2017076744 Kanevskiy, Mikhail (University of Alaska at Fairbanks, Institute of Northern Engineering, Fairbanks, AK); Shur, Yuri; Jorgenson, Torre; Brown, Dana R. N.; Moskalenko, Nataliya; Brown, Jerry; Walker, Donald A.; Raynolds, Martha K. and Buchhorn, Marcel. Degradation and stabilization of ice wedges; implications for assessing risk of thermokarst in northern Alaska: Geomorphology, 297, p. 20-42, illus. incl. sketch maps, November 15, 2017. Includes appendix.

Widespread degradation of ice wedges has been observed during the last decades in numerous areas within the continuous permafrost zone of Eurasia and North America. To study ice-wedge degradation, we performed field investigations at Prudhoe Bay and Barrow in northern Alaska during 2011-2016. In each study area, a 250-m transect was established with plots representing different stages of ice-wedge degradation/stabilization. Field work included surveying ground- and water-surface elevations, thaw-depth measurements, permafrost coring, vegetation sampling, and ground-based LiDAR scanning. We described cryostratigraphy of frozen soils and stable isotope composition, analyzed environmental characteristics associated with ice-wedge degradation and stabilization, evaluated the vulnerability and resilience of ice wedges to climate change and disturbances, and developed new conceptual models of ice-wedge dynamics that identify the main factors affecting ice-wedge degradation and stabilization and the main stages of this quasi-cyclic process. We found significant differences in the patterns of ice-wedge degradation and stabilization between the two areas, and the patterns were more complex than those previously described because of the interactions of changing topography, water redistribution, and vegetation/soil responses that can interrupt or reinforce degradation. Degradation of ice wedges is usually triggered by an increase in the active-layer thickness during exceptionally warm and wet summers or as a result of flooding or disturbance. Vulnerability of ice wedges to thermokarst is controlled by the thickness of the intermediate layer of the upper permafrost, which overlies ice wedges and protects them from thawing. In the continuous permafrost zone, degradation of ice wedges rarely leads to their complete melting; and in most cases wedges eventually stabilize and can then resume growing, indicating a somewhat cyclic and reversible process. Stabilization of ice wedges after their partial degradation makes them better protected than before degradation because the intermediate layer is usually 2 to 3 times thicker on top of stabilized ice wedges than on top of initial ice wedges in undisturbed conditions. As a result, the likelihood of formation of large thaw lakes in the continuous permafrost zone triggered by ice-wedge degradation alone is very low.

DOI: 10.1016/j.geomorph.2017.09.001

2017068518 Palagushkina, Olga (Kazan Federal University, Institute of Management, Economics and Finance, Kazan, Russian Federation); Wetterich, Sebastian; Biskaborn, Boris K.; Nazarova, Larisa; Schirrmeister, Lutz; Lenz, Josefine; Schwamborn, Georg and Grosse, Guido. Diatom records and tephra mineralogy in pingo deposits of Seward Peninsula, Alaska: Palaeogeography, Palaeoclimatology, Palaeoecology, 479, p. 1-15, illus. incl. 3 tables, sketch maps, 110 ref., August 2017.

Vast areas of the terrestrial Subarctic and Arctic are underlain by permafrost. Landscape evolution is therefore largely controlled by climate-driven periglacial processes. The response of the frozen ground to late Quaternary warm and cold stages is preserved in permafrost sequences, and deducible by multi-proxy palaeoenvironmental approaches. Here, we analyse radiocarbon-dated mid-Wisconsin Interstadial and Holocene lacustrine deposits preserved in the Kit-1 pingo permafrost sequence combined with water and surface sediment samples from nine modern water bodies on Seward Peninsula (NW Alaska) to reconstruct thermokarst dynamics and determine major abiotic factors that controlled the aquatic ecosystem variability. Our methods comprise taxonomical diatom analyses as well as Detrended Correspondence Analysis (DCA) and Redundancy Analysis (RDA). Our results show, that the fossil diatom record reflects thermokarst lake succession since about 42 ¹⁴C kyr BP. Different thermokarst lake stages during the mid-Wisconsin Interstadial, the late Wisconsin and the early Holocene are mirrored by changes in diatom abundance, diversity, and ecology. We interpret the taxonomical changes in the fossil diatom assemblages in combination with both modern diatom data from surrounding ponds and existing micropalaeontological, sedimentological and mineralogical data from the pingo sequence. A diatom-based quantitative reconstruction of lake water rN indicates changing lake environments during mid-Wisconsin to early Holocene stages. Mineralogical analyses indicate presence of tephra fallout and its impact on fossil diatom communities. Our comparison of modern and fossil diatom communities shows the highest floristic similarity of modern polygon ponds to the corresponding initial (shallow water) development stages of thermokarst lakes. We conclude, that mid-Wisconsin thermokarst processes in the study area could establish during relatively warm interstadial climate conditions accompanied by increased precipitation due to approaching coasts, while still high continentality and hence high seasonal temperature gradients led to warm summers in the central part of Beringia.

DOI: 10.1016/j.palaeo.2017.04.006

2017068609 van Vliet-Lanoë, Brigitte (Université de Bretagne Occidentale, Laboratoire Domaines Océaniques, Plouzane, France); Brulhet, Jacques; Combes, Philippe; Duvail, Cédric; Ego, Frédéric; Baize, Stéphane and Cojan, Isabelle. Quaternary thermokarst and thermal erosion features in northern France; origin and palaeoenvironments: Boreas, 46(3), p. 442-461, illus. incl. sects., geol. sketch map, 116 ref., July 2017.

A thermokarst is a collapse feature resulting from the thawing of ice-rich permafrost or of massive ice of various origins. Little attention has been paid to the sedimentary fabric resulting from this type of collapse, except for glaciotectonic features. In western Europe, two palaeo-forms are commonly studied: lithalsas and ice-wedge casts. Collapsed pingos are much rarer. Very few papers have compiled present-day and fossil data. Here, field data collected from quarries in the eastern Paris Basin were analysed, providing useful records of thermokarst collapses in alluvial calcareous silts, sands, and gravels. These forms have a circular shape when viewed on satellite images. Permafrost is attested regionally by the recurrent occurrence of meter-sized pattern grounds at the surface of the chalk and of ice-wedge casts. Traces of segregation and reticulate ice are common. These features are primarily connected to a major interstadial, c. 150 ka BP, orbitally forced and commonly associated with a major glacial retreat. They occur both in drained and waterlogged situations, resulting in a specific pattern of deformation. They are controlled by the brittle and plastic behaviour of sediments and resemble passive glaciotectonism. Normal and reverse faults, with the offset decreasing downward, are common, and those with local shear are reported. Lithalsas, seasonal frost blisters, spring frost blisters and perhaps pingos seem to have formed. Most of these deformations correspond to thermokarst sinkholes bordered by gravitational collapse faults. The offset of these faults increases towards the surface, and the faults have been recurrently confused with neotectonism triggered by palaeo-earthquakes. However, there are no faults beneath the observed deformation features, and the region lacks recorded seismic activity over the last century. Our data may be helpful in interpreting similar structures elsewhere. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1111/bor.12221

2017068633 Koch, Joshua C. (U. S. Geological Survey, Alaska Science Center, Anchorage, AK); Toohey, Ryan C. and Reeves, Donald M. Tracer-based evidence of heterogeneity in subsurface flow and storage within a boreal hillslope: Hydrological Processes, 31(13), p. 2453-2463, illus. incl. 2 tables, sketch map, 49 ref., June 30, 2017.

Runoff from boreal hillslopes is often affected by distinct soil boundaries, including the frozen boundary and the organic-mineral boundary (OMB), where highly porous and hydraulically conductive organic material overlies fine-grained mineral soils. Viewed from the surface, ground cover appears as a patchwork on sub-meter scales, with thick, moss mats interspersed with lichen-covered, silty soils with gravel inclusions. We conducted a decameter-scale subsurface tracer test on a boreal forest hillslope in interior Alaska to quantify locations and mechanisms of transport and storage in these soils, focusing on the OMB. A sodium bromide tracer was added as a slug addition to a pit and sampled at 40 down-gradient wells, screened primarily at the OMB and within a 7 ´ 12 m well field. We maintained an elevated head in the injection pit for 8.5 hr to simulate a storm. Tracer breakthrough velocities ranged from <0.12 to 0.93 m hr^-1, with the highest velocities in lichen-covered soils. After 12 hr and cessation of the elevated head, the tracer coalesced and was only detected in thick mosses at a trough in the OMB. By 24 hr, approximately 17% of the tracer mass could be accounted for. The majority of the mass loss occurred between 4 and 12 hr, while the tracer was in contact with lichen-covered soils, which is consistent with tracer transport into deeper flow paths via preferential flow through discrete gravelly areas. Slow breakthroughs suggest that storage and exchange also occurred in shallow soils, likely related to saturation and drainage in fine-grained mineral soils caused by the elevated hydraulic head. These findings highlight the complex nature of storage and transmission of water and solutes from boreal hillslopes to streams and are particularly relevant given rapid changes to boreal environments related to climate change, thawing permafrost and increasing fire severity. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.11205

2017068631 You Yanhui (Chinese Academy of Sciences, Arid Regions Environmental and Engineering Research Institute, Lanzhou, China); Yu Qihao; Pan, Xicai; Wang Xinbin; Guo Lei and Wu Qingbai. Thermal effects of lateral supra-permafrost water flow around a thermokarst lake on the Qinghai-Tibet Plateau: Hydrological Processes, 31(13), p. 2429-2437, illus. incl. sketch map, 38 ref., June 30, 2017.

Both the inflow and outflow of supra-permafrost water to lakes play important roles in the hydrologic process of thermokarst lakes. The accompanying thermal effects on the adjacent permafrost are required for assessing their influences on the development of thermokarst lakes. For these purposes, the lake water level, temperature dynamics, and supra-permafrost water flow of a lake were monitored on the Qinghai-Tibet Plateau. In addition, the spatial and temporal variation of the active layer thickness and permafrost distribution around the lake were investigated by combining ground penetrating radar, electrical resistivity tomography, and borehole temperature monitoring. The results revealed that the yearly unfrozen supra-permafrost water flow around the lake lasted approximately 5 months. The temperature and water level measurements during this period indicate that the lake water was recharged by relatively colder supra-permafrost water from the north-western lakeshore and was discharged through the eastern lakeshore. This process, accompanied by heat exchange with the underlying permafrost, might cause a directional difference of the active layer thickness and permafrost characteristics around the lake. Specifically, the active layer thickness variation was minimal, and the ice-rich permafrost was found adjacent to the lakeshore along the recharge groundwater pathways, whereas a deeper active layer and ice-poor permafrost were observed close to the lakeshore from which the warm lake water was discharged. This study suggests that the lateral flow of warm lake water can be a major driver for the rapid expansion of thermokarst lakes and provides clues for evaluating the relationships between the thermokarst expansion process and climate warming. Abstract Copyright (2010), John Wiley & Sons, Ltd.

DOI: 10.1002/hyp.11193

2017076739 Chadburn, S. E. (University of Leeds, School of Earth and Environment, Leeds, United Kingdom); Burke, E. J.; Cox, P. M.; Friedlingstein, P. and Hugelius, G. An observation-based constraint on permafrost loss as a function of global warming: Nature Climate Change, 7(5), p. 340-344, illus., 31 ref., May 2017. Based on Publisher-supplied data.

DOI: 10.1038/NCLIMATE3262

2017071001 Möller, P. (Helmholtz-Centre Potsdam, German Research Centre for Geosciences, Potsdam, Germany); Lüders, V. and De Lucia, M. Formation of Rotliegend Ca-Cl brines in the North German Basin compared to analogues in the geological record: Chemical Geology, 459, p. 32-42, illus. incl. 3 tables, 75 ref., May 25, 2017. Includes appendices.

The formation of terrestrial Ca-Cl brines is controlled by two major processes: chemical reactions between halite brines and igneous and metamorphic rocks and/or their debris in sedimentary basins, and the abstraction of H₂O by evaporation, freezing or formation of hydrous minerals. Albitization dominates in environments of low H₂O activity, i.e., halite saturated systems. Chloritization, serpentinization and formation of smectites seems to be related to less saline systems, i.e., enhanced water activity.The Rotliegend brines of the North German Basin evolved by interaction of infiltrating halite brines with volcanic debris of the Permian acid volcanic rocks by albitization and chloritization of plagioclase. At present their temperatures are between 130 and 150 °C at 3000-4000 m depth. Although they developed in a different environment they chemically and isotopically resemble the basinal brines from the Mississippi Salt Dome basin or even the deep brines from the Red Sea. All these brines have in common that halite brines interacted with plagioclase (An + SiO₂ + 2Na⁺ 2Alb + Ca²⁺) or possibly with clay minerals (Ca-clay + 2Na⁺ Na₂-clay + Ca²⁺) at enhanced temperatures. The trends of stable isotopes show slopes in the dD-d¹⁸O diagram which are typical for hydrothermal reactions of evaporation brines with rock or sediments. The genesis of Rotliegend brines differ from Ca-Cl brines in the Canadian Shield, Siberian Platform, the Dry Valleys in Antarctica and even the local brines from the Chilean salars and the Californian Bristol Dry Lake. The Antarctic Dry Valley brines seem to be dominated by melting of ice-cements of their permafrost sections. The Ca-Cl brines of springs in the Chilean salars and the Bristol Dry Lake ascend due to thermal convection along tectonic faults. Although the Canadian Shield brines chemically resemble those of the Siberian Platform their stable isotope fractionation suggest that they developed by different processes of water abstraction. Exotic stable isotope values in brines are gained by freezing or ultrafiltration processes in the precursor sediments of the present crystalline rocks of the Canadian Shield and by small volume ratios of liquids and metamorphic rocks such as of KTB/VB.

