Abstract

Bubbles can be generated at the sea surface by many mechanisms, but the main source is by the entrainment of air in breaking waves. Bubbles will scavenge material from the surrounding water, thus contributing to the cycling of dissolved and particulate organic material. When they burst at the sea surface these bubbles generate a sea salt aerosol contaminated with material scavenged from the sea-surface microlayer and below. Gases will be exchanged between a bubble and the surrounding water while it is submerged. In addition, the breaking waves and surfacing bubble plumes disrupt the surface microlayer, and this may enhance transfer of gases directly through the sea surface.

The net transfer of a gas between a bubble and the surrounding water, from entrainment until the bubble bursts or fully dissolves, contributes to the total transfer of that gas between atmosphere and ocean. This bubble-mediated transfer has some special properties that set it apart from direct air–sea transfer of poorly soluble gases. Bubble-mediated air–sea transfer velocities depend on the solubility in addition to the molecular diffusivity of the gas in seawater. Bubble-mediated transfer is not proportional to air–sea concentration difference, but is biased toward injection and the forcing of supersaturation. The entrainment of air by breaking waves increases rapidly in intensity with higher wind speeds.