DOCSLIB.ORG

The Experimental Simulation of Ice-Wedge Casting

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Experimental Simulation of Ice-Wedge Casting Permafrost, Phillips, Springman & Arenson (eds) © 2003 Swets & Zeitlinger, Lisse, ISBN 90 5809 582 7 The experimental simulation of ice-wedge casting J.B. Murton Department of Geography, University of Sussex, Brighton, UK C. Harris Department of Earth Sciences, University of Cardiff, UK ABSTRACT: This paper describes a new methodology to simulate ice-wedge casting by scaled physical modelling experiments in a geotechnical centrifuge. The purpose of the experiments is to determine the effect of host sediment granulometry and ice content on (a) the mechanisms of casting and (b) the size and structure of casts. Six models were constructed with host sediments comprising medium sand, loessic silt and silt-clay mixtures, and gravimetric moisture contents ranging from ϳ15% to 60%. The models thawed from the surface downwards. Model ice wedges were 150 mm high and tapered uniformly downward from a maximum true width of 50 mm, equivalent to prototype- scale wedges 4.5 m high and р1.5 m wide. Model 6 data on temperature, pore-water pressure and drainage during thaw, and on cast geometry after thaw demonstrate the potential of this approach to the study of ice-wedge casting. 1 INTRODUCTION described in an unpublished study by T. Rudzinska (1972, cited in Jahn 1975, pp. 72–73). Alternating layers Ice-wedge casts are key stratigraphic indicators of for- of gravel, sand and silt (ϳ10–40 mm thick) were placed mer permafrost and are often used to reconstruct in a small vessel and the sediment frozen. A wedge- palaeotemperatures (Huijzer and Vandenberghe 1998, shaped hole was cut in the middle of the frozen sedi- Murton & Kolstrup 2003). However, the mechanisms ment, filled with water and the vessel again chilled, of casting and their controlling factors have rarely producing an artificial ice wedge ϳ80 mm high and been studied and are difficult to monitor in the field with a maximum width of ϳ40 mm. Above the wedge (Dylik 1966, Jahn 1975, Harry & Gozdzik 1988, and host sediment was laid a sand layer ϳ10 mm thick. Murton & French 1993). Two key factors that that are The sediment was thawed and then refrozen, before cut- believed to influence casting are the particle size and ting the sediment block in half to compare the resultant ice content of the host sediment (Black 1976). A new ice-wedge cast with the size and shape of the initial ice approach to verify the influence of these factors is to wedge. The experiment was repeated using two freeze- simulate casting by laboratory modelling experiments thaw cycles to determine the effect of repetitive freeze- and to compare the artificial casts with natural ones. thaw on the cast structure. This approach permits (1) control of particle size and The experiments caused downturning of sediment ice content; (2) monitoring of temperature, pore pres- layers into the cast due to subsidence or collapse, pro- sure and cast development during thaw; and (3) meas- ducing a “cone-in-cone” structure. In addition, a sedi- urement of the initial ice wedge and the final cast. ment lining (ϳ3 mm thick) formed around the lower The objectives of this paper are to (i) describe the sides of one cast, the sediment deriving from within the new experimental methodology using scaled centrifuge ice wedge. The cast was reported to be “larger and modelling, and (ii) discuss the results from one test in deeper” than the former ice wedge, and Rudzinska con- order to demonstrate the potential of this new approach cluded that the degree of sediment subsidence depends to studies of ice-wedge casting. A companion paper on texture and the number of freeze-thaw cycles. will describe the results from all six tests and evaluate The approach taken in Rudzinska’s experiment their significance to the cryostratigraphic record applies only at the small scale at which it was con- (Harris and Murton in prep.). First we describe a previ- ducted. To apply the results to the field scale it is ous experiment to simulate ice-wedge casting in order essential to reproduce the correct self-weight stresses to highlight the necessity of correct scaling of stresses associated with thaw of the upper few metres of soil. in thawing soil. This can be achieved either by carrying out full-scale laboratory experiments or, more simply, by centrifuge 2 PREVIOUS EXPERIMENT modeling in which 1/N scale models are thawed at N times gravity. The centrifuge scaling laws applicable To our knowledge, only one previous laboratory experi- to simulating the degradation of the upper metres of ment has attempted to simulate ice-wedge casting, as permafrost are described by Harris et al. (2001a, b). 