Geophysical Imaging of Discontinuous Permafrost in Northwest Canada

In order to improve predictions of how hydrological processes in regions of low-relief discontinuous permafrost will respond to future climate warming, it is necessary to understand how discrete bodies of permafrost thaw in the subsurface. Using data collected within the Scotty Creek research basin in the Northwest Territories of Canada, we demonstrate how electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) surveying can be used to delineate accurately the two-dimensional structure of permafrost bodies to depths of around 15 m. Our ERT and GPR images reveal that the permafrost bodies have thicknesses of around 7-12 m, are characterized by steep lateral boundaries and have variable thaw depths beneath permafrost plateaus. Beneath one permafrost plateau, a thaw-depth depression confines some groundwater within an anomalously thick layer of saturated peat. We suggest that enhanced thawing at this location will eventually cause groundwater to 'punch' through the permafrost and provide a conduit for surface runoff to infiltrate into the deep groundwater system.