Natural and man-made sea slicks in the North Sea investigated by a helicopter-borne 5-frequency radar scatterometer

Abstract In April 1994 natural sea slicks and five man-made slicks, which were spread as a pure substance and from two different spreading solvents, n-hexane and ethanol, respectively, were overflown by a helicopter carrying a five-frequency multi-polarization radar scatterometer, the so-called Heliscat. For the first time, natural sea slicks were successfully simulated by spreading hexadecanoic acid methyl ester (palmitic acid methyl ester (PME)), representing the fatty acid fraction of biogenic slicks, from the spreading solvent ethanol. It is shown that the different slick generation procedures (pure substance, spreading solvents n-hexane or ethanol) give rise to different influences on backscattered radar signals: a PME slick spread from ethanol induces slightly stronger suppressions of the radar backscattering than a PME slick spread from n-hexane; the wave damping maximum of oleyl alcohol (OLA) spread as a pure substance is shifted to higher wave numbers as compared to OLA slicks spread from solvent...

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