Distribution and growth of thaw slumps in the Richardson Mountains–Peel Plateau region, northwestern Canada

Abstract

Retrogressive thaw slumps are one of the most active geomorphic features in permafrost terrain. This study investigated the distribution and growth of thaw slumps in the Richardson Mountains and Peel Plateau region, northwestern Canada, using Tasseled Cap (TC) trend analysis of a Landsat image stack. Based on the TC linear trend image, more than 212 thaw slumps were identified in the study area, of which 189 have been active since at least 1985. The surface area of the slumps ranges from 0.4 to 52ha, with 10 slumps exceeding 20ha. The thaw slumps in the region are all situated within the maximum westward extent of the Laurentide Ice Sheet. Based on relations between frequency distribution of slumps and that of terrain factors in the landscape, the slumps are more likely to occur on the ice-rich hummocky rolling moraines at elevations of 300–350m and 450–500m and along east-facing slopes (slope aspects of 15° to 180°) with gradients of 8° to 12°. Pixel-level trend analysis of the TC greenness transformation in the Landsat stack allowed calculating headwall retreat rates for 19 thaw slumps. The 20-year average retreat rates (1990–2010 period) for 19 slumps ranged from 7.2 to 26.7myr−1, with the largest slumps having higher retreat rates. At the regional scale, the 20-yr headwall retreat rates are mainly related to slope aspect, with south- and west-facing slopes exhibiting higher retreat rates, and large slumps appear to be generating feedbacks that allow them to maintain growth rates well above those of smaller slumps. Overall, the findings presented in this study allow highlighting of key sensitive landscapes and ecosystems that may be impacted by the presence and growth of thaw slumps in one of the most rapidly warming region in the Arctic.