Response of deep-sea CaCO3 sedimentation to Atlantic meridional overturning circulation shutdown

[1] Changes in the distribution of the preservation and burial of calcium carbonate (CaCO3) in deep ocean sediments and associated atmospheric pCO2 response to the shutdown of the Atlantic meridional overturning circulation (MOC) are examined using an Earth system model. We find that shutdown of the Atlantic MOC forced by the freshwater inflow significantly decreases the CaCO3 content in North Atlantic sediments. This is a consequence of a decrease in bottom-water carbonate ion concentrations and reduction in sea-surface CaCO3 production. The main sedimentary impacts of these two effects are separated in time, however, with reduced CaCO3 production dominating the decrease in CaCO3 burial during the first 1000 years after the forcing is applied. In the absence of significant overturning circulation in the Atlantic, atmospheric pCO2 increases by 11 ppm, largely due to a decrease in POC export and a weakening biological pump. The change in pCO2 induced by reorganization of CaCO3 burial in deep-sea sediments is small, only 1 ppm, because increased preservation of CaCO3 in the Pacific largely efficiently buffers decreased preservation in the Atlantic, leaving the global burial and ocean alkalinity minimally changed at equilibrium.