Permafrost Monthly Alerts (PMAs)

13006038 Fedotov, A. P. (Russian Academy of Sciences, Limnological Institute, Irkutsk, Russian Federation); Phedorin, M. A.; Enushchenko, I. V.; Vershinin, K. E.; Melgunov, M. S. and Khodzher, T. V. A reconstruction of the thawing of the permafrost during the last 170 years on the Taimyr Peninsula (east Siberia, Russia): Global and Planetary Change, 98-99, p. 139-152, illus. incl. strat. cols., sketch map, 107 ref., December 2012.

Reconstructing the temporal and spatial changes in climate on a seasonal basis during the past few centuries may help us better understand the modern-day interplay between natural and anthropogenic climate variability. The objective of this paper is to reconstruct the thawing of the permafrost at 71°N in Arctic Siberia during the termination of the Little Ice Age and the subsequent Recent Warming period. Sediment samples from two lakes on the Taimyr Peninsula were analysed by high-resolution X-ray fluorescence spectroscopy at a scan resolution of 1 mm, and pollen analyses were conducted. The depth-age models of the cores were constructed using 210Pb and 137Cs activity according to the constant rate of supply (CRS) model. The lake sediment cover of these lakes began to form ca. 1840. We defined three periods of increased permafrost thawing during the last 170 years. The first maximum of permafrost melting occurred from 1870 to 1880, the second episode was from 1900 to 1930 and the third began between 1960 and 1965. During these periods, the maxima of permafrost melting occurred with a specific time lag following. Abstract Copyright (2012) Elsevier, B.V.

DOI: 10.1016/j.gloplacha.2012.09.002

13007376 van der Ploeg, Martine J. (Wageningen University, Deptartment Environmental Sciences, Wageningen, Netherlands); Haldorsen, Sylvi; Leijnse, Anton and Heim, Michael. Subpermafrost ground water systems; dealing with virtual reality while having virtually no data: Journal of Hydrology, 475, p. 42-52, illus. incl. 3 tables, geol. sketch map, 93 ref., December 19, 2012.

Studies on the Earth's hydrology in general thrive on abundant data, while data on certain groundwater systems are virtually absent as a result of their inaccessibility. This poses challenges for understanding and modeling such systems, yet modeling is often the only option to study them. When it comes to limited data availability, a simple model may have a better predictive performance than a complex model. In a case study of a subpermafrost groundwater system on Svalbard we applied three simplified models which do not cover all processes, and compared their outcomes. The results of all models were different and sometimes contrasting. By combining all model results within their associated assumptions we show how dynamic processes in data-limited subpermafrost groundwater systems can be interpreted. Using multiple interpretations of a system by making different assumptions can thus be used to understand processes in data limited groundwater systems. Our results also illuminate the fierce data scarcity of subpermafrost groundwater systems, and the necessity of resolving this. Abstract Copyright (2012) Elsevier, B.V.

DOI: 10.1016/j.jhydrol.2012.08.046

13001310 Breecker, Daniel O. (University of Texas at Austin, Department of Geological Sciences, Austin, TX); Payne, Ashley E.; Quade, Jay; Banner, Jay L.; Ball, Carolyn E.; Meyer, Kyle W. and Cowan, Brian D. The sources and sinks of CO₂ in caves under mixed woodland and grassland vegetation: Geochimica et Cosmochimica Acta, 96, p. 230-246, illus. incl. 8 tables, sketch map, 78 ref., November 1, 2012.

We measured concentrations and stable carbon isotope compositions of carbon dioxide in the atmospheres of three caves in central Texas and one cave in southern Arizona in order to identify CO₂ sources and sinks. The vegetation above the caves studied is either savannah (two caves, above which vegetation has been minimally disturbed) or discrete patches of grassland and woodland (two caves, above which vegetation has been highly disturbed). We tested two hypotheses concerning CO₂ in the cave atmospheres: (1) cave ventilation by tropospheric air is the primary sink for CO₂ and (2) CO₂ is primarily derived from the deepest rooting plants growing above the caves. Within caves, we monitored CO₂ at individual locations on monthly and daily time-scales and measured CO₂ along transects with increasing distance from the cave entrances. We also measured CO₂ in the pore spaces of soils under grasses and trees above each of the caves. We calculated d¹³C values of respired CO₂ (d¹³C_r) for all gas samples using measured d¹³C values and CO₂ concentrations. We then identified the sources of cave CO₂ by comparing cave-air and soil CO₂d¹³C_r values. At all locations in each Texas cave, CO₂ concentrations were highest (lowest) and d¹³C values were lowest (highest) during the summer (winter). Cave-air CO₂ concentrations consistently increased and d¹³C values consistently decreased with distance from the cave entrances. Similar but smaller magnitude seasonal variations in CO₂ concentrations occurred in the Arizona cave and no seasonal or spatial variation in the d¹³C of cave-air CO₂ was observed. The mean d¹³C_r values of CO₂ in soils under grass were 3.5-4.5 ppm higher than the d¹³C_r values of CO₂ in soils under trees. In the caves under savannah, mean d¹³C_r values of cave-air CO₂ (-24 ppm in both caves) were within 1 ppm of the mean d¹³C_r values of CO₂ in soils under trees. In caves covered by large, contiguous areas of grassland, the d¹³C_r values of cave-air CO₂ were similar to grassland soil values during the summer and were intermediate between grassland and woodland soil values during the winter. The observed spatial and temporal variations in cave-air CO₂ are consistent with density-driven ventilation controlled by seasonal surface temperature changes as the primary sink for CO₂ in the Texas caves. The consistent agreement between soil and cave d¹³C_r values indicate that the same mixing and diffusion equations that are used to calculate d¹³C_r values of soil CO₂ also apply to cave-air CO₂. Our results suggest that the majority of CO₂ advects or diffuses into these caves from soils as a gas rather than being transported in aqueous solution. Measured d¹³C_r values and numerical production-diffusion modeling supports our hypothesis that the majority of gaseous CO₂ in these caves is derived from deeply rooted vegetation. The carbon isotope composition of groundwater and speleothem calcite used for paleoclimate records are therefore likely biased toward deeply rooted plants, even if sparsely present. Abstract Copyright (2012) Elsevier, B.V.

DOI: 10.1016/j.gca.2012.08.023

13004195 Chasmer, L. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Kenward, A.; Quinton, W. and Petrone, R. CO₂ exchanges within zones of rapid conversion from permafrost plateau to bog and fen land cover types: Arctic, Antarctic, and Alpine Research, 44(4), p. 399-411, illus. incl. 5 tables, 43 ref., November 2012.

Variability of midday net ecosystem CO₂ exchange (NEE) and respiration was measured using a transect of closed system chambers spanning transitions from channel fen, permafrost plateau, and ombrotrophic flat bog land cover types during the spring melt season (26 April-6 June 2008). The primary objective was to compare fluxes from different land cover types and topographic variability within zones adjacent to and including rapid permafrost thaw. During this period, the bog was the greatest net source of CO2 to the atmosphere, followed by plateau, and fen. NEE was slightly positive (indicating CO₂ loss to the atmosphere) during the snowmelt period (average = 0.009 ± 0.004 mg CO₂ m^-2 s^-1), and increased to 0.025 ± 0.012 mg CO₂ m^-2 s^-1, on average, possibly due to soil thaw and increased microbial activity within two days of completely snow-free conditions. Near surface soil temperature and depth to the water table were the most significant controls of soil and ground cover CO₂ fluxes within chambers at all sites (p < 0.05). Analysis of historical aerial photographs and satellite imagery of the area from 1947 to 2008 indicates that plateaus are converting more rapidly into bogs than fen, where 73% of plateau areas (since 1970) that thawed had become bogs (as opposed to 27% conversion into fen). Future research requires establishment of a full ecosystem or land cover greenhouse gas and soil nutrient exchange/transfer program, including CO₂ and water fluxes as well as dissolved organic and inorganic C, and CH₄ losses from the soil. These results contribute to a better understanding of northern soil and ground-cover carbon exchanges as greater areas of permafrost plateaus collapse and form bogs.

DOI: 10.1657/1938-4246-44.4.399

13004196 Lupascu, M. (University of Bristol, Bristol Glaciology Centre, Bristol, United Kingdom); Wadham, J. L.; Hornibrook, E. R. C. and Pancost, R. D. Temperature sensitivity of methane production in the permafrost active layer at Stordalen, Sweden; a comparison with non-permafrost northern wetlands: Arctic, Antarctic, and Alpine Research, 44(4), p. 469-482, illus. incl. 2 tables, sketch map, 83 ref., November 2012.

Relationships were determined between methane (CH₄) production and in situ conditions within the permafrost active layer during a single melt season at Stordalen, Sweden, with a specific emphasis on temperature sensitivity of methanogenesis. In situ temperature, moisture, pH, dissolved organic carbon, and CH4 concentration data were measured at three contrasting active layer sites (sedge mire, Sphagnum mire, and ombrotrophic bog), and laboratory incubations of active layer material were subsequently employed to determine the sensitivity of CH₄ production to temperature. Q₁₀ values, describing the CH₄ production response of peat to a temperature change of 10 °C, ranged from 1.9 to 3.5 and 2.4 to 5.8 for the sedge and Sphagnum mire sites, respectively. A wider review of the literature on Q₁₀ responses of methanogenesis in northern peatlands shows similar features to the temperature response of CH₄ production in the active layer at Stordalen. In general, Q₁₀ values are not significantly different in Arctic permafrost wetlands than non-Arctic northern wetlands; however, Sphagnum sites display Q₁₀ responses (mean Q₁₀ = 8) that are notably greater than that of wetter minerotrophic-sedge environments (mean Q₁₀ = 4.3). This finding has implications for the parameterization of Q₁₀ factors in numerical carbon cycling models, and suggests that the use of spatially variable Q₁₀ values could be a useful approach for more accurate modeling of CH₄ fluxes from northern wetlands under different climatic change scenarios.

URL: http://dx.doi.org/10.1657/1938-4246-44.4.469

13008576 Johnson, Donald L. (University of Illinois at Urbana-Champaign, Department of Geography, Urbana, IL) and Johnson, Diana N. The polygenetic origin of prairie mounds in northeastern California: in Mima mounds; the case for polygenesis and bioturbation (Horwath Burnham, Jennifer L., editor; et al.), Special Paper - Geological Society of America, 490, p. 135-159, illus. incl. 5 tables, sketch map, 150 ref., October 2012.

We studied low prairie (Mima) mounds and ridges with sorted stone borders separated by broad rubbly soil intermounds in areas near Mount Shasta, northern California. An earlier study ascribed a purely physical origin for these soil features based on a four-stage conceptual model. Mounds were interpreted as periglacially produced clay domes formed in polygonal ground and stone perimeters as loose gravity accumulations in unexplained shallow trenches at dome peripheries. The model was widely cited to account for similar stone-bordered prairie mounds and rubbly soil intermounds in the Pacific Northwest. Our observations and measurements indicate, however, that these mounded landscapes are more complex, and that a polygenetic origin best explains them. We suggest that combined bioturbation, seasonal frost action, and erosion processes, with occasional eolian inputs, best account for the mounds, their well sorted stone borders, and the poorly sorted rubbly soil intermound pavements. We propose a transitional, eight-stage conceptual model to explain this complex landscape. The model may generally explain the origin of other similar strongly bioturbated, cold winter-impacted, erosion-prone mounded tracts in the Pacific Northwest.

