14038896 Strauss, Jens (Alfred Wegener Institute, Potsdam, Germany); Schirrmeister, Lutz; Grosse, Guido; Wetterich, Sebastian; Ulrich, Mathias; Herzschuh, Ulrike and Hubberten, Hans-Wolfgang. The deep permafrost carbon pool of the Yedoma region in Siberia and Alaska: Geophysical Research Letters, 40(23), p. 6165-6170, illus. incl. sketch map, 45 ref., December 16, 2013.
Estimates for circumpolar permafrost organic carbon (OC) storage suggest that this pool contains twice the amount of current atmospheric carbon. The Yedoma region sequestered substantial quantities of OC and is unique because its deep OC, which was incorporated into permafrost during ice age conditions. Rapid inclusion of labile organic matter into permafrost halted decomposition and resulted in a deep long-term sink. We show that the deep frozen OC in the Yedoma region consists of two distinct major subreservoirs: Yedoma deposits (late Pleistocene ice- and organic-rich silty sediments) and deposits formed in thaw-lake basins (generalized as thermokarst deposits). We quantified the OC pool based on field data and extrapolation using geospatial data sets to 83 + 61/-57 Gt for Yedoma deposits and to 128 + 99/-96 Gt for thermokarst deposits. The total Yedoma region 211 + 160/-153 Gt is a substantial amount of thaw-vulnerable OC that must be accounted for in global models. Abstract Copyright (2013), . The Authors. Geophysical Research Letters published by Wiley on behalf of the American Geophysical Union.
14046079 Xie, S. (Chinese Academy of Sciences, Cold and Arid Regions Environmental and Engineering Research Institute, Laboratory of Desert and Desertification, Lanzhou, China); Qu, J.; Zu, R.; Zhang, K.; Han, Q. and Niu, Q. Effect of sandy sediments produced by the mechanical control of sand deposition on the thermal regime of underlying permafrost along the Qinghai-Tibet Railway: Land Degradation & Development, 24(5), p. 453-462, illus. incl. strat. col., 1 table, sketch map, 28 ref., September 2013.
To date, the mechanical control of drifting sand is the main method used for the protection of the Qinghai-Tibet Railway from damage. The thermal effect of sandy sediments which are held in place on the underlying permafrost is a key area of interest and the focus of this paper. A ground temperature investigation of the permafrost along the railway route was undertaken and results were related to the different mechanical control measures used to control moving sand which had resulted in varying sandy sediment thicknesses. The studies were conducted in the Hongliang River area of the Qinghai-Tibet Plateau from June 2010 to September 2010 using thermistor sensors. The results showed that the permafrost ground temperature and its daily variation, as well as the thawing depth of the active layer, decreased after the setting-up of sand movement controls which had resulted in the accumulation of thick sandy sediments within the outside fringe of sand-control engineering, or a covering of thin sandy sediments within the inside trackside (fringe) of sand-control engineering. Below the thick sandy sediment cover accumulated by sand-blocking fences, the average maximum temperature decreased. Average temperature decreased and the average depth of seasonal thawing (average thinning) were 3·38°C, 0·54°C and 0·48 m, respectively. Below the thin sand sediment cover accumulated by the checkerboard sand barriers, the values for the same parameters were 1·02°C, 0·21°C and 0·5 m, respectively. This study found that the mechanical control of sand does not only protect the railway from obstruction, but also facilitates permafrost stability, which in turn can help promote safety in railway operations. Abstract Copyright (2010), John Wiley & Sons, Ltd.
14044861 Arzhanov, M. M. (Rossiyskaya Akademiya Nauk, Institut Fiziki Atmosfery im. A. Obukhova, Moscow, Russian Federation) and Yeliseyev, A. V. Vliyaniye klimaticheskikh izmeneniy nad sushey vnetropicheskikh shirot na dinamiku mnogoletnemerzlykh gruntov pri stsenariyakh RCP v XXI v. po raschetam global'noy klimaticheskoy modeli IFA RAN [Influence of climate change at high latitudes on permafrost dynamics in the 21st century according to RCP scenarios and numerical analysis based on the global climate model developed at the Institute of Atmosphere Physics, Russian Academy of Sciences]: Meteorologiya i Gidrologiya, 2013(7), p. 31-42 (English sum.), illus., 51 ref., 2013.
The estimates of possible climate changes and cryolitozone dynamics in the 21st century over the Northern Hemisphere land are obtained using the IAP RAS global climate model forced by the RCP (Representative Concentration Pathways) scenarios. Annual mean warming over the northern extratropical land during the 21st century amounts to 1.2-5.3°C depending on the scenario. The snow cover area in February amounting currently to 46 million km2 decreases to 33-42 million km2 in the late 21st century. According to model estimates, the near-surface permafrost in the late 21st century persists in northern West Siberia, in Transbaikalia and Tibet even under the most aggressive RCP 8.5 scenario; under more moderate RCP 6.0, RCP 4.5, and RCP 2.6 scenarios, it remains in East Siberia and in some high-latitude regions of North America. The total near-surface permafrost area in the Northern Hemisphere in the current century decreases by 5.3-12.8 million km2 depending on the scenario. The soil subsidence due to permafrost thawing in Central Siberia, Transbaikalia, and North America can reach 0,5-0,8 m.
14040622 Mottaghy, D. (Geophysica Beratungsgesellschaft mbH, Aachen, Germany); Schwamborn, G. and Rath, V. Past climate changes and permafrost depth at the Lake El'gygytgyn site; implications from data and thermal modeling: Climate of the Past, 9(1), p. 119-133, illus. incl. 6 tables, sects., 57 ref., 2013. Includes appendices; part of special issue no. 48, Initial results from Lake El'gygytgyn, western Beringia; first time-continuous Pliocene-Pleistocene terrestrial record from the Arctic, edited by Brigham-Grette, J., et al., URL: http://www.clim-past.net/special_issue48.html; published in Climate of the Past Discussion: 16 July 2012, URL: http://www.clim-past-discuss.net/8/2607/2012/cpd-8-2607-2012.html; accessed in Apr., 2013.
