Coccolithophore growth and calcification in an acidified ocean: Insights from Community Earth System Model simulations

However, several oceanic regions show large increases in calcification, such as the North Atlantic, Western Pacific, and parts of the Southern Ocean, due to an alleviation of carbon limitation for coccolithophore growth. Global annual calcification is 6% higher under present-day CO2 levels relative to preindustrial CO2 (1.5 compared to 1.4 Pg C/year). However, under 900 � atm CO2, global annual calcification is 11% lower than under preindustrial CO2 levels (1.2 Pg C/year).

Large portions of the ocean show greatly decreased coccolithophore calcification relative to growth, resulting in significant regional carbon export and air-sea CO2 exchange feedbacks. Our study implies that coccolithophores become more abundant but less calcified as CO2 increases with a tipping point in global calcification (changing from increasing to decreasing calcification relative to preindustrial) at approximately ≤600 ğ�œ‡ atm CO2.