Low‐frequency propagation across the East Greenland Frontal Zone: Directional dependence of acoustic modes

Abstract

In a previous paper [L. E. Mellberg et al., J. Acoust. Soc. Am. Suppl. 1 77, S56 (1985)], an analysis was conducted to determine the relative importance of acoustic propagation modes (bottom bounce, surface duct, and convergence zone) for a shallow source (10 m) along a 100 nmi west to east track through the East Greenland Frontal Zone. In the present paper, a comparison is made to results obtained for a reciprocal east to west track through the zone to determine the directional dependence of the dominant acoustic modes. Along the west to east track, outward from the ice edge and the East Greenland Current, there is a transition from surface duct to convergence zone as the principal propagation mode. This transition, as well as the initial bottom slope, restricts the envelope of ray angles found in this convergence zone mode. For the east to west track, the convergence zone is the dominant mode along the entire path and its character changes significantly. The directional dependence of these modes result in marked changes in propagation loss with range and the energy fields as generated by the two sources. [Work supported by ONR and NUSC.]