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 glaci al period show abrupt temperature changes on timescales of a few hundr ed years, which have been attributed to cycles of ice build-up and rel ease associated with large ice sheets (Dansgaard-Oeschger cycles and H einrich events)(3) and their coupling to ocean circulation(4,5). But l ittle is known about the dynamics of the atmosphere during the last gl aciation. Ice sheets influence atmospheric circulation, and studies us ing 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-resolutio n ice-core record from Greenland(1,2). This analysis provides direct e vidence that atmospheric circulation during the last glaciation was mo re turbulent than it is today.