Sedimentary processes associated with recent landslides – Karrat Fjord 2017 case of study

Tsunamigenic landslides represent a major geohazard in the fjord environments of central West Greenland, induced by steep topographic reliefs and changing Arctic conditions. A dramatic example occurred on June 17^th 2017, when a slope failure on the south-facing wall of Ummiammakku Mountain released a 38-40 × 10⁶ m³ rock avalanche into Karrat Fjord. The event generated a displacement wave with local runup heights exceeding 90 m and propagated 32 km southwest to the settlement of Nuugaatsiaq, causing severe infrastructure destruction and four fatalities. In this study we have integrated swath bathymetry and seismic datasets, along with sediment core information, to map mass-transport deposits produced by the 2017 rock avalanche in Karrat Fjord. By integrating geophysical imaging, lithofacies descriptions, XRF geochemistry, grain-size distributions, and ²¹⁰Pb-dating, this study delineates the channelized runout of the 2017 event.

The increasing frequency of landslides in West Greenland has motivated new research into the climatic and cryospheric controls on slope instability. Although the region is tectonically stable with only minor earthquake activity, recent studies suggest a connection between warming climate, permafrost degradation, and enhanced slope failure. This hypothesis aligns with broader observations across polar margins that link rising temperatures, increased precipitation, and isostatic rebound with enhanced decreasing slope instability. Our findings demonstrate the value of high-resolution marine datasets for detecting offshore landslide deposits and contribute new insights into the temporal and spatial patterns of slope instability in a rapidly changing Arctic fjord system.