The surface active sea films: properties and dynamics

Abstract

Surface-active substance (SAS) films play an important role for an interpretation of remote sensing of the ocean surface. A review is presented of the results of the theoretical and experimental (as laboratory well as nature) studies. The physical properties of thin (monomolecular and composite) organic films on the water surface have been studied with accent on the main mechanical characteristics: film pressure and film elasticity (Young modules). These values are responsible for the variations of the dispersive properties of gravity-capillary waves, in particular, the growth of decrement of these waves with the film presence, and the appearance the second type of waves on the water surface covered by thin film-the Marangoni waves. Usually marine films are composed of organic molecules and their specific properties such as hysteresis, connection between the film elasticity and the concentration of the organic matter in the subsurface microlayer and the wind velocity have been observed. A mathematical model of surface film hysteresis is proposed. The exact dispersion relations for linear waves on a fluid surface covered by a film have been obtained and calculated numerically for a wide range of the viscosity and elasticity. The nonlinear theory of the surfactant film effects on short wind ripple within the kinetic equation for the wind wave spectrum is proposed and the results of corresponding field and laboratory tests are reported. The theory of the surface manifestation of internal waves due to surfactant films based on a nonlinear model of the interaction between short wind waves and the current field induced by internal waves, taking into account real properties of the surfactants, is developed.