THE SEA-SURFACE SALINITY IN THE TROPICAL ATLANTIC BETWEEN 10-DEGREES-S AND 30-DEGREES-N - SEASONAL AND INTERANNUAL VARIATIONS (1977-1989)

The seasonal and interannual variations of the Sea Surface Salinity (SSS) are analysed in the tropical Atlantic (15-degrees-S-30-degrees-N, 80-degrees-W-15-degrees-E) from observations collected by merchant ships between 1977 and 1989 and earlier by ORSTOM research vessels. The harmonic analysis of SSS shows a well defined seasonal cycle both within a 5-degrees-N-15-degrees-N zonal belt and west of 50-degrees-W at higher latitudes. In the eastern Atlantic between 10 and 20-degrees-N (along the shipping lanes West Africa-South Africa and West Africa-Brazil), SSS increased from 1977 to 1985, particularly near 10-degrees-N. SSS variability is mostly related to the river outflow (Amazon, Orinoco and Congo) west of 40-degrees-W and in southern Gulf of Guinea. In the eastern Atlantic, precipitation associated with the ITCZ largely control the SSS seasonal variations.