DOI: 10.1130/2012.2490(06)

13007234 Wang Yibo (Lanzhou University, Laboratory of Western China's Environmental Systems, Lanzhou, China); Wu Qingbai; Tian Liming; Niu Fujun and Tan Long. Correlation of alpine vegetation degradation and soil nutrient status of permafrost in the source regions of the Yangtze River, China: Environmental Earth Sciences, 67(4), p. 1215-1223, illus. incl. 2 tables, 40 ref., October 2012.

The impacts of alpine vegetation degradation on the main soil nutrients in the permafrost were studied by the comparative analysis of typical plots in the source regions of the Yangtze River. It is found that vegetation degradation has a severe effect on the content of the main soil nutrients, especially in the topsoil (0-10 cm) where the soil nutrients content were changed. There are good correlations between soil organic matter (SOM) and total nitrogen (TN), total phosphorus (TP) and total potassium (TK) in alpine soil. The change to soil nutrients increases concomitantly with the increasing intensity of vegetation degradation. Soil nutrients change dramatically in the thermokarst lakes in the surrounding area where vegetation is severely degraded. The ratio of SOM, TN, TP and TK in different soil layers of the adjacent thermokarst lakes is 5.88, 5.14, 3.86 and 4.43, respectively. The vegetation degradation accelerates the degradation of alpine soil environment in alpine frozen soil. Copyright 2012 Springer-Verlag Berlin Heidelberg and The Author(s)

DOI: 10.1007/s12665-012-1567-5

13004073 French, H. (University of Ottawa, Departments of Geography and Earth Sciences, Ottawa, ON, Canada) and Demitroff, M. Late Pleistocene paleohydrography, eolian acitivity and frozen ground, New Jersey Pine Barrens, Eastern USA: Geologie en Mijnbouw. Netherlands Journal of Geosciences, 91(1-2), p. 25-35, illus. incl. sketch maps, 36 ref., September 2012.

The Late Pleistocene surface paleohydrography of the New Jersey Pine Barrens consisted of a series of broad braided alluvial surfaces with meandering paleochannels. This drainage is best explained in terms of impermeable (i.e. frozen) substrate, high sediment load, variable or decreasing discharge, and eolian sedimentary dynamics. Evidence for eolian activity is provided by wind-abraded sand grains, coversand, dunes, ventifacts, deflation hollows and wind-polished boulders. In several places stream avulsion occurred due to channel infilling by locally-derived wind-blown sediment. The braided and meandering river systems that characterise the tundra and polar semi-desert lowlands of the Western Canadian Arctic are described as modern analogs.

URL: http://www.njgonline.nl/publish/articles/000468/english.html

13008416 Karlsson, Johanna Mard (Stockholm University, Department of Physical Geography and Quaternary Geology, Stockholm, Sweden); Lyon, Steve W. and Destouni, Georgia. Thermokarst lake, hydrological flow and water balance indicators of permafrost change in western Siberia: Journal of Hydrology, 464-465, p. 459-466, illus. incl. 2 tables, sketch map, 42 ref., September 25, 2012.

Permafrost, mainly of discontinuous type, that underlies the tundra and taiga landscapes of the Nadym and Pur river basins in northwestern Siberia has been warming during the recent decades. A mosaic of thermokarst lakes and wetlands dominates this area. In this study we tested the hypothesis chain that permafrost thawing changes thermokarst lake area and number, and is then also reflected in and detectable through other associated hydrological changes. Based on indications from previous studies, the other hydrological changes in a basin were expected to be decreasing intra-annual runoff variability (quantified by decreasing maximum and increasing minimum runoff) and systematically decreasing water storage. To test this hypothesis chain, we mapped thermokarst lake changes using remote sensing analysis and analyzed both climate (temperature and precipitation) and water flow and balance changes using available monthly data records. This was done for the whole Nadym and Pur river basins and a smaller sub-basin of the former (denoted 7129) with comparable data availability as the whole river basins. The results for the 7129 sub-basin show all the indicators (thermokarst lake and other hydrological) changing consistently, as could be expected in response to permafrost thawing that alters the connections between surface and subsurface waters, and leads to overall decreases in water (including ground ice) storage within a basin. Over the Nadym and Pur basins, the relative area influenced by similar permafrost thawing and associated lake and hydrological effects appears (yet) too small to be clearly and systematically reflected in the basin-average indicators for these large basins.

DOI: 10.1016/j.jhydrol.2012.07.037

13004086 van Loon, A. J. (Adam Miciewicz University, Geological Institute, Poznari, Poland); Blaszkiewicz, M. and Degorski, M. The role of permafrost in shaping the late-glacial relief of northern Poland: Geologie en Mijnbouw. Netherlands Journal of Geosciences, 91(1-2), p. 223-231, illus. incl. geol. sketch map, 53 ref., September 2012.

The presence of permafrost in Poland north of the line indicating the maximum ice extent of the Vistulian (Weichselian) glaciation after retreat of the land-ice cap has been a subject of debate for a long time. Investigations in an area at the line of the maximum ice extent of the Pomeranian phase prove that permafrost existed, indeed, after the ice retreat. This conclusion is drawn on the basis of morphological data (the presence of oriented kettle holes), sedimentological data (the nature of the infilling of the kettle holes) and pedological data (permafrost-affected horizons in soil profiles). It appears that the permafrost mostly developed in the ice-free zone that appeared after the retreat of the land-ice cap, but it is likely that some relict permafrost that had originated earlier in front of advancing ice was also still present. The landscape of northern Poland owes its relief partly to the Late Glacial permafrost.

URL: http://www.njgonline.nl/publish/articles/000481/english.html

13004090 Vandenberghe, J. (Vrije Universiteit, Institute of Earth Sciences, Amsterdam, Netherlands). Multi-proxy analysis; a reflection on essence and potential pitfalls: Geologie en Mijnbouw. Netherlands Journal of Geosciences, 91(1-2), p. 263-269, illus., 39 ref., September 2012.

Multi-disciplinarity and multi-proxy approaches are necessary to understand the processes in complex earth systems. However, unlimited and uncontrolled multi-proxy-correlations may be risky. A number of case studies illustrate the potential pitfalls when the processes that drive the individual proxies have no common causal significance or dating is not precise enough. Crossing thresholds at different levels and delay times may also be factors that hamper direct correlations of proxies. Multi-proxy analysis of the intrinsic relationships between proxies in a system is the primary task before any correlation should be made.

URL: http://www.njgonline.nl/publish/articles/000485/english.html

13008258 Andersson, Rina Argelia (Stockholm University, Department of Geological Sciences and Quaternary Geology, Stockholm, Sweden); Meyers, Philip; Hornibrook, Edward; Kuhry, Peter and Mörth, Carl-Magnus. Elemental and isotopic carbon and nitrogen records of organic matter accumulation in a Holocene permafrost peat sequence in the East European Russian Arctic: JQS. Journal of Quaternary Science, 27(6), p. 545-552, illus. incl. sketch map, 58 ref., August 2012.

A peat deposit from the East European Russian Arctic, spanning nearly 10 000 years, was investigated to study soil organic matter degradation using analyses of bulk elemental and stable isotopic compositions and plant macrofossil remains. The peat accumulated initially in a wet fen that was transformed into a peat plateau bog following aggradation of permafrost in the late Holocene (~2500 cal a BP). Total organic carbon and total nitrogen (N) concentrations are higher in the fen peat than in the moss-dominated bog peat layers. Layers in the sequence that have lower concentrations of total hydrogen (H) are associated with degraded vascular plant residues. C/N and H/C atomic ratios indicate better preservation of organic matter in peat material dominated by bryophytes as opposed to vascular plants. The presence of permafrost in the peat plateau stage and water-saturated conditions at the bottom of the fen stage appear to lead to better preservation of organic plant material. d¹⁵N values suggest N isotopic fractionation was driven primarily by microbial decomposition whereas differences in d¹³C values appear to reflect mainly changes in plant assemblages. Positive shifts in both d¹⁵N and d¹³C values coincide with a local change to drier conditions as a result of the onset of permafrost and frost heave of the peat surface. This pattern suggests that permafrost aggradation not only resulted in changes in vegetation but also aerated the underlying fen peat, which enhanced microbial denitrification, causing the observed ¹⁵N-enrichment. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1002/jqs.2541

13008261 Leng, Melanie J. (University of Leicester, Department of Geology, Leicester, United Kingdom); Wagner, Bernd; Anderson, N. John; Bennike, Ole; Woodley, Ewan and Kemp, Simon J. Deglaciation and catchment ontogeny in coastal south-west Greenland; implications for terrestrial and aquatic carbon cycling: JQS. Journal of Quaternary Science, 27(6), p. 575-584, illus. incl. sketch map, 63 ref., August 2012.

Here we present Holocene organic carbon, nitrogen, sulphur, carbon isotope ratio and macrofossil data from a small freshwater lake near Sisimiut in southwest Greenland. The lake was formed c. 11 cal ka BP following retreat of the ice sheet margin and is located above the marine limit in this area. The elemental and isotope data suggest a complex deglaciation history of interactions between the lake and its catchment, reflecting glacial retreat and post-glacial hydrological flushing probably due to periodic melting of local remnant glacial ice and firn areas between 11 and 8.5 cal ka BP. After 8.5 cal ka BP, soil development and associated vegetation processes began to exert a greater control on terrestrial-aquatic carbon cycling. By 5.5 cal ka BP, in the early Neoglacial cooling, the sediment record indicates a change in catchment-lake interactions with consistent d¹³C while C/N exhibits greater variability. The period after 5.5 cal ka BP is also characterized by higher organic C accumulation in the lake. These changes (total organic carbon, C/N, d¹³C) are most likely the result of increasing contribution (and burial) of terrestrial organic matter as a result of enhanced soil instability, as indicated by an increase in Cenococcum remains, but also Sphagnum and Empetrum. The impact of glacial retreat and relatively subdued mid- to late Holocene climate variation at the coast is in marked contrast to the greater environmental variability seen in inland lakes closer to the present-day ice sheet margin. Copyright 2012 John Wiley & Sons, Ltd. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1002/jqs.2544

13002133 Mangold, N. (Université Nantes, Laboratoire Planétologie et Géodynamique de Nantes, Nantes, France); Kite, E. S.; Kleinhans, M. G.; Newsom, H.; Ansan, V.; Hauber, E.; Kraal, E.; Quantin, C. and Tanaka, K. The origin and timing of fluvial activity at Eberswalde Crater, Mars: Icarus, 220(2), p. 530-551, illus. incl. 1 table, sketch maps, 154 ref., August 2012.