807 3 EXPERIMENTAL METHODOLOGY Model ice wedges were 150 mm high and tapered uniformly downward from a maximum true width of The present experiments were carried out in the 50 mm. During thaw in the centrifuge at 30 gravities, Cardiff Geotechnical Centrifuge Facility. This com- these were equivalent to prototype-scale wedges 4.5 m prises a beam centrifuge of radius 2.8 m capable of high and р1.5 m wide. Six models were constructed to accelerating a model package with a mass of up to 1/30 scale (Table 1). Host sediments comprised medium 1000 kg at an acceleration of 100 gravities. The test sand (models 1 and 2), natural loessic silt (models 3 package is contained within a strongbox of external and 4) and silt-clay mixtures (models 5 and 6). dimensions ϳ750 mm ϫ 550 mm ϫ 500 mm built of Gravimetric moisture contents ranged from ϳ15% steel with Perspex sides. (model 1) to 60% (model 6). Models 3 and 5 had mois- Six ice-wedge models were constructed in a ture contents between the Plastic Limit and Liquid polypropylene test box of internal dimensions 750 mm Limit, whereas in models 4 and 6, moisture contents long by 450 mm wide by 500 mm deep that fitted exceeded the Liquid Limit. closely inside the centrifuge strongbox. Freezing of the Centrifuge tests lasted between approximately model soil took place within a chest freezer, and the 8 hours (model 1) and 22.5 hours (model 6). Soil models were thawed from the surface downwards in drainage was allowed during thaw, except in model 2. the geotechnical centrifuge under an acceleration of Temperature and pore-water pressure were recorded 30 gravities (g). Thus, dimensional scaling during at 10-second intervals on a data logger. Time-lapse thaw between model and prototype was ϫ30. photographs were taken through the clear Perspex A layer of sand ϳ20 mm thick formed the base of front of the strongbox, and videos through the front each model. Above it were laid successive layers of and top of the model in order to document the forma- soil ϳ20–35 mm thick. The top of each layer was tion of ice-wedge casts. After complete thawing of the carefully flattened and the layer was frozen before the wedge and host soil, the models were allowed to drain next was added. Marker layers 2–3 mm thick and of for 2–4 weeks before they were vertically sectioned different colour and/or texture to the soil layers were and structures within them were measured, sketched placed between them in order to highlight any defor- and photographed. mation structures formed during thaw. The soil layers and markers were laid on both sides of an aluminium mould with external dimensions identical to the inter- nal dimensions of a similar mould used to form the model ice wedges. After the uppermost soil layer had been laid and frozen, the mould was removed from the soil, leaving a wedge-shaped trough into which a previously-frozen model ice wedge was inserted. Any gaps between the sides of the wedge and trough, usually no more than 1 to 2 mm wide, were filled with chilled water and frozen prior to commencing thaw of the ice wedge. Finally, a model active layer 25 mm thick was placed above the top of the wedge and moistened with warm Figure 1. Vertical section through ice-wedge model 6, water in order to expedite thaw of the model. showing location of pore-water pressure transducers and Instrumentation buried in the soil during model thermocouples adjacent to the ice wedge, and of marker horizons in the host silt-clay soil. construction comprised six miniature pore pressure transducers (Druck PDCR-81, 350 mbar), and up to 14 Type K thermocouples. The transducers were placed at 50 mm and 100 mm distances from the edge Table 1. Ice-wedge model parameters. of the ice wedge in order to determine if (1) excess Moisture pore pressures resulted during thaw of the ice wedge Model Grain size content* (%) Cover soil and host soil (2) whether these were associated with lateral or vertical hydraulic gradients. Monitoring of 1 medium sand 15 sand pore pressure also facilitates interpretation of soil 2 medium sand 20 sand rheology and hence casting mechanisms during thaw. 3 Pegwell silt 40 Prawle silt 4 Pegwell silt 20 Prawle silt The thermocouples permitted monitoring of the rate † † of thaw and the pattern of isotherms adjacent to the 5 2/3 silt, 1/3 clay 30 2/3 silt, 1/3 clay 6 2/3 silt, 1/3 clay† 60 2/3 silt, 1/3 clay† thawing ice wedge. The positioning of transducers and thermocouples in model 6 is shown in Figure 1. *Approximate gravimetric moisture content. †Kaolinite. 808 4 RESULTS 4.2 Pore pressures To illustrate the results of these casting experiments, we Pore pressures generated during thaw consolidation present some data on temperature, pore pressures and are illustrated in Figure 3 for transducers located at cast geometry from model 6.
