ACOUSTIC ATTENUATION IN SEA ICE (PART 1); REFLECTION OF SOUND AT THE WATER-ICE INTERFACE (PART 2)
MCGILL UNIV MONTREAL (QUEBEC) MACDONALD PHYSICS LAB
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Measurements of the attenuation of acoustic waves in sea ice at frequencies between 10 kHz and 500 kHz were made on the ice cover at Tanquary Fiord, Ellesmere Island latitude 81 degrees 25 min N, longitude 76 degrees 50 min W during April-May in 1967 and again in 1969. A horizontal transmission path at a depth of 4 ft, mid-way between the top and bottom surfaces of the ice cover, was used at ranges of 4 ft to 25 ft between piezoelectric transducers immersed in oil-filled bore holes. In an auxiliary experiment in 1969, measurements of the specular reflection of water-borne sound at the water-sea ice interface were made as a function of angle of incidence. The geometric configuration was such that a constant path aligned carefully at each angle of incidence to match this configuration thus obviating the necessity of having to make corrections for range and for directionality characteristics of the transducers. The amplitude reflection coefficient was found to have a value near 0.1 for near-normal angles of incidence but its value was found to increase rapidly with increasing angle of incidence beyond 30 degrees.
- Snow, Ice and Permafrost