. 31, 2014.

URL: http://epub.oeaw.ac.at/0xc1aa500e_0x002dc464.pdf

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15014978 Anderson, S. M. (University of New Hampshire, Institute of Earth, Ocean and Space, Durham, NH); Palace, Michael W.; Layne, M.; Varner, Ruth K. and Crill, Patrick M. Species composition at the sub-meter level in discontinuous permafrost in subarctic Sweden [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B41B-0400, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Northern latitudes are experiencing rapid warming. Wetlands underlain by permafrost are particularly vulnerable to warming which results in changes in vegetative cover. Specific species have been associated with greenhouse gas emissions therefore knowledge of species compositional shift allows for the systematic change and quantification of emissions and changes in such emissions. Species composition varies on the sub-meter scale based on topography and other microsite environmental parameters. This complexity and the need to scale vegetation to the landscape level proves vital in our estimation of carbon dioxide (CO2) and methane (CH4) emissions and dynamics. Stordalen Mire (68°21'N, 18°49'E) in Abisko and is located at the edge of discontinuous permafrost zone. This provides a unique opportunity to analyze multiple vegetation communities in a close proximity. To do this, we randomly selected 25 1´1 meter plots that were representative of five major cover types: Semi-wet, wet, hummock, tall graminoid, and tall shrub. We used a quadrat with 64 sub plots and measured areal percent cover for 24 species. We collected ground based remote sensing (RS) at each plot to determine species composition using an ADC-lite (near infrared, red, green) and GoPro (red, blue, green). We normalized each image based on a Teflon white chip placed in each image. Textural analysis was conducted on each image for entropy, angular second momentum, and lacunarity. A logistic regression was developed to examine vegetation cover types and remote sensing parameters. We used a multiple linear regression using forwards stepwise variable selection. We found statistical difference in species composition and diversity indices between vegetation cover types. In addition, we were able to build regression model to significantly estimate vegetation cover type as well as percent cover for specific key vegetative species. This ground-based remote sensing allows for quick quantification of vegetation cover and species and also provides the framework for scaling to satellite image data to estimate species composition and shift on the landscape level. To determine diversity within our plots we calculated species richness and Shannon Index. We found that there were statistically different species composition within each vegetation cover type and also determined which species were indicative for cover type. Our logistical regression was able to significantly classify vegetation cover types based on RS parameters. Our multiple regression analysis indicated Betunla nana (Dwarf Birch) (r²=.48, p=<0.0001) and Sphagnum (r²=0.59, p=<0.0001) were statistically significant with respect to RS parameters. We suggest that ground based remote sensing methods may provide a unique and efficient method to quantify vegetation across the landscape in northern latitude wetlands.

15014969 Chang, Rachel Y. (Harvard University, Cambridge, MA); Karion, Anna; Sweeney, Colm; Henderson, J.; Mountain, M.; Eluszkiewicz, J.; Luus, K. A.; Lin, John C.; Dinardo, S.; Miller, Charles E. and Wofsy, S. C. Constraining estimates of methane emissions from Arctic permafrost regions with CARVE [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B33K-0611, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Permafrost in the Arctic contains large carbon pools that are currently non-labile, but can be released to the atmosphere as polar regions warm. In order to predict future climate scenarios, we need to understand the emissions of these greenhouse gases under varying environmental conditions. This study presents in-situ measurements of methane made on board an aircraft during the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), which sampled over the permafrost regions of Alaska. Using measurements from May to September 2012, seasonal emission rate estimates of methane from tundra are constrained using the Stochastic Time-Inverted Lagrangian Transport model, a Lagrangian particle dispersion model driven by custom polar-WRF fields. Preliminary results suggest that methane emission rates have not greatly increased since the Arctic Boundary Layer Experiment conducted in southwest Alaska in 1988.

15015009 Johnson, Aiden (Montana State University, Bozeman, MT); Stoy, Paul and Ewing, Stephanie A. Quantifying the uncertainty of Landsat tm derived energy balance parameters in the discontinuous permafrost zone; a Monte Carlo approach [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B43C-0534, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

High latitude regions are proving to be highly sensitive to climatic change as indicated by shifts in plant communities and other surface properties. Such transitions in the vegetated surface result in differences in the absorption and partitioning of incident solar radiation with uncertain consequences for regional climate. Simple descriptions of surface and subsurface changes over time in the discontinuous permafrost zone often remain elusive because of the complex spatial patterning of vegetated surface. The analysis of remote sensing data to determine the spatial extent and location of different surface features, and their changes, provides a means to track the temporal changes that have occurred since the dawn of of the remote sensing data record. Here, we evaluate the uncertainties associated with generating albedo from Landsat tm. There are two primary sources of uncertainty in the albedo product generated from Landsat; uncertainty associated with coefficients assigned to Landsat bands for generating albedo, and uncertainty in the raw digital remote sensing values. We employed a Monte Carlo method of random parameter generation and implementation of these coefficients to characterize changes to and uncertainty in Landsat albedo in an area of pronounced thaw in the discontinuous permafrost zone in west-central Alaska. The motivation for the uncertainty analysis is to quantify significant changes to land surface properties over time. Results indicate that the overall variability in the albedo layer is not strongly impacted by the coefficients applied to the Landsat data bands, and more affected by the variance within the Landsat data. Changes in albedo over the past 40 years tend to be concentrated along the edges of existing features, especially lakes.

