Contrasting atmospheric and climate dynamics of the last-glacial and Holocene periods

Our present climate is relatively stable compared to that of the Last Glacial Maximum about 20,000 years ago. Palaeoclimate records obtained from ice cores(1,2) and deep-sea sediment cores(3) for the last glacial period show abrupt temperature changes on timescales of a few hundred years, which have been attributed to cycles of ice build-up and release associated with large ice sheets (Dansgaard-Oeschger cycles and Heinrich events)(3) and their coupling to ocean circulation(4,5). But little is known about the dynamics of the atmosphere during the last glaciation. Ice sheets influence atmospheric circulation, and studies using general circulation models have suggested stormier, more variable atmospheric dynamics during the Last Glacial Maximum than today(6-9). Here we report the results of an analysis of temporal trends over the past 91,000 years in the oxygen isotope signatures of a high-resolution ice-core record from Greenland(1,2). This analysis provides direct evidence that atmospheric circulation during the last glaciation was more turbulent than it is today.