Bifurcation of the North Equatorial Current derived from altimetry in the Pacific Ocean*

The gridded (1/3°*1/3°) altimetry data from October 1992 through December 2004 were analyzed to study the seasonal and interannual variabilities of the bifurcation of the North Equatorial Current (NEC) at the surface in the western North Pacific Ocean. Calculations show that on annual average the bifurcation occurs at about 13.4°N at the surface. The geostrophic flow derived from Sea Surface Height (SSH) data shows that the southernmost latitude of the NEC bifurcation at the surface is about 12.9°N in June and the northernmost latitude is about 14.1°N in December. Correlation analyses between the bifurcation latitude and the Southern Oscillation Index (SOI) suggest that the bifurcation latitude is highly correlated with the El Niño/Southern Oscillation (ENSO) events. During the El Niño years the bifurcation of the NEC takes place at higher latitudes and vice versa.