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Oil Pollution

© ESA 1996 . ERS Image, South China Sea | Oil slicks on the ocean surface are detectable in SAR images because the small scale waves in the slick- covered areas are suppressed by the oil. Since the radar backscatter from the ocean surface depends on the magnitude of these short scale waves, the image intensity in these areas will be significantly lower than the surrounding area.

Thus, oil slicks appear as dark patches in SAR images. Oil slick is most readily observed in SAR images when the sea surface wind speed is between 2 m/s to 10 m/s.

Besides man-made spills, naturally occurring slicks due to marine organic materials also produce similar effects on the ocean surface. These signatures are commonly observed in coastal waters where biological activity is the greatest. Oil spill may be distinguished from these natural slicks by a study of the shape of the slicks in SAR images.
The two images in this page shows oil being discharged by ships into the sea.
© ESA 1996 . ERS Image, Near Singapore