DOCSLIB.ORG

Érosion Du Pergélisol, Transport Fluvial Et Sédimentation Marine, Côte Est De La Baie D’Hudson, Nunavik, Canada

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Érosion Du Pergélisol, Transport Fluvial Et Sédimentation Marine, Côte Est De La Baie D’Hudson, Nunavik, Canada Érosion du pergélisol, transport fluvial et sédimentation marine, côte est de la baie d’Hudson, Nunavik, Canada Thèse Maxime Jolivel Doctorat en sciences géographiques Philosophiae Doctor (Ph.D.) Québec, Canada © Maxime Jolivel, 2014 ii Résumé Cette thèse présente une étude du système érosion-transport-sédimentation en milieu de thermokarst dans un contexte de réchauffement climatique. La zone d’étude comprend le bassin versant de la rivière Sheldrake, 5 km au nord du village Umiujaq au Nunavik, ainsi qu’une zone de 15 km2 au large de son embouchure, dans le Passage de Nastapoka, en baie d’Hudson. Trois axes majeurs sont considérés: 1- l’étude des conditions de pergélisol et l’estimation quantitative des masses et volumes de sédiments et de carbone érodés à l’échelle du bassin versant ; 2- la mesure du régime hydrologique et sédimentaire du principal vecteur de transport, la rivière Sheldrake ; 3- la bathymétrie, la sédimentologie et la mesure des apports sédimentaires et organiques dans le milieu marin côtier au large de l’embouchure de la rivière. Dans le bassin versant de la rivière Sheldrake, le pergélisol s’est considérablement dégradé au cours des 50 dernières années, particulièrement dans la toundra forestière. La subsidence des lithalses, des palses, des plateaux de pergélisol et des plateaux palsiques engendre la formation de mares de thermokarst. De nombreux glissements de terrain et des ravins d’érosion sont également actifs et favorisent le rejet de sédiments dans le réseau fluvial. Avec la dégradation du pergélisol, la connectivité hydrologique augmente, ce qui facilite l’évacuation des sédiments et du carbone via le cours d’eau principal. Dans cet environnement thermokarstique, la charge sédimentaire fluviale en suspension est plus importante en été alors que les températures élevées de l’air commandent le dégel des sols, favorisant l’activation des ostioles et le déclenchement des glissements de terrain. Les pluies estivales permettent le transport et l’évacuation des sédiments en baie d’Hudson. Parvenus en mer, les sédiments et le carbone transportés en suspension subissent une forte dispersion à cause de l’intensité des courants marins du Passage de Nastapoka. Il en résulte l’absence d’une augmentation mesurable du taux de sédimentation. En revanche, la composition isotopique du carbone sédimentaire montre que la fraction terrigène a augmenté depuis le Petit Âge Glaciaire et que ce phénomène s’est considérablement iii accéléré vers la fin du 20ème siècle. Il est suggéré que la dégradation du pergélisol contribue à cette augmentation, quoique ce ne soit pas le seul facteur qu’on puisse invoquer. iv Abstract This thesis studies the system erosion-transport-sedimentation in a thermokastic area, in a context of warming climate. The study area encompasses the catchment of the Sheldrake River, 5 km north of the village Umiujaq, Nunavik, and a 15 km2 area off its mouth, in the Nastapoka Sound, in Hudson Bay. Three main axes are considered: 1- study of permafrost conditions and quantitative estimate of the volumes and masses of eroded sediment and organic carbon at the scale of the catchment; 2- measurements of the hydrological and sedimentary regime of the main vector of transport, the Sheldrake River; 3- bathymetry, sedimentology and measurements of mineral and organic inputs in the coastal marine environment, off the river mouth. In the Sheldrake River catchment, permafrost has considerably degraded during the last 50 years, particularly in the forested tundra. Subsidence of lithalsas, palsas, permafrost plateaus and peat plateaus leads to the formation of thermokarst ponds. Many landslides and erosion gullies are also active and favor inputs of sediments in the fluvial network. Because of permafrost decay, hydrological connectivity increases, facilitating evacuation of sediment and carbon through the river. In this thermokarstic environment, the fluvial sedimentary load in suspension is more important during summer when high air temperatures provoke soils thawing, favoring frostboils activation and triggering of landslides. Summer rainfalls allow sediment transport and evacuation in Hudson Bay. Once in the sea, the sediments and carbon in suspension are dispersed because of the intensity of the marine currents in the Nastapoka Sounds. This results in an absence of a measurable increase of sedimentation rates. However, the isotopic composition of sedimentary carbon shows that the terrestrial fraction has increased since the Little Ice Age and that this trend has significantly accelerated since the end of the 20th century. It is suggested that permafrost decay contributes to this increase, although