Exploring seasonal acidification in the Yellow Sea

The Yellow Sea on the western continental margin of the North Pacific Ocean is of major ecological and economic importance. Four field surveys were conducted during May and November 2012, August 2015, and January 2016, investigating seasonal variations in dissolved oxygen and carbonate system parameters of this marginal sea. Results showed that the Yellow Sea cold water mass accumulated respiration-induced CO 2 in subsurface and bottom waters in summer and autumn, leading to acidified seawaters with critical carbonate saturation states of aragonite (Ω arag ) of less than 1.5. These seriously acidified seawaters occupied one third of surveyed areas in summer and autumn, likely affecting local calcified organisms and benthic communities. In a future scenario for the 2050s, in which the atmospheric CO 2 mole fraction increases by 100 μmol mol −1 , half of the Yellow Sea benthos would be seasonally covered by acidified seawater having a critical Ω arag of less than 1.5. The corresponding bottom-water pHT would be around 7.85 in summer, and 7.80 in autumn. Of the China seas, the Yellow Sea cold water mass represents one of the ecosystems most vulnerable to ocean acidification.