%0 Journal Article
%T Subsurface low pH and carbonate saturation state of aragonite on China side of the North Yellow Sea: combined effects of global atmospheric CO2 increase, regional environmental changes, and local biogeochemical processes
%A W.-D. Zhai
%A N. Zheng
%A C. Huo
%A Y. Xu
%J Biogeosciences Discussions
%D 2013
%I Copernicus Publications
%R 10.5194/bgd-10-3079-2013
%X Based upon seven field surveys conducted between May 2011 and January 2012, we investigated pH, carbonate saturation state of aragonite (次arag), and ancillary parameters on the Chinese side of the North Yellow Sea, a western North Pacific continental margin of major economic importance. Subsurface waters were nearly in equilibrium with air in May and June. From July to October, the fugacity of CO2 (fCO2) of bottom water gradually increased to 697 ㊣ 103 米atm and pH decreased to 7.83 ㊣ 0.07 due to respiration/remineralization processes of primary production induced biogenic particles. In November and January, bottom water fCO2 decreased and pH gradually returned to an air-equilibrated level due to cooling enhanced vertical mixing. The corresponding bottom water 次arag was 1.74 ㊣ 0.17 (May), 1.77 ㊣ 0.26 (June), 1.70 ㊣ 0.26 (July), 1.72 ㊣ 0.33 (August), 1.32 ㊣ 0.31 (October), 1.50 ㊣ 0.28 (November), and 1.41 ㊣ 0.12 (January). Critically low 次arag values of 1.0 to 1.2 were mainly observed in subsurface waters in a salinity range of 31.5每32.5 psu in October and November, accounting for ~ 10% of the North Yellow Sea area. Water mass derived from the adjacent Bohai Sea had a typical water salinity of 30.5每31.5 psu, and bottom water 次arag values ranged mostly between 1.6 and 2.4. This study showed that the carbonate system in the North Yellow Sea was substantially influenced by global atmospheric CO2 increase. The community respiration/remineralization rates in typical North Yellow Sea bottom water mass were estimated at 0.55每1.0 米mol O2 kg 1 d 1 in warm seasons, leading to seasonal drops in subsurface pH and 次arag. Outflow of the Bohai Sea water mass counteracted the subsurface 次arag reduction in the North Yellow Sea.
%U http://www.biogeosciences-discuss.net/10/3079/2013/bgd-10-3079-2013.pdf