HR: 0800h
AN: B41D-0227 [Abstracts]
TI: Atmospheric Chemistry Response to Changes in Tropospheric Methane Concentration: Application to the
Permian-Triassic Boundary.
AU: * Lamarque, J
EM: lamar@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305
United States
AU: Kiehl, J T
EM: jtkon@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305
United States
AU: Shields, C
EM: shields@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305
United States
AU: Boville, B A
EM: boville@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305
United States
AB:
A large methane release from clathrates at the end of the Permian (250 million years ago) has been hypothesized as a possible
explanation for the observed large light isotopic carbon deviation. Estimates of the release provide a range of equivalent
tropospheric methane concentrations; this range indicates that concentrations up to 1000x present-day conditions were
possible. We evaluate the atmospheric chemical impact of such methane concentrations using a three-dimensional climate model
(extending from the surface to approximately 85 km) with interactive chemistry. The model uses the land/ocean distribution
(including sea-surface temperature) from Kiehl and Shields (Geology, 2005), representative of the simulated time period.
Our results indicate that stratospheric ozone shows limited sensitivity to the methane loading until tropospheric methane
reaches 750x present-day concentrations. The response for larger concentrations indicates a very rapid collapse of the
atmospheric ozone. Very nonlinear behaviors are also observed in other chemically-important species such as OH and CO.
Implications for the sustainability of life are discussed.
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 0365 Troposphere: composition and chemistry
DE: 0473 Paleoclimatology and paleoceanography (3344, 4900)
DE: 0714 Clathrate
SC: Biogeosciences [B]
MN: Fall Meeting 2005