Abstract
Abstract. On the 17 June 2017, a massive landslide which mobilized 35–58 million m3 of material entered the Karrat Isfjord in western Greenland. It triggered a tsunami wave with a runup height exceeding 90 m close to the landslide, ca. 50 m on the opposite shore of the fjord. The tsunami travelled ca. 32 km along the fjord and reached the settlement of Nuugaatsiaq with ca. 1–1.5 m high waves which flooded the terrain up to 9 m a.s.l. (above sea level). Tsunami waves were powerful enough to destroy the community infrastructure, impact fragile coastal tundra landscape, and unfortunately injure several inhabitants and cause four deaths. Our field survey carried out 25 months after the event results in documentation of the previously unreported scale of damage in the settlement (ca. 48 % of infrastructure objects including houses and administration buildings were destroyed by the tsunami). We have observed a recognizable difference in the concentration of tsunami deposit accumulations between areas of the settlement overwashed by the wave and areas of runup and return flow. The key tsunami effects preserved in the coastal landscape were eroded coastal bluffs, gullied and dissected edges of cliffed coast in the harbour, and tundra vegetation compressed by boulders or icebergs rafted onshore during the event.
Highlights
Known to the research community for at least 60 years, the occurrence, scale, and impacts of tsunamis in cold regions (Arctic and subarctic) still shock the wider public
We have explored ArcticDEM (Porter et al, 2018) resources and compared terrain changes between pre- and post- tsunami digital terrain models (DTMs) to determine the scale of coastal landscape modification entailed by tsunami impact
In ESRI ArcGIS software a 2 m DTM constructed from satellite images captured on 11 September 2016 was subtracted from DTM captured on 19 June 2017 to calculate elevation difference between models and check if sites where tsunami erosion and deposition detected during fieldwork were traceable in digital terrain models (Fig. 6)
Summary
Known to the research community for at least 60 years, the occurrence, scale, and impacts of tsunamis in cold regions (Arctic and subarctic) still shock the wider public. The landslide which entered Lituya Bay in Alaska in 1958 triggered a giant tsunami wave with a runup height of over 500 m (Miller, 1960) Another wave (runup over 190 m) recorded in 2015 in Taan Fjord, Alaska, was caused by a landslide from local slopes destabilized by the retreat of Tyndall Glacier (Dufresne et al, 2018; Higman et al, 2018; Haeussler et al, 2018; Bloom et al, 2020). In the last hundred years tsunamis were recorded in Norwegian fjords, e.g. the Tafjord 1934 event (e.g. Harbitz et al, 2014)
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