Load more

Recommended publications
  • Chapter 7 Seasonal Snow Cover, Ice and Permafrost
    I Chapter 7 Seasonal snow cover, ice and permafrost Co-Chairmen: R.B. Street, Canada P.I. Melnikov, USSR Expert contributors: D. Riseborough (Canada); O. Anisimov (USSR); Cheng Guodong (China); V.J. Lunardini (USA); M. Gavrilova (USSR); E.A. Köster (The Netherlands); R.M. Koerner (Canada); M.F. Meier (USA); M. Smith (Canada); H. Baker (Canada); N.A. Grave (USSR); CM. Clapperton (UK); M. Brugman (Canada); S.M. Hodge (USA); L. Menchaca (Mexico); A.S. Judge (Canada); P.G. Quilty (Australia); R.Hansson (Norway); J.A. Heginbottom (Canada); H. Keys (New Zealand); D.A. Etkin (Canada); F.E. Nelson (USA); D.M. Barnett (Canada); B. Fitzharris (New Zealand); I.M. Whillans (USA); A.A. Velichko (USSR); R. Haugen (USA); F. Sayles (USA); Contents 1 Introduction 7-1 2 Environmental impacts 7-2 2.1 Seasonal snow cover 7-2 2.2 Ice sheets and glaciers 7-4 2.3 Permafrost 7-7 2.3.1 Nature, extent and stability of permafrost 7-7 2.3.2 Responses of permafrost to climatic changes 7-10 2.3.2.1 Changes in permafrost distribution 7-12 2.3.2.2 Implications of permafrost degradation 7-14 2.3.3 Gas hydrates and methane 7-15 2.4 Seasonally frozen ground 7-16 3 Socioeconomic consequences 7-16 3.1 Seasonal snow cover 7-16 3.2 Glaciers and ice sheets 7-17 3.3 Permafrost 7-18 3.4 Seasonally frozen ground 7-22 4 Future deliberations 7-22 Tables Table 7.1 Relative extent of terrestrial areas of seasonal snow cover, ice and permafrost (after Washburn, 1980a and Rott, 1983) 7-2 Table 7.2 Characteristics of the Greenland and Antarctic ice sheets (based on Oerlemans and van der Veen, 1984) 7-5 Table 7.3 Effect of terrestrial ice sheets on sea-level, adapted from Workshop on Glaciers, Ice Sheets and Sea Level: Effect of a COylnduced Climatic Change.
    [Show full text]
  • 180 in Siberian Syngenetic Ice-Wedge Complexes
    14C AND 180 IN SIBERIAN SYNGENETIC ICE-WEDGE COMPLEXES YURIJ K. VASIL'CHUK Department of Cryolithology and Glaciology and Laboratory of Regional Engineering Geology, Moscow State University, Vorob'yovy Gory, 119899 Moscow, Russia and The Theoretical Problems Department, Russian Academy of Sciences, Denezhnyi pereulok, 12, 121002 Moscow, Russia and ALLA C. VASIL'CHUK Institute of Cell Biophysics, The Russian Academy of Sciences, 142292, Pushchino Moscow Region, Russia ABSTRACT. We discuss the possibility of dating ice wedges by the radiocarbon method. We show as an example the Seyaha, Kular and Zelyony Mys ice wedge complexes, and investigated various organic materials from permafrost sediments. We show that the reliability of dating 180 variations from ice wedges can be evaluated by comparison of different organic mate- rials from host sediments in the ice wedge cross sections. INTRODUCTION Permafrost covers 60% of the Russian territory and a large part of North America. During the glacial period, almost all of Europe was also covered by permafrost, with temperatures close to the present ones in the north of western Siberia and Yakutia (Vasil'chuk and Vasil'chuk 1995a). That permafrost melted not more than 10,000 yr ago. This enables radiocarbon dating of paleopermafrost sediments from Europe and North America. Hydrogen and oxygen stable isotopes in syngenetic ice wedges of northern Eurasia and North America permafrost zones yield paleoclimatic parameters, such as paleotemperature. The oxygen isotope composition of a recently formed syngenetic ice wedge together with present winter temper- atures of surface air (Vasil'chuk 1991) made it possible to use stable isotope variations in ancient syngenetic ice wedges as a quantitative paleotemperature indicator (to make sure that the same dependence took place in the past).
