Environmental Variability at Site Alfa during the Broadband-87 Exercise

• Main Authors: Bucca, Paul J, Meredith, Roger W
• Other Authors: NAVAL OCEAN RESEARCH AND DEVELOPMENT ACTIVITY STENNIS SPACE CENTER MS
• Format: Text
• Language: English
• Published: 1989
• Subjects: Physical and Dynamic Oceanography; Acoustic Detection and Detectors; *ACOUSTIC CHANNELS; *ACOUSTIC MEASUREMENT; *UNDERWATER SOUND SIGNALS; ACOUSTIC VELOCITY; BROADBAND; DISPLACEMENT; FLEET EXERCISES; GULF STREAM; OCEAN BOTTOM; OCEAN CURRENTS; OCEAN ENVIRONMENTS; OCEAN SURFACE; PROFILES; SOUND TRANSMISSION; STABILITY; SURFACE TEMPERATURE; TABLES(DATA); TEMPERATURE; THERMOCLINES; VARIATIONS; WATER MASSES; PE63785N; North Atlantic
• Online Access: http://www.dtic.mil/docs/citations/ADA214666; http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA214666

The Broadband-87 acoustics exercise was an at-sea efforts designed to characterize broadband propagation. This experiment was conducted in two areas of the North Atlantic Ocean Site Alfa, 31 N, 76 W, was chosen for its acoustically bottom-limited conditions and characteristically stable oceanographic environment. Site Delta, 28 N, 67 W, represented an area in which the sound channel is unobstructed by the seafloor. This report documents the comprehensive set of environment data taken at Site Alfa in support of the acoustic measurements. The oceanographic environment was, basically very stable throughout the exercise despite its location in a cold-core eddy of the Gulf Stream. Thermometric satellite imagery collected during the exercise quantified the surface temperature within this eddy to be about 1 C cooler than the surrounding waters. The measurements were collected fully within the confines of the eddy, precluding potentially marked variability resulting from acoustic propagation across dissimilar water masses. A 36 hour time series of temperature data collected during the exercise exhibited a maximum sound speed variation of approximately 6 m/sec in the area of the main thermocline below the 18 C water layer. However, a 15 mile displacement over the duration of these measurements precluded an accurate interpretation of this variability. The most profound effect of the eddy on the conduct of the exercise was the extremely strong surface currents experienced. Expendable Current Profile measurements indicate that near surface currents approaching 5.5 kt were present. Plots and tabulations of all data collected during phase Alfa of Broadband-87 are in the appendices.