Interannual variability in the mid- and low-latitude western North Pacific

Twenty-two years (1967-88) of hydrographic data along the 137 degree E meridian and surface wind data were analyzed to study the interannual variability in the western North Pacific. In the midlatitude region north of 22 degree N, the dominant signal in the dynamic height field was the interannual path variations of the Kuroshio. Whereas the eastward transport of the Kuroshio itself had no significant changes between the straight-path and meander-path years, the net transport of the Kuroshio system including recirculations showed a 30% increase during the meander-path years. In the straight-path years when the net transport was small, the Kuroshio tended to take a straight path with a strong recirculation developed to the south. In the low-latitude region along 137 degree E, fluctuations in the surface height anomaly field had a meridionally coherent structure. Accompanying the surface height drops in the ENSO years was an increase in the transport of both the North Equatorial Current (NEC) and the North Equatorial Countercurrent (NECC) and a southward shift in the boundary of the NEC and NECC. We found that these interannual fluctuations of the NEC and the NECC highly correlated to the Sverdrup transport fluctuations estimated from the basinwide wind-stress curl field.