Film drop production over a wide range of liquid conditions

Bursting bubbles at the ocean surface can produce liquid drops which transport material into the atmosphere, impacting global climate dynamics through radiative balance and cloud condensation nuclei. Film drops are one of two primary types of spray. We present an extensive experimental study on film drop production, for a wide range of physicochemical liquid conditions, salinity, temperature in saltwater, and small contamination by surfactant. We discuss how thinning and rupture models in the literature are able to describe the film thickness at bursting, bubble lifetime, and number of supermicron film drops emitted. Existing theories for the film drainage rate and number of film drops are shown to be robustly consistent with the experimental results, and we provide prefactors of the scaling equations to enable their implementation into sea spray emission functions. The bubble's lifetime remains poorly described by existing scalings. While significant scatter remains when considering the film thickness at bursting, existing theories describe reasonably well the mean values when varying viscosity, temperature or surfactant contamination. However, we show that varying salinity induces a shift in film thickness which cannot be explained by existing scaling theories.