The Stable Isotopic Composition of Atmospheric CO2

H. P. Affek*, D. Yakir

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingChapterpeer-review

13 Scopus citations


About half of the CO2 emitted by fossil fuel combustion currently remains in the atmosphere. The other half is removed by CO2 uptake on land and in the ocean. Prediction of future CO2 concentrations relies critically on the understanding of these sources and sinks and their potential variability over time. While such understanding requires quantification of individual carbon fluxes, the means to achieve this in direct measurements are very limited. The isotopic composition of atmospheric CO2 provides a powerful and indispensable tool in that respect. This chapter reviews the methodological and observational basis underlying the use of the isotopic composition of atmospheric CO2 in tracing and interpreting the changes in sources and sinks of CO2 over seasonal, annual, and longer timescales, as well as over different spatial scales. The processes influencing the isotopic 'signatures' associated with specific processes in the contemporary carbon cycle and the usefulness of such signals are discussed. For example: How can annual-scale variations in 13C observations be used to partition CO2 uptake between land and ocean? Why does the decreasing trend in the 13C of atmospheric CO2 over the past 150 years (due to the addition of 13C-depleted CO2 to the atmosphere through fossil fuel combustion) provide an indicator of the carbon turnover rate in the biosphere? Why does the 18O in atmospheric CO2 reflect variability in the plant versus soil fluxes within the land biosphere? Finally, the new frontiers in the application of isotopic analysis of atmospheric CO2, such as the use of laser spectroscopy, our ability to identify variations in the rare, isotopically doubly labeled CO2 molecules (e.g., containing both 13C and 18O), and the measurement of the 17O anomaly in CO2, are explored.

Original languageAmerican English
Title of host publicationTreatise on Geochemistry
Subtitle of host publicationVolume 5: The Atmosphere
EditorsHeinrich D. Holland, Karl K. Turekian
Place of PublicationOxford
PublisherElsevier Inc.
Number of pages34
ISBN (Print)9780080983004
StatePublished - 2014
Externally publishedYes


  • Atmospheric carbon dioxide
  • Carbon cycle flux partitioning
  • Stable isotopes


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