Effects of Deep Circulation on CaCO3 Dissolution and Accumulation in the Southwestern Atlantic Ocean

Abstract Deep oceanic circulation regulates seafloor calcium carbonate (CaCO 3 ) accumulation by transporting atmospheric carbon dioxide (CO 2 ) to depth and then transferring it, with respired CO 2 , along the global ocean conveyor belt. This creates the shallowing trend of CaCO 3 preservation from the Atlantic to the Pacific Oceans. The thermohaline flow can be, however, complex on a basin‐wide scale; here, we use a state‐of‐the‐art data compilation and a carbonate accumulation/dissolution model to explain the CaCO 3 distribution within the basins of the Southwestern Atlantic Ocean. Our results demonstrate that different currents foster systematically dissimilar CaCO 3 preservation within these connected ocean basins. The more undersaturated, faster moving, northward‐flowing Antarctic bottom water readily dissolves more CaCO 3 than the southward‐flowing North Atlantic deep water. We are able to predict quantitatively these observations, based on benthic carbonate chemistry and mass‐transfer rates. Our model and CaCO 3 records in such basins have the potential to provide new understanding about deep‐ocean circulation of the past.