Abstract
Based on satellite surface salinity (SSS) observations from the SMOS, Aquarius and SMAP missions, we investigate the interannual SSS variability during the period from 2010 to 2020 in the Gulf of Guinea, impacted by the Congo River run-off. Combined with in situ data, the available 11 years of satellite salinity data suggest that the plume of Congo run-off primarily spreads into western directions, leading to reduced SSS. A fraction of it also shows a coastal southward extent subject to interannual variability influenced by coastal trapped waves. The low-salinity water is associated with high values of net primary production, confirming the riverine origin of the nutrient rich plume. No correlation can be found between the plume patterns and the different upwelling strengths in the subsequent upwelling months, nor could a correlation be found with the occurrence of the Benguela Niños. Linking the occurrence of a barrier layer to the occurrence of low-salinity plumes remains difficult, mainly because of the sparseness of in situ data. However, the influence of the low-salinity layer is evident in its stronger stratification and an increased available potential energy.
Highlights
The region off the southwestern coast of Africa is one of the world’s most productive eastern boundary upwelling regions (EBUS)
High-resolution models may help in this respect; most models use a relaxation to climatological salinity, which itself suffers from the lack of data and does not present the realistic salinity variability
We used satellite-derived sea-surface salinity data to expand our knowledge about sea-surface variability off the coast of Africa, where we studied the variability of the Congo-River-induced freshwater plume and its interannual variability over the period from 2010 to 2020
Summary
The region off the southwestern coast of Africa is one of the world’s most productive eastern boundary upwelling regions (EBUS) In this region, the interannual variability of the near-surface surface temperature field, exceeding 2◦ C above or below the seasonal mean, known as Benguela Niños or Niñas [1,2] (and references therein), weakens or enhances the strength of the upwelling. The interannual variability of the near-surface surface temperature field, exceeding 2◦ C above or below the seasonal mean, known as Benguela Niños or Niñas [1,2] (and references therein), weakens or enhances the strength of the upwelling On interannual timescales, these temperature anomalies have been shown to be remotely forced by equatorial Kelvin waves, which travel along the equatorial wave guide to the east after their genesis by subsequently relaxing western equatorial winds and propagate poleward as coastally trapped waves (CTW) along the coast of Africa. Several previous studies mention the existence of a dispersion of low-salinity plumes away from the
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