it is not the only proposed source. v vi Table des matières Résumé ................................................................................................................................. iii Abstract .................................................................................................................................. v Table des matières ............................................................................................................. vii Liste des tableaux ................................................................................................................. xi Liste des figures ................................................................................................................. xiii Remerciements .................................................................................................................... xv Avant-propos .................................................................................................................... xvii CHAPITRE 1 - Introduction générale ................................................................................ 1 1.1 Problématique générale .................................................................................................. 1 1.2 Objectifs généraux .......................................................................................................... 2 1.3 Objectifs spécifiques ....................................................................................................... 3 1.4 Région d’étude ................................................................................................................. 4 1.5 Méthodologie ................................................................................................................. 10 1.5.1 Cartographie de la distribution et de la dégradation du pergélisol et estimation quantitative des masses et volumes de sédiments et de carbone érodés ............................... 10 1.5.2 Mesures du régime hydrologique et sédimentaire de la rivière Sheldrake .................. 11 1.5.3 Bathymétrie, sédimentologie et mesure des apports sédimentaires et organiques dans le Passage de Nastapoka au large de l’embouchure de la rivière Sheldrake ....................... 11 1.6 Structure de la thèse ..................................................................................................... 12 1.6.1 Chapitre 2 ..................................................................................................................... 12 1.6.2 Chapitre 3 ..................................................................................................................... 12 1.6.3 Chapitre 4 ..................................................................................................................... 13 1.7 Références ....................................................................................................................... 13 vii CHAPITRE 2 - Thermokarst and export of sediment and organic carbon in the Sheldrake River watershed, Nunavik, Canada. .............................................................. 17 2.1 Résumé .......................................................................................................................... 17 2.2 Abstract ......................................................................................................................... 18 2.3 Introduction .................................................................................................................. 18 2.4 Study area and regional setting................................................................................... 20 2.5 Permafrost degradation processes .............................................................................. 25 2.6 Methodology ................................................................................................................. 28 2.6.1 Permafrost and thermokarst mapping ......................................................................... 28 2.6.2 Landslides identification and sediment and organic matter released .......................... 31 2.6.3 Estimation of organic carbon and sediment fluxes from connected thermokarst ponds .............................................................................................................................................. 32 2.6.4 Hydrological connectivity ........................................................................................... 36 2.7 Results ........................................................................................................................... 36 2.7.1 Spatiotemporal evolution of permafrost ...................................................................... 36 2.7.2 Activity of landslides, active layer failures and gullies between 1957 and 2009 ....... 41 2.7.3 Hydrological connectivity ..........................................................................................
