Decadal changes in the equatorial Pacific circulation

Abstract

An ocean general circulation model with data assimilation is used to analyze the decadal changes in the tropical Pacific Ocean circulation. Results indicate that the variability in the Equatorial Undercurrent (EUC) and subtropical cells (STC) have a strong relationship to the variability of the zonal wind stress of the tropical Pacific Ocean. The EUC volume transport gradually declined from the 1960's to the 1990's as a response to the overall zonal wind stress forcing across the equatorial Pacific. In contrast, the STC weakened abruptly in 1976, thus responding rapidly to the abrupt weakening in the zonal wind stress associated with a large climatic shift. The results indicate that the tropical Pacific Ocean responds to forcing on multiple time scales, which is important in determining the mechanism that controls decadal variability in the Pacific Ocean.