Oceanic Heat Content Variability and El Niño Cycles

Abstract

Tropical Pacific heat content variability is studied in the context of a linear dynamical model forced by observed winds in the period 1970?87. The results confirm the relationships between equatorial heat content, surface winds, and SST predicted by coupled models of ENSO, and are consistent with sea level observations during this period. It is found that the meridional transports at the western boundary generally act to oppose the tendency in equatorial heat content, but are more than compensated for by the interior transports. Such a scenario is consistent with the reflection of equatorial (long) Rossby waves, but not off-equatorial ones, suggesting a dominant role for the former. In agreement with previous studies, an interhemispheric exchange of heat content is found in association with the ENSO cycle. The structure of heat content and transport anomaly fields throughout a composite ENSO cycle is presented and discussed in the context of existing theories, which highlight the role of Rossby waves and western boundary reflections.