The ice cap of Austfonna in eastern Svalbard is the largest in the Eurasian Arctic at 8000 km2 and has about 200 km of marine-terminating ice cliffs (Dowdeswell et al. 2008). Several of its drainage basins are of surge type (Meier & Post 1969) and, between 1936 and 1938, one of these basins (Bråsvellbreen; 1100 km2) increased its velocity rapidly and underwent an advance of about 20 km along a 30 km wide front (Schytt 1969). Since that time the ice-cap terminus has stagnated and retreated, losing mass by a combination of surface melting, thinning and iceberg production. Retreat has revealed several distinctive and well-preserved submarine landforms (Fig. 1) linked to this recent surge activity (Solheim & Pfirman 1985; Solheim 1991).
(a) Rhombohedral ridges and a terminal moraine ridge on the seafloor offshore of Bråsvellbreen, an outlet of the Austfonna ice cap in eastern Svalbard. Image courtesy of the Norwegian Hydrographic Service (Permission no. 14/G754). Acquisition system Kongsberg EM1002. Frequency 97 kHz. Grid-cell size 3 m. The ridges are interpreted to have been formed by the filling of basal crevasses with deforming diamictic sediment. (b) Oblique aerial photograph of the surge and rapid advance of Bråsvellbreen in 1938 (Photo S38-1958; courtesy of Norsk Polarinstitutt). (c) Location of study area (red box; map from IBCAO v. 3.0). (d …
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Rhombohedral crevasse-fill ridges at the marine margin of a surging Svalbard ice cap
