HR: 1340h
AN: PP33C-1604    [Abstracts]
TI: A GCM study of the role of changing emissions and climate on atmospheric methane variations during the Holocene and glacial-interglacial transitions
AU: * Harder, S
EM: harders@vancouver.wsu.edu
AF: Washington State University, Environmental Science Program 14204 NE Salmon Creek Ave., Washougal, WA 98671 United States
AU: Shindell, D
EM: dshindell@giss.nasa.gov
AF: NASA Goddard Institute for Space Studies, 280 Broadway, New York, NY 10025 United States
AU: Schmidt, G
EM: gschmidt@giss.nasa.gov
AF: NASA Goddard Institute for Space Studies, 280 Broadway, New York, NY 10025 United States
AU: Brook, E
EM: brooke@geo.oregonstate.edu
AF: Oregon State University, Dept. of Geosciences 104 Wilkinson Hall, Corvallis, OR 97331 United States
AB: Ice core records of atmospheric methane concentration and its interpolar gradient vary with climate. Efforts have recently been directed at understanding the factors that created this record. We use the Goddard Institute for Space Studies General Circulation Model including tropospheric chemistry to study of the response of methane concentration to source changes during the Holocene and to a changing chemical sink resulting from changes in VOC emissions and SSTs during glacial-interglacial transitions. Results show that changes in the source distribution are not linear within the Holocene. We combine model results with ice core data to provide constraints on changes in northern and tropical sources. Contour plots are constructed for methane concentration and gradient that together allow us to determine the degree of tropical and northern emissions changes for specific Holocene periods. At glacial-interglacial transitions methane concentration is sensitive to changes in both VOC and tropical methane emissions but the sensitivity changes significantly as SST decreases. Our findings suggest that changes in the ice core methane record are likely the result of changes in both the source and the sink. Changes in the sink become especially important when changes in methane concentration and climate are large.
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1616 Climate variability (1635, 3305, 3309, 4215, 4513)
DE: 1622 Earth system modeling (1225)
DE: 1626 Global climate models (3337, 4928)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005