HR: 1330h
AN: A52A-0767    [PDF]
TI: An Update of the NOAA-University of Colorado Global Atmospheric Methane Isotope Record
AU: * Miller, J B
EM: john.b.miller@noaa.gov
AF: CIRES, University of Colorado, Campus Box 216, 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: Dreier, M
EM: dreier@spot.colorado.edu
AF: INSTAAR, University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Claymore, V
EM: morrisv@colorado.edu
AF: INSTAAR, University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Fletcher, S M
EM: fletcher@igpp.ucla.edu
AF: Institute for Geophysics and Planetary Physics University of California, Los Angeles, 5438 Slichter Hall, Los Angeles, CA 90025 United States
AU: White, J W
EM: james.white@colorado.edu
AF: INSTAAR, University of Colorado, Campus Box 450, Boulder, CO 80309 United States
AU: Dlugokencky, E J
EM: ed.dlugokencky@noaa.gov
AF: NOAA/CMDL, R/CMDL1 325 Broadway, Boulder, CO 80305 United States
AU: Tans, P P
EM: pieter.tans@noaa.gov
AF: NOAA/CMDL, R/CMDL1 325 Broadway, Boulder, CO 80305 United States
AB: Starting in 1998, measurements of $\delta^{13}$C of CH$_{4}$ began on samples collected weekly at six sites of the NOAA/CMDL Cooperative Air Sampling Network. Since then, six other sites have been added, expanding the global coverage of our measurements. Our measurements reveal no significant inter-annual trend since 1999, similar to the methane growth rate over the same time frame. However, annual mean $\delta^{13}$C values in 1998 are more negative than the rest of the record, consistent with the hypothesis that the 1998 methane growth rate anomaly was caused, at least in part, by increased emissions from wetlands. The atmospheric inter-hemispheric gradient has also remained relatively constant through our record, which may be an indication of a steady distribution of sources. At higher time frequencies, seasonal cycle amplitudes of at least 0.5 per mil are observed at our high northern sites (Barrow and Alert), while we see small or no amplitude at our southern sites. The strong seasonal cycles in $\delta^{13}$C observed at Barrow and Alert are out of phase with the seasonal cycle of methane, indicating a complex mixture of source and sink processes responsible for the observed variations in methane concentration at these sites. Finally, we will use our CH$_{4}$ and $\delta^{13}$C measurements to derive multi-year average estimates (and uncertainty) for different methane sources using both a simple two-box model and a three-dimensional transport model.
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