Uncovering a 70-year-old permafrost degradation induced disaster in the Arctic, the 1952 Niiortuut landslide-tsunami in central West Greenland

On December 15th 1952, at approximately 14:00 local time a mass of 5.9x10(6)m(3) of permafrozen talus deposits failed in a landslide close to the Niiortuut mountain on the south coast of the Nuussuaq peninsula, central West Greenland. Between 1.8 and 4.5x10(6) m(3) of the material entered the sea and generated a tsunami that propagated through the Vaigat strait (Sullorsuaq). Here we describe this catastrophic event for the first time by analysis of historical material supplemented by recent fieldwork and discuss the implications for the state of contemporary permafrozen slopes. The tsunami killed a fisherman working on the shore of southern Nuussuaq, 10 km south-east of the landslide. In the mining town of Qullissat, 30 km south of the landslide, it had a runup height of 2.2-2.7m and causedminormaterial damage. Morphological evidence show that the basal surface of rupture was 80 m inside the permafrost cemented talus slope, whose degradation was a dynamic conditioning factor for the landslide. The 1952 Niiortuut landslide is the first historically recorded event of permafrost degradation induced landslide-tsunamis in the Arctic. We infer that the landslide and its cascading consequences occurred due to the early-twentieth century warming that started in the late 1910's in the Arctic. Warming is now increasingly affecting this region, as shown by an enhanced recent landslide activity.

Automated summary

On December 15th 1952, a large landslide occurred near the Niiortuut mountain on the south coast of the Nuussuaq peninsula in Greenland, resulting in the collapse of permafrozen talus deposits and the generation of a tsunami. This event is the first historically recorded instance of a landslide-induced tsunami in the Arctic caused by permafrost degradation. The warming of the Arctic region since the early twentieth century is likely to have contributed to this event. Recent landslide activity indicates that warming continues to affect this region.