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Science 25 August 2006:
Vol. 313. no. 5790, pp. 1109 - 1112
DOI: 10.1126/science.1126562
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Reports

Ice Record of {delta}13C for Atmospheric CH4 Across the Younger Dryas-Preboreal Transition

Hinrich Schaefer,1,2* Michael J. Whiticar,1 Edward J. Brook,2 Vasilii V. Petrenko,3 Dominic F. Ferretti,4,5 Jeffrey P. Severinghaus3

We report atmospheric methane carbon isotope ratios ({delta}13CH4) from the Western Greenland ice margin spanning the Younger Dryas–to–Preboreal (YD-PB) transition. Over the recorded ~800 years, {delta}13CH4 was around –46 per mil ({per thousand}); that is, ~1{per thousand} higher than in the modern atmosphere and ~5.5{per thousand} higher than would be expected from budgets without 13C-rich anthropogenic emissions. This requires higher natural 13C-rich emissions or stronger sink fractionation than conventionally assumed. Constant {delta}13CH4 during the rise in methane concentration at the YD-PB transition is consistent with additional emissions from tropical wetlands, or aerobic plant CH4 production, or with a multisource scenario. A marine clathrate source is unlikely.

1 School of Earth and Ocean Sciences, University of Victoria, Post Office Box 3055, V8W 3P6, Canada.
2 Department of Geosciences, Oregon State University, 104 Wilkinson Hall, Corvallis, OR 97331, USA.
3 Scripps Institution of Oceanography, University of California, San Diego, Mail Code 0244, La Jolla, CA 92093, USA.
4 Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
5 National Institute of Water and Atmospheric Research Limited, Post Office Box 14901, Wellington, New Zealand.

* To whom correspondence should be addressed. E-mail: schaefeh{at}geo.oregonstate.edu

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