Tracking Spread of the Agulhas Leakage Into the Western South Atlantic
and Its Northward Transmission During the Last Interglacial
Abstract
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.