SAR Image of Oil Slicks in the Atlantic

Because SAR image brightness is dependent upon surface geometry, SAR data is extremely useful for observing the surface features of the ocean. This SAR image of the Atlantic Ocean, close to Angola, shows many slicks resulting from oil naturally seeping from the ocean floor. The image is dark where the slicks occur not because of the colour of oil, but because the oil damps down small surface waves and the smoother surface reflects more of the transmitted signal away from the satellite. SAR imagery will also readily detect oil slicks coming from ships, however the changing alignment of the slicks here result from multiple static sources in combination with a change in tidal flow.

Such natural seepage can be used to indicate the presence of offshore oil reserves. The large dark areas in the north of this image are from rain affecting surface waves, the source cloud being transparent to the radar signal.