October 11, 2023 Tsunami: Dickson Fjord, Greenland

Reference #13837 (supplementary):

Twenty-five days after the rock-ice avalanche of 2023-09-16, described in the main text, a new landslide occurred in the gully. The event was first recognized in the seismic record as it produced a VLP [very long-period (VLP) signal]. A Sentinel-2 satellite image from 2013-10-13 showed that the glacier in the gully was now eroded even more than during the September 16th event, and the part of the glacier protruding into Dickson Fjord was also further reduced in size. No clear new landslide scar has been observed, but the glacier is dirtier after the event at a higher elevation than before.

Tsunami runup could be observed in the images in two places: 200 m west of the mouth of the gully 60 m runup was mapped.

Field validation was not possible for this event because the Danish military does not patrol by boat this late in the season and the Air Force surveillance plane was not available. Furthermore, open-access satellite acquisition stops in this region in late October due to arctic winter darkness. We interpret the above event to be a minor (relative to the September 16th) landslide that entrained a large portion of the glacier. The initial landslide might have been composed of material deposited in the impact area of the gully after the September 16th rock-ice avalanche or be a minor rockslide from the back-scarp of the September 16th rockslide.

Reference #14052:

These landslides were caused by debuttressing of the glacier following glacial thinning over the past decade […] Tsunami run-up for the October 11th even was only observed 200 m west of the gully ~75% of the magnitude of the September event in this location (60 m vs 80 m)