Temporal variability of atmospheric oxygen from both continuous measurements and a flask sampling network: Tools for studying the global carbon cycle

Atmospheric oxygen (O₂) measurements, together with carbon dioxide (CO₂), are useful tools for elucidating mechanisms that influence the global carbon cycle. This dissertation presents a synthesis of data from eleven years of measurements from a global network of flask sampling stations, describes a new method for achieving continuous atmospheric O ₂ measurements, and presents one year of data from a field station deployment of this continuous measurement technique. The eleven-year record shows atmospheric O₂ decreasing, but slower than expected from fossil fuel combustion owing to the influence of land biota. From these data a global carbon budget is calculated for the period from January 1990 to January 2000: fossil fuel combustion produced an average of 6.33 ± 0.38 Gt C/y of CO₂, of which 3.21 ± 0.13 Gt C/y remained in the atmosphere, 1.44 ± 0.66 Gt C/y were taken up by land biota, and 1.68 ± 0.52 Gt C/y were taken up by oceans.; The rate of decrease in atmospheric O₂ and increase in CO ₂ vary from year to year. Analysis of these covariations suggests that exchanges with land biota can account for most of the variation in the CO ₂ growth rate. The amplitudes of the seasonal cycles of atmospheric O₂ also show interannual variations, suggesting that oceanic marine productivity rates vary interannually. Observations such as these highlight the value of long records and the need for higher temporal resolution atmospheric O₂ time series that together can capture variability on time-scales ranging from hours to decades.; The new continuous measurement technique employs an analyzer that utilizes the paramagnetic properties of molecular O₂. The design and development of the analyzer system is discussed, and it is shown to achieve a precision of 1 per meg (≈0.2 ppm) from repeated measurements over a one-hour interval. This system was deployed at Baring Head, New Zealand, where it has collected data since June 1999. These data show high resolution features in the seasonal cycle, and high frequency variability that the land biota and oceans can induce in atmospheric O₂ and CO₂ concentrations.; This dissertation also discusses gas handling issues that are important to consider for accurate determination of precise atmospheric O₂ concentrations.