Detection of Oil Under Ice: An Acoustic Reverberation Method

Through new exploration and aging infrastructure, there is an ever-increasing risk of oil spills or leaks into natural bodies of water, but presently there is no low-cost method to actively monitor for such spills under ice cover, particularly not any method giving rapid coverage of a large area. Therefore, a method based on acoustic reverberation time under the ice was investigated. A broadband, impulsive acoustic source generating a frequency band of 10-90 kHz was used in a water tank with a layer of naturally-grown ice for a scaled feasibility study of this method; this band provided appropriately short wavelengths, scaled for the small tank environment. Reflections from the tank walls were minimized, and a diffuse environment within the tank allowed for extraction of a reverberation time with a hydrophone. Results show an oil presence changed the reverberation time as compared to an oil-free ice layer across all diffuse frequency bands.