Volume-Scattering Measurements at 12 kc/sec in the Western Pacific

Acoustic volume scattering data at 12 kc/sec from 14 deep-water areas lying in the region 5°–45°N and 115°–175°E in the Western Pacific are presented. Results are shown graphically as volume-scattering coefficient (and scattering strength) vs depth. Volume-scattering-coefficient values (expressed in decibel form) range from about −50 to −95 dB. There is considerable variation from area to area; the more southerly areas have the lower scattering coefficients, and scattering layers observed there are less well defined. Most intense scattering occurred in an area northeast of Honshu, Japan, where layers 500 ft thick with a peak scattering coefficient near −50 dB were observed. Scattering levels show a rough dependence on latitude and a somewhat stronger correlation with estimates of organic productivity. Volume-scattering coefficients observed off Southern California are usually higher by 5–15 dB than those in the Western Pacific areas.