MULTI-SCALE INVESTIGATIONS OF PERMAFROST LANDSCAPE CHANGE (Invited Presentation)

Ice-rich permafrost terrains comprise some of the most rapidly changing landscapes in the world due to the effects of climate-driven permafrost thaw. Thermokarst is the surface manifestation of thaw-driven geomorphic change. It can be expressed as discrete features on thawing slopes such as retrogressive thaw slumps or as contiguous areas where particular surface and subsurface conditions give rise to broad areas of disturbed terrain as in the case of degrading ice-wedge polygons. Present-day patterns of thermokarst are a product of geological, climate and environmental history. The nature and distribution of thermokarst is a critical indicator of subsurface conditions and terrain sensitivity, and a predictor of the trajectories of landscape change. This presentation will highlight thermokarst landscape sensitivity using empirically-driven models and explore geophysical factors driving the alteration of thermokarst systems and how they are represented at different scales.

Thermokarst types have been inventoried across northwestern Canada at various spatial scales using a combination of high-resolution satellite imagery and mapping methods. These inventories have been used to develop statistical models (Random Forest) that identified the relationship between the spatial distribution of thermokarst and terrain characteristics (i.e. surficial geology, permafrost condition, slope, aspect, elevation, vegetation), which can then be used to predict landscape scale sensitivity to future thermokarst. The relative importance of terrain variables in the model reflects geomorphic process and provides insight into the controls over thermokarst development. As climate continues to warm, knowledge of the physical factors driving the alteration of thermokarst systems and a regional-scale analysis of thermokarst is necessary to not only assess hazards and inform management of northern infrastructure and heritage assets but to also better understand the trajectories of northern ecosystem change and the cascade of downstream consequences.