    [Show full text]
  • Periglacial Processes, Features & Landscape Development 3.1.4.3/4
    Periglacial processes, features & landscape development 3.1.4.3/4 Glacial Systems and landscapes What you need to know Where periglacial landscapes are found and what their key characteristics are The range of processes operating in a periglacial landscape How a range of periglacial landforms develop and what their characteristics are The relationship between process, time, landforms and landscapes in periglacial settings Introduction A periglacial environment used to refer to places which were near to or at the edge of ice sheets and glaciers. However, this has now been changed and refers to areas with permafrost that also experience a seasonal change in temperature, occasionally rising above 0 degrees Celsius. But they are characterised by permanently low temperatures. Location of periglacial areas Due to periglacial environments now referring to places with permafrost as well as edges of glaciers, this can account for one third of the Earth’s surface. Far northern and southern hemisphere regions are classed as containing periglacial areas, particularly in the countries of Canada, USA (Alaska) and Russia. Permafrost is where the soil, rock and moisture content below the surface remains permanently frozen throughout the entire year. It can be subdivided into the following: • Continuous (unbroken stretches of permafrost) • extensive discontinuous (predominantly permafrost with localised melts) • sporadic discontinuous (largely thawed ground with permafrost zones) • isolated (discrete pockets of permafrost) • subsea (permafrost occupying sea bed) Whilst permafrost is not needed in the development of all periglacial landforms, most periglacial regions have permafrost beneath them and it can influence the processes that create the landforms. Many locations within SAMPLEextensive discontinuous and sporadic discontinuous permafrost will thaw in the summer months.
    [Show full text]
  • 773593683.Pdf
    LAKE AREA CHANGE IN ALASKAN NATIONAL WILDLIFE REFUGES: MAGNITUDE, MECHANISMS, AND HETEROGENEITY A DISSERTATION Presented to the Faculty of the University of Alaska Fairbanks In Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY By Jennifer Roach, B.S. Fairbanks, Alaska December 2011 iii Abstract The objective of this dissertation was to estimate the magnitude and mechanisms of lake area change in Alaskan National Wildlife Refuges. An efficient and objective approach to classifying lake area from Landsat imagery was developed, tested, and used to estimate lake area trends at multiple spatial and temporal scales for ~23,000 lakes in ten study areas. Seven study areas had long-term declines in lake area and five study areas had recent declines. The mean rate of change across study areas was -1.07% per year for the long-term records and -0.80% per year for the recent records. The presence of net declines in lake area suggests that, while there was substantial among-lake heterogeneity in trends at scales of 3-22 km a dynamic equilibrium in lake area may not be present. Net declines in lake area are consistent with increases in length of the unfrozen season, evapotranspiration, and vegetation expansion. A field comparison of paired decreasing and non-decreasing lakes identified terrestrialization (i.e., expansion of floating mats into open water with a potential trajectory towards peatland development) as the mechanism for lake area reduction in shallow lakes and thermokarst as the mechanism for non-decreasing lake area in deeper lakes. Consistent with this, study areas with non-decreasing trends tended to be associated with fine-grained soils that tend to be more susceptible to thermokarst due to their higher ice content and a larger percentage of lakes in zones with thermokarst features compared to study areas with decreasing trends.
    [Show full text]
  • Organic Carbon Characteristics in Ice-Rich Permafrost in Alas and Yedoma Deposits, Central Yakutia, Siberia” by Torben Windirsch Et Al
    Biogeosciences Discuss., https://doi.org/10.5194/bg-2019-470-RC1, 2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Interactive comment on “Organic Carbon Characteristics in Ice-rich Permafrost in Alas and Yedoma Deposits, Central Yakutia, Siberia” by Torben Windirsch et al. Anonymous Referee #1 Received and published: 27 January 2020 The paper “Organic Carbon Characteristics in Ice-rich Permafrost in Alas and Yedoma Deposits, Central Yakutia, Siberia” by Windirsch et al. reports detailed analyses on carbon and ice contents, stable water isotopes, soil grain size distribution, and age estimates for two long ground profiles in the Central Yakutia, Russia. The presented materials are rare and highly valuable to understand landscape development and con- tents in the permafrost of the Eastern Siberia. Although I expect this paper to be finally published in Biogeosciece, the authors have not fully utilized, described, and discussed the data presented. The importance of this paper is the rareness of the sample core. I encourage the authors to enrich their descriptions about each core unit as a valuable drilling log of a permafrost region. Some portions in Discussion are C1 not logically constructed. For the main datasets of stable water isotopes and carbon parameters, a more in-depth and quantitative discussion is anticipated. Although the authors want to focus on the organic carbon characteristics as indicated in the title, more comprehensive discussion and interpretation must be done using available water geochemistry, cryostratigraphy, grain size distribution, magnetic susceptibility, etc. The usage of references or previous studies is poor and is often not clear or inappropriate.
