Investigation of the causes of historical changes in the subsurface salinity minimum of the South Atlantic

Abstract

In this study, we investigate the subsurface salinity changes on decadal timescales across the subtropical South Atlantic Ocean using two ocean reanalysis products, the latest version of the Simple Ocean Data Assimilation and the Estimating the Circulation and Climate of the Ocean, Phase II, as well as using additional climate model experiments. Results show that there is a recent significant salinity increase at the core of the salinity minimum at intermediate levels. The main underlying mechanism for this subsurface salinity increase is the lateral advective (gyre) changes due to the Southern Annular Mode variability, which conditions an increased contribution from the Indian Ocean high salinity waters into the Atlantic. The global warming signal has a secondary but complementary contribution. Latitudinal differences at intermediate depth in response to large-scale forcing are in part caused by local variation of westward propagation features, and by compensating contributions of salinity and temperature to density changes.