• journal_title：Geology
• Contributor：Cristiano M. Chiessi ; Stefan Mulitza ; André Paul ; Jürgen Pätzold ; Jeroen Groeneveld ; Gerold Wefer
• Publisher：Geological Society of America
• Date：2008-
• Format：text/html
• Language：en
• Identifier：10.1130/G24979A.1
• journal_abbrev：Geology
• issn：0091-7613
• volume：36
• issue：12
• firstpage：919

The North Atlantic Ocean underwent an abrupt temperature increase of 9 °C at high latitudes within a couple of decades during the transition from Heinrich event 1 (H1) to the Bølling 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 (δ¹⁸Osw) for the subtropical South Atlantic. We identify a warming of ~6.5 °C and an increase in δ¹⁸O_sw of 1.2‰ at the permanent thermocline during the transition, and a simultaneous warming of ~3.5 °C with no significant change in δ¹⁸O_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 (H1) and strong (Bølling) Atlantic meridional overturning circulation (AMOC). However, this zonal seesaw explains an increase of just 0.3‰ in permanent thermocline δ¹⁸O_sw. Considering that δ¹⁸O_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 Agulhas leakage took place at the transition from H1 to the Bølling, and was responsible for the change in δ¹⁸O_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 Bølling warm event.