High Resolution Digital Terrain Models Provide Multi-Dimensional Perspective on Thaw Slump-driven Transformation of Permafrost Terrain in the Canadian Western Arctic.

Ice-rich glaciated permafrost environments across northwestern Canada are amongst the most rapidly changing permafrost landscapes of the world. To monitor these dynamic environments, Unmanned Aerial Vehicle (UAV) systems, and Light Detection and Ranging (LiDAR) have enabled highly detailed three-dimensional surface reconstructions (e.g., Digital Elevation Model; DEM) of permafrost thaw features at a scale that bridges the gap between satellite remote-sensing and field-scale observations. Satellite technology now can provide daily-to-weekly observations of mass wasting features such as retrogressive thaw slumps (RTS), but it is primarily limited to two-dimensional size estimations. Our work links two-and three-dimensional measurements of RTS by quantifying area-volume (A/V) relationships to better understand the geomorphic and geochemical implications of rapidly accelerating thaw-driven processes. A LiDAR-derived single-date A/V relationship based on disturbances from fluvial and lake-dominated landscapes across the forest-tundra transition in western Arctic Canada included RTS ranging in size from small slope-side features to mega slumps. The relationship was modeled by a power-law function (R² = 0.90; n = 71) indicating non-linearity in the geomorphic impacts of slump intensification. The capacity of UAVs to derive robust quantitative time-series provides novel insights into permafrost processes that are otherwise challenging to study. Multi-date A/V patterns for individual features track accelerating, linear, and stabilizing RTS change trajectories and provide new insight on thaw-driven processes and feedbacks. The study highlights the importance of exploring A/V relationships to better understand RTS evolution, to predict landscape denudation and ground ice volumes over larger geographic extents, and to back-cast consequences of recent RTS intensification using satellite records.