Reverberation from Deep Scattering Layers in the Western North Atlantic

Abstract

Reverberation from deep scattering layers was measured at 37 sites in the western North Atlantic. Resonant scatterers, presumably the swimbladders of bathypelagic fish, were responsible for the bulk of the observed reverberation. Three scattering layers, each populated with a characteristic size of scatterer, were found to persist over distances of several hundred kilometers. During the day, these layers were at depths between 300 and 900 m. A migration towards the sea surface of scatterers from the shallowest layer at sunset appeared to be responsible for most of the low frequency reverberation observed at night. The majority of the scatterers from the deepest of the layers did not experience a daily migration in depth. Two of the layers studied showed pronounced decreases in depth with increasing latitude. No seasonal variations in scattering strengths were observed.