Ice core records from Antarctica and Greenland show greenhouse gas signatures consistent with climate inferences assumed from records of oxygen isotope fractions through time.
Noting that atmospheric methane decays quickly, O'Hara seeks to understand what kind of methane source is capable of sustaining the levels and concentrations of methane seen in the ice core record.
Through a kinematic model, the author finds that the methane source reservoir that created the ice core signals must have had high initial methane concentrations and long residence times. Because the glacial climate was dryer compared with today's climate, the author then assumes that the amount of methane currently escaping from wetlands is presently at a maximum.
He finds, however, that the current storage capacity of the methane source for global wetlands is much too small to account for the signatures seen in the ice cores. Instead, the author proposes that gas hydrates in shallow marine sediments are the likely dominant source of the methane found in ice cores and thus the dominant source of methane in past environments.
Journal reference: A model for late Quaternary methane ice core signals: Wetlands versus a shallow marine source. Geophysical Research Letters (GRL) paper 10.1029/2007GL032317, 2008; http://dx.doi.org/10.1029/2007GL032317
Authors: Kieran D. O'Hara: Department of Earth and Environmental Sciences, University of Kentucky, Lexington, Kentucky, U.S.A.
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