Sources of variations in total column carbon dioxide
Observations of gradients in the total CO2 col- umn, ⟨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 investi- gate how variations in ⟨CO2⟩ arise. On diurnal scales, varia- tions are small and are forced by both local fluxes and advec- tion. 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 gradi- ent. In this case, because variations in ⟨CO2⟩ are tied to syn- optic 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 simu- lations suggest a novel analysis framework for using column observations in carbon cycle science.