Load more

Recommended publications
  • GEOMORPHOLOGIE 4-2008 BIS:Maquette Geomorpho
    Géomorphologie : relief, processus, environnement, 2008, n° 4, p. 223-234 Paraglacial and paraperiglacial landsystems: concepts, temporal scales and spatial distribution Géosystèmes paraglaciaire et parapériglaciaire : concepts, échelles temporelles et distribution spatiale Denis Mercier* Abstract The Pleistocene Earth history has been characterized by major climatic fluctuations. During glacial periods, ice may have covered around 30 per cent of the Earth surface compared to approximately 10 per cent nowadays. With global change, polar environments and other montainous glacial environments of the world are presently undergoing the most important changes since the end of the Last Glacial Maximum and are experiencing paraglacial and paraperiglacial geomorphological readjustments. Paraglacial and para- periglacial landsystems consist of several subsystems including gravitational, fluvial, coastal, aeolian and lacustrine environments. Paraglacial and paraperiglacial landsystems can be analysed as open and complex landsystems characterized by energy, water and sed- iment fluxes and exchange with surrounding environments, especially with glacial and periglacial landsystems as inputs. Those cascading landsystems are likely to react to climate change because they rely on an ice-cold water stock (glacier and permafrost) that developed during a previous cold sequence (glaciation). The response of paraglacial and paraperiglacial systems to climatic forcing takes place over a long time span ranging from an immediate reaction to several millennia. The spatial limits of paraglacial and para- periglacial landsystems are inherently dependant on the time scale over which the system is analyzed. During the Pleistocene, glaciations widely affected the high latitudes and the high altitudes of the Earth and were followed by inherited paraglacial sequences. Glacier forelands in Arctic and alpine areas experience paraglacial processes with the present warming.
    [Show full text]
  • Changes in Peat Chemistry Associated with Permafrost Thaw Increase Greenhouse Gas Production
    Changes in peat chemistry associated with permafrost thaw increase greenhouse gas production Suzanne B. Hodgkinsa,1, Malak M. Tfailya, Carmody K. McCalleyb, Tyler A. Loganc, Patrick M. Crilld, Scott R. Saleskab, Virginia I. Riche, and Jeffrey P. Chantona,1 aDepartment of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306; bDepartment of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721; cAbisko Scientific Research Station, Swedish Polar Research Secretariat, SE-981 07 Abisko, Sweden; dDepartment of Geological Sciences, Stockholm University, SE-106 91 Stockholm, Sweden; and eDepartment of Soil, Water and Environmental Science, University of Arizona, Tucson, AZ 85721 Edited by Nigel Roulet, McGill University, Montreal, Canada, and accepted by the Editorial Board March 7, 2014 (received for review August 1, 2013) 13 Carbon release due to permafrost thaw represents a potentially during CH4 production (10–12, 16, 17), δ CCH4 also depends on 13 major positive climate change feedback. The magnitude of carbon δ CCO2,soweusethemorerobustparameterαC (10) to repre- loss and the proportion lost as methane (CH4) vs. carbon dioxide sent the isotopic separation between CH4 and CO2.Despitethe ’ (CO2) depend on factors including temperature, mobilization of two production pathways stoichiometric equivalence (17), they previously frozen carbon, hydrology, and changes in organic mat- are governed by different environmental controls (18). Dis- ter chemistry associated with environmental responses to thaw. tinguishing these controls and further mapping them is therefore While the first three of these effects are relatively well under- essential for predicting future changes in CH4 formation under stood, the effect of organic matter chemistry remains largely un- changing environmental conditions.
    [Show full text]
  • Geophysical Mapping of Palsa Peatland Permafrost
    The Cryosphere, 9, 465–478, 2015 www.the-cryosphere.net/9/465/2015/ doi:10.5194/tc-9-465-2015 © Author(s) 2015. CC Attribution 3.0 License. Geophysical mapping of palsa peatland permafrost Y. Sjöberg1, P. Marklund2, R. Pettersson2, and S. W. Lyon1 1Department of Physical Geography and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden 2Department of Earth Sciences, Uppsala University, Uppsala, Sweden Correspondence to: Y. Sjöberg ([email protected]) Received: 15 August 2014 – Published in The Cryosphere Discuss.: 13 October 2014 Revised: 3 February 2015 – Accepted: 10 February 2015 – Published: 4 March 2015 Abstract. Permafrost peatlands are hydrological and bio- ing in these landscapes are influenced by several factors other geochemical hotspots in the discontinuous permafrost zone. than climate, including hydrological, geological, morpholog- Non-intrusive geophysical methods offer a possibility to ical, and erosional processes that often combine in complex map current permafrost spatial distributions in these envi- interactions (e.g., McKenzie and Voss, 2013; Painter et al., ronments. In this study, we estimate the depths to the per- 2013; Zuidhoff, 2002). Due to these interactions, peatlands mafrost table and base across a peatland in northern Swe- are often dynamic with regards to their thermal structures and den, using ground penetrating radar and electrical resistivity extent, as the distribution of permafrost landforms (such as tomography. Seasonal thaw frost tables (at ∼ 0.5 m depth), dome-shaped palsas and flat-topped peat plateaus) and talik taliks (2.1–6.7 m deep), and the permafrost base (at ∼ 16 m landforms (such as hollows, fens, and lakes) vary with cli- depth) could be detected.
