Toward a radiometric ice clock: uranium ages of the Dome C ice core

• Published in: Quaternary Science Reviews
• Main Authors: Aciego, S., Bourdon, B., Schwander, J., Baur, H., Forieri, A.
• Other Authors: Aciego, S.; Institute of Geochemistry and Petrology, ETH Zurich, Switzerland, Bourdon, B.; Department of Geological Sciences, University of Michigan, Ann Arbor, MI, USA, Schwander, J.; Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland, Baur, H.; Institute of Geochemistry and Petrology, ETH Zurich, Switzerland, Forieri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia, Institute of Geochemistry and Petrology, ETH Zurich, Switzerland, Department of Geological Sciences, University of Michigan, Ann Arbor, MI, USA, Climate and Environmental Physics, Physics Institute, University of Bern, Switzerland, Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier Science Limited 2011
• Subjects: Radiometric ice clock; 02. Cryosphere::02.03. Ice cores::02.03.99. General or miscellaneous; EPICA; ice core
• Online Access: http://hdl.handle.net/2122/7786; https://doi.org/10.1016/j.quascirev.2011.06.008

Ice sheets and deep ice cores have yielded a wealth of paleoclimate information based on continuous dating methods while independent radiometric ages of ice have remained elusive. Here we demonstrate the application of (234U/238U) measurements to dating the EPICA Dome C ice core based on the accumulation of 234U in the ice matrix from recoil during 238U decay out of dust bound within the ice. Measured (234U/238U) activity ratios within the ice generally increase with depth while the surface areas of the dust grains are relatively constant. Using a newly designed device for measuring surface area for small samples, we were able to estimate reliably the recoil efficiency of nuclides from dust to ice. The resulting calculated radiometric ages range between 80 ka and 870 ka. Measured samples in the upper 3100 m fall on the previously published age-depth profile. Samples in the 3200–3255 m section show a marked change from 723–870 ka to 85 ka indicating homogenization of the deep ice prior to resetting of the (234U/238U) age in the basal layers. The mechanism for homogenization is likely enhanced lateral ice flow due to high basal melting and geothermal heat flux. Published 2389-2397 JCR Journal open