Deep radiostratigraphy of the East Antarctic plateau: connecting the Dome C and Vostok ice core sites

MARIE G. P. CAVITTE,DONALD D. BLANKENSHIP,EMMANUEL LEMEUR,MARTIN J. SIEGERT,FRÉDÉRIC PARRENIN,JOSEPH A. MACGREGOR,DUSTIN M. SCHROEDER,DUNCAN A. YOUNG

doi:10.1017/jog.2016.11

Abstract

ABSTRACTSeveral airborne radar-sounding surveys are used to trace internal reflections around the European Project for Ice Coring in Antarctica Dome C and Vostok ice core sites. Thirteen reflections, spanning the last two glacial cycles, are traced within 200 km of Dome C, a promising region for million-year-old ice, using the University of Texas Institute for Geophysics High-Capacity Radar Sounder. This provides a dated stratigraphy to 2318 m depth at Dome C. Reflection age uncertainties are calculated from the radar range precision and signal-to-noise ratio of the internal reflections. The radar stratigraphy matches well with the Multichannel Coherent Radar Depth Sounder (MCoRDS) radar stratigraphy obtained independently. We show that radar sounding enables the extension of ice core ages through the ice sheet with an additional radar-related age uncertainty of ~1/3–1/2 that of the ice cores. Reflections are extended along the Byrd-Totten Glacier divide, using University of Texas/Technical University of Denmark and MCoRDS surveys. However, core-to-core connection is impeded by pervasive aeolian terranes, and Lake Vostok's influence on reflection geometry. Poor radar connection of the two ice cores is attributed to these effects and suboptimal survey design in affected areas. We demonstrate that, while ice sheet internal radar reflections are generally isochronal and can be mapped over large distances, careful survey planning is necessary to extend ice core chronologies to distant regions of the East Antarctic ice sheet.

Highlights

Ice cores retrieved from East Antarctica provide the longest record of direct greenhouse gas concentrations and are key to understanding late Quaternary climate forcings
(3) Bridge to Vostok – In the third and final phase, we extended the HiCARS radar reflections described in the first phase, but this time we extended them in the direction of the Vostok ice core site along the UT/TUD survey (Fig. 1), to connect the Dome C and the Vostok ice cores
A distinction must be made between the internal stratigraphy within a ∼200 km radius of the Dome C ice core site, which shows relatively uniform, sub-parallel and continuous reflections, with that of areas further upflow towards Lake Vostok, characterized by more complex or truncated reflections due to the presence of the tectonically-controlled deep subglacial Lake Vostok basin (Studinger and others, 2003), and aeolian reworking of the ice surface

Summary

Introduction

Ice cores retrieved from East Antarctica provide the longest record of direct greenhouse gas concentrations and are key to understanding late Quaternary climate forcings. Age uncertainties at such depths become significant using traditional ice core dating methods: single core chronologies vary between confidence intervals of 2 ka at Vostok (O2/N2 dating method; Suwa and Bender, 2008) and 6 ka at Dome C (EDC3 chronology; Parrenin and others, 2007) for ice older than 100 ka. Efforts have been focussed on developing multi-core statistical approaches such as the Antarctic Ice Core Chronology 2012 (AICC2012) timescale (Lemieux-Dudon and others, 2010; Bazin and others, 2013; Veres and others, 2013), which synchronizes five deep polar ice cores. Both cores lack a well established absolute depth certainty (Parrenin and others, 2012). We adopt the AICC2012 chronology to date the radar reflections in this study as that chronology should provide the best comparison of ages between the EDC and Vostok ice core

Results

Discussion

Conclusion