DOI: 10.1016/j.chemgeo.2017.04.001

2017076740 Wang, Zhengang (Universite Catholique de Louvain, George Lemaitre Center for Earth and Climate Reserach, Louvain-la-Neuve, Belgium); Hoffmann, Thomas; Six, Johan; Kaplan, Jed O. and Govers, Gerard. Human-induced erosion has offset one-third of carbon emissions from land cover change: Nature Climate Change, 7(5), p. 345-349, illus., 41 ref., May 2017. Based on Publisher-supplied data.

DOI: 10.1038/nclimate3263

2017069994 Jaworski, Tomasz (Nicolaus Copernicus University in Torun, Department of Geomorphology and Palaeogeography of the Quaternary, Torun, Poland). The morphology of peat bog surfaces on Hermansenoya, NW Svalbard: Polar Science, 11, p. 83-95, illus. incl. geol. sketch maps, strat. cols., 34 ref., March 2017.

URL: http://dx.doi.org/10.1016/j.polar.2016.11.006

2017075600 González García, M. (University of Valladolid, Department of Geography, Spain); Serrano Cañadas, E.; Sanjosé Blasco, J. J. and González Trueba, J. J. Surface dynamic of a protalus lobe in the temperate high mountain; western Maladeta, Pyrenees: in Geoecology in Mediterranean mountain areas; tribute to Professor José María García-Ruiz (Nadal-Romero, Estela, editor; et al.), Catena (Giessen), 149(Part 3), p. 689-700, illus. incl. 5 tables, sketch maps, 68 ref., February 2017.

The Maladeta protalus lobe is located in the Maladetas Massif (Central Pyrenees). A detailed geomorphologic map, RTK-GPS techniques, bottom temperature of the winter snowcover (BTS) technique and datalogger to monitor the ground thermal regime were used to reveal the present-day activity of the protalus lobe and its location in a mountain permafrost environment. Systematic monitoring using differential GPS at eight fixed points throughout the surface of the protalus lobe shows vertical and horizontal displacements during the field surveys of 2008, 2009, 2010, 2011, 2012 and 2013. The recorded dynamic defines a periglacial landform with low activity and rapid interannual variations in a thermal imbalance state. The location of protalus lobe in marginal periglacial environments of the temperate high mountain makes it an effective morphoclimatic geoindicator.

DOI: 10.1016/j.catena.2016.08.011

2017073845 Chakraborty, Somsubhra (Uttar Banga Krishi Viswavidyalaya, Cooch Behar, India); Weindorf, David C.; Michaelson, Gary J.; Ping, Chien Lu; Choudhury, Ashok; Kandakji, Tarek; Acree, Autumn; Sharma, Akriti and Wang Dandan. In-situ differentiation of acidic and non-acidic tundra via portable X-ray fluorescence (PXRF) spectrometry: Pedosphere, 26(4), p. 549-560, illus. incl. 4 tables, 55 ref., August 2016.

DOI: 10.1016/S1002-0160(15)60064-9

2017073571 Percival, Jeanne B. (Geological Survey of Canada, Ottawa, ON, Canada) and Williamson, Marie-Claude. Mineralogy and spectral signature of reactive gossans, Victoria Island, NT, Canada: Applied Clay Science, 119(Part 2), p. 431-440, illus. incl. 2 tables, geol. sketch maps, 54 ref., January 2016.

Gossans resulting from the oxidation of sulphide-rich bedrock occur sporadically across Canada, and these features are routinely indicated on geological maps published by the Geological Survey of Canada (GSC). In the Canadian Arctic Islands, some gossans display reactive zones in permafrost characterized by specific textures and mineralogical facies. In poorly-vegetated areas of the High Arctic, gossans can easily be detected on high-resolution satellite imagery. However, the mechanisms leading to their formation are poorly known. For this study, two reactive gossans located in the early Neoproterozoic Minto Inlier of Victoria Island, Northwest Territories, were investigated to determine if the deposits constitute (1) analogues of mine waste in permafrost and (2) vectors to economic resources. Mineralogy was determined in situ using a portable spectroradiometer, with follow-up laboratory measurements. Site 1, Gossan Hill, is a 75-m topographic high capped by a poorly consolidated, rust-coloured layer overlying pyrite-rich sands, and resembles a classic gossan. Site 2, Gossan Sill, underlies a mineralized gabbroic sill consisting of sulphide-rich veins and pods but appears to be inverted morphologically. Visible-Near Infrared-Short Wave Infrared spectral analyses of surficial materials at Gossan Hill indicate gypsum, goethite and jarosite, and X-ray diffraction (XRD) confirms their presence as well as quartz, illite and feldspar. At Sill Gossan, spectral analyses show gypsum and jarosite; XRD indicates variable amounts of goethite, hematite, pyrite, chlorite, calcite and feldspar. The positive relief and presence of concentric alteration zones at Gossan Hill suggest that cryogenic processes, typical of Arctic regions, are active. Water becomes expelled during the freezing cycle forcing material outwards and along with oxidation of the sulphides, forms variably coloured zones in gossanous material. The inverted stratigraphy at Sill Gossan is more problematic. Constant weathering and mass wasting from the overlying sill and pyrite-rich breccia provide fresh pyrite to the gossan on a regular (seasonal) basis. Abstract Copyright (2016) Elsevier, B.V.

DOI: 10.1016/j.clay.2015.05.026

2017075651 Mackelprang, Rachel (California State University, Department of Biology, Northridge, CA); Saleska, Scott R.; Jacobsen, Carsten Suhr; Jansson, Janet K. and Tas, Neslihan. Permafrost meta-omics and climate change: Annual Review of Earth and Planetary Sciences, 44, p. 439-462, illus., 180 ref., 2016.

Permanently frozen soil, or permafrost, covers a large portion of the Earth's terrestrial surface and represents a unique environment for cold-adapted microorganisms. As permafrost thaws, previously protected organic matter becomes available for microbial degradation. Microbes that decompose soil carbon produce carbon dioxide and other greenhouse gases, contributing substantially to climate change. Next-generation sequencing and other -omics technologies offer opportunities to discover the mechanisms by which microbial communities regulate the loss of carbon and the emission of greenhouse gases from thawing permafrost regions. Analysis of nucleic acids and proteins taken directly from permafrost-associated soils has provided new insights into microbial communities and their functions in Arctic environments that are increasingly impacted by climate change. In this article we review current information from various molecular -omics studies on permafrost microbial ecology and explore the relevance of these insights to our current understanding of the dynamics of permafrost loss due to climate change.

DOI: 10.1146/annurev-earth-060614-105126

2017067933 O'Regan, Matt (Stockholm University, Department of Geological Sciences, Stockholm, Sweden); Greenwood, Sarah L.; Preto, Pedro; Sward, Henrik and Jakobsson, Martin. Geotechnical and sedimentary evidence for thick-grounded ice in southern Lake Vattern during deglaciation: GFF, 138(2), p. 355-366, 2016.

A 74-meter Late Pleistocene to Holocene sedimentary sequence was recovered from southern Lake Vättern in the autumn of 2012. At 54 m below the lake floor, shear strength and high-resolution bulk density measurements suggest the presence of an unconformity in the varved proglacial clays. Incremental load consolidation tests reveal highly overconsolidated sediments below this level. Preconsolidation pressures for the underlying sediments are between 1250 and 2100 kPa, up to 1700 kPa more than the current in-situ effective stress. The highly overconsolidated sediments indicate either substantial erosion (the removal of 215-360 m of sediment), or consolidation under a large grounded ice mass sitting up to 230 m above paleo-lake level. Glaciotectonic deformation in underlying sediments supports the interpretation of a grounded ice mass. It is likely that this horizon is either contemporaneous with or older than the Levene moraine, formed between 13.4 and 13.8 ka. In the 30 m of overlying proglacial clays, there is no further evidence for grounded ice, indicating that any ice advance to southern Lake Vättern during the Younger Dryas would have been limited to an extremely thin ice tongue.

DOI: 10.1080/11035897.2015.1055511

2017075341 Abakumov, E. V. (Saint Petersburg State University, St. Petersburg, Russian Federation); Tomashunas, V. M.; Lodygin, E. D.; Gabov, D. N.; Sokolov, V. T.; Krylenkov, V. A. and Kirtsideli, I. Yu. Polycyclic aromatic hydrocarbons in insular and coastal soils of the Russian Arctic: Eurasian Soil Science, 48(12), p. 1300-1305, 28 ref., December 2015. Based on Publisher-supplied data.

The content and individual component compositions of polycyclic aromatic hydrocarbons in polar soils of the Russian Arctic sector have been studied. The contamination of soils near research stations is identified from the expansion of the range of individual polycyclic aromatic hydrocarbons, the abrupt increase in the content of heavy fractions, and the accumulation of benzo[a]pyrene. Along with heavy hydrocarbons, light hydrocarbons (which are not only natural compounds, but also components of organic pollutants) are also accumulated in the contaminated soils. Heavy polycyclic aromatic hydrocarbons are usually of technogenic origin and can serve as markers of anthropogenic impact in such areas as Cape Sterligov, Cape Chelyuskin, and the Izvestii TsIK Islands. The content of benzo[a]pyrene, the most hazardous organic toxicant, appreciably increases in soils around the stations, especially compared to the control; however, the level of MPC is exceeded only for the soils of Cape Chelyuskin. Copyright 2015 Pleiades Publishing, Ltd.

DOI: 10.1134/S1064229315120029

2017075343 Goncharova, O. Yu. (Lomonosov Moscow State University, Soil Science, Moscow, Russian Federation); Matyshak, G. V.; Bobrik, A. A.; Moskalenko, N. G. and Ponomareva, O. E. Temperature regimes of northern taiga soils in the isolated permafrost zone of Western Siberia: Eurasian Soil Science, 48(12), p. 1329-1340, 34 ref., December 2015. Based on Publisher-supplied data.

Soil temperature regimes were studied in three ecosystems of the north of Western Siberia in the zone of isolated permafrost: the forest ecosystem with gleyic loamy sandy podzol (Stagnic Albic Podzol), the flat-topped peat mound ecosystem with humus-impregnated loamy sandy to light loamy peat cryozem (Histic Oxyaquic Turbic Cryosol (Arenic)), and the peat mound (palsa) ecosystem with oligotrophic destructive permafrost-affected peat soil (Cryic Histosol). Annual temperature measurements in the soil profiles demonstrated that these soils function under different temperature regimes: very cold permafrost regime and cold nonpermafrost regime. The following annual temperature characteristics proved to be informative for the studied soils: sums of above-zero temperatures at the depths of 10 and 20 cm, the maximum depth of penetration of temperatures above 10°C, and the number of days with daily soil temperatures above (or below) 0°C at the depth of 20 cm. On the studied territory, the insulating effect of the snow cover in winter was at least two times more pronounced than the insulating effect of the vegetation cover in summer. Cryogenic soils of the studied region are characterized by the high buffering towards changing climatic parameters. This is explained by the presence of the litter and peat horizons with a very low thermal diffusivity and by the presence of permafrost at a relatively shallow depth with temperature gradients preventing penetration of heat to the permafrost table. Copyright 2015 Pleiades Publishing, Ltd.

DOI: 10.1134/S1064229315100038

2017073588 Medvedkov, A. A. (Moscow State University, Faculty of Geography, Moscow, Russian Federation). Geoenvironmental response of the Yenisei Siberia mid-taiga landscapes to global warming during late XX-early XXI centuries: Water Resources, 42(7), p. 922-931, illus. incl. sect., sketch map, 10 ref., December 2015.

The response of middle boreal landscapes in the Yenisei Siberia to climate warming is considered. Changes in the systems of exodynamics, natural permafrost and nonpermafrost landscapes are analyzed based on a series of studies. Permafrost landscapes are ranked by their susceptibility to climate warming. Changes in the habitats were identified. The aggravating problems of the local population in the sphere of the use of taiga resources, characterizing the current stage of changes in the environment and climate are demonstrated. Copyright 2015 Pleiades Publishing, Ltd.

