PALEOCEANOGRAPHIC RECONSTRUCTIONS OF SURFACE OCEAN CONDITIONS IN THE GREENLAND, ICELAND AND NORWEGIAN SEAS THROUGH THE LAST 14-KA BASED ON DIATOMS

Prior reconstructions of the last glacial maximum and the Holocene did not include detailed paleoclimate data from the Greenland, Iceland and Norwegian (GIN) seas, which cover sensitive areas for oceanographic boundaries, sea ice distribution and deep water formation. In order to fill this gap, we studied nine well dated sediment cores from this area and reconstructed the paleoceanographic conditions of the surface GIN seas at 2000-year intervals since 13,400 BP based on the diatom record. Results show that a N.-S. extending sea-ice-free corridor had opened along Norway already at 13,400 BP, indicating a northward flow of a branch of the North Atlantic Drift, possibly caused by a change in the jet stream flow due to the decreased height of the North American ice sheet. A major change of climatic conditions occurred over the GIN seas as the insolation anomaly reached its maximum around 9000 BP, when the sea ice cover and the oceanic fronts retreated to a northwesterly position along Greenland, and the ocean temperatures rose. The first half of the Holocene is recorded as the wannest period during the last 13,400 BP in the GIN seas. The duration of this climatic optimum decreased both toward the north and toward the margins of the area. The second half of the Holocene is characterized by a cooling trend in step with the decreasing insolation. These results support the proposal of Imbrie et al. (1992) that the GIN seas region acts as an initial responder to insolation changes.