GEOSCAN, résultats de la recherche


TitreClimate and permafrost relations across widely separated sites in northern Canada
AuteurThroop, J; Smith, S L; Lewkowicz, A G
SourceThermal state of frozen ground in a changing climate during the IPY, abstracts from the Third European Conference on Permafrost; par Mertes, J R (éd.); Christiansen, H H (éd.); Etzelmüller, B (éd.); 2010 p. 342
Séries alt.Secteur des sciences de la Terre, Contribution externe 20090435
Réunion3rd European Conference on Permafrost (EUCOPIII); Longyearbyen, Svalbard; NO; juin 14-18, 2010
ProvinceTerritoires du Nord-Ouest; Nunavut; Yukon
SNRC25; 26; 27; 35; 36; 37; 38; 39; 45; 46; 47; 48; 49; 55; 56; 57; 58; 59; 65; 66; 67; 68; 69; 75; 76; 77; 78; 79; 85; 86; 87; 88; 89; 95; 96; 97; 98; 99; 105; 116; 107; 115; 116; 117; 120; 340; 560
Lat/Long OENS-141.0000 -60.0000 90.0000 60.0000
Sujetspergélisol; congélation du sol; glace fossile; températures au sol; climat arctique; géologie des dépôts meubles/géomorphologie; géologie de l'environnement
ProgrammeLes sciences de la Terre à l'appui de la caractérisation, à l'échelle nationale, des impacts des changements climatiques sur la masse continentale canadienne, Géosciences de changements climatiques
Résumé(disponible en anglais seulement)
Permafrost zones extend across 50% of Canada's land area, with conditions varying from continuous through to isolated patches, along latitudinal and elevational gradients (Heginbottom et al., 1995). The purpose of this study is to determine the spatially variable influence of climate on permafrost tempera-tures at nine widely separated thermal monitoring sites in northern Canada (Figure 1).

The study sites encompass various environmental and climatic conditions, and range from ice-rich sediment with mean annual temperatures just below 0°C in the sporadic discontinuous permafrost zone, to bedrock at temperatures close to -15°C in the con-tinuous permafrost zone. There are between one and five boreholes at each site ranging in depth from 3 to 60 m.

A comparative analysis was conducted to assess the variability in climate-permafrost relationships across space. The local characteristics at each bore-hole were assessed using the mean annual air and ground temperatures (MAAT and MAGT, respec-tively), freezing n-factor (nf), apparent thermal dif-fusivity (ATD), snow characteristics, and substrate.

A strong relationship exists between MAAT and MAGT across all of the sites. The differences be-tween these two variables increase as MAAT in-creases. The strongest relationships were observed at Alert and Iqaluit, where the least amount of snow accumulates.
The sites with MAGTs close to 0°C are consid-ered warm permafrost, and the sites below -2°C are considered cold permafrost. The ATD was at least an order of magnitude lower at the warm permafrost sites than the cold ones, and generally increased with increasing depth across all of the sites.

The warm permafrost sites at Wrigley, Table Mountain, and Wolf Creek had the lowest values of nf, ranging between 0.21 and 0.44. Values of nf were highest at very cold or bedrock sites, Alert, Iqaluit, Sixty Mile, and Alpine Burwash, even though some of these sites had significant amounts of snow. Al-though snow has a great influence on air-ground sur-face temperature relationships during the winter, the relationship is modulated by air temperatures, active layer thickness, and subsurface moisture.
The influence of vegetation and snow characteris-tics, substrate, and frozen and unfrozen moisture on the thermal link between air and permafrost tem-peratures is evident through the variations in annual temperature amplitude propagation.

MAAT is the primary determinant of permafrost temperatures across these study sites in northern Canada. Cold bedrock sites are more sensitive to changes in climate than the warm ice-rich perma-frost sites. The relationship between snow and nf de-pends not only on MAAT and active layer thickness, but also on the substrate material and moisture con-tent, both frozen and unfrozen, at the site.