Atmospheric methane variability: Centennial-scale signals in the Last Glacial Period

Rachael H. Rhodes, Edward J. Brook, Joseph R. McConnell, Thomas Blunier, Louise C. Sime, Xavier Fain, Robert Mulvaney

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)
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Abstract

In order to understand atmospheric methane (CH4) biogeochemistry now and in the future, we must apprehend its natural variability, without anthropogenic influence. Samples of ancient air trapped within ice cores provide the means to do this. Here we analyze the ultrahigh‐resolution CH4 record of the West Antarctic Ice Sheet Divide ice core 67.2–9.8 ka and find novel, atmospheric CH4 variability at centennial time scales throughout the record. This signal is characterized by recurrence intervals within a broad 80–500 year range, but we find that age‐scale uncertainties complicate the possible isolation of any periodic frequency. Lower signal amplitudes in the Last Glacial relative to the Holocene may be related to incongruent effects of firn‐based signal smoothing processes. Within interstadial and stadial periods, the peak‐to‐peak signal amplitudes vary in proportion to the underlying millennial‐scale oscillations in CH4 concentration—the relative amplitude change is constant. We propose that the centennial CH4 signal is related to tropical climate variability that influences predominantly low‐latitude wetland CH4 emissions.
Original languageEnglish
Pages (from-to)575-590
Number of pages16
JournalGlobal Biogeochemical Cycles
Volume31
Issue number3
Early online date22 Mar 2017
DOIs
Publication statusPublished - Mar 2017
Externally publishedYes

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