This study focuses on the temperature field observed in boreholes drilled as part of interdisciplinary scientific campaign targeting the El'gygytgyn Crater Lake in NE Russia. Temperature data are available from two sites: the lake borehole 5011-1 located near the center of the lake reaching 400 m depth, and the land borehole 5011-3 at the rim of the lake, with a depth of 140 m. Constraints on permafrost depth and past climate changes are derived from numerical simulation of the thermal regime associated with the lake-related talik structure. The thermal properties of the subsurface needed for these simulations are based on laboratory measurements of representative cores from the quaternary sediments and the underlying impact-affected rock, complemented by further information from geophysical logs and data from published literature. The temperature observations in the lake borehole 5011-1 are dominated by thermal perturbations related to the drilling process, and thus only give reliable values for the lowermost value in the borehole. Undisturbed temperature data recorded over more than two years are available in the 140 m deep land-based borehole 5011-3. The analysis of these observations allows determination of not only the recent mean annual ground surface temperature, but also the ground surface temperature history, though with large uncertainties. Although the depth of this borehole is by far too insufficient for a complete reconstruction of past temperatures back to the Last Glacial Maximum, it still affects the thermal regime, and thus permafrost depth. This effect is constrained by numerical modeling: assuming that the lake borehole observations are hardly influenced by the past changes in surface air temperature, an estimate of steady-state conditions is possible, leading to a meaningful value of 14 ± 5 K for the post-glacial warming. The strong curvature of the temperature data in shallower depths around 60 m can be explained by a comparatively large amplitude of the Little Ice Age (up to 4 K), with low temperatures prevailing far into the 20th century. Other mechanisms, like varying porosity, may also have an influence on the temperature profile, however, our modeling studies imply a major contribution from recent climate changes.
14042165 Sun Zhongjun (Institute of Geophysical & Geochemical Exploration, Langfang, China); Yang Zhibin; Mei Hai; Qin Aihua; Zhang Fugui; Zhou Yalong; Zhang Shunyao and Mei Bowen. Geochemical characteristics of the shallow soil above the Muli gas hydrate reservoir in the permafrost region of the Qilian Mountains, China: in Exploring China; environment and resources (Cheng Hangxin, editor; et al.), Journal of Geochemical Exploration, 139, p. 160-169, illus. incl. 2 tables, geol. sketch map, 38 ref., April 2014.
In this study, the Muli gas hydrate reservoir in the Qilian Mountains was chosen as a test area for the geochemical exploration of gas hydrates in mid-latitude regions. Soil headspace gases, acid-extracted hydrocarbons and stable carbon isotopes of methane, and soil magnetic susceptibility as well as microbes were tested. The results show that the distribution of geochemical anomalies can be well correlated with the underlying gas hydrate reservoir. Acid-extracted hydrocarbons, soil headspace gases, and the stable carbon isotopes of methane can be considered as major indicators for geochemical exploration of gas hydrates, whereas magnetic susceptibility and microbes served as complementary indicators. The stable carbon isotopes of methane and the hydrocarbon composition of the surface geochemical anomalies indicated a thermogenic origin, which shows that the gas source of the potential gas hydrate reservoir in this area may be contributed by deep oil and coal-formed gases. An accumulation model for the gas hydrate reservoirs was also developed and an integrated exploration project for gas hydrate, oil and coal bed methane is also proposed for the Muli area. Abstract Copyright (2014) Elsevier, B.V.
14038020 Mari, Stefano; Scapozza, Cristian; Delaloye, Reynald and Lambiel, Christophe. Il permafrost nelle Alpi Ticinesi (2006-2011); rapportio no. 1 del Gruppo Permafrost Ticino [Permafrost in the Ticino Alps (2006-2011); report no. 1 of the Ticino Permafrost Group]: Bollettino della Società Ticinese di Scienze Naturali, 100, p. 135-139, 14 ref., 2012.
14039286 orbes, D. L. (Geological Survey of Canada, Natural Resources Canada, Dartmouth, NS, Canada); Manson, G. K.; Whalen, D. J. R.; Couture, N. J. and Hill, P. R. Coastal products of marine transgression in cold-temperate and high-latitude coastal-plain settings; Gulf of St Lawrence and Beaufort Sea: in Sedimentary coastal zones from high to low latitudes; similarities and differences (Martini, I. P.; et al.), Special Publication - Geological Society of London, 388, illus. incl. block diags., strat. cols., sects., sketch maps, 141 ref., May 13, 2014. (Online First).
Cold climate exerts a clear influence on the processes of marine transgression in mid- and high-latitude coastal-plain settings, but its signature in the depositional record is much clearer at high latitude. Both cases selected for this study are influenced by the legacy of past glaciation and the pervasive effects of ongoing Holocene marine transgression. Both are affected by sea ice. The high-latitude site lies within the zone of continuous permafrost and the abundance of excess ground ice along the Beaufort coast is the dominant factor distinguishing it from the mid-latitude Gulf of St Lawrence (GSL) setting and standard models of transgressive coasts elsewhere. In the southern GSL, the transgressive unconformity (TU) is at the seabed (or buried by a very thin veneer) across the inner shelf; shoreface sand moves landward, keeping pace with the transgressive front through deposition in barriers, dunes and estuaries. The pace of transgression in the Beaufort Sea is influenced by a number of distinctive periglacial erosion processes, including thermal abrasion and thaw subsidence. Marine transgression across this landscape creates intricate breached-lake estuaries and low sandy barrier beaches with limited dunes, leaving distinctive facies suites and geometry, while seaward sediment transport buries the TU on the inner shelf.
14046095 Walter Anthony, Katey M. (University of Alaska at Fairbanks, Water and Environmental Research Center, Fairbanks, AK) and Anthony, Peter. Constraining spatial variability of methane ebullition seeps in thermokarst lakes using point process models: Journal of Geophysical Research: Biogeosciences, 118(3), p. 1015-1034, illus. incl. 5 tables, sketch map, 88 ref., July 2013.
Ebullition is an important but highly heterogeneous mode of methane emission in lakes. Variability in both spatial distribution and temporal flux creates difficulty in constraining uncertainties in whole lake emission estimates. Analysis of short- and long-term flux measurements on 162 ebullition seeps in 24 panarctic lakes confirmed that seep classes, identified a priori according to bubble patterns in winter lake ice, have distinct associated fluxes irrespective of lake or region. To understand the drivers of ebullition's spatial variability and uncover ways to better quantify ebullition in field work, we combined point-process modeling with field measurements of 2679 GPS-marked and classified ebullition seeps in three Alaskan thermokarst (thaw) lakes that varied by region, permafrost type, and seep distribution. Spatial analysis of field data revealed that seeps cluster above thawed permafrost soil mounds in lake bottoms. Seep density and clustering, determined from field observations, were used as parameters in a Poisson cluster process model to simulate seeps across entire lake surfaces. Sampling results indicated that (1) applying seep-class mean flux values to unmeasured seeps counted on ice-bubble surveys does not compromise accuracy of whole lake flux estimates; (2) three distributed 50 m2 ice-bubble survey transects more accurately estimate mean lake ebullition than 17 dispersed 0.2 m2 bubble traps; and (3) the uncertainty associated with whole lake mean ebullition estimated by lake-ice survey transects is inversely related to seep density. Findings suggest that transect field data collected on a large number of widely distributed lakes can be combined to provide a well-constrained, bottom-up estimate of regional lake ebullition. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
14040753 Dymov, A. A. (Russian Academy of Sciences, Institute of Biology, Syktyvkar, Russian Federation); Zhangurov, E. V. and Startsev, V. V. Soils of the northern part of the Subpolar Urals; morphology, physicochemical properties, and carbon and nitrogen pools: Eurasian Soil Science, 46(5), p. 459-467, 35 ref., May 2013. Based on Publisher-supplied data.
