The impact of deep internal tides on acoustic propagation

Strong deep (~250 m) internal tides have been observed off the south shores of Oahu. These tides result in large fluctuations in temperature (6-8°C) on a semi-diurnal basis, and in turn change the sound speed structure of the region where present. The authors quantify the impact of these tidally-induced sound speed variations on sonar system performance. Examples include an ASW (Anti-Submarine Warfare) sonar and its ability to localize sources. Finally, they comment on the ability to specify the water column characteristics (temperature T and salinity S versus depth) using the U.S. Navy´s Modular Ocean Data Assimilation System (MODAS), including some limitations of MODAS in providing an estimate of the sound speed environment of a region with time