Opposite-Sign Sea Surface Salinity Anomalies Over the Northeastern and Southwestern South Atlantic Ocean From 2010 to 2017

Abstract

Using seven sea surface salinity (SSS) data sets, the dominant modes of interannual SSS variability over the South Atlantic Ocean are examined for the period 2010–2017, which features strong anomalies (>0.1 g/kg). The empirical orthogonal function analysis and composite analysis are used, and the results show that the South Atlantic Ocean features opposite-sign SSS anomalies over the southwestern (45°–20°S/40°–60°W) and northeastern (0°–15°E/0°–15°S) regions. SSS budget analyses based on the Estimating the Circulation and Climate of the Ocean model estimate suggest that horizontal advection promotes the opposite-sign SSS anomalies over the two regions. The interannual changes in the horizontal advection can be attributed to changes in the advection of mean salinity by the anomalous horizontal flow, in which the Ekman velocities play the dominant role. The anomalous wind stress and sea level pressure patterns suggest that the opposite SSS variations in poles A and B are probably associated with atmospheric forcings under alternating Atlantic Nino and Benguela Nina conditions. This study offers a connection in interannual SSS variations over two remote regions within the South Atlantic Ocean and suggests the possible role of the climate mode in setting up interannual salinity anomalies over the South Atlantic Ocean.