Sources of variations in total column carbon dioxide

Observations of gradients in the total CO_2 column, (CO2), are expected to provide improved constraints on surface fluxes of CO_2. Here we use a general circulation model with a variety of prescribed carbon fluxes to investigate how variations in (CO_2) arise. On diurnal scales, variations are small and are forced by both local fluxes and advection. On seasonal scales, gradients are set by the north-south flux distribution. On synoptic scales, variations arise due to large-scale eddy-driven disturbances of the meridional gradient. In this case, because variations in (CO_2) are tied to synoptic activity, significant correlations exist between (CO_2) and dynamical tracers. We illustrate how such correlations can be used to describe the north-south gradients of (CO_2) and the underlying fluxes on continental scales. These simulations suggest a novel analysis framework for using column observations in carbon cycle science.

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