Observations of rising methane bubbles in Trondheimsfjord and its implications to gas dissolution

Abstract

Gas dissolution reduces the release of methane to the atmosphere from subsea sources. Being able to predict and assess the methane flux to the atmosphere requires knowledge on gas dissolution and mass transfer. This can be obtained by studying the size evolution of bubbles rising in water. New data of bubble size evolution have been obtained by releasing, tracking, and filming methane bubbles with an ROV in the Trondheimsfjord from depths varying between 100 and 300 m. Released bubbles had an initial diameter between 5 and 7 mm and were tracked until they reached a diameter of roughly 2 mm. The new data were compared against theory, applying established correlations for the mass transfer coefficient. There was an inconsistency between experiment and theory. Thus, new correlations for the mass transfer are proposed. The new correlations are consistent with both the new experiments and previously published experiments. They indicate that the conditions in the ocean can be labeled as partly contaminated with respect to mass transfer.

Observations of rising methane bubbles in Trondheimsfjord and its implications to gas dissolution