DOI: 10.1134/S0097807815070076

2017073744 Komurlu, Eren (Karadeniz Technical University, Department of Mining Engineering, Trabzon, Turkey) and Kesimal, Ayhan. Experimental study of polyurethane foam reinforced soil used as a rock-like material: Journal of Rock Mechanics and Geotechnical Engineering, 7(5), p. 566-572, illus. incl. 8 tables, 21 ref., October 2015. Based on Publisher-supplied data.

In this study, polyurethane foam type thermoset polymerizing, due to chemical reaction between its liquid ingredients, was tested as binder after solidifying and then a rock-like material mixing with a sandy silt type soil was prepared. The uniaxial compressive strengths (UCSs) of polyurethane foam reinforced soil specimens were determined for different polyurethane ratios in the mixture. Additionally, a series of tests on slake durability, impact value, freezing-thawing resistance, and abrasion resistance of polyurethane reinforced soil (PRS) mixture was conducted. The UCS values over 3 MPa were measured from the PRS specimens. The testing results showed that treated soil can economically become a desirable rock-like material in terms of slake durability and resistances against freezing-thawing, impact effect and abrasion. As another characteristic of the rock-like material made with polyurethane foam, unit volume weight was found to be quite lower than those of natural rock materials.

DOI: 10.1016/j.jrmge.2015.05.004

2017073007 Walker, H. Jesse and McGraw, M. Maintaining the integrity of the environment in an Arctic delta during modernization: in Human impacts on landscapes; sustainability and the role of geomorphology (Hudson, Paul, editor; et al.), Zeitschrift für Geomorphologie, 59, Suppl. 2, p. 137-153, 26 ref., May 2015.

Many parts of the Arctic are being modified by ever-increasing rates of political, industrial and commercial activity. Early developers gave little thought about their effect on the environment. One area now being subjected to modernization is the Colville River Delta in Arctic Alaska, USA. Although long a key location for Inuit fishing and hunting, remnants of their presence are a few turf-house foundations. Major changes began in 1973 when the town of Nuiqsut was founded. About the same time, the integrity of the Arctic was becoming a major concern, a concern that led to numerous governmental and industrial regulations. Changes to the Delta include the construction of numerous buildings insulated from the fragile tundra surface, the development of two major runways, the construction of a large oil field and its pipelines, and a road system. Successful construction in a permafrost-dominated landscape demands techniques that preserve its frozen characteristic. The geomorphic impact on the Delta has been minimal primarily for two reasons: strict regulation of construction on the North Slope and the recency of its development allowing developers to take advantage of the technological improvements that accompany arctic engineering.

DOI: 10.1127/zfg_suppl/2015/S-59208

2017072138 Agatova, Anna R.; Nepop, Roman and Bronnikova, Maria. Outburst floods of the ice-dammed lakes in the SW of Tuva, southern Siberia: in Hydrological extreme events; modelling and significance for understanding global change, demonstrating multidisciplinary context (Herget, Jürgen, editor; et al.), Zeitschrift für Geomorphologie, 59, Suppl. 3, p. 159-175, illus., 33 ref., 2015.

We conducted a preliminary study of high mountain depressions of the SW Tuva (Mountains of Southern Siberia). For the first time the hydrological system transformation and landscape evolution in the region was considered in detail in relation to the cataclysmic outburst floods of ice-dammed lakes. The paper presents the geological and geomorphological evidence of ice-dam lake development and drainage within the Dzhulukul, Khindiktik-Kol', Akhol' basins. Multidisciplinary investigations including geomorphological and geoarchaeological approaches, lithostratigraphic and pedogenetic analysis accompanied by radiocarbon dating were applied to reconstruct the landscape evolution. The new data suggests the existence of significantly larger lakes which relate to the degradation of extensive Pleistocene ice-sheet glaciations. Floods from these lakes, including those from the palaeo Dzhulukul, where modern runoff goes northward into the Arctic Ocean basin, flowed southward into the Mongolian Inland Drainage Basin. Together with the more humid climate, the significant water supply from the lakes within the Dzhulukul depression (Dzhulukul, Khindiktik-Kol', Akhol') is another factor that controlled much higher former lake levels in the northern part of the Great Lakes Basin, which was not previously considered. The most obvious evidence of palaeolake development is preserved in the Akhol' Basin. Associated landforms and available absolute dates indicate four main stages of lake development. The first stage started no later than 14000 cal. years BP and was characterized by the maximal water level at about 2380 m a. s. l. (180 above present). Partial lake drainage down to 2270 m a. s. l. marks the second stage which ended before 8000 years BP. There are no sufficient data to clearly separate the next two stages of lake evolution. The level 2220 m a. s. l. was quite prolonged before final draining to approximately the modern state. During this time there were only climatically driven oscillations of the lake level and in these final stages the soils developed about 3000 - 3500 cal. years BP and the Akhol' Basin was settled by nomads as- sociated with the Saglyn Culture of the Scythian epoch (6th - 2nd centuries BC).

DOI: 10.1127/zfg_suppl/2015/59203

2017072131 Fölmli, Christian (Universität Bern, Geologisches Institut, Bern, Switzerland); Herwegh, Marco; Schlunegger, Fritz and Anselmetti, Flavio S. Murgänge und Felsstürze im Gebiet Ritzlihorn-Spreitgraben, Guttannen BE; analyse der Felskonditionierung und des Mur- und Sturzkegels [Debris flows and rockfalls in the Ritzlihorn-Spreitgraben area, Guttannen; an analysis of rock conditions and of mud- and debris cones]: Swiss Bulletin für Angewandte Geologie, 20(2), p. 47-69 (English sum.), 55 ref., 2015.

Debris flows are some of the most erosive processes in mountainous regions. In the area of the Ritzlihorn-Spreitgraben system, several debris flow events occurred in the years 2009-2011 with historically unprecedented high frequency and magnitude. This study shows that the events of the years 2009-2011 are three to five times larger than those in the past between 14 to 8 ky, which built up the fan of Guttannen with a total volume of about 257 Mio m3 of unconsolidated material. In the period from 8 ky up to the year 2009 the system indicates only slight debris flow and rockfall activity. The Ritzlihorn-Spreitgraben system has therefore changed from first active accumulative to a slightly active, up to an again strongly active though erosive debris flow and rockfall system since 2009. The future debris flow activity seems to be strongly coupled with the rock falls. Based on the strong degree of disintegrated gneisses of the Guttannen zone near the Ritzlihorn, large amounts of unconsolidated or only ice-cemented bedrock material occurs in the summit region. Due to the on-going permafrost degradation and the predicted temperature rise, an increased rockfall activity has to be expected in the area in the following decades. This may imply a further high debris flow frequency and magnitude with event sizes comparable with those in the years 2009-2011.

URL: https://www.e-periodica.ch/cntmng?pid=vsp-004:2015:20::231

2017069441 Kerguillec, Riwan; Sellier, Dominique and Beylich, Achim A. An example of a periglacial recovery; the slope of Sletthoi (Dovrefjell, central Norway): Zeitschrift für Geomorphologie, 59(2), p. 173-196, 33 ref., 2015.

The massif of Dovrefjell is part of the Scandes Mountains and lies near the 62nd parallel and the 9th east meridian. Snohetta (2,286 m a.s.l.) is its highest summit (glacial belt). In these mountains, periglacial activity is determined by the observation of authentic periglacial features at 900 m a.s.l. The standard periglacial belts include three successive levels in which the morphological indicators of periglacial activity are increasingly developed with altitude. However, research carried out on the slope of Sletthoi (1,441 m), a peripheral mountain of Snohetta, shows that it disrupts the regularity of the layout of these belts. Sletthoi displays periglacial features which do not seem to be in accordance with altitude, thus raising the problem of their morphodynamic significance. The surveys show an example of a recent periglacial recovery in a neve site from the Little Ice Age, in relation to thawing permafrost. They underline the spatial and temporal irregularities of the functional periglacial belt.

DOI: 10.1127/0372-8854/2014/0144

2017069395 Popescu, Razvan; Vespremeanu-Stroe, Alfred; Onaca, Alexandru and Cruceru, Nicolae. Permafrost research in the granitic massifs of southern Carpathians (Parang Mountains): Zeitschrift für Geomorphologie, 59(1), p. 1-20, 35 ref., 2015.

Thermal and geoelectrical methods were used to detect permafrost in rock glaciers, block fields, talus slopes and rockwalls in the granitic alpine area of Parang Mountains where large rock deposits exist above the timberline. Variability of debris porosity at different sites, with and without permafrost, was preliminary assessed by measuring the clasts dimensions. The lower limits for permafrost occurrence and creep within debris-built landforms were found at 1,950 m and 2,100 m, respectively. The mean annual rock temperatures suggested conducive conditions for permafrost occurrence in northward exposed rockwalls above 2,350 m. DC resistivity profiles revealed relative thin permafrost (5-15 m) with medium to low ice content in tongue shape rock glaciers below 2,050 m, and thicker permafrost (> 20 m) with medium ice content in lobate rock glaciers above the mentioned altitude. It is assumed that about a half of permafrost areas in Parang Mountains are in thermal disequilibrium with the present climate. Our multiple investigations in Southern Carpathians show that the main factor influencing the downslope extension and hence the conventional lower limit of the permafrost specific to granitic massifs is the high porosity of unconsolidated debris deposits.

DOI: 10.1127/0372-8854/2014/0145

2017072995 Leopold, Matthias; Völkel, Jörg; Dethier, David P. and Williams, Mark W. Changing mountain permafrost from the 1970s to today; comparing two examples from Niwot Ridge, Colorado Front Range, USA: in Climatic signals in geomorphological systems; approaches from aeolian, fluvial, colluvial, periglacial, coastal, and man-made geomorphological systems (Zielhofer, Christoph, editor; et al.), Zeitschrift für Geomorphologie, 58, Suppl. 1, p. 137-157, 59 ref., 2014.

Melting mountain permafrost is reported from alpine areas around the world as a direct consequence of rising air temperatures over the past decades. However, alpine sites that offer sufficient older data to compare with recent conditions are rare. The study site Niwot Ridge, situated at 3600 m a.s.l. in the Front Range of the Rocky Mountains, Colorado, USA, offers permafrost distribution data from the early 1970s. We used four different approaches to evaluate and compare the old data with recent conditions and to discuss consequences in how the old data should be considered. (i) Air photographs and survey stakes were used to compare modern surface conditions of a solifluction lobe with those in the past. Despite high resolution of the air photographs (0.3 m), the error of position after geo-rectification was higher (± 1.0 m) than average displacement rates of gelifluction lobes (10 mm/a), rendering this approach unsuitable. Replication of a 1963-1967 study of soil movement from 2006-2009 yielded average movement rates of 11.4 mm/a compared to 9.4 mm/a in the 1960s. (ii) Temperature profiles of a three-year survey (2007-2009) to depths of 7 m were compared with data from the 1970s from the same site. Modern temperature profiles document a complex annual curve that includes several weeks of unfrozen conditions, this finding is in contrast with the permafrost conditions reported from the 1970s. (iii) Electric resistivity profiles on a gelifluction lobe, surveyed in different seasons during the year, show the freezing front down to 2 m depth during the early winter, the melting process during spring conditions and the complete melt of all ice lenses during the summer months. Geophysical results corroborate data from nearby temperature loggers and were used to extend the survey to other areas on Niwot Ridge. (iv) A simple 1 D-heat flow model was driven by the annual temperature variations of 1972 and 2008, resulting in several weeks of unfrozen conditions at various depths but with temperatures close to freezing during the 1970s. Our study documents that at present, on south facing slopes, permafrost neither exists at 2 m depth on wet sites nor at 4 m depth on dry sites as suggested during the 1970s.

DOI: 10.1127/0372-8854/2013/S-00129

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2017073081 Badu, Yu. B.; Gafarov, N. A. and Podbornyy, E. E., editors. Kriosfera neftegazokondensatnykh mestorozhdeniy poluostrova Yamal; T. 2, Kriosfera Bovanenkovskogo neftegazokondensatnogo mestorozhdeniya [Cryosphere of oil, gas and condensate fields in the Yamal Peninsula; Volume 2, Cryosphere of the Bovanenkovo oil, gas and condensate field]: Gazprom Ekspo, Moscow, Russian Federation, 424 p., illus. incl. 96 tables, sects., strat. cols., sketch maps, 133 ref., 2013.

Environmental conditions of cryosphere, geological structure, state, composition and properties of cryogenic formation grounds in the Bovanenkovskoye oil and gas condensate field (Yamal Peninsula) are considered. Specific features of the cryosphere: gas occurrences from frozen rock masses, formation of ice deposits, polygonal-veiny ices, salinization of soils, and cryopegs are characterized in detail. Geocryological zoning of frozen formations is carried out.

