The Relationship Between Fluctuations in Sea Level, Wind Stress and Sea Surface Temperature in the Equatorial Pacific

Abstract

Correlations among sea level, wind stress and sea surface temperature at various lags have been used to determine the relationship between these parameters in the Pacific equatorial region 10°N to 10°S. Seasonal sea level in the coastal upwelling region depends on the magnitude of the meridional component of the southeast trade. Seasonal sea level along and south of the equator (to about 110°W) depends mainly on the temperature of water advected from the coastal upwelling region. Seasonal sea level in mid-ocean is mainly a function of the degree of set-up by the zonal component of the local wind stress. In the Countercurrent trough, seasonal sea level varies inversely with the magnitude of the local meridional shear except in spring when it is directly proportional to set-up by the zonal component of the northeast trade. Year-to-year sea level fluctuations from about 4°N to 10°S in the eastern half of the ocean are caused primarily by fluctuations in the temperature of water advected away from the coastal upwelling region. Year-to-year sea level fluctuations in the Countercurrent trough are caused by fluctuations in the strength of local meridional shear. An inverse relationship between year-to-year fluctuations in sea level in the Countercurrent trough and in the eastern ocean from 4°N to 10°S is explained in terms of the dependence of the meridional shear in the Countercurrent region on sea surface temperature in the equatorial ocean. A detailed description of the signature of an El Niño event on sea level, wind stress and sea surface temperature fields is given, as well as the manner in which such an event is forced.