The morphology and physicochemical properties of mountain-tundra and mountain-forest soils of the Subpolar Urals are analyzed. Gleyic humus-illuvial podburs, in combination with humus-illuvial podburs and raw-humus gleyzems, predominate in the mountain-tundra zone; permafrost-affected gleyzems and peat gleyzems with a shallow (30-50 cm) permafrost table are developed on colluvial fans at the foots-lopes. Iron-illuvial podzols, iron-illuvial svetlozems, eluviated burozems, texture-differentiated podzolic soils with a microprofile of a podzol, and gleyed peat-podzolic soils occur in the mountain-forest zone. The organic carbon and nitrogen pools in the soils considerably vary depending on the soil type and local landscape conditions. The organic carbon pool stored in the upper 50 cm of the soil profile varies from 7.7 to 39.3 kg/m2 in the mountain-tundra soils and from 6.5 to 11.8 kg/m2 in the mountain-forest soils. The corresponding values for the nitrogen pool are 0.4-2.4 and 0.4-0.8 kg/m2, respectively. Copyright 2013 Pleiades Publishing, Ltd.
14040754 Karavaeva, N. A. (Russian Academy of Sciences, Institute of Geography, Moscow, Russian Federation). Soil zonality of the Chukotka Upland: Eurasian Soil Science, 46(5), p. 468-483, 37 ref., May 2013. Based on Publisher-supplied data.
The vertical soil-geographic zonality of the Chukotka Upland in the area of the Amguema River valley can be considered a model vertical zonality in the Low Arctic regions at the interface between the continental and oceanic climates. The plain bottom of the valley has a continental climate. The surrounding mountains are under the influence of an oceanic climate, which is more pronounced in the low mountains and less pronounced in the medium-high mountains. Three altitudinal soil zones are distinguished: (1) the plain Subarctic zone with the absolute heights below 200-400 m a.s.l., where cryoturbated humus-impregnated peat-mucky gleyzems are developed from loamy substrates, and gleyed soddy podburs are developed from loamy sandy substrates; (2) the low-mountain zone of a creeping alder forest (the forest-tundra zone?) of the Low Arctic at the heights of 400-700 m a.s.l., where mucky-gray-humus humus-impregnated podzolized gleyzems are developed under tundra patches, cryoturbated peat-mucky high-humus-impregnated podzolized gleyzems are developed under creeping alder thickets, and pedoliths are exposed in the zones of landslides; and (3) the mountain Middle Arctic zone at elevations above 700 m a.s.l., where very thin soil films predominate; gray-humus cryometamorphic lithozems are developed from the eluvium of magmatic rocks, and humus-impregnated cryometamorphic soils with quicksand suprapermafrost horizons are developed from the eluvium of hard sedimentary rocks. Copyright 2013 Pleiades Publishing, Ltd.
14041146 Di Matteo, A. (Universita di Parma, Parma, Italy); Kuznetsova, T. V.; Nikolayev, V. I.; Spasskaya, N. N. and Yakumin, P. Izotopnyye issledovaniya kostnykh ostatkov Yakutskikh pleystotsenovykh loshadey [Isotopic studies of fossilized bones of Pleistocene horses of Yakutia]: Led i Sneg = Ice and Snow, 122, p. 93-101 (English sum.), illus. incl. 2 tables, 35 ref., 2013.
Well-conserved carcasses of ancient large mammals can be found in permafrost of North-eastern Siberia. Mummified remains of ancient horses are rather rare ones. Complex stable isotope studies of 5 mummies and several horses' bones from Northern Yakutia were carried out. Results obtained testify to possibility to use carbon isotope composition of hydroxylapatite carbonate from horses' bones as palaeoclimatic indicator. It was determined relative (warmer or cooler, more dry or humid) environmental conditions during our horses' lives. Preliminary data allow us to suppose that in Late Pleistocene lived in similar landscapes as well in Yakutia as Western Europe.
14041145 Shpolyanskaya, N. A. (Moskovskiy Gosudarstvennyy Universitet Imeni M. V. Lomonosova, Moscow, Russian Federation). Podzemnyye l'dy-pokazatel' pleystotsenovoy istorii Rossiyskoy Arktiki [Ground ice as an indicator of the Pleistocene history of the Russian Arctic]: Led i Sneg = Ice and Snow, 122, p. 69-82 (English sum.), illus. incl. sketch map, strat. col., 1 table, sect., 43 ref., 2013.
Based on the analysis of massive ground ice origin, the geological development of the Russian Arctic in the Quaternary period has been considered. A classification of massive ice with two new genetic types (sub-marine and coastal-marine) and new mechanism of their formation have been proposed by the author. The possibility of permafrost formation with massive ice directly in marine environments has been established. Significant differences in the geological development of western and eastern Arctic, particularly in the transgressive-regressive mode, have been revealed. This calls into question the leading role of glacial eustatic processes in sea level fluctuations and brings to the fore the role of tectonic processes.
14046043 Verba, M. L. (Sevmorgeo, St. Petersburg, Russian Federation). Kollektornyye svoystva porod osadochnogo chekhla arkhipelaga Shpitsbergen [Properties of sedimentary reservoir rocks in the Svalbard Archipelago]: Neftegazovaya Geologiya. Teoriya i Praktika, 8(1), 45 p. (English sum.), illus. incl. strat. col., 3 tables, sketch map, 34 ref., 2013.
