Independent variations of CH 4 emissions and isotopic composition over the past 160,000 years

Lars Möller, Todd Sowers, Michael Bock, Renato Spahni, Melanie Behrens, Jochen Schmitt, Heinrich Miller, Hubertus Fischer

Research output: Contribution to journalArticlepeer-review

36 Scopus citations

Abstract

During the last glacial cycle, greenhouse gas concentrations fluctuated on decadal and longer timescales. Concentrations of methane, as measured in polar ice cores, show a close connection with Northern Hemisphere temperature variability, but the contribution of the various methane sources and sinks to changes in concentration is still a matter of debate. Here we assess changes in methane cycling over the past 160,000 years by measurements of the carbon isotopic composition δ 13 C of methane in Antarctic ice cores from Dronning Maud Land and Vostok. We find that variations in the δ 13 C of methane are not generally correlated with changes in atmospheric methane concentration, but instead more closely correlated to atmospheric CO 2 concentrations. We interpret this to reflect a climatic and CO 2 -related control on the isotopic signature of methane source material, such as ecosystem shifts in the seasonally inundated tropical wetlands that produce methane. In contrast, relatively stable δ 13 C values occurred during intervals of large changes in the atmospheric loading of methane. We suggest that most methane sources - most notably tropical wetlands - must have responded simultaneously to climate changes across these periods.

Original languageEnglish (US)
Pages (from-to)885-890
Number of pages6
JournalNature Geoscience
Volume6
Issue number10
DOIs
StatePublished - Oct 2013

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

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