HR: 08:15h
AN: B41G-02    [Abstracts]
TI: Constraining the N2O budget using isotopologues and isotopomers
AU: * Yung, Y L
EM: yly@gps.caltech.edu
AF: Caltech, 2100 E California Blvd, Pasadena, CA 91125, United States
AU: Kim, P
EM: spk@gps.caltech.edu
AF: Caltech, 2100 E California Blvd, Pasadena, CA 91125, United States
AU: Liang, M
EM: mcl@gps.caltech.eu
AF: Caltech, 2100 E California Blvd, Pasadena, CA 91125, United States
AU: Liang, M
EM: mcl@gps.caltech.eu
AF: RCEC Academia Sinica, P.O. Box 1-48 Nankang, Taipei, 00000, Taiwan
AU: Shia, R
EM: rls@gps.caltech.edu
AF: Caltech, 2100 E California Blvd, Pasadena, CA 91125, United States
AB: The continued increase of N2O in the atmosphere is a serious environmental concern. As a consequence, N2O is one of the gases targeted for regulation by the Kyoto Protocol. Therefore, to stabilize concentrations at the present level, an immediate reduction of the additional flux of N2O that has occurred since the Industrial Revolution would be necessary. However, the N2O budget is at present not well quantified, making it difficult to determine the sources and the cause of its increase precisely (IPCC 2007). In order to find the best constraints to the N2O budget, we carried out a time dependent box model study similar to that of Rahn and Wahlen (2000) for N2O and its isotopologues and isotopomers from 1700 A.D. to the present. An adjoint code was constructed from the box model via the Tangent linear and Adjoint Model Compiler (TAMC) to calculate the gradient of a cost function, in this case the least squared sum of residuals, with respect to the initial conditions. These gradient calculations were then fed to optimization algorithms to minimize the value of the cost function, thereby acquiring the optimal parameters and the best fit to the observed data. Preliminary results are as follows: (1) The IPCC 2007 N2O budget appears to be consistent with the isotopic data, which help to refine some of the fluxes; (2) The mean nitrification/denitrification ratio for N2O sources is obtained from this analysis in order to explain the time evolution of both 15-N and 18-O data; (3) Our model confirms and extends the "depleted ocean" model of Rahn and Wahlen (2000) for the N2O oceanic source; and (4) Site preference data for 15-N provides the most sensitive discrimination between natural and anthropogenic sources of N2O.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting