Simulated CO2-induced ocean acidification for ocean in the East China: historical conditions since preindustrial time and future scenarios

Since preindustrial times, as atmospheric CO2 concentration increases, the ocean continuously absorbs anthropogenic CO2, reducing seawater pH and [CO32-], which is termed ocean acidification. We perform Earth system model simulations to assess CO2-induced acidification for ocean in the East China, one of the most vulnerable areas to ocean acidification. By year 2017, ocean surface pH in the East China drops from the preindustrial level of 8.20 to 8.06, corresponding to a 35% rise in [H+], and reduction rate of pH becomes faster in the last two decades. Changes in surface seawater acidity largely result from CO2-induced changes in surface dissolved inorganic carbon (DIC), alkalinity (ALK), salinity and temperature, among which DIC plays the most important role. By year 2300, simulated reduction in sea surface [CO32-] is 13% under RCP2.6, contrasted to 72% under RCP8.5. Furthermore, simulated results show that CO2-induced warming acts to mitigate reductions in [CO32-], but the individual effect of oceanic CO2 uptake is much greater than the effect of CO2-induced warming on ocean acidification. Our study quantifies ocean acidification induced by anthropogenic CO2, and indicates the potentially important role of accelerated CO2 emissions in projections of future changes in biogeochemistry and ecosystem of ocean in the East China.