Interhemispheric air temperature phase relationships in the nonlinear Dansgaard-Oeschger oscillation

Abstract

It has previously been suggested that the Southern Ocean might act as a thermal reservoir in mediating the relationship between the northern and southern hemisphere air temperature signals during a Dansgaard-Oeschger cycle. On the basis of a climate model-based analysis, we demonstrate on the contrary that it is equatorial and subtropical North Atlantic thermocline waters that act so as to integrate and damp the northern hemisphere signal to fix the amplitude and phase of the southern hemisphere counterpart to the more intense North Atlantic component of the oscillation. The dynamics of the Southern Ocean component of the Atlantic meridional overturning circulation are critical in explaining the evolution of the interhemispheric temperature phase relationships. European Project for Ice Coring in Antarctica Dronning Maud Land-inferred air temperature variations are in phase with sea surface temperatures north of the Antarctic sea ice edge, suggesting that it is via a fast atmospheric pathway that this temperature signal is transmitted into the Antarctic ice core record.