1. Niels Bohr Institute for Astronomy, Physics and Geophysics, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen OE, Denmark;
2. Nagaoka University of Technology, 1603-1 Kamitomioka-machi, Nagaoka 940-2188, Japan;
3. Laboratoire de Glaciologie et Géophysique de l'Environnement (CNRS), BP 96, 38402 St Martin d'Héres Cedex, France;
4. Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, CH-3012, Switzerland;
5. Lamont-Doherty Earth Observatory of Columbia University, Rte 9W - PO Box 1000, Palisades, New York 10964-8000, USA;
6. Institute Pierre Simon Laplace/ Laboratoire des Sciences du Climat et de l'Environnement, UMR CEA-CNRS, CE Saclay, Omme des Merisiers, 91191 Gir-Sur-Yvette, France;
7. Alfred-Wegener-Institute for Polar and Marine Research (AWI), Postfach 120161, D-27515 Bremerhaven, Germany;
8. National Institute of Polar Research, Kaga 1-9-10, Itabashi-ku, Tokyo 173-8515 Japan;
9. Nordic Volcanological Institute, Grensásvegur 50, 108 Reykjavik, Iceland;
10. Department of Physical Geography and Quaternary Geology, Stockholm University, S-106 91, Stockholm, Sweden;
11. Département des Sciences de la terre et de l'Environnement, Faculté des Sciences, CP 160/03, Université Libre de Bruxelles, 50 avenue FD Roosevelt, B1050 Brussels, Belgium;
12. Research Institute for Humanity and Nature, 335 Takashima-cho, Marutamachi-dori Kawaramachi nishi-iru, Kamigyo-ku, Kyoto 602-0878, Japan;
13. INSTAAR, Campus Box 450, University of Colorado, Boulder, Colorado 80309-0450, USA;
14. Kitami Institute of Technology, Koencho 165, Kitami, Hokkaido 090-8507 Japan;
15. Raunvísindastofnun Háskólans, Dunhagi 3, Iceland;
16. National Energy Authority, Grensásvegur 9, IS-108 Reykjavík, Iceland
17. Deceased

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 °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.

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