15015033 Lang, Ashley (University of Georgia, Odum School of Ecology, Athens, GA); Varner, Ruth K.; Osman, Matthew; Burke, S. A.; Wik, Martin and Crill, Patrick M. Spatial variability of methane ebullition from permafrost thaw ponds in a subarctic mire [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51E-0333, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Methane (CH4) has an important role in the energy budget of the atmosphere. Warming due to radiative forcing by this and other greenhouse gases is amplified at high latitudes. Rising soil and air temperatures in these regions lead to permafrost thaw and the potential release of large amounts of CH4 and CO2 to the atmosphere. Where permafrost thaw is occurring, a changing landscape may lead to new CH4 sources. Small ponds are key features of these landscapes. Forming in depressions of previously frozen ground, thaw ponds may release large quantities of CH4 through ebullition (bubbling), yet little has been done to assess their potential contribution to carbon emissions from ecosystems with thawing permafrost. We have made summer measurements of CH4 ebullition from thaw ponds located within the Stordalen Mire, a subarctic permafrost complex in northern Sweden. Our findings suggest that small water bodies can be a substantial local CH4 source. Ebullition occurred episodically and varied spatially, both within and among the ponds. Over a three-week period in July 2013, average bubble CH4 concentration varied from 2 ppm to 1.6% and total bubble flux from 0 to 5456 mg CH4 m-2 d-1. Fluxes were highest from deeper ponds while shallower, and presumably younger, ponds produced significantly less gas with a much lower CH4 concentration. Temperatures and physical characterization of the ponds suggest that substrate type may be as important as heat in influencing the rate of ebullitive flux. Although spatial and temporal variability make CH4 flux from thaw ponds difficult to quantify, these findings suggest that continued warming may drive a positive feedback for CH4 emission and permafrost degradation in the Arctic. Future data on thaw pond cover across Stordalen Mire will allow us to better understand the changing contribution of these ponds to the local total CH4 emission.

15014989 Layne, M. (California State University, Division of Science and Environmental Policy, Marina, CA); Prado, M. F.; Anderson, S. M.; Bryce, Julie G.; Palace, Michael W.; Varner, Ruth K. and Crill, Patrick M. Estimating mercury sequestration as a function of vegetation along a thawing permafrost gradient [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B41C-0422, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Recent studies suggest that with increasing temperatures due to climate change, there is likely to be a release of mercury (Hg) from its frozen stores in high latitude peatlands. This mobilized Hg may then leave the terrestrial ecosystem by entering the hydrosphere or remain sequestered in Arctic terrestrial ecosystems as it is incorporated into wetland vegetation. One challenge in forecasting the fate of mercury with climate change lies in estimating the degree to which plants accumulate mercury as a function of the species and/or the microenvironment. Existing studies show mercury concentrations in plants can vary significantly in just a short distance in peat lands and can even vary among the same species in different ecotones. In order to enhance understanding the distribution of mercury in vegetation across the permafrost thaw gradient we carried out mercury analyses of foliage samples in well-characterized ecotones in Stordalen mire, in Abisko, Sweden. This mire, which lies at the edge of the discontinuous permafrost zone, is being severely impacted by climate change and thereby affords an ideal opportunity to investigate the influence of thawing on mercury sequestration. We separated vegetation communities into five different categories; Hummock, Tall Shrub, Semiwet, Tall Graminoid, and Wet. Percent cover for each site was determined using a 1 m2 quadrat sectioned into 64 subplots. A camera suspended above the plots collected images in the near infrared, red and green bands. This image data was used to analyze at both the local plot scale and to scale up to the landscape level for both vegetation communities and proportion of key species. For our analysis we only used the near infrared and determined entropy, angular second momentum and lacunarity. Extractable mercury concentrations in the plant tissues were measured via cold vapor Inductively Coupled Plasma Mass Spectrometry. Mercury abundances varied between 7.0 and 28.7 ng/g in foliar tissue (for S. lapponum and Sphagnum, respectively). Results of a Kruskal Wallis test found a significant difference in Hg sequestration based on plant species (df=9, c2=18.04, p=0.03). Our results suggest that variable mercury concentrations in Sphagnum (7.6-28.77 ng/g) are related to abundance of water with higher concentrations found in drier areas. The Wet site types showed the lowest overall spatially averaged mercury concentration (<5 ng/g). Variations of spatially averaged mercury content in Tall Shrub sites (>12 ng/g) are most likely due to the large differences in overall species composition. The integration of plant Hg abundances across sites well-characterized for spectral properties may ultimately enable the scaling up to an ecosystem model for Hg distributions within the landscape.

15015041 Werner, S. L. (University of New Hampshire Main Campus, Earth, Ocean and Space Sciences, Durham, NH); Malhotra, Avni; McCalley, C. K.; Varner, Ruth K.; Roulet, Nigel T. and Crill, Patrick M. Increase in sedge biomass across a permafrost thaw gradient correlates to changes in the magnitude and isotopic composition of methane emissions [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51E-0347, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Species transitions have been observed in northern latitudes in response to a warming climate. Sedge species in particular are becoming more abundant as permafrost thaws. These species are closely linked to increases in methane (CH₄) emission, which has 23 times the global warming potential of carbon dioxide (CO₂) and wetlands are a major natural source of emissions. Understanding how CH₄emissions are associated with species changes during thaw is essential for estimating CH₄ fluxes from discontinuous permafrost regions and for predicting the trajectory of CH₄ emissions under future climate change. To understand the relationship between sedges and methane emissions, we measured methane fluxes and the isotopic composition of pore water CH₄ and CO₂ along a permafrost thaw gradient in Stordalen Mire, Abisko, Sweden. To determine the controls on CH₄emission, we measured vegetation biomass, pH, soil temperature, active layer depth and species composition. Significant differences were found between different vegetation classes, with lowest fluxes of CH₄ observed in the frozen palsa (0.73±4.41 mg m-2 d-1), mid-range fluxes in Sphagnum sites (14.21±15.8 mg m-2 d-1) and highest fluxes in the wet graminoid (165.4±136.6 mg m-2 d-1). The best indicator of CH₄ flux was biomass of sedge vegetation (e.g Eriophorum vaginatum and Carex spp.) (R²=0.86 p=0.001). In general, pore water CH₄ increased with depth and was on average highest and most variable in the Carex spp. dominated sites compared to the mixed vegetation, Sphagnum and E. vaginatum dominated sites. The best predictor of below ground CH₄ concentration was also sedge biomass (R²=0.86 p=0.01 at 30 cm). The variability and abundance of CH₄ indicates differences in methane production rates depending on the presence of sedges. Patterns in del13C-CH4 suggest a shift from hydrogenotrophic production in Sphagnum dominated sites to increasing contributions from acetate fermentation in sedge-dominated sites. These observations identify transitions to sedge dominated ecosystems as an important contributor to rising CH₄emissions during permafrost thaw, a positive feedback to a warming climate.

