Response of permafrost to recent extreme warm conditions (2023-2024) in northwestern Canada

The response of permafrost to anomalously warm years is examined within the context of a multi decadal warming trend in the Mackenzie Valley and Delta regions of northwestern Canada. The effects of warm conditions in 1998, 2023, and 2024 on permafrost are compared using long term ground temperature, thaw penetration, and ground surface elevation monitoring records. While 1997-98 is recognized as an extreme warm year that led to significant permafrost thaw and thermokarst development, air temperatures across Canada were even higher in 2023-24. Elevated ground surface temperatures throughout northwestern Canada in 2023-24, coupled with the cumulative impacts of eight warm years since ~2010, resulted in peak permafrost temperatures at half of the study sites and the deepest mean cumulative thaw penetration at 86% of the study sites. Seasonal and regional analyses demonstrate that the warming impacts of 2023-24 occurred later in the northern portion of the Mackenzie Valley and Delta than the central and southern areas. The extreme warm conditions in 1997-1998 were once thought to be exceptional, but permafrost landscapes are expected to be increasingly shaped by the impacts of warm years.