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TitlePermafrost modelling in northern Great Slave region, Northwest Territories, Phase 1: Climate data evaluation and 1-d sensitivity analysis
AuthorRiseborough, D W; Wolfe, S A; Duchesne, C
SourceGeological Survey of Canada, Open File 7333, 2013, 50 pages,
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories
NTS75L; 75M; 76D; 85I; 85J; 85N; 85O; 85P; 86A; 86B; 86C
AreaYellowknife; Great Slave Lake; Gordon Lake; MacKay Lake; Lac de Gras
Lat/Long WENS-117.0000 -110.0000 65.0000 62.0000
Subjectssurficial geology/geomorphology; engineering geology; permafrost; freezing ground; ground ice; ground temperatures; terrain sensitivity; terrain types; terrain analysis; arctic geology; modelling; mapping techniques; climate, arctic; climate
Illustrationslocation maps; tables; plots; stratigraphic sections
Natural Resources Canada Library - Ottawa (Earth Sciences)
ProgramLand-based Infrastructure, Climate Change Geoscience
Released2013 03 13
AbstractClimate variables were examined to evaluate their use in permafrost models, using data for Yellowknife Northwest Territories, Canada as an example. Results suggest that conversion of the annual temperature cycle to a sine wave is an acceptable approximation, as long as the wave retains the correct values for the annual freezing and thawing degree-day totals. Changes in snow depth can be approximated by a parabolic accumulation function. The delay of snow cover initiation with respect to the start of the freezing season, the snow accumulation function, and snow density are all critical, whereas end-of-season snowpack evolution is of secondary importance.
Modelling results show that any difference in substrate materials produces a change in the mean annual temperature at the top-of-perennially frozen/unfrozen ground (TTOP) and annual maximum freezing/thawing layer thickness (AFTT). The greatest differences in TTOP were produced by changes in the thickness and degree of saturation of the surface organic layer. Intermediate differences were due to differences in substrate materials within and immediately below the annual freezing/thawing layer itself, and the smallest differences were due to variations in the substrate well below the thickness of the annual freezing/thawing layer. These results suggest that knowledge or consideration of the thickness and moisture content of organic soil veneers will be vital to permafrost mapping in this environment.
Summary(Plain Language Summary, not published)
Permafrost (ground that remains below 0°C) exists under the combined conditions of a cold climate and suitable terrain properties. In the area north of Great Slave Lake, permafrost is close to its southern limit, and can be easily disturbed by changes at the ground surface, including climate change. This study provides some initial results as part of a project to map permafrost conditions in the Northern Great Slave region using computer models. Permafrost conditions were represented using computer simulation of typical terrain conditions in the region, as influenced by the Yellowknife climate. Results show that knowing the thickness and moisture content of the surface peat layer is important for accurate predictions of permafrost distribution.