Retreat patterns and dynamics of the former Bear Island Trough Ice Stream

Covering one of the widest continental shelves in the world, the epicontinental Barents Sea is characterized by several shallow banks separated by troughs that open towards the Norwegian Sea in the west and the Arctic Ocean in the north (Fig. 1a). The bank areas have typical water depths of 100–200 m and the troughs 300–500 m. The most prominent cross-shelf trough, the Bear Island Trough (Bjornoyrenna), extends over 750 km from Storbanken (‘the large bank’ in Norwegian) in the NE to the shelf break in the SW (Fig. 1a). It is 150–200 km wide and spans water depths of 300–500 m. Ice sheet reconstructions over the last decades have recognized that a major ice sheet covered the whole Barents Sea during the Last Glacial Maximum (LGM; Mangerud et al. 1992; Svendsen et al. 2004). Large trough-mouth fans (TMFs; Vorren et al. 1989) appear as seaward-convex bulges in the bathymetry at the mouth of troughs that extend to the shelf break. The largest of these, the Bear Island Trough-Mouth Fan (Fig. 1a), contains up to 3–4 km of Plio-Pleistocene glacial sediments. The location of a major ice stream in the Bear Island Trough, draining the former Barents Sea and Fennoscandian ice sheets and delivering large amounts of sediments to the Bear Island TMF during the LGM (Fig. 1a), has been inferred from seafloor geomorphology and palaeo-ice-sheet geometry (Denton & Hughes 1981; Solheim et al. 1990; Ottesen et al. 2005; Andreassen et al. 2007), from studies of the fan itself (e.g. Vorren & Laberg 1997) and from borehole data (Saettem 1994). Two late glacial maxima have been inferred in the SW Barents Sea, one before 22 cal ka BP and one after 19 cal ka (Vorren & Laberg 1996). Fig. 1. Bathymetry, geomorphology, Last Glacial …