UC San Diego

This work primarily concentrates on establishing a long- term, continuous measurement program of atmospheric Ar/N₂. The atmospheric argon and nitrogen cycles should be dominated by ocean ingassing and degassing due to air-sea heat exchange, which links the heat and chemistry cycles through changes in solubility. Atmospheric Ar/N₂ can thus serve as a tracer of air-sea heat flux and ocean heat storage on both seasonal and interannual time scales, providing an independent estimate of the long-term warming of the earth's oceans due to global warming. In this dissertation, I use simple box models to develop the argument that Ar/N₂ measurements should yield useful information on air-sea heat flux. I also employ predictions from a comparative project testing atmospheric transport models to create global maps of the expected seasonal cycle in atmospheric Ar/N₂. I then describe the development of a continuous air intake system that is coupled with an existing mass spectrometer. I discuss the technical issues associated with calibration, especially the recognition of thermal fractionation at the sampling inlet. This result has already led to changes in the way atmospheric flask sampling is performed at stations as well as allowing continuous measurements with a precision of 2-3 per meg over an hour. Lastly, I present the first 17 months of semi-continuous data measured at the Scripps Pier, La Jolla, CA, showing a seasonal cycle of 9 per meg. Parallel measurements of O₂/N₂ and Ar/N₂ allow the seasonal cycle in air-sea O₂/N₂ flux to be partitioned into components due to heat flux and changes in ocean biology and stratification. The annual cycle is overlaid with significant synoptic variability, which has been observed at this level for the first time. The correlation between the deviations in Ar/N₂ and O₂/N₂ suggest that these changes may be due to changes in air- sea heat flux or atmospheric transport, however the anomalies are not clearly driven by regional or local changes in air-sea heat flux. It is possible that instrumental issues remain to be worked out, but the anomalies may also hint at unexpected complexities in the atmospheric Ar/N₂ cycle