    [Show full text]
  • Potential Effect of Climate Change on the Distribution of Palsa Mires in Subarctic Fennoscandia
    CLIMATE RESEARCH Vol. 32: 1–12, 2006 Published August 10 Clim Res Potential effect of climate change on the distribution of palsa mires in subarctic Fennoscandia Stefan Fronzek1,*, Miska Luoto2, Timothy R. Carter1 1Finnish Environment Institute, Box 140, 00251 Helsinki, Finland 2Thule Institute, University of Oulu, Box 7300, 90014 Oulu, Finland ABSTRACT: Palsa mires are northern mire complexes with permanently frozen peat hummocks, located at the outer limit of the permafrost zone. Palsa mires have high conservation status, being characterized by a rich diversity of bird species and unique geomorphological processes. They are currently degrading throughout their distributional range, probably because of regional climatic warming. Distributions of palsas in Fennoscandia were modelled using 5 climate envelope tech- niques (generalized linear modelling, generalized additive modelling, classification tree analysis, artificial neural networks and multiple adaptive regression splines). The models were studied with respect to their sensitivity to altered climate. Climate change scenarios were applied to assess possi- ble impacts on the palsa distribution during the 21st century. The models achieved a good to very good agreement with the observed palsa distribution and thus suggest a strong dependency on cli- mate. Even small increases of temperature (1°C) and precipitation (10%) resulted in considerable losses of areas suitable for palsa development. Of the 5 models tested, 3 predicted the total disappear- ance of regions suitable for palsa development with an increased mean annual temperature of 4°C. Under climate change scenarios based on 7 Atmosphere-Ocean General Circulation Models (AOGCMs) the models indicated that the degradation of palsas will proceed very quickly. All but one climate scenario resulted in the total disappearance of suitable regions for palsa development by the end of the 21st century.
    [Show full text]
  • Permafrost Soils and Carbon Cycling
    SOIL, 1, 147–171, 2015 www.soil-journal.net/1/147/2015/ doi:10.5194/soil-1-147-2015 SOIL © Author(s) 2015. CC Attribution 3.0 License. Permafrost soils and carbon cycling C. L. Ping1, J. D. Jastrow2, M. T. Jorgenson3, G. J. Michaelson1, and Y. L. Shur4 1Agricultural and Forestry Experiment Station, Palmer Research Center, University of Alaska Fairbanks, 1509 South Georgeson Road, Palmer, AK 99645, USA 2Biosciences Division, Argonne National Laboratory, Argonne, IL 60439, USA 3Alaska Ecoscience, Fairbanks, AK 99775, USA 4Department of Civil and Environmental Engineering, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Correspondence to: C. L. Ping ([email protected]) Received: 4 October 2014 – Published in SOIL Discuss.: 30 October 2014 Revised: – – Accepted: 24 December 2014 – Published: 5 February 2015 Abstract. Knowledge of soils in the permafrost region has advanced immensely in recent decades, despite the remoteness and inaccessibility of most of the region and the sampling limitations posed by the severe environ- ment. These efforts significantly increased estimates of the amount of organic carbon stored in permafrost-region soils and improved understanding of how pedogenic processes unique to permafrost environments built enor- mous organic carbon stocks during the Quaternary. This knowledge has also called attention to the importance of permafrost-affected soils to the global carbon cycle and the potential vulnerability of the region’s soil or- ganic carbon (SOC) stocks to changing climatic conditions. In this review, we briefly introduce the permafrost characteristics, ice structures, and cryopedogenic processes that shape the development of permafrost-affected soils, and discuss their effects on soil structures and on organic matter distributions within the soil profile.
