Disequilibrium response of permafrost thaw to climate warming in Canada over 1850–2100

Climate warming would induce permafrost thaw. However, the response of permafrost to atmospheric climate change could take from a few years to millennia. In this study, we simulated the transient changes in ground thermal regimes and permafrost status in Canada over 1850–2100 at a half‐degree latitude/longitude resolution using a process‐based model. The results show that the ground thermal regimes were in strong disequilibrium, with much stronger warming near the surface than in deeper ground. The reduction in permafrost extent (20.5–24.0%) by the end of the 21st century was much smaller than equilibrium projections, but permafrost thaw would continue after the 21st century even if air temperature stops increasing. Permafrost thaw from the top was very significant, and the area with supra‐permafrost taliks increased exponentially, especially during the 21st century. This marked permafrost thaw from the top could have significant impacts on hydrology, landscape, soil biogeochemistry, ecosystems, and infrastructure.