Effects of internal waves and bores on acoustic transmissions in the Strait of Gibraltar

Abstract

The Strait of Gibraltar Acoustic Monitoring Experiment was conducted in April 1996 to determine the feasibility of using acoustic methods to make routine, rapidly repeated transport measurements in the Strait of Gibraltar, as well as to explore the acoustic scattering caused by the unique internal wave field in the Strait. The acoustic data from high-frequency (2 kHz) reciprocal transmissions across the Strait are unique in that they clearly isolate the acoustic effects of passing internal bores without the added complexity of surface and bottom interactions. Although the acoustic scattering caused by each passing internal bore is different, some common characteristics can be identified. The challenge is to explain these acoustic observations in terms of the physical processes occurring. Acoustic propagation models through range- and time-dependent sound-speed fields representing the Strait and perturbed by internal bore models are being used to understand these observations and to determine to what aspects of the bore the acoustics are most sensitive.