Permafrost temperatures were measured by the Geological Survey of Canada (GSC) in 1977-1981 at boreholes along a proposed pipeline route in the southern Yukon. Analysis of climate station records indicate that mean annual air temperatures in the region have since increased by 0.5-1.0˚C. Renewed interest in the pipeline and the need to develop adaptation strategies for existing highway infrastructure have meant that information on permafrost and geotechnical conditions must be updated. To accomplish this goal, a total of eight GSC boreholes ranging in depth from 5-9 m were located, unblocked of ice and instrumented with thermistor cables and data-loggers to permit renewed ground temperature monitoring. Manual temperature measurements were also taken at four other shallow boreholes. Electrical resistivity tomography (ERT) surveys were conducted at each site.
MAGTs below 1 m at permafrost sites in the study area range from -0.2˚C to -1.5˚C with permafrost depths greater than 25 m. The permafrost at the study sites can be classified as sporadic discontinuous and extensive discontinuous. Ground temperatures indicate that permafrost can persist under warmer climatic conditions as long as it remains protected by its ecosystem properties.
Thermal monitoring for 2011-2012 shows an average increase of 0.5-1.0˚C when compared to the original 1978-1981 ground temperatures. This slow rate of ground warming is mainly attributed to a combination of limited climate change, especially in the south of the study area, ground temperatures close to 0˚C, and the possible disturbance of sites from the removal of vegetation prior to the original measurements being made. ERT surveys conducted at most borehole sites show deeper thaw or taliks where the cleared cut-line used for geophysical work in the 1970s is crossed.
These results indicate the impacts of climate change and environmental change in the study area over the past three decades. They appear to match the relatively slow rates of ground warming observed elsewhere in northern Canada where permafrost temperatures are close to 0˚C and where warming also requires changes in latent heat due to internal thaw. TTOP equilibrium modelling suggests that if climate change is responsible for the ground warming, most of the change can be attributed to the step-like MAAT increase that occurred between 1975-1976.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OOU.#10393/24300 |
| Date | 09 July 2013 |
| Creators | Maxime Arsène, Duguay |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thèse / Thesis |
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