LATE QUATERNARY PALEOCEANOGRAPHY OF THE EURASIAN BASIN, ARCTIC-OCEAN

We reconstructed late Quaternary deep (3000-4100 m) and intermediate d epth (1000-2500 m) paleoceanographic history of the Eurasian Basin, Ar ctic Ocean from ostracode assemblages in cores from the Lomonosov Ridg e, Gakkel Ridge, Yermak Plateau, Morris Jesup Rise, and Amundsen and M akarov Basins obtained during the 1991 Polarstern cruise. Modern assem blages on ridges and plateaus between 1000 and 1500 m are characterize d by abundant, relatively species-rich benthic ostracode assemblages, in part, reflecting the influence of high organic productivity and inf lowing Atlantic water. In contrast, deep Arctic Eurasian basin assembl ages have low abundance and low diversity and are dominated by Krithe and Cytheropteron reflecting faunal exchange with the Greenland Sea vi a the Fram Strait. Major faunal changes occurred in the Arctic during the last glacial/interglacial transition and the Holocene. Low-abundan ce, low-diversity assemblages from the Lomonosov and Gakkel Ridges in the Eurasian Basin from the last glacial period have modern analogs in cold, low-salinity, low-nutrient Greenland Sea deep water; glacial as semblages from the deep Nansen and Amundsen Basins have modern analogs in the deep Canada Basin. During Termination 1 at intermediate depths , diversity and abundance increased coincident with increased biogenic sediment, reflecting increased organic productivity, reduced sea-ice, and enhanced inflowing North Atlantic water. During deglaciation deep Nansen Basin assemblages were similar to those living today in the de ep Greenland Sea, perhaps reflecting deepwater exchange via the Fram S trait. In the central Arctic, early Holocene faunas indicate weaker No rth Atlantic water inflow at middepths immediately following Terminati on 1, about 8500-7000 year B.P., followed by a period of strong Canada Basin water overflow across the Lomonosov Ridge into the Morris Jesup Rise area and central Arctic Ocean. Modern perennial sea-ice cover ev olved over the last 4000-5000 years. Late Quaternary faunal changes re flect benthic habitat changes most likely caused by changes in the imp ort of cold, deepwater of Greenland Sea origin and warmer and middepth Atlantic water to the Eurasian Basin through the Fram Strait, and exp ort of Arctic Ocean deepwater.