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 5.9 × 106 m3 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 4.5 × 106 m3 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 2.2-2.7 m and caused minor material 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.

Postglacial relative sea level change and glacier activity in the early and late Holocene: Wahlenbergfjorden, Nordaustlandet, Svalbard.

Sediment cores from Kløverbladvatna, a threshold lake in Wahlenbergfjorden, Nordaustlandet, Svalbard were used to reconstruct Holocene glacier fluctuations. Meltwater from Etonbreen spills over a threshold to the lake, only when the glacier is significantly larger than at present. Lithological logging, loss-on-ignition, ITRAX scanning and radiocarbon dating of the cores show that Kløverbladvatna became isolated from Wahlenbergfjorden c. 5.4 cal. kyr BP due to glacioisostatic rebound. During the Late Holocene, laminated clayey gyttja from lacustrine organic production and surface runoff from the catchment accumulated in the lake. The lacustrine sedimentary record suggests that meltwater only spilled over the threshold at the peak of the surge of Etonbreen in AD 1938. Hence, we suggest that this was the largest extent of Etonbreen in the (mid-late) Holocene. In Palanderbukta, a tributary fjord to Wahlenbergfjorden, raised beaches were surveyed and organic material collected to determine the age of the beaches and reconstruct postglacial relative sea level change. The age of the postglacial raised beaches ranges from 10.7 cal. kyr BP at 50 m a.s.l. to 3.13 cal. kyr BP at 2 m a.s.l. The reconstructed postglacial relative sea level curve adds valuable spatial and chronological data to the relative sea level record of Nordaustlandet.