Sea Surface Salinity (SSS) data have been collected in the tropical Pa
cific Ocean since 1969. From this data set, relationships of SSS with
ENSO have been found in both the western and the eastern Pacific. Thes
e have mainly been associated with the presence of the ITCZ and equato
rial upwelling. In the Central South Tropical Pacific a surface salini
ty maximum is formed by a positive Evaporation-Precipitation balance w
hich undergoes seasonal and interannual variations. It is prolonged in
the west by a subsurface salinity maximum. During ENSO events, the su
rface and subsurface salinity maxima expand westward. Initially, the s
ubsurface salinity maximum is strengthened and shoals, but eventually
it is driven back eastward by the equatorial jet. Such changes in surf
ace and subsurface salinity need to be included in the scenario of an
El Nino event.