Laboratory measurements of rise velocity for individual, hydrate-free and hydrate-coated gas bubbles in water

Tracking methane transport becomes more complicated in the deep ocean where seafloor release of methane gas bubbles occurs at the high pressures and low temperatures conducive to hydrate formation on bubble surfaces. Gas hydrate formation can make the bubble surface rigid, preventing the dynamic interplay between bubble size, shape and rise velocity that gas-transport models commonly rely upon when using bubble size to predict bubble rise velocity. To better constrain gas-transport model predictions, we conducted controlled laboratory measurements of rise velocity, u_z, for hydrate-free air, methane, and xenon bubbles and hydrate-coated xenon bubbles. Experimental results for u_z were compared to predicted u_z values from several published parameterizations used to study dissolution of gas bubbles rising in the ocean. For both hydrate-free and hydrate-coated gas bubbles, the McGinnis et al. (2006) parameterization provides the most accurate u_z predictions.