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AGU: Geophysical Research Letters

 

Index Terms

  • Atmospheric Composition and Structure: Biosphere/atmosphere interactions
  • Biogeosciences: Carbon cycling
  • Biogeosciences: Isotopic composition and chemistry
  • Global Change: Biogeochemical cycles, processes, and modeling
  • Atmospheric Processes: Stratosphere/troposphere interactions

Abstract

GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L02802, 5 PP., 2005
doi:10.1029/2004GL021011

Triple oxygen isotope composition of tropospheric carbon dioxide as a tracer of terrestrial gross carbon fluxes

K. J. Hoag

Department of Earth and Planetary Science and Department of Chemistry, University of California, Berkeley, California, USA

C. J. Still

Department of Geography, University of California, Santa Barbara, California, USA

I. Y. Fung

Department of Earth and Planetary Science and Department of Chemistry, University of California, Berkeley, California, USA

K. A. Boering

Department of Earth and Planetary Science and Department of Chemistry, University of California, Berkeley, California, USA

Stratospheric photochemistry leads to anomalous oxygen isotope enrichments in CO2 (for which Δ17O = δ17O − 0.516 × δ18O ≠ 0). This isotope anomaly is not lost until air returns to the troposphere and CO2 undergoes isotope exchange with water primarily in the terrestrial biosphere and oceans. A two-box model is used to investigate the contribution of stratospheric production and contemporary surface carbon fluxes to tropospheric Δ17OCO2. The predicted magnitude of ∼0.15‰ is large enough that measurement of a globally averaged tropospheric Δ17OCO2 should provide a new constraint for gross carbon exchanges between the biosphere and atmosphere in terrestrial carbon cycle models. Importantly, Δ17OCO2 should be complementary to the primary isotopic tracer of gross carbon exchanges, δ18OCO2, but is not dependent on numerous hydrologic variables. Furthermore, with improved measurement precision, Δ17OCO2 could serve as a direct tracer of gross carbon exchanges and their variations.

Received 14 July 2004; accepted 9 December 2004; published 19 January 2005.

Citation: Hoag, K. J., C. J. Still, I. Y. Fung, and K. A. Boering (2005), Triple oxygen isotope composition of tropospheric carbon dioxide as a tracer of terrestrial gross carbon fluxes, Geophys. Res. Lett., 32, L02802, doi:10.1029/2004GL021011.

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