    [Show full text]
  • Permafrost Conditions Near Shorelines of Oriented Lakes in Old Crow Flats, Yukon Territory
    Permafrost conditions near shorelines of oriented lakes in Old Crow Flats, Yukon Territory P. Roy-Léveillée & C. R. Burn Department of Geography and Environmental Studies, Carleton University, Ottawa, Ontario, Canada. ABSTRACT Old Crow Flats is a 4300 km 2 plain in the continuous permafrost of Northern Yukon. It contains over 2500 thermokarst lakes, many of which have rectilinear shorelines and tend to be oriented either NE-SW or NW-SE. Previous explanations of the shape and orientation of the lakes focussed on the underlying geological structure and the propagation of faults through the sediments to cause the alignment of the lakeshores. Permafrost conditions and shore erosion mechanisms observed at forested and tundra sites suggest that wind and patterns of ice-wedge development may be contributing to the occurrence of rectilinear shorelines in the open tundra of Old Crow Flats. RÉSUMÉ La plaine de Old Crow est située dans la zone de pergélisol continu, au nord du Yukon. Le nombre de lacs thermokarstiques situés sur cette plaine excède 2500, et plusieurs de ceux-ci ont des berges rectilignes et ont tendance à être orientés soit nord-est-sud-ouest ou nord-ouest-sud-est. Jusqu’à maitenant, les explications avancées pour les lacs d’Old Crow misent sur la structure geologique sous-jacente et la propagation de failles à travers les sédiments forcant l’alignment des berges des lacs. Les conditions thermiques du pergélisol et les mecanismes d’érosion des berges observés dans la tundra et la forêt de la plaine de Old Crow suggèrent qu’en fait le vent et la distribution des coins de glace jouent un rôle important pour le dévelopment de berges rectilignes dans la tundra sur la plaine d’Old Crow.
    [Show full text]
  • Ice Wedge Degradation and CO2 and CH4 Emissions in the Tuktoyaktuk Coastlands, NT
    Arctic Science Ice wedge degradation and CO2 and CH4 emissions in the Tuktoyaktuk Coastlands, NT Journal: Arctic Science Manuscript ID AS-2016-0011.R2 Manuscript Type: Article Date Submitted by the Author: 11-Aug-2017 Complete List of Authors: Martin, Abra; University of Victoria, School of Environmental Studies Lantz, Trevor; University of Victoria, Environmental Studies Humphreys, Elyn; Carleton University , Geography and Environmental Studies Draft Keyword: carbon dioxide, methane, permafrost, thermokarst, ice wedge Is the invited manuscript for consideration in a Special N/A Issue?: https://mc06.manuscriptcentral.com/asopen-pubs Page 1 of 37 Arctic Science Ice wedge degradation and CO 2 and CH 4 emissions in the Tuktoyaktuk Coastlands, NT. Abra F. Martin 1, Trevor C. Lantz 1,3 and Elyn R. Humphreys 2 1. School of Environmental Studies, University of Victoria 2. Geography and Environmental Studies, Carleton University 3. Author for Correspondence: [email protected] 4. AFM and TCL conceived the study; AFM and TCL collected the data; AFM analyzed the data; AFM,Draft TCL and ERH wrote the manuscript. https://mc06.manuscriptcentral.com/asopen-pubs Arctic Science Page 2 of 37 1 Abstract 2 3 Increases in ground temperature make soil organic carbon in permafrost 4 environments highly vulnerable to release to the atmosphere. High-centred polygonal 5 terrain is a form of patterned ground that may include areas that act as large sources of 6 carbon to the atmosphere because thawing ice-wedges can result in increased ground 7 temperatures, soil moisture and thaw depth. To evaluate the effect of ice wedge 8 degradation on carbon flux, carbon emissions were characterized at two polygonal 9 peatlands in the Tuktoyaktuk Coastlands in northern Canada.
