| The scattering and backscattering properties of bubble populations in the upper ocean are estimated with Mie theory and a generalized bubble size spectrum based on in situ observations. Optical properties of both clean bubbles, and bubbles coated with an organic film are analyzed; while the coating changes total scattering by bubbles only slightly, it amplifies the backscattering significantly over the clean bubbles by up to a factor of 5. The comparisons with the corresponding optical properties of micro-organisms indicate that bubbles are at least one order of magnitude more efficient in backscattering than micro-organisms. Given a bubble number density frequently found at sea (from ∼105 to ∼107 M -3), the bubble populations significantly influence the scattering process in the ocean, especially in oligotrophic waters. Bubbles appear to make a large contribution to the missing terms in constructing the observed total backscattering coefficient of the ocean. This contribution to backscattering is strongly enhanced if the bubbles are coated with organic film. The injection of bubbles will shift ocean color toward the green, resembling phytoplankton blooms, and hence introduce error in ocean color remote sensing if its effect is not corrected. |
