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Warming-induced destabilization of peat plateau/thermokarst lake complexes
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2011 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 116, G03035- p.Article in journal (Refereed) Published
Abstract [en]

Peat plateaus are widespread at high northern latitudes and are important soil organic carbon reservoirs. A warming climate can cause either increased ground subsidence (thermokarst) resulting in lake formation or increased drainage as the permafrost thaws. A better understanding of spatiotemporal variations in these landforms in relation to climate change is important for predicting the future thawing permafrost carbon feedback. In this study, dynamics in thermokarst lake extent during the last 35-50 years has been quantified through time series analysis of aerial photographs and high-resolution satellite images (IKONOS/QuickBird) in three peat plateau complexes, spread out across the northern circumpolar region along a climatic and permafrost gradient. From the mid-1970s until the mid-2000s there has been an increase in mean annual air temperature, winter precipitation, and ground temperature in all three study areas. The two peat plateaus located in the continuous and discontinuous permafrost zones, respectively, where mean annual air temperatures are below -5 degrees C and ground temperatures are -2 degrees C or colder, have experienced small changes in thermokarst lake extent. In the peat plateau located in the sporadic permafrost zone where the mean annual air temperature is around -3 degrees C, and the ground temperature is close to 0 degrees C, lake drainage and infilling with fen vegetation has been extensive and many new thermokarst lakes have formed. In a future progressively warmer and wetter climate permafrost degradation can cause significant impacts on landscape composition and greenhouse gas exchange also in areas with extensive peat plateaus, which presently still experience stable permafrost conditions.

Place, publisher, year, edition, pages
2011. Vol. 116, G03035- p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:su:diva-66512DOI: 10.1029/2010JG001635ISI: 000295130400002OAI: oai:DiVA.org:su-66512DiVA: diva2:469862
Note
authorCount :2Available from: 2011-12-27 Created: 2011-12-20 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Temporal and spatial dynamics in subarctic peat plateaus and thermokarst lakes
Open this publication in new window or tab >>Temporal and spatial dynamics in subarctic peat plateaus and thermokarst lakes
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Permafrost peatlands are widespread at high northern latitudes and are important soil organic carbon reservoirs. A future warming in these areas, as suggested by global climate models, can cause thawing and increased ground subsidence (thermokarst), resulting in changes in surface hydrology and ecosystem functioning. The aim of this thesis is to increase our knowledge of temporal and spatial dynamics in subarctic peat plateaus with interspersed thermokarst lakes in order to better understand how these ecosystems respond to climate change. Detailed plant macrofossil and carbon/nitrogen ratio analyses of two peat plateaus located in the continuous and northern discontinuous permafrost zones in west-central Canada show that permafrost conditions have been stable since permafrost developed around 5600–4500 cal yr BP. Peat plateaus act as carbon sinks over time. The lack of wet phases since the plateaus formed, despite several local fires, suggests that this type of peatlands have been negligible as methane sources throughout most of their history, representing a negative net radiative forcing on climate. Thermokarst lakes are common features in peat plateaus across the northern permafrost region. A time-series analysis of aerial photographs and high resolution satellite images in three peat plateau/thermokarst lake complexes along a climatic and permafrost gradient shows that where the mean annual air temperature (MAAT) is below -5ºC and ground temperatures are -2ºC or colder, only minor changes in thermokarst lake extent have occurred from the mid 1970s until the mid 2000s. During the same time interval extensive lake drainage and new lake formation has taken place where the MAAT is ca -3ºC and the ground temperature is close to 0ºC. In a future progressively warmer and wetter climate, permafrost degradation can cause significant impacts on landscape pattern and greenhouse gas exchange also in the vast peat plateaus presently experiencing stable permafrost conditions.

Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography and Quaternary Geology (INK), Stockholm University, 2010. 36 p.
Series
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 23
Keyword
Peatlands, permafrost, subarctic, peat plateau, thermokarst lake, macrofossil analysis, carbon/nitrogen ratio, peat accumulation, carbon accumulation, remote sensing, binary encoding, time-series analysis
National Category
Natural Sciences
Research subject
Physical Geography
Identifiers
urn:nbn:se:su:diva-42115 (URN)978-91-7447-106-9 (ISBN)
Public defence
2010-10-01, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Manuscript.Available from: 2010-09-09 Created: 2010-08-17 Last updated: 2011-12-27Bibliographically approved

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