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Abstract
Two deep ice cores from central Greenland, drilled in the 1990s, have played a key
role in climate reconstructions of the Northern Hemisphere, but the oldest sections
of the cores were disturbed in chronology owing to ice folding near the bedrock. Here
we present an undisturbed climate record from a North Greenland ice core, which extends
back to 123,000 years before the present, within the last interglacial period. The
oxygen isotopes in the ice imply that climate was stable during the last interglacial
period, with temperatures 5 degrees C warmer than today. We find unexpectedly large
temperature differences between our new record from northern Greenland and the undisturbed
sections of the cores from central Greenland, suggesting that the extent of ice in
the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland.
This record shows a slow decline in temperatures that marked the initiation of the
last glacial period. Our record reveals a hitherto unrecognized warm period initiated
by an abrupt climate warming about 115,000 years ago, before glacial conditions were
fully developed. This event does not appear to have an immediate Antarctic counterpart,
suggesting that the climate see-saw between the hemispheres (which dominated the last
glacial period) was not operating at this time.