TY - JOUR

T1 - Brief communication

T2 - New radar constraints support presence of ice older than 1.5 Myr at Little Dome C

AU - Lilien, David A.

AU - Steinhage, Daniel

AU - Taylor, Drew

AU - Parrenin, Frederic

AU - Ritz, Catherine

AU - Mulvaney, Robert

AU - Martin, Carlos

AU - Yan, Jie-Bang

AU - O'Neill, Charles

AU - Frezzotti, Massimo

AU - Miller, Heinrich

AU - Gogineni, Prasad

AU - Dahl-Jensen, Dorthe

AU - Eisen, Olaf

PY - 2021/4/19

Y1 - 2021/4/19

N2 - 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 similar to 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 375m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, similar to 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, similar to 65m above the basal unit and similar to 265m above the bed, with sufficient resolution (19 +/- 2 kyrm(-1)) to resolve 41 kyr glacial cycles.

AB - 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 similar to 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 375m of ice older than 600 kyr at BELDC. Stratigraphy is well preserved to 2565 m, similar to 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, similar to 65m above the basal unit and similar to 265m above the bed, with sufficient resolution (19 +/- 2 kyrm(-1)) to resolve 41 kyr glacial cycles.

KW - CHRONOLOGY

U2 - 10.5194/tc-15-1881-2021

DO - 10.5194/tc-15-1881-2021

M3 - Journal article

VL - 15

SP - 1881

EP - 1888

JO - The Cryosphere

JF - The Cryosphere

SN - 1994-0416

IS - 4

ER -