"Carbon dioxide (CO2), produced and released to the atmosphere by human activities, has been accumulating in the oceans for approximately two centuries and will continue to do so well beyond the end of this century if emissions are not curbed. One direct consequence of CO2 build-up in the atmosphere and its transfer to the ocean is the acidification of seawater. Calcite, a mineral secreted by many organisms living in the surface ocean to produce their shells and skeletons, covers a large part of the seafloor and acts as a natural anti-acid, neutralizing CO2. Thus, a precise knowledge of the kinetics of this dissolution reaction is necessary to predict the ocean recovery time towards its pre-acidification state once anthropogenic CO2 emissions are curbed. This thesis combines laboratory experiments, oceanographic measurements and model outputs to explore and unravel the mechanisms that control calcite dissolution at the sediment-water interface (SWI) on the seafloor in the context of current anthropogenic ocean acidification. Using a newly developed temperature-controlled rotating-disk reactor, as well as a stirred reactor, we were able to measure the rate of dissolution of simulated and natural sediment disks of variable calcite content under environmental and hydrodynamic conditions representative of deep-sea benthic environments. These experiments revealed that, in contrast to the reigning paradigm that calcite dissolution kinetics in seawater is surface reaction-controlled and of high order, calcite dissolution at the SWI and under deep-sea conditions is linearly dependent on the undersaturation state of the overlying seawater with respect to calcite and controlled by the presence of a diffusive-boundary layer (DBL) above the sediment bed. Therefore, irrespective of the mineralogy and sediment properties, the dissolution rate is simply a function of the saturation state of the overlying seawater with respect to calcite, the calcite content of the sediment, and hydrodynamics at the seafloor. From these observations, using a compilation of seawater chemical variables in the global ocean, corresponding sediment calcite content and rain rates, as well as recently modeled bottom current velocities, we have been able to identify the loci of current anthropogenic calcite dissolution and its rate. We found that significant anthropogenic dissolution of calcite at the seafloor currently occurs in the western North Atlantic, where the bottom waters are youngest, and at various hot spots in the southern Atlantic, Indian and Pacific Oceans. Using model projections for the 21st century, under a “business as usual” scenario, we found that while seawater will become more corrosive to this mineral, calcite dissolution at the seafloor will decrease in intensity because bottom currents will slow down and the amount of calcite particles delivered to the seafloor will diminish. These results indicate that the neutralization of human-made CO2 by calcite dissolution at the seafloor may take longer than previously thought. These findings are of critical interest to the scientific community and the public, as these results have far reaching implications for ocean acidification mitigation, to the fate of benthic communities living under increasing environmental stress, and to geologists contemplating both present and past records of ocean acidification"--