Nearly synchronous climate change in the Northern Hemisphere during the last glacial termination

The climate of the North Atlantic region underwent a series of abrupt cold/warm oscillations when the ice sheets of the Northern Hemisphere retreated during the last glacial termination (17.7-11.5 kyr ago). Evidence for these oscillations, which are recorded in European terrestrial sediments as the Oldest Dryas/Bolling/ Older Dryas/Allerod/Younger Dryas vegetational sequence(1,2), has been found in Greenland ice cores(3,4). The geographical extent of many of these oscillations is not well known(5,6), but the last major cold event (the Younger Dryas) seems to have been global in extent(7-10). Here we present evidence of four major oscillations in the hydrological balance of the Owens basin, California, that occurred during the last glacial termination. Dry events in western North America occurred at approximately the same time as cold events recorded in Greenland ice, with transitions between climate regimes in the two regions taking place within a few hundred years of each other. Our observations thus support recent climate simulations which indicate that cooling of the North Atlantic Ocean results in cooling of the North Pacific Ocean(11) which, in turn, leads to a drier climate in western North America(12).