ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2aAO1. The internal tide of the western North Atlantic observed using long-range reciprocal acoustic transmissions.

Brian D. Dushaw

A.P.L., Univ. of Washington, 1013 NE 40th St., Seattle, WA 98105-6698

Peter F. Worcester

Bruce D. Cornuelle

Univ. of California, La Jolla, CA 92093-0213

Bruce M. Howe

Univ. of Washington, Seattle, WA 98105-6698

Time series of ray travel times were obtained at 350-, 410-, and 670-km ranges in the western North Atlantic during the 1991--2 Acoustic Mid-Ocean Dynamics Experiment (AMODE). Transmissions were recorded for approximately 300 days between six transceivers in a pentagonal array. Sound-speed variability is separated from current variability by calculating the sum of reciprocal travel times. Both phase-locked and narrow-band internal-tide sound-speed variability, caused by the internal-tide isotach displacement, are observed by the sum travel times. The description of the acoustic array as a high-directivity antenna for the incident internal tide will be given. Beamforming the internal tide M[sub 2] and K[sub 1] harmonic constants determined on each of the 15 acoustic paths suggests two origins of significant internal tide generation are the Blake Escarpment and the continental shelf north of Puerto Rico. The nontidal, high-frequency variability (>1 cpd) is due to internal-wave sound-speed and current variability.