15015252 Sparkes, Robert B. (University of Manchester, Manchester, United Kingdom); Dogrul Selver, Ayca; Bischoff, Juliane; Gustafsson, Orjan; Semiletov, Igor P.; Dudarev, Oleg V.; Talbot, Helen M. and Van Dongen, Bart E. Terrestrial organic carbon and biomarker export from East Siberian permafrost to the Arctic Ocean [abstr.]: in Goldschmidt abstracts 2014, V.M. Goldschmidt Conference - Program and Abstracts, 24, p. 2360, 2014. Meeting: Goldschmidt 2014, June 8-13, 2014, Sacramento, CA.

15015960 Clough, James G. (Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK); Daanen, Ronald; Benoit, Dick; Holdmann, Gwen and Harun, Nina T. Dynamic integration of geothermal data; an example from Pilgrim Hot Springs, Alaska [abstr.]: in Geological Society of America, 2014 annual meeting & exposition, Abstracts with Programs - Geological Society of America, 46(6), p. 207, 2014. Meeting: Geological Society of America, 2014 annual meeting & exposition, Oct. 19-22, 2014, Vancouver, BC, Canada.

Alaska has 48 hot springs (>50°C) and 49 warm to cool thermal springs (<50°C). Pilgrim Hot Springs (PHS) is one of the hottest geothermal systems in the north-central geothermal belt, extending eastward from the Seward Peninsula to the Canada border and containing 39 thermal springs related to radioactive mineral decay in plutons and extensional tectonic forces. PHS lies within the Pilgrim River valley on the Seward Peninsula, a cold climate region with discontinuous permafrost. The hot springs at Pilgrim have created a large area (~2 km²) without permafrost. Data from PHS research is included in the Alaska Geothermal Database that is part of the National Geothermal Data System. PHS data includes remote sensing, airborne geophysics, ground-based geophysics and borehole data. The hottest temperature recorded to date is just over 91°C with a shallow hot aquifer beneath a clay cap between 7.5 and 15 m below the surface. Below the shallow hot water is a temperature reversal into a cooler aquifer of approximately 65°C, below which is a strong temperature gradient with a maximum temperature near bedrock of 91°C. Attempts to locate the upflow zone at PHS have failed. Temperature data analysis suggests an upflow zone outside the current focus area where access is difficult due to logistical obstacles. This location does not satisfy a hydrologic model that suggests that the cold aquifer is actively cooling the system and flowing past the upflow zone from the Kigluaik Mountains to the Pilgrim River. This leaves only a very small upflow region between existing boreholes where the hot water can flow from bedrock to the surface. Recently collected magnetotelluric (MT) data shed some light on the geologic structures of the sedimentary basin, but this dataset does not capture all the nuances of the flow pattern that developed over centuries. Utilizing the geothermal database, we can integrate the MT data with the geochemistry, borehole and hydrologic data to locate the actual upflow zone. This will be accomplished by 3-Dimensional geospatial referencing of this data to identify the next step in the exploration process. The Alaska geothermal database points out the shortcomings of available data for PHS as well. Adding a seismic study of PHS will identify the local fault structures to accurately locate a production well in the upwelling zone.

15015023 Bruhwiler, Lori (NOAA, Earth System Research Laboratory, Boulder, CO). Top-down constraints on wetland emissions of CH₄ [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B44C-08, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

An important challenge for predicting the future evolution of the global climate is representing feedback processes. One such feedback involves methane emissions from wetlands. Vast stores of carbon in the Arctic may thaw over the next centuries, and it is important to understand how wetlands will evolve over time since large scale drying will likely result in smaller emissions of CH₄ and more respiration of CO₂. Permafrost thaw can also produce smaller emissions if ponded soils drain. Changes in precipitation and land use in the Tropics and mid-latitudes may also lead to significant changes in emissions, shifting the balance between respiration of CH₄ and CO₂. Modeling CH₄ emissions from wetlands is a complicated problem since even the distribution of wetlands is subject to much uncertainty and is treated in a variety of ways in current CH₄ emission models. Nutrient cycling and small-scale processes must also be represented at scales that are large enough to be interpreted at global scales. Ultimately, confidence in models that couple greenhouse gas emissions with climate models should be dependent on the ability of the emission models to reproduce the current observed spatial distribution and variability. Global network and campaign data are critical to evaluation of bottom-up emission models, and here we show results using both global and regional modeling approaches. Inverse techniques can also provide details on how simulated emissions must be adjusted in order to obtain optimal agreement with observations, and this can lead to insights into deficiencies in the models. We demonstrate this by showing results from a suite of inversions performed using different wetland models.

