Importance of the Salinity Barrier Layer for the Buildup of El Nino

TLDR: In this article, the potential influence of vertical salinity stratification on the heat buildup and thus on El Nino was considered using sea level observations and coupled models, which revealed the concomitant presence of heat accumulation and a significant barrier layer in the western equatorial Pacific.

Abstract: Several studies using sea level observations and coupled models have shown that heat buildup in the western equatorial Pacific is a necessary condition for a major El Nino to develop. However, none of these studies has considered the potential influence of the vertical salinity stratification on the heat buildup and thus on El Nino. In the warm pool, this stratification results in the presence of a barrier layer that controls the base of the ocean mixed layer. Analyses of in situ and TOPEX/Poseidon data, associated with indirect estimates of the vertical salinity stratification, reveal the concomitant presence of heat buildup and a significant barrier layer in the western equatorial Pacific. This relationship occurs during periods of about one year prior to the mature phase of El Nino events over the period 1993–2002. Analyses from a coupled ocean–atmosphere general circulation model suggest that this relationship is statistically robust. The ability of the coupled model to reproduce a realistic ...