The potential of 14CO in glacial ice as a tracer for past cosmic ray flux and atmospheric hydroxyl radical abundance
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Date
2016-03-07
Journal Title
Journal ISSN
Volume Title
Publisher
Antarctic Climate and Ecosystems Cooperative Research Centre
Abstract
The amount of 14C-containing carbon monoxide (14CO) in glacial ice is determined by
trapping of atmospheric 14CO into air bubbles in the ice and in situ cosmogenic production
of 14CO in relatively shallow ice and firn. Earlier studies of 14CO in ice cores showed large
disagreements with regard to rates of in situ cosmogenic production as well as with regard
to whether 14CO produced in the firn layer is well retained or largely escapes to the
atmosphere via the interconnected pore space. We have reviewed previously published work
that included 14CO measurements in ice or firn air, and compared with our more recent
high-precision measurements on very large ice and firn samples. The available evidence
suggests that very little in situ cosmogenic 14CO is retained in the diffusive part of the firn
(the upper ≈ 40 – 100m). In situ cosmogenic 14CO production rates below the firn diffusive
zone are non-negligible, with production due to deeper-penetrating muons. At sites with low
snow accumulation rates, the in situ cosmogenic 14CO component is expected to be larger
than the trapped atmospheric component. This potentially allows to use ice core 14CO
measurements from such sites to improve our understanding of past cosmic ray flux
variations. In contrast, at sites with very high accumulation rates, trapped atmospheric 14CO
is expected to be dominant over the in situ cosmogenic component. This potentially allows
14CO records from such sites to be used for reconstructions of past atmospheric hydroxyl
radical (OH) variations.
Description
Keywords
Carbon 14, Isotope dating, Ice, Antarctic regions, Glaciers, Cosmic ray flux, Atmospheric chemistry, Carbon monoxide, Drill cores
Citation
Petrenko, V. V., Hmiel, B., Neff, P., Smith, A. M., Buizert, C., Etheridge, D., & Dyonisius, M. (2016). The potential of 14CO in glacial ice as a tracer for past cosmic ray flux and atmospheric hydroxyl radical abundance. Paper presented at the IPICS 2016, International Partnerships in Ice Core Sciences, Second Open Science Conference, 7-11 March 2016, Hobart, Tasmania.