    [Show full text]
  • D3.1 Palsa Mire
    European Red List of Habitats - Mires Habitat Group D3.1 Palsa mire Summary Palsa mire develops where thick peat is subject to sporadic permafrost in Iceland, northern Fennoscandia and arctic Russia where there is low precipitation and an annual mean temperature below -1oC. The permafrost dynamics produce a typical patterning with palsa mounds 2-4m (sometimes 7m) high elevated in central thicker areas by permafrost lenses, the carpet of Sphagnum peat limiting the penetration of thaw, and a perennially frozen core of peat, silt and ice lenses beneath. Pounikko hummock ridges can be found in marginal areas subject to seasonal freezing and there are plateau-wide palsas and pounu string mires in the arctic. Intact palsa mounds show a patterning of weakly minerotrophic vegetation with different assemblages of mosses, herbs and sub-shrubs on their tops and sides. Old palsa mounds can become dry and erosion may lead to melting and collapse. Complete melting leaves behind thermokarst ponds. Palsa mires have experienced substantial decline and deterioration in recent years and, although these changes are not yet dramatic, all estimations indicate high probability of collapse as a result of climatic warming. Climate change mitigation measures are decisive to prevent the collapse of this habitat type. Synthesis This habitat type is assessed as Critically Endangered (CR) under Criterion E as its probability of collapse within the next 50 years is estimated to be over 50% as a result of climate warming. This quantitative analysis has been performed by reviewing and analyzing published research articles, together with unpublished contributions from experts, by including probabilistic modeling of future trends and linear extrapolation of recent trends to support model predictions.
    [Show full text]
  • Radiocarbon Chronology of Holocene Palsa of Bol
    Yurij K.Vasil’chuk1*, Alla C.Vasil’chuk2, Högne Jungner3, Nadine A. Budantseva4, Julia N. Chizhova5 1 Department of Landscape Geochemistry and Soil Geography, Lomonosov Moscow State University, e-mail [email protected] & [email protected] *Corresponding author 2 Laboratory of Geoecology of the North, Lomonosov Moscow State University, e-mail [email protected] 3 Helsinki University, Helsinki, Finland, e-mail [email protected] 4 Department of Landscape Geochemistry and Soil Geography, Lomonosov Moscow GEOGRAPHY State University, e-mail [email protected] 5 Department of Landscape Geochemistry and Soil Geography, Lomonosov Moscow 38 State University, e-mail [email protected] RADIOCARBON CHRONOLOGY OF HOLOCENE PALSA OF BOL’SHEZEMEL’SKAYA TUNDRA IN RUSSIAN NORTH ABSTRACT. Six palsa mire in Usa River downwards from a summit. This evidenced valley and in Vorkuta area in North-eastern this frozen mound is real palsa, but not a part of European Russia were studied in residual form as a result of erosion. detail. In total 75 new 14C dates from different palsa sections were obtained. KEY WORDS: palsa; permafrost; mires; North- In palsa mire near Bugry Settlement 3.2 Eastern Europe; radiocarbon. m high palsa dated from 8.6 to 2.1 ka BP. The permafrost and palsa began 2.1 ka INTRODUCTION BP. In palsa mire near Usa Settlement low moor peat in 2 m high palsa dated 3690 Palsas represent one of the most BP, palsa began to heave at least 3700 widespread forms of permafrost terrain. BP. A low-moor peat of 2.5 m high palsa They are abundant in areas of discontinuous indicates the change in the hydrological- permafrost with mean annual temperatures mineral regime during 7.1 to 6.3 ka BP, close to the freezing point, although they heaving commenced 6 ka BP.
