Monitoring of retrogressive thaw slumps

PhD student: Philipp Bernhard

Vast areas of the Arctic host ice-rich permafrost, which is becoming increasingly vulnerable to rapid thaw in a warming climate. Rapid permafrost degradation has major impacts on the local hydrology and ecosystems, and it can also reinforce climate change by mobilizing organic carbon, leading to the emission of the greenhouse gases CO2 and CH4. One important land surface characteristic arising from rapid thaw are retrogressive thaw slumps (RTS). In addition to the mobilization of carbon, these slumps can alter the chemistry of streams and rivers and need to be considered in the planning of infrastructure.

By differencing DEMs generated at different instants in time, we can perform change detection. The following image shows an application of this technique to monitor changes in the permafrost in the Mackenzie River Delta, Canada:

Enlarged view: DEM differencing to monitor permafrost thawing — Observations of a thaw slump in the Mackenzie River Delta, Canada. A: Aerial photo of a thaw slump (courtesy Simon Zwieback). B: Sentinel-2 L1C image of part of the area in the Mackenzie River Delta (Date: 21.08.2017), C: Result after DEM generation process for single-pass TanDEM-X observation in the Science Phase (01.06.2015). The heigt change shows the difference to a previous TanDEM-X DEM from 2013. The strong height change of up to -8m indicate that the thaw slump shown in A was increasing in size between the two observations.