Benthic stable oxygen and carbon isotope records; XRF scanner S and EDP XRF S, and foraminiferal assemblages of sediment core M125-95-3

Negative excursions in the stable carbon isotopic composition (δ¹³C) at Atlantic intermediate to mid-depths are common features of millennial-scale events named Heinrich Stadials (HS). The mechanisms behind these excursions are not yet fully understood, but most hypotheses agree on the central role played by the weakening of the Atlantic meridional overturning circulation. Marine records registering millennial-scale negative δ¹³C excursions in the Atlantic are mostly restricted to the HS of the last deglacial, while the HS of the last glacial are poorly studied. Here we constrain changes in bottom water ventilation in the western tropical South Atlantic mid-depth during HS of the last glacial and deglacial by investigating marine core M125-95-3. The concurrent decreases in benthic foraminifera δ¹³C and increases in bulk sediment sulfur indicates an increased Northern Component Water (NCW) residence time in the western tropical South Atlantic mid-depth during HS. Furthermore, a coherent meridional pattern emerges from the comparison of our new data to previously published mid-depth records from the western South Atlantic. While our record shows the largest negative δ¹³C excursions during almost all HS, the western equatorial Atlantic showed medium and the subtropical South Atlantic showed the smallest negative excursions. This meridional pattern supports the notion that during HS a reduction in the NCW δ¹³C source signal together with the accumulation of respired carbon at NCW depths drove the negative δ¹³C excursions. We suggest that the negative δ¹³C excursions progressively increase along the NCW southwards pathway until the signal dissipates/dilutes by mixing with Southern Component Water.