THE FLICKERING SWITCH OF LATE PLEISTOCENE CLIMATE CHANGE

POLAR ice contains a unique record of past climate variations; previous Greenland ice cores have documented relatively warm 'interstadial' periods during the last glaciation and short (century-scale) returns to colder conditions during the glacial to interglacial warming (see, for example, ref. 1). These climate features have also been observed to varying degrees in ocean sediment cores2-4 and terrestrial pollen and insect records5-7. Here we report electrical conductivity measurements from a new Greenland ice core, which confirm these previous observations, and also reveal a hitherto unrecognized mode of rapid climate variation. Fluctuations in ice conductivity on the scales of <5-20 years reflect rapid oscillations in the dust content of the atmosphere. This 'flickering' between two preferred states would seem to require extremely rapid reorganizations in atmospheric circulation.