Revealing Old Ice with Krypton-81 (81Kr)
Abstract
The noble gas radioisotope 81Kr (half-life 229 ka) has long been identified as an ideal tracer for dating water and ice in the range of 50-1300 ka, particularly because it is inert, gaseous and of cosmogenic origin [1]. However, for a long time 81Kr dating was hampered by the lack of a detection technique that can meet the requirements of analyzing its extremely low abundance at a reasonable sample size. A few years ago, 81Kr-dating was demonstrated on large (100-200 kg) ice samples from Taylor-Glacier (Antarctica) with the laser-based detection method Atom Trap Trace Analysis (ATTA) [2].
Here, we report on 81Kr dating of ice samples as small as 6 kg with the latest ATTA instrument at USTC (http://atta.ustc.edu.cn). We applied the method to samples from the Guliya ice cap of Tibetan Plateau, and from blue ice areas as well as deep ice cores of Antarctica. The resulting 81Kr ages, ranging from <50 ka to >1200 ka, provide unambiguous constraints on the timescale of these ice samples. These recent advances underline the usefulness of 81Kr for dating existing ice cores as well as searching for old ice beyond 1 Ma. [1] Z.-T. Lu, Tracer applications of noble gas radionuclides in the geosciences, Ear. Sci. Rev. 138, 196-214, (2014) [2] C. Buizert, Radiometric 81Kr dating identifies 120,000-year-old ice at Taylor Glacier, Antarctica, PNAS 111, 6876, (2014)- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.C41C1744L
- Keywords:
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- 3337 Global climate models;
- ATMOSPHERIC PROCESSESDE: 0724 Ice cores;
- CRYOSPHEREDE: 1621 Cryospheric change;
- GLOBAL CHANGEDE: 4901 Abrupt/rapid climate change;
- PALEOCEANOGRAPHY