Carbonate chemistry and the anthropogenic CO2 in the South China Sea

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Carbonate chemistry and the anthropogenic CO2 in the South China Sea

In order to understand the water mass exchange between the South China Sea and the West Philippine Sea, and to study the dissolved carbonate system in the seas surrounding Taiwan Island, we participated in five WOCE cruises (Cruises 257, 262, 266, 287 and 316) aboard R/V Ocean Researcher 1.The areas studied were the South China Sea, the West Philippine Sea and the Bashi Channel.Temperature, salinity, pH, alkalinity and total CO₂ were measured.
Our data indicate that because of the interference of the submarine topography and the Kuroshio axis, there exists a 0front" south of the Lanyu Islet.East of it, the water mass belongs to the West Philippine Sea, on the west in the mixed water of the South China Sea and the West Philippine Sea.
The South China Sea deep water should have the characteristics similar to the water at about 2 200 m in the West Philippine Sea.The calculated results from the residence time, the inorganic carbon dissolution rate and the organic carbon decomposition rate show that the differences between these two water masses should be between 0.008-0.023 in pH, 5.2-15.0 μmol/kg in apparent oxygen utilization, 3.6-10.2 μmol/kg in alkalinity and 6.4-18.4 pmol/kg in total CO₂,respectively.The measured results show that there are no distinguishable differences between these two water masses, implying a short deep water residence time of approximately 40 a.
The anthropogenic CO₂ penetrates to roughly 500 m, slightly shallower than found in the West Philippine Sea.The entire South China Sea contains (0.38±0.1)×1015 g excess CO₂.