Frequency‐Domain Airborne Electromagnetic Imaging of Permafrost Reveals Heterogeneity and Drivers of Permafrost Change in the Discontinuous Permafrost Zone of Northwestern Canada

Abstract Northern permafrost landscapes are undergoing rapid warming and thaw, yet the three‐dimensional subsurface structure that governs thaw vulnerability and landscape response remains poorly resolved by conventional ground temperature monitoring and satellite remote sensing. Frequency‐domain airborne electromagnetic (AEM) surveys can resolve permafrost structure rapidly at regional scales across complex terrain. Here, we present three representative survey lines from 1,340 line‐km of AEM data collected in the central Mackenzie Valley, Northwest Territories. Rather than relying on fixed resistivity thresholds, we develop a gradient‐based method to identify permafrost depth and transition‐zone thickness from vertical resistivity gradients, enabling consistent mapping across warm (>−2°C) discontinuous permafrost. Interpretations are evaluated using a co‐located electrical resistivity tomography profile and borehole temperature measurements in the context of regional surficial geology mapping. The AEM survey images resistivity to depths of ∼100 m along a linear infrastructure corridor and reveals permafrost thicknesses ranging from absent beneath sufficiently large, deep, or persistent waterbodies to ∼35 m in undisturbed uplands. Results demonstrate pronounced lateral heterogeneity controlled by geology, hydrology, slope position, vegetation cover, and disturbance history. Areas affected by wildfire in the past three decades exhibit persistently reduced shallow resistivity, broadened permafrost‐base transition zones, and locally thinner permafrost, whereas talik networks, including through‐going taliks that fully disrupt permafrost continuity, are resolved beneath sufficiently large, deep, or persistent waterbodies. These findings quantify the subsurface legacy of disturbance and highlight spatial variability and vulnerability within the discontinuous permafrost zone, with implications for infrastructure stability, groundwater connectivity, and future thaw trajectories.