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2017071104 Murray, Renaud. Bilan hydrologique d'un bassin versant dans la région d'Umiujaq au Québec nordique [Hydrological assessment of a watershed in the Umiujaq region of northern Quebec]: 118 p. (English sum.), illus. incl. 10 tables, 41 plates, 95 ref., Master's, 2016, Université Laval, Sainte-Foy, QC, Canada. Includes appendices.

Nunavik's communities rely mainly on surface water. Several constraints, such as treatment costs and drying-up in the winter, motivate the search for an alternative. The availability of groundwater in the northern region is limited, due to the presence of permafrost. Moreover, the sustainable exploitation of groundwater in the Nordic region remains to be demonstrated, as groundwater recharge processes and the dynamics of groundwater flows are different from those observed in temperate regions. The main objective of the project is to assess the availability of groundwater for drinking water supply of a northern community. The water budget of a 2.1 km² watershed in the Tasiapik Valley near the Umiujaq community (Nunavik) was carried out between July 2014 and July 2015. The total precipitation was evaluated using environment Canada data's for a sum of 520 mm. Potential and actual evapotranspiration were calculated using the Hydro-Quebec equations (Bisson and Roberge, 1983) and Budyko (1974) for respective values of 330 mm and 192 mm. The installation of a gauging channel in the main stream made it possible to evaluate the discharge at the outlet for a total of 280 mm. Storage in surface and underground reservoirs were estimated by closing the surface water budget and represents 48 mm. Groundwater recharge was characterized according to the Darcy method by the instrumentation of four sites covered by different vegetation. Thus, the average recharges over the entire catchment area represents 207 mm, which corresponds to about 40% of the total precipitation. In addition, the watershed experiences one recharge episode per year, which is different from the two episodes normally observed in southern Quebec. The reason behind this phenomenon is firstly related to a shorter summer and to the late melting of snow caused by the type of vegetation. Then, the base flow is estimated by the hydrograph separation technic. The average calculated flow rate correspond to an equivalent of water of 193 mm. This represents 69% of the total flow, which is characteristic of regions without permafrost. This result, however, is not surprising considering that permafrost is present in small quantity in the watershed and is found exclusively in the form of isolated mounds. As a result, its impact on underground flows is limited, not to mention the fact that it is present in a layer of silt that is poorly permeable, even in the absence of permafrost. On the other hand, discharge at the outlet is influenced by groundwater from other watersheds, which partly explains the high value obtained. The transfer of groundwater between catchments, which is obtained by closing the groundwater water budget, corresponds to a water supply of 34 mm coming from the adjacent catchments. This estimate seems consistent with the characteristics of the study site. Indeed, the latter is located in a valley surrounded by a cuesta and a hill both having an important relief. These characteristics mean that the groundwater watershed is larger than the surface watershed. Groundwater discharges can also be used to estimate the amount of water that can be used for sustainable development. The equivalent water of this parameter has a value of 193 mm, which represents 405 300 000 litres of water. The watershed therefore contains enough of this resource to meet the village's needs, since the community uses about 18,370,450 litres of water per year, or 4.5% of the available resource. The field campaigns also allowed the sampling in order to analyze the chemistry of water. These results were then compared with the maximum acceptable drinking water concentrations from the Government of Quebec's Drinking Water Quality Regulation (MDDELCC, 2016) and the aesthetic objectives of Health Canada (2016). The conclusion is that the water is drinkable, but that it exceeds the limit with respect to manganese, which is not a problem, since this element is mostly harmful to the laundry and for plumbing equipment. However, some elements have not been analyzed and a thorough examination of the bacteriological standards is necessary in order to determine with certainty the potability of this groundwater.

URL: http://www.theses.ulaval.ca/2016/32899/

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2017076219 Duroe, Kiersten (Kent State University, Department of Geology, Kent, OH); Mills, Jonathan; Kinsman-Costello, Lauren E. and Herndon, Elizabeth. Iron redox cycling and impacts on phosphorus solubility in tundra and boreal ecosystems [abstr.]: in Geological Society of America, Northeastern Section, 52nd annual meeting; Geological Society of America, North-Central Section, 51st annual meeting, Abstracts with Programs - Geological Society of America, 49(2), Abstract no. 40-6, 2017. Meeting: Geological Society of America, Northeastern Section, 52nd annual meeting; Geological Society of America, North-Central Section, 51st annual meeting, March 19-21, 2017, Pittsburgh, PA.

Rapidly changing climate in high-latitude regions is altering biogeochemical cycles and potentially shifting Arctic and sub-Arctic ecosystems from sinks to sources of atmospheric carbon. Phosphorus (P) is an important nutrient whose availability may limit biological productivity, plant growth, and carbon storage in northern ecosystems. Microorganisms control the release of inorganic phosphate from decomposing organic matter and make it available for plant uptake. However, phosphate sorbs strongly to soil minerals such as iron (Fe) oxides, and bioavailability may also be regulated by microbially mediated iron oxidation/reduction transformations. Here, we investigate the potential for phosphate adsorption to iron oxide minerals that precipitate during drainage of anoxic, Fe-rich peat soils to limit P bioavailability in high-latitude peatlands. We compare Fe and P geochemistry in peat soils collected from relatively depressed and saturated microtopographic positions to elevated and dry positions along a latitudinal gradient in northern North America, including tundra (Barrow Environmental Observatory, AK; Toolik Lake Field Station, AK) and boreal (Bonanza Creek Environmental Forest, AK; Marcell Experimental Forest, MN) ecosystems. Differences in soil saturation generated by microtopography serve as a proxy for hydrologic changes driven by altered climate and permafrost degradation. To assess P sorption to Fe-oxides, we used a phosphate sorption index to evaluate the capacity for soils to bind phosphate and sequential extractions to quantify Fe phases including poorly-crystalline and crystalline iron oxides. Our results indicate that phosphate sorption capacity differs across microtopographic gradients that may reflect the position of Fe-oxide accumulation at oxic-anoxic interfaces. Consequently, projected temperature increases in Arctic and sub-Arctic regions may influence P availability due to increased association with iron oxides that precipitate as water tables lower in drying peatlands.

2017076320 Finkelstein, Sarah A. (University of Toronto, Department of Earth Sciences, Toronto, ON, Canada); Hargan, Kathryn E.; Ruhland, Kathleen M.; Packalen, Maara; Smol, John P.; Keller, Wendel and Paterson, Andrew M. A multi-proxy record of Holocene paleoclimate and paleolimnological change from North Raft Lake, Hudson Bay Lowlands, northern Ontario, Canada [abstr.]: in Geological Society of America, Northeastern Section, 52nd annual meeting; Geological Society of America, North-Central Section, 51st annual meeting, Abstracts with Programs - Geological Society of America, 49(2), Abstract no. 53-1, 2017. Meeting: Geological Society of America, Northeastern Section, 52nd annual meeting; Geological Society of America, North-Central Section, 51st annual meeting, March 19-21, 2017, Pittsburgh, PA.

The Hudson Bay Lowlands (HBL) is an extensive peatland extending over 372,000 km² in northern Manitoba, Ontario and Quebec, Canada. Over the Holocene, >31 Pg of carbon have accumulated in the bog and fen habitats across the region. The region is presently subject to significant warming and permafrost thaw, and paleoenvironmental records are critical for understanding the fate of peatland carbon under different climatic regimes. While a variety of paleoecological studies of peat cores from the region are contributing to an emerging picture of peatland development in response to climatic, hydrological and ecological processes, paleolimnological records derived from lake sediments are a critical source of paleoclimatic records independent from peatland processes. While lakes are abundant in the HBL region, the majority are shallow (Z<1 m) and do not preserve whole-Holocene sediment sequences. North Raft Lake (54.53°-84.76°W; 113 m asl) is situated in the vicinity of the Sutton Ridge in the northeastern sector of Ontario's Hudson Bay Lowlands. With a depth of ~11 m, North Raft Lake contains a continuous middle to late Holocene sedimentary sequence 1.5 m in length. Initial sediments are carbonate-rich, low in pollen, and contain marine shells and abundant marine dinoflagellate cysts, suggesting inundation by the Tyrell Sea (the proto-Hudson Bay). Pollen taxa present include Chenopodiaceae, Shepherdia canadensis and shrub Betula and Salix, indicative of tidally influenced salt marsh vegetation. Isostatic uplift gradually reduced marine influence, and by the middle Holocene, sediment organic matter increased above 5%, pollen concentrations increased and assemblages indicate establishment of a closed-basin freshwater lake. Tree pollen assemblages suggest local presence of boreal-type forested peatlands dominated by Picea and Larix, with Alnus, Cupressaceae, Ericaceae and Populus present as well. This assemblage was relatively stable through to present day, with few shifts in the pollen stratigraphy. Chironomid head capsules were also well preserved in the North Raft sediments; assemblage changes suggest mid-Holocene warming across the HBL, with increases in lake water temperatures and/or lake littoral habitat.

2017074228 Morse, P. D., compiler (Geological Survey of Canada, Ottawa, ON, Canada). Report on the Permafrost and hydrogeology interactions meeting: Open-File Report - Geological Survey of Canada, Rep. No. 8192, 60 p., 2017. (Northwest Territories Geological Survey, NWT Open Report, No. 2017-010). Meeting: Permafrost and hydrogeology interactions meeting, Nov. 14, 2016, Yellowknife, NT, Canada. Individual abstracts are not cited separately.

Presently, no comprehensive view exists of the relations between permafrost and hydrogeology in varying Northern conditions. Similarly, the responses with climate change remain poorly understood. These are critical knowledge gaps, as climate change impacts on permafrost are likely to alter hydrologic cycles, groundwater flow networks, and surface water supplies. Communities, governments, regulators, industry, and academics are noting process changes in the North. Regulators need guidance on how to scope groundwater and permafrost issues as they affect economic development. Northern capacity to address issues facing Northern society is limited, so knowledge must come through collaboration and engagement. A meeting of 27 government, academic, and industry researchers and practitioners was held to address these issues. A plan was developed to scope out the State of Knowledge on permafrost and hydrogeology interactions. This report documents meeting-related materials and minutes.

DOI: 10.4095/299674

2017070320 Burd, Katheryn (University of Alberta, Edmonton, AB, Canada); Tank, Suzanne; Olefeldt, D. and Estop Aragones, Cristian. Impacts of wildfire and permafrost thaw on sources and downstream fate of dissolved organic carbon in subarctic peatland-rich catchments [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0427, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Northern peatlands have accumulated vast stores of organic carbon since the last deglaciation, and peatlands are often substantial sources of exported dissolved organic carbon (DOC) from boreal catchments. In order to better understand the carbon balance at catchment scales, it is important to consider peatland DOC export and its downstream mineralization into greenhouse gases. Current literature disregards the importance of freshwater DOC cycling in global carbon models. The taiga plains of western Canada is a subarctic region with extensive peatland complexes comprised of treed peat plateaus with permafrost, as well as non-permafrost thermokarst bogs. In this region, the warming climate is predicted to increase the rate of permafrost thaw and the frequency and intensity of wildfires. In this study we investigated the impacts of wildfire and permafrost thaw on peatland pore water DOC chemistry and microbial lability through an incubation experiment, while simultaneously monitoring downstream DOC export in paired unburned and recently burned peatland-rich catchments. Three 28-day incubations were conducted to determine the microbial lability of DOC using a factorial design that tested the effects of both thaw and fire. CO₂ production in DOM incubations from recently developed thermokarst bogs were 4-50 times greater than from any of the other locations where pore water was collected. These results suggest that permafrost thaw is likely to increase peatland DOC export to and CO₂ emissions from downstream aquatic ecosystems. Conversely, DOC from burned peatlands has lower microbial lability than their paired unburned peatland ecosystems. Furthering our understanding of freshwater DOC dynamics, particularly after a disturbance, will help us better understand the potential impacts of climate change on catchment-scale carbon cycling.

2017070321 Eickmeyer, David (University of Ottawa, Ottawa, ON, Canada); Kimpe, Linda; Kokelj, Steve; Pisaric, Michael F. J.; Smol, John P.; Sanei, Hamed; Thienpont, Joshua R. and Blais, J. M. Interactions of polychlorinated biphenyls and organochlorine pesticides with sedimentary organic matter of retrogressive thaw slump-affected lakes in the tundra uplands adjacent to the Mackenzie Delta, NT, Canada [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0428, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Increased incidences and severity of thermokarst activity, such as retrogressive thaw slumping, in the permafrost-rich western Canadian Arctic have been previously shown to influence basic water chemistry and sedimentation rates of affected lakes. Using a comparative spatial analysis of sediment cores from 8 lakes in tundra uplands adjacent to the Mackenzie Delta, NT, we examined how the presence of retrogressive thaw slumps on lake shores affected persistent organic pollutant (POPs, including polychlorinated biphenyls (PCB), hexa- and pentachlorobenzenes (CBz) and dichlorodiphenyltrichloroethane and metabolites (DDT)) accumulation in lake sediments. Sediments of slump-affected lakes contained higher total organic carbon (TOC)-normalized POP concentrations than nearby reference lakes that were unaffected by thaw slumps. PCB and DDT deposition rates to the sediment were not significantly different between reference and affected lakes; however, CBz flux to sediment was found to be higher in slump-affected lakes. Mean focus-corrected inorganic sedimentation rates were positively related to TOC-normalized contaminant concentrations, explaining 58-94% of the variation in POP concentrations in sediment, suggesting that reduced organic carbon in slump-affected lake water results in higher concentrations of POPs on sedimentary organic matter. This explanation was corroborated by an inverse relationship between sedimentary POP concentrations and TOC content of the lake water. Higher POP concentrations observed in sediment of slump-affected lakes are best explained by simple solvent switching processes of hydrophobic organic contaminants onto a smaller pool of available organic carbon when compared to neighboring lakes unaffected by thaw slump development.

