The distributions of dissolved O₂ and CO₂ in the global surface ocean have not previously been systematically compared, despite their significance for life and climate. Here we present a new biogeochemical technique to detect different processes impacting their distributions in oceanic surface waters. We apply the approach to the GLODAPv2 and SOCCOM datasets. The GLODAPv2 dataset shows large seasonal variations in surface dissolved O₂ and CO₂. O₂ is typically assumed to return to gas exchange equilibrium with the atmosphere more rapidly than CO₂, but we observed a strong coupling in their deviations from equilibrium. Applied to the profiling SOCCOM float data in the high-latitude Southern Ocean, we detect systematic errors in the CO₂ values as large as 18 μatm, equivalent to ~50% underestimation in sea-to-air CO₂ flux. This demonstrates a strong potential of such technique in identifying biases and improving CO₂ and O₂ data collected by autonomous platforms.

Air-sea disequilibrium,carbon cycle,dissolve oxygen,Southern Ocean,Biogeochemical Argo float