The fan deposit in Eberswalde crater has been interpreted as strong evidence for sustained liquid water on early Mars with a paleolake formed during the Noachian period (>3.7 Gy). This location became a key region for understanding the Mars paleo-environment. Eberswalde crater is located 50 km north of the rim of the 150 km diameter crater Holden. Stratigraphic relationships and chronology obtained using recent Mars Express High Resolution Stereo Camera and Mars Reconnaissance Orbiter Context Camera images show that Eberswalde fluvial activity crosscuts Holden ejecta and thus postdates Holden crater, whose formation age is estimated from crater counts as Late Hesperian (~3.5 Gy, depending on models). Fluvial modeling shows that short term activity (over several years to hundreds of years) involving dense flows (with sediment:water ratio between 0.01 and 0.3) may be as good an explanation of the fluvial landforms as dilute flow over longer durations. Modeling of the thermal effect of the Holden impact in the Eberswalde watershed is used to evaluate its potential role in aqueous activity. The relative timing of the Holden impact and Eberswalde's fan is a constraint for future studies about the origin of these landforms. Holden ejecta form a weak and porous substrate, which may be easy to erode by fluvial incision. In a cold climate scenario, impact heating could have produced runoff by melting snow or ground ice. Any attempt to model fluvial activity at Eberswalde should take into account that it may have formed as late as in the Late Hesperian, after the great majority of valley network formation and aqueous mineralization on Mars. This suggests that hypotheses for fan formation at Eberswalde by transient and/or localized processes (i.e. impact, volcanism, unusual orbital forcing) should be considered on a par with globally warmer climate.

DOI: 10.1016/j.icarus.2012.05.026

13002143 Schorghofer, Norbert (University of Hawaii, Institute for Astronomy, Honolulu, HI) and Forget, François. History and anatomy of subsurface ice on Mars: Icarus, 220(2), p. 1112-1120, illus. incl. 1 table, 63 ref., August 2012.

Ice buried beneath a thin layer of soil has been revealed by neutron spectroscopy and explored by the Phoenix Mars Lander. It has also been exposed by recent impacts. This subsurface ice is thought to lose and gain volume in response to orbital variations (Milankovitch cycles). We use a powerful numerical model to follow the growth and retreat of near-surface ice as a result of regolith-atmosphere exchange continuously over millions of years. If a thick layer of almost pure ice has been deposited recently, it has not yet reached equilibrium with the atmospheric water vapor and may still remain as far equatorward as 43°N, where ice has been revealed by recent impacts. A potentially observable consequence is present-day humidity output from the still retreating ice. We also demonstrate that in a sublimation environment, subsurface pore ice can accumulate in two ways. The first mode, widely known, is the progressive filling of pores by ice over a range of depths. The second mode occurs on top of an already impermeable ice layer; subsequent ice accumulates in the form of pasted on horizontal layers such that beneath the ice table, the pores are completely full with ice. Most or all of the pore ice on Mars today may be of the second type. At the Phoenix landing site, where such a layer is also expected to exist above an underlying ice sheet, it may be extremely thin, due to exceptionally small variations in ice stability over time.

DOI: 10.1016/j.icarus.2012.07.003

13008246 Mukhopadhyay, Sujoy (Harvard University, Department of Earth and Planetary Sciences, Cambridge, MA); Ackert, Robert P.; Pope, Allen E.; Pollard, David and DeConto, Robert M. Miocene to recent ice elevation variations from the interior of the West Antarctic ice sheet; constraints from geologic observations, cosmogenic nuclides and ice sheet modeling: Earth and Planetary Science Letters, 337-338, p. 243-251, illus. incl. 2 tables, sketch map, 41 ref., July 1, 2012. Supplementary data available in online version.

Observations of long-term West Antarctic Ice Sheet (WAIS) behavior can be used to test and constrain dynamic ice sheet models. Long-term observational constraints are however, rare. Here we present the first constraints on long-term (Miocene-Holocene) WAIS elevation from the interior of the ice sheet near the WAIS divide. We use geologic observations and measurements of cosmogenic ²¹Ne and ¹⁰Be in bedrock surfaces to constrain WAIS elevation variations to <160 m above the present-day ice levels since 7 Ma, and <110 m above present-day ice levels since 5.4 Ma. The cosmogenic nuclide data indicate that bedrock surfaces 35 m above the present-day ice levels had near continuous exposure over the past 3.5 Ma, requiring average interior WAIS elevations to have been similar to, or lower than present, since the beginning of the Pliocene warm period. We use a continental ice sheet model to simulate the history of ice cover at our sampling sites and thereby compute the expected concentration of the cosmogenic nuclides. The ice sheet model indicates that during the past 5 Ma interior WAIS elevations of >65 m above present-day ice levels at the Ohio Range occur only rarely during brief ice sheet highstands, consistent with the observed cosmogenic nuclide data. Furthermore, the model's prediction that highstand elevations have increased on average since the Pliocene is in good agreement with the cosmogenic nuclide data that indicate the highest ice elevation over the past 5 Ma was reached during the highstand at 11 ka. Since the simulated cosmogenic nuclide concentrations derived from the model's ice elevation history are in good agreement with our measurements, we suggest that the model's prediction of more frequent collapsed-WAIS states and smaller WAIS volumes during the Pliocene are also correct.

DOI: 10.1016/j.epsl.2012.05.015

13003589 Angert, Alon (Hebrew University of Jerusalem, Institute of Earth Sciences, Jerusalem, Israel); Rodeghiero, Mirco and Griffin, Kevin. High alternative oxidase activity in cold soils and its implication to the Dole effect: Geophysical Research Letters, 39(16), Citation L16710, illus. incl. 2 tables, 32 ref., 2012.

Variations in the Dole Effect, which have been used to infer past changes in biospheric productivity, are strongly affected by isotopic discrimination in soil respiration. Respiration through the alternative oxidase (AOX) pathway is associated with a higher discrimination than the one associated with the "normal" dark respiration pathway (the cytochrome pathway, COX). However, observations of O₂ discrimination and AOX activity in undisturbed natural environments are scarce. In the current study we measured the O₂ concentration and stable isotopes in the root zone of tundra, boreal forest and alpine forest soils. To estimate the discrimination from this data, we have performed O₂ diffusion experiments in gamma-sterilized soil columns, with varying soil clay content. The discrimination found in the diffusion experiments was independent of clay content, and the value found, 14 ± 2ppm, is the same as the one for binary diffusion of O₂ in N₂, indicating no interaction between the O₂ and clay particles. Based on the field and laboratory results, the respiratory discrimination in the soils studied is 15-31 ppm, with the higher values associated with colder soils. The high discrimination found for cold (<6°C) soils indicates that AOX is a major respiratory pathway in these soils. This relationship between soil temperature and discrimination can be used in future interpretations of Dole Effect variations.

DOI: 10.1029/2012GL052719

13003579 Arp, C. D. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Jones, B. M.; Lu, Z. and Whitman, M. S. Shifting balance of thermokarst lake ice regimes across the Arctic Coastal Plain of northern Alaska: Geophysical Research Letters, 39(16), Citation L16503, illus. incl. sketch maps, 28 ref., 2012. Supplemental information/data is available in the online version of this article.

The balance of thermokarst lakes with bedfast- and floating-ice regimes across Arctic lowlands regulates heat storage, permafrost thaw, winter-water supply, and over-wintering aquatic habitat. Using a time-series of late-winter synthetic aperture radar (SAR) imagery to distinguish lake ice regimes in two regions of the Arctic Coastal Plain of northern Alaska from 2003-2011, we found that 18% of the lakes had intermittent ice regimes, varying between bedfast-ice and floating-ice conditions. Comparing this dataset with a radar-based lake classification from 1980 showed that 16% of the bedfast-ice lakes had shifted to floating-ice regimes. A simulated lake ice thinning trend of 1.5 cm/yr since 1978 is believed to be the primary factor driving this form of lake change. The most profound impacts of this regime shift in Arctic lakes may be an increase in the landscape-scale thermal offset created by additional lake heat storage and its role in talik development in otherwise continuous permafrost as well as increases in over-winter aquatic habitat and winter-water supply.

DOI: 10.1029/2012GL052518

13003564 Brothers, Laura L. (U. S. Geological Survey, Woods Hole, MA); Hart, Patrick E. and Ruppel, Carolyn D. Minimum distribution of subsea ice-bearing permafrost on the U.S. Beaufort Sea continental shelf: Geophysical Research Letters, 39(15), Citation L15501, illus. incl. sketch map, 20 ref., 2012.

Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s^-1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ~5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

DOI: 10.1029/2012GL052222

13008163 Gaal, Ladislav (Slovak University of Technology, Faculty of Civil Engineering, Bratislava, Slovak Republic); Szolgay, Jan; Kohnova, Silvia; Parajka, Juraj; Merz, Ralf; Viglione, Alberto and Blöschl, Günter. Flood timescales; understanding the interplay of climate and catchment processes through comparative hydrology: Water Resources Research, 48(4), Citation W04511, illus. incl. 4 tables, 60 ref., 2012. Includes appendices.

We analyze the controls on flood duration based on the concept of comparative hydrology. Rather than modeling a single catchment in detail, we compare catchments with contrasting characteristics in order to understand the controls in a holistic way. We analyze the hydrographs of 9223 maximum annual flood events in 396 Austrian catchments ranging from 5 to ~10,000 km² as a function of climatic controls such as storm type (synoptic and convective storms, rain-on-snow, snowmelt), and catchment controls such as soils, soil moisture, geology, and land form. The ratio of the flood volume and the flood peak is used as a measure of the flood duration or flood timescale. The results indicate that, spatially, the median flood timescales range from 16 h in the hilly catchments, where convective storms prevail, to 104 h in the lowland catchments where substantial inundation into the floodplain occurs. The range is even larger for different flood types, from 7 h for flash floods in the hilly catchments to 200 h for snowmelt floods in an Alpine area with deeply weathered rocks and deep soils. The results also indicate that the catchment area is not the most important control on the flood timescales. For the range of catchments considered here, climate is very important through storm type and antecedent soil moisture, and geology is very important through soil characteristics. The concept of comparative hydrology is also used to interpret the interplay of the processes controlling the flood duration at timescales from hours to millennia. It is argued that the flood timescale is a rich fingerprint of the hydrological processes in a catchment because it integrates a range of climate and catchment characteristics by a time parameter.

DOI: 10.1029/2011WR011509

13003566 Harden, Jennifer W. (U. S. Geological Survey, Menlo Park, CA); Koven, Charles D.; Ping, Chien-Lu; Hugelius, Gustaf; McGuire, A. David; Camill, Phillip; Jorgenson, Torre; Kuhry, Peter; Michaelson, Gary J.; O'Donnell, Jonathan A.; Schuur, Edward A. G.; Tarnocai, Charles; Johnson, Kristopher and Grosse, Guido. Field information links permafrost carbon to physical vulnerabilities of thawing: Geophysical Research Letters, 39(15), Citation L15704, illus. incl. 1 table, 55 ref., 2012. Supplemental information/data is available in the online version of this article.

Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3 m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems.