The data obtained by the author during field works in the vicinity of the Barentsburg and Pyramid mines of Arktikugol complex of enterprises are analyzed. Additional information obtained by previous researchers in various areas of the Svalbard archipelago, including wells Grumantskaya-1 and Raddedalen-1, is used, as well as the results of petrophysical study of the collection of geologists of Polar Marine Geological Expedition and VNIIOkeangeologia. The results of laboratory study of porosity, density, velocity and magnetic properties are presented. It is concluded that the Phanerozoic sediments' section is not so hopeless in terms of porosity and permeability as previously thought. Furthermore, the section of Svalbard archipelago has similar features with the section of the Timan-Pechora province in terms of reservoir properties (one of the prerequisites for petroleum potential). The different types of reservoirs are identified on the basis of petrophysical properties in the Lower Paleozoic, Middle Devonian, Lower and Middle Carboniferous, Middle Triassic and Cretaceous-Paleocene strata, which sometimes contain fluid migration. The halogen bands and permafrost rocks are considered as confining beds.
14045454 Mishra, U. (Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA) and Riley, W. J. Alaskan soil carbon stocks; spatial variability and dependence on environmental factors: Biogeosciences, 9(9), p. 3637-3645, illus. incl. 2 tables, sketch map, 51 ref., 2012.
The direction and magnitude of soil organic carbon (SOC) changes in response to climate change depend on the spatial and vertical distributions of SOC. We estimated spatially resolved SOC stocks from surface to C horizon, distinguishing active-layer and permafrost-layer stocks, based on geospatial analysis of 472 soil profiles and spatially referenced environmental variables for Alaska. Total Alaska state-wide SOC stock was estimated to be 77 Pg, with 61% in the active-layer, 27% in permafrost, and 12% in non-permafrost soils. Prediction accuracy was highest for the active-layer as demonstrated by highest ratio of performance to deviation (1.5). Large spatial variability was predicted, with whole-profile, active-layer, and permafrost-layer stocks ranging from 1-296 kg C m-2, 2-166 kg m-2, and 0-232 kg m-2, respectively. Temperature and soil wetness were found to be primary controllers of whole-profile, active-layer, and permafrost-layer SOC stocks. Secondary controllers, in order of importance, were found to be land cover type, topographic attributes, and bedrock geology. The observed importance of soil wetness rather than precipitation on SOC stocks implies that the poor representation of high-latitude soil wetness in Earth system models may lead to large uncertainty in predicted SOC stocks under future climate change scenarios. Under strict caveats described in the text and assuming temperature changes from the A1B Intergovernmental Panel on Climate Change emissions scenario, our geospatial model indicates that the equilibrium average 2100 Alaska active-layer depth could deepen by 11 cm, resulting in a thawing of 13 Pg C currently in permafrost. The equilibrium SOC loss associated with this warming would be highest under continuous permafrost (31%), followed by discontinuous (28%), isolated (24.3%), and sporadic (23.6%) permafrost areas. Our high-resolution mapping of soil carbon stock reveals the potential vulnerability of high-latitude soil carbon and can be used as a basis for future studies of anthropogenic and climatic perturbations.
14046874 Gradzinski, Michal (Jagiellonian University, Institute of Geological Sciences, Cracow, Poland); Hercman, Helena and Staniszewski, Krzysztof. Middle Pleistocene carbonate-cemented colluvium in southern Poland; its depositional processes, diagenesis and regional palaeoenvironmental significance: Sedimentary Geology, 306, p. 24-35, illus. incl. 3 tables, geol. sketch maps, 99 ref., June 1, 2014.
A colluvial origin is postulated for the enigmatic relic mantle of immature, carbonate-cemented rudites on the bedrock slope of Krakow Highland, preserved in the area of Kwaczala Gullies. The deposits comprise four sedimentary facies: (A) sporadic clast-supported openwork conglomerates; (B) predominant matrix-supported massive conglomerates, some with a coarse-tail normal grading; (C) subordinate sheets of parallel stratified and/or ripple cross-laminated fine-grained sandstones; and (D) local coarse-grained sandstones with gently inclined parallel stratification. The 230Th-U dating of sparry calcite cements points to the penultimate Odranian/Warthanian interglacial. The debris was derived from local bedrock, inferred to have been frost-shattered in permafrost conditions during the Odranian glacial. Colluvial resedimentation was triggered by the rapid change in environment conditions brought by early deglaciation. Dense-snow/slush flows and slush-laden watery debris flows are thought to have transferred limestone debris from the upper to middle hillslope, where siliciclastic sand matrix was incorporated and solifluctional creep prevailed, accompanied by slope sheetwash processes. Carbonate cementation of the talus occurred in phreatic conditions during the penultimate Odranian/Warthanian interglacial (marine isotope stage 7), when soils formed and local springs supplied carbonate-saturated groundwater. The patchy preservation of cemented colluvium indicates its erosional relics. The Pleistocene colluvial mantle in the Krakow Highland was probably extensive, but was removed by subsequent erosion where non-cemented. Abstract Copyright (2014) Elsevier, B.V.
14046913 Pautler, Brent G. (University of Toronto, Environmental NMR Center, Toronto, ON, Canada); Reichart, Gert-Jan; Sanborn, Paul T.; Simpson, Myrna J. and Weijers, Johan W. H. Comparison of soil derived tetraether membrane lipid distributions and plant-wax dD compositions for reconstruction of Canadian Arctic temperatures: Palaeogeography, Palaeoclimatology, Palaeoecology, 404, p. 78-88, illus. incl. chart, 2 tables, sketch map, 83 ref., June 15, 2014.
Polar amplification of climate warming has received much attention as these rapidly rising temperatures have the potential to alter ecosystem function and biogeochemical cycles. In particular carbon preserved in Arctic tundra soil and permafrost may be especially vulnerable resulting in carbon cycle perturbations providing an additional positive feedback to climate change. Reliable methods for reconstructing past temperature changes in polar regions have been established from ice cores and marine sediments; however techniques for the continental terrestrial environments are lacking, but are imperative to examine polar amplification of climate warming. Here we compare two molecular methods for reconstructing continental annual mean air temperature (MAT) for the Canadian Arctic based on the distribution of soil bacterial-derived glycerol dialkyl glycerol tetraether (GDGT) membrane lipids (MBT-CBT proxy) and the hydrogen isotopic composition (dD) of plant wax-derived n-alkanes. These two proxies were applied to both modern soil and paleosols collected from the Yukon Territory, Canada, to evaluate both the accuracy of the reconstructed absolute temperatures as well as the relative change in temperature between the Last Glacial and the Holocene. Branched GDGT-based estimates using the recently revised MBT'-CBT calibration are overall higher by ca. 6°C compared to the original calibration. MAT estimates for modern soils based on the original MBT-CBT calibration are comparable with those based on the dD of extracted C29n-alkanes and instrumental data, however produced a 6°C higher temperature signal for the glacial paleosols. Therefore, branched GDGT based temperature reconstructions for glacial soils in the high Arctic may represent the higher temperatures at the time of soil formation when bacterial activity was optimal whereas dD of C29n-alkane plant lipids appear to integrate an average annual signal. When used in tandem, these geochemical proxies may provide a more comprehensive method for reconstructing Arctic paleoclimate. Abstract Copyright (2014) Elsevier, B.V.
