PERILOUS PERMAFROST: NAVIGATING THE COMPLEXITIES OF PERMAFROST-RELATED LANDSLIDES IN A CHANGING CLIMATE, DEMPSTER HIGHWAY, YUKON

Keywords: Permafrost, landslides, active layer detachments, retrogressive thaw flow slides, climate change, wildfire

Thaw of permafrost and associated ground ice can lead to surface subsidence and slope instability, consequently modifying terrain and drainage patterns. Permafrost-related landslides are complex phenomena influenced by multiple interacting factors. These mass-movements are a growing concern due to the impacts of increasing global temperatures, changing precipitation regimes, and wildfire-induced ground disturbance. Landslides in permafrost terrain can also induce further permafrost degradation, releasing previously trapped carbon into the atmosphere and contributing to global climate change. Active layer detachments (ALDs) and retrogressive thaw flows (RTFs) are two types of landslides caused by permafrost degradation that are impacting the Dempster Highway in northern Yukon. The Dempster Highway starts just south of Dawson, Yukon, and traverses northeast to Inuvik, NWT. The study area lies within unglaciated terrain and passes through the North Ogilvie Mountains and Eagle Plains Upland. Understanding the complex relationships between the climatological, geological, and cryological factors contributing to the morphology of these landslides is important for predicting future hazard areas and protecting highways and communities in the north.

This study investigates a section of the Dempster Highway that experienced an intense wildfire in 2017. In the years following the fire a high density of ALDs have occurred, resulting in the formation of RTFs that are still active today. Data collection involves synthesizing previous literature, analysis of satellite imagery and LiDAR data, and field work to produce descriptions of landslides and how they have evolved over the last six years. Initial results indicate ALDs initiation commonly occurs on slopes consisting of sandstone and shale colluvium. RTFs evolve in areas with ice-rich permafrost where the ALDs removed insulating organics. These continue to be a significant sediment source in the area. This research contributes to understanding the triggers, dynamics, and impacts of permafrost-related landslides on the Dempster Highway and is important for keeping the corridor safe and accessible.