Potential buffering capacity of naturally distributed carbonate minerals against future rises in atmospheric CO and coastal acidification: the Yellow Sea and three major estuaries in China.

The dissolution of marine carbonate minerals represents a scalable carbon dioxide (CO) removal approach toward global climate goals. In this study, potential buffering capacity of naturally distributed carbonate minerals against future rises in atmospheric CO and thereby coastal acidification were assessed using field data obtained in the Bohai Sea, Yellow Sea and Chinese major estuaries. Results showed that highly soluble carbonate minerals such as calcite and aragonite dominated surface sediments, constituting 8-12 % of dry weight of sediments in Chinese major estuaries, while lowly soluble carbonate minerals (mostly dolomite) accounted for <1.5 %. At a conservative estimate, the South Yellow Sea particulate inorganic carbon (PIC) pool west of 124 °E in the region can potentially convert 21 × 10 mol CO (equivalent to 0.9 Mt CO or 0.25 Tg C) into bicarbonate. If the atmospheric CO further rises in the future, the Yellow Sea represents one of the most vulnerable systems within the Chinese seas to adverse impacts from ocean acidification. Based on the projection of CaCO saturation states under the future atmospheric CO rise, Yellow Sea aragonite pools will dissolve sooner than calcite pools. However, the future projection suggests that the air-equilibrated Ω will not decline to 2.0-2.1 in the Yellow Sea by the 2050s, implying that the South Yellow Sea's calcite pool may not play an important role in buffering the atmospheric CO rise.