15015035 Burke, S. A. (University of New Hampshire, Institute of the Study of Earth Oceans and Space, Durham, NH); Varner, Ruth K.; Palace, Michael W.; Wik, Martin; Crill, Patrick M. and Lang, Ashley. The sound of bubbles; monitoring methane fluxes from thaw ponds using acoustic systems [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51E-0335, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Methane (CH₄) is a greenhouse gas released from wetlands. Thaw ponds from related subsidence and slumping permafrost contribute to the overall CH₄ emission in northern latitudes, yet little is know about some aspects of this methanogenesis pathway. Methane ebullition (bubbling) from three thaw ponds has been monitored for two ice-free seasons at Stordalen Mire in northern Sweden using manual bubble traps and an acoustic monitoring system. The acoustic system allows for continuous monitoring and for bubbling events to be captured at the time of release. A total of twelve bubble traps were deployed in six thaw ponds and six peat areas at the Stordalen Mire, ten of which included the acoustic monitoring system. Overall CH₄ bubble flux from the ponds during July 2013 was lower than the same period in 2012. The different variation in fluxes between the years for the three ponds suggests that each pond responds differently to changes in the ecosystem. One of the ponds is an example of a self-contained slumped permafrost area while the other two are much more fen-like in vegetation characteristics and both have water flowing into the area from the neighboring lake. Stable isotopic signatures of CH₄ gas collected at one site suggest CO₂ reduction as the primary production pathway while those of the other two sites suggest acetate fermentation. The more fen-like sites appear to be more sensitive to changes in environmental conditions, which would explain the observed differences in CH₄ flux between years. Water temperature does not appear to correlate with CH₄ flux in any of the ponds.

15015066 Ciais, P. (Commissariat à l'Énergie Atomique et aux Énergies Alternatives, Gif sur Yvette, France) and Sabine, C. L. Carbon cycle and climate change, a tale of increasing emissions and uncertain future sinks [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract U22A-01, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

CO2 has increased by 40% in the atmosphere above pre-industrial levels, and is reaching close to 400 ppm. It's a fact that the increase of CO2 is due to human-caused emissions from land use change and fossil fuel use. Yet, an average of 54% of these human emissions was removed from the atmosphere by CO2 sinks in the ocean and the land biosphere. In the IPCC AR5 report, an update of the global carbon budget is provided, together with CH4 sources and sinks, over the last 3 decades. The first finding is the recent acceleration of fossil fuel CO2 emissions during the last decade, and the fact that sinks have increased proportionally with emissions. Future projections of the coupled climate-carbon cycle system using CMIP5 models, translated into compatible emissions for each RCP pathway radiative forcing trajectory will be presented. When the carbon cycle is coupled to simulations of climate change, the sinks weaken, causing a positive feedback on warming, but uncertainties on the magnitude of this feedback and on the role of each regions, remain very high, as shown by the large spread between models. The second finding concerns additional feedbacks, most likely of positive sign, such as CO2 and CH4 emissions from thawed permafrost and nutrient limitations on land carbon storage. These feedbacks were not included in the CMIP5 models and represent a large (but uncertain) source of extra warming for any given economic scenario of anthropogenic emissions

15014982 Erickson, L. M. (Gustavus Adolphus College, Department of Geology, St. Peter, MN); Prado, M. F.; Wik, Martin; DeStasio, J.; Halloran, M.; Setera, J. B.; Bryce, Julie G.; Crill, Patrick M.; Johnson, Joel E. and Varner, Ruth K. Mercury dynamics in sub-arctic lake sediments across a methane ebullition gradient [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B41C-0410, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Recent studies have suggested that Arctic warming may play a key role in enhancing carbon (C) and mercury (Hg) export from permafrost peatlands, yet the mechanisms by which Hg is mobilized during thaw remain enigmatic. To elucidate the links between these chemical systems, we investigated Hg concentrations in cores taken in organic C rich sediments in lake Villasjon (avg. depth 1.5 m) at the Stordalen Mire, Abisko, Sweden. We chose coring sites based on zones with significantly different ebullitive methane (CH₄) fluxes established in earlier studies and we hypothesized that the microbial community producing CH₄ is also potentially mobilizing Hg. Recovered sediment cores (~44 and 40 cm in depth) are characterized by having roughly 30 cm of organic-rich silt material on top of a transition to more clastic material in the bottom ~10 cm. Cores were sub-sampled every 2 cm, and the sediment samples were then freeze-dried and subsequently analyzed for extractable Hg via cold vapor inductively coupled plasma mass spectrometry. Mercury is most abundant in the upper portions of both sediment cores, after which concentrations decrease with depth. The high ebullition site had Hg concentrations exceeding 80 ng_Hg/g_sediment at the core top that decreased to a low Hg concentration <15 ng_Hg/g_sediment at the core base. The low ebullition site had overall lower concentrations compared to the high ebullition site with more intermediate values (<50 ng_Hg/g_sediment) starting at 2 cm depth, dropping to <15 ng_Hg/g_sediment at ~26 cm. We found differences (>&eq;50%) in overall Hg contents between both cores in the top layers of the core. Mercury content positively correlated with total organic C (TOC, R²=0.74) and sulfur (S, R²=0.92) in the high ebullition site. Mercury content also negatively correlated with dissolved inorganic carbon (DIC) in the high ebullition site (R²=0.71). These relationships are only seen in the high ebullition site, whereas in the low ebullition site, Hg links with other geochemical data (e.g., TOC, C, nitrogen, S, DIC) were more variable. Our findings imply that (1) processes that enhance CH₄ mobilization may also affect Hg dynamics in sediment cores and (2) assessing overall Hg behavior in lakes requires cores in multiple locations.

15015032 Kochendorfer, John (NOAA, Oak Ridge, TN); Heuer, Mark; Dumas, E.; Meyers, Tilden P.; Baker, Bruce; Healy, Claire E.; Munster, J.; Sayres, D. S. and Anderson, J. G. Eddy covariance measurements of methane fluxes from an Arctic sedge wetland [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51E-0332, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Concern and uncertainty regarding the magnitude of greenhouse gas emissions from permafrost regions has prompted a new field study on the North Slope of Alaska. In support of an aircraft eddy covariance campaign beginning in 2013, a CH4 and CO2 eddy covariance flux tower was installed in a wet sedge ecosystem along the aircraft measurement transect, south of Prudhoe Bay, AK. The tower-based results indicate that this ecosystem is a strong source of CH4 to the atmosphere, with preliminary fluxes of approximately 100 mg CH4 m-2 day-1 measured in late July. Prior to installation in Alaska, the tower and aircraft flux measurement systems were also compared for one week over a salt marsh on Wallops Is, VA in June, 2013. The flux of CH4 to the atmosphere was significantly smaller than at the sedge site in Alaska, and was measured by the eddy covariance tower to be about 10 mg CH4 m-2 day-1. Results from this study will be presented, with a specific focus on the tower-based CH4 flux measurements and their correlation with soil temperature.

