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

Rhodes, Rachael H. and Brook, Edward J. and McConnell, Joseph R. and Blunier, Thomas and Sime, Louise C. and Faïn, Xavier and Mulvaney, Robert (2017) Atmospheric methane variability: Centennial-scale signals in the Last Glacial Period. Global Biogeochemical Cycles. ISSN 0886-6236 DOI 10.1002/2016GB005570

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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.

Item Type: Article
Uncontrolled Keywords: NILAREP; IA72,
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
08 - Green Open Access
Journal or Publication Title: Global Biogeochemical Cycles
Identification Number: 10.1002/2016GB005570
Depositing User: Sarah Humbert
Date Deposited: 08 Apr 2017 00:13
Last Modified: 28 Apr 2017 16:38

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