Natural films in coastal waters

Mesoscale ocean phenomena such as eddies are often depicted by characteristic film patterns. Surface slicks dampen out the centimetre-scale surface waves, causing a low radar backscatter signal. Similar backscatter values are found for e.g. oil spill and grease ice. In order to investigate the composition of the natural films or the so called surface microlayer, samples of the sea surface were for the first time taken simultaneously with ERS-1 SAR coverage of the relevant area. Both slick and nonslick sites were included in the experiment. The samples were analyzed for differences in several chemical parameters to verify whether the dark patches in the SAR image could be related to increased biological activity, i.e. to natural film. A chemical difference between slicked and non-slicked areas corresponding to respectively dark and brighter areas in the ERS-1 SAR image was identified.