Acoustic remote sensing of internal solitary waves and internal tides in the Strait of Gibraltar

Tiemann, CO, Worcester PF, Cornuelle BD.  2001.  Acoustic remote sensing of internal solitary waves and internal tides in the Strait of Gibraltar. Journal of the Acoustical Society of America. 110:798-811.

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High-frequency underwater acoustic transmissions across the Strait of Gibraltar are used to examine the feasibility of acoustically measuring several physical processes in the Strait, a difficult area to sample with conventional instruments. Internal undular bores propagate along the interface between an upper layer of Atlantic water and a lower layer of Mediterranean water. As they cross the acoustic path they are recognized by their scattering effects in the acoustic record. The time between internal bore crossings is influenced more by the tidal phase of the bore release at the Camarinal Sill than by variability in the bore's propagation time to the acoustic path. When internal bores were present, the acoustic arrival patterns could be classified as one of three types with different internal bore and internal tide amplitudes. The arrival types alternate during spring to neap tide transitions, suggesting that internal bore amplitude is not linearly related to tidal height. The sensitivity of acoustic observables to several physical parameters is investigated using a forward model, and a demonstration of inverse techniques provides estimates of several physical parameters from spring tidal cycles. (C) 2001 Acoustical Society of America.