Sedimentological, Geochemical and Isotopic Evidence for the Establishment of Modern Circulation through the Bering Strait and Depositional Environment History of the Bering and Chukchi Seas during the Last Deglaciation

SEDIMENTOLOGICAL, GEOCHEMICAL AND ISOTOPIC EVIDENCE FOR THE ESTABLISHMENT OF MODERN CIRCULATION THROUGH THE BERING STRAIT AND DEPOSITIONAL ENVIRONMENT HISTORY OF THE BERING AND CHUKCHI SEAS DURING THE LAST DEGLACIATION Sea level regression during the Last Glacial Maximum exposed the Bering Land Bridge, and cut off the connection between the North Pacific and Arctic Ocean, ending the exchange of North Pacific Water through the Bering Strait. Exchange of North Pacific Water comprises a major portion of fresh water input to the Arctic Ocean, and is of vital importance to North Atlantic Deep Water formation, a vital component of Atlantic Meridional Overturning Circulation. Bering Strait throughflow thus plays an integral role in global climate stability. A suite of four cores were selected, three in the Bering Sea and one in the Chukchi Sea, to bracket the Bering Strait in order to elucidate changes in sediment delivery, productivity and regional oceanography as the Bering Land Bridge flooded and modern ocean circulation was established during the last deglaciation. The arrival of nutrient rich North Pacific Water in the Chukchi Sea is recorded around 8 ka by organic carbon isotope depletion and increases in total organic carbon and organic nitrogen, reflecting an increasingly marine isotopic signal and increased productivity. In the Bering Sea, the early deglaciation is marked by depleted organic carbon isotopes that indicate increasing terrestrial input, and increased total organic carbon. Principal component analysis of sedimentologic, geochemical and isotopic data clearly captures discrete sediment populations that correspond to key climatic intervals, representing changes in sediment delivery, productivity and circulation during the last deglaciation. In the Bering Sea we observe