Hypothetical methane pulse from clathrates: simulation of atmospheric implications and preservation in ice cores

• Published in: Quaternary International
• Main Author: Bock, Josué
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2012
• Subjects: ice core
• Online Access: https://ueaeprints.uea.ac.uk/id/eprint/53125/; https://doi.org/10.1016/j.quaint.2012.07.254

It remains an open question if methane clathrate degassing events could be fully recorded by the ice core records, depending on their strength and duration. Due to the relatively short residence time of methane in the atmosphere, return to background atmospheric values after an initial burst of clathrates could happen within a few decades and be nearly absent from the ice core archive. In this study, sudden methane emissions of variable amplitude, duration and location are simulated with a 2 dimensional atmospheric chemistry model. The signatures of the two stable isotopes of methane (DCH3 and 13CH4), which reflect additional aspects of the methane budget, are also simulated. Different environmental conditions are considered (present, pre-industrial, glacial). The resulting time trends in methane and its stable isotopes are investigated, as well as their consequences in terms of atmospheric oxidation capacity and radiative forcing. A model of trace gas transport in firn is then used to investigate the preservation of the atmospheric signals in ice cores at sites undergoing different glaciological conditions (e.g. temperature, snow accumulation rate). The stable isotope signals in ice allow to identify characteristic signatures of a massive methane release from hydrates. High time-resolution analysis of these stable isotopes in ice would, however, be necessary for such an identification.