Summary
Ice core records from Antarctic and Greenland have revealed that the last deglaciation (ca. 19, 000 to 11, 000 years before present) was accompanied by an 80 ppmv increase in atmospheric CO2 and a sequence of large, hemispheric climate variations. Precise information on the relative timing of these north-south climate variations and their relation with the rise in CO2 is a key to resolving questions concerning the mechanisms which force and couple climate changes between the hemispheres. Here we present a series of records for the deglaciation: a proxy for regional Antarctic temperature derived from a composite of four high-dating-precision Antarctic ice cores; a proxy for regional Greenland temperature constructed from the North-Greenland ice core; and two ice core records of atmospheric CO2. All records are synchronised to the common Greenland Ice Core 2005 Chronology (GICC05), using dating ties provided by fast variations in global methane gas concentrations. We observe clear anti-phase behaviour between Antarctic and Greenland temperature. This pattern may be explained by shifts in the balance of meridional ocean heat flux between the hemispheres, consistent with the bipolar seesaw hypothesis. The deglacial CO2 rise is highly correlated with Antarctic temperature (r2 = 0.95 with Byrd CO2, r2 = 0.96 with Siple CO2). Detailed lag-correlation analysis, suggests that the deglacial CO2 rise lagged the Antarctic temperature rise by between 0-400 yr, which is substantially shorter and more tightly constrained than the most often cited previous estimate of 200-1400 y. The observed tight coupling between CO2 and Antarctic temperature lends support to the view that marine processes in the Southern Ocean played a central role in the CO2 rise during the deglaciation, while previous estimates of the lag suggest that the mechanism involved act on timescales around 1000 yr, our results require that the mechanisms involved act on centennial timescales or less.