REFRACTION OF SOUND-WAVES AT POLAR LATITUDE

Horizontal refraction in the ocean sound channel is a function of the acoustic mode number and frequency (chromatic aberration), and may lead to wide separations of long-range transmission paths. We consider the 1960 antipodal transmission from Perth, Australia, to Bermuda. The path has a southernmost point in the Indian Ocean, which depends sensitively on horizontal refraction associated with the north-to-south shoaling of the sound axis across the Antarctic Circumpolar Current. (Refraction by the current velocity is relatively small.) This southernmost point is at about 40-degrees-S for low modes of relatively high frequency, and at about 50-degrees-S for high modes of low frequency.