Multiple mechanisms generate a universal scaling with dissipation for the air-water gas transfer velocity

Abstract

A large corpus of field and laboratory experiments support the finding that the water side transfer velocity kL of sparingly soluble gases near air-water interfaces scales as kL∼(νε)1/4, where ν is the kinematic water viscosity and ε is the mean turbulent kinetic energy dissipation rate. Originally predicted from surface renewal theory, this scaling appears to hold for marine and coastal systems and across many environmental conditions. It is shown that multiple approaches to representing the effects of turbulence on kL lead to this expression when the Kolmogorov microscale is assumed to be the most efficient transporting eddy near the interface. The approaches considered range from simplified surface renewal schemes with distinct models for renewal durations, scaling and dimensional considerations, and a new structure function approach derived using analogies between scalar and momentum transfer. The work offers a new perspective as to why the aforementioned 1/4 scaling is robust.