Is there 1.5-million-year-old ice near Dome C, Antarctica?

Frédéric Parrenin,Duncan A Young,Marie G P Cavitte,Jason Roberts,Catherine Ritz,Jérôme Chappellaz,Martin J Siegert,Donald D Blankenship,Hubertus Fischer,Valérie Masson-Delmotte,Olivier Passalacqua,Olivier Gagliardini

doi:10.5194/tc-11-2427-2017

Abstract

Abstract. Ice sheets provide exceptional archives of past changes in polar climate, regional environment and global atmospheric composition. The oldest dated deep ice core drilled in Antarctica has been retrieved at EPICA Dome C (EDC), reaching ∼ 800 000 years. Obtaining an older paleoclimatic record from Antarctica is one of the greatest challenges of the ice core community. Here, we use internal isochrones, identified from airborne radar coupled to ice-flow modelling to estimate the age of basal ice along transects in the Dome C area. Three glaciological properties are inferred from isochrones: surface accumulation rate, geothermal flux and the exponent of the Lliboutry velocity profile. We find that old ice (> 1.5 Myr, 1.5 million years) likely exists in two regions: one ∼ 40 km south-west of Dome C along the ice divide to Vostok, close to a secondary dome that we name Little Dome C (LDC), and a second region named North Patch (NP) located 10–30 km north-east of Dome C, in a region where the geothermal flux is apparently relatively low. Our work demonstrates the value of combining radar observations with ice flow modelling to accurately represent the true nature of ice flow, and understand the formation of ice-sheet architecture, in the centre of large ice sheets.

Highlights

Since around 800 000 years ago, glacial periods have been dominated by a ∼ 100 000-year cyclicity, as documented in multiple proxies from marine, terrestrial and ice core records (Elderfield et al, 2012; Jouzel et al, 2007; Lisiecki and Raymo, 2005; Loulergue et al, 2008; Lüthi et al, 2008; Wang et al, 2008; Wolff et al, 2006)
We developed a simple 1-D thermo-mechanical model constrained by radar observations to infer the age in an ice sheet
We identified two areas where the age of basal ice should exceed 1.5 Myr

Summary

Introduction

Since around 800 000 years ago, glacial periods have been dominated by a ∼ 100 000-year cyclicity, as documented in multiple proxies from marine, terrestrial and ice core records (Elderfield et al, 2012; Jouzel et al, 2007; Lisiecki and Raymo, 2005; Loulergue et al, 2008; Lüthi et al, 2008; Wang et al, 2008; Wolff et al, 2006) These data have provided evidence of consistent changes in polar and tropical temperatures, continental aridity, aerosol deposition, atmospheric greenhouse gas concentrations and global mean sea level over numerous glacial cycles. Parrenin et al.: Is there 1.5-million-year-old ice near Dome C, Antarctica?

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Results

Conclusion