DOI: 10.1029/2012GL051958

13008174 Rössler, Ole (Oeschger Centre for Climate Change Research, Institute of Geography, Bern, Switzerland); Diekkrüger, Bernd and Löffler, Jörg. Potential drought stress in a Swiss mountain catchment; ensemble forecasting of high mountain soil moisture reveals a drastic decrease, despite major uncertainties: Water Resources Research, 48(4), Citation W04521, illus. incl. 7 tables, 106 ref., 2012.

Climate change is expected to profoundly influence the hydrosphere of mountain ecosystems. The focus of current process-based research is centered on the reaction of glaciers and runoff to climate change; spatially explicit impacts on soil moisture remain widely neglected. We spatio-temporally analyzed the impact of the climate on soil moisture in a mesoscale high mountain catchment to facilitate the development of mitigation and adaptation strategies at the level of vegetation patterns. Two regional climate models were downscaled using three different approaches (statistical downscaling, delta change, and direct use) to drive a hydrological model (WaSiM-ETH) for reference and scenario period (1960-1990 and 2070-2100), resulting in an ensemble forecast of six members. For all ensembles members we found large changes in temperature, resulting in decreasing snow and ice storage and earlier runoff, but only small changes in evapotranspiration. The occurrence of downscaled dry spells was found to fluctuate greatly, causing soil moisture depletion and drought stress potential to show high variability in both space and time. In general, the choice of the downscaling approach had a stronger influence on the results than the applied regional climate model. All of the results indicate that summer soil moisture decreases, which leads to more frequent declines below a critical soil moisture level and an advanced evapotranspiration deficit. Forests up to an elevation of 1800 m a.s.l. are likely to be threatened the most, while alpine areas and most pastures remain nearly unaffected. Nevertheless, the ensemble variability was found to be extremely high and should be interpreted as a bandwidth of possible future drought stress situations.

DOI: 10.1029/2011WR011188

13007068 Velicogna, I. (University of California, Irvine, Department of Earth System Science, Irvine, CA); Tong, J.; Zhang, T. and Kimball, J. S. Increasing subsurface water storage in discontinuous permafrost areas of the Lena River basin, Eurasia, detected from GRACE: Geophysical Research Letters, 39(9), Citation L09403, illus. incl. sketch map, 40 ref., 2012.

We use monthly measurements of time-variable gravity from the GRACE (Gravity Recovery and Climate Experiment) satellite mission to quantify changes in terrestrial water storage (TWS) in the Lena river basin, Eurasia, during the period April 2002 to September 2010. We estimate a TWS increase of 32 ± 10 km³/yr for the entire basin, equivalent to an increase in water thickness of 1.3 ± 0.4 cm/yr over a basin of 2.4 million km². We compare TWS estimates from GRACE with time series of precipitation (P) minus evapotranspiration (ET) from ERA-Interim reanalysis minus observational river discharge (R). We find an excellent agreement in annual and inter-annual variability between the two time series. Furthermore, we find that a bias of -20 ± 10% in P-ET is sufficient to effectively close the water budget with GRACE. When we account for this bias, the time series of cumulative TWS from GRACE and climatological data agree to within ±3.8 cm of water thickness, or ±9% of the mean annual P. The TWS increase is not uniform across the river basin and exhibits a peak, over an area of 502,400 km², centered at 118.5°E, 62.5°N, and underlain by discontinuous permafrost. In this region, we attribute the observed TWS increase of 68 ± 19 km³ to an increase in subsurface water storage. This large subsurface water signal will have a significant impact on the terrestrial hydrology of the region, including increased baseflow and alteration of seasonal runoff.

DOI: 10.1029/2012GL051623

13006490 Berthling, Ivar (Norwegian University of Science and Technology, Department of Geography, Trondheim, Norway). Beyond confusion; rock glaciers as cryo-conditioned landforms: Geomorphology, 131(3-4), p. 98-106, illus., 99 ref., August 15, 2011.

Whether rock glaciers are permafrost creep features or may also be related to glaciers in non-permafrost environments, and whether they should be defined by genesis or appearance, have caused heated debate for several decades. This paper analyses the rock glacier debate from a theoretical viewpoint, in order to highlight and discuss underlying problems and with the aim of providing a common conceptual framework from which to proceed. It is suggested that the morphological rock glacier definition should be abandoned. A new genetic definition is proposed where permafrost is the primary condition, but where the deforming ice/debris may be of both glacial and periglacial origin. Abstract Copyright (2011) Elsevier, B.V.

DOI: 10.1016/j.geomorph.2011.05.002

13007788 Schirrmeister, L. (Alfred Wegener Institute for Polar and Marine Research, Periglacial Research, Potsdam, Germany); Kunitsky, V.; Grosse, G.; Wetterich, S.; Meyer, H.; Schwamborn, G.; Babiy, O.; Derevyagin, A. and Siegert, C. Sedimentary characteristics and origin of the late Pleistocene Ice Complex on north-east Siberian Arctic coastal lowlands and islands; a review: in Timing and vegetation history of past interglacials in northern Eurasia (Frechen, Manfred, editor), Quaternary International, 241(1-2), p. 3-25, illus. incl. sects., 5 tables, sketch map, 128 ref., August 15, 2011.

The origin of Late Pleistocene ice-rich, fine-grained permafrost sequences (Ice Complex deposits) in arctic and subarctic Siberia has been in dispute for a long time. Corresponding permafrost sequences are frequently exposed along seacoasts and river banks in Yedoma hills, which are considered to be erosional remnants of Late Pleistocene accumulation plains. Detailed cryolithological, sedimentological, geochronological, and stratigraphical results from 14 study sites along the Laptev and East Siberian seacoasts were summarized for the first time in order to compare and correlate the local datasets on a large regional scale. The sediments of the Ice Complex are characterized by poorly-sorted silt to fine-sand, buried cryosols, TOC contents of 1.2-4.8 wt%, and very high ground ice content (40-60 wt% absolute). A second large constituent of the Ice Complex are large syngenetic ice wedges, resulting in a total ice content of the Ice Complex of up to 80 vol%. Ice Complex deposits were mostly formed during the Middle Weichselian interstadial and/or during the Late Weichselian stadial periods. A conceptual model of nival lithogenesis of Ice Complex deposits was developed that integrates various other formation hypotheses. A combination of various local and regional paleogeographical, geological, and paleoclimate conditions controlled the formation of Ice Complex sequences during the Late Pleistocene in northern East Siberia. They are chronologically and stratigraphically, but not genetically equivalent to Eurasian and Alaskan loess deposits.

DOI: 10.1016/j.quaint.2010.04.004

13002997 Lang, Stefan (University of Salzburg, Centre for Geoinformatics, Salzburg, Austria); Kaab, Andreas; Pechstädt, J.; Flügel, Wolfgang-Albert; Zeil, P.; Lanz, E.; Kahuda, D.; Frauenfelder, R.; Casey, K.; Füreder, P.; Sossna, I.; Wagner, I.; Janauer, G.; Exler, N.; Boukalova, Z.; Tapa, R.; Lui, J. and Sharma, N. Assessing components of the natural environment of the upper Danube and upper Brahmaputra River basins: in BRAHMATWINN results (Flügel, Wolfgang-Albert, editor), Advances in Science and Research, 7, p. 21-36, illus. incl. 9 tables, sketch maps, 22 ref., 2011. Accessed in June, 2012.

A comprehensive understanding of the interplay between the natural environment and the human dimension is one of the prerequisites to successful and sustaining IWRM practices in large river basins such as the Upper Brahmaputra river basin or the Upper Danube river basin. These interactions, their dynamics and changes, and the likely future scenarios were investigated in the BRAHMATWINN project with a series of tools from remote sensing and geoinformatics. An integrated assessment of main components of the natural environment in the two river basins as well as in five reference catchments within those basins, has led to the delineation of hydrological response units (HRUs). HRUs are spatial units bearing a uniform behaviour in terms of the hydrological response regime, as a function of physical parameters land use, soil type, water, vegetation cover and climate. Besides the delineated HRUs which are available in a spatially exhaustive manner for all reference catchments, the following information were provided as spatial layers: (1) uniform digital surface models of both the twinned basins and the reference catchments; (2) glacier areas and the magnitude of glacier loss; (3) mountain permafrost distribution and identification of areas particularly affected by permafrost thaw; (4) a consistent land use/land cover information in all reference catchments; and (5) the vulnerabilities of wetlands and groundwater in terms of anthropogenic impact and climate change.

DOI: 10.5194/asr-7-21-2011

13007885 Mugnuolo, Raffaele (Italian Space Agency, Italy). Is there water on Mars?: Hydrolink, 49(4, SUPPL.), p. 52-54, illus., 2011.

13002804 Konz, Nadine (University of Basel, Institute of Environmental Geosciences, Basel, Switzerland); Baenninger, D.; Konz, Markus; Nearing, Mark and Alewell, Christine. Process identification of soil erosion in steep mountain regions: Hydrology and Earth System Sciences (HESS), 14(4), p. 675-686, illus. incl. 4 tables, sketch maps, 34 ref., 2010. Published in Hydrology and Earth System Sciences Discussion: 9 March 2009, URL: http://www.hydrol-earth-syst-sci-discuss.net/6/2153/2009/hessd-6-2153-20 09.html; accessed in Feb., 2012.

Mountainous soil erosion processes were investigated in the Urseren Valley (Central Switzerland) by means of measurements and simulations. The quantification of soil erosion was performed on hill slope scale (2.20 m) for three different land use types: hayfields, pastures with dwarf shrubs and pastures without dwarf shrubs with three replicates each. Erosion rates during growing season were measured with sediment traps between June 2006 and November 2007. Long-term soil erosion rates were estimated based on Cs-137 redistribution. In addition, soil moisture and surface flow were recorded during the growing season in the field and compared to model output. We chose the WEPP model (Water Erosion Prediction Project) to simulate soil erosion during the growing season. Model parameters were determined in the field (slope, plant species, fractional vegetation cover, initial saturation level), by laboratory analyses (grain size, organic matter) and by literature study. The WEPP model simulates sheet erosion processes (interrill and splash erosion processes, please note that no rill erosion occurs at our sites). Model output resulted in considerable smaller values than the measured erosion rates with sediment traps for the same period. We attribute the differences to observed random gravity driven erosion of soil conglomerates. The Cs-137 measurements deliver substantially higher mean annual erosion rates, which are most likely connected to snow cover related processes such as snow gliding and avalanche activities.

URL: http://www.hydrol-earth-syst-sci.net/14/675/2010/hess-14-675-2010.pdf

13002809 Zhang, Yinsuo (Carleton University, Department of Geography and Environmental Studies, Ottawa, ON, Canada); Carey, Sean K.; Quinton, William L.; Janowicz, J. Richard; Pomeroy, John W. and Flerchinger, Gerald N. Comparison of algorithms and parameterisations for infiltration into organic-covered permafrost soils: Hydrology and Earth System Sciences (HESS), 14(5), p. 729-750, illus. incl. 7 tables, 91 ref., 2010. Includes appendix; part of special issue no. 105, Cold region hydrology: improved processes, parameterization and prediction. edited by Carey, S., et al., URL: http://www.hydrol-earth-syst-sci.net/special_issue105.html; published in Hydrology and Earth System Sciences Discussion: 4 September 2009, URL: http://www.hydrol-earth-syst-sci-discuss.net/6/5705/2009/hessd-6-5705-20 09.html; accessed in Feb., 2012.

