Examining a coupled climate model using CFC‐11 as an ocean tracer

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Abstract
Anthropogenic CFC‐11 dissolved in seawater is used to analyze ocean ventilation simulated in a global coupled air‐sea model. Modeled CFC‐11 distributions are compared to observations gathered on three Southern Hemisphere research cruises. The total amount of CFC‐11 absorbed by the model's Southern Ocean is realistic, though some notable differences in the vertical structure exist. Observed and simulated CFC‐11 distributions are qualitatively consistent with the coupled model's predictions that the ocean may delay greenhouse gas‐induced warming of surface air temperatures at high southern latitudes. The sensitivity of model‐predicted CFC‐11 levels in the deep Southern Ocean to the choice of gas exchange parameterization suggests that quantitative assessments of model performance based upon simulated CFC‐11 distributions can be limited by air‐sea gas flux uncertainties in areas of rapid ocean ventilation. Such sensitivities can complicate the quantitative aspects of CFC‐11 comparisons between models and observations, and between different models.