Thermohaline variability of the western tropical Pacific during 1995-1998:On the erosion/reconstitution of the fresh pool

The thermohaline variability of the western tropical Pacific at an El Nino- Southern Oscillation (ENSO) timescale is investigated for the 1995-1998 ENS O period along three transects, relying mostly on thermosalinograph and exp andable bathythermograph data distributed along three cross-equatorial ship ping lines. The water masses crossing these transects are studied chronolog ically by using estimates of wind forcing and precipitation. Zonal advectio n tends to shift eastward (westward) the fresh pool of the western Pacific and the zonal salinity front at its eastern edge during an El Nino (a La Nm a) event. Because of increased wind stress at the beginning of an El Nino e pisode, the fresh pool can be destroyed by upwelling of saltier water and i ncreased evaporation. It is, however, reconstructed further on its way to t he east, by more favorable wind and precipitation conditions, This erosion/ reconstruction process is then discussed in relation to ENSO development.