ice
; krypton
; krypton 81
; unclassified drug
; ice
; air pollution
; analytic method
; Antarctica
; article
; astronomy
; atom trap trace analysis
; glacier
; interglacial
; priority journal
; radiometric dating
; chemistry
; climate change
; gas
; Geochronology
; glaciology
; ice cover
; methodology
; paleoclimatology
; reproducibility
; standard
; geochronology
; glaciology
; paleoclimatology
; Antarctic Regions
; Climate Change
; Gases
; Ice
; Ice Cover
; Krypton Radioisotopes
; Radiometric Dating
; Reproducibility of Results
英文摘要:
We present 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 (i) 85Kr and 39Ar 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 81Kr 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 large samples are available, greatly enhancing their scientific value as archives of old ice and meteorites. At present, ATTA 81Kr analysis requires a 40-80-kg ice sample; as sample requirements continue to decrease, 81Kr dating of ice cores is a future possibility.
Buizert, C., College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States; Baggenstos, D., Scripps Institution of Oceanography, University of California, San Diego, CA 92093, United States; Jiang, W., Physics Division, Argonne National Laboratory, Argonne, IL 60439, United States; Purtschert, R., Climate and Environmental Physics, University of Bern, CH-3012 Bern, Switzerland; Petrenko, V.V., Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, United States; Lu, Z.-T., Physics Division, Argonne National Laboratory, Argonne, IL 60439, United States, Department of Physics, Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, United States; Müller, P., Physics Division, Argonne National Laboratory, Argonne, IL 60439, United States; Kuhl, T., Ice Drilling Design and Operations, University of Wisconsin, Madison, WI 53706, United States; Lee, J., College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States; Severinghaus, J.P., Scripps Institution of Oceanography, University of California, San Diego, CA 92093, United States; Brook, E.J., College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States
Recommended Citation:
Buizert C.,Baggenstos D.,Jiang W.,et al. Radiometric 81Kr dating identifies 120;000-year-old ice at Taylor Glacier; Antarctica[J]. Proceedings of the National Academy of Sciences of the United States of America,2014-01-01,111(19)