Radiometric 81Kr dating identifies 120,000 year old ice at Taylor Glacier, Antarctica Christo Buizerta*, Daniel Baggenstosb, Wei Jiangc, Roland Purtschertd, Vasilii V. Petrenkoe, Zheng-Tian Luc,f, Peter Müllerc, Tanner Kuhlg, James Leea, Jeffrey P. Severinghausb and Edward J. Brooka aCollege of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis OR 97331, USA bScripps Institution of Oceanography, University of California, San Diego, CA 92093, USA cPhysics Division, Argonne National Laboratory, Argonne, IL 60439, USA dClimate and Environmental Physics, University of Bern, CH-3012 Bern, Switzerland eDepartment of Earth and Environmental Sciences, University of Rochester, Rochester NY 14627, USA fDepartment of Physics and Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA gIce Drilling Design and Operations, University of Wisconsin, Madison WI 53706, USA *Corresponding author:
[email protected] 104 CEOAS Admin Bldg., Oregon State University, Corvallis OR 97333, USA Abstract We present the first successful 81Kr-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four ~350 kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The 81Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean absolute age offset of 6 ± 2.5 ka. Our experimental methods and sampling strategy are validated by 1) 85Kr and 39Ar analyses that show the samples to be free of modern air contamination, and 2) air content measurements that show the ice did not experience gas loss. We estimate the error in the 81Kr ages due to past geomagnetic variability to be below 3 ka.