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RETROGRESSIVE THAW SLUMPS: FROM SLOPE PROCESS TO THE LANDSCAPE SENSITIVITY OF NORTHWESTERN CANADA
Session: Keynote / Conférence
S.V. Kokelj, Northwest Territories Geological Survey, Government of the Northwest Territories (Canada)
J. Tunnicliffe, School of Environment, University of Auckland (New Zealand)
D. Lacelle, Department of Geography University of Ottawa (Canada)
T.C. Lantz, School of Environmental Studies, University of Victoria (Canada)
R.H. Fraser, Canada Centre for Remote Sensing, Natural Resources Canada (Canada)
Retrogressive thaw slumping is an important driver of geomorphic change in ice-rich, glaciogenic landscapes. Here we summarize research on the processes of thaw slump development, with focus on studies from northwestern Canada. In the Peel Plateau, individual slumps commonly exceed 20 ha in area. These “mega slumps” displace downslope up to 106 m3 of previously frozen materials, reconfigure drainage networks, and significantly increase stream sediment and solute loads. The significant acceleration of slump activity has caused this process to become a dominant driver of geomorphic change in several ice-rich environments across the western Arctic. Landsat satellite imagery (1985 to 2011) and high frequency climatic and photographic time-series from the Peel Plateau indicate that an increase in rainfall has accelerated downslope sediment flux from slump scar zones, perpetuating slump activity and intensifying this disturbance regime. Increasing summer rainfall is likely the main factor driving recent geomorphic change. Remotely sensed mapping of slump-impacted terrain across a 1, 275, 000 km2 area of northwestern Canada indicates the close association with ice-rich hummocky moraine landscapes deposited at the margins of the former Laurentide Ice Sheet. This mapping provides a quantitative basis for evaluating the potential for climate-driven landscape change and assessing the spatial distribution of ice-cored permafrost across northwestern Canada.
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