Abstract
Antarctic ice cores show that a millennial-scale coolingevent, the Antarctic Cold Reversal (14,700 to 13,000 yearsago), interrupted the last deglaciation1–3. The Antarctic ColdReversal coincides with the Bølling–Allerød warm stage in theNorth Atlantic, providing an example of the inter-hemisphericcoupling of abrupt climate change generally referred toas the bipolar seesaw4–9. However, the ocean–atmospheredynamics governing this coupling are debated10–15. Here weexamine the extent and expression of the Antarctic ColdReversal in the Southern Hemisphere using a synthesis of84 palaeoclimate records.We find that the cooling is strongestin the South Atlantic and all regions south of 40 S. Atthe same time, the terrestrial tropics and subtropics showabrupt hydrologic variations that are significantly correlatedwith North Atlantic climate changes. Our transient globalclimate model simulations indicate that the observed extent ofAntarctic Cold Reversal cooling can be explained by enhancednorthward ocean heat transport from the South to NorthAtlantic10, amplified by the expansion and thickening of seaice in the Southern Ocean. The hydrologic variations at lowerlatitudes result from an opposing enhancement of southwardheat transport in the atmosphere mediated by the Hadleycirculation. Our findings reconcile previous arguments aboutthe relative dominance of ocean5,10,11 and atmospheric14,15 heattransports in inter-hemispheric coupling, demonstrating thatthe spatial pattern of past millennial-scale climate changereflects the superposition of both.