How we detect an oil spill

Because of its viscous property, oil forms a film-like coverage on the ocean surface. This film modifies the surface tension of the water and therefore dampens the small capillary waves that are present on “clean seas”. Capillary waves reflect radar energy producing a “bright” backscatter or a sea clutter signature on radar images. In contrast, oil on the ocean surface is detected as “dark” signatures. Our experienced analysts use the resulting backscatter characteristics, in conjunction with the elements of tone, texture, shape, meteo-oceanic conditions, and geographical location to identify and classify possible oil anomalies and rule out possible false positives on each image.

Using satellite imagery up to 90,000 km2 of ocean can be surveyed within minutes and notifications issued in near-real time.  The analysis is done seven days a week, throughout the year, independent of weather or darkness.

Pollution surveillance aircraft
© Transport Canada

Spill Verification

Possible detections are signalled to regional enforcement and response agencies and the aircraft of the National Aerial Surveillance Program (NASP).  The ISTOP program monitoring reports provide information on the location of the spill, areal extent, length and nearby ship positions.

The near-real time notification makes the most efficient use of the aircraft by pinpointing the area of interest in the vast ocean.  Evidence gathered by the flight crews, supported by the satellite monitoring reports, are used to enforce domestic and international laws and conventions on pollution.

The analysis information is used by wildlife biologists, enforcement and emergency response personnel to monitor changes in polluter’s habits. Environment Canada’s Emergencies Science and Technology Section in Ottawa can supply computer generated hindcast and forecast models of the origin of the slick as well as to where it may have naturally dispersed.