C. Henin et al., OBSERVATIONS OF SEA-SURFACE SALINITY IN THE WESTERN PACIFIC FRESH POOL - LARGE-SCALE CHANGES IN 1992-1995, J GEO RES-O, 103(C4), 1998, pp. 7523-7536
This paper investigates the variability of sea surface salinity (SSS)
in the western equatorial Pacific fresh pool. For this purpose, we pro
cessed data collected from thermosalinographs embarked on merchant shi
ps. Two main cross-equatorial shipping lines that are representative o
f the oceanic conditions in the western tropical Pacific were selected
: the Japan-Tarawa-Fiji line that crosses the equator near 173 degrees
E (eastern track) and the New-Caledonia-Japan line that crosses the e
quator near 156 degrees E (western track). We show that there is a str
ong SSS variability in the region at monthly as well as interannual ti
mescales. This high variability is attributed to the successive passag
es of a zonal salinity front, trapped in the [5 degrees N-5 degrees S]
equatorial band and migrating in phase with the southern oscillation
index. We also found the eastern track to be more variable in SSS beca
use it is more exposed to these SSS front incursions. We carried out a
detailed study of the mechanisms responsible for this variability; it
revealed that the rainfall input acts as a source of freshwater respo
nsible for the existence of a contrasted distribution of SSS (mainly h
igh-salinity waters in the central Pacific and low-salinity waters in
the western Pacific). However, the main mechanism responsible for the
SSS variability is zonal advection that makes the two distinct masses
of water converge, resulting in a salinity front which shifts back and
forth in the equatorial band.