PNNL

Abstract

The continuous oceanic uptake of anthropogenic CO2 changes the chemical composition of the marine realm resulting in a lowering of pH (ocean acidification). Recently, meso- cosm studies showed that marine organisms react to pH changes1, i.e. the concentration of dimethylsulfide (DMS), a biogenic sulfur compound, was significantly reduced in a high CO2 / low pH world2. As marine DMS emissions are the largest natural source for atmospheric sulfur, changes in the source strength could alter the Earth radiation budget. In this study we investigate the impact of ocean acidification on production and emission of marine DMS with an Earth System Model. At the end of the 21th century we find a decrease of global oceanic DMS emission by 7 % compared to 1860 due to CO2 induced climate warming and by 17 % due to the combined effects of ocean acidification and climate warming. The reduced marine sulfur emission due to ocean acidification can be transferred to an additional warming potential of +0.38 W/m2 or to an equilibrium temperature response of 0.21 to 0.45°C which adds up to the anthropogenic climate warming.