HR: 15:10h
AN: A42D-07    [PDF]
TI: Carbon-13 Evidence of the Causes of the Atmospheric Methane Concentration Increase Since 1700AD and of a Varying Methane Budget Beforehand
AU: * Etheridge, D
EM: david.etheridge@csiro.au
AF: CSIRO Atmospheric Research, PMB No. 1, Aspendale, Vic 3195 Australia
AU: Ferretti, D
EM: d.ferretti@niwa.co.nz
AF: National Institute of Water and Atmospheric Research Ltd, PO Box 14901, Kilbirnie, Wel 1 New Zealand
AU: Ferretti, D
EM: d.ferretti@niwa.co.nz
AF: University of Colorado, Box 450, Boulder, CO 80309 United States
AU: Miller, J B
EM: john.b.miller@noaa.gov
AF: University of Colorado, Box 450, Boulder, CO 80309 United States
AU: Miller, J B
EM: john.b.miller@noaa.gov
AF: NOAA/CMDL, R/CMDL1 325 Broadway, Boulder, CO 80305 United States
AU: White, J W
EM: james.white@colorado.edu
AF: University of Colorado, Box 450, Boulder, CO 80309 United States
AU: Lowe, D
EM: d.lowe@niwa.co.nz
AF: National Institute of Water and Atmospheric Research Ltd, PO Box 14901, Kilbirnie, Wel 1 New Zealand
AU: MacFarling, C
EM: Cecelia.Macfarling@csiro.au
AF: CSIRO Atmospheric Research, PMB No. 1, Aspendale, Vic 3195 Australia
AU: Dreier, M
EM: Mark.Dreier@colorado.edu
AF: University of Colorado, Box 450, Boulder, CO 80309 United States
AU: Trudinger, C
EM: cathy.trudinger@csiro.au
AF: CSIRO Atmospheric Research, PMB No. 1, Aspendale, Vic 3195 Australia
AU: van Ommen, T
EM: tas.van.ommen@utas.edu.au
AF: Antarctic CRC & Australian Antarctic Division, GPO Box 252-80, Hobart, Tas 7001 Australia
AU: Lassey, K
EM: k.lassey@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research Ltd, PO Box 14901, Kilbirnie, Wel 1 New Zealand
AU: Allan, W
EM: w.allan@niwa.cri.nz
AF: National Institute of Water and Atmospheric Research Ltd, PO Box 14901, Kilbirnie, Wel 1 New Zealand
AU: Allison, C
EM: collin.allison@csiro.au
AF: CSIRO Atmospheric Research, PMB No. 1, Aspendale, Vic 3195 Australia
AU: Francey, R
EM: roger.francey@csiro.au
AF: CSIRO Atmospheric Research, PMB No. 1, Aspendale, Vic 3195 Australia
AB: The causes of the major increase in the concentration of atmospheric methane since 1700 AD are investigated. We measured d13CH4 in air extracted from Antarctic ice cores and firn and in air archived from Cape Grim, Tasmania. This was done using a newly developed GC-IRMS technique that analyses very small air samples with high precision. The results show that d13CH4 increased over the past century, consistent with the addition of isotopically enriched sources from anthropogenic activity. However a large increase (about 1.5 per mil) in d13CH4 from 1700AD back to about 1500AD was also observed. This was quite unexpected as it was previously assumed, based on the small observed changes in methane concentration, that the pre-anthropogenic methane budget was approximately in balance. Explanations for the cause of this d13CH4 increase invoke changes in enriched sources such as biomass burning with compensating changes in biogenic (mainly wetland) sources, or changes in a strongly fractionating sink.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 0322 Constituent sources and sinks
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting