SPATIAL AND TEMPORAL VARIATIONS OF SURFACE SEAWATER F(CO2) IN THE KUROSHIO OFF JAPAN

To examine the annual growth rate of CO2 in the ocean, spatial and tem poral variations of the fugacity of CO2 (f(CO2)) in surface seawater i n the Kuroshio off Japan were surveyed, using the data obtained by the Japan Meteorological Agency in the period 1989-1995. Winter surface s eawater f(CO2), decreased distinctly in the south of the Kuroshio fron t, where sea surface temperature increased sharply. In other seasons, such a large spatial variability at the Kuroshio front was rarely foun d. The temporal variation in surface seawater f(CO2) at the selected a rea could be expressed by a rather simple function consisting of annua l and bi-annual harmonics and a linear trend. The seasonal variation h as a sharp maximum peak in summer, but an indistinct minimum peak in t he period from winter to spring. The annual growth rate was 1.5 mu atm /yr, significant at the 95% level. The seasonal variation reproduced a ssuming a thermodynamic dependence of surface seawater f(CO2) on water temperature and salinity explains only about similar to 24% of the ob served seasonal variation. (C) 1998 Elsevier Science B.V.