CGRG Bibliography of Canadian Geomorphology
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Author : Fortier, D.; Stephani, E.; and Allard, M.
Date : 2004.
Title : Gully formation in ice-wedge polygons areas: an analog for climate warming induced permafrost degradation.
Publication : Arctic Net. First Annual Scientific Meeting, Palace Royal, Quebec City. December 5-8, 2004. Program.
Issue :
Page(s) : 31.
Abstract
In the Canadian Arctic archipelago, and other continuous permafrost regions, ice-wedges networks under tundra polygons often represent the dominant form of ground-ice. Tundra polygons originate in the elaborate network of thermal contraction cracks. These cracks fill up with ice that comes primarily from snowmelt water that seeps into the permafrost and refreezes as a vein. As cracks reoccur in already existing cracks, the accretion of ice veins with time builds up ice wedges. Polygonal networks can be particularly well developed in favourable geomorphological contexts. One such network is located on Bylot Island (730 09’ N, 800 00’ W), where we observed catastrophic terrain modifications resulting from the sudden destabilisation of the thermal regime of permafrost. Knowledge of the landscape resulting from the destabilisation of the thermal regime of the ground is useful in climate warming studies focusing on the thermo-erosion of tundra polygons due to increased snow-melt run-off, on the thermo-abrasion of river bluff due to increased glacier melt and on the degradation of coastal permafrost due to sea-level rise or land subsidence. Starting in 1999, after the snowmelt period, surface run-off water flowed in opened frost-cracks and thereafter directly into ice wedges. Piping processes rapidly formed a flowing tunnel network in the permafrost. Most tunnels roofs fissure, break and collapse under their own weight during the summer of their formation, altough some of them can last a few years. Tunnel collapse created retrogressive headscarps retreating upslope. During the summer, incoming solar radiation and the advection of sensible and latent atmospheric heat lead to ground-ice melt on the slopes of the gully, thaw-consolidation of the sediments, gradual surface subsidence, mass displacement and eventually the destruction of the polygons. After four summers, the area affected by the thermo-erosion and thermokarst of the ice-wedges was 20 000 m2. This polygenetic thermokarst phenomenon leads to major geomorphologic and ecological disturbances of the environment such as the development of a new hydrographic network, the drying of wetlands, the drainage of lakes and, on certain occasions, to the inception of pingos.
Bibliography of Canadian Geomorphology