Infiltration into frozen and unfrozen soils is critical in hydrology, controlling active layer soil water dynamics and influencing runoff. Few Land Surface Models (LSMs) and Hydrological Models (HMs) have been developed, adapted or tested for frozen conditions and permafrost soils. Considering the vast geographical area influenced by freeze/thaw processes and permafrost, and the rapid environmental change observed worldwide in these regions, a need exists to improve models to better represent their hydrology. In this study, various infiltration algorithms and parameterisation methods, which are commonly employed in current LSMs and HMs were tested against detailed measurements at three sites in Canada's discontinuous permafrost region with organic soil depths ranging from 0.02 to 3 m. Field data from two consecutive years were used to calibrate and evaluate the infiltration algorithms and parameterisations. Important conclusions include: (1) the single most important factor that controls the infiltration at permafrost sites is ground thaw depth, (2) differences among the simulated infiltration by different algorithms and parameterisations were only found when the ground was frozen or during the initial fast thawing stages, but not after ground thaw reaches a critical depth of 15 to 30 cm, (3) despite similarities in simulated total infiltration after ground thaw reaches the critical depth, the choice of algorithm influenced the distribution of water among the soil layers, and (4) the ice impedance factor for hydraulic conductivity, which is commonly used in LSMs and HMs, may not be necessary once the water potential driven frozen soil parameterisation is employed. Results from this work provide guidelines that can be directly implemented in LSMs and HMs to improve their application in organic covered permafrost soils.

URL: http://www.hydrol-earth-syst-sci.net/14/729/2010/hess-14-729-2010.pdf

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13005866 Olefeldt, David. Quantity and composition of waterborne carbon transport in subarctic catchments containing peatlands and permafrost: 167 p., Doctoral, 2011, McGill University, Montreal, QC, Canada. ISBN: 978-0-494-775363 Available from: Univ. Microfilms.

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13003313 Layzell, Anthony (University of Kansas, Department of Geography, Lawrence, KS) and Eppes, Martha Cary. The effect of remnant glacial topography on Holocene alluvial forms and processes in the San Juan Mountains, southern Colorado [abstr.]: in AMQUA 2012, American Quaternary Association 22^nd biennial meeting, 2012, program and abstracts; From floods to droughts; water, climate variability, and their impacts in the Holocene, Program and Abstracts - American Quaternary Association. Conference, 22, p. 80, June 2012. WWW. Meeting: AMQUA 2012, American Quaternary Association 22^nd biennial meeting, June 21-25, 2012, Duluth, MN.

URL: http://www.cce.umn.edu/Documents/CPE-Conferences/2012AMQUAProgramAbstractsBook.p ...

13003315 Loope, Henry M. (University of Wisconsin at Madison, Department of Geography, Madison, WI); Mason, Joseph A.; Knox, James; Goble, Ronald J.; Hanson, Paul R. and Young, Aaron R. Late Wisconsinan eolian sand activity in the upper Mississippi River basin [abstr.]: in AMQUA 2012, American Quaternary Association 22^nd biennial meeting, 2012, program and abstracts; From floods to droughts; water, climate variability, and their impacts in the Holocene, Program and Abstracts - American Quaternary Association. Conference, 22, p. 82, June 2012. WWW. Meeting: AMQUA 2012, American Quaternary Association 22^nd biennial meeting, June 21-25, 2012, Duluth, MN.

URL: http://www.cce.umn.edu/Documents/CPE-Conferences/2012AMQUAProgramAbstractsBook.p ...

13003329 Murphy, Laura R. (University of Kansas, Kansas Geological Survey, Lawrence, KS); Hurst, Stance C.; Holliday, Vance T.; Johnson, Eileen and Sanderson, Bridget. The late Quaternary plant communities of the Caprock Canyonlands ecotone; multiple proxy paleoenvironmental data from two draws on the eastern escarpment of the southern High Plains of Texas, U.S.A. [abstr.]: in AMQUA 2012, American Quaternary Association 22^nd biennial meeting, 2012, program and abstracts; From floods to droughts; water, climate variability, and their impacts in the Holocene, Program and Abstracts - American Quaternary Association. Conference, 22, p. 96, June 2012. WWW. Meeting: AMQUA 2012, American Quaternary Association 22^nd biennial meeting, June 21-25, 2012, Duluth, MN.

URL: http://www.cce.umn.edu/Documents/CPE-Conferences/2012AMQUAProgramAbstractsBook.p ...

13002001 Gierek, C. G. (New Mexico Institute of Mining and Technology, Department of Earth and Environmental Science, Socorro, NM) and Newton, B. T. How trees interact with their environment; a stable isotope study [abstr.]: in New Mexico Geological Society spring meeting, New Mexico Geology, 34(2), p. 51-52, May 2012. Meeting: New Mexico Geological Society spring meeting, April 27, 2012, Socorro, NM.

13006759 Boyce, J. M. (University of Hawai'i at Manoa, Hawaii Institute of Geophysics and Planetology, Honolulu, HI); Barlow, N. G. and Wilson, L. Model for the emplacement of the outer ejecta layer of low aspect-ratio layer ejecta craters by turbulent flow: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 1081, illus., 15 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on Sept. 26, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1081.pdf

13003148 Conway, S. J. (Université de Nantes, Laboratoire de Planétologie et Géodynamique de Nantes, Nantes, France); Mangold, N.; Balme, M. R. and Ansan, V. Comparison of the morphology of crater-slopes with gullies to those without gullies: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2281, illus. incl. sketch map, 8 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 27, 2012.

www.lpi.usra.edu/meetings/lpsc2012/pdf/2281.pdf

13003160 Dundas, C. M. (U. S. Geological Survey, Astrogeology Science Center, Flagstaff, AZ) and Keszthelyi, L. P. Modeling of steam pressure under Martian lava flows: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2554, illus., 18 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 27, 2012.

www.lpi.usra.edu/meetings/lpsc2012/pdf/2554.pdf

13006881 Levy, Joseph S. (Oregon State University, College of Earth, Ocean, and Atmospheric Science, Corvallis, OR); Fountain, Andrew G.; Nylen, Thomas L.; Head, James W., III and Dickson, James L. Rapid growth and decay of Mars-analog gullies in buried ice and sediment-rich substrates; new views of gullies as disequilibrium landforms in Garwood Valley, Antarctica: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 1100, illus., 16 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on Oct. 18, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/1100.pdf

13003170 Mege, D. (Polish Academy of Sciences, Institute of Geological Sciences, WROONA Group, Wroclaw, Poland); Purcell, P. G. and Jourdan, F. Dikes and linear troughs; new observations on the Somali Plate: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 1317, illus. incl. geol. sketch map, 14 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 30, 2012.

www.lpi.usra.edu/meetings/lpsc2012/pdf/1317.pdf

13000556 Mercier, Dave (Virginia Polytechnic Institute and State University, Department of Geosciences, Blacksburg, VA) and Lowell, Robert P. Ice melting above a convecting, crystallizing magmatic sill on Mars: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2275, illus., 10 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 6, 2012.

www.lpi.usra.edu/meetings/lpsc2012/pdf/2275.pdf

13006884 Pina, P. (Instituto Superior Tecnico, Centro de Recursos Naturais e Ambiente, Lisbon, Portugal); Vieira, G.; Christiansen, H. H.; Barata, M. T.; Oliva, M.; Neves, M.; Bandeira, L.; Lousada, M.; Jorge, M. and Saraiva, J. Analog studies of ice-wedge polygons in Svalbard; 2011 field campaign, topology and geometry: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2353, 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on Oct. 18, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2353.pdf

13006927 Rask, J. C. (Dynamac Corporation, Space Biosciences Division, Moffett Field, CA); De Leon, P.; Marinova, M. M. and McKay, C. P. The exploration of Marambio Antarctica as a Mars analog: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2455, illus. incl. sketch map, 7 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on Oct. 23, 2012.

URL: http://www.lpi.usra.edu/meetings/lpsc2012/pdf/2455.pdf

13003093 Retherford, K. D. (Southwest Research Institute, San Antonio, TX); Davis, M. W.; Winters, G. S.; Patrick, E. L.; Escobedo, S. M.; Nagengast, M. E.; Gladstone, G. R.; Miles, P. F.; Parker, J. W.; Stern, S. A. and Hendrix, A. R. Lunar Ultraviolet Reflectance Experiment (LURE); far-UV signatures of water ice: in Lunar and planetary science conference XLIII; papers presented to the Forty-third lunar and planetary science conference, Abstracts of Papers Submitted to the Lunar and Planetary Science Conference, 43, Abstract 2190, illus., 7 ref., 2012. Meeting: Forty-third lunar and planetary science conference, March 19-23, 2012, Woodlands, TX. Accessed on July 20, 2012.

www.lpi.usra.edu/meetings/lpsc2012/pdf/2190.pdf

13001850 Anderson, L. S. (Institute of Arctic and Alpine Research, Boulder, CO) and Anderson, R. S. Contributions of sub-debris melt and ice face retreat to the rapid deflation of the debris-covered Kennicott Glacier terminus, Wrangell Mountains, Alaska [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C13A-0721, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

Debris covered glaciers are common in tectonically active or highly erodible ranges such as the Himalaya, Tien Shan, Alps, Southern Alps, and the Wrangell Mountains. Debris cover has a variable effect on the mass balance profile depending on its thermal conductivity, albedo, and thickness. Although debris cover generally reduces melt, melt within debris covered zones is complicated by the presence of bare ice faces which retreat at high rates relative to melt beneath debris. As the need to extrapolate individual glacier mass balance into regional trends grows under a changing climate and rising sea level, it is imperative that we develop a full understanding of the factors that alter glacier mass balance, in this case: debris-cover and ice face retreat. In order to understand the influence of debris-cover on the retreat and deflation of glaciers, we completed a field campaign on the 43km long Kennicott Glacier in south-central Alaska from June to mid-August 2011. This valley glacier supports a 26km² debris-covered terminus with a high concentration of exposed ice faces relative to other debris covered glaciers. The debris covered zone exhibits extensive thermokarst and the distribution of ice cliffs is influenced by the presence of large sinuous supraglacial streams. Previous laser altimetry research on Kennicott glacier reveals that surface elevations have decreased in the debris-covered terminus at a rate of 0.34m/yr (1957-2000), and Precipitation-Temperature Area Altitude modeling shows monotonic ice loss from 1957-2008. Rapid deflation in the debris-covered terminus is likely the result of reduced ice advection from up glacier or increased melt in the debris-covered portion of the glacier over the last half century. As a first step to understanding this rapid surface elevation reduction, we document melt beneath debris of variable thickness at 60 locations using ablation stakes, the horizontal retreat of 62 ice faces, and debris depth and surface temperature at 200 sites in the debris covered zone. We collected air temperature at three locations and temperature profiles through the debris at eight locations. We will document the orientation and concentration of ice faces using IKONOS imagery and then use a positive degree melt method with these temperature measurements to determine the contributions of melt beneath debris and ice face retreat to the total melt at the terminus. Debris surface temperature data will be used to validate 30m resolution Landsat infrared data for the Kennicott Glacier and provide a necessary check on the infrared imagery often used in debris-covered glacier research. Thermal conductivity, derived from our profiles of temperature through the debris, in conjunction with our debris thickness data will be used to model the melt produced under the debris covered terminus of the glacier and be compared to our empirical results. In further research, we will employ the feature tracking method to reveal spatial and temporal changes in advection and its effect on the elevation and extent of the debris-covered terminus of the Kennicott Glacier.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001897 Chen, M. (Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos, NM); Rowland, J. C.; Wilson, C. J.; Altmann, G. and Brumby, S. P. Temporal and spatial patterns in thermokarst lake area change in Yukon Flats, Alaska; an indication of permafrost degradation [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21B-0468, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

