ASA 127th Meeting M.I.T. 1994 June 6-10

3aAO8. High-frequency acoustic propagation measurements during solitary wave events on the eastern continental shelf edge.

Edward R. Levine

Richard R. Shell

Michael R. Medeiros

Code 8212, Naval Undersea Warfare Ctr., Division Newport, Newport, RI 02841

High-frequency environmental acoustics studies were conducted during July 1993, on the continental shelf edge east of New Jersey. Internal solitons previously observed in this region near the shelf/slope front propagate in packets, usually in the summer seasonal thermocline, and have been associated with anomalous low frequency sound propagation. Acoustic pings were collected using a towed sled instrumented with sonar arrays. Synoptic measurements to characterize the solitons including sound velocity profiles sampled every 10 min over a tidal cycle, and moored data including current, temperature, and conductivity. Acoustic measurements were taken during sled tows parallel to the bottom bathymetry, normal to the propagation direction, over a region determined from bottom cores to be nearly homogeneous fine sand. Measurements were taken using the sled as a source for backscatter measurements, and also using moored acoustic sources and the sled based transducers as receivers. The observed solitons had amplitudes of approximately 10 m and periods of several minutes. The backscatter variability during soliton events was observed to approximately 10--20 dB, and will be compared to modeled predictions based on environmental data.