Re-advance of the Fennoscandian Ice Sheet during Heinrich Event 1

Five sediment cores, bathymetric and 2D seismic reflection data from Vestfjorden, northern Norway, were studied in order to constrain the timing and extent of a major ice stream draining the northwestern Fennoscandian Ice Sheet during the last deglaciation (15–10 14C ka B.P.). The bathymetric and seismic data indicate that Vestfjorden/Trænadjupet was covered by grounded ice reaching the shelf break during the Last Glacial Maximum (LGM). After the LGM break-up and recession towards outer inner Vestfjorden at ∼ 13.6 14C ka B.P., the ice re-advanced towards the outer part of Vestfjorden prior to 13.1 14C ka B.P. This is inferred from glaciomarine sediments overlain by diamicton at the base of the sediment cores interpreted as basal tills and associated contemporaneous build-up of grounding zone wedges in the central Vestfjorden. This sequence of events is coherent with the late Weichselian ice sheet dynamics both along the western Norwegian continental shelf and in the Barents Sea, possibly indicating a direct response to meltwater injection and accompanied cooling during disruption of the thermohaline circulation associated with Heinrich Event 1. Enhanced supply of suspension load resulted in deposition of laminated sediments at ∼ 13 14C ka B.P. reflecting the retreat of the ice stream towards the inner fjord in response to global climate amelioration and increased Atlantic water inflow. Two additional ice re-advances towards the Norwegian coastline are inferred from distinct input of ice-rafted debris (IRD) with a typical mineralogical fingerprint derived from Neoproterozoic–Early Silurian calcite and dolomite marbles in the ice sheet catchment area. Thus, the re-advances may be concurrent with the Older Dryas (∼ 12.2 14C ka B.P., Skarpnes) and Younger Dryas (∼ 10.7 14C ka B.P., Tromsø Lyngen) cooling events.