The fate of pelagic CaCO₃ production in a high CO₂ ocean: a model study

Abstract. This model study addresses the change in pelagic calcium carbonate production (CaCO₃, as calcite in the model) and dissolution in response to rising atmospheric CO₂. The parameterization of CaCO₃ production includes a dependency on the saturation state of seawater with respect to calcite. It was derived from laboratory and mesocosm studies on particulate organic and inorganic carbon production in Emiliania huxleyi as a function of pCO₂. The model predicts values of CaCO₃ production and dissolution in line with recent estimates. The effect of rising pCO₂ on CaCO₃ production and dissolution was quantified by means of model simulations forced with atmospheric CO₂ increasing at a rate of 1% per year from 286 ppm to 1144 ppm over a 140 year time-period. The simulation predicts a decrease of CaCO₃ production by 27%. The combined change in production and dissolution of CaCO₃ yields an excess uptake of CO₂ from the atmosphere by the ocean of 5.9 GtC over the period of 140 years.