Sea surface salinity variability in response to the Congo river discharge

A strong correlation is found between month-to-month variations in upper ocean salinity (as revealed by Aquarius satellite and Argo observations) and month-to-month variations in the freshwater discharge from the Congo River over a region off the coast of West Africa that is large enough to be easily observed by the Aquarius satellite. Vertical profiles of salinity derived from Argo floats reveal that these freshwater anomalies can be traced to 30 m below the sea surface. Combining the spatial area characterized by strong negative correlations between Aquarius SSS data and Congo discharge with the Argo vertical profiles of salinity, the volume of the freshwater anomalies is inferred and used to estimate the Congo River discharge. Reasonably good agreement is found between the Congo River discharge as observed by a stream gauge at Brazzaville and that estimated from the combined Aquarius and Argo data, especially during the freshening portion of the seasonal cycle (during this phase the correlation is 0.84, implying ~70% of the variance can be explained). The precipitation minus evaporation portion of the freshwater flux is found to play a secondary role in this region.