Field studies of natural slicks due to internal waves

New observations are presented of natural banded slicks and their associated internal waves (IW), conducted from an oceanographic platform on the Black Sea in June, 1998. Surface waves were measured with X-band and Ka-band radars and with an optical spectrum analyzer operating in the cm and mm surface wavelength ranges; IW were measured with an STD-probe. Surface films were sampled in both slick and non-slick areas, and the film elasticity parameter and film concentration variations were estimated from these samples using laboratory measurements of capillary-gravity wave damping. The estimated film elasticities for the slick bands exceeded 20 mN/m, while those in non-slick areas were only a few mN/m. The most prominent slick bands were detected over IW troughs, in accordance with theory. The relative cm-mm-scale wave damping (contrast) in the slick bands was very high (more than an order of magnitude), reaching a maximum for wavelengths ~1.5 cm. Comparison of observed wave damping in the banded slicks with hydrodynamic modulation over IW in nonslick cases has shown that the presence of surfactants strongly enhances the surface manifestation of the IW