Analyzing the 2019 Atlantic Niño signature in the tropical Atlantic sea surface salinity using coupled reanalysis assimilating satellite and in-situ temperature and salinity

This study investigates the impact of the 2019 Atlantic Niño on sea surface salinity (SSS) variability in the tropical Atlantic during the mature phase of event using coupled reanalysis data that assimilate SST, T-S profiles, and SSS. Two regions with pronounced sea surface salinity anomalies (SSSA) were identified: the northern equatorial Atlantic (NEA) and the southeastern Atlantic (SEA). In NEA, positive SSSA are primarily driven by freshwater flux, especially the anomalous precipitation, in response to the movements of the Intertropical Convergence Zone (ITCZ), while ocean dynamics play a secondary role. In SEA, negative SSS anomalies are mostly induced by the advection impacts of offshore currents and vertical mixing, and river runoff anomalies also contribute significantly. These findings highlight the distinct mechanisms driving SSS changes in the northern and southern tropical Atlantic and demonstrate the importance of coupled reanalysis data in improving the understanding of air-sea interactions in these regions.