Spatial Variability of Permafrost and Active Layer Thickness in a Forested Hillslope of the Taiga Shield

ABSTRACT Under continued climate warming, understanding present‐day permafrost distribution and the controls on ground thaw are critical for predicting permafrost thaw trajectories and associated implications. This study presents a high‐resolution investigation of permafrost extent and active layer thickness (ALT) across a coniferous forested hillslope in the discontinuous permafrost zone near Yellowknife, Northwest Territories, Canada. Using ground‐penetrating radar (GPR), electrical resistivity tomography (ERT), and frost probing, spatial patterns of permafrost distribution and ALT were mapped and evaluated in relation to key environmental factors. Seasonal thaw patterns revealed greater early‐season thaw at hillslope margins, whereas end‐of‐season variability was primarily governed by topographic gradients. Although ALT was correlated with multiple surface and subsurface characteristics, wet soil conditions at the hillslope base emerged as the dominant control on hillslope‐scale ALT variability. Permafrost occurred in isolated patches along the transition from forested terrain to exposed bedrock, where shallow overburden constrained permafrost development. At the forest to wetland transition, increased ALT and indications of suprapermafrost taliks suggest that elevated soil moisture and associated latent heat inhibit complete refreezing to the permafrost table, highlighting the critical role of moisture in regulating permafrost stability. These results showcase substantial ALT variability over small spatial scales and demonstrate the influence of adjacent land covers in governing permafrost distribution within forested hillslopes. By characterizing high‐resolution spatial patterns of ALT and contemporary permafrost occurrence within a representative regional land cover, this study provides key insights to improve permafrost modeling and vulnerability assessments under continued climate warming.