15015013 McCalley, C. K. (University of New Hampshire, Institute for the Study of Earth, Oceans and Space, Durham, NH); Shorter, J. H.; Zahniser, M. S.; McManus, J. B.; Nelson, D. D.; Hodgkins, S. B.; Chanton, J.; Crill, Patrick M.; Varner, Ruth K. and Saleska, S. R. High-resolution stable isotope measurements elucidate patterns of CH₄ metabolism in temperate and northern wetlands [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B43G-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Methane flux from wetlands is both a critical component of the global CH₄ budget, and highly sensitive to global climate change. Changes in CH₄ dynamics under climate change can arise from alterations in temperature and precipitation patterns as well as shifts in plant community composition associated with shrub encroachment and permafrost thaw. Gaps in our understanding of the mechanisms driving CH₄ production and consumption dynamics, however, limit our ability to predict the magnitude of this response under future climate conditions. To address these gaps, we quantified the isotopic composition of CH₄ fluxes from a high latitude (68°N) wetland underlain by discontinuous permafrost (Stordalen Mire, Sweden) and a temperate wetland (43°N) undergoing shrub encroachment (Sallie's Fen, NH). We used newly developed quantum cascade laser technology, linked to automated chambers, to quantify isotopes (¹³C-CH₄ and recent addition of CH₃D laser) at a high temporal frequency and partition net CH₄ emissions into its component parts, methanogenesis (including both acetoclastic, and hydrogenotrophic pathways) and methanotrophy (which consumes CH₄ primarily via aerobic metabolism). Changes in plant communities and hydrology during permafrost thaw result in both large increases in CH₄ emissions as well as shifts in the CH₄ production pathway, from hydrogenotrophic to increasingly acetoclastic mechanisms. In contrast, shrub encroachment that replaces sedge species reduces CH₄ emissions, but has a smaller impact on the isotopic signature of emitted CH₄, with both hydrogenotrophic and acetoclastic production likely occurring across plant communities. Three years of measurements at Stordalen Mire identify temperature and hydrologic variability as key contributors to both annual and interannual patterns in d13C-CH₄. At the fully thawed fen site where the water table is continually at or above the peat surface, d13C-CH₄ was relatively constant across years, with an annual pattern suggestive of more hydrogenotrophic production early and late in the growing season. At the intermediate thaw, Sphagnum dominated site high variability in water table position both within and across years contributed to larger fluctuations in d13C-CH₄. Together these results provide insights into the role of plant communities and variable environmental conditions in shaping CH₄ production and consumption patterns in diverse wetland ecosystems. Ongoing efforts to incorporate this isotopic information into a process based wetland model, Wetland-DNDC, expand our ability to predict and understand changes in CH₄ dynamics under climate change.

15014974 Onstott, Tullis C. (Princeton University, Princeton, NJ); Lau, C. M.; Stackhouse, B. T.; Medvigy, D.; Chen, Yuheng; Layton, A.; Vishnivetskaya, T. A.; Pfiffner, S. M.; Whyte, Lyle; Mykytczuk, N.; Ronholm, Jen; Allan, Jennifer; Bennett, P.; Chourey, K. and Hettich, R. L. An atmospheric CH₄ sink in the High Arctic and its implication for global warming [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B33K-0616, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Arctic permafrost underlies about 16% of the Earth's surface and contains ~500 Pg of C down to one meter. Organic-rich peatlands (averaging ~4 wt% SOC) comprise 19% of this area, whereas the remaining 81% is permafrost-affected mineral cryosols (0.5-1.5 wt% SOC). Temperatures in the Arctic are predicted to increase ~6°C over the next 100 years which increases the depth of the active layer, the seasonally thawed soil above the permafrost. Thawing permafrost peat deposits (e.g. Stordalen Mire, Sweden) are currently CH4 sources. Field measurements, intact core studies and microcosm experiments performed by us, however, over the past few years on mineral cryosols associated with ice wedge polygons from Axel Heiberg Island (AHI) in the Canadian High Arctic consistently indicate that they are sinks for atmospheric CH4 as well as the CH4 emitted from the underlying permafrost. After 1.5 years of thawing at 4°C, 1 m long intact cores of the active layer and underlying permafrost mineral cryosols collected from ice wedge polygons at AHI continue to exhibit uptake of atmospheric CH4 even for water saturated cores. The measured core fluxes are consistent with flux measurements performed in the field over the past two years, which range from 0.005 to 0.89 mg CH4-C/m2/hr and which have revealed significant differences in the atmospheric CH4 consumption fluxes between the polygon interiors and the polygon troughs. Metagenome and metaproteome analyses of these mineral cryosols indicates that the pmoA genes and proteins are most similar to an uncultured methanotroph type known as USC-a, which is recognized as a high affinity, atmospheric CH4 oxidizer. Our microcosm studies have yielded atmospheric CH4 uptake rates that are consistent with those of published results from high latitude organic-rich soils and temperate forest soils and indicate a temperature dependency for the cellular rate of CH4 oxidization that is approximately twice that reported for methanogenesis. This temperature dependency when combined with annual temperature records from nearby Eureka weather station suggests that these High Arctic ice wedge polygons are significant annual sinks for atmospheric CH4. Because the maximum atmospheric CH4 uptake rate coincides with the summer time dips in the recorded atmospheric CH4 and peaks in d13C, we propose that seasonal variations in the high latitude atmospheric CH4 are partially modulated by the activity of atmospheric CH4 oxidizers. We also suggest that this sink will increase with rising Arctic temperatures and may lessen the interannual increases in atmospheric CH4.

