Novel applications of carbon isotopes in atmospheric CO2: What can atmospheric measurements teach us about processes in the biosphere?

A. P. Ballantyne, J. B. Miller, I. T. Baker, P. P. Tans, J. W.C. White

Research output: Contribution to journalArticlepeer-review

Abstract

Conventionally, measurements of carbon isotopes in atmospheric CO 213CO 2) have been used to partition fluxes between terrestrial and ocean carbon pools. However, novel analytical approaches combined with an increase in the spatial extent and frequency of δ 13CO 2 measurements allow us to conduct a global analysis of δ 13CO 2 variability to infer the isotopic composition of source CO 2 to the atmosphere (δ s). This global analysis yields coherent seasonal patterns of isotopic enrichment. Our results indicate that seasonal values of δ s are more highly correlated with vapor pressure deficit (r = 0.404) than relative humidity (r = 0.149). We then evaluate two widely used stomatal conductance models and determine that the Leuning Model, which is primarily driven by vapor pressure deficit is more effective globally at predicting δ s (RMSE = 1.6‰) than the Ball-Woodrow-Berry model, which is driven by relative humidity (RMSE = 2.7‰). Thus stomatal conductance on a global scale may be more sensitive to changes in vapor pressure deficit than relative humidity. This approach highlights a new application of using δ 13CO 2 measurements to validate global models.

Original languageEnglish
Pages (from-to)3093-3106
Number of pages14
JournalBiogeosciences
Volume8
Issue number10
DOIs
StatePublished - 2011

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