The formation, expansion, and drainage of thermokarst lakes is determined by the lateral and vertical degradation of permafrost. Consequently, areal changes in thermokarst lakes can reflect changes in the spatial distribution and depth of permafrost. However, natural variability in lake areas confounds the long term trend and makes it difficult to detect permafrost degradation by simply comparing lake areas from different time periods. In this study, we used Landsat images of 16 time periods between 1984 and 2009 to extract lake area (closed basin lakes only) for a 422,382 ha study area within Yukon Flats, Alaska. A multiple linear regression model was built to quantify the long term change in lake area. In this model, we included LWB (local water balance, defined as difference between total precipitation and total potential evapotranspiration since the preceding October), MDT (mean daily temperature from May 1st to the date that Landsat image was acquired) and PRD (four time periods: 1984-1986, 1992, 1999-2002, and 2009). MDT was used to indicate the active layer depth. Both LWB and MDT were used to account for natural variability in lake area. The model explained 95% of the total variability in lake area, with 62%, 16% and 17% accounted for by LWB, MDT and PRD respectively. Using the total lake area (15898 ha) in 1984-1986 as a baseline, lake area increased by 12% in 1992, and decreased by 6% during 1999-2002 and 8% in 2009. Among the 1,667 lakes, 267 lakes showed an area decrease and 115 lakes showed an increase. The expanding lakes were distributed along the Yukon River and its main tributaries (Beaver creek and Birch creek), while the shrinking lakes were located farther away from rivers or on fluvial terraces. A potential reason for the spatial pattern of expanding and shrinking lakes is that, after permafrost thaws, lakes can become connected to the groundwater system. Lakes close to the rivers may be recharged by groundwater due to their lower position relative to groundwater table, while lakes farther away from rivers drain to the subsurface due to their higher position. This study provides a rigorous method to quantify long term change in thermokarst lake area and the regression model can be used in earth system models to make better predictions of thermokarst lake areas.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001895 Hinkel, Kenneth M. (University of Cincinnati, Department of Geography, Cincinnati, OH); Lenters, J. D.; Grosse, G.; Arp, C. D.; Jones, B.; Beck, R. A.; Eisner, W. R.; Frey, K. E.; Liu, H.; Kim, C. and Townsend-Small, Amy. Initial results from the CircumArctic Lakes Observation Network (CALON) Project [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21B-0466, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

About half of the Arctic Coastal Plain (ACP) of northern Alaska is covered with thermokarst lakes and drained lake basins, making lakes a dominant landscape element and a crucial component of the Arctic permafrost system. However, to date there has been no systematic collection of key lake parameters or baseline data with which to make spatial and temporal comparisons to assess the impact of warmer temperatures, changing cloud cover and precipitation patterns, permafrost degradation, and direct human impacts on lakes. As separate groups, we have been working on lakes in arctic Alaska for the past decade and are currently monitoring some lakes. This effort has recently been organized into the Circumarctic Lakes Observation Network (CALON) with funding from NSF's Arctic Observing Network (AON) program. The objective of CALON is to expand and integrate our existing lake monitoring network across arctic Alaska to provide data for key indices using in situ measurements, field surveys, interviews with members of the indigenous community, and remote sensing/GIS technologies. In 2012, we will enhance the existing in situ network by developing lake monitoring sites to collect year-round baseline data and assess physical, chemical, and biological lake characteristics across environmental gradients. This will be accomplished by implementing a multiscale (hierarchical) lake instrumentation scheme such that basic data are collected from 51 lakes, while a subset of 16 lakes is more intensively instrumented. Regional scaling and extrapolation of key metrics is accomplished through validation of satellite imagery with ground measurements, and standardized protocols will be developed to enable inter-site comparison and to prepare for expansion towards a pan-Arctic network. Initial results are available from lake water profile temperature measurements made in summer 2010 along a 130-km transect extending from Barrow southward toward the interior. Ice-out occurs about 2-4 weeks later on lakes near the Arctic coast, reflecting the marine influence. Rapid warming follows ice-cover decay, with water temperature responding synchronously to daily and synoptic weather variations across the area. Inland lakes are significantly (6°C) warmer in mid-summer than those near the coast, which is also in accordance with the regional climatic gradient. All lakes are well-mixed and largely isothermal, with minimal thermal stratification (< 2°C) occurring only during calm, sunny periods in deeper lakes (> 2m). During the last several years lake water temperature, water level, and ice thickness measurements have also been collected from in a number of lakes located near a coastal hub site in the vicinity of Teshekpuk Lake. This dataset also reveals variability in the thermal regime over small geographic areas both within and between years with respect to differences in lake depth, lake size, and local environmental conditions.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001898 Jepsen, S. M. (U. S. Geological Survey, Denver, CO); Voss, C. I.; Walvoord, M. A.; Minsley, B. J.; Rose, J. and Smith, B. D. Disappearing Twelvemile Lake in Alaska's discontinuous permafrost; scoping analysis of water budget [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21B-0469, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

The number and size of lakes in northern high-latitude regions have undergone significant changes over the last 3 decades or longer, possibly in association with climate warming. In the Yukon Flats Basin (YFB) of interior Alaska, a region underlain by discontinuous permafrost, these changes have not been uniform among lake drainage basins, suggesting the importance of local processes that are not well understood. As an example in the YFB, Twelvemile Lake has decreased in area by 60% since 1984, while neighboring Buddy Lake, 2 km to the southeast, has shown no significant change (see Figure). The objective of this study is to evaluate physical mechanisms that could account for the lowering of Twelvemile Lake, using a combination of water flux approximations, historical climate data and the permafrost distribution as interpreted from airborne electromagnetics (AEM). All possible in- and out-flux pathways to the lake are considered and compared with the observed rate of change in the lake's volume, to rank the importance of each pathway as a contributor to the change in lake level. Results from the AEM survey suggest the presence of a »200 m diameter open-talik beneath the lake, and subsurface, channel-shaped depressions in the permafrost table ("channels") that may direct shallow groundwater (GW) flow into or out of the lake basin. An increase in potential evapotranspiration of only »2 cm yr^-1 from the period of 1950-1980 to 1981-2010 is found to be insignificant relative to the observed 13 cm yr^-1 rate of lake level lowering since the early 1980's. Thus, alternative water pathways are needed to explain the lake level change. The following four processes are shown to potentially have a significant contribution to the observed rate of lake level change: (i) Reduced water inputs from decreased snowpacks; (ii) Increased infiltration of snowmelt due to changes in wintertime ice content of subnivean soil; (iii) Changes in GW flow through inlet and outlet channels to the lake basin due to ground ice dynamics; (iv) Changes in GW flow to the lake resulting from lateral ice aggradation or degradation in the open-talik. In conclusion, the lowering of Twelvemile Lake may result from a combination of processes that are operating in addition to those commonly associated with thermokarst lakes.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001864 Kholodov, A. L. (University of Alaska Fairbanks, Geophysical Institute, Fairbanks, AK). The role of the snow covers in the permafrost temperature dynamics at the northern Yakutia over the last 30 years [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C13B-0743, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

This report concerns the changes of the dynamics of snow warming influence on the permafrost temperature at the northern Yakutia. Snow is a key factor determines the thermal state of permafrost here. Despite of the absence of air temperature latitudinal zonality mean annual ground temperature decreases northward approximately 1 centigrade per latitude degree due to changes of the snow warming impact. At the north-western part with a relatively maritime climate warming influence of the snow is 0.5 to 1.5°C, while in the southern and eastern part with more continental climate it is 3.5 to 4.5°C. Snow redistribution within the some types of landscape at the beginning of the winter season can lead to the extremely fast freezing of the active layer and cooling of the permafrost within such types of landscapes. The main goal of the current research was to estimate snow warming impact dynamics over the last 30 years in the northern Yakutia. We took in consideration changes of the three main parameters, are determining snow cover thermal state: snow thickness; amplitude of air temperature seasonal oscillation; temperature during the winter period during. Following conclusion can be done based on the data analysis: Interannual changes of snow warming influence are tenth to first centigrades, what is comparable with air temperature fluctuations. During the 1980-90s snow impact on the permafrost stood stable in the southeastern part of the region or had a slightly negative trend in the western part. It could be explained by the changes of snow thickness, reduced thermal resistivity of snow due to winter warming and decreasing of the amplitude of seasonal temperature oscillation in the western part of the region. Since the end of 90s general increasing of the snow cover warming influence was noticed for the entire investigated territory. These results correspond with data of modern permafrost temperature observations have been done in the region during the last decades. Most of monitoring sites did not show sustainable changes of the permafrost temperature until the end of 90s years of the XX century, but recent measurements record increasing of the mean annual ground temperature at the most of monitoring sites in the region.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001882 Lachniet, M. S. (University of Nevada Las Vegas, Department of Geoscience, Las Vegas, NV); Sloat, A. R. and Lawson, D. E. Ice wedge growth in the Fox permafrost tunnel dates to marine isotope stage II? [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21A-0453, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