15015018 Prado, M. F. (University of New Hampshire, Earth Sciences, Durham, NH); Varner, Ruth K.; Bryce, Julie G.; McCalley, C. K.; Erickson, L. M. and Crill, Patrick M. Mercury export pathways in thawing peatlands; insights from Stordalen, Sweden [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B44B-08, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Recent studies have shown that climate change in northern high latitudes plays a significant role in enhancing the mobilization of previously sequestered mercury (Hg) in peatlands to the atmosphere and hydrosphere. The magnitude and mechanics of Hg mobilization, however, remain poorly constrained. To investigate the coupling of different export pathways and the major fate and transport of Hg in a subarctic ecosystem, we measured atmospheric Hg fluxes across a permafrost thaw gradient and compared these fluxes with exchangeable Hg from peat cores collected in July 2012 and July 2013 at the Stordalen Mire, Abisko, Sweden (68°21'N). Mercury flux measurements were estimated using a Tekran 2537 ambient air mercury analyzer integrated into a dynamic chamber system. The nine chamber array is divided into three sites, three chambers per site: (1) palsa site: dwarf-shrub dominated hummocks overlying permafrost, (2) Sphagnum: semi-wet hollows with 100% sphagnum cover with minor Eriophorum vaginatum, and (3) Eriophorum: wet hollows dominated by Carex rostrata and Eriophorum angustifolium. Continuous ambient air Hg measurements were made for multiple days at each site prior to flux chamber measurements. All three sites show a diel pattern characterized by Hg deposition during lows of photosynthetically active radiation (PAR) and ground temperature and a release of Hg during the peak PAR and ground temperature periods (13:00-15:00 h). The palsa site yielded the highest Hg flux accompanied with the least amount of Hg deposition in the evening. The Eriophorum releases the least amount of Hg and is associated with the highest Hg deposition. The Sphagnum shows the most variability of the three sites, at times releasing as much as the palsa site but absorbing more than the Eriophorum in one instance. Consideration of the Hg flux measurements together with exchangeable Hg concentrations of the peat suggests that the palsa has the highest amount of stored Hg and given the aerobic conditions present near the surface the preferred pathway of export is likely volatilization. The Sphagnum-dominated sites have less abundant Hg in the core (1-20 ng/g) than the palsa (10-60 ng/g), and the Eriophorum-dominated sites have intermediate values (1-70 ng/g), at certain depths comparable to the peat cored from the palsa. Taken together our results suggest that during initial stages of permafrost thaw export of gas-phase mercury may be an important pathway, but as thawing continues mercury export into the hydrosphere becomes significant. Further, our findings imply that the bulk of Hg released as a consequence of permafrost thaw is most likely exported into the hydrosphere where it is more susceptible to being methylated.

15014970 Sayres, D. S. (Harvard University, School of Engineering and Applied Sciences, Cambridge, MA); Healy, Claire E.; Munster, J.; Anderson, J. G.; Dumas, E.; Dobosy, Ron; Baker, Bruce and Langford, J. Regional measurements of methane fluxes and methane isotopologues in the North Slope of Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B33K-0612, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Rapid changes in the Arctic climate, exemplified by the decrease in end of summer sea ice, require regional understanding of changes in the Arctic system. Due to the inaccessibility of much of the Arctic region in situ aircraft measurements are well suited to providing a high spatial resolution map of a changing Arctic. We present here measurements of methane emissions from thermokarst lakes and melting permafrost in the North Slope region of Alaska. These measurements were acquired during the summer 2013 mission of the Flux Observations of Carbon from an Airborne Laboratory (FOCAL) instrument suite using the Aurora Flight Sciences' Centaur aircraft. The FOCAL payload combines the Anderson Group's (Harvard University) Carbon spectrometers for measuring the concentrations of methane, carbon dioxide, nitrous oxide, and water vapor and the carbon isotopologues of methane and carbon dioxide with the NOAA Atmospheric Turbulence and Diffusion Division (ATDD) Best Air Turbulence (BAT) probe for measuring the turbulent winds from a moving aircraft. Together these allow for the measurement of trace gas fluxes. The measurements were obtained by flying low (~10 m altitude) over the North Slope.

15015026 Sepulveda-Jauregui, A. (University of Alaska Fairbanks, Water and Environmental Research Center, Institute of Northern Engineering, Fairbanks, AK); Walter Anthony, K. M.; Martinez-Cruz, K. C.; Anthony, P. and Thalasso, F. Seasonal and latitudinal variations in dissolved methane from 42 lakes along a north-south transect in Alaska [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B51D-0299, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Northern lakes are important reservoirs and sources to the atmosphere of methane (CH4), a potent greenhouse gas. It is estimated that northern lakes (>55°N) contribute about 20% of the total global lake methane emissions, and that emissions from these lakes will increase with climate warming. Temperature rise enhances methane production directly by providing the kinetic energy to methanogenesis, and indirectly by supplying organic matter from thawing permafrost. Warmer lakes also store less methane since methane's solubility is inversely related to temperature. Alaskan lakes are located in three well-differentiated permafrost classes: yedoma permafrost with high labile carbon stocks, non-yedoma permafrost with lower carbon stocks, and areas without permafrost, also with generally lower carbon stocks. We sampled dissolved methane from 42 Alaskan lakes located in these permafrost cover classes along a north-south Alaska transect from Prudhoe Bay to the Kenai Peninsula during open-water conditions in summer 2011. We sampled 26 of these lakes in April, toward the end of the winter ice-covered period. Our results indicated that the largest dissolved methane concentrations occurred in interior Alaska thermokarst lakes formed in yedoma-type permafrost during winter and summer, with maximal concentrations of 17.19 and 12.76 mg L-1 respectively. In these lakes, emission of dissolved gases as diffusion during summer and storage release in spring were 18.4% and 17.4% of the annual emission budget, while ebullition (64.2%) comprised the rest. Dissolved oxygen was inversely correlated with dissolved methane concentrations in both seasons; the absence of O2 enhances methane production, while high concentration of O2 could favor methane oxidation. These relationships suggest that permafrost type, and specifically the availability of permafrost organic matter, influences methane cycling in Alaskan lakes.