2017070364 Fritz, M. (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Periglacial Research, Potsdam, Germany); Tanski, G.; Goncalves-Araujo, Rafael; Heim, B.; Koch, B. and Lantuit, H. Dissolved organic matter properties in arctic coastal waters are strongly influenced by degrading permafrost coasts and by local meteorology [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-05, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Organic carbon and nutrients are increasingly mobilized from permafrost coasts due to accelerated coastal erosion in response to Arctic warming. The nearshore zone plays a crucial role in Arctic biogeochemical cycling, as here the released material is destined to be (1) mineralized into greenhouse gases, (2) incorporated into marine primary production, (3) buried in nearshore sediments or (4) transported offshore. We present dissolved organic matter (DOM) quantities in surface water in the nearshore zone of the southern Beaufort Sea from three consecutive summer seasons under different meteorological conditions. Colored and fluorescent dissolved organic matter (cDOM, fDOM) properties are used to differentiate the terrestrial from the marine DOM component. Dissolved organic carbon (DOC) concentrations in the nearshore zone of the southern Beaufort Sea vary between about 1.5 and 5 mg C L^-1. In low salinity conditions between 8 and 15, high DOC concentrations of 3.5 to 5 mg C L^-1 prevail. Storm events can lead to strongly decreased DOC concentration and increasing salinity (14 to 28) in surface water, probably due to upwelling. In windy and wavy conditions throughout the season, the water column is well-mixed and DOC-poor because saline waters are transported from the offshore to the nearshore. We recognized a significant negative correlation between DOC and salinity, independent from varying meteorological conditions. This suggests conservative mixing between DOC derived from permafrost coasts and marine primary production. Stable stratification in the nearshore zone and calm weather conditions will increase the influence of terrestrial-derived DOM and the potential turnover time for biogeochemical cycling in coastal ecosystems. The strength of the terrestrial influence can be estimated by salinity and stable water isotope measures as they directly correlate with DOC concentrations; the lower the salinity the stronger the terrestrial influence. We conclude that the terrestrial footprint of coastal erosion on DOM concentrations in the nearshore zone is significant and may increase with future climate warming. Meteorological conditions play a major role for the strength of the terrestrial DOM signal, which can vary on short timescales.

2017070362 Gaglioti, B. (Lamont-Doherty Earth Observatory, Palisades, NY); Mann, D. H.; Farquharson, L. M.; Jones, B. M.; Wooller, M. J.; Baughman, C. A.; Groves, P.; Kunz, M.; Pohlman, J.; Wiles, G. C. and Reanier, R. Peat insulation moderates the sensitivity of permafrost carbon to climate warming in Arctic Alaska [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Continued warming in the Arctic may cause permafrost to thaw and release large amounts of soil carbon (C) both downstream and into the atmosphere. Understanding how permafrost C responded to prehistoric warming events can tell us how sensitive this process is. We investigated how soil and permafrost C budgets responded to paleo-warming events over the last 40,000 years in Arctic Alaska. In this presentation we first describe paleoclimatic changes using oxygen isotope ratios in ancient willow wood, which is a proxy for air temperature and sea-ice-extent. We then quantify how much permafrost C was released from watersheds using radiocarbon (¹⁴C) age-offsets in lake sediment. Stepped-temperature ¹⁴C analysis constrains both the age and quality of discreet organic matter sources that were vulnerable to thaw. Results showed that during the relatively warm Bolling-Allerod period (B-A; 14,700-12,800 cal years ago) and Holocene Thermal Maximum (HTM; 11,700-8500 cal years ago), ¹⁴C age-offsets were 2-3x their modern levels, and up to 10x more ancient C was being released, indicating significant permafrost thaw in the surrounding watershed. Deep, Yedoma C from ice age deposits was vulnerable to thaw during the BA period, but not during the HTM warming. This enhanced release of ancient C during the BA and HTM was interrupted during the cold and dry Younger Dryas interval (YD; 12,800-11,700 cal years ago) when age-offsets were reduced. Even though recent air temperatures are comparable to those estimated for the warm HTM, age-offsets today are relatively low, and similar to the cold YD. This pattern suggests that the insulating peat layer that has accumulated in the region since the early Holocene is stabilizing permafrost C in the face of recent warming. To estimate the capacity of this peat-buffering feedback to protect permafrost from thaw, we compare these paleo-results with permafrost modeling simulations involving peat covers varying in thickness and moisture content.

2017070361 Grosse, G. (Alfred Wegener Institute Helmholtz-Center for Polar and Marine Research Potsdam, Potsdam, Germany); Sannel, Britta; Abbott, B. W.; Arp, C. D.; Camill, P.; Farquharson, L. M.; Günther, F.; Hayes, D. J.; Jones, B. M.; Jorgenson, T.; Kokelj, S. V.; Kuhry, P.; Lenz, Josefine; Liu, L.; McGuire, A. D.; Morgenstern, A.; O'Donnell, J. A.; Nitze, Ingmar; Olefeldt, D.; Parsekian, A.; Romanovsky, V. E.; Schuur, E.; Turetsky, M. R.; Walter Anthony, K. M. and Wullschleger, S. D. A synthesis of thermokarst and thermo-erosion rates in northern permafrost regions [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-01, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Permafrost regions have been identified to host a soil organic carbon (C) pool of global importance, storing more than 1500 PgC. A large portion of this C pool is currently frozen in deep soils and permafrost deposits. Amplified climate change in Polar Regions and associated permafrost thaw hence may result in mobilization of large amounts of C as greenhouse gases, dissolved organic C, or particulate organic matter, with substantial impacts on C cycling and C pool distribution. Understanding potential consequences and feedbacks of permafrost degradation therefore requires better quantification of processes and landforms related to thaw. While many predictive land surface models consider a gradual increase in the average active layer thickness across the permafrost domain, rapid shifts in landscape topography and surface hydrology caused by thaw of ice-rich permafrost are much more difficult to project. Field studies of thermokarst and thermo-erosion indicate highly complex and rapid landscape-ecosystem feedbacks. Contrary to gradual top-down permafrost thaw that may affect any permafrost type at the surface, both thermokarst and thermo-erosion are considered pulse disturbances that are linked to presence of near-surface ice-rich permafrost, are active on short sub-annual to decadal time scales, and may affect C stores tens of meters deep. Here we present a comprehensive review synthesizing measured and modeled rates of thermokarst and thermo-erosion processes from the scientific literature and own observations across the northern hemisphere permafrost regions. The goal of our synthesis is (1) to provide an overview on the range of thermokarst and thermo-erosion rates that may be used for parameterization of thermokarst and thermo-erosion in ecosystem and landscape models; and (2) to assess simple back-of-the-envelope scenarios of the magnitude of C thaw due to thermokarst and thermo-erosion versus projected active layer thickening. Example scenarios considering thermokarst lake expansion and talik growth relying on existing lake databases indicate that these processes have a high possibility to contribute substantially to permafrost C mobilization over the coming century. For thermo-erosion processes, scenario development is challenging due to lack of spatial databases for such features.

2017070282 Heikoop, J. M. (Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos, NM); Newman, B. D.; Arendt, C. A.; Andresen, C. G.; Lara, M. J.; Wainwright, Haruko M.; Throckmorton, H.; Graham, D. E.; Wilson, C. J.; Wullschleger, S. D.; Romanovsky, V. E.; Bolton, W. R.; Wales, Nathan A. and Rowland, J. C. The nitrate inventory of unsaturated soils at the Barrow Environmental Observatory; current conditions and potential future trajectories [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B33B-0587, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Studies conducted in the Barrow Environmental Observatory under the auspices of the United States Department of Energy Next Generation Ecosystem Experiment (NGEE) - Arctic have demonstrated measurable nitrate concentrations ranging from <1 to 17 mg/L in the unsaturated centers of high-centered polygons. Conversely, nitrate concentrations in saturated areas of polygonal terrain were generally below the limit of detection. Isotopic analysis of this nitrate demonstrates that it results from microbial nitrification. The study site currently comprises mostly saturated soils. Several factors, however, could lead to drying of soils on different time scales. These include 1) topographic inversion of polygonal terrain associated with ice-wedge degradation, 2) increased connectivity and drainage of polygon troughs, similarly related to the thawing and subsidence of ice-wedges, and 3) near-surface soil drainage associated with wide-spread permafrost thaw and active layer deepening. Using a GIS approach we will estimate the current inventory of nitrate in the NGEE intensive study site using soil moisture data and existing unsaturated zone nitrate concentration data and new concentration data collected in the summer of 2016 from high- and flat-centered polygons and the elevated rims of low-centered polygons. Using this baseline, we will present potential future inventories based on various scenarios of active layer thickening and landscape geomorphic reorganization associated with permafrost thaw. Predicted inventories will be based solely on active layer moisture changes, ignoring for now potential changes associated with mineralization and nitrification of previously frozen old organic matter and changes in vegetation communities. We wish to demonstrate that physical landscape changes alone could have a profound effect on future nitrate availability. Nitrate data from recent NGEE campaigns in the Seward Peninsula of Alaska will also be presented.

2017070358 Helbig, M. (Université de Montréal, Département de géographie, Montreal, QC, Canada); Chasmer, L.; Desai, A. R.; Quinton, W. L.; Kljun, N. and Sonnentag, O. Direct climate warming effects exceed indirect impacts of permafrost thaw on boreal landscape net CO₂ exchange [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41J-03, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Net CO₂ exchange of boreal forest-wetland landscapes in the sporadic permafrost zone may be altered directly by a changing climate and indirectly by permafrost thaw-induced wetland expansion. How the combined effects impact net landscape CO₂ exchange (NLE) remains unknown. Here, we quantify the indirect land cover change impact on NLE and the direct climate change impact on potential NLE. To resolve spatial differences in net CO₂ exchange across a rapidly thawing boreal forest-wetland landscape in northwestern Canada, we combined nested eddy covariance flux tower measurements (on a landscape and ecosystem scale) with footprint modelling. With -13 g C m^-2 the annual NLE was similar to the -19 g C m^-2 annual net ecosystem exchange of the permafrost-free wetland. Both gross primary production (GPP) and ecosystem respiration (ER) were larger at the landscape-level compared to the wetland. Thus, wetland expansion and concurrent forest loss may change the magnitude of GPP and ER, but its impact on NLE appears to be small. To assess direct climate impacts on potential NLE, we combined downscaled climate projections (RCP4.5 and RCP8.5; 2091-2100) of air temperature (T_a) and incoming shortwave radiation (SW_in) with measured NLE. Maximum potential GPP for daily T_a and SW_in was derived using boundary line analysis of the partitioned GPP. An ER model was constructed using daily T_a and ER. Warmer T_a in spring and fall are expected to reduce the current T_a-limitation of GPP in the shoulder seasons. At the end of the century, an average of 18 days in June are projected to be T_a-limited compared to 29 days for 2006-2015 (RCP8.5). In October, the number of T_a-limited days decreases from 24 to 10 whereas the number of SW_in-limited days increases from 5 to 20 (RCP8.5). Overall, projected climate change increases potential GPP in spring and fall and ER throughout the year. Combined, the current annual potential NLE of -218 g C m^-2 is reduced to -193 g C m^-2 (RCP4.5) and -92 g C m^-2 (RCP8.5). How NLE will change in the future is therefore likely more influenced by direct climate change impacts than by thaw-induced land cover change.

