Through its ability to transport large amounts of heat, fresh water and nutrients, the ocean is an essential regulator of climate1,2. The pathways and mechanisms of this transport and its stability are critical issues in understanding the present state of climate and the possibilities of future changes. Recently, global high-quality hydrographic data have been gathered in the World Ocean Circulation Experiment (WOCE), to obtain an accurate picture of the present circulation. Here we combine the new data from high-resolution trans-oceanic sections and current meters with climatological wind fields, biogeochemical balances and improved a priori error estimates in an inverse model, to improve estimates of the global circulation and heat fluxes. Our solution resolves globally vertical mixing across surfaces of equal density, with coefficients in the range (3–12) × 10-4 m2 s-1. Net deep-water production rates amount to (15 ± 12) × 106 m3 s-1 in the North Atlantic Ocean and (21 ± 6) × 106 m3 s-1 in the Southern Ocean. Our estimates provide a new reference state for future climate studies with rigorous estimates of the uncertainties.
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This work was completed while A.G. was a graduate student in the MIT/WHOI Joint Program in Physical Oceanography. We thank J. Toole, B. Warren, J. Marotzke, D. Glover and N. Hogg. B. Arbic, G. McKinley, A. Czaja, A. Macdonald, J. Marshall and M. Fieux also provided helpful comments on the manuscript. We are grateful to the principal investigators who provided the data from the World Ocean Circulation Experiment and the Franco-Indonesian Java-Australia Dynamic Experiment. G. Brown and D. Spiegel helped to design the figures. We were supported by the Jet Propulsion Laboratory and by gifts from Ford, General Motors and Daimler-Chrysler to MIT's Climate Modelling Initiative. This work is a contribution to the World Ocean Circulation Experiment.
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