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The South Atlantic subtropical dipole is the dominant mode of coupled variability in the South Atlantic, connecting sea level pressure and sea surface temperature. Previous studies have shown its great relevance to the climate conditions over South America and West Africa. We have used several numerical experiments with the Hybrid Coordinate Ocean Model to investigate the effects that an austral winter–spring dipole asserts on the South Atlantic. We explore the interaction between SST anomalies and the formation of the fossilized mixing region, which preserve temperature anomalies underneath the summer mixed layer, until they feed back to SST after the next autumn. It was found that, through this process, there is a memory effect that restores temperature anomalies from an austral winter–spring dipole back to the austral winter of the following year. The dominant mechanisms are the contribution from entrainment and surface net heat flux (NHF). Entrainment is mostly controlled by vertical temperature gradient anomalies, while surface NHF is controlled by interactions of climatological ocean heat loss and anomalies of mixed layer thickness. Our results suggest that the combined effect of entrainment and surface NHF is different in the southwest and northeast dipole regions, leading to differences in both intensity and timing of SST anomalies. Turbulent and nonlinear processes are most important to reduce entrainment in the southwest dipole region and to increase the memory effect asymmetry.

The role that the Indonesian Throughflow plays on climate is investigated in an alternative scenario, expected during glacial ages. The equatorwards shift of the Southern Hemisphere westerlies found in glacial ages acts to decrease the Agulhas Leakage (AL) and the thermohaline circulation (THC) in the Atlantic. Recent results suggest that these changes are followed by an increased THC in the Pacific, through an inter‐basin seesaw mechanism. The enhanced circulation in the Pacific demands thermocline water to cross the equator towards northern latitudes, which shifts the water source of the throughflow from the low‐salinity North Pacific to the relative saltier South Pacific. It is shown that in this equilibrium, the salinity anomalies of the throughflow impact the inter‐basin seesaw towards the restoration of the modern climate, enhancing the North Atlantic Deep Water (NADW) formation and decreasing the THC in the Pacific. These results are consistent with paleo‐observations and provide new insights to interpreting the climate changes in glacial periods.

<p>The spatiotemporal evolutions of sea surface salinity measurements from the SMOS satellite reveal presence of a local salinity maximum in the northwestern tropical Atlantic beginning in September increasing with a Maximum in October and disappearing in January. Its structure and variability are analyzed through SMOS SSS daily products derived with advanced techniques developed at the Barcelona Expert Centre during 9 years. The results are compared with in situ data along the North Brazil Current (NBC) from the Prediction and Research moored Array in the Tropical Atlantic - PIRATA program. This seasonal tropical SSS maximum, produces the salty signature Northward of the NBC, which is seen as a localized salinity maximum on satellite imagery, in contrast to the fresh signature present in summer-early fall. These changes suggest a change in the composition of water masses that enter in the South Atlantic contributing to an alteration in the dynamics of global circulation.</p>