1Laboratoire des Sciences du Climat et de l'Environnement, UMR8212, CNRS – Gif sur Yvette, France
2Laboratoire Jean Kuntzmann, Grenoble, France
3Laboratoire de Glaciologie et Geophysique de l'Environnement, CNRS-UJF, St. Martin d'Heres, France
4Institute of Speleology, Romanian Academy, Cluj-Napoca, Romania
5British Antarctic Survey, Cambridge, UK
6Arctic and Antarctic Research Institute, St. Petersburg, Russia
7Université catholique de Louvain, Earth and Life Institute, Georges Lemaître Center for Earth and Climate Research, Louvain-la-Neuve, Belgium
8Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
9Department of Chemistry Ugo Schiff, University of Florence, Florence, Italy
10Climate and Environmental Physics, Physics Institute and Oeschger Center for Climate Change Research, University of Bern, Bern, Switzerland
Received: 14 Nov 2012 – Discussion started: 30 Nov 2012
Abstract. An accurate and coherent chronological framework is essential for the interpretation of climatic and environmental records obtained from deep polar ice cores. Until now, one common ice core age scale had been developed based on an inverse dating method (Datice), combining glaciological modelling with absolute and stratigraphic markers between 4 ice cores covering the last 50 ka (thousands of years before present) (Lemieux-Dudon et al., 2010). In this paper, together with the companion paper of Veres et al. (2013), we present an extension of this work back to 800 ka for the NGRIP, TALDICE, EDML, Vostok and EDC ice cores using an improved version of the Datice tool. The AICC2012 (Antarctic Ice Core Chronology 2012) chronology includes numerous new gas and ice stratigraphic links as well as improved evaluation of background and associated variance scenarios. This paper concentrates on the long timescales between 120–800 ka. In this framework, new measurements of δ18Oatm over Marine Isotope Stage (MIS) 11–12 on EDC and a complete δ18Oatm record of the TALDICE ice cores permit us to derive additional orbital gas age constraints. The coherency of the different orbitally deduced ages (from δ18Oatm, δO2/N2 and air content) has been verified before implementation in AICC2012. The new chronology is now independent of other archives and shows only small differences, most of the time within the original uncertainty range calculated by Datice, when compared with the previous ice core reference age scale EDC3, the Dome F chronology, or using a comparison between speleothems and methane. For instance, the largest deviation between AICC2012 and EDC3 (5.4 ka) is obtained around MIS 12. Despite significant modifications of the chronological constraints around MIS 5, now independent of speleothem records in AICC2012, the date of Termination II is very close to the EDC3 one.
Revised: 24 Jun 2013 – Accepted: 25 Jun 2013 – Published: 01 Aug 2013
Bazin, L., Landais, A., Lemieux-Dudon, B., Toyé Mahamadou Kele, H., Veres, D., Parrenin, F., Martinerie, P., Ritz, C., Capron, E., Lipenkov, V., Loutre, M.-F., Raynaud, D., Vinther, B., Svensson, A., Rasmussen, S. O., Severi, M., Blunier, T., Leuenberger, M., Fischer, H., Masson-Delmotte, V., Chappellaz, J., and Wolff, E.: An optimized multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120–800 ka, Clim. Past, 9, 1715-1731, doi:10.5194/cp-9-1715-2013, 2013.