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CH 4 sources estimated from atmospheric observations of CH 4 and its 13 C/ 12 C isotopic ratios: 2. Inverse modeling of CH 4 fluxes from geographical regions
Author(s) -
Mikaloff Fletcher Sara E.,
Tans Pieter P.,
Bruhwiler Lori M.,
Miller John B.,
Heimann Martin
Publication year - 2004
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2004gb002224
Subject(s) - isotope , southern hemisphere , atmospheric sciences , stable isotope ratio , isotopic signature , isotopes of carbon , environmental science , geology , climatology , physics , quantum mechanics
We present a time‐dependent inverse modeling approach to estimate the magnitude of CH 4 emissions and the average isotopic signature of the combined source processes from geographical regions based on the observed spatiotemporal distribution of CH 4 and 13 C/ 12 C isotopic ratios in CH 4 . The inverse estimates of the isotopic signature of the sources are used to partition the regional source estimates into three groups of source processes based on their isotopic signatures. Compared with bottom‐up estimates, the inverse estimates call for larger CH 4 fluxes in the tropics (266 ± 25 Tg CH 4 /yr) and southern extratropics (98 ± 15 Tg CH 4 /yr) and reduced fluxes in the northern extratropics (252 ± 18 Tg CH 4 /yr). The observations of 13 C/ 12 C isotopic ratios in CH 4 indicate that the large a posteriori CH 4 source in the tropics and Southern Hemisphere is attributable to a combination both bacterial sources and biomass burning and support relatively low estimates of fossil CH 4 emissions.