On the global oxygen anomaly and air‐sea flux

We present a new climatology of monthly air‐sea oxygen fluxes throughout the ice‐free surface global ocean. The climatology is based on weighted linear least squares regressions using heat flux monthly anomalies for spatial and temporal interpolation of historical O 2 data. The seasonal oceanic variations show that the tropical belt (20°S‐20°N) is characterized by relatively small air‐sea fluxes when compared to the middle to high latitudes (40°–70°). The largest and lowest seasonal fluxes occur during summer and winter in both hemispheres. By means of an atmospheric transport model we show that our climatology is in better agreement with the observed amplitude and phasing of the variations in atmospheric O 2 /N 2 ratios because of seasonal air‐sea exchanges at baseline stations in the Pacific Ocean than with previous air‐sea O 2 climatologies. Our study indicates that the component of the air‐sea O 2 flux that correlates with heat flux dominates the large‐scale air‐sea O 2 exchange on seasonal timescales. The contribution of each major oceanic basin to the atmospheric observations is described. The seasonal net thermal (SNO T ) and biological (SNO B ) outgassing components of the flux are examined in relation to latitudinal bands, basin‐wide, and hemispheric contributions. The Southern Hemisphere's SNO B (∼0.26 Pmol) and SNO T (∼0.29 Pmol) values are larger than the Northern Hemisphere's SNO B (∼0.15 Pmol) and SNO T (∼0.16 Pmol) values (1 Pmol = 10 15 mol). We estimate a global extratropical carbon new production during the outgassing season of 3.7 Pg C (1 Pg = 10 15 g), lower than previous estimates with air‐sea O 2 climatologies.