Heinrich-Scale Climate Events in Western North America and the Northeastern Pacific? Testing Possible Mechanisms

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9632029 Pisias This award supports a collaborative effort that will test hypotheses regarding the occurrence of millennial-scale climate fluctuations now recognized in western North America and the northeastern Pacific Ocean. Preliminary data from marine sediments off California and Oregon, pollen records from Pacific Northwest lakes, and glacial records from western North America reveal climate events that appear to be related to the Heinrich events of the North Atlantic. This study will test two hypotheses: 1) that climate events originating in the North Atlantic are transmitted to the North Pacific ocean and western North America via thermohaline circulation and its influence on properties of the surface ocean and circulation of the atmosphere, and 2) that climates of the North Atlantic, North America, and the northeast Pacific depend jointly on the elevation of the Laurentide Ice Sheet and its influence on atmospheric circulation. These hypotheses will be constrained by analyzing the paleoclimate record in a geographic array of sites in the northeastern Pacific Ocean and in western North America, including constraints on oceanic upwelling and near- surface advection, deep ocean properties and vegetation on land, and comparing these data with model output. A significant advance will come from linking the records from land and sea with a well- constrained chronology, and with stratigraphic links of pollen and terrigenous sediment in marine cores.