2017070341 Herndon, E. (Kent State University Kent Campus, Kent, OH); AlBashaireh, Amineh; Duroe, Kiersten and Singer, D. M. Influence of iron redox cycling on organo-mineral associations in Arctic tundra soils [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41D-0458, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Geochemical interactions between soil organic matter and minerals influence decomposition in many environments but remain poorly understood in arctic tundra systems. In tundra soils that are periodically to persistently saturated, the accumulation of iron oxyhydroxides and organo-iron precipitates at redox interfaces may inhibit decomposition by binding organic molecules and protecting them from microbial degradation. Here, we couple synchrotron-source spectroscopic techniques with chemical sequential extractions and physical density fractionations to evaluate the spatial distribution and speciation of Fe-bearing phases and associated organic matter in organic and mineral horizons of the seasonally thawed active layer in tundra soils from northern Alaska. Mineral-associated organic matter comprised 63 ± 9% of soil organic carbon stored in the active layer of ice wedge polygons. Ferrous iron produced in anoxic mineral horizons diffused upwards and precipitated as poorly-crystalline oxyhydroxides and organic-bound Fe(III) in the organic horizons. Ferrihydrite and goethite were present as coatings on mineral grains and plant debris and in aggregates with clays and particulate organic matter. Organic matter released through acid-dissolution of iron oxides may represent a small pool of readily-degradable organic molecules temporarily stabilized by sorption to iron oxyhydroxide surfaces, while larger quantities of particulate organic carbon and humic-like substances may be physically protected from decomposition by Fe-oxide coatings and aggregation. We conclude that formation of poorly-crystalline and crystalline iron oxides at redox interfaces contributes to mineral protection of organic matter through sorption, aggregation, and co-precipitation reactions. Further study of organo-mineral associations is necessary to determine the net impact of mineral-stabilization on carbon storage in rapidly warming arctic ecosystems.

2017070359 Heslop, J. K. (University of Alaska Fairbanks, Water and Environmental Research Center, Fairbanks, AK); Walter Anthony, K. M.; Grosse, G.; Anthony, P. and Bondurant, A. Temperature sensitivity of methanogenesis in a thermokarst lake sediment core [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41J-06, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Little is known about temperature sensitivity of permafrost organic carbon (OC) mineralization over time scales of years to centuries following thaw. Due to their formation and thaw histories, taliks (thaw bulbs) beneath thermokarst lakes provide a unique natural laboratory from which to examine how permafrost thawed in saturated anaerobic conditions responds to changes in temperature following long periods of time since thaw. We anaerobically incubated samples from a 590 cm thermokarst lake sediment core near Fairbanks, Alaska at four temperatures (0, 3, 10, and 25 °C) bracketing observed talik temperatures. We show that since initial thaw »400 yr BP CH₄ production shifts from being most sensitive to at lower (0-3 °C; Q_10-EC=1.15E7) temperatures to being most sensitive at higher (10-25 °C; Q_10-EC=67) temperatures. Frozen sediments collected from beneath the talik, thawed at the commencement of the incubation, had significant (p ≤&eq; 0.05) increases in CH₄ production rates at lower temperatures but did not show significant CH₄ production rate increases at higher temperatures (10-25 °C). We hypothesize the thawing of sediments removed a major barrier to C mineralization, leading to rapid initial permafrost C mineralization and preferential mineralization of the most biolabile OC compounds. In contrast, sediments which had been thawed beneath the lake for longer periods of time did not experience statistically significant increases in CH₄ production at lower temperatures (0-10 °C), but had high temperature sensitivities at higher temperatures (10-25 °C). We believe these rate increases are due to warmer temperatures in the experimental incubations crossing activation energy thresholds, allowing previously recalcitrant fractions of OC to be utilized, and/or the presence of different microbial communities adapted to thawed sediments. Recently-deposited sediments at shallow depths in the lake core experienced increases in CH₄ production across all incubation temperatures (Q_10-ST=4.4).

2017070366 Hutchings, J. (University of Florida, Department of Geological Sciences, Ft. Walton Beach, FL); Zhang, X.; Bianchi, Thomas S.; Schuur, E.; Arellano, Ana R. and Liu, Y. Effects of enhanced thaw depth on the composition of Arctic soil organic matter leachate [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-07, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Pan-Arctic permafrost is increasingly susceptible to thaw due to the disproportionally high rate of temperature change in high latitudes. These soils contain a globally significant quantity of organic carbon that, when thawed, interacts with the modern carbon cycle. Current research has focused on atmospheric carbon fluxes and transport by rivers and streams to continental shelves, but has overlooked the lateral flux of carbon within watershed soils, which is the primary link between terrestrial and riverine ecosystems. Understanding the effects of water movement through permafrost soils on dissolved organic carbon is critical to better modelling of lateral carbon fluxes and interpreting the resulting observed riverine carbon fluxes with applications to investigations of the past, present, and future of the pan-Arctic. We conducted a laboratory leaching experiment using active layer soils from the Eight Mile Lake region of interior Alaska. Cores were sampled into surface and deep sections. Surface sections were subjected to a three-stage leaching process using artificial rain, with cores stored frozen overnight between stages (which crudely simulated freeze-thaw mechanisms). Surface leachates were sampled for analysis and the remainder percolated through deep soils using the same three-staged approach. Measurements of surface and deep leachates were selected to characterize transport-related changes to dissolved organic matter and included dissolved organic carbon, fluorescent dissolved organic matter via excitation emission matrices, and molecular composition via Fourier transform ion cyclotron resonance mass spectrometry. Primary findings from the experiment include a net retention of 2.4 to 27% of dissolved organic carbon from surface leachates in deep soils, a net release of fluorescent dissolved organic matter from deep soils that was 43 to 106% greater than surface leachates, increased hydrophobicity during stage three of leaching, and the preferential leaching of lignin- and tannin-like formulas from deep soils, consistent with fluorescence measurements.

2017070360 Liebner, S. (Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany); Lehr, C.; Wagner, D.; Obu, Jaroslav; Lantuit, H. and Fritz, M. Potential methane production in thawing permafrost is constrained by methanogenic population size, carbon density, and substrate [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41J-07, 2 ref., December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The release of carbon from newly thawed permafrost is estimated to add between 0.05 and 0.39 °C to the simulated global mean surface air temperature by the year 2300. The release of the potent greenhouse gas CH₄ following permafrost thaw is thereby of particular concern. Models simulated a contribution of CH₄ to the radiative forcing from thawing permafrost of up to 40% for the maximum extent of thermokarst (1). Batch experiments on thawed permafrost samples, however, have rendered the contribution of anaerobically produced carbon and in particular of CH₄ to be surprisingly weak (2) and CH₄ production which is realized through methanogenic archaea was reported to be low and associated with long lag phases . This leads to the hypotheses that initial methanogenic population sizes and/or substrates are limiting factors in permafrost. The objective of this study is to identify constraints for CH₄ production in thawing permafrost. We analyzed several low Arctic permafrost cores of up to 3 m depth of different land cover types, sediment properties, age and stratigraphy for methanogenic abundance, potential methane production and predictors of both. We found that methanogenic population size and substrate pool are constraints on methane production but unlike expected, they do not fully explain low CH₄ production rates in thawing permafrost. Even when both, population size and substrate concentrations, were large, the potential production of CH₄ was still comparably low. Furthermore we show that the potential production of CH₄ in thawing permafrost is a function of the methanogenic population size if substrate is not the limiting factor and that the methanogenic population size in turn is a function of the carbon density. Based on our study we propose that on the long term after permafrost has thawed, growth and community shifts within the methanogenic population will occur which potentially will increase methane production by orders of magnitude. 1. Schneider von Deimling T, et al. (2015) Observation-based modelling of permafrost carbon fluxes with accounting for deep carbon deposits and thermokarst activity. Biogeosciences 12(11):3469-3488. 2. Schaedel C, et al. (2016) Potential carbon emissions dominated by carbon dioxide from thawed permafrost soils. Nature Clim. Change advance online publication.

2017070365 O'Donnell, J. A. (National Park Service Anchorage, Anchorage, AK); Aiken, George; Abbott, B. W.; Butler, K. D.; Ewing, S. A.; Olefeldt, D.; Spencer, R. G.; Striegl, R. G.; Vonk, J. and Wickland, K. Dissolved organic matter composition in waters draining permafrost landscapes; a circumpolar synthesis [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-06, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The flux of dissolved organic matter (DOM) from terrestrial to freshwater aquatic and marine ecosystems represents an important component of the carbon (C) balance in Arctic and sub-Arctic watersheds. Recent warming and permafrost thaw have altered DOM fluxes in rivers, both through the release of old permafrost C and by shifting hydrologic transport and cycling of DOM in soils. The fate of DOM along the soil-river-ocean continuum is closely linked to its chemical composition, which governs photochemical and microbially mediated transformations and therefore C-cycle feedbacks to the atmosphere. Given the complexity of these issues, large uncertainties exist with respect to DOM fate under future warming and permafrost thaw. To better constrain DOM turnover and fate, we synthesized DOM composition data from 48 published studies and additional unpublished data from across the northern circumpolar permafrost region. Our database includes over 4000 water samples spanning different regions (North America, Eurasia), permafrost zones (continuous, discontinuous), site types (soils, rivers, lakes, ocean), and disturbances (i.e., thermokarst activity). DOM was characterized using a broad range of analytical approaches, including bulk dissolved organic carbon (DOC) and nitrogen concentrations, optical properties, chemical fractionation, and C isotopes (d¹³C, D¹⁴C). Preliminary findings highlight broad spatial variation in DOM composition along the soil-to-ocean continuum, reflecting DOM processing as a function of transport time. DOC concentrations were highest in waters draining upland and peatland thermokarst features, but generally declined in larger downstream basins. While DOM age in ground ice and permafrost-thaw waters was old (> 10k y BP), DOM in streams and rivers was generally modern, likely reflecting the bio-lability and rapid turnover of permafrost C, as well as dilution of old DOM by young carbon inputs moving down the hydrologic network. We will present further analyses in the goal of identifying relationships between DOM composition and bio-lability across sites to generating robust decay functions for earth system modelers.

2017070285 Oktem, R. (Lawrence Berkeley National Laboratory, Berkeley, CA); Wainwright, Haruko M.; Curtis, J. B.; Dafflon, B.; Peterson, J.; Ulrich, C.; Hubbard, S. S. and Torn, M. S. Ground-based remote sensing for quantifying subsurface and surface co-variability to scale Arctic ecosystem functioning [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B33C-0617, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Predicting carbon cycling in Arctic requires quantifying tightly coupled surface and subsurface processes including permafrost, hydrology, vegetation and soil biogeochemistry. The challenge has been a lack of means to remotely sense key ecosystem properties in high resolution and over large areas. A particular challenge has been characterizing soil properties that are known to be highly heterogeneous. In this study, we exploit tightly-coupled above/belowground ecosystem functioning (e.g., the correlations among soil moisture, vegetation and carbon fluxes) to estimate subsurface and other key properties over large areas. To test this concept, we have installed a ground-based remote sensing platform - a track-mounted tram system - along a 70 m transect in the ice-wedge polygonal tundra near Barrow, Alaska. The tram carries a suite of near-surface remote sensing sensors, including sonic depth, thermal IR, NDVI and multispectral sensors. Joint analysis with multiple ground-based measurements (soil temperature, active layer soil moisture, and carbon fluxes) was performed to quantify correlations and the dynamics of above/belowground processes at unprecedented resolution, both temporally and spatially. We analyzed the datasets with particular focus on correlating key subsurface and ecosystem properties with surface properties that can be measured by satellite/airborne remote sensing over a large area. Our results provided several new insights about system behavior and also opens the door for new characterization approaches. We documented that: (1) soil temperature (at >5 cm depth; critical for permafrost thaw) was decoupled from soil surface temperature and was influenced strongly by soil moisture, (2) NDVI and greenness index were highly correlated with both soil moisture and gross primary productivity (based on chamber flux data), and (3) surface deformation (which can be measured by InSAR) was a good proxy for thaw depth dynamics at non-inundated locations.

2017070363 Palmtag, J. (Stockholm University, Stockholm, Sweden); Hugelius, G. and Kuhry, P. High resolution landscape-level assessments of soil organic carbon storage in permafrost soils of NE Greenland and northern Russia [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B42D-04, 4 ref., December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Recent studies have shown that permafrost soils in the northern circumpolar region store almost twice the size of the entire atmospheric carbon pool (Hugelius et al., 2014). The observed permafrost warming and degradation could intensify the microbial activity and decomposition of organic matter releasing even more greenhouse gases into the atmosphere (Schuur et al., 2015). Soil organic carbon (SOC) pools have large regional and landscape-level variability and best possible SOC estimates are crucial for better understanding the impact of the permafrost-carbon feedback on global warming. This study provides high-resolution land cover and landform classification data on total SOC storage (Palmtag et al., 2015; 2016) from five under-sampled regions of continuous permafrost, contrasting mountainous (Zackenberg, NE Greenland) and lowland (NE Siberia, Russia; Taymyr Peninsula, Russia) settings. The emphasis throughout the sites was put on SOC partitioning within the landscape and soil horizon levels as well as on soil forming processes under periglacial conditions. Our data suggest that different processes govern SOC burial and preservation in mountain and lowland soils. The estimated mean SOC storage is varying between 5 kg in NE Greenland to 30 kg C m^-2 in NE Siberia for the top meter of soil with only negligible amount of total ecosystem carbon being stored phytomass (Taymyr Peninsula). Observed large regional and landscape-level SOC differences, mainly controlled by topographic, ecoclimatic, geomorphologic and edaphic factors, emphasize the importance of detailed field studies for improving the landscape level C inventories. Hugelius, G. et al. Estimated stocks of circumpolar permafrost carbon with quantified uncertainty ranges and identified data gaps. Biogeosciences, 11, 6573-6593, 2014. Palmtag, J. et al. Storage, landscape distribution and burial history of soil organic matter in contrasting areas of continuous permafrost. Arctic, Antarctic, and Alpine Research, 47(1), 71-88,2015. Palmtag, J. et al. Controls on the storage of organic carbon in permafrost soils in northern Siberia. European Journal of Soil Science, 67, 478-491, 2016. Schuur, E.A.G. et al. Climate change and the permafrost carbon feedback. Nature, 20, 171-179, 2015.

