Spatial variability of surface fCO2 in the western North Pacific during summer 2007

Abstract

In order to study spatial variabilities and major controlling factors, we measured fugacity of CO2 (fCO2), temperature, salinity and nutrients in surface waters of the North Pacific (7°30′∼33°15′N, 123°56′E∼164°24′W) between September∼October 2007. The North Pacific and the marginal sea were distinguished by fCO2 distribution as well as unique characteristics of temperature and salinity. There was a distinct diurnal SST variation in the tropical North Pacific area, and surface fCO2 coincidently showed diurnal variation. In the North Pacific area, surface fCO2 was mainly controlled by temperature, while in the marginal sea area it was primarily dependent on alkalinity and dissolved inorganic carbon concentrations. Air-sea CO2 flux showed a large spatial variation, with a range of -6.10∼5.06 mmol m-2 day-1. The center of subtropical gyre of North Pacific acted as a source of CO2 (3.09±0.95 mmol m-2 day-1). Tropical western North Pacific (i.e. the 'warm pool' area and the subtropical western North Pacific) acted as weak sources of CO2 (1.07±1.20 mmol m-2 day-1 and 0.50±0.53 mmol m-2 day-1 respectively). In the marginal sea, however, the flux was estimated to be -0.68±1.17 mmol m-2 day-1, indicating that this area acted as a sink for CO2.