Extensive hydrogeological disruption triggered by an atmospheric river affecting Disko Island (West Greenland) in summer 2023

Debris flows and slush flows are mass movements that can be triggered abruptly by precipitation and snowmelt. They are a well known contributor to geomorphic changes and potential geohazards in areas such as the subpolar regions. In this study we discuss and analyze a series of mass movements linked to a single event that happened between July 6^th and 7^th 2023 in Central West Greenland. An atmospheric river led extreme precipitation into Qeqertarsuaq (Disko Island) and surrounding areas, increasing late spring snowmelt runoff significantly and causing hundreds of slush flows and debris flows, which also damaged local infrastructures. We combined remote sensing observations (Sentinel-2 and drone-based) before and after the event to map the larger mass movements. We then used the environmental monitoring dataset available in the area (Greenland Ecosystem Monitoring Disko) and climate reanalysis (Copernicus Arctic Regional Reanalysis) data to assess the synoptic pattern at the base of the event. We found almost 200 significant slush flows and debris flows only in Disko Island. During the 18-hours-event cumulative precipitation peaked 100mm being generally above 80mm in several portions of the island (mainly in the Southwest) where most events occurred. An increase in moisture transport through atmospheric rivers in a warming Arctic, has already been seen as a further contributor to abrupt glacial melting. We show here how such events are able to trigger potential hazards to local communities, making necessary to increase our knowledge about past events and future hazards in remote and less monitored areas, such as Greenland.