Saline Indian Ocean waters invaded the South Atlantic thermocline during glacial termination II

Salty and warm Indian Ocean waters enter the South Atlanticvia the Agulhas leakage, south of Africa. Model simulations andproxy evidence of Agulhas leakage strengthening during glacial terminationsled to the hypothesis that it was an important modulator ofthe Atlantic Ocean circulation. Yet, the fate of the leakage salinity andtemperature anomalies remains undocumented beyond the southerntip of Africa. Downstream of the leakage, new paleoceanographicevidence from the central Walvis Ridge (southeast Atlantic) showsthat salinity increased at the thermocline, and less so at the surface,during glacial termination II. Thermocline salinity change coincidedwith higher frequency of Agulhas rings passage at the core locationand with salinity maxima in the Agulhas leakage area, suggesting thatleakage waters were incorporated in the Atlantic circulation throughthe thermocline. Hydrographic changes at the Walvis Ridge and inthe leakage area display a distinct two-step structure, with a reversalat ca. 134 ka. This matched a wet interlude within the East Asia weakmonsoon interval of termination II, and a short-lived North Atlanticwarming. Such concurrence points to a Bølling-Allerød-like recoveryof the Atlantic circulation amidst termination II, with a northwardshift of the Intertropical Convergence Zone and Southern Hemispherewesterlies, and attendant curtailment of the interocean connectionsouth of Africa.