14040624 Ringeval, B. (University of Bristol, Bristol Research Initiative for the Dynamic Global Environment, Bristol, United Kingdom); Hopcroft, P. O.; Valdes, P. J.; Ciais, P.; Ramstein, G.; Dolman, A. J. and Kageyama, M. Response of methane emissions from wetlands to the last glacial maximum and an idealized Dansgaard-Oeschger climate event; insights from two models of different complexity: Climate of the Past, 9(1), p. 149-171, illus. incl. 2 tables, 49 ref., 2013. Includes appendices; published in Climate of the Past Discussion: 1 August 2012, URL: http://www.clim-past-discuss.net/8/3093/2012/cpd-8-3093-2012.html; accessed in May, 2013.
The role of different sources and sinks of CH4 in changes in atmospheric methane ([CH4]) concentration during the last 100 000 yr is still not fully understood. In particular, the magnitude of the change in wetland CH4 emissions at the Last Glacial Maximum (LGM) relative to the pre-industrial period (PI), as well as during abrupt climatic warming or Dansgaard-Oeschger (D-O) events of the last glacial period, is largely unconstrained. In the present study, we aim to understand the uncertainties related to the parameterization of the wetland CH4 emission models relevant to these time periods by using two wetland models of different complexity (SDGVM and ORCHIDEE). These models have been forced by identical climate fields from low-resolution coupled atmosphere-ocean general circulation model (FAMOUS) simulations of these time periods. Both emission models simulate a large decrease in emissions during LGM in comparison to PI consistent with ice core observations and previous modelling studies. The global reduction is much larger in ORCHIDEE than in SDGVM (respectively -67 and -46%), and whilst the differences can be partially explained by different model sensitivities to temperature, the major reason for spatial differences between the models is the inclusion of freezing of soil water in ORCHIDEE and the resultant impact on methanogenesis substrate availability in boreal regions. Besides, a sensitivity test performed with ORCHIDEE in which the methanogenesis substrate sensitivity to the precipitations is modified to be more realistic gives a LGM reduction of -36%. The range of the global LGM decrease is still prone to uncertainty, and here we underline its sensitivity to different process parameterizations. Over the course of an idealized D-O warming, the magnitude of the change in wetland CH4 emissions simulated by the two models at global scale is very similar at around 15 Tg yr-1, but this is only around 25% of the ice-core measured changes in [CH4]. The two models do show regional differences in emission sensitivity to climate with much larger magnitudes of northern and southern tropical anomalies in ORCHIDEE. However, the simulated northern and southern tropical anomalies partially compensate each other in both models limiting the net flux change. Future work may need to consider the inclusion of more detailed wetland processes (e.g. linked to permafrost or tropical floodplains), other non-wetland CH4 sources or different patterns of D-O climate change in order to be able to reconcile emission estimates with the ice-core data for rapid CH4 events.
14045452 Rontani, J. F. (Aix-Marseille University, Mediterranean Institute of Oceanography, Marseille, France); Charriere, B.; Petit, M.; Vaultier, F.; Heipieper, H. J.; Link, H.; Chaillou, G. and Sempéré, R. Degradation state of organic matter in surface sediments from the southern Beaufort Sea; a lipid approach: Biogeosciences, 9(9), p. 3513-3530, illus. incl. 2 tables, sketch map, 105 ref., 2012.
For the next decades significant climatic changes should occur in the Arctic zone. The expected destabilisation of permafrost and its consequences for hydrology and plant cover should increase the input of terrigenous carbon to coastal seas. Consequently, the relative importance of the fluxes of terrestrial and marine organic carbon to the seafloor will likely change, strongly impacting the preservation of organic carbon in Arctic marine sediments. Here, we investigated the lipid content of surface sediments collected on the Mackenzie basin in the Beaufort Sea. Particular attention was given to biotic and abiotic degradation products of sterols and monounsaturated fatty acids. By using sitosterol and campesterol degradation products as tracers of the degradation of terrestrial higher plant inputs and brassicasterol degradation products as tracers of degradation of phytoplanktonic organisms, it could be observed that autoxidation, photooxidation and biodegradation processes act much more intensively on higher plant debris than on phytoplanktonic organisms. Examination of oxidation products of monounsaturated fatty acids showed that photo- and autoxidation processes act more intensively on bacteria than on phytodetritus. Enhanced damages induced by singlet oxygen (transferred from senescent phytoplanktonic cells) in bacteria were attributed to the lack of an adapted antioxidant system in these microorganisms. The strong oxidative stress observed in the sampled sediments resulted in the production of significant amounts of epoxy acids and unusually high proportions of monounsaturated fatty acids with a trans double bond. The formation of epoxy acids was attributed to peroxygenases (enzymes playing a protective role against the deleterious effects of fatty acid hydroperoxides in vivo), while cis/trans isomerisation was probably induced by thiyl radicals produced during the reaction of thiols with hydroperoxides. Our results confirm the important role played by abiotic oxidative processes in the degradation of marine bacteria and do not support the generally expected refractory character of terrigenous material deposited in deltaic systems.
14046668 Majorowicz, Jacek (University of Alberta, Department of Physics, Edmonton, AB, Canada); Grasby, S. E.; Safanda, J. and Beauchamp, B. Gas hydrate contribution to Late Permian global warming: Earth and Planetary Science Letters, 393, p. 243-253, illus., 108 ref., May 1, 2014.
