Collaborative Research: Testing the Northern Route for Younger Dryas Meltwater

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The PIs propose a three-year project to investigate the origin of the Younger Dryas cooling. New evidence suggests that glacial Lake Agassiz released fresh water to the Arctic through the Mackenzie River and they propose that this signal should be detectable along the western margin of the Canadian Archipelago in the oxygen isotope ratio in the shells of planktonic foraminifera. The project involves a three-week expedition to survey the seafloor and subbottom layers and collect sediment cores from the eastern Beaufort Sea, a region that is remote and has not been well explored. Besides the sediment processing and micropaleontology that are part of generating the isotope data that reflect sea surface salinity, two complementary shore-based projects are proposed. The first is to integrate the new geophysical data on the continental margin with the climate history of the open sea, sediment transport, relative sea level change, and terrestrial climate, as they have done previously for the Chukchi Sea. The second is to compare the geochemical data with results from a high resolution General Circulation Model that is configured to reveal the path and the mixing of the melt water. Although the paleoceanographic data will be spatially limited, model runs will show the low salinity distribution in the Arctic as well as in the Nordic seas where the freshening may have affected deep ocean overturning and caused the Younger Dryas cooling.The Younger Dryas was a period of climatic cooling that began about 13,000 years ago and lasted more than 1000 year. It reversed a period of climatic warming, even though insolation continued to increase. This study will attempt to determine the mechanism that allowed such a reversal in temperature trend to occur and, thus, inform discussions of whether similar changes are probable in the future.