Document Type
Article
Publication Date
2010
Abstract
In this study, we report measurements of CFC-12 (CCl2F2) in firn air and in air extracted from shallow ice cores from three Antarctic sites. The firn air data are consistent with the known atmospheric history of CFC-12. In contrast, some of the ice core samples collected near the firn-ice transition exhibit anomalously high CFC-12 levels. Together, the ice core and firn air data provide evidence for the presence of modern air entrapped in the shallow ice core samples that likely contained open pores at the time of collection. We propose that this is due to closure of the open pores after drilling, entrapping modern air and resulting in elevated CFC-12 mixing ratios. Our results reveal that open porosity can exist below the maximum depth at which firn air samples can be collected, particularly at sites with lower accumulation rates. CFC-12 measurements demonstrate that post-drilling closure of open pores can lead to a change in the composition of bubble air in shallow ice cores through purely physical processes. The results have implications for investigations involving trace gas composition of bubbles in shallow ice cores collected near the firn-ice transition.
Recommended Citation
Aydin, M., et al. "Post-coring entrapment of modern air in some shallow ice cores collected near the firn-ice transition: evidence from CFC-12 measurements in Antarctic firn air and ice cores." Atmospheric Chemistry and Physics 10.11 (2010): 5135-5144. doi: 10.5194/acp-10-5135-2010
Copyright
The authors
Creative Commons License
This work is licensed under a Creative Commons Attribution 3.0 License.
Comments
This article was originally published in Atmospheric Chemistry and Physics, volume 10, issue 11, in 2010. DOI: 10.5194/acp-10-5135-2010