South Atlantic interocean exchange as the trigger for the Bolling warm event

The North Atlantic Ocean underwent an abrupt temperature increase of 9 degrees C at high latitudes within a couple of decades during the transition from Heinrich event 1 (H1) to the Bolling warm event, but the mechanism responsible for this warming remains uncertain. Here we address this issue, presenting high-resolution last deglaciation planktic and benthic foraminiferal records of temperature and oxygen isotopic composition of seawater (delta O-18(sw)) for the subtropical South Atlantic. We identify a warming of similar to 6.5 degrees C and an increase in delta O-18(sw) of 1.2%omicron at the permanent thermocline during the transition, and a simultaneous warming of -3.5 degrees C with no significant change in delta O-18(sw) at intermediate depths. Most of the warming can be explained by tilting the South Atlantic east-west isopycnals from a flattened toward a steepened position associated with a collapsed (H 1) and strong (Bolling) Atlantic meridional over-turning circulation (AMOC). However, this zonal seesaw explains an increase of just 0.3%omicron in permanent thermocline delta O-18(sw). Considering that delta O-18(sw) at the South Atlantic permanent thermocline is strongly influenced by the inflow of salty Indian Ocean upper waters, we suggest that a strengthening in the Agullhas leakage took place at the transition from H1 to the Bolling, and was responsible for the change in delta O-18(sw) recorded in our site. Our records high-light the important role played by Indian-Atlantic interocean exchange as the trigger for the resumption of the AMOC and the Bolling warm event.