MIS 3 to MIS 1 temporal and LGM spatial variability in Arctic Ocean sea-ice cover: Reconstruction from biomarkers

摘要

Using the sea ice proxy IP25 and phytoplankton-derived biomarkers (brassicasterol and dinosterol) Arctic sea-ice conditions were reconstructed for Marine Isotope Stage (MIS) 3 to 1 - with special emphasis on the Last Glacial Maximum (LGM) - in sediment cores from the northern Barents Sea continental margin across the Central Arctic Ocean to the Southern Mendeleev Ridge. Our results suggest more extensive sea-ice cover than present-day during latter part of MIS 3, increasing sea-ice growth during MIS 2 and decreased sea-ice cover during the last deglacial. The summer ice edge remained north of the Barents Sea even during extremely cold (i.e., Last Glacial Maximum (LGM)) as well as warm periods (i.e., Bølling-Allerød). During the LGM, the western Svalbard margin and the northern Barents Sea margin areas were characterized by high concentrations of both IP25 and phytoplankton biomarkers, interpreted as a productive ice-edge situation, caused by the inflow of warm Atlantic Water. In contrast, the LGM Central Arctic Ocean (north of 84°N) was covered by thick permanent sea ice throughout the year with rare break-up, indicated by zero or near-zero biomarker concentrations. The spring/summer sea-ice margin significantly extended southwards to the Laptev Sea shelf (southern Lomonosov Ridge) and southern Mendeleev Ridge during the LGM. Our proxy reconstructions are very consistent with published model results based on the North Atlantic/Arctic Ocean Sea Ice Model (NAOSIM).