    [Show full text]
  • New Ground Ice Maps for Canada Using a Paleogeographic Modelling Approach
    New ground ice maps for Canada using a paleogeographic modelling approach 5 H. Brendan O’Neill1, Stephen A. Wolfe1, Caroline Duchesne1 1Geological Survey of Canada, Natural Resources Canada, 601 Booth St. Ottawa, Canada Correspondence to: H. Brendan O’Neill: [email protected] The works published in this journal are distributed under the Creative Commons Attribution 4.0 License. This licence does not affect the Crown copyright work, which is re-usable under the Open Government Licence (OGL). The Creative Commons 10 Attribution 4.0 License and the OGL are interoperable and do not conflict with, reduce or limit each other. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2018 1 Abstract Ground ice melt caused by climate-induced permafrost degradation may trigger significant ecological change, damage infrastructure, and alter biogeochemical cycles. The fundamental ground ice mapping for Canada is now >20 years old, and does not include significant new insights gained from recent field and remote sensing based studies. New modelling 5 incorporating paleogeography is presented in this paper to depict the distribution of three ground ice types (massive ice and icy sediments, segregated ice, and wedge ice) in northern Canada. The modelling uses an expert-system approach in a geographic information system (GIS), founded in conceptual principles gained from empirically-based research, to predict ground ice abundance in near-surface permafrost. Datasets of surficial geology, deglaciation, paleovegetation, glacial lake and marine limits, and modern permafrost distribution allow representations in the models of paleoclimatic shifts, tree line 10 migration, marine and glacial lake inundation, and terrestrial emergence, and their effect on ground ice abundance.
    [Show full text]
  • Palsas and Lithalsas
    Published in : Treatise on Geomorphology (2013), vol. 8, pp. 223–237 DOI: http://dx.doi.org/10.1016/B978-0-12-374739-6.00210-4 Status : Postprint (Author’s version) PALSAS AND LITHALSAS GLOSSARY Active layer: The top layer of ground subject to annual thawing and freezing in areas underlain by permafrost (Glossary of permafrost and related ground-ice terms, Technical memorandum, 142, National Research Council, Canada (1988)). Aggradational ice: Segregation ice formed in the lower part of the active layer and incorporated into the permafrost. Cryogenic structures: Distinct soil micromorphology resulting from the effects of freezing and mainly from the formation of segregation ice in the ground. Cryosuction: A suction of water in the ground to the freezing front in fine-grained material. Frost thrusting: Lateral movement of mineral soil in relation to freezing of water in the soil. Gelifluction: The slow downslope flow of unfrozen earth materials on a frozen substrate. Little ice age: A period of cooling and glacier expansion that covers a period extending from the sixteenth to the nineteenth centuries. Mud boils or frost boils: Small mounds of soil material formed by frost action and corresponding in section to cryoturbations. ABSTRACT Palsas and Iithalsas are mounds that contain lenses of segregation ice. They are islands of permafrost. These two kinds of mounds are very similar in shape, size, and origin. However, the palsas have a cover of peat which does not exist in Iithalsas. The formation of ice in the core of these mounds requires material in which capillary water undergoes slow freezing. The remnants of Iithalsas are depressions surrounded by ramparts, which does not exist after the melting of palsas.
    [Show full text]
  • A Review of Published Literature on the Effects of Permafrost on the Hydrogeochemistry of Bedrock
    FI0000082 POSIVA 2000-09 A review of published literature on the effects of permafrost on the hydrogeochemistry of bedrock M. Gascoyne Gascoyne GeoProjects Inc. Ca nada June 2000 POSIVA OY Toolonkatu 4. FIN-00100 HELSINKI, FIMLAND Phone (09) 2280 30 (nat.), ( + 358-9-) 2280 30 (int.) Fax (09) 2280 3719 (nat.), ( + 358-9-) 2280 3719 (int.) ISBN 951-652-095-2 ISSN 1239-3096 The conclusions and viewpoints presented in the report are those of author(s) and do not necessarily coincide with those of Posiva. Please be aware that all of the Missing Pages in this document were originally blank pages Posiva-raportti - Posiva Report Rapor1intunnu s -Report code POSIVA 2000-09 P0Siva °y lulkaisuaika - Date T66!6nkatu 4, FIN-00100 HELSINKI, FINLAND JuiKaisuaiKa uate Puh. (09) 2280 30 - Int. Tel. +358 9 2280 30 June 2000 Tekija(t) - Author(s) Toimeksiantaja(t) - Commissioned by M. Gascoyne Posiva Oy Gascoyne GeoProjects Inc. NimeklT- Title A REVIEW OF PUBLISHED LITERATURE ON THE EFFECTS OF PERMAFROST ON THE HYDROGEOCHEMISTRY OF BEDROCK Tiivistelma -Abstract Salt-rejection into the aqueous phase from permafrost growth ('aggradation') during the onset of cold-climate conditions in the Pleistocene period is a mechanism that could account for the presence of saline groundwaters in the Fennoscandian Shield. This report describes the results of a review of scientific literature on the subject of permafrost, to search for and evaluate information which may indicate whether this mechanism is feasible for sites such as Olkiluoto and Aspo on the Baltic Sea coast. The geomorphological characteristics of permafrost (such as development of patterned ground, ice wedging, pingo growth) have been studied in detail in the literature and provide an understanding of the effects of pore water expulsion and saline water formation.
