Oceanic heat content variability in the tropical Pacific during the 1982–1983 El Niño

Abstract

Anomalous heat transport and storage during the 1982–1983 El Niño are investigated using a linear, multimode model forced by observed winds. Heat transport is decomposed into symmetric (about the equator) and antisymmetric components. The former was dominated by anomalous northward Ekman transport which represented an enhancement of the usual seasonal cycle. The latter involved both Ekman and geostrophic transports. Near‐equatorial wind anomalies forced Kelvin and Rossby waves usually associated with El Niño; together these waves set up antisymmetric, geostrophic transport which tended to oppose direct Ekman transport. Because the opposition was imperfect, there was net heat convergence which caused variations in heat content in bands of latitude centered on the equator. Within a fairly narrow band (±5°) heat content was anomalously high preceding El Niño and was depleted following the event. Equatorial heat content anomalies were largely compensated by opposing anomalies in low latitudes of the extraequatorial ocean so that variability over broader bands of latitude about the equator was relatively small. A sampling study employing the model suggests that observational evidence for a heat content variations over the region ±15° is an artifact arising from inadequate spatial resolution offered by the sea level measurement network.