15015016 Serafimovich, Andrei (GFZ German Research Centre for Geosciences, Telegrafenberg, Potsdam, Germany); Metzger, S.; Hartmann, Jog; Kohnert, K. and Sachs, T. The Airborne Measurements of Methane Fluxes (AIRMETH) Arctic campaign [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B43G-07, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

One of the most pressing questions with regard to climate feedback processes in a warming Arctic is the regional-scale methane release from Arctic permafrost areas. The Airborne Measurements of Methane Fluxes (AIRMETH) campaign is designed to quantitatively and spatially explicitly address this question. Ground-based eddy covariance (EC) measurements provide continuous in-situ observations of the surface-atmosphere exchange of methane. However, these observations are rare in the Arctic permafrost zone and site selection is bound by logistical constraints among others. Consequently, these observations cover only small areas that are not necessarily representative of the region of interest. Airborne measurements can overcome this limitation by covering distances of hundreds of kilometers over time periods of a few hours. Here, we present the potential of environmental response functions (ERFs) for quantitatively linking methane flux observations in the atmospheric surface layer to meteorological and biophysical drivers in the flux footprints. For this purpose thousands of kilometers of AIRMETH data across the Alaskan North Slope are utilized, with the aim to extrapolate the airborne EC methane flux observations to the entire North Slope. The data were collected aboard the research aircraft POLAR 5, using its turbulence nose boom and fast response methane and meteorological sensors. After thorough data pre-processing, Reynolds averaging is used to derive spatially integrated fluxes. To increase spatial resolution and to derive ERFs, we then use wavelet transforms of the original high-frequency data. This enables much improved spatial discretization of the flux observations, and the quantification of continuous and biophysically relevant land cover properties in the flux footprint of each observation. A machine learning technique is then employed to extract and quantify the functional relationships between the methane flux observations and the meteorological and biophysical drivers in the flux footprints. Lastly, the resulting ERFs are used to extrapolate the methane release over spatio-temporally explicit grids of the Alaskan North Slope. Metzger et al. (2013) have demonstrated the efficacy of this technique for regionalizing airborne EC heat flux observations to within an accuracy of ≤&eq;18% and a precision of ≤&eq;5%. Here, we show for the first time results from applying the ERF procedure to airborne methane EC measurements, and report its potential for spatio-temporally explicit inventories of the regional-scale methane exchange.

15014967 van Winden, E. M. (Utrecht University, Earth Sciences Department, Utrecht, Netherlands); Sapart, C. J.; Roeckmann, T.; Vonk, Jorien; van der Veen, C.; Schade, J. D.; Lynch, Laurel and Zimov, N. Constraining methane formation/removal pathways with stable isotopes in different aquatic environments throughout the summer season in the Kolyma region, north-east Siberia [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B33K-0609, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Large uncertainties exist on the past, current, and future atmospheric methane budget, especially on the role of Northern Arctic wetlands, which are important methane sources. CH4 emissions from the large Arctic carbon reservoirs are predicted to increase when Arctic temperatures rise and permafrost thaws. Organic carbon released by Arctic permafrost degradation increases methanogenesis, enhancing the flux of methane to the atmosphere. Emissions of methane from wetlands are difficult to quantify because of the complex mechanisms involved in methane production and removal and their heterogeneity within different aquatic environments. During the relatively short summer season the change of many environmental parameters (e.g. temperature, active layer depth, pH, water depth, substrate biolability) will affect methanogenesis. The different production and removal mechanisms are associated with different isotope effects, and therefore isotope measurements may help quantify the relative importance of the various processes. In this study, we investigate the isotopic signature (dD and d13C) of methane in Siberian lakes, ponds, wetlands, streams, and rivers to better understand the seasonal variations in methane mixing ratios and stable isotopes. Sampling of ebullition released by sediment stirring was conducted in different aquatic environments at locations with different underlying permafrost type (Pleistocene-aged Yedoma or Holocene-aged floodplain), and at different times during the summer season. In addition, air samples were taken above each aquatic sampling site. Preliminary results showed a wide range of dD values and d13C values, varying from about -200 ppm to -400 ppm, and -80 ppm to -40 ppm, respectively. Our final methane isotope results allow identifying seasonal variations in: (1) methane formation (acetate fermentation or CO2 reduction) and removal pathways (oxidation) and (2) type of substrates. Mixing ratios and the isotopic signature of methane may allow us to better understand how the methane formation/removal pathways vary during the summer season. Understanding seasonal variability of methane release from various source environments will help to model current and future changes in the global methane budget.

