| Summary: | Permafrost and active layer thickness (ALT) vary considerably spatially and in response and sensitivity to warming. Understanding the driving influences behind local scale variability and sensitivity is important to guide regional studies. Heterogeneity in the thermal state of permafrost (TSP), ALT and the most important influences on each were analyzed across the western Canadian Arctic and Subarctic. Spatial differences in ALT were related to ecoregional characteristics with increasing average ALT by ecoregion moving south (68 cm to 126 cm) and high variability in ALT for shrub dominated ecoregions (up to 145 cm). The sensitivity of the permafrost model varied between regions, highlighting the importance of winter conditions with less than 60 % of observations remaining within 1 ºC of the original value compared to 72 % for the thawing conditions. Local models of permafrost presence compared to regional models both under current (33% compared to 77%) and future climates (71% compared to 10%) demonstrated the unreliability of regional models in locations where the underlying model assumptions were not valid. Ultimately, the importance of using locally measured data to characterize and adjust regional assumptions was demonstrated. Finally, differential magnitudes of thermal responses to warming (up to 5 ºC), based on the connectivity of the air and ground thermal regime across the analysis, underscores the potential for permafrost resilience and the need to account for variable surface offsets when predicting future permafrost distribution maps.
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