Reconstructing bottom currents along the Brazilian margin from the Last Glacial Maximum to the Holocene

The deep ocean circulation during the last glacial cycle exhibited characteristics distinct from the Holocene. This interval marks the transition between glacial and interglacial conditions, strongly influenced by millennial-scale Heinrich events, which were characterized by massive iceberg discharges into the North Atlantic. Studies indicate that during these events, the AMOC became shallower and weaker, resulting in a pronounced reduction in deep ocean circulation across the Atlantic. In this study, we present three sediment cores: DGL-1914 (1131 m), DGL-1905 (2513 m) and DGL-1903 (2704 m), collected along the western Brazilian margin near the São Francisco River, spanning the last 40.000 years. To investigate variability in deep-current velocity, we applied the Sortable Silt proxy in combination with the Zr/Rb ratio, both indicators of paleocurrent strength.  Our results show that during Heinrich events (H1, H2, H3, and H4), significant changes occurred in current velocities, reflecting distinct hydrodynamic conditions associated with the Intermediate Western Boundary Current (IWBC) (core DGL-1914) and the Deep Western Boundary Current (DWBC) (cores DGL-1905 and DGL-1903). In particular, we observe a pronounced reduction in the DWBC flow during these events, indicating a weakening of the AMOC in the South Atlantic throughout these intervals. These results provide new insights into deep circulation in the western South Atlantic and contribute to a more comprehensive understanding of bottom-waters dynamics along the Brazilian margin.