Thermodynamic interaction between seasonal landfast ice and coastal sediments in the Mackenzie Delta, Western Canadian Arctic

Christopher Stevens ‘04
Department of Geology and Geophysics, University of Calgary

High latitude Arctic coastal environments are dynamic interfaces through which onshore and offshore permafrost transitions. Recent climate change and increasing interest in northern resource development have highlighted the need for a comprehensive investigation of permafrost and freeze-thaw process within the coastal zone. Previous research of the thermal regime in these regions has been limited in Canada and elsewhere, due to the technical and logistical challenges of working in remote ice-dominated environments. Over the winters of 2005, 2006 and 2007, the thermal regime of an actively forming distributary mouth bar located in the near-shore zone of the Mackenzie Delta was investigated. Ground Penetrating Radar (GPR), drill, and ground temperature data were used to obtain a better understanding of the current thermal conditions and seasonal changes associated with periods of open water and ice cover. In total, four thermistor cables were successfully installed beneath zones of bottom-fast ice which provided continuous ground temperatures up to 10 m in depth. In addition, over 180 line km of multi-frequency GPR data were acquired from an ice surface to resolve near-shore conditions, including ice thickness, water bathymetry, sedimentary structures and thermal interface. Temperature measurements indicate that beneath zones of bottom-fast ice heat was readily conducted from the underlying sediments, which contributed to the development of seasonal frost and permafrost cooling. At locations where ice contact with the sediment bed was short-lived (less than 80 days), minimal heat flow with the permafrost body occurred until freezeback of the active layer. The spatial variability in ice conditions between the three winters also led to the development of suprapermafrost taliks at some locations. After ice break-up, active layer thaw was measured up to 3 m in depth. These preliminary results provide insight into the influence of landfast ice on near-surface ground temperatures and suggest its control on permafrost stability within the coastal zone.