Under usual conditions, the Western Equatorial Pacific is characterized by a low heat content on the equator and a maximum one west of 170E. After the appearance of EI Nino, this maximum is replaced by another one located in the Central South Pacific; this feature has been observed in 1972-73 but also in 1957-58 and 1976-77. The mechanism involves probable change of the mixed layer depth.
Henin, Christian, and Jean-René Donguy. 1980. "Heat content changes within the mixed layer of the Equatorial Pacific Ocean." Journal of Marine Research 38, (4). https://elischolar.library.yale.edu/journal_of_marine_research/1529