Impact of an artificial surfactant release on air-sea gas fluxes during Deep Ocean Gas Exchange Experiment II

During the 2007 UK SOLAS Deep Ocean Gas Exchange Experiment in the northeast Atlantic Ocean, we conducted the first ever study of the effect of a deliberately released surfactant (oleyl alcohol) on gas transfer velocities (k_w) in the open ocean. Exchange rates were estimated with the ³He/SF₆ dual tracer technique and from measured sea-to-air DMS fluxes and surface water concentrations. A total of seven k_w estimates derived from ³He/SF₆ were made, two of which were deemed to be influenced by the surfactant. These exhibited suppression from ∼5% to 55% at intermediate wind speeds (U₁₀) in the range 7.2-10.7 m s^-1. Similarly, k_w determined from DMS data (k_DMS) was also depressed by the surfactant; suppression ranged from ∼39% at 5.0 m s^-1 to ∼24% at 10.8 m s^-1. Surfactant thus has the potential to measurably suppress gas exchange rates even at moderate to high wind speeds.