Impact of surface ocean acidification on the CO2 absorption rate

Acidification of the surface ocean due to increased absorption of CO2 from the atmosphere directly impacts the CO2 absorption rate. Current measurements and equilibrium chemistry models suggest that the oceans have absorbed approximately half of the extra CO2 added during the past 200 years, which has resulted in a pH decline of approximately 0.1 units, with acidification projections of up to approximately 0.7 pH units as a result of a six-fold increase in pre-industrial atmospheric CO2 levels. The impact of CO2 absorption on the pH of the surface ocean can easily be predicted using steadystate chemical equilibrium and charge and mass balance models. However, the impact of acidification on the rate of CO2 absorption and the variations of the absorption rate during CO2 absorption as a result of pH change are typically ignored in the literature. In this article, the impact of acidification of the surface ocean on the CO2 absorption rate is described using simple mathematical models. The models predict that the rate of CO2 absorption is enhanced with acidification consistent with the rate of increase of CO2 in the atmosphere.