V. V. Petrenko et al., Science (2009) 324(5926): 14CH4 measurements in Greenland ice: Investigating last glacial termination CH4 sources

Science (24 April 2009), Vol. 324, No. 5926, pp. 506–508; DOI: 10.1126/science.1168909

Reports

¹⁴CH₄ measurements in Greenland ice: Investigating last glacial termination CH₄ sources

Vasilii V. Petrenko,^1,*,** Andrew M. Smith,² Edward J. Brook,³ Dave Lowe,⁴ Katja Riedel,⁴ Gordon Brailsford,⁴ Quan Hua,² Hinrich Schaefer,⁴ Niels Reeh,⁵ Ray F. Weiss,¹ David Etheridge,⁶ Jeffrey P. Severinghaus¹

Abstract

The cause of a large increase of atmospheric methane concentration during the Younger Dryas–Preboreal abrupt climatic transition (~11,600 years ago) has been the subject of much debate. The carbon-14 (¹⁴C) content of methane (¹⁴CH₄) should distinguish between wetland and clathrate contributions to this increase. We present measurements of ¹⁴CH₄ in glacial ice, targeting this transition, performed by using ice samples obtained from an ablation site in west Greenland. Measured ¹⁴CH₄ values were higher than predicted under any scenario. Sample ¹⁴CH₄ appears to be elevated by direct cosmogenic ¹⁴C production in ice. ¹⁴C of CO was measured to better understand this process and correct the sample ¹⁴CH₄. Corrected results suggest that wetland sources were likely responsible for the majority of the Younger Dryas–Preboreal CH₄ rise.

¹ Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
² Australian Nuclear Science and Technology Organisation (ANSTO), Private Mail Box 1, Menai, NSW 2234, Australia.
³ Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
⁴ National Institute of Water and Atmospheric Research Ltd., Post Office Box 14901, Kilbirnie, 301 Evans Bay Parade, Wellington, New Zealand.
⁵ DTU Space, National Space Institute, Technical University of Denmark, Ørsteds Plads, Building 348, DK-2800 Kongens Lyngby, Denmark.
⁶ Commonwealth Scientific and Industrial Research Organisation, Marine and Atmospheric Research, Private Mail Box 1, Aspendale, VIC 3195, Australia.

^* Present address: Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.

**Correspondence e-mail: vasilii.petrenko@colorado.edu

Link to abstract:  http://www.sciencemag.org/cgi/content/abstract/324/5926/506