HR: 15:25h
AN: U23A-08 INVITED     [Abstracts]
TI: ``Pre-Vostok'' Greenhouse Gas Concentrations Reconstructed From the EPICA Dome C Ice Core
AU: * Stocker, T F
EM: stocker@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Bern, 3012 Switzerland
AU: Siegenthaler, U
EM: siegenthaler@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Bern, 3012 Switzerland
AU: Spahni, R
EM: spahni@climate.unibe.ch
AF: Climate and Environmental Physics, Physics Institute, University of Bern, Bern, 3012 Switzerland
AU: Chappellaz, J
EM: chappellaz@lgge.obs.ujf-grenoble.fr
AF: Laboratoire de Glaciologie et G\'eophysique de l'Environnement, 54, rue Moli\`ere, St. Martin d'H\`eres, 38402 France
AU: Fischer, H
EM: hufischer@awi-bremerhaven.de
AF: Alfred Wegener Institut f\"ur Polarforschung, Columbusstrasse, Bremerhaven, 27568 Germany
AB: The new deep ice core recovered from Dome Concordia in the framework of EPICA, the European Project of Ice Coring in Antarctica, contains a continuous climate history of the past 740,000 years [EPICA Community Members, 2004]. We present the current status of measurements of CO$_2$, CH$_4$ and N$_2$O on air trapped in the bubbles of the Dome C ice core. CO$_2$ is measured using laser absorption spectroscopy on samples of less than 10 g of ice which are mechanically crushed or milled. CH$_4$ and N$_2$O are extracted using a melt-refreeze technique and then measured by gas chromatography. The ice core contains an uncontaminated climate record down to Marine Isotope Stage 14 (MIS 14) as verified by a consistent gas age/ice age difference determined at terminations V and VI. CO$_2$ and CH$_4$ results from MIS 11 show that the normal levels of greenhouse gases prevailed during this exceptionally long interglacial. This demonstrates that the length of the interglacial was not due to exceptionally high greenhouse gas levels. MIS 13 and earlier interglacials, however, show significantly colder interglacials. In addition, the glacials are shorter which results in a more balanced sequence of cold and warm phases. Measurements of the greenhouse gas concentrations are central in understanding the mechanisms in the climate system which cause the significant change of character of the ice age cycles at around 400 kyr BP. We will present greenhouse gas measurements covering the first of the "pre-Vostok" interglacials from MIS 11 to MIS 14 (410 to 550 kyr BP) for CO$_2$, and from MIS 11 to MIS 16 (410 to 620 kyr BP) for CH$_4$. These measurements will resolve the "EPICA Challenge" [Wolff et al., 2004] put out to modelers to predict the expected greenhouse gas levels prior to 400 kyr BP based on the knowledge of the orbital parameters, and known paleoclimatic proxies (sea level from marine sediment records, dust load and isotopic concentration of precipitation in Antarctica from the EPICA Dome C ice core). \scriptsize EPICA Community Members, {\it Nature, 429}, 623-628, 2004. Wolff, E.W., et al., {\it EOS; Trans.\ Am.\ Geophys.\ Un.}, in press, 2004.
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1600 GLOBAL CHANGE (New category)
SC: Union [U]
MN: 2004 AGU Fall Meeting