We present new high resolution, well dated, foraminiferal delta 18O records from the extratropical southern hemisphere (ODP Site 1233; 41 degrees S, 74 degrees W) which reveal that both the physical properties of the surface and intermediate ocean covary with Antarctic climate during Termination 1. This synchrony between polar and mid latitude climate changes demonstrates that large regions of the southern hemisphere vary in antiphase with the abrupt changes observed in North Atlantic climate across the termination. Furthermore, our benthic delta 18O records show that the Antarctic surface climate signal extends into the intermediate ocean suggesting that the temperature of the southern hemisphere thermocline, a large thermal reservoir, also varies out of phase with North Atlantic climate. We argue that the clear antiphase between the upper ocean heat content in the southern hemisphere and climate in the North Atlantic strongly supports changes in interhemispheric heat transport related to ocean circulation as a mechanism for the Younger Dryas cooling.