We dated a Pleistocene ice wedge (wedge 50S) and its host sediments from the CRREL Fox Permafrost Tunnel near Fairbanks, Alaska with twenty radiocarbon analyses on wood, dispersed organic material, dissolved inorganic carbon (DIC), and dissolved organic carbon (DOC). The age of a wood fragment within the host sediments is 35,570 ± 340 14C yr BP and is thus a maximum age of wedge growth. Previous 14C ages of dispersed organic matter within the ice wedge returned ages from 28 to 31 14C ka, and the wedge is overlain by sediment in which a wood fragment returned an age of 30,090 ± 300 14C yr BP, thus suggesting an age of between 28-35 14C ka BP. Such an age is surprising because it occurs during Marine Isotope Stage (MIS) III, not the colder intervals of MIS II. To constrain better the wedge age for paleoclimatic analysis, we determined DIC and DOC age pairs within four ice blocks subsampled from the wedge. Our new DIC/DOC dates are up to 8000 years younger than dispersed organic material in the wedge. The DIC/DOC age pairs return divergent ages, which suggest fluctuating proportions of carbon dioxide and organic carbon with variable radiocarbon ages entrapped within the ice wedge. Because the organic matter ages are older than the DIC/DOC ages, we conclude that they represent "detrital" maximum ages for the ice wedge and represent the timing of permafrost aggradation prior to wedge growth. Based on the assumption that the ice ages can only be contaminated by old "detrital" carbon associated with the stratigraphically older host sediments, the youngest dates likely provide the best estimate of when the ice wedge was last active. The youngest age we determined is 21,600 ± 140 14C yr BP (on DOC) recovered from inclined folia that parallel the outer wedge margin at ca. 3.25 cm from the left-most edge, which corresponds to a calendar age of 25.7 cal ka. This sample location corresponds to the stratigraphically-oldest ice according to standard ice wedge growth models. We also determined a minimum age of the wedge of 18,000 ± 110 14C yr BP by dating of DOC in "pond" ice near to and stratigraphically above wedge 50S. Our data thus substantially revise the timing of ice wedge 50S growth to between 21,600 and 18,000 14C yr BP during MIS II. The calendar age of the youngest wedge date coincides with the beginning of Heinrich event 2 at ca. 26 cal ka, and we hypothesize that ice wedge growth coincided with cold conditions in Alaska at this time. The anomalously "old" age of 30,090 ± 300 14C yr BP stratigraphically above the ice wedge may represent the age of material emplaced by mass movement over the wedge following ice growth cessation and may not be a true minimum limiting age. Our data further reveal complex carbon-source dynamics in permafrost and ice wedge sediments.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001901 Lyons, E. A. (University of California at Los Angeles, Department of Geography, Los Angeles, CA); Sheng, Y. and Hinkel, K. M. Seasonal and interannual lake dynamics on the Arctic Coastal Plain of Alaska [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21B-0473, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

This study measured seasonal and interannual lake dynamics on the Arctic Coastal Plain. We investigated the factors that made a shoreline stable or dynamic. Using differential GPS, the lake shorelines were mapped with sub-meter accuracy in June and August of 2008 through 2010. These lake shoreline maps were combined with lake maps generated from 46 Landsat images over 33 years. Despite being within 10 km of each other, lakes on the Barrow Peninsula exhibit strikingly different seasonal and interannual dynamics. Of those lakes mapped in all three years, two lakes showed no significant seasonal or interannual change, one lake showed significant seasonality but no inter-annual change, and one lake showed significant interannual trend with little seasonality. In addition to changes in hydrologic variables, lakes on the Arctic Coastal Plain experience changing permafrost regimes which act on each lake individually.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001848 Marinova, M. (NASA, Ames Research Center, Space Sciences Division, Moffett Field, CA); McKay, C. P.; Heldmann, J. L.; Davila, A. F.; Andersen, D. T.; Jackson, A.; Lacelle, D.; Paulsen, G.; Pollard, W. H. and Zacny, K. Mapping the depth to ice-cemented ground in the high elevation dry valleys, Antarctica [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C11F-08, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

The high elevation Dry Valleys of Antarctica provide a unique location for the study of permafrost distribution and stability. In particular, the extremely arid and cold conditions preclude the presence of liquid water, and the exchange of water between the ice-cemented ground and the atmosphere is through vapour transport (diffusion). In addition, the low atmospheric humidity results in the desiccation of the subsurface, forming a dry permafrost layer (i.e., cryotic soils which are dry and not ice-cemented). Weather data suggests that subsurface ice is unstable under current climatic conditions. Yet we do find ice-cemented ground in these valleys. This contradiction provides insight into energy balance modeling, vapour transport, and additional climate effects which stabilize subsurface ice. To study the driving factors in the stability and distribution of ice-cemented ground, we have extensively mapped the depth to ice-cemented ground in University Valley (1730 m; 77°S 51.8', 160°E 43'), and three neighboring valleys in the Beacon Valley area. We measured the depth to ice-cemented ground at 15-40 locations per valley by digging soil pits and drilling until ice was reached; for each location 3-5 measurements within a »1 m² area were averaged (see figure). This high-resolution mapping of the depth to ice-cemented ground provides new insight on the distribution and stability of subsurface ice, and shows significant variability in the depth to ground ice within each valley. We are combining data from mapping the depth to ice-cemented ground with year-round, in situ measurements of the atmospheric and subsurface conditions, such as temperature, humidity, wind, and light, to model the local stability of ice-cemented ground. We are using this dataset to examine the effects of slopes, shading, and soil properties, as well as the suggested importance of snow recurrence, to better understand diffusion-controlled subsurface ice stability.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001900 Mayer, D. P. (Clark University, School of Geography, Worcester, MA) and Frey, K. E. Measuring seasonal variations of East Siberian thermokarst lake areas using PALSAR data [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21B-0472, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

Degradation of permafrost owing to climate warming is expected to have profound impacts on Arctic hydrology and biogeochemical cycling. Thermokarst lakes, or thaw lakes, are major features of Arctic landscapes and are important modulators of biogeochemical activity in permafrost-affected regions. Recent studies of thaw lake change in eastern Siberia using remotely-sensed optical images acquired several decades apart suggest that thaw lakes have increased in number and extent in areas of continuous permafrost. However, such studies are limited by their inability to account for seasonal variations in lake extent associated with summer snowmelt. The objective of this study was to quantify changes in thaw lake area throughout the summer melt season within a »2500 km² area of the Kolyma River drainage basin in eastern Siberia. The analysis was based on 9 scenes acquired by the Phased Array L-band Synthetic Aperture Radar (PALSAR) instrument during the summers of 2007, 2008 and 2010. The unique backscatter signature of open water in L-band SAR data allows for straightforward delineation of open water. Lakes were classified by applying a histogram threshold to cross-polarized radar backscatter images using a minimum spatial threshold of 0.26 hectares (16 contiguous pixels). The results of this analysis indicate that the total extent of thaw lakes can decrease by as much as ~25% during the period from one week after freshet in early June to early September. These results suggest that estimates of interannual change in thaw lake extent based on remotely-sensed images may be sensitive to the time of year when the data were captured and that higher temporal resolution image data are needed to draw firm conclusions about trends in thaw lake extent in areas of continuous permafrost.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13001892 Sloat, A. R. (University of Nevada Las Vegas, Las Vegas, NV); Lachniet, M. S. and Lawson, D. E. d¹⁸O and dD suggest episodic late Pleistocene ice wedge growth in central Alaska [abstr.]: in AGU 2011 fall meeting, American Geophysical Union Fall Meeting, 2011, Abstract C21A-0463, December 2011. Meeting: American Geophysical Union 2011 fall meeting, Dec. 5-9, 2011, San Francisco, CA.

Stable isotopes in ancient buried ice wedges from the Cold Regions Research and Engineering Laboratory Permafrost Tunnel indicate growth occurred during three cold episodes during the late Pleistocene in Central Alaska. Oxygen (d¹⁸O) and hydrogen (dD) stable isotopes were analyzed at high resolution in seven ice wedges (1N, 14.9SWinze, 18N, 35S, 45S, 52.5S, and 58N). Three stratigraphically separate climatic events are apparent in the d¹⁸O, dD, and deuterium excess (d_x) records of ice wedges, with d¹⁸O values ranging from -29 to -20ppm (SMOW) and d_x values ranging from -6 to +9ppm (SMOW). Paleotemperatures during ice wedge formation were determined using the equation T(°C) = d¹⁸O/0.80 derived from Alaskan stations within the Global Network of Isotopes in Precipitation (GNIP) database. Assuming no change in moisture source over time, the middle stratigraphic unit ice wedges formed when temperatures were the coldest, with the lower stratigraphic unit ice wedges forming when temperatures were 3 + 0.3°C higher, and the upper stratigraphic unit wedges forming when temperatures were 9 + 0.3°C higher. In wedge 58N, d¹⁸O values of -24ppm at the outer edge of the wedge and d¹⁸O values of -27ppm in the center of the wedge indicate formation began in warmer conditions, growth occurred during a cold period, and growth terminated abruptly during the onset of a warming event. Dissolved organic carbon (DOC) dates of 26,879 + 579 cal yr BP indicate the lower unit wedges began forming during Heinrich Event 2 (H2). Isotopic signatures of small wedges in the uppermost unit in the tunnel indicate formation occurred during later cold events in Central Alaska. These stable isotope data provide insight into the possible response of Central Alaska to North Atlantic Heinrich event forced climatic variability during the late Pleistocene.

URL: http://www.agu.org/cgi-bin/SFgate/SFgate?language=English&verbose=0&listenv=tabl ...

13006602 Painter, Thomas H. (Jet Propulsion Laboratory, Pasadena, CA); Deems, Jeffrey S. and Skiles, S. McKenzie. Impact of dust on snow albedo, snowmelt, and runoff in the Colorado River basin [abstr.]: in Geological Society of America, 2011 annual meeting, Abstracts with Programs - Geological Society of America, 43(5), p. 337, October 2011. Meeting: Geological Society of America, 2011 annual meeting, Oct. 9-12, 2011, Minneapolis, MN.

The allocation of Colorado River runoff to more than 25 million people in 7 states and 2 countries is overcommitted by more than 10% of its historical mean. Climate models project runoff losses of 7 to 20% from the basin in this century due to human-induced climate change. Recent work has shown however that by the late 1800s, decades prior to allocation of the river's runoff in the 1920s, a five-fold increase in dust loading from anthropogenically disturbed soils in the southwest US was already decreasing snow albedo and shortening the duration of snow cover by several weeks. From in situ radiation measurements in the mountains of the Upper Colorado River basin (UCRB), we have found that dust absorption in snow reduces snow albedo from its fresh snow value of ~0.85 down to 0.4-0.5 and in years with extreme dust loading, down to ~0.3. At-surface radiative forcings range from 25 to 110 W/m², compared with the globally-averaged anthropogenic greenhouse gas forcing of about 3 W/m². These radiative forcings increase the already dominant net solar radiation in melting snow and shortening snow duration by 25-50 days. We have extrapolated these results to the UCRB using the Variable Infiltration Capacity model with post-disturbance and pre-disturbance impacts of dust on albedo to assess the impact on runoff from the UCRB across 1916 to 2003. We find that peak runoff at Lees Ferry, AZ has occurred on average three weeks earlier under heavier dust loading and that increases in evapotranspiration from earlier exposure of vegetation and soils may decrease runoff by more than ~1.0 billion cubic meters (bcm) or ~5% of annual average runoff. Toward understanding dust's impact on snowmelt runoff in the context of water management, we investigated the interannual variability of rates of change in runoff during the snowmelt runoff relative to the interannual variability in air temperature (through positive degree days) and dust radiative forcing across 6 years of data in the San Juan Mountains, Colorado. We find that the temperature variation explains none of the variation in runoff anomalies whereas runoff anomalies are strongly dependent on the variation in dust radiative forcing.

13006515 Retallack, Gregory J. (University of Oregon, Department of Geological Sciences, Eugene, OR). Paleosol evidence for Ediacaran glaciations near Boston, Massachusetts, USA [abstr.]: in Geological Society of America, 2011 annual meeting, Abstracts with Programs - Geological Society of America, 43(5), p. 321, October 2011. Meeting: Geological Society of America, 2011 annual meeting, Oct. 9-12, 2011, Minneapolis, MN.

