Response of South Atlantic deep waters to deglacial warming during Terminations V and I

New deep-sea core data from the Atlantic sector of the Southern Ocean. covering MIS12 to MIS10 and the last deglaciation, show a clear lag of the changes in deep water properties with respect to changes in surface conditions. The development of a chronology based on the correlation of Southern Ocean sea surface temperature with air temperature over Antarctica allows the quantification and comparison of phase lags within the Marine records during Termination V (TV) and Termination I (TI). Deglacial changes in the South Atlantic are interpreted as the response to changes in the state of the Atlantic meridional ocean circulation (AMOC). The warming of South Atlantic surface waters and air temperature over Antarctica at the beginning of both TV and TI is attributable to a reduction in interhemispheric heat transport due to the weakening of the AMOC. Comparison of our results with CLIMBER-2 simulations indicates that the response of bottom waters seen in the benthic isotopic records, delayed with respect to South Atlantic surface warming, can be explained by the increased inflow of North Atlantic Deep Water (NADW) to the South Atlantic site at the time of the AMOC recovery. Reconstructed sea surface temperature at our South Atlantic site exhibits a cold spell at the end of TV, resembling the Antarctic Cold Reversal of the last deglaciation. The presence of cold spells during TV and TI may be explained by the fact that the recovery of the AMOC took place early during the termination in both cases. The sequence of events is similar during both terminations; however, the magnitude of the phase shifts between South Atlantic surface and deep waters conditions differs from one termination to the other, suggesting variations in the magnitude and duration of the AMOC perturbation. (c) 2010 Elsevier B.V. All rights reserved.