Rapid gas hydrate release (the "clathrate gun" hypothesis) has been invoked as a cause for the rapid global warming and associated negative carbon isotope excursion observed during the Latest Permian Extinction (LPE). We modeled the stability of gas hydrates through a warming Middle to Late Permian world, considering three settings for methane reservoirs: 1) terrestrial hydrates, 2) hydrates on exposed continental shelves during glacial sea level drop, and 3) hydrates in deep marine settings. Model results show that terrestrial hydrates would rapidly destabilize over ~400 ky after deglaciation for moderate heatflow (40 mW/m2), and more rapidly for higher heat flow values. Exposed continental shelves would lose hydrates even more rapidly, after being flooded due to loss of ice storage on land. These two major hydrate reservoirs would thus have destabilized during the Middle to Late Permian climate warming, well prior to the LPE event. However, they may have contributed to the >2 ppm negative C-isotopic shift during the late Middle Permian. Deep marine hydrates would have remained stable until LPE time. Rapid warming of deep marine waters during this time could have triggered destabilization of this reservoir, however given the configuration of one super continent, Pangea, hydrate bearing continental slopes would have been less extensive than modern day. This suggests that any potential gas hydrate release would have had only a minor contributing impact to the runaway greenhouse during the Latest Permian extinction. Abstract Copyright (2014) Elsevier, B.V.
14038731 Zacny, K. (Honeybee Robotics, Pasadena, CA); Paulsen, G.; McKay, C. P.; Glass, B.; Davé, A.; Davila, A. F.; Marinova, M.; Mellerowicz, B.; Heldmann, J.; Stoker, C.; Cabrol, Nathalie; Hedlund, M. and Craft, J. Reaching 1 m deep on Mars; the icebreaker drill: Astrobiology, 13(12), p. 1166-1198, illus. incl. 3 tables, 77 ref., December 16, 2013.
The future exploration of Mars will require access to the subsurface, along with acquisition of samples for scientific analysis and ground-truthing of water ice and mineral reserves for in situ resource utilization. The Icebreaker drill is an integral part of the Icebreaker mission concept to search for life in ice-rich regions on Mars. Since the mission targets Mars Special Regions as defined by the Committee on Space Research (COSPAR), the drill has to meet the appropriate cleanliness standards as requested by NASA's Planetary Protection Office. In addition, the Icebreaker mission carries life-detection instruments; and in turn, the drill and sample delivery system have to meet stringent contamination requirements to prevent false positives. This paper reports on the development and testing of the Icebreaker drill, a 1 m class rotary-percussive drill and triple redundant sample delivery system. The drill acquires subsurface samples in short, approximately 10 cm bites, which makes the sampling system robust and prevents thawing and phase changes in the target materials. Autonomous drilling, sample acquisition, and sample transfer have been successfully demonstrated in Mars analog environments in the Arctic and the Antarctic Dry Valleys, as well as in a Mars environmental chamber. In all environments, the drill has been shown to perform at the "1-1-100-100" level; that is, it drilled to 1?m depth in approximately 1 hour with less than 100 N weight on bit and approximately 100 W of power. The drilled substrate varied and included pure ice, ice-rich regolith with and without rocks and with and without 2% perchlorate, and whole rocks. The drill is currently at a Technology Readiness Level (TRL) of 5. The next-generation Icebreaker drill weighs 10 kg, which is representative of the flightlike model at TRL 5/6.
14046098 Tei, Shunsuke (Hokkaido University, Graduate School of Environmental Science, Sapporo, Japan); Sugimoto, Atsuko; Yonenobu, Hitoshi; Yamazaki, Takeshi and Maximov, Trofim C. Reconstruction of soil moisture for the past 100 years in Eastern Siberia by using d13C of larch tree rings: Journal of Geophysical Research: Biogeosciences, 118(3), p. 1256-1265, illus. incl. 1 table, 58 ref., July 2013.
A stable carbon isotope ratio (d13C) chronology for the past 100 years was developed from larch tree rings in eastern Siberia (near Yakutsk, 62°14'N, 129°37'E), to reconstruct past soil moisture water equivalent (SWE). Based on the correlation analyses between SWE and tree ring d13C, we developed a linear regression model for SWE in the late growing period (LGP: 15 July to 31 August) using annual tree ring d13C, which was calculated from the combination of latewood in a current year and earlywood in the following year, and then reconstructed SWE (LGP) for 1908-2007. Reconstructed SWE was compared with factors such as the output of the land surface model, annual precipitation, and Palmer Drought Severity Index for July. From the results, the reconstructed SWE appears reasonable and shows a large variation, including repeated occurrences of severe drought and an unprecedented high soil moisture event in 2006-2007 during the past 100 years. The reconstruction also captured a past documented record of severe drought in the 1940s. Despite the generally good performance of the reconstruction, by the 1930s the estimated SWE was higher than that expected from the annual precipitation. Tree ring width and d13C were negatively correlated in most periods. However, the negative correlation was weaker for the period from 1919 to 1925, when relatively low air temperature was observed. This result suggests that the rate of photosynthesis, together with the degree of stomata opening, also affected the tree ring d13C during cool periods. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved.
14040644 Murdock, K. J. (University of Massachusetts at Amherst, Amherst, MA); Wilkie, K. and Brown, L. L. Rock magnetic properties, magnetic susceptibility, and organic geochemistry comparison in core LZ1029-7 Lake El'gygytgyn, Russia Far East: Climate of the Past, 9(1), p. 467-479, illus. incl. 1 table, sketch maps, 47 ref., 2013. Part of special issue no. 48, Initial results from Lake El'gygytgyn, western Beringia; first time-continuous Pliocene-Pleistocene terrestrial record from the Arctic, edited by Brigham-Grette, J., URL: http://www.clim-past.net/special_issue48.html; published in Climate of the Past Discussion: 18 September 2012, URL: http://www.clim-past-discuss.net/8/4565/2012/cpd-8-4565-2012.html; accessed in May, 2013.
Susceptibility measurements performed on initial short (~ 16 m) cores PG1351 taken from Lake El'gygytgyn exhibited a large range in values. This observation led to the suggestion of widespread magnetite dissolution within the sediments due to anoxic conditions within the lake. Rock magnetic properties and their comparison with magnetic susceptibility, total organic carbon (TOC), and bulk d13Corg proxies in core LZ1029-7, taken from the same site as the previously drilled PG1351, provide an insight into the character of the magnetic minerals present within the lake and can further the understanding of processes that may be present in the newer long core sediments. Susceptibility measurements (c) of discrete samples corroborate the two order of magnitude difference seen in previous continuous susceptibility measurements (k), correlating high values with interglacial periods and low values with glacial intervals. Hysteresis parameters indicate that the majority of the magnetic material to be magnetite of PSD size. TOC values increase while d13Corg values decrease in one section of LZ1029-7, which is defined as the Last Glacial Maximum (LGM), and help confine the age of the core to approximately 62 ka. Increases in TOC during the most recent glacial interval suggest increased preservation of organic carbon during this period. High TOC and low magnetic susceptibility during the LGM support the theory of perennial ice cover during glacial periods, which would lead to lake stratification and therefore anoxic bottom water conditions. Low temperature magnetic measurements confirmed the presence of magnetite, but also indicated titanomagnetite and possibly siderite, rhodochrosite, and/or vivianite were present. The latter three minerals are found only in anoxic environments, and further support the notion of magnetite dissolution.
