Structure of sound speed in the Gulf of Aden

The environmental characteristics of seawater affect acoustic wave propagation. Physical phenomena such as wind, tides, internal waves, temperature, and salinity variations, temperature and hydrodynamic fronts, and sea currents affect some of the acoustic wave frequencies. In order to simulate sound speed, Mackenzie empirical equation is employed and added to the MITgcm model to calculate sound speed in the domain as a function of temperature, salinity and depth. The model domain is in the range of 7° N-19°N and 44°E-57.1°E. Initial data (temperature, salinity, wind, net heat flux, evaporation and precipitation) were introduced to the model and numerical model was performed for 20 years. Comparison of temperature and salinity results with the measured data shows good agreement. Seasonal profiles of temperature, salinity and speed of sound were also investigated. The results showed that variations in the speed of sound are subject to temperature variations. Moreover, three water masses i.e. surface water mass, middle water mass, and Red Sea water mass are observed in the Gulf of Aden. The saline water of the Red Sea is at a depth of 300 to 800 meters, leading to inversion in the temperature and salinity profiles, resulting in the inversion of the speed of sound profile. In the range of 11.9°N and 44° E to 50°E, the rate of variations in the speed of sound from the surface to the depth of 250 m follow the temperature variations. Also, at depths of 300 to 800 m, due to the presence of the Red Sea water mass, the rate of variations in the speed of sound is due to temperature and salinity. Likewise, in the range of 45.8°E and from 12.8°N to 11°N, from the depth of 300 meters to the seabed, temperature variations were uniform, therefore the speed of sound is a function of temperature variation and salinity. At 11.9 °N latitude, two sound channels and at 45.8°E longitude, one sound channel was observed in spring.