    [Show full text]
  • Identifying Drivers Behind Spatial Variability of Methane Concentrations in East Siberian Ponds
    ORIGINAL RESEARCH published: 26 March 2021 doi: 10.3389/feart.2021.617662 Identifying Drivers Behind Spatial Variability of Methane Concentrations in East Siberian Ponds Zoé Rehder 1,2*, Anna Zaplavnova 3,4 and Lars Kutzbach 5 1 Department of the Land in the Earth System, Max Planck Institute for Meteorology, Hamburg, Germany, 2 International Max Planck Research School on Earth System Modeling, Hamburg, Germany, 3 Department of Geology and Geophysics, Novosibirsk State University, Novosibirsk, Russia, 4 The Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia, 5 Institute of Soil Science, Center for Earth System Research and Sustainability (CEN), Universität Hamburg, Hamburg, Germany Waterbody methane emissions per area are negatively correlated with the size of the emitting waterbody. Thus, ponds, defined here as having an area smaller than 8 · 104 m2, contribute out of proportion to the aquatic methane budget compared to the total area they cover and compared to other waterbodies. However, methane concentrations in and methane emissions from ponds show more spatial variability than Edited by: Annalea Lohila, larger waterbodies. We need to better understand this variability to improve upscaling University of Helsinki, Finland estimates of freshwater methane emissions. In this regard, the Arctic permafrost Reviewed by: landscape is an important region, which, besides carbon-rich soils, features a high Ronny Lauerwald, Université Paris-Saclay, France pond density and is exposed to above-average climatic warming. We studied 41 Sophia Burke, polygonal-tundra ponds in the Lena River Delta, northeast Siberia. We collected water University of New Hampshire, samples at different locations and depths in each pond and determined methane United States concentrations using gas chromatography.
    [Show full text]
  • Other Periglacial Landforms Ice Wedges & Ice-Wedge Polygons
    Other periglacial landforms Ice wedges & ice-wedge polygons when thermal tension exceeds the strength of surface materials, frost cracking occurs & fractures penetrate into the active layer and the upper portion of the permafrost – start only mm wide but go down several meters water melts in active zone in spring, flows into crack, freezes in permafrost & grows with time to form ice wedge or, in dry permafrost, sand wedge ice wedges connect in polygonal pattern with diameters of meters to > 100 m; have some with ridges at boundary, others with troughs active ice wedges are limited to continuous permafrost; when they melt, surrounding sediment collapses into space, & creates ice-wedge cast 454 lecture 11 Patterned ground in northern Alaska 454 lecture 11 White Mountains, AZ 454 lecture 11 Hummocky terrain in northern Alaska 454 lecture 11 Greenland 454 lecture 11 Pingos large, ice-cored, dome-like features best developed in continuous permafrost few meters to > 100 m high & up to 1200 m basal diameter oval or circular in plan form in fields closed-system pingos develop in level, poorly-drained shallow lake basins – draining of lake allows permafrost table to rise to level of former lake floor – water trapped in saturated soil is displaced upward by cryostatic pressure (pressure from ice formation) until it freezes & becomes the core of the pingo open-system pingos develop on slopes where free water under artesian pressure is injected into the site of the pingo – as water approaches the surface, it freezes – more common in discontinuous permafrost pingos grow at 5 cm to > 1 m/yr 454 lecture 11 270 m pingos in the delta of the Mackenzie River, Canada 454 lecture 11 pingo on the coastal plain near Kotzebue, Alaska 454 lecture 11.
    [Show full text]