Mapping the Activity and Evolution of Retrogressive Thaw Slumps by Tasselled Cap Trend Analysis of a Landsat Satellite Image Stack

Retrogressive thaw slumps are a dominant agent of geomorphic change in ice‐rich permafrost landscapes and may remain active for decades. Previous studies of slump activity have used aerial photographs and/or high‐resolution satellite images acquired at (multi)‐decadal time intervals. This study investigates if the calculation of the three Tasselled Cap transformations (brightness, greenness and wetness) from a dense stack of Landsat Thematic Mapper and Enhanced Thematic Mapper+ images can be used to identify slump activity and map slump evolution at near‐annual resolution. Results obtained from analysis of slumps in the Richardson Mountains‐Peel Plateau region of the Northwest Territories, Canada, suggest that Tasselled Cap linear trend images effectively identify both active and stable thaw slumps. In addition, the analysis of single‐date Tasselled Cap values at the pixel level can be used to map the initiation, growth and stabilisation of slumps at near‐annual timescales. The Tasselled Cap trend analysis method therefore offers the possibility to: (1) map the distribution of thaw slumps by activity level (active, stable or relict); (2) derive headwall retreat rates at near‐annual resolution; and (3) determine patterns of stabilisation and re‐vegetation over the period of available Landsat images. The rich temporal information provided by Landsat analysis complements conventional, higher spatial resolution (but lower temporal resolution) methods that map slumps from pairs of aerial photographs and high‐resolution satellite imagery.