Southward migrations of the Atlantic Equatorial Currents during the Younger Dryas

Abstract

Previous studies suggested that a weakened Gulf Stream may have contributed to the Younger Dryas (YD) cold event, however the physical mechanism of the Gulf Stream weakening is unclear. Here, we utilize paired Mg/Ca and δ18O measurements of planktonic foraminifera from the northerly and southerly marine sediments in the middle Atlantic Ocean to reconstruct past changes in tropical surface ocean temperature and salinity over the past 14 ka. We demonstrate that during the YD the sea surface temperature (SST) at the northerly core (0°16′S) was up to 2.1–2.7°C cooler whereas the SST at the southerly core (14°53′S) was up to 0.8–1.6°C warmer than modern temperatures. The δ18O, salinity values, accumulation rates, and other hydrological elements at the northerly core all exhibit opposite patterns with those at the southerly core. The antiphased variations of the paleohydrological elements at the northerly and southerly cores suggest that the Atlantic Equatorial Currents shifted southward significantly from its present-day position during the YD, possibly resulting in a decrease of the Gulf Stream, in turn a cool Northern Hemisphere.