Interannual variability of air-sea O2 fluxes and the determination of CO2 sinks using atmospheric O2/N2



[1] Motivated by the use of atmospheric O2/N2 to determine CO2 sinks under the assumption of negligible interannual variability in air-sea O2 fluxes, we examine interannual fluctuations of the global air-sea flux of O2 during the period 1980–1998 using a global ocean circulation and biogeochemistry model along with an atmospheric transport model. It is found that both the El Niño/Southern Oscillation (ENSO) cycle and wintertime convection in the North Atlantic are primary drivers of global air-sea oxygen flux interannual variability. Model estimated extremes of O2 flux variability are −70/+100 × 1012 mol/yr (Tmol/yr), where positive fluxes are to the atmosphere. O2/N2 variability could cause an up to ±1.0 PgC/yr error in estimates of interannual variability in land and ocean CO2 sinks derived from atmospheric O2/N2 observations.