15012992 Ward, M. K. (McGill University, Department of Geography, Montreal, QC, Canada) and Pollard, W. H. The geomorphology of two hyper-saline springs in the Canadian High Arctic [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract V21A-2691, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

On Axel Heiberg Island in the Canadian High Arctic a number of low temperature perennial saline springs occur despite being subject to a cold polar desert climate with a mean annual air temperature of -18°C. Associated with 2 groups of hyper-saline springs are distinctive landforms resulting from winter deposition of salt minerals. These deposits resemble tufas structurally but unlike true tufas which are composed of carbonate minerals, these landforms are formed mainly of salt. This study hypothesizes that the extreme cold winter air temperatures cools water temperatures triggering rapid precipitation of various salt minerals (mainly hydrohalite, NaCl*2H2O) which subsequently alters the flow hydrology by obstructing summer flow paths. The tufa-like appearance of these salt deposits reflects the interaction between changing water temperature, chemistry and flow. This research characterises the geomorphology and geochemistry of two hyper-saline springs on Axel Heiberg Island: the first is located at Wolf Diapir (79°07'23"N; 90°14'39"W), the deposit at this site resembles a large conical mound (2.5 m tall ´ 3m diameter). The second is located at Stolz Diapir (79°04'30"N; 87°04'30"W), in this case a series of pool and barrage structures staircase down a narrow valley for approximately 300 m (several pools are 10 m wide ´ 3 m deep). The springs have very different seasonal surface hydrologic regimes and topographic settings which influence the pattern of mineral precipitates. The accumulation of precipitates occurs during the winter and is dominated by the formation of hydrohalite. In the summer, the accumulated hydrohalite melts incongruently to form halite; spring water and snowmelt dissolves various parts of the accumulations, changing the morphology of the deposits. The aim of this poster is to present preliminary observations characterising the processes driving tufa formation in a permafrost environment, a process that has not been described in detail in geomorphic literature. Preliminary data on surface and groundwater conditions of the springs; groundwater chemistry and mineral precipitates are presented. These data are used to model tufa processes and formation. Additional fieldwork is planned for April 2013 to expand and validate these observations. An interesting application of this research pertains to the search of liquid water on Mars. These features offer a potentially unique indication of groundwater activity in areas of cold permafrost and thus may aid in the site selection for future Mars missions. Axel Heiberg Island's cold and dry climate provides a Martian analogue setting that is a viable alternative to the costs and risks associated with full Mars missions. Numerous features on the surface of Mars indicate the action of water; e.g. gullies were observed within a small number of impact craters that suggest these have been formed in the recent past. It is believed water would exist in a briny nature that would allow it to remain stable on the surface for short periods of time. Results from NASA's Phoenix mission on Mars have provided the first physical evidence of the presence of liquid saline water. Finding water on Mars could have astrobiology implications and potentially the discovery of life on another planet.

15015019 Wilson, C. J. (Los Alamos National Laboratory, Los Alamos, NM); Chen, Min; Rowland, J. C. and Altmann, G. L. Quantifying seasonal dynamics of surface inundation on the Barrow Peninsula, AK [abstr.]: in AGU 2013 fall meeting, American Geophysical Union Fall Meeting, 2013, Abstract B44C-02, December 2013. Meeting: American Geophysical Union 2013 fall meeting, Dec. 9-13, 2013, San Francisco, CA.

Wetlands are commonly distributed across the Arctic Coastal Plain of Northern Alaska, a low-gradient region underlain by continuous permafrost. They are important components of the global biogeochemical cycle because of the large carbon stores and potential release of this carbon as CO2 and CH4 due to climate change. These wetlands are recharged seasonally by water from snowmelt and summer rainfall, but their area shrinks significantly during the snow free season every year. While seasonal and long-term thaw lake area change is well documented, the seasonal dynamics of smaller wetland features including polygon ponds is poorly quantified. Understanding and quantifying the factors driving and controlling the spatial redistribution of surface water will help in the parameterization of models and evaluation of predictions of water, energy and carbon budgets for lowland Arctic regions. In this study, we used high spatial resolution images (WorldView 2 and QuickBird) on 9 dates from 2006-2012 to investigate the seasonal change and spatial pattern of surface water area for a 4700 ha wetland near Barrow, AK. We found that the surface water area decreased dramatically throughout the summer each year. For example, it decreased by 782 ha (74%) from June 24 to July 21 and continued to decrease by 153 ha (54%) from July 21 to August 4 in 2010. The correlation between the seasonal change in surface water area and local precipitation minus evapotranspiration was low, indicating that the local water balance had little direct control on the change in surface water area through the Summer. Instead, the post snowmelt change in the area of surface inundation as a function of time was well fit by the equation for hydrograph recession, indicating that drainage of ponded water in July and August may be primarily controlled by shallow subsurface flow rather than through evapotranspiration, even in this very low gradient environment. The rate of drainage of surface water was significantly different between DTLBs of different ages, with young DTLBs being the fastest, followed by medium age, and old and ancient DTLBs. In terms of spatial distribution pattern, we found that about 70% of surface water area was distributed in the DTLBs. The percentage of surface water area in the individual DTLBs was relatively stable in the same season of every year, as there was high correlation in the percentage of surface water area within DTLBs among similar seasons no matter whether they were from the same year or different years. During and right after spring snowmelt, macro-topography (represented by mean elevation of DTLBs) controlled the spatial distribution of surface water area. While in July and August, the micro-topography (represented by ice-wedge polygons) controlled the distribution of surface water area. Specifically, during and right after snowmelt, the DTLBs with lower elevations tended to have higher percentage of inundated area. In July and August, the DTLBs with ice-wedge polygons tended to have higher percentage of surface water area.

15014573 Bellefleur, Gilles (Geological Survey of Canada, Ottawa, ON, Canada); Riedel, Michael and Brent, Tom. Seismic and well-log inference of gas hydrate accumulations above the Umiak and Ya Ya gas fields, Northwest Territories: in CSPG/CSEG/CWLS geoconvention 2013 on Integration; geoscience engineering partnership; conference abstracts, CSPG CSEG CWLS Conference, 2013, illus. incl. sects., sketch map, 7 ref., 2013. Meeting: CSPG/CSEG/CWLS geoconvention 2013 on Integration; geoscience engineering partnership, May 6-12, 2013, Calgary, AB, Canada.

URL: http://cseg.ca/assets/files/resources/abstracts/2013/079_GC2013_Seismic_and_well ...

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