Acoustic propagation analysis in the front of saline water mass in the Gulf of Aden

Influence of water mass on sound propagation in the Gulf of Aden underwater acoustics used for communication, navigation and identification of objects by both humans and marine mammals and for investigating the detrimental effects of anthropogenic activities (e.g. pile driving, seismic survey and ships) on marine animals. The Gulf of Aden presents a unique ecosystem that deserves scientific attention. In addition to its extraordinary biotic richness, the Gulf of Aden also serves as a highway for international trade between east and west. The Gulf of Aden is an important Gulf connecting Red sea water with the Indian Ocean. Red Sea Water is the most prominent water mass in the Gulf of Aden and there is no ambiguity about its origin. It outflows into the Gulf of Aden from the Red Sea through Bab-el-Mandab strait. Sound speed in the oceans depends on temperature, salinity, and pressure and has large seasonal and spatial variations.

This paper studies patterns and seasonal variations of propagation sound in the presence of the Red sea water mass by using a coupled ocean model (MITgcm) and an acoustic model (ray method). For this purpose, first using the results of Shafiei et al. (1397), temperature and salinity output were extracted and then using the Mackenzie equation, the speed of sound was calculated.

By examining the sound speed profile horizontally and vertically, the intrusion flow of the Red Sea water to the Gulf of Aden was observed at depths of 300 to 800 meters Also in winter, the outflow area of the Red Sea is larger than in summer. Then, the influence of this strong intrusion on sound propagation are comprehensively analyzed with the parabolic equation and explained by using the ray theory. Using the ray theory, in the presence of infiltration flow of Red Sea water to the Gulf of Aden in different scenarios, including in the direction perpendicular to this flow, parallel to the movement of this flow and different depths of the sound source, how sound propagation from this phenomenon in these seasons Analyzed.

Propagation sound was studied in 2D and 3D, the results show that displacement the sound source across intrusion flow can change the propagation paths and cause the convergence zone to broaden and approach the sound source. In addition, the results of two-dimensional and three-dimensional simulations showed that the presence of these masses caused changes in the distribution of acoustic energy in both seasons. Overall, the results show that intrusion flow can change the propagation paths and cause the convergence zone to broaden and approach the sound source.