Anomalous flow below 2700 m in the EPICA Dome C ice core detected using δ 18 O of atmospheric oxygen measurements

• Main Authors: M. Leuenberger, U. Siegenthaler, A. Tisserand, R. Spahni, L. Panno, J.-M. Barnola, J. Jouzel, V. Masson-Delmotte, G. Durand, B. Lemieux-Dudon, F. Parrenin, G. B. Dreyfus
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2007
• Subjects: Environmental pollution; TD172-193.5; Environmental protection; TD169-171.8; Environmental sciences; GE1-350; EPICA; ice core
• Online Access: https://doaj.org/article/3c07e8b911b1413184eb2e1d671e1bd5

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 (δ 18 O of O 2 , noted δ 18 O atm ) and daily northern hemisphere summer insolation has been observed for the youngest four climate cycles. Here we use this relationship with new δ 18 O of O 2 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 δ 18 O atm 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 δ 18 O atm 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.