2017070346 Schaedel, Christina (Northern Arizona University, Center for Ecosystem Science and Society, Flagstaff, AZ); Ernakovich, J. G.; Harden, J. W.; Natali, S.; Richter, A.; Schuur, E. and Treat, C. C. Strategizing a comprehensive laboratory protocol to determine the decomposability of soil organic matter in permafrost [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41D-0464, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Soil organic matter decomposition depends on physical, chemical, and biological factors, such as the amount and quality of the organic matter stored, abiotic conditions (such as soil temperature and moisture), microbial community dynamics, and physical protection by soil minerals. Soils store immense amounts of carbon with 1330-1580 Pg of carbon in the permafrost region alone. Increasing temperatures in the Arctic will thaw large amounts of previously frozen organic carbon making it available for decomposition. The rate at which carbon is being released from permafrost soils is crucial for understanding future changes in permafrost carbon storage and carbon flux to the atmosphere. The potential magnitude and form of carbon release (carbon dioxide or methane) from permafrost can be investigated using soil incubation studies. Over the past 20 years, many incubation studies have been published with soils from the permafrost zone and multiple recent syntheses have summarized current findings from aerobic and anaerobic incubation studies. However, the breadth of the synthesis projects was hampered by incomplete meta-data and the use of different methods. Here, we provide recommendations to improve and standardize future soil incubation studies (which are not limited to permafrost soils) to make individual studies useful for inclusion in syntheses and meta-analyses, which helps to broaden their impact and our understanding of organic matter cycling. Additionally, we identify gaps in the understanding of permafrost carbon decomposability, that, when coupled with emerging knowledge from field observations and experiments, can be incorporated into future studies to gain a better overview of the overall decomposability of permafrost carbon.

2017070289 Schuster, P. F. (U. S. Geological Survey, Denver, CO). The potential release of mercury currently stored in permafrost [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B33D-0632, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Changing climate in northern regions is causing permafrost to thaw with major implications for the cycling of carbon, nutrients, and heavy metals, particularly mercury (Hg) in arctic and subarctic ecosystems. Permafrost occurs in nearly one quarter of the Earth's northern land mass and an estimated 13 percent of Earth's entire land surface. Large-scale permafrost thaw will release Hg currently stored in permafrost, impacting aquatic resources and posing a serious threat to human health. We measured total sediment Hg concentration in 543 samples from 13 permafrost cores from the Alaskan interior and the North Slope. We assume this Hg is atmospherically deposited natural Hg (not of anthropogenic origin) over millennia since at least the last ice age. We estimate the median mass of stored Hg in northern hemisphere permafrost to be 790+/-267 Kilotons, potentially the second largest mercury pool on the planet. Projections indicate substantial permafrost thawing leading to peak annual Hg releases exceeding current total annual anthropogenic emissions of mercury, with major implications for terrestrial and aquatic life, the world's fisheries, and ultimately human health.

2017070322 Shakil, Sarah (University of Alberta, Edmonton, AB, Canada); Tank, S. E. and Kokelj, S. Mobilization and degradation of particulate organic carbon from retrogressive thaw slumps in the western Canadian Arctic [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0429, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Rapid arctic climate warming has contributed to a significant intensification in the rate and occurrence of thermokarst features which can cause large quantities of frozen organic carbon to suddenly become an active part of the contemporary carbon cycle. Mobilized organic carbon becomes susceptible to bacterial decomposition to CO₂, which can then act as a significant positive feedback to climate change. Increasingly, studies are showing dissolved organic carbon (DOC) released from thawing permafrost is highly biodegradable, however, we know little about the biodegradability of permafrost-derived particulate organic carbon (POC). On the Peel Plateau, NWT, Canada, where a warming and wetting climate has intensified the activity of massive retrogressive thaw slumps (RTS), and where some of the Arctic's largest RTS features occur, POC can be more than an order of magnitude greater in streams impacted by an RTS feature when compared to upstream, unimpacted locations, and this mobilization causes POC concentrations to be more than 200 times greater than DOC downstream of slumps. Furthermore, POC released from RTS features can be 6,000 to 13,000 years older than POC in unimpacted streams, indicating a significant mobilization of permafrost carbon in the particulate form. To determine the biodegradability of RTS-released POC in this region, incubations using water samples collected upstream, at, and downstream of RTS sites were conducted during the summer of 2015. Dissolved oxygen measurements were taken 1-2 times per day, and samples for POC and DOC concentration, SUVA254, and bacterial abundance were collected at 0 days, 7 days, and 11 days. Treatments containing a spike of RTS-runoff in filtered water declined in oxygen at a rate as much as 10 times greater than treatments containing filtered DOC controls and unfiltered upstream water indicating that the released of RTS-derived POC substantially increases carbon mineralization in impacted streams. This pool of organic carbon could therefore substantially contribute to the transfer of organic carbon from permafrost soils to the atmospheric carbon pool. Ongoing work is examining the balance between POC decomposition during downstream transport and re-sequestration into streambed sediments.

2017070319 Shatilla, N. J. (McMaster University, Hamilton, ON, Canada) and Carey, S. K. Dissolved organic carbon sources and pathways in a subarctic, alpine watershed underlain by discontinuous permafrost, Yukon, Canada [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0426, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

The origin, timing and movement of organic carbon from terrestrial to aquatic systems are poorly characterized in subarctic alpine environments with variable frozen ground conditions. Increases in temperature, growing seasonal duration, changes in precipitation regimes, vegetation composition and active layer deepening from climate warming will result in new sources and altered pathways of dissolved organic carbon (DOC) transport. The objective of this research is to provide new insight into how DOC sources evolve throughout the year in a permafrost-underlain alpine catchment using fluorescing dissolved organic matter and DOC dataset. Wolf Creek Research Basin (»178 km²) is located at the southern boundary of the discontinuous permafrost zone in Yukon Territory, Canada. Samples were collected at differing frequencies from two high elevation headwater streams (GC, BB) and a headwater lake (CL) from 19 April 2015 to 22 August 2016. Additional samples from riparian zones, wetland complexes (W1, W2) and the catchment outlet (WC) were used in conjunction with the headwater hydrochemical data to characterize event and seasonal differences in concentration and partitioning between microbially-derived and terrestrial organic carbon. DOC concentrations in both headwater streams changed in response to episodic water inputs from snowmelt, precipitation events and groundwater inputs. Results from 2015 indicate that greater DOC fluxes correspond with increasing discharge during freshet at both headwaters (GC, BB) with DOC concentrations at GC increasing from a winter minimum of »0.7 mg/L to a maximum value of 9.8 mg/L in mid-May before declining to concentrations ranging from 1.0 to 1.6 mg/L during summer. Specific UV absorbance (SUVA) and other common optical indices were used to characterize the quality of DOC in surface waters, and excitation emission matrices (EEMs) were used in a parallel factor analysis (PARAFRAC) to quantify temporal patterns of underlying DOC components. Time series analysis of this output was used to address knowledge gaps in organic carbon dynamics of alpine systems. This research will aid in the assessment of how permafrost thaw in complex alpine systems, which are poorly characterized despite their widespread occurrence, influences stream DOC at the headwater and landscape scale.

2017070329 Spencer, R. (Florida State University, Tallahassee, FL); Carey, J. and Tang, J. Permafrost thaw and vegetation cover change may alter silicon exports to Arctic coastal receiving waters [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0439, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Silicon (Si) availability in Arctic coastal waters is a critical factor dictating phytoplankton species composition, as diatoms require as much Si as nitrogen (N) on a molar basis to survive. Riverine exports are the main source of Si to Arctic coastal waters annually and thus, the timing and magnitude of river Si fluxes have direct implications for marine ecology and global carbon dynamics. Although geochemical factors exert large controls on Si exports to marine waters, watershed land cover has recently been shown to alter the retention and transport of Si along the land-ocean continuum in lower latitudes, due in large part to the ability of terrestrial vegetation to store large quantities of Si in its tissue. However, it is unclear how shifts in basin land cover and climatic warming will alter Si exports in the Arctic, as increasing shrubiness and northward migration of treeline may increase Si retention on land, but permafrost thaw and elevated weathering rates may stimulate Si exports towards coastal waters. In this study we investigate how permafrost thaw and vegetation cover shifts are altering Arctic riverine Si export using the geochemical signatures of ten rivers draining a 700 km north-south gradient across the Yukon and Arctic North Slope basins in Alaska. Across the 2016 spring freshet, average dissolved Si (DSi) concentrations across sites ranged from 22 to 115 mM, with a significant negative relationship observed between average DSi concentration and latitude (r=-0.95, p<0.05). Conversely, average biogenic Si (BSi) concentrations showed no trends with latitude and were more uniform across the permafrost-vegetation cover gradient, ranging from 8 to 15 mM BSi. Si yields followed a similar pattern as concentrations across the gradient. We use data on basin lithology and land cover, instantaneous discharge, and the concentrations of inorganic nutrients (N, phosphorous), chlorophyll a, total suspended solids (TSS), and Ge (Germanium)/Si ratios, to determine the drivers of these patterns in Si behavior. In turn, our results will be used to create the first predictive framework to assess how future warming will alter fluvial Si exports to Arctic receiving waters.

2017070324 Spencer, R. G. (Florida State University, Department of Earth, Ocean and Atmospheric Sciences, Tallahassee, FL); Drake, T.; Guillemette, François; Chanton, J.; Podgorski, D. C. and Zimov, N. The ephemeral signature of permafrost carbon in an Arctic fluvial network [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0432, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Arctic fluvial networks process, outgas, and transport significant quantities of terrestrial organic carbon (OC). The contribution from permafrost thaw, however, remains uncertain. A primary obstacle to quantifying the contribution of permafrost OC is its high biodegradability, since it is lost to microbial respiration soon after thaw. In this study, we investigate the by-product of respiration (dissolved inorganic carbon; DIC) at maximum late-summer thaw in sites spanning the fluvial network in order to assess whether the microbial consumption of permafrost imparts a persisting aged (¹⁴C-depleted) signature on the DIC pool. Using keeling-curve incubations, we show that water column bacteria respire different sources of dissolved OC (DOC) downstream. Evidence of permafrost respiration (production of aged DIC) was only present in permafrost-influenced sites. In the non-permafrost sites, ambient DIC was modern, which does not preclude respiration of permafrost OC upstream since depleted ¹⁴C in DIC can be easily overwhelmed by modern (¹⁴C-enriched) DIC. DOC compositional analysis via FT-ICR-MS showed that aliphatic and nitrogen containing compounds were associated with the production of aged DIC, which provides insight as to why permafrost OC is likely rapidly respired upon thaw. Overall, the results from this study demonstrate the complications of using ¹⁴C-DIC as a geochemical tracer for permafrost. We highlight the need for novel and unique conservative geochemical tracers to quantify the release and fate of permafrost OC in fluvial systems.

2017070326 St. Pierre, Kyra (University of Alberta, Edmonton, AB, Canada); St. Louis, Vincent L.; Schiff, S. L.; Aukes, P.; Dainard, Paul and Lehnherr, Igor. Dissolved inorganic carbon dynamics in a High Arctic glacial watershed [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0436, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

In the Canadian Arctic Archipelago, glacial mass loss has accelerated dramatically since the start of the 2000s. While the characterization of the sub-glacial drainage system and its meltwaters have received considerable attention, we know yet little about the quality of these meltwaters as they exit the glacier and flow into receiving freshwater ecosystems. Due to high rates of coupled physical and chemical weathering of geological material, glacial meltwaters could have important consequences for dissolved inorganic carbon (DIC) chemistry in freshwater systems, particularly in determining whether these ultra-oligotrophic freshwaters are sources or sinks of carbon dioxide (CO₂). Efforts to quantify CO₂ fluxes in the High Arctic at the watershed scale have largely focused on the terrestrial environment, so far leaving the role of large glacier-fed lake ecosystems unresolved. At 540 km² and 267 m deep, Lake Hazen on northern Ellesmere Island (81°N, 71°W) is the world's largest high arctic lake by volume. Its 7400-km² watershed is just over a third glaciated and is underlain by permafrost. Since 2005, glacial run-off into the lake has increased 10 fold, as have sedimentation rates. Our objectives were three-fold: 1) to assess temporal variability in pCO₂ dynamics during the melt season in glacial rivers; 2) to assess spatial variability in pCO₂ in different rivers throughout the watershed; and, 3) to determine the impact of glacial meltwaters on Lake Hazen as a source or sink of CO₂ to the atmosphere. During summers 2015 and 2016, we completed detailed DIC, pCO₂ and chemical surveys of 7 glacial rivers in the Lake Hazen watershed. From 2013-2016, we also completed DIC, pCO₂ and chemical depth profiles in Lake Hazen itself. Spring under ice profiles of the lake indicate the build-up of CO₂ and depletion of O₂ at depth, suggesting respiration of organic matter at the bottom of the lake over winter. However, dense, turbid glacial rivers form underflow currents upon entering Lake Hazen, transporting waters undersaturated in CO₂ to the bottom of the lake. Detailed results of spring and summer water column surveys, along with results from bottle incubation experiments to determine CO₂ drawdown rates due to glacial inputs to Lake Hazen, will be presented.

