Precise dating of the 8.2 kyr event provides evidence for global climate response

Abstract

The 8.2 kyr event was the most pronounced Holocene cooling seen in Greenland ice cores and is one of the Global boundary Stratigraphic Points (GSSPs) subdividing the Holocene epoch. It is believed to be caused by the sudden drainage of North American proglacial lakes affecting the Atlantic Meridional Overturning circulation. The event had a profound impact on North Atlantic Climate and the global monsoon system while its impact beyond the Northern Hemisphere is less clear. Here, we provide a precise synchronization between Greenland and Antarctic ice cores around the 8.2 event via volcanic tie-points. Using the global production rate variations of cosmogenic radionuclides (10Be in ice cores and 14C in tree-rings) we then anchor the event on the absolutely dated tree-ring timescale. This allows us to precisely and absolutely date this GSSP at the site where it has been formally defined (i.e., Greenland Ice Cores), circumventing the uncertainty of the Greenland Ice Core timescale, and compare its age to independent estimates from U-Th-dated speleothems. Based on these findings, we provide evidence for a global impact of the 8.2 kyr event beyond the Northern Hemisphere and discuss the its propagation around the globe and its impact on Holocene climate dynamics.