Postglacial canyon incision primes ice-cored hillslopes for thaw slumping in the western Canadian Arctic

Abstract Thaw-induced permafrost landslides, or thaw slumps, exemplify the alarming potential of rapid Arctic climate change to couple with unstable geomorphic feedbacks and escalate landscape hazards, sediment and solute fluxes, and carbon emissions. An emergent hot spot of thaw slump activity in the western Canadian Arctic provides an opportunity to understand the geomorphic context that predisposes some regions to extreme thaw sensitivity. Previous research suggests that slump concentration in this region may result from postglacial incision of ice-cored moraine along the historical margin of the Laurentide Ice Sheet. We assess this hypothesis in the Aklavik Range of the Northwest Territories, where we mapped 217 thaw slumps and reconstructed more than 3 m/k.y. of bedrock canyon incision since the Last Glacial Maximum. We find that thaw slumps tend to form between fluvially incised bedrock and relict till hillslopes. More than 75% of thaw slumping occurs within 500 m of incised bedrock, and hillslope normalized steepness explains over 33% of slump size variability. We interpret intense regional thaw slumping as a climate-sensitive landscape response to postglacial base-level change propagating into ice-cored hillslopes. This finding implies that the end-member permafrost disturbances observed in the western Canadian Arctic may be limited outside regions that share analogous geomorphic context.