CPD Climate of the Past Discussions CPD 1814-9359 Copernicus GmbH Göttingen, Germany 10.5194/cpd-6-1895-2010 Deep ocean ventilation, carbon isotopes, marine sedimentation and the deglacial CO<sub>2</sub> rise Tschumi T. 1 Joos F. 1 2 Gehlen M. 3 Heinze C. 4 Climate and Environmental Physics, Physics Institute, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland Oeschger Centre for Climate Change Research, University of Bern, 3012 Bern, Switzerland Laboratoire du Climat et de l'Environnement (LSCE), L'Orme des Merisiers Bât. 712, 91191 Gif-sur-Yvette, France University of Bergen, Geophysical Institute & Bjerkness Centre for Climate Research, Allegaten 70, 5007 Bergen, Norway 27 09 2010 6 5 1895 1958 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.clim-past-discuss.net/6/1895/2010/cpd-6-1895-2010.html The full text article is available as a PDF file from http://www.clim-past-discuss.net/6/1895/2010/cpd-6-1895-2010.pdf

The link between the atmospheric CO<sub>2</sub> level and the ventilation state of the deep ocean is an important building block of the key hypotheses put forth to explain glacial-interglacial CO<sub>2</sub> fluctuations. In this study, we systematically examine the sensitivity of atmospheric CO<sub>2</sub> and its carbon isotope composition to changes in deep ocean ventilation, the ocean carbon pumps, and sediment formation in a global three-dimensional ocean-sediment carbon cycle model. Our results provide support for the hypothesis that a break up of Southern Ocean stratification and invigorated deep ocean ventilation were the dominant drivers for the early deglacial CO<sub>2</sub> rise of ~35 ppm between the Last Glacial Maximum and 14.6 ka BP. Another rise of 10 ppm until the end of the Holocene is attributed to carbonate compensation responding to the early deglacial change in ocean circulation. Our reasoning is based on a multi-proxy analysis which indicates that an acceleration of deep ocean ventilation during the early deglaciation is not only consistent with recorded atmospheric CO<sub>2</sub> but also with the reconstructed opal sedimentation peak in the Southern Ocean at around 16 ka BP, the record of atmospheric &delta;<sup>13</sup>C<sub>CO<sub>2</sub></sub>, and the reconstructed changes in the Pacific CaCO<sub>3</sub> saturation horizon.

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