Revealing permafrost continuity across a northern watershed with airborne electromagnetics

Accelerated permafrost thawing in warming northern climates may alter groundwater-surface water dynamics, thereby impacting hydrologic and ecologic functions, and the potential release of stored carbon species as greenhouse gases. Such rapid changes to the hydrologic system will present unique challenges for many northern communities including changes in land surface features, water fluxes and quality, and wildlife habitat. Here, we present the results of an airborne frequency-domain electromagnetic survey conducted over a discontinuous permafrost region within the Central Mackenzie Valley in Northwest Territories, Canada. Electrical resistivity measurements within the upper 100 metres were gathered across a geologically complex environment where permafrost variability is hypothesized to be impacting the groundwater-surface water system. A comparison of permafrost observations from boreholes with resistivity measurements allowed delineation of frozen conditions in shallow surficial sediments and underlying bedrock. Observed vertical and lateral variability in permafrost extent around lakes and streams indicates direct connectivity between surface water, overburden, and bedrock stratigraphic units. Conversely, extensive permafrost along and below the expansive Mackenzie River reveal relatively continuous permafrost occurrence limiting interaction with deeper groundwater. High-resolution investigations of permafrost dynamics will be critical in understanding the effects of its rapid degradation due to warming climatic conditions within northern landscapes.