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

TitleRadiometric Kr-81 dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica
Publication TypeJournal Article
Year of Publication2014
AuthorsBuizert C, Baggenstos D, Jiang W., Purtschert R., Petrenko VV, Lu Z.T, Muller P., Kuhl T., Lee J., Severinghaus JP, Brook E.J
JournalProceedings of the National Academy of Sciences of the United States of America
Volume111
Pagination6876-6881
Date Published2014/05
Type of ArticleArticle
ISBN Number0027-8424
Accession NumberWOS:000335798000041
Keywordsatmospheric ch4; climate-change; core; Geochronology; geomagnetic-field; glaciology; greenland; magnetooptical trap; paleoclimatology; past 800,000 years; polar ice; record; termination
Abstract

We present successful Kr-81-Kr radiometric dating of ancient polar ice. Krypton was extracted from the air bubbles in four similar to 350-kg polar ice samples from Taylor Glacier in the McMurdo Dry Valleys, Antarctica, and dated using Atom Trap Trace Analysis (ATTA). The Kr-81 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) Kr-85 and Ar-39 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 Kr-81 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 Kr-81 analysis requires a 40-80-kg ice sample; as sample requirements continue to decrease, Kr-81 dating of ice cores is a future possibility.

DOI10.1073/pnas.1320329111
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