Evolution of events before and after the 17 June 2017 landslide at Karrat, West Greenland – a multidisciplinary approach for studying landslides in a remote arctic area

• Main Authors: Svennevig, Kristian, Dahl-Jensen, Trine, Keiding, Marie, Boncori, John Peter Merryman, Larsen, Tine B., Salehi, Sara, Solgaard, Anne Munck, Voss, Peter H.
• Format: Text
• Language: English
• Published: 2020
• Subjects: Arctic; Greenland; Isfjord; Karrat Isfjord; Nuugaatsiaq; permafrost
• Online Access: https://doi.org/10.5194/esurf-2020-32; https://esurf.copernicus.org/preprints/esurf-2020-32/

The 17 June 2017 rock avalanche on the south facing slope of the Ummiammakku Mountain (Karrat Isfjord, West Greenland) caused a tsunami that flooded the nearby village of Nuugaatsiaq, killed four persons and destroyed 11 buildings. Landslide activity in the area was not previously known and the disaster gave rise to important questions about what events led up to the landslide and what the future hazard is in the area around the landslide? However, the remoteness of the area and difficult fieldwork conditions, made it challenging to answer these questions. We apply a multidisciplinary workflow to reconstruct a timeline of events on the coastal slope here collectively termed the Karrat Landslide Complex. The workflow combines limited fieldwork with analyses of freely available remote sensed data comprising seismological records, Sentinel-1 space borne Synthetic Aperture Radar (SAR) data and Landsat and Sentinel-2 multispectral optical satellite imagery. Our analyses show that at least three historic rock avalanches occurred in the Karrat Landslide Complex: Karrat 2009, Karrat 2016 and Karrat 2017. The last is the source of the tsunami and the first two are described for the first time here. All three are interpreted to have initiated as translational rockslides. In addition to the historical rock avalanches, several pre historic rock avalanche deposits are observed, demonstrating older periods of activity. Furthermore, three larger areas of continuous activity are described and may pose a potential future hazard. A number of non-tectonic seismic events confined to the landslide complex are interpreted to record landslide activity. Based on the temporal distribution of events in the landslide complex, we speculate that the possible trigger for landslides is permafrost degradation caused by climate warming. The results of the present work highlight the benefits of a multidisciplinary approach based on freely available data to studying landslides in remote Arctic areas under difficult logistical field conditions and demonstrates the importance of identifying minor precursor events to identify areas of future hazard.