Sources of variations in total column carbon dioxide

Observations of gradients in the total CO2 column, CO2 , are expected to provide improved constraints on surface fluxes of CO2 . Here we use a general circulation model with a variety of prescribed carbon fluxes to investigate how variations in CO2 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 CO2 are tied to synoptic activity, significant correlations exist between CO2 and dynamical tracers. We illustrate how such correlations can be used to describe the north-south gradients of CO2 and the underlying fluxes on continental scales. These simulations suggest a novel analysis framework for using column observations in carbon cycle science.