Stratospheric Radiocarbon in the Twenty-First Century: Comparing Measurements and Model Results

Measurements of ¹⁴CO₂ on whole-air samples collected cryogenically from balloon flights in 2003, 2004 and 2005, along with simultaneous measurements of other long-lived stratospheric tracers (such as nitrous oxide, methane, and CFCs), are compared with model results from the Lawrence Livermore National Laboratory 3D chemical transport model IMPACT. Year-to-year variations are examined in order to quantify the contributions of the time-dependent carbon-14 production rates, variations in stratospheric transport, and the Suess Effect due to fossil fuel burning in the troposphere that propogates into the stratosphere. Implications for radiocarbon studies at Earth's surface that aim to quantify the partitioning of carbon between the atmosphere, oceans, and terrestrial biosphere will be discussed.