Modeling bubbles and dissolved gases in the ocean

We report on the development of a bubble concentration model and a dissolved gas concentration model for the oceanic boundary layer. The bubble model solves a set of concentration equations for multiple gases in bubbles of different sizes, and the dissolved gas concentration model simulates the evolution of dissolved gases and dissolved inorganic carbon. The models include the effects of advection, diffusion, bubble buoyant rising, bubble size changes, gas exchange between bubbles and ambient water, and chemical reactions associated with the dissolution of CO₂. The formulation consistency and the numerical accuracy are shown by the good agreement with a model describing individual bubble behavior in a test simulating the evolution of a bubble cloud released in the water. To study the bubble and dissolved gas evolution after a single wave-breaking event, the models are coupled with a fluid dynamical Direct Numerical Simulation model with spatially and temporally distributed momentum and bubble injection for a typical breaking wave. The modeled bubble size spectrum compares well with laboratory measurements. The breaker-induced vortex not only advects the bubble-induced dissolved gas anomalies downstream but also entrains the surface diffusion layer to greater depth. Due to the hydrostatic pressure and surface tension exerted on bubbles, gases inside bubbles are able to dissolve in slightly supersaturated water. When the water is highly supersaturated, bubbles add to the venting of dissolved gases.