ABSTRACT: Evolution geomorphologique holocene des polygones à coins de glace de la vallée du glacier C-79, Ile Bylot, archipel arctique canadien [Holocene geomorphological evolution of ice-wedge polygons, valley of glacier C-79, Bylot Island, Canadian Arctic archipelago].

CGRG Bibliography of Canadian Geomorphology
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A reconstitution of the paleoenvironments and paleoclimates of Bylot Island (730 09’N, 800 00’ W), in the Canadian Arctic archipelago, was realized through a detailed geomorphological analysis of syngenetic ice-wedge polygons and by the stratigraphic analysis of the sedimentary sequences accumulated in the depressed centers of the polygons. These reconstitutions are based on new geomorphological, cryostratigraphical, sedimentological, geophysical, geochronological and climatological data. During the Holocene, the recession of glacier C-79, located in the south-western part of Bylot Island, has led to the genesis of a large glacio-fluvial outwash following the marine regression in the valley after 6000 BP. The cooling that began during the Neoglacial, that is during the Late Holocene has led to a decrease in glacier melt and glacio-fluvial activity. The rheological properties of the ground and the initial configuration of the syngenetic ice-wedge polygons network that developed in the glacio-fluvial outwash of glacier C-79 were modified after the accumulation of more than two meters of loess and organic sediment; this accumulation began after 3670 ± 110 BP. The sedimentary sequence comprised of loess, peat and ice has been dated and analyzed in order to detect significant changes of the surface wind regime and of the precipitation – evaporation (P-E) regime of the polygons that occurred during the last 3500 years. Changes in the P-E regime were always linked to changes of the summer surface wind regime, probably in response to changes in the position of the ''Canadian Polar Trough''. The active geomorphological processes were also characterized. Air temperature and ground thermal conditions occuring in the frost-cracking process of permafrost were determined by in-situ measurements. The research also allowed the characterization of the process of underground thermo-erosion of ice wedges. This process is responsible for the rapid destruction of the polygons, the development of thermokarst gullies, wetland and lake drainage and, on certain occasion, the growth of pingos. This process has led to the formation of thermokarst gullies covering and area of 20 000 m2 after 4 summers of activity from 1999 to 2002.

Bibliography of Canadian Geomorphology