    [Show full text]
  • Changes in Snow, Ice and Permafrost Across Canada
    CHAPTER 5 Changes in Snow, Ice, and Permafrost Across Canada CANADA’S CHANGING CLIMATE REPORT CANADA’S CHANGING CLIMATE REPORT 195 Authors Chris Derksen, Environment and Climate Change Canada David Burgess, Natural Resources Canada Claude Duguay, University of Waterloo Stephen Howell, Environment and Climate Change Canada Lawrence Mudryk, Environment and Climate Change Canada Sharon Smith, Natural Resources Canada Chad Thackeray, University of California at Los Angeles Megan Kirchmeier-Young, Environment and Climate Change Canada Acknowledgements Recommended citation: Derksen, C., Burgess, D., Duguay, C., Howell, S., Mudryk, L., Smith, S., Thackeray, C. and Kirchmeier-Young, M. (2019): Changes in snow, ice, and permafrost across Canada; Chapter 5 in Can- ada’s Changing Climate Report, (ed.) E. Bush and D.S. Lemmen; Govern- ment of Canada, Ottawa, Ontario, p.194–260. CANADA’S CHANGING CLIMATE REPORT 196 Chapter Table Of Contents DEFINITIONS CHAPTER KEY MESSAGES (BY SECTION) SUMMARY 5.1: Introduction 5.2: Snow cover 5.2.1: Observed changes in snow cover 5.2.2: Projected changes in snow cover 5.3: Sea ice 5.3.1: Observed changes in sea ice Box 5.1: The influence of human-induced climate change on extreme low Arctic sea ice extent in 2012 5.3.2: Projected changes in sea ice FAQ 5.1: Where will the last sea ice area be in the Arctic? 5.4: Glaciers and ice caps 5.4.1: Observed changes in glaciers and ice caps 5.4.2: Projected changes in glaciers and ice caps 5.5: Lake and river ice 5.5.1: Observed changes in lake and river ice 5.5.2: Projected changes in lake and river ice 5.6: Permafrost 5.6.1: Observed changes in permafrost 5.6.2: Projected changes in permafrost 5.7: Discussion This chapter presents evidence that snow, ice, and permafrost are changing across Canada because of increasing temperatures and changes in precipitation.
    [Show full text]
  • Environmental and Physical Controls on Northern Terrestrial Methane Emissions Across Permafrost Zones
    Global Change Biology (2013) 19, 589–603, doi: 10.1111/gcb.12071 Environmental and physical controls on northern terrestrial methane emissions across permafrost zones DAVID OLEFELDT*, MERRITT R. TURETSKY*, PATRICK M. CRILL† andA. DAVID MCGUIRE‡ *Department of Integrative Biology, University of Guelph, Science Complex, Guelph, ON, Canada N1G 2W1, †Department of Geological Sciences, Stockholm University, Stockholm, SE-106 91, Sweden, ‡US Geological Survey, Alaska Cooperative Fish and Wildlife Research Unit, University of Alaska Fairbanks, Fairbanks, AK 99775, USA Abstract Methane (CH4) emissions from the northern high-latitude region represent potentially significant biogeochemical feedbacks to the climate system. We compiled a database of growing-season CH4 emissions from terrestrial ecosys- tems located across permafrost zones, including 303 sites described in 65 studies. Data on environmental and physical variables, including permafrost conditions, were used to assess controls on CH4 emissions. Water table position, soil temperature, and vegetation composition strongly influenced emissions and had interacting effects. Sites with a dense sedge cover had higher emissions than other sites at comparable water table positions, and this was an effect that was more pronounced at low soil temperatures. Sensitivity analysis suggested that CH4 emissions from ecosystems where the water table on average is at or above the soil surface (wet tundra, fen underlain by permafrost, and littoral ecosys- tems) are more sensitive to variability in soil temperature than drier ecosystems (palsa dry tundra, bog, and fen), whereas the latter ecosystems conversely are relatively more sensitive to changes of the water table position. Sites with near-surface permafrost had lower CH4 fluxes than sites without permafrost at comparable water table posi- tions, a difference that was explained by lower soil temperatures.
