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

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. © 2009, American Association for the Advancement of Science (AAAS)

Keywords

Greenland, Ice, Methane, Carbon 14, Climatic change, Air pollution

Citation

Petrenko, V. V., Smith, A. M., Brook, E. J., Lowe, D., Riedel, K., Brailsford, G., Huh, Q., Schaefer, H., Reeh, N., Weiss, R. F., Etheridge, D. M. & Severinghaus, J. P. (2009). 14CH4 measurements in Greenland ice: investigating last glacial termination CH4 sources. Science, 324(5926), 506-508. doi:10.1126/science.1168909