In studies using timeseries observations of atmospheric O2/N2 to infer the fate of fossil fuel CO2, it has been assumed that multi-year trends in observed O2/N2 are insensitive to interannual variability in air-sea fluxes of oxygen. We begin to address the validity of this assumption by investigating the magnitude and mechanisms of interannual variability in the flux of oxygen across the sea surface using a North Atlantic biogeochemical model. The model, based on the MIT ocean general circulation model, captures the gross patterns and seasonal cycle of nutrients and oxygen within the basin. The air-sea oxygen flux exhibits significant interannual variability in the North Atlantic, with a standard deviation (0.36 mol m-2 y-1) that is a large fraction of the mean (0.85 mol m-2 y-1). This is primarily a consequence of variability in winter convection in the subpolar gyre. ¿ 2000 American Geophysical Union