Ocean Circulation and Climate Impacts of Proglacial Lake Outbursts into the Northeastern Pacific Ocean

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Numerous models have explored the impact of North Atlantic freshwater flood events in the context of abrupt climate change at the end of the last ice age, suggesting these events had major impact on the meridional overturning circulation (MOC) system. During the early deglaciation (roughly 16,600 to 13,000 BC), cataclysmic floods from proglacial Lake Missoula inundated eastern Washington-Oregon and passed into the Pacific Ocean via the Cascadia Basin. While we know that turbidity currents originating from these floods penetrated nearly 1000 km into the North Pacific to depths over 3km there is little understanding of the impact of this freshwater discharge on ocean circulation or climate. Unlike the North Atlantic, the most likely scenario for climate impact from freshwater discharge into the Northeast Pacific involves changes in structure of the upper ocean and thermocline properties. This project will conduct modeling experiments (idealized ocean-only and fully-coupled numerical CCSM3 model simulations) to explore the impacts of a surface layer discharge event versus convection from a hyperpycnal, subsurface flow to test the hypothesis that flood induced changes in N. Pacific subploar-subtropical ocean circulation could influence the position of the intertropical convergence zone (ITCZ), thereby providing a mechanism for influencing climate via tropical air-sea interaction. The project will also use radiocarbon date core material to establish a chronology of outburst events.Broader Impacts of Proposed WorkThis project will enhance collaborations between physical oceanographers, paleoceanographers and paleoclimatologists. The Pacific Northwest Pleistocene floods are a phenomenon of great interest to the general public because they dramatically affected much of the regional landscape. Results of the proposed research will be used to educate the public about processes of current day climate change through connections to changes seen during glacial times. A young female post-doc will receive valuable cross-disciplinary training from three leading scientists in the geosciences.