Surface and subsurface Agulhas Leakage dynamics across Termination V and MIS 11

The glacial termination that occurred approximately 430 thousand years ago (i.e., Termination V) culminated in the interglacial known as Marine Isotope Stage 11 (MIS 11). During this period, Earth’s mean temperature was approximately 2°C warmer than the pre-industrial era. Therefore, it makes an excellent case study for investigating the response of key components of the climate system under global warming conditions. Warm and saline (sub)surface waters from the Indian Ocean enter the South Atlantic through its southeastern sector via the so-called Agulhas Leakage (AL), thereby influencing the heat and salt content of the basin. Variations in the intensity of the AL are thought to play a key role in modulating the strength of the Atlantic Meridional Overturning Circulation on orbital and millennial timescales. However, the scarcity of high-resolution paleoceanographic records hampers detailed investigations of AL variability during Termination V and MIS 11. Here, we assess changes in AL across this time interval based on planktonic foraminiferal assemblages, as well as Mg/Ca ratios and stable oxygen isotopic ratios of surface and subsurface planktonic foraminiferal species (i.e., Globigerinoides ruber (white) and Globorotalia truncatulinoides (sinistral)). Our results allow us to reconstruct AL faunal index, a proxy for AL intensity, and associate (sub)surface temperature and salinity changes. Altogether, the records suggest an increase in AL intensity across Termination V. Interestingly, millennial-scale subsurface signals display a delayed response of up to ~6 thousand years relative to surface conditions. Although the mechanism underlying this decoupling remain unclear, it suggests that additional processes may have influenced subsurface oceanographic variability during this key climatic interval.