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TitlePermafrost in the Mackenzie Delta, Northwest Territories
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorSmith, M W
SourceGeological Survey of Canada, Paper no. 75-28, 1976, 34 pages, Open Access logo Open Access
PublisherEnergy, Mines and Resources Canada
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthwest Territories
Lat/Long WENS-136.0000 -132.0000 69.0000 68.0000
Subjectsmathematical and computational geology; engineering geology; surficial geology/geomorphology; geothermal gradient; ground temperatures; permafrost; soil studies; talik; thermal analyses; resistivity surveys, ground
Released1976 05 01; 2013 03 18
AbstractVariations in ground temperature regime and permafrost distribution were studied between 1969 and 1971 in a small area in the east-central part of the Mackenzie Delta about 50 km northwest of Inuvik, Northwest Territories. The Delta is an area of active sedimentation and erosion, and about 50 per cent of the study area is covered by water. A major distributary in the study area is undergoing lateral migration, and the local configuration of permafrost is closely related to the history of river migration. The vegetation shows a successional sequence related to river migration indicating a complex interaction between vegetation, topography, and microclimate. The major objectives of the study were to: (1) describe the permafrost and ground temperature variations in the study area; (2) understand how local environmental factors influence the ground temperature field; and (3) analyze the development of the present ground temperature field in terms of its position in the long-term migration history of a shifting channel. In order to monitor the ground temperature variations, boreholes were drilled to various depths up to 30 m. Temperatures were measured with thermistors, and these measurements were augmented with seismic and resistivity surveys. Lake and river temperatures also were recorded and ground materials were sampled from boreholes. Measurements of ground temperatures, snow depths, and ice cover were made in winter. Permafrost is discontinuous; calculations indicate that permafrost is absent beneath channels and lakes that are wider than 80 to 100 m. Ground temperatures are warmer close to water bodies, and the permafrost table falls steeply beneath cutbanks. Observations indicate permafrost thicknesses of between 50 to 65 m in stable, spruce-covered areas. Calculations show that the maximum permafrost thickness in the area is about 100 m at sites most distant from water bodies. Beneath slip-off slopes, where temperatures are warmer than beneath cutbanks, permafrost is only 2. 5 to 9 rn thick, thickens away from the river, and disappears towards it. Permafrost is absent in some places where winter snow drifts are deep. Using simple heat conduction theory a consistent explanation of permafrost distribution in terms of local environmental factors is developed. The heat conduction models are suitable for ground temperature prediction, with agreement typically within 20. S°C of observed values for most sites. Calculations of thermal disturbance due to channel shifting are in general agreement with observations, although omission of the latent heat term leads to some errors.

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