The past decade has seen a substantial amount of research on air-sea gas exchange and its environmental controls. These studies have significantly advanced the understanding of processes that control gas transfer, led to higher quality field measurements, and improved estimates of the flux of climate-relevant gases between the ocean and atmosphere. This review discusses the fundamental principles of air-sea gas transfer and recent developments in gas transfer theory, parameterizations, and measurement techniques in the context of the exchange of carbon dioxide. However, much of this discussion is applicable to any sparingly soluble, non-reactive gas. We show how the use of global variables of environmental forcing that have recently become available and gas exchange relationships that incorporate the main forcing factors will lead to improved estimates of global and regional air-sea gas fluxes based on better fundamental physical, chemical, and biological foundations.

The SOLAS Air‐Sea Gas Exchange (SAGE) Experiment was conducted in the western Pacific sector of the Southern Ocean. During SAGE, gas transfer velocities were determined using the 3He/SF6 dual gas tracer technique, and results were obtained at higher wind speeds (16.0 m s−1) than in previous open ocean dual tracer experiments. The results clearly reveal a quadratic relationship between wind speed and gas transfer velocity rather than a recently proposed cubic relationship. A new parameterization between wind speed and gas transfer velocity is proposed, which is consistent with previous 3He/SF6 dual tracer results from the coastal and open ocean obtained at lower wind speeds. This suggests that factors controlling air‐sea gas exchange in this region are similar to those in other parts of the world ocean, and that the parameterization presented here should be applicable to the global ocean.

[1] Air-water gas transfer influences CO 2 and other climatically important trace gas fluxes on regional and global scales, yet the magnitude of the transfer is not well known. Widely used models of gas exchange rates are based on empirical relationships linked to wind speed, even though physical processes other than wind are known to play important roles. Here the first field investigations are described supporting a new mechanistic model based on surface water turbulence that predicts gas exchange for a range of aquatic and marine processes. Findings indicate that the gas transfer rate varies linearly with the turbulent dissipation rate to the 1 = 4 power in a range of systems with different types of forcing -in the coastal ocean, in a macro-tidal river estuary, in a large tidal freshwater river, and in a model (i.e., artificial) ocean. These results have important implications for understanding carbon cycling.