Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica ...

• Main Authors: Severinghaus, J. P., Muller, P., Petrenko, V. V., Lee, J., Baggenstos, D., Purtschert, R., Buizert, C., Lu, Z.-T., Jiang, W., Kuhl, T., Brook, E. J.
• Format: Text
• Language: English
• Published: National Academy of Sciences NAS 2014
• Subjects: 530 Physics; McMurdo Dry Valleys; Taylor Glacier; Atta; Antarc*; Antarctica
• Online Access: https://dx.doi.org/10.7892/boris.74092; http://boris.unibe.ch/74092/

We present successful 81 Kr-Kr radiometric dating of ancient polarice. 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 81 Kr radiometric ages agree with independent age estimates obtained from stratigraphic dating techniques with a mean abso-lute age offset of 6±2.5 ka. Our experimental methods and sampling strategy are validated by (i) 85 Kr and 39 Ar analyses that show the samples to be free of modern air contamination and (ii)air content measurements that show the ice did not experience gas loss. We estimate the error in the 81 Kr ages due to past geomagnetic variability to be below 3 ka. We show that ice from the previous interglacial period (Marine Isotope Stage 5e, 130–115 ka before present) can be found in abundance near the surface of Taylor Glacier. Our study paves the way for reliable radiometric dating of ancient ice in blue ice areas and margin sites where ...