A first estimate of present and preindustrial air-sea CO2 flux patterns based on ocean interior carbon measurements and models



[1] The exchange of CO2 across the air-sea interface is a main determinant of the distribution of atmospheric CO2 from which major conclusions about the carbon cycle are drawn, yet our knowledge of atmosphere-ocean fluxes still has major gaps. A new analysis based on recent ocean dissolved inorganic carbon data and on models permits us to separately estimate the preindustrial and present air-sea CO2 flux distributions without requiring knowledge of the gas exchange coefficient. We find a smaller carbon sink at mid to high latitudes of the southern hemisphere than previous data based estimates and a shift of ocean uptake to lower latitude regions compared to estimates and simulations. The total uptake of anthropogenic CO2 for 1990 is 1.8 (±0.4) Pg C yr−1. Our ocean based results support the interpretation of the latitudinal distribution of atmospheric CO2 data as evidence for a large northern hemisphere land carbon sink.