Seasonal variation in total inorganic carbon and its controlling processes in surface waters of the western North Pacific subtropical gyre

• Published in: Marine chemistry 2001-07, Vol.75 (1), p.17-32
• Main Authors: Ishii, Masao, Inoue, Hisayuki Y, Matsueda, Hidekazu, Saito, Shu, Fushimi, Katsuhiko, Nemoto, Kazuhiro, Yano, Toshihiko, Nagai, Hideki, Midorikawa, Takashi
• Format: Article
• Language: English
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Geochemistry; Mineralogy; Net community production; North Pacific subtropical gyre; Pacific Ocean; Physical and chemical properties of sea water; Physics of the oceans; Seasonal variability; Silicates; Total inorganic carbon; Water geochemistry
• ISSN: 0304-4203; 1872-7581
• DOI: 10.1016/S0304-4203(01)00023-8

Seasonal variation in total inorganic carbon (TCO 2) in surface waters of the western North Pacific (137°–152°E) subtropical gyre was analyzed on the basis of measurements of TCO 2 and partial pressure of CO 2 ( pCO 2sw). The controlling processes including vertical mixing, horizontal advection, and net air–sea CO 2 transport, as well as biological activity, were quantified. The seasonal increase in normalized TCO 2 (NTCO 2) from autumn to winter, ranging from 19 to 37 μmol kg −1 in the northern part of the subtropical gyre between 24°N and 30°N, was predominantly accounted for by the upward supply of TCO 2 due to enhanced vertical mixing. The contribution of horizontal advection, estimated from monthly meridional NTCO 2 distributions and the monthly advection field of the Meteorological Research Institute (MRI)'s 3D-ocean general circulation model, was insignificant. Analyses of the mixed-layer NTCO 2 budget revealed that biological activity was playing an important role in the decrease in surface NTCO 2 from winter to summer. Annual net community production reached 48±19 gC m −2 between 24°N and 30°N, and 19±16 gC m −2 between 15°N and 23°N.