Marine sediments from the Western and Eastern South Atlantic continental margins are used to reconstruct mercury (Hg) accumulation over the last glacial/interglacial cycle. Sediment core GL-1248, collected from the continental slope off northeastern Brazil, and sediment core ODP1077, retrieved from the Congo deep-sea fan area, both dated to the last 128 ka and 130 ka respectively. Mercury concentrations in GL-1248 ranged between 14.95 and 69.43ng/g, and varied with periodicities of 56 ka and 900 yr suggesting the presence of glacial-interglacial changes and millennial-scale variability respectively. Parallel trends of Hg and XRF-Fe plots suggest that following atmospheric Hg deposition onto the continent, Hg is incorporated with iron (Fe) minerals before transportation and eventual immobilization at the NE Brazil continental slope. Mercury concentrations in ODP1077 varied significantly, having concentrations between 23.12 ng/g and 256 ng/g, and its plot exhibits an anti-phase pattern with the Fe/Ca ratio plot, that distinguishes between periods of increased and decreased terrigenous material delivery. This inverse trend in the plots of mercury concentration and Fe/Ca ratio shows that during periods of increased (decreased) terrigenous material delivery, less (more) mercury accumulates in the marine sediment. Although Hg concentration is poorly correlated with total organic carbon (TOC), it correlates positively with XRF-Ca implying that marine organic matter played a significant role in mercury distribution and accumulation in the ODP1077 marine sediment core. Despite the fact that both marine sediment cores were retrieved from the tropics and cover the same glacial/interglacial periods, their mercury variations and the main drivers of mercury accumulations are dissimilar. Accordingly, we identified two different pathways by which mercury is incorporated into marine sediments for prolonged storage and inclusion in the global mercury biogeochemical cycle. The outcome of this study suggests that regional climate processes and geochemical conditions are essential to Hg variations in environmental archives. Another obvious finding is that the source of sedimentary organic carbon is a key determinant of their affinity for mercury.

Intensification of the Agulhas Leakage (AL) during glacial terminations has long been proposed as a necessary mechanism for reverting the Atlantic Meridional Overturning Circulation (AMOC) to its interglacial mode. However, lack of records showing the downstream evolution of AL signal and substantial temporal differences between AL intensification and resumption of deep‐water convection have cast doubt on the importance of this mechanism to the AMOC. Here, we analyze a combination of new and previously published data relating to Mg/Ca‐derived temperatures and ice volume‐corrected seawater δ18O records (δ18OIVC‐SW, as a proxy for relative changes in ocean salinity), which demonstrate propagation of AL signal via surface and thermocline waters to the western South Atlantic (Santos Basin) during Termination II and the early Last Interglacial. The saline AL waters were temporally stored in the upper subtropical South Atlantic until they were abruptly released in two stages into the North Atlantic via surface and thermocline waters at ca. 129 and 123 ka BP, respectively. Accounting for age model uncertainties, these two stages are coeval with the resumption of convection in the Labrador and Nordic seas during the Last Interglacial. We propose a mechanism whereby both active AL and a favorable ocean‐atmosphere configuration in the tropical Atlantic were required to allow flux of AL waters into the North Atlantic, where they then contributed to enhancing the AMOC during the Last Interglacial period. Our results provide a framework that connects AL strengthening to the AMOC intensifications that followed glaciations.