Eastern Brazil Hydroclimate Weakening Linked to Stronger AMOC During the Pleistocene

Several paleoclimate studies focus on the impacts of changes in Atlantic Meridional Overturning Circulation (AMOC) on the dynamics of the South American Monsoon System (SAMS) on millennial timescales; however, they lack interpretations on longer timescales throughout the Quaternary. Here, we present a sediment core covering the last 1 million years collected in the tropical region of the eastern Brazilian margin near the São Francisco River mouth. We used the ln(Si/Al) as hydroclimate proxy, interpreting as changes in the SAMS activity, and also δ¹³C of benthic foraminifera to track changes on deep-water circulation. We observed substantial changes between 700-400 ka, marked by the weakening of the SAMS simultaneously with increasing long-term trend of δ¹³C, suggesting a coupled ocean-atmosphere changes during this period. We infer that the observed increase in ventilation is a response to a stronger AMOC, which leads to a global northward migration of the Intertropical Convergence Zone (ITCZ), resulting in a decrease in SAMS intensity. Thus, our data offer insights into long-term coupled responses between the oceanic and atmospheric systems in the tropical realm during the Quaternary.