Interhemispheric climate links revealed by a late-glacial cooling episode in southern Chile

Abstract

Understanding the relative timings of climate events in the Northern and Southern hemispheres is a prerequisite for determining the causes of abrupt climate changes. But climate records from the Patagonian Andes^1,2,3,4 and New Zealand^5,6,7,8 for the period of transition from glacial to interglacial conditions—about 14.6–10 kyr before present, as determined by radiocarbon dating—show varying degrees of correlation with similar records from the Northern Hemisphere. It is necessary to resolve these apparent discrepancies in order to be able to assess the relative roles of Northern Hemisphere ice sheets and oceanic, atmospheric and astronomical influences in initiating climate change in the late-glacial period. Here we report pollen records from three sites in the Lake District of southern Chile (41° S) from which we infer conditions similar to modern climate between about 13 and 12.2 ¹⁴C kyr before present (bp), followed by cooling events at about 12.2 and 11.4 ¹⁴C kyr bp, and then by a warming at about 9.8 ¹⁴C kyr bp. These events were nearly synchronous with important palaeoclimate changes recorded in the North Atlantic region⁹, supporting the idea that interhemispheric linkage through the atmosphere was the primary control on climate during the last deglaciation. In other regions of the Southern Hemisphere, where climate events are not in phase with those in the Northern Hemisphere, local oceanic influences may have counteracted the effects that propagated through the atmosphere.