Permafrost landscapes in a changing climate – Rockslides and Thermokarst along the Forkastningsfjellet coastline

Accelerated climate warming in Arctic latitudes is leading to permafrost degradation, which is accompanied by rapidly changing landscapes. Thawing permafrost and thus related thermokarst processes have significant impacts on local ecosystems and existing infrastructure. Likewise, thawing permafrost threatens Arctic communities by increasing slope instability and potentially correlated displacement waves. However, scarce observational data limits our understanding of deep-seated landslide development in connection with fast thawing permafrost and thermokarst.

Forkastningsfjellet is a rapidly changing coastal mountain range, situated along the eastern margin of Isfjorden, Svalbard, which is affected by such thermokarst activity and rockslide driven coastline changes. Over the past 8 years, we have been documenting accelerating surface deformation and thermo-erosive activity, which in turn led to subsurface drainage, sinkhole and tunnel formation that lowered the stability of the permafrost bedrock of the cliff. The most recent rockslide in November 2022 was promoted by thawing of formerly ice-filled cracks and increasing pore water pressures within the strongly fractured bedrock. Due to continuing head scarp retrogression and ongoing gully formation along pre-existing zones of weakness, cliff collapse will most likely continue.

In order to achieve a better understanding of the process rates and the associated mass transfer, we use integrated, cross-platform datasets (drone imagery, satellite data, surface temperature measurements and differential GPS) to analyse the process dynamics, quantify rates of cliff top retreat and the correlated surface mass transfer. Our results are of fundamental importance for the understanding of future engineering geological hazard scenarios in Arctic coastal regions.