A new constraint on global air-sea CO sub(2) fluxes using bottle carbon data

We develop a new observationally derived monthly ocean surface climatology for the partial pressure of CO sub(2) (pCO sub(2)) that allows an independent data-based constraint on contemporary air-sea CO sub(2) fluxes. Our approach uses a neural network, trained on ~17,800 bottle-derived measurements of pCO sub(2), to diagnose monthly pCO sub(2) levels from standard ocean hydrographic data. Although the pattern of contemporary air-sea CO sub(2) fluxes is generally consistent with the independent underway pCO sub(2) data network, we find a strong shift in the magnitude of oceanic sources and sinks of CO sub(2). In particular, we find a contemporary Southern Hemisphere oceanic CO sub(2) uptake of 0.93 PgC/year, driven by a prominent CO sub(2) sink in the subpolar region (25 degree S-60 degree S), that is five times the magnitude of the Northern Hemisphere oceanic sink (0.18 PgC/year). Globally, our results suggest a net open-ocean CO sub(2) sink of 1.55 plus or minus 0.32 PgC/year for the nominal year of 2000. Key Points * New data-based approach to diagnose monthly surface ocean p CO sub(2) distributions * Independent constraint on global air-sea CO sub(2) flux distribution and magnitude * Southern Hemisphere carbon uptake is five times the magnitude of the Northern Hemisphere