In search of in-situ radiocarbon in Law Dome ice and firn

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 2000-10, Vol.172 (1), p.610-622
• Main Authors: Smith, A.M., Levchenko, V.A., Etheridge, D.M., Lowe, D.C., Hua, Q., Trudinger, C.M., Zoppi, U., Elcheikh, A.
• Format: Article
• Language: English
• Subjects: 14CO; 14CO 2; Antarctica; Bomb pulse; Firn; In-situ; Radiocarbon
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/S0168-583X(00)00280-9

Results of AMS radiocarbon measurements on CO and CO 2 separated from firn air directly pumped from the ice sheet, and on CO 2 separated from air extracted from ice cores by a dry grating technique, are presented. The firn air samples and ice cores used in this study were collected from the region of Law Dome, Antarctica. No evidence of in-situ 14CO 2 was found in the firn air samples or the ice core air samples from one site although a slight enhancement of 14CO above expected polar atmospheric concentrations was observed for some firn air samples. A clear in-situ 14CO 2 signal for ice pre-dating the radiocarbon bomb pulse was found, however, in air samples extracted from an ice core from a second site. We compare these results and propose an hypothesis to explain this apparent contradiction. The degree to which in-situ 14C is released from the ice crystals during trapping and bubble formation is considered and discussed. The selectivity of the dry grating technique for the extraction of trapped atmospheric gases from ice cores is also discussed and compared with other methods.