Anomalous flow below 2700 m in the EPICA Dome C ice core detected using δ18O of atmospheric oxygen measurements
- 1LSCE/IPSL, CEA-CNRS-UVSQ, CE Saclay, 91191, Gif-sur-Yvette, France
- 2Department of Geosciences, Princeton University, Princeton, New Jersey, USA
- 3Laboratoire de Glaciologie et Geophysique de l'Environnement (CNRS), St Martin d'Heres, France
- 4Niels Bohr Institute for Astronomy, Physics and Geophysics, University of Copenhagen, Copenhagen, Denmark
- 5Physics Institute, University of Bern, Bern, Switzerland
- 6Université Bordeaux I, UMR 5805 EPOC, Environnements et Paleoenvironnements Océaniques et Côtiers, Talence Cedex 33405, France
Abstract. While there are no indications of mixing back to 800 000 years in the EPICA Dome C ice core record, comparison with marine sediment records shows significant differences in the timing and duration of events prior to stage 11 (~430 ka, thousands of years before 1950). A relationship between the isotopic composition of atmospheric oxygen (δ18O of O2, noted δ18Oatm) and daily northern hemisphere summer insolation has been observed for the youngest four climate cycles. Here we use this relationship with new δ18O of O2 measurements to show that anomalous flow in the bottom 500 m of the core distorts the duration of events by up to a factor of 2. By tuning δ18Oatm to orbital precession we derive a corrected thinning function and present a revised age scale for the interval corresponding to Marine Isotope Stages 11–20 in the EPICA Dome C ice core. Uncertainty in the phasing of δ18Oatm with respect to insolation variations in the precession band limits the accuracy of this new agescale to ±6 kyr (thousand of years). The previously reported ~30 kyr duration of interglacial stage 11 is unchanged. In contrast, the duration of stage 15.1 is reduced by a factor of 2, from 31 to 16 kyr.