Molecular oxygen in the atmosphere is linked to the carbon cycle by photosynthesis and respiration, and can be used as a tracer for studying elusive problems of carbon geochemistry. Oxygen is relatively insoluble in seawater. Its atmospheric inventory, in contrast to the of carbon dioxide, is not buffered by equilibrium with the oceans. Global carbon and oxygen fluxes are therefore nearly quantitatively reflected in the changing atmospheric oxygen concentration, and one can use the atmospheric oxygen content as an integrator of seasonal and interannual fluxes of carbon and oxygen. The goal of this research project is to, develop an isotope dilution - isotope ratio mass spectrometry method and to evaluate its capability for measuring small changes in the atmospheric oxygen. Together with the ongoing work of others this work will also set the stage for more extensive future studies of the atmospheric oxygen cycle and its implications for the oceanic carbon cycle and the total rate of anthropogenic carbon dioxide production. Oxygen is also linked to the carbon cycle by the combustion of fossil fuels and the global conversion of biomass into carbon dioxide. There must be a gradual global decrease in the atmospheric oxygen content which quantitatively reflects the total rate oxygen consumption by these two processes. The consumption rate by fossil fuel burning is well known. One can thus measure the long term anthropogenic oxygen decrease, and calculate the biomass conversion rate by difference.
