Changes in the South Atlantic Dipole, relations with the Interdecadal Pacific Oscillation and impacts on South America

Abstract

Changes in physical features of the South Atlantic Ocean (SAO) have been observed over the last few decades as a result of anthropogenic climate change. As an example, the increase in Agulhas Leakage, the continental melting of Greenland and changes in wind-forced ocean circulation are factors associated with changes in the Atlantic Meridional Overturning Circulation (AMOC). Within this context, important means of ocean-atmosphere interaction on a climate scale, such as the main mode of coupled variability of the SAO, known as the South Atlantic Dipole (SAD), may also be subject to variations. This work aimed to investigate changes in the SAD over different phases of the Interdecadal Pacific Oscillation (IPO) since the 1950s and assess their impacts on the climate of South America during the austral summer. The main finding is a southward shift of the entire SAD pattern over the analyzed period, consistent with other observed oceanic and atmospheric changes attributed to global warming. Associated with that, a change from a tripole to a dipole pattern of precipitation anomalies was observed over the South American continent during summer. Besides, the SAD displayed an alternate relationship with IPO phases, with a positive (negative) correlation with Pacific Niño SST anomalies during the IPO negative (positive) phase.