    [Show full text]
  • Cryolithogenesis Ground Ice Content of Frost Mounds In
    EARTH’S CRYOSPHERE SCIENTIFIC JOURNAL Kriosfera Zemli, 2019, vol. XXIII, No. 2, pp. 25–32 http://www.izdatgeo.ru CRYOLITHOGENESIS DOI: 10.21782/EC2541-9994-2019-2(25-32) GROUND ICE CONTENT OF FROST MOUNDS IN THE NADYM RIVER BASIN N.M. Berdnikov1, A.G. Gravis1, D.S. Drozdov1–4, O.E. Ponomareva1,2, N.G. Moskalenko1, Yu.N. Bochkarev1,5 1 Earth Cryosphere Institute, Tyumen Scientifi c Centre SB RAS, P/O box 1230, Tyumen, 625000, Russia; [email protected] 2 Russian State Geological Prospecting University (MGRI–RSGPU), 23, Miklukho-Maclay str., Moscow, 117997, Russia 3 Tyumen State Oil and Gas University, 56, Volodarskogo str., Tyumen, 625000, Russia 4 Тyumen State University, 6, Volodarskogo str., Tyumen, 625003, Russia 5 Lomonosov Moscow State University, Faculty of Geography, 1, Leninskie Gory, Moscow, 119991, Russia The “classical type” ice-cored frost mounds (palsas) are widespread in the northern taiga of Western Si- beria. Besides, morphologically diff erent forms of permafrost hummocky landforms are developed, diff erentiat- ing from the “classical” frost mounds by size and fl atter top surface. Using core samples from ten-meter deep boreholes, we have analyzed the total thickness of segregated ice and the contribution of ice inclusions to the total soil ice content, to determine the origin of such fl at-topped mounds. A good correlation has been revealed between surface elevations and volumetric ice content of sediments composing fl at-topped peat mounds, whose ice content is found to be higher than in the intermound depressions. These facts indicate the local nature of ice segregation and therefore suggest that the investigated landforms were formed by the frost heave processes, rather than being remnant permafrost landforms.
    [Show full text]
  • A Song of Ice and Mud Interactions of Microbes with Roots, Fauna and Carbon in Warming Permafrost-Affected Soils
    A song of ice and mud Interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils Sylvain Monteux Akademisk avhandling som med vederbörligt tillstånd av Rektor vid Umeå universitet för avläggande av filosofie doktorsexamen framläggs till offentligt försvar i N430 salen, Naturvetarhuset September 28, kl. 10:15. Avhandlingen kommer att försvaras på engelska. Fakultetsopponent: Prof. Dr., Joshua Schimel, University of California Santa Barbara, Santa Barbara,USA. Department of Ecology and Environmental Sciences Organization Document type Date of publication Umeå University Doctoral thesis 07 September 2018 Department of Ecology and Environmental Sciences Author Sylvain Monteux Title A song of ice and mud: interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils Abstract Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities,
    [Show full text]
  • Decade of Permafrost Thaw in a Subarctic Palsa Mire Alters Carbon Fluxes Without Affecting Net Carbon Balance C
    Decade of permafrost thaw in a subarctic palsa mire alters carbon fluxes without affecting net carbon balance C. Olid*, J. Klaminder, S. Monteux, M. Johansson, E. Dorrepaal Snow depth increases observed in some artic regions have led to a winter- warming of permafrost-containing peatlands. Permafrost thaw and the temperature-dependent decomposition of previously frozen carbon (C) is currently considered as one of the most important feedbacks between the Artic and the global climate system. However, the magnitude of this feedback remains uncertain because winter effects are rarely integrated and predicted from mechanisms active in both surface (young) and thawing deep (old) peat layers. Here, we quantified the effects of long-term in situ permafrost thaw in the net C balance of a permafrost-containing peatland subjected to a 10-years snow manipulation experiment. In short, we used a peat age modelling approach to quantify the effect of winter-warming on the net C balance as well as on the underlying changes in surface C inputs and losses along the whole peat continuum. Contrary to our hypothesis, winter-warming did not affect the net C balance regardless of the increased old C losses. This minimum overall effect is due to the strong reduction on the young C losses from the upper active layer associated to the new water saturated conditions and the decline in bryophytes. Our findings highlight the need to incorporate long-term year-round responses in C fluxes when estimating the net effect of winter-warming on permafrost C storage. We also demonstrate that thaw-induced changes in moisture conditions and plant communities are key factors to predicting future climate change feedbacks between the artic soil C pool and the global climate system.
    [Show full text]