Permafrost, real estate, and climate change: the case of Thompson, northern Manitoba, Canada

Abstract

Unambiguous evidence that permafrost is degrading in response to current global warming is difficult to obtain. Some of the clearest signals are probably provided by changes in permafrost distribution in the subarctic regions, at the extreme southern fringes of the discontinuous permafrost zone. This hypothesis is discussed with reference to Thompson (lat.: 55 degrees north; long.: 98 degrees west), northern Manitoba. During initial construction of the town site in the early 1960's, marginal permafrost bodies were encountered. Some of these have now degraded. Recent air temperature records indicate that the annual mean air temperature in the area has probably increased over the period 1910-1993 by approximately 0.5-1.0°C. A permafrost monitoring program, conducted at 4 forested sites adjacent to the town site between 1969-1976 found that one permafrost site degraded during the period 1968-1971 and two other, non-permafrost sites, showed slight warming. In the 1960's, building had not been permitted on certain subdivision lots where drilling had indicated the presence of shallow permafrost bodies. In the 1990's, the potential high real estate value of these Iots prompted further additional drilling by city authorities. These investigations indicate the absence of permafrost from certain lots, and, as a consequence, new residential housing has been allowed. It is unclear whether the thaw of permafrost bodies at Thompson is the result of 1) recent climate warming, 2) increased thaw consequent upon destruction of the boreal forest, or 3) natural variability.