HR: 16:00h
AN: U24C-01    [Abstracts]
TI: Stability of the Stratospheric Ozone Shield During the End-Permian Mass Extinction
AU: * Beerling, D
EM: d.j.beerling@sheffield.ac.uk
AF: University of Sheffield, Department of Animal and Plant Sciences, University of Sheffield, Sheffield, S10 2TN, United Kingdom
AU: Harfoot, M
EM: michael.harfott@aeat.co.uk
AF: University of Cambridge, Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, CB1 1EW, United Kingdom
AU: Pyle, J
EM: john.pyle@atm.ch.cam.ac.uk
AF: University of Cambridge, Centre for Atmospheric Science, Department of Chemistry, University of Cambridge, Cambridge, CB1 1EW, United Kingdom
AB: The end-Permian mass extinction (251 Myr ago) is associated with the eruption of the Siberian Traps, and has also been linked with massive H₂S releases from super-anoxic oceans and CH₄ degassing from sea-floor clathrates. This presentation will present new calculations using the Cambridge two-dimensional atmospheric chemistry-transport model that assess the potential for each of these scenarios to damage Earth's ozone layer which shields the surface biota from harmful ultraviolet-B radiation. Our calculations include representation of the warm end-Permian ‘greenhouse' climate and its modelled low O₂ atmospheric content (15 %). We show that the direct and indirect effects of the Siberian Traps have the greatest potential to exert severe O₃ depletion, to an extent that depends on the duration of the main eruptive phase. However, the O₃ layer is found to be remarkably resilient to massive oceanic H₂S and CH₄ releases, both separately, and in combination. The results will be discussed in the context of chemical and transport mechanisms that lead to these different conclusions.
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 0370 Volcanic effects (8409)
DE: 0404 Anoxic and hypoxic environments (4802, 4834)
DE: 4904 Atmospheric transport and circulation
SC: Union [U]
MN: 2007 Fall Meeting