2017070357 Sweeney, Colm (NOAA Boulder, Earth System Research Laboratory, Boulder, CO); Commane, R.; Wofsy, S.; Dlugokencky, E. J.; Karion, A.; Stone, R. S.; Chang, Rachel; Tans, P. P. and Wolter, Sonja. Decadal changes in CH4 and CO2 emissions on the Alaskan North Slope [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41J-02, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Large changes in surface air temperature, sea ice cover and permafrost in the Arctic Boreal Ecosystems (ABE) are significantly impacting the critical ecosystem services and human societies that are dependent on the ABE. In order to predict the outcome of continued change in the climate system of the ABE, it is necessary to look at how past changes in climate have affected the ABE. We look at 30 years of CH₄ and 42 years of CO₂ observations from the NOAA Global Greenhouse Gas Reference Network site in Barrow, Alaska. By eliminating background trends and only looking at data collected when winds are blowing off the North Slope we find very little change in CH₄ enhancements, but significant changes in the CO₂ enhancements coming off the tundra. The bulk of both CO₂ and CH₄ emissions appear to be emitted well after the first snow fall on the North Slope. CO₂ emissions are a strongly correlation with summer surface temperatures, while CH₄ emissions appear insensitive to the large temperature changes that occurred over the measurement period. These results suggest that CO₂, and not CH₄ emissions, are a likely pathway for the degradation of permafrost carbon.

2017070328 Toohey, R. (U. S. Geological Survey, Anchorage, AK); Herman-Mercer, N. M.; Schuster, P. F.; Mutter, E. A. and Koch, J. C. Long-term increases in Yukon River water chemistry as indicators of changing flowpaths, groundwater, and permafrost [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0438, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Alaska has experienced a warming climate over the last century that has altered air temperature, precipitation, and permafrost. The Yukon River Basin (YRB), underlain primarily by discontinuous permafrost, experiences many of these changes. Water chemistry is strongly correlated with different flowpaths governed by active layer dynamics throughout the YRB. Previous research within the YRB suggests long term decreases in dissolved organic carbon (DOC) and increasing groundwater contribution as the result of changing flowpaths and permafrost degradation. In the YRB, additional biogeochemical parameters (major ions, nutrients) have greater historical data availability that is expected to exhibit the inverse of DOC with increasing trends as the active layer expands. Combining data collected by the US Geological Survey and the Yukon River Inter-Tribal Watershed Council, we were able to analyze a rare water chemistry and discharge database of 32 years from the Yukon River and one of its major tributaries, the Tanana River. Non-parametric trend analysis indicates significant increases of Ca, Mg, and Na flux in both rivers over the data record. Additionally, SO₄ and P annual flux also increased over this time period in the Yukon River. Increasing trends throughout the open water season for Ca, Mg, P and SO₄ monthly flux suggests increased exposure to mineral soils and weathering has significantly increased. Perhaps most importantly, groundwater chemistry has experienced statistically significantly changes with increases in monthly flux of Ca, Mg, P and SO₄ over the last three decades. Changing hydrology and geochemistry of the YRB may have important implications for the carbon cycle, aquatic ecosystems, and contaminant transport.

2017070330 Zolkos, Scott (University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada); Tank, S. E. and Kokelj, S. V. The carbon cycle implications of chemical weathering in retrogressive thaw slump-impacted streams [abstr.]: in AGU 2016 fall meeting, American Geophysical Union Fall Meeting, 2016, Abstract B41C-0441, December 2016. Meeting: American Geophysical Union 2016 fall meeting, Dec. 12-16, 2016, San Francisco, CA.

Permafrost thaw is "unlocking" and exposing significant amounts of sediment, solutes and organic carbon previously maintained in frozen soils to biochemical processing and fluvial transport. While microbial respiration of permafrost organic carbon contributes significantly to CO₂ in Arctic headwater streams, chemical weathering of minerals unearthed by thawing permafrost may fix CO₂ as bicarbonate (HCO₃), thus removing it from the active carbon cycle. However, the degree to which mineral weathering acts to temper CO₂ generated during permafrost thaw is largely unknown. During summer 2015, we investigated these dynamics in eight streams (orders »1-3) impacted by retrogressive thaw slumps across the Peel Plateau (NT, Canada), where thaw slumps expose permafrost that is comprised of abundant glacial tills, and glaciofluvial and glaciolacustrine sediments. Thaw slump activity had a discernible signature in all streams: conductivity, pH, dissolved inorgnaic carbon (DIC), and solute concentrations (Ca, Mg, Na, K, SO₄, Cl) increased in the downstream (thaw slump-impacted) reach, relative to upstream, while CO₂ decreased. This corresponded with an isotopically-enriched DIC pool in impacted streams (mean d¹³C_DIC = -9.80 ppm), perhaps indicating the dissolution of carbonate minerals following exposure by thaw slump activity. Despite a general decrease downstream of thaw slumps, CO₂ remained supersaturated in impacted streams (mean pCO₂ = 915 matm). However, the highest partial pressures of CO₂ were found in thaw slump runoff (mean pCO₂ = »4,600 matm), above the point where runoff entered downstream systems. High pCO₂ levels in slump runoff may be derived from microbial respiration of slump-released dissolved organic carbon or, for some slumps, carbonate dissolution (range d¹³C_DIC = 0.67 - -23.37 ppm). While this work suggests thaw slumps in the Western Canadian Arctic may act to partially temper CO₂ in headwater streams, these stream networks will likely persist as significant sources of CO₂ to the atmosphere.

2017070735 Zhang, Xiaowen (University of Florida, Department of Geological Sciences, Fort Walton Beach, FL); Bianchi, Thomas S. and Schuur, Edward. Alteration of chemical composition of soil-leached dissolved organic matter under cryogenic cycles [abstr.]: in 2016 ocean sciences meeting, Ocean Sciences Meeting, 2016, Abstract CT54A-0259, February 2016. Meeting: 2016 ocean sciences meeting, Feb. 21-26, 2016, New Orleans, LA.

Arctic permafrost thawing has drawn great attention because of the large amount of organic carbon (OC) storage in Arctic soils that are susceptible to increasing global temperatures. Due to microbial activities, some of the OC pool is converted in part to greenhouse gases, like CH₄ and CO₂ gas, which can result in a positive feedback on global warming. In Artic soils, a portion of OC can be mobilized by precipitation, drainage, and groundwater circulation which can in some cases be transported to rivers and eventually the coastal margins. To determine some of the mechanisms associated with the mobilization of OC from soils to aquatic ecosystems, we conducted a series of laboratory soil leaching experiments. Surface soil samples collected from Healy, Alaska were eluted with artificial rain at a constant rate. Leachates were collected over time and analyzed for dissolved organic carbon (DOC) concentrations. Concentrations began from 387-705 mg/L and then dropped to asymptote states to 25-219 mg/L. High-resolution spectroscopy was used to characterize colored dissolved organic matter (CDOM) and CDOM fluorescence intensity also dropped with time. Fluorescence maximum intensity (F_max) for peak C ranged from 0.7-4.2 RU, with Ex_max/Em_max = 310/450 nm. F_max for peak T ranged from 0.5-3.2 RU, with Ex_max/Em_max = 275/325 nm. Peak C: peak T values indicated preferential leaching of humic-like components over protein-like components. After reaching asymptotic levels, samples were stored frozen and then thawed to study the cryogenic impact on OC composition. CDOM intensity and DOC concentration increased after the freeze-thaw cycle. It was likely that cryogenic processes promoted the breakdown of OC and the releases of more DOC from soils. PARAFAC of CDOM excitation and emission matrices (EEMs) will be used to analyze CDOM composition of the soil leachates.

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2017074242 Fish, C. S. (Geological Survey of Canada, Ottawa, ON, Canada); Morse, P. D. and Wolfe, S. A. Icings in the Lac la Martre area (1984-2015), Northwest Territories, mapped from Landsat imagery: Open-File Report - Geological Survey of Canada, Rep. No. 8124, 43 p., illus. incl. tables, sketch maps, 29 ref., 2017.

Icings are sheet-like masses of layered ice that form over the winter by freezing of successive flows of water on the ground surface or on top of river or lake ice. Icings can negatively impact the performance of seasonal and all-season roads and are a transportation risk in Arctic regions. Therefore, maps of their occurrence and reoccurrence provide important geoscience information required for development and transportation infrastructure planning. In this study, a set of icing maps was derived using threshold values of band ratios from a time series of Landsat images (1984-2015), located within the Bear and Interior Platform Geological Provinces in the Lac la Martre area, NWT (WRS-2 Path 49/Row 16). The icings maps were generated using images acquired in late spring when the region is largely snow-free, but ice bodies remain. A water mask created from summer images was used to differentiate between different types of frozen water bodies (rivers, lakes, icings), so any remaining ice was considered to be icings. Icing reoccurrence maps were generated by overlaying successive icing distribution maps in a Geographic Information System. This Open File contains the digital, georeferenced icing data.

DOI: 10.4095/299737

2017074241 Galloway, Jennifer (Geological Survey of Canada, Canada). Geoscience tools for supporting environmental assessment of metal mining: in Public presentations, Environmental Geoscience Program (EGP); current status of research projects (Jacob, N.; et al.), Scientific Presentation - Geological Survey of Canada, Rep. No. 49, p. 93-114, illus., 2017. PowerPoint presentation; presented at the Environmental Geoscience Program meeting, Quebec City, QC, May 10-11, 2016.

The goal of this activity is to test the hypothesis that climate variability controls metal(loid) cycling in the environment. We initiated research in 2015-16 to provide missing baseline geochemical data and model the cumulative impacts of geogenic and anthropogenic processes, with a focus on climate variability, on the transport and fate of metal(loids) in the vicinity of the City of Yellowknife, Northwest Territories. Due to the complex geology of the Slave Geological Province and in particular, mineralized greenstone belts and hydrothermal alteration zones, geochemical background can be highly variable even on small spatial scales. In addition, the Yellowknife region has experienced 75 years of gold ore mining and processing that resulted in release of substantial quantities of arsenic to the surrounding environment. The larger POLAR Knowledge Canada S&T funded activity will also focus on the Courageous Lake area that is thought to have been impacted by free-milling gold mining and processing at Tundra, Salmita, and Bulldog mines in the 1960s and 1980s, and the yet to be developed Hope Bay area (TMAC Resources Ltd.) in the central and northern Slave Geological Province, respectively.

DOI: 10.4095/299736

2017074287 Wolfe, S. A. (Geological Survey of Canada, Ottawa, ON, Canada); Morse, P. D.; Fraser, R.; Kerr, D. E.; Van der Sanden, J. J.; Short, N. H. and Zhang, Y. Climate change geoscience in sub-Arctic Canada; information pages: Popular Geoscience - Geological Survey of Canada, Rep. No. 99, 16 p. (French sum.), illus. incl. sketch maps, 20 ref., 2017. ISBN: 978-0-660-07985-1. Also available in French.

Air temperatures in northern Canada are rising at a rate of three to four times that of the global average. This warming, and its consequences on the environment and people of the North, is of significant concern. This is particularly true for sub-Arctic Canada, which is located within a sensitive boundary between seasonally and perennially frozen ground (known as permafrost). Natural Resources Canada addresses priority geoscience issues important to Canadians. The Climate Change Geoscience Program, in partnership with other agencies, applies knowledge, techniques, and innovations to issues of climate change impacts and adaptations. This series of information pages describes the application of our geoscience expertise and its impact on addressing climate change and adaptation in sub-Arctic Canada. These pages cover the issues of surficial geology, permafrost distribution and change, ground temperatures, ice-rich terrain and thermokarst, winter roads, and change detection. A list of publications pertinent to the research activities presented in the information pages is provided at the end of this document.

DOI: 10.4095/299883

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