Abstract
Abstract. The area near Dome C, East Antarctica, is thought to be one of the most promising targets for recovering a continuous ice-core record spanning more than a million years. The European Beyond EPICA consortium has selected Little Dome C (LDC), an area ∼ 35 km southeast of Concordia Station, to attempt to recover such a record. Here, we present the results of the final ice-penetrating radar survey used to refine the exact drill site. These data were acquired during the 2019–2020 austral summer using a new, multi-channel high-resolution very high frequency (VHF) radar operating in the frequency range of 170–230 MHz. This new instrument is able to detect reflectors in the near-basal region, where previous surveys were largely unable to detect horizons. The radar stratigraphy is used to transfer the timescale of the EPICA Dome C ice core (EDC) to the area of Little Dome C, using radar isochrones dating back past 600 ka. We use these data to derive the expected depth–age relationship through the ice column at the now-chosen drill site, termed BELDC (Beyond EPICA LDC). These new data indicate that the ice at BELDC is considerably older than that at EDC at the same depth and that there is about 375 m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, ∼ 93 % of the ice thickness, below which there is a basal unit with unknown properties. An ice-flow model tuned to the isochrones suggests ages likely reach 1.5 Myr near 2500 m, ∼ 65 m above the basal unit and ∼ 265 m above the bed, with sufficient resolution (19 ± 2 kyr m−1) to resolve 41 kyr glacial cycles.
Highlights
Ice cores provide one of the best records of paleoclimate on 100 kyr timescales, but to date no continuous ice core has been recovered that spans more than 800 kyr in stratigraphic order
To the east of Little Dome C (LDC) there is some down-warping of englacial horizons, but the ice in that area is thicker than at Beyond EPICA LDC (BELDC) as the bed deepens in subglacial valleys
Near LDC, they indicate a unit of basal ice in which few events are visible; the origin of this basal unit requires further investigations as its flow properties and composition are unknown
Summary
Ice cores provide one of the best records of paleoclimate on 100 kyr timescales, but to date no continuous ice core has been recovered that spans more than 800 kyr in stratigraphic order. There is great interest in extending ice-core records beyond the mid-Pleistocene transition (1.25 to 0.7 Ma), since this may provide unique insight in the mechanism which caused the switch between 41 and 100 kyr ice-age cycles. An ice core spanning the last ∼ 1.5 Myr would extend into the period characterized by regular 41 kyr cycles and would provide a more precise record of greenhouse gases through this transition than is currently available (Fischer et al, 2013).
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