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

Abstract

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 (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.

Volcanic synchronisation between the EPICA Dome C and Vostok ice cores (Antarctica) 0–145 kyr BP

“…4b) ranges from ∼0.05 m to ∼0.75 m, EDC96 recording similar events at slightly deeper depths compared to EDC99. The depth difference remains largely confined between 0.1 and 0.3 m down to 600 m. The small oscillations in this depth interval are probably due to spatial irregularities of snow deposition/re-deposition (sastrugi, Ekaykin et al, 2002;Barnes et al, 2006); the logging uncertainty could indeed only contribute a systematic error of order <1 mm per 2.2 m. Between 600 and 790 m, the depth difference increases to ∼0.7 m, probably due to logging differences between the two cores. Indeed, the 600 m depth corresponds to the start of the brittle zone at EDC.…”

“…While climate models and meteorological observations and reanalyses confirm a coherency of inter-annual to decadal temperature fluctuations on the east Antarctic Plateau (Masson-Delmotte et al, 2011), the intermittency of precipitation (Sime et al, 2009;Stenni et al, 2010;Laepple et al, 2011) and the local elevation changes (MassonDelmotte et al, 2011;Siddall et al, 2012) may induce sitespecific isotopic signals. Superimposed on this depositional variability, post-depositional processes linked to wind erosion and depth propagation of surface height variability are known to induce noise in isotopic profiles, even at the local scale (Ekaykin et al, 2002). Finally, uncertainties in ice core isotopic synchronisation arise from different sampling resolutions.…”

“…orbital tuning) (e.g. Waelbroeck et al, 1995;Dreyfus et al, 2007;Kawamura et al, 2007); (ii) wiggle matching of ice core records to other dated paleo-archives such as ice, marine or terrestrial cores (e.g. Blunier and Brook, 2001;Waelbroeck et al, 2008); (iii) identification of dated horizons such as tephra layers, sulfate spikes or cosmogenic radionuclides spikes (e.g.…”

Phase relationships between orbital forcing and the composition of air trapped in Antarctic ice cores

“…The most closely related ice core parameter is δ 18 O atm , δ 18 O of atmospheric O 2 . Ice core records of δ 18 O atm are strongly correlated with variations of insolation in the precession band, with a lag assumed to be ∼ 5-6 ka as established for the last termination (glacial-interglacial transition, Bender et al, 1994;Jouzel et al, 1996;Petit et al, 1999;Shackleton et al, 2000;Dreyfus et al, 2007). The modulation of δ 18 O atm by precession operates through the biosphere productivity and changes in low-latitude water cycle (Bender et al, 1994;Malaizé et al, 1999;Wang et al, 2008;Severinghaus et al, 2009;Landais et al, 2007Landais et al, , 2010.…”

“…Because of these complex interactions, the lag between δ 18 O atm and precession should vary with time (Leuenberger, 1997;Jouzel et al, 2002). However, for dating purposes, this lag has been assumed to be constant with an uncertainty of a quarter of a precession cycle (6 ka; Jouzel et al, 1996;Parrenin et al, 2001Parrenin et al, , 2007Dreyfus et al, 2007).…”