Fossil ice wedges of periglacial paleosols in the upper Squantum and upper Brookline Members of the Roxbury Conglomerate, and other intervening paleosols of humid temperate paleoclimate, now indicate two separate post-Cryogenian glacial episodes near Boston, Massachusetts, which had an Ediacaran paleolatitude of 50°. Two episodes and several glacial stages are also revealed by extensive chemical analyses for Ba/Sr ratios and chemical index of alteration of sediments within both the Roxbury Conglomerate and the Cambridge Argillite. One glacial episode predates a local tuff dated by ²⁰⁷Pb/²⁰⁶Pb at 567 ± 1.7 Ma, and the second glacial episode of 4 distinct glacial stages postdates that tuff and predates early Cambrian sandstones. Both glaciations are Ediacaran because they postdate well dated local basement rocks: Lynn-Mattapan Volcanics at 596-602 Ma and Dedham Granite at 606-610 Ma. Age models and international correlations suggest early Ediacaran (ca. 582 Ga) and late Ediacaran (ca. 550 Ga) ages for these glacial episodes, as for Gaskiers and Baykonur Glaciations of Newfoundland and Siberia, respectively. In the South Australian Ediacaran stratotype, these two glacial episodes are represented by dropstones in the Bunyeroo Formation and diamictites in the Billy Springs Formation. Both glacial episodes are represented by ice wedges near Boston, which today are evidence of maritime glacial climate like that of coastal Greenland and Arctic Canada, unlike continental glaciation and sand wedges of inland Antarctica and the Cryogenian Elatina Glaciation of South Australia. Simple discoidal vendobiont fossils (Aspidella terranovica) in the Dorchester Member of the Roxbury Formation (newly discovered) and in the Cambridge Argillite are in heterolithic shale-siltstone facies interpreted as intertidal to shallow marine, as for Aspidella-bearing shales of the Fermeuse Formation of Newfoundland. These were sessile benthic organisms with filamentous internal microstructure.

13002967 Buckeridge, Kate M. (Queen's University, Department of Biology, Kingston, ON, Canada) and Grogan, Paul. Deepened snow increases late thaw biogeochemical pulses in mesic low Arctic tundra: in 6th international symposium on Ecosystem behavior (Johnson, D. W., editor; et al.), Biogeochemistry (Dordrecht), 101(1-3), p. 105-121, illus., 65 ref., December 2010. Meeting: BIOGEOMON 2009 (6th international symposium on Ecosystem behavior), June 29-July 3, 2009, Helsinki, Finland.

Pulses of plant-available nutrients to the soil solution are expected to occur during the dynamic winter-spring transition in arctic tundra. Our aims were to quantify the magnitude of these potential nutrient pulses, to understand the sensitivity of these pulses to winter conditions, and to characterize and integrate the environmental and biogeochemical dynamics of this period. To test the hypotheses that snow depth, temperature and soil water-and not snow nutrient content-are important controls on winter and spring biogeochemistry, we sampled soil from under ambient and deepened snow every 3 days from late winter to spring, in addition to the snowpack at the start of thaw. Soil and microbial biogeochemical dynamics were divided into distinct phases that correlated with steps in soil temperature and soil water. Soil solution and microbial pools of C, N and P fluctuated with strong peaks and declines throughout the thaw, especially under deepened snow. Snowpack nutrient accumulation was negligible relative to these biogeochemical peaks. All nutrient and microbial peaks declined simultaneously at the end of snowmelt and so this decline was delayed by 15 days under deepened snow. The timing of these nutrient pulses is critical for plant species nutrient availability and landscape nutrient budgets. This detailed and statistically-based characterisation of the winter-spring transition in terms of environmental and biogeochemical variables should provide a useful foundation for future biogeochemical process-based studies of thaw, and indicate that spring thaw and possibly growing season biogeochemical dynamics are sensitive to present and future variability in winter snow depth. Copyright 2010 Springer Science+Business Media B.V. and The Author(s)

DOI: 10.1007/s10533-010-9426-5

13002939 Alewell, Christine (University of Basel, Department of Environmental Geoscience, Basel, Switzerland); Giessler, Reiner; Klaminder, Jonathan and Rollog, Mark. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats [abstr.]: in European Geosciences Union general assembly 2010, Geophysical Research Abstracts, 12, EGU2010-4359, 2010. Meeting: European Geosciences Union general assembly 2010, May 2-7, 2010, Vienna, Austria.

13008565 Chasmer, L. (Wilfrid Laurier University, Cold Regions Research Centre, Waterloo, ON, Canada); Hopkinson, C. and Quinton, W. Quantifying errors in discontinuous permafrost plateau change from optical data, Northwest Territories, Canada; 1947-2008: in 30th Canadian symposium on Remote sensing; bridging excellence (Peddle, Derek R., editor; et al.), Canadian Journal of Remote Sensing (CD-ROM) = Journal Canadien de Télédétection (CD-ROM), 36(SUPPL.2), p. 211-223 (French sum.), illus. incl. 5 tables, sketch maps, 25 ref., 2010. Meeting: Thirtieth Canadian symposium on Remote sensing, June 22-25, 2009, Lethbridge, AB, Canada.

The discontinuous permafrost zone has been subject to increased air temperatures over recent decades. Permafrost thaw can cause changes to topography, hydrology, vegetation, and trace gas fluxes, and thus it is important to monitor changes in permafrost area through time. Optical imagery can be used to generate time-series databases of near-surface spectra that may be related to permafrost area. This provides a spatial perspective on area permafrost change that is not easily obtained from field data alone. This study examines the cumulative maximum and minimum errors of aerial and satellite imagery used for change detection within the Scotty Creek watershed, Fort Simpson, NWT, Canada. The results illustrate that, unless unchanging linear features are found throughout every image used (e.g., to be used as multitemporal tie points) and radiometric normalization can be applied (problematic for film images), direct image to image comparisons (e.g., subtraction) are not appropriate. Further, measureable cumulative errors are often produced by misclassification of edges, resolution limitations, and increased landscape fragmentation. At Scotty Creek, increased fragmentation of permafrost plateaus occurred from 1947 to 2008. Cumulative maximum and minimum errors result in an approximate 8%-26% error in permafrost area when compared with the total area of the site. Rates of permafrost area reduction within the study area were approximately 0.5% every year, determined from linear correlation (r² = 0.91, n = 5). Therefore, based on the maximum cumulative error (a worst-case scenario), approximately 21-32 years (for resolutions of 0.18-1.10 m) is required between images to approximate change within this particular site. Increased (decreased) rates of change at other sites will decrease (increase) the timing required to identify change between images beyond error bounds.

URL: http://pubs.casi.ca/doi/abs/10.5589/m10-058

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13002295 Bobrowsky, P. T. and Dominguez, M. J. Landslide susceptibility map of Canada: Open-File Report - Geological Survey of Canada, Geological Survey of Canada, Calgary, AB, Canada, Rep. No. 7228, 1 sheet, tables; geologic hazards map, 1:6,000,000, 4 ref., 2012. WWW. Accessed on Nov. 21, 2012.

Landslides are especially damaging in Canada and despite their extensive occurrence, the exact location of instability depends on several factors and is therefore not homogeneous across the country. The 1:6 million scale landslide susceptibility map of Canada presented here is a first approximation for those individuals interested in pursuing more detailed investigations. The map has been constructed based primarily on GIS, by considering digital layers of relevant national information including: slope angle, aspect, precipitation, permafrost, surficial geology, vegetation, distance to rivers, distance to coast (lakes and oceans) and bedrock lithology. These variables have been categorized into several classes depending on their greater or lesser favourability to influence slope instabilities. The values assigned to each class are not equal for the whole country and vary depending on the region considered (Canadian Shield, Hudson Bay Lowlands, or the remaining area). Broad patterns in slope instability are apparent at the national scale.

URL: http://geoscan.ess.nrcan.gc.ca/cgi-bin/starfinder/0?path=geoscan.downloade.fl&id ...

13002210 Short, N.; LeBlanc, A. M.; Sladen, W. E.; Allard, M. and Mathon-Dufour, V. Seasonal surface displacement derived from InSAR, Iqaluit, Nunavut: Geological Survey of Canada, Canadian Geoscience Map, Geological Survey of Canada, Ottawa, ON, Canada, Rep. No. 66, 1 disc or 1 sheet (French sum.), illus. incl. tables; colored surficial geology map, 1:15,000, 5 ref., 2012. ISBN: 978-1-100-19878-1 compact disc, WWW. Preliminary edition. Accessed on Nov. 21, 2012.

This map shows the spatial distribution of the relative ground surface displacement between the major terrain units during one summer in the area of Iqaluit. The ground displacement was derived using interferometric synthetic aperture radar (InSAR) data for the summer of 2011. Stable ground represents locations where either no vertical change was calculated or where displacement was within the expected range of error (±0.5 cm). Very low, low, and moderate downward displacement represents surface lowering on the order of 0.5 to 2, 2 to 4.5, and 4.5 to 8.5 cm, respectively. Upward displacement represents a surface rise of 0.5 to 1.5 cm. Areas of no data result from a loss of interferometric coherence. These are typically water and other relatively smooth surfaces from which there is no radar return, or where there has been significant ground surface disturbance and the radar returns cannot be correlated. The InSAR results correspond well with the expected displacement associated with the characteristics of the major terrain units. The displacement reflects seasonal settlement caused by thawing of ice in the active layer or in the near-surface permafrost.

URL: http://geoscan.ess.nrcan.gc.ca/cgi-bin/starfinder/0?path=geoscan.downloade.fl&id ...">http://geoscan.ess.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/geos ...

13002211 Short, N.; LeBlanc, A. M.; Sladen, W. E.; Carbonneau, A. S. and Allard, M. Seasonal surface displacement derived from InSAR, Pangnirtung, Nunavut: Geological Survey of Canada, Canadian Geoscience Map, Geological Survey of Canada, Ottawa, ON, Canada, Rep. No. 67, 1 disc or 1 sheet (French sum.), colored surficial geology map, 1:5,000, 4 ref., 2012. ISBN: 978-1-100-19879-8 compact disc, WWW. Preliminary edition. Accessed on Nov. 21, 2012.

This map shows the spatial distribution of the relative ground surface displacement between the major terrain units during one summer in the area of Pangnirtung. The ground displacement was derived using interferometric synthetic aperture radar (InSAR) data for the summer of 2011. Stable ground represents locations where either no vertical change was calculated or where displacement was within the expected range of error (±0.5 cm). Very low, low, moderate, and high downward displacement represents surface lowering on the order of 0.5 to 2, 2 to 4.5, 4.5 to 8.5, and 8.5 to 10 cm, respectively. Upward displacement represents a surface rise of 0.5 to 3 cm. Areas of no data result from a loss of interferometric coherence. These are typically water and other relatively smooth surfaces from which there is no radar return, or where there has been significant ground surface disturbance and the radar returns cannot be correlated. The InSAR results correspond well with the expected displacement associated with the characteristics of the major terrain units. The displacement reflects seasonal settlement caused by thawing of ice in the active layer or in the near-surface permafrost.

URL: http://geoscan.ess.nrcan.gc.ca/cgi-bin/starfinder/0?path=geoscan.downloade.fl&id ...

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