The surface fCO2 distribution of the western North Pacific in summer 2002

Abstract

We measured the fugacity of CO2 (fCO2), temperature, salinity, nutrients and chlorophyll a in the surface water of the western North Pacific (4°30′∼33°′N, 144°20′∼127°35′E) in September 2002. There were zonally several major currents which have characteristics of specific temperature and salinity (NECC, North Equatorial Counter Current; NEC, North Equatorial Current; Kuroshio etc.). Surface fCO2 distribution was clearly distinguished into two groups, tropical and subtropical areas of which boundary was 20°N. In the tropical area, surface fCO2 was mainly controlled by temperature, while in the subtropical area, surface fCO2 was dependent on total inorganic carbon contents. Air-sea CO2 flux showed a large spatial variation, with a range of -0.69∼0.79 mmole m-2 day-1. In the area of AE (Anticyclonic Eddy), SM (Southern Mixed region) and NM (Northern Mixed region), the ocean acted as a weak source of CO2 (0.6∼0.79 mmole m-2 day-1). In NECC, NEC, Kuroshio and ECS (East China Sea), however, the fluxes were estimated to be -0.3 mmole m-2 day-1 for the first three regions and -1.2 mmole m-2 day-1 for ECS respectively, indicating that these areas acted as sinks of CO2. The average air-sea flux in the entire study area was 0.15 mmole m-2 day-1, implying that the western North Pacific was a weak source of CO2 during the study period.