Electrical conductivity and ground displacement in permafrost terrain

Abstract

Permafrost and ground ice are important features of the landscape that can significantly affect infrastructure in cold regions. Information on thaw susceptibility is important for predicting the behaviour of permafrost as an engineering substrate. We compare apparent conductivity surveys to ground displacement obtained from differential interferometric synthetic aperture radar with the objective of establishing apparent conductivity as an indicator of thaw susceptibility for regional characterization of terrain stability and permafrost conditions along the western coast of Hudson Bay, Nunavut. For field conditions where ground displacement and conductivity are influenced by surficial geology, there is a correlation between high seasonal and inter-annual subsidence and low apparent conductivity, and between high seasonal and inter-annual subsidence and high seasonal conductivity ratio, inferred to be indicative of high ice content and thaw-related displacement. For field conditions with no strong influence of surficial geology, a clear correspondence between subsidence and apparent conductivity does not exist. Nevertheless, the geophysical data are useful in identifying relevant factors for characterization of terrain stability such as saline permafrost and an ice-rich top of permafrost that experience significant seasonal fluctuations in unfrozen water content. When utilizing low-induction number electromagnetic surveys in permafrost terrain, apparent conductivity must be corrected for a depth-dependent temperature profile. For this study, correction factors of 6–13% are required to compensate for temperature variation, or 2.1% per °C at half-depth, but this is not necessarily applicable to other temperature profiles.