The glacial inception as recorded in the NorthGRIP Greenland ice core: timing, structure and associated abrupt temperature changes |
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| Authors: | Amaelle Landais Valérie Masson-Delmotte Jean Jouzel Dominique Raynaud Sigfus Johnsen Christof Huber Markus Leuenberger Jakob Schwander Bénédicte Minster |
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| Institution: | (1) IPSL/Laboratoire des Sciences du Climat et de l’Environnement, UMR CEA-CNRS, CEA Saclay, 91191 Gif-sur -Yvette, France;(2) LGGE, UMR CNRS-UJF, 2 −53 Rue Molière, 38 402 St Martin d’Heres, France;(3) Department of Geophysics, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark;(4) Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland;(5) Institute of Earth Sciences, Hebrew University, Givat Ram, 91904 Jerusalem, Israel |
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| Abstract: | The mechanisms involved in the glacial inception are still poorly constrained due to a lack of high resolution and cross-dated
climate records at various locations. Using air isotopic measurements in the recently drilled NorthGRIP ice core, we show
that no evidence exists for stratigraphic disturbance of the climate record of the last glacial inception (∼123–100 kyears
BP) encompassing Dansgaard–Oeschger events (DO) 25, 24 and 23, even if we lack sufficient resolution to completely rule out
disturbance over DO 25. We quantify the rapid surface temperature variability over DO 23 and 24 with associated warmings of
10±2.5 and 16±2.5°C, amplitudes which mimic those observed in full glacial conditions. We use records of δ18O of O2 to propose a common timescale for the NorthGRIP and the Antarctic Vostok ice cores, with a maximum uncertainty of 2,500 years,
and to examine the interhemispheric sequence of events over this period. After a synchronous North–South temperature decrease,
the onset of rapid events is triggered in the North through DO 25. As for later events, DO 24 and 23 have a clear Antarctic
counterpart which does not seem to be the case for the very first abrupt warming (DO 25). This information, when added to
intermediate levels of CO2 and to the absence of clear ice rafting associated with DO 25, highlights the uniqueness of this first event, while DO 24
and 23 appear similar to typical full glacial DO events. |
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