S/SE Brazilian continental margin sea surface temperature and productivity changes over the last 50 kyr

Abstract

Off the S/SE Brazilian continental margin, the Brazil Current (BC) drives important oceanographic processes. Over the Deglacial time interval, this shallow current was influenced by the Atlantic Meridional Overturning Circulation (AMOC) at different timescales resulting in changes in sea surface temperature (SST) and primary productivity. In this work, a 50-kyr record retrieved from the upper slope of Santos Basin (NAP63–1, 24°30′10“ S, 44°11’28” W, 842 m) was utilized to evaluate SST and productivity changes based on planktonic foraminifera abundances and Globigerinoides ruber (albus) Mg/Ca ratios. Our results highlight that during Marine Isotopic Stage 3 (MIS 3), the SW Atlantic was marked by increased variability in SST and productivity related to South Atlantic Central Water upwelling during BC strengthening driven by episodic AMOC interruption events. As the AMOC weakened during MIS 2, the BC strengthened, and surface water productivity increased in the Brazilian margin. Towards MIS 1, SST progressively increased while productivity decreased because of a weaker BC as AMOC resumed its interglacial state. Our findings suggest that the previously observed Holocene antiphase relationship between AMOC and BC has been present since MIS 3.