Northern landscapes are changing rapidly as a result of climate-driven permafrost thaw, impacting ecosystems and communities. Although broad-scale empirical datasets describing the nature, distribution, and susceptibility to permafrost degradation are crucial to support climate change planning and adaptation, these do not exist for northern Canada. This knowledge gap stimulated the NWT Thermokarst Mapping Collective (TKC), a project bringing together permafrost and geomatics expertise to develop methods to systematically inventory thermokarst and periglacial landforms around NWT communities and across the NWT. Here we synthesize TKC-generated data for over 17,000 km2 around 33 NWT communities (5,625 km2 per community) and explore variations and similarities between communities in terms of thermokarst processes and associated impacts. Our assessment draws out regional trends in thaw-driven landscape change and highlights linkages to permafrost conditions, geologic setting, and climate.
For example, large retrogressive thaw slumps occur primarily in mountainous and hilly terrain with ice-rich permafrost, posing a serious hazard to communities and infrastructure in the Tundra Cordillera. Thaw slumps are common in the Tundra Plains as well, although these are constrained in size by geologic and topographic setting, and are found more commonly on coastlines and lakeshores rather than in steeply incised terrain. Deep-seated landslides are observed throughout the Cordilleran but there is a southward increase in cases where the failure plane occurs at the base of thin permafrost, indicating yet another suite of mass wasting processes. Thermokarst lake dynamics are common in extensive areas of low-relief terrain in the Tundra and Taiga Plains and over the Shield. In the Tundra Plains, lake and pond expansion related to polygonal networks and ice-wedge degradation are common, whereas further south in the Taiga Plains, thermokarst lake development and peatland degradation are widespread. The latter occurs over the Shield as well, although to a lesser extent, as organic terrain is less extensive and ramparted lakes are more common thermokarst features.
This sensitivity assessment provides a first quantitative overview of complex combinations of thermokarst processes and thaw-related issues affecting NWT communities. Identifying overarching trends and community-specific suites of thermokarst landscapes will improve our understanding of the consequences of permafrost thaw, let us prioritize community geohazard mapping, and support climate change adaptation planning.