Abstract:
In order to constrain the processes controlling the cycles of biogeochemically important
gases such as 02 and C02, and thereby infer rates of biological activity in the upper ocean
or the uptake of radiatively important "greenhouse" gases, the noble gases are used to
characterize and quantify the physical processes affecting the dissolved gases in aquatic
environments. The processes of vertical mixing, gas exchange, air injection, and
radiative heating are investigated using a 2 year time-series of the noble gases,
temperature, and meteorological data from Station S near Bermuda, coupled with a 1-
dimensional upper ocean mixing model to simulate the physical processes in the upper
ocean. The rate of vertical mixing that best simulates the thermal cycle is 1.1±0.1 x104 m
The gas exchange rate required to simulate the data is consistent with the formulation
of Wanninkhof (1992) to ± 40%, while the formulation of Liss and Merlivat 1986 must
be increased by a factor of 1.7± 0.6. The air injection rate is consistent with the
formulation of Monahan and Torgersen (1991) using an air entrainment velocity of 3±1
cm s1. Gas flux from bubbles is dominated on yearly time-scales by larger bubbles that
do not dissolve completely, while the bubble flux is dominated by complete dissolution of
bubbles in the winter at Bermuda. In order to obtain a high-frequency time-series of the
noble gases to better parameterize the gas flux from bubbles, a moorable, sequential
noble gas sampler was developed. Preliminary results indicate that the sampler is capable
of obtaining the necessary data. Dissolved gas concentrations can be significantly
modified by ice formation and melting, and due to the solubility of He and Ne in ice, the
noble gases are shown to be unique tracers of these interactions. A three-phase
equilibrium partitioning model was constructed to quantify these interactions in
perennially ice-covered Lake Fryxell, and this work was extended to oceanic
environments. Preliminary surveys indicate that the noble gases may provide useful and
unique information about interactions between water and ice.
