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TitleVariability in shallow ground thermal conditions, Mackenzie Valley, NWT, Canada
AuthorSmith, S L; Riseborough, D W
SourceProceedings, IPY 2012 Knowledge to action conference; 2012 p. 1
Alt SeriesEarth Sciences Sector, Contribution Series 20110197
MeetingIPY 2012 Knowledge to Action Conference; Montréal; CA; April 22-27, 2012
Mediaon-line; digital
File formatpdf
ProvinceNorthwest Territories; Yukon
NTS95G; 95H; 95I; 95J; 95K; 95N; 95O; 96B; 96C; 96D; 96E; 96F; 96L; 96M; 96N; 97B; 97C; 106G; 106H; 106I; 106J; 106K; 106L; 106M; 106N; 106O; 106P; 107A; 107B; 107C; 107D
AreaMackenzie corridor; Gwich'in; Fort Good Hope; Norman Wells; Inuvialuit; Deh Cho; Sahtu
Lat/Long WENS-136.0000 -118.0000 70.0000 61.0000
Subjectssurficial geology/geomorphology; freezing ground; ground ice; ground temperatures; permafrost; thermal analyses; temperature
ProgramProgram Management - Climate Change Science, Climate Change Geoscience
AbstractPermafrost is an important component of the landscape of the Mackenzie Valley that influences both natural and human systems. The active layer, the near surface layer that freezes and thaws seasonally, is responsive to short-term fluctuations in climate. Since travel and construction activities in the north often occur in the winter and are dependent on frozen ground conditions, the timing of these activities can vary with fluctuations in climate. Although air temperature is an important factor, site specific conditions including snow cover duration and vegetation can significantly influence the interannual variability of the shallow ground thermal regime. Recent efforts have resulted in an updated characterization of the permafrost thermal state for representative terrain types throughout the Mackenzie Valley, representing the International Polar Year (IPY) snapshot. In addition, time series were also extended which have facilitated an investigation of the spatial and temporal variability of the shallow ground thermal regime including the interannual variability in the onset of ground freezing and thawing.

Air and near-surface ground temperature data collected between 1993 and 2008 for 54 sites were analysed. Although mean annual air temperature generally follows the latitudinal gradient, mean annual near-surface ground temperature shows greater spatial variability reflecting the variability in vegetation and in particular its effect on snow cover conditions. Near-surface ground temperature, including freezing and thawing indices also exhibit greater temporal variability compared to that for air temperature. A comparison of the two IPY years, 2007 and 2008, further illustrates the high interannual variability in near-surface thermal conditions, particularly in the Mackenzie Delta area. In 2007, onset of ground thawing generally occurred later at sites north of 68°N compared to 2008. This may be in part related to later spring melt of snow cover and greater June snow cover extent reported by Brown et al. (2010). In 2008, the onset of ground freezing at these sites was generally later (in some cases more than a month later) compared to 2007 which may reflect early snow accumulation in the autumn. These results indicate the influence that timing and duration of snow cover may have on the shallow ground thermal regime and the freezing and thawing of the active layer. Improved quantification of the timing and variation of ground freezing and thawing with changing climatic conditions can inform decisions regarding winter construction and transportation activities and support northern infrastructure design in a changing climate.