Thaw-depth monitoring

Abstract

Fifty-eight sites have been established along a 1200 km transect in the Mackenzie valley to monitor processes linking climate, climate change, permafrost, and the active layer. Annual maximum thaw penetration and surface movement are measured relative to thaw tubes anchored in permafrost. Active layer thickness, calculated from thaw penetration and surface movement, varies as a result of local soil properties, vegetation, and microclimate as well as regional atmospheric climate. Whereas thaw penetration has increased at most sites over the last 6 8 years, this increase is not always reflected by an equivalent increase in active layer thickness because of thaw settlement. Frequent air and shallow ground temperatures provide a complementary record at many sites. Active layer thickness influences biotic soil conditions, foundation performance, slope stability, and hydrology. Monitoring the active layer can contribute to modelling near surface permafrost and the impact of environmental change and can assist adaptation.