Rapid mass movements triggered by rain-on-snow events associated with atmospheric rivers in West Greenland

Rapid mass movements in cold mountain environments are an important geomorphic factor that shapes the landscape, as well as a potential source of geohazard. Although their triggering mechanisms have been investigated in multiple studies, the spatial and temporal distribution of these events is poorly known in most Arctic regions. Among rapid mass movements that can be triggered abruptly by precipitation and snowmelt, we report a large-scale event that involved Central West Greenland in July 2023. Rain-on-snow linked to an atmospheric river event triggered more than 150 slushflows in Disko Island (Qeqertarsuaq). Pre-post event remote sensing imagery was used to map the affected areas, while environmental monitoring data and climate reanalysis products provided insights into the atmospheric river event and its impact on a snow-dominated landscape. During the 18-hour event, cumulative precipitation peaked at 115 mm, with more than 80 mm in several areas among the most affected by debris and snowpack mobilization. We show how the extreme precipitation rates reached during this event are similar to those experienced during a few other rapid mass movement events (i.e., wet-slush avalanches, slush flows, and debris flows) documented in various locations across West Greenland. The implications of such extreme rain-on-snow events in the Arctic are still poorly known. We suggest increasing remote-sensing based efforts to monitor and map rapid mass movements in critical areas of the Arctic, as most of them go unnoticed when infrastructure or large-scale damage are not involved.