A review of the status of advanced technologies for the detection of oil in and with ice

Remote sensors for application to oil in ice and oil with ice are assessed. Radio-frequency methods to detect oil in ice depend on the difference in d ielectric properties between oil and water. Freshwater ice is relatively tr ansparent to frequencies below about 200 MHz. Despite extensive theoretical studies, there is a lack of experimental evidence to support the notion th at radio-frequency methods have potential. Acoustic methods for the detection of oil in ice show promise. Regular meta l inspection equipment is capable of detecting oil layers under ice. Oil pr opagates shear waves and detection methods based on this unique property ar e capable of identifying oil in ice. One unit has been built and tested in the field based on this principle. Oil with ice detection is a well developed technology. A common sensor is a n infrared camera or an IR/UV (infrared/ultraviolet) system. The inherent w eaknesses include the inability to discriminate oil on beaches, among weeds or debris. The laser fluorosensor is a most useful instrument because of i ts unique ability to identify oil on backgrounds that include water, soil, ice and snow. It is the only sensor that can positively discriminate oil on most backgrounds. Radar offers the only potential for large area searches and foul weather remote sensing, however, there is little potential to dete ct oil in the immediate vicinity of ice. A major weakness of radar is that it is limited to operation over seas with winds of about 2-8 m/s. Equipment operating in the visible region of the spectrum, such as cameras and scanners, is useful for documentation or providing a basis for the over lay of other data. It is not useful beyond this because oil shows no spectr al characteristics in the visible region that can be used to discriminate o il. (C) 2001 Elsevier Science Ltd. All rights reserved.