Seasonal and interannual variations in atmospheric oxygen and implications for the global carbon cycle

Measurements of changes in atmospheric molecular oxygen using a new interferometric technique show that the O₂ content of air varies seasonally in both the Northern and Southern Hemispheres and is decreasing from year to year. The seasonal variations provide a new basis for estimating global rates of biological organic carbon production in the ocean, and the interannual decrease constrains estimates of the rate of anthropogenic CO₂ uptake by the oceans.