14045634 Zander, Anja (Universität zu Köln, Geographisches Institut, Cologne, Germany) and Hilgers, A. Potential and limits of OSL, TT-OSL, IRSL and pIRIR290 dating methods applied on a middle Pleistocene sediment record of Lake El'gygytgyn, Russia: Climate of the Past, 9(2), p. 719-733, illus. incl. sketch map, 6 tables, sect., 54 ref., 2013. Includes supplement, URL: http://www.clim-past.net/9/719/2013/cp-9-719-2013-supplement.pdf; part of special issue no. 48, Initial results from Lake El'gygytgyn, western Beringia; first time-continuous Pliocene-Pleistocene terrestrial record from the Arctic, edited by Brigham-Grette, J., et al., URL: http://www.clim-past.net/special_issue48.html; published in Climate of the Past Discuss.: 28 September 2012, URL: http://www.clim-past-discuss.net/8/4779/2012/cpd-8-4779-2012.html; accessed in June, 2013.
This study tests the paleomagnetic and proxy-data based Mid- to Upper Pleistocene sediment deposition history of Lake El'gygytgyn by applying different approaches of luminescence dating techniques on sediment cores taken from the centre of the 175 m deep lake. For dating polymineral and quartz fine grains (4-11 mm grain size range) were extracted from nine different levels from the upper 28 m of sediment cores 5011-1A and 5011-1B. According to the independent age model, the lowest sample from 27.8-27.9 m below lake bottom level correlates to the Brunhes-Matuyama (B/M) reversal. Polymineral sub-samples were analysed by infra-red stimulated luminescence (IRSL) and post-IR IRSL measured at 290 °C (pIRIR290) using single aliquot regenerative dose (SAR) sequences. SAR protocols were further applied to measure the blue light optically stimulated luminescence (OSL) and thermally-transferred OSL (TT-OSL) of fine-grained quartz supplemented by a multiple aliquot approach. Neither low temperature IRSL measurements at 50 °C nor any OSL dating approach on quartz yielded reliable results. Deconvolution of their dose response curves revealed a pseudo-increase of the dose response curves and explains the observed underestimation. The pIRIR protocol applied to polymineral fine grains was the only luminescence technique able to provide dating results of acceptable accuracy up to ca. 700 ka when correlated to the existing proxy-data and paleomagnetic based age record. We present the potential and limits of the different dating techniques and a correlation of pIRIR290 results with the proxy-data based age model.
14038027 Kaleschke, Lars and Kutzbach, Lars. Schützende Decke in Gefahr [A protective cover in danger]: Forschung (Boppard), 2012(4), p. 6-11, 2012.
14038981 Al-Omari, Asaad (Universite d'Orléans, Orleans, France); Brunetaud, Xavier; Beck, Kevin and Al-Mukhtar, Muzahim. Effect of thermal stress, condensation and freezing-thawing action on the degradation of stones on the Castle of Chambord, France: Environmental Earth Sciences, 71(9), p. 3977-3989, illus. incl. 6 tables, 23 ref., May 2014.
This work consists in estimating the role of climatic conditions in the degradation of two French limestones, tuffeau and Richemont stone, used in the construction and the restoration of the Castle of Chambord, the largest castle in the Loire Valley, France. Meteorological data, air temperature, air relative humidity and rainfall were statistically analysed in combination with stone data from thermal-humidity sensors inserted into the walls. The climatic conditions of the surrounding area were described to assess their role in enhancing the degradation of the stones through three weathering processes: thermal stress, condensation and freezing-thawing. The damage risks due to the weathering processes were taken into account not only through the bulk effects on the stone surfaces, but also their effects were extended to investigate the damage that occurs within the porous structure of the stone. Field observations showed that the main patterns of degradation affecting the stones of the castle are biological colonization and stone detachment in the form of stone spalling and exfoliation. The results of the analysis show that there is no risk of damage to the stones due to thermal stress. Moreover, the two stones experience similar overall trends against freezing-thawing processes. Finally, this study clearly highlights the important role of condensation in the degradation of the stones of the castle. Copyright 2013 Springer-Verlag Berlin Heidelberg
14038998 Celik, Mustafa Yavuz (Afyon Kocatepe University, Afyon Vocational School, Afyonkarahisar, Turkey); Akbulut, Huseyin and Ergul, Ayse. Water absorption process effect on strength of Ayazini tuff, such as the uniaxial compressive strength (UCS), flexural strength and freeze and thaw effect: Environmental Earth Sciences, 71(9), p. 4247-4259, illus. incl. strat. col., 3 tables, geol. sketch maps, 59 ref., May 2014.
Tuffs have been used as a construction material possibly since ancient times. In Afyonkarahisar, Turkey, there are numerous buildings constructed by tuff. Tuff has been a local construction material, during the Roman, Seljuk and Ottoman periods. Even though tuffs have relatively low durability and low strength values compared to marble, etc., they have survived with no major deterioration failures on many historical buildings. It has also been preferred because of its high porous texture, lightweight and easy shaping and process properties in the building sector. Naturally, it would be easily affected by water and humidity because of its porous structure. However, having this kind of structure leads to poor durability properties due to keeping water in it. The main objective of this study was to evaluate the physical and mechanical properties of the tuff quarried from the region and possible water effect, which may lead to degradation of its strength and durability of the material, thereby shortening the life span of the building structure used. Samples, which were tested after exposing to water and the freeze and thaw effects, were measured at a certain time. In this study, uniaxial compressive strength and flexural strength tests were conducted on test samples. The test results indicate that water may deteriorate the tuff's strength properties and durability of the materials in due time. Copyright 2013 Springer-Verlag Berlin Heidelberg
14041154 Briggs, Kevin M. (University of Southampton, Faculty of Engineering and the Environment, Southampton, United Kingdom); Smethurst, Joel A.; Powrie, William and O'Brien, Anthony S. Wet winter pore pressures in railway embankments: Proceedings of the Institution of Civil Engineers. Geotechnical Engineering, 166(5), p. 451-465, illus. incl. 2 tables, 39 ref., October 2013.
