Seasonal Variability of Sea Surface Salinity in the NW Gulf of Guinea from SMAP Satellite
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Date
2022
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Remote Sensing in Earth Systems Sciences
Abstract
The advent of satellite-derived sea surface salinity (SSS) measurements has boosted scientific
study in less-sampled ocean regions such as the northwestern Gulf of Guinea (NWGoG). In this
study, we examine the seasonal variability of SSS in the NWGoG from the Soil Moisture Active
Passive (SMAP) satellite and show that it is well-suited for such regional studies as it is able to
reproduce the observed SSS features in the study region. SMAP SSS bias, relative to in-situ data
comparisons reflects the differences between skin layer measurements and bulk-surface
measurements that have been reported by previous studies. The study results reveal three broad
anomalous SSS features: a basin-wide salinification during boreal summer, a basin-wide
freshening during winter and a meridionally-oriented frontal system during other seasons. A salt
budget estimation suggests that seasonal SSS variability is dominated by changes in freshwater
flux, zonal circulation and upwelling. Freshwater flux, primarily driven by the seasonally varying
Intertropical Convergence Zone is a dominant contributor to salt budget in all seasons except
during fall. Regionally, SSS is most variable off southwestern Nigeria and controlled primarily by
westward extensions of the Niger River. Anomalous salty SSS off the coasts of Cote d’Ivoire and
Ghana, especially during the summer, is driven mainly by coastal upwelling and horizontal advection.
Description
Research Article
Keywords
Gulf of Guinea, Sea Surface Salinity, Upwelling