Re-analysis of key evidence in the case for a hemispherically synchronous response to the Younger Dryas climatic event

摘要

A south-east Australian speleothem stable isotope record displaying an apparent cooling synchronous with the northern hemisphere Younger Dryas climate event (12.9-11.7 ka) has significantly influenced scientific thinking on the climatic response of the southern hemisphere following the Last Glacial Maximum. This is one of very few records displaying such a response, and yet the cooling was inferred from substantial extrapolation between just three uranium-series ages. Technological advances since then have produced major improvements in both the spatial resolution and the accuracy of uranium-series geochronologies. Re-analysis of this sample has yielded ages of 7.96±0.36 to 7.69±0.33 ka for the interval previously inferred to span the Younger Dryas, and reveals a substantial hiatus in deposition from 6.93±0.64 to 1.83±0.16 ka. These data not only refute the original evidence for an inter-hemispheric synchroneity of the Younger Dryas but also reject any evidence for neoglacial conditions at 3 ka.