14045743 van Zeyl, D. P. (J. D. Mollard and Associates, Regina, SK, Canada); Penner, L. A. and Halim, R. A. A slope failure caused by drainage cutoff through the advancement of seasonal frost, Hudson Bay Lowland: Landslides, 10(3), p. 315-322, illus. incl. sketch maps, 36 ref., June 2013.
A failure occurred between December 14 and 17, 2008 in the upper part of a 45-m high, northwest facing bank of the Nelson River in northern Manitoba (56.687°N, 93.777°W). The slope failure occurred at a spring site in a bay associated with a buried valley. The sediment input to the river from this event is roughly 20,000 to 25,000 m3. The source zone is made up of 25 m of water-bearing sand and gravel confined between ice-rich silty clay at the top of the bank and laminated to rhythmically bedded silt and clay at the base of the section. The collapse was confined to the material above the basal silts and clays and was associated with a perched groundwater flow system. A strong argument for drainage cutoff by the advancement of seasonal frost has been demonstrated through the correlation of the bank collapse with the timing of a significant cold snap recorded at two nearby weather stations. The failure illustrates the importance of stratigraphy in controlling bank erosion in this area. Previously, fluvial erosion was seen as an important control on mass wasting in Horseshoe Bay. However, surface information suggests that no toe erosion except to remove the slide deposit has occurred at this site since 2004. Copyright 2013 Springer-Verlag Berlin Heidelberg and The Author(s)
14045541 Sargent, Paul (Newcastle University, School of Civil Engineering and Geosciences, Newcastle upon Tyne, United Kingdom); Hughes, Paul N.; Rouainia, Mohamed and White, Maggie L. The use of alkali activated waste binders in enhancing the mechanical properties and durability of soft alluvial soils: Engineering Geology, 152(1), p. 96-108, illus. incl. 6 tables, 39 ref., January 18, 2013.
This paper presents recent work in utilising industrial by-products as sustainable binders for use in deep soil mixing, to enhance the geotechnical properties of soft soils. The study has used geotechnical and mineralogical tests to determine the performance of the binders when incorporated into an artificial silty sand soil. Comparisons with the strength and durability of untreated and stabilised soils have been made. The study indicates that from the by-products tested, soils stabilised with alkali activated blast furnace slag resulted in the greatest strength and durability improvements; with other materials tested showing smaller improvements. The addition of alkali activators has been observed to allow pozzolanic reactions to occur, which has led to improved mechanical properties; primarily strength, which increased with time. The durability of the soil was improved by the additions of by-products, though alkali activation did not cause significant additional increase in durability. Abstract Copyright (2013) Elsevier, B.V.
14047127 Francke, A. (University of Cologne, Institute for Geology and Mineralogy, Cologne, Germany); Wennrich, V.; Sauerbrey, M.; Juschus, O.; Melles, M. and Brigham-Grette, J. Multivariate statistic and time series analyses of grain-size data in Quaternary sediments of Lake El'gygytgyn, NE Russia: Climate of the Past, 9(6), p. 2459-2470, illus. incl. sects., sketch maps, 65 ref., 2013. Part of special issue no. 48, Initial results from lake El'gygytgyn, western Beringia; first time-continuous Pliocene-Pleistocene terrestrial record from the Arctic published in Climate of the Past Discussion: 14 January 2013, edited by Brigham-Grette, J., et al., URL: http://www.clim-past.net/special_issue48.html; accessed in June., 2014.
Lake El'gygytgyn, located in the Far East Russian Arctic, was formed by a meteorite impact about 3.58 Ma ago. In 2009, the International Continental Scientific Drilling Program (ICDP) at Lake El'gygytgyn obtained a continuous sediment sequence of the lacustrine deposits and the upper part of the impact breccia. Here, we present grain-size data of the past 2.6 Ma. General downcore grain-size variations yield coarser sediments during warm periods and finer ones during cold periods. According to principal component analysis (PCA), the climate-dependent variations in grain-size distributions mainly occur in the coarse silt and very fine silt fraction. During interglacial periods, accumulation of coarser material in the lake center is caused by redistribution of clastic material by a wind-induced current pattern during the ice-free period. Sediment supply to the lake is triggered by the thickness of the active layer in the catchment and the availability of water as a transport medium. During glacial periods, sedimentation at Lake El'gygytgyn is hampered by the occurrence of a perennial ice cover, with sedimentation being restricted to seasonal moats and vertical conduits through the ice. Thus, the summer temperature predominantly triggers transport of coarse material into the lake center. Time series analysis that was carried out to gain insight into the frequency of the grain-size data showed variations predominately on 98.5, 40.6, and 22.9 kyr oscillations, which correspond to Milankovitch's eccentricity, obliquity and precession bands. Variations in the relative power of these three oscillation bands during the Quaternary suggest that sedimentation processes at Lake El'gygytgyn are dominated by environmental variations caused by global glacial-interglacial variations (eccentricity, obliquity), and local insolation forcing and/or latitudinal teleconnections (precession), respectively.
14040527 Gauthier, D. (Queen's University, Department of Geological Sciences and Geological Engineering, Kingston, ON, Canada) and Hutchinson, D. J. Evaluation of potential meteorological triggers of large landslides in sensitive glaciomarine clay, Eastern Canada: Natural Hazards and Earth System Sciences (NHESS), 12(11), p. 3359-3375, illus. incl. 5 tables, sketch maps, 49 ref., 2012.
Heavy rains spread over some interval preceding large landslides in sensitive glaciomarine clay in eastern Canada are often noted as a triggering or causative factor in case studies or research reports for individual landslides, although the quantity or duration of the triggering rain event has never been characterized adequately. We selected five large landslide events that occurred in the glaciomarine clay in eastern Canada, and calculated cumulative antecedent precipitation for intervals ranging between one and 365 days preceding each event. We also calculated the antecedent precipitation values for every other day in the record, and computed the relative rank of the landslide day within the complete record. Our results show that several intervals for each landslide event are highly ranked - including those preceding a presumably earthquake-triggered landslide - but overall the rankings were highly variable, ranging between 99% and 6%. The set of highest-ranking intervals are unique for each event, including both short and long-term cumulative precipitation. All of the landslides occurred in the spring months, and the release of sequestered surface and ground water during the spring ground thaw may be related to the timing of the large landslides, so that the evolution of ground frost in the early winter may be of interest for landslide prediction. We found no simple precipitation threshold for triggering large landslides in sensitive glaciomarine clay in eastern Canada, suggesting that some complex temporal and spatial combination of pre-conditions, external energy (e.g. earthquakes), precipitation triggers and other factors such as ground frost formation and thaw are required to trigger a landslide.
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