Towards orbital dating of the EPICA Dome C ice core using δO2/N2
- 1Institut Pierre-Simon Laplace/Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ – UMR8212, 91191, Gif-sur-Yvette, France
- 2Department of Geosciences, Princeton University, Princeton, NJ 08540, USA
- 3Université catholique de Louvain, Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research (TECLIM), Chemin du cyclotron, 2, 1348 Louvain la Neuve, Belgium
- 4Laboratoire de Glaciologie et Géophysique de l'Environnement, CNRS-UJF, 38402 St. Martin d'Hères, France
- 5Arctic and Antarctic Research Institute, 38 Bering street, St. Petersburg 199397, Russia
- 6Climate and Environmental Physics, Physics Institute, and Oeschger Centre for Climate Change Research, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
- *now at: Oak Ridge Institute for Science and Education Climate Change Policy and Technology Fellow with the US Department of Energy Office of Policy and International Affairs, 1000 Independence Avenue SW, Washington, DC 20585, USA
- **now at: British Antarctic Survey, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
- ***These authors contributed equally to this work.
Abstract. Based on a composite of several measurement series performed on ice samples stored at −25 °C or −50 °C, we present and discuss the first δO2/N2 record of trapped air from the EPICA Dome C (EDC) ice core covering the period between 300 and 800 ka (thousands of years before present). The samples stored at −25 °C show clear gas loss affecting the precision and mean level of the δO2/N2 record. Two different gas loss corrections are proposed to account for this effect, without altering the spectral properties of the original datasets. Although processes at play remain to be fully understood, previous studies have proposed a link between surface insolation, ice grain properties at close-off, and δO2/N2 in air bubbles, from which orbitally tuned chronologies of the Vostok and Dome Fuji ice core records have been derived over the last four climatic cycles. Here, we show that limitations caused by data quality and resolution, data filtering, and uncertainties in the orbital tuning target limit the precision of this tuning method for EDC. Moreover, our extended record includes two periods of low eccentricity. During these intervals (around 400 ka and 750 ka), the matching between δO2/N2 and the different insolation curves is ambiguous because some local insolation maxima cannot be identified in the δO2/N2 record (and vice versa). Recognizing these limitations, we restrict the use of our δO2/N2 record to show that the EDC3 age scale is generally correct within its published uncertainty (6 kyr) over the 300–800 ka period.