There is scarcely a subject in biogeochemistry which is more fundamental, yet so poorly understood, as the variability in atmospheric oxygen. Oxygen is an essential element to global life cycles and is consumed by fossil fuel-burning and deforestation; yet the changes in the atmospheric oxygen concentration which must reflect these processes have never been detected. The difficulty is simply that the appropriate technology has not been available for measuring the expected variations in oxygen against the large oxygen background of air. Direct measurements of changes in oxygen would substantially improve the framework for studying the global carbon cycle and the perturbations due to human activities. Specifically, measuring the presumed long term rate of decline in oxygen would provide a basis for establishing the net annual global oxidation from which one could construct accurate figures for the net sources and sinks of carbon from fossil fuel burning and biospheric oxidation. This would provide objective constraints on models of oceanic carbon dioxide uptake which are needed to forecast future carbon dioxide levels and future climate. It would also provide a better basis for understanding whether today's elevated carbon dioxide levels are stimulating global net primary production. This project is designed to investigate the atmospheric oxygen and carbon dioxide fraction in air samples gathered from a series of stations around the world. The purpose of those measurements is to correlate seasonal, latitudinal and secular trends in atmospheric carbon dioxide with variations in oxygen. These data will provide insights into changes in global biomass, and in ocean and land biological productivities. Air samples will be taken in glass flasks and oxygen mole fraction will be referenced to compressed air standards using a recently developed interferometric oxygen analyzer. The measurements will be accompanied by systematic studies of oxygen stability in glass flasks and high pressure cylinders. Other work will include a laboratory feasibility study of obtaining cryogenically extracted air samples from the stratosphere for oxygen analysis, which would be of interest for determining recent oxygen depletion.
