Equatorial sea level response during the 1982–1983 El Niño

Abstract

During the 1982–83 El Niño/Southern Oscillation event, sea level across the width of the equatorial Pacific adjusted to the reversal of the equatorial trade winds, and by the end of 1982 the normal sea level slope across the Pacific had been eliminated. The transfer of warm upper‐ocean water from the western Pacific to the eastern Pacific was accomplished by a combination of direct wind forcing as the wind anomaly crossed the basin and by mass flux induced by free equatorial waves. The importance of equatorially trapped Kelvin waves of first and second vertical mode during the onset of the 1982–83 El Niño is inferred from the cross‐correlation statistics between central and eastern Pacific sea level stations and between wind variations in the western Pacific and equatorial sea level stations to the east. The different propagation speeds of these two modes appears to be responsible for the observed change inshape of the major sea level signals during the 1982–83 event. Tentative evidence for first baroclinic mode, first meridional‐mode Rossby waves is also presented.