US-France Cooperative Research: Variability in Thermohaline Circulation and North Atlantic Climate

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0233483McManusThis three-year award for US-France collaboration in climate change involves researchers at the Woods Hole Oceanographic Institution and the Laboratory for Climate Sciences and Environment of the French National Center for Scientific Research (CNRS). Jerry F. McManus in the US and Laurent Labeyrie in France will lead this collaborative program to model and analyze the variability in thermohaline circulation and impact on North Atlantic climate. The ocean's thermohaline circulation has undergone reorganization on various time scales, with important implications for understanding the Earth's climate in the past and present. Nutrient proxies provide important evidence of watermass reconfigurations. Dynamical tracers may provide an ideal complement to this information by allowing quantitative evaluation of changes in the rates of deepwater formation and export. Combination of watermass properties and overturning rate could yield direct estimates of the transport by the ocean's thermohaline circulation. To this end, the US and French investigators will refine a method that utilizes two long-lived uranium series, 231 Pa and 230 Th. They will construct maps of the burial ratio (231Pa/230Th) in bulk sediment cores of the Atlantic Ocean. In addition, they will evaluate the link between changes in circulation and climate variability through high-resolution time series. The US group brings to this collaboration expertise in the area of Uranium-series radiochemistry. This is complemented by French expertise in spatial coverage and resolution and access to the IMAGES cores repository in France.This award represents the US side of joint proposals to the NSF and the French National Center for Scientific Research (CNRS). NSF will cover travel funds and living expenses for the US investigators. CNRS will support the visits of the French researchers and a graduate student to the United States. The project will advance understanding of the causes and potential impact of ocean circulation on climate change and abrupt climate change in the North Atlantic.