Answer: Density
Step-by-step explanation:
Actually those three things are really just one thing. Density.
Temperature affects density.
Salinity affects density.
Density affects the speed of sound through water.
Alterations to the speed of sound through water alter the path of soundwaves propagating through the water.
Sooo…
With increasing depth, comes decreasing temps as water gets colder the deeper you go. Cold water is denser than warm. Sound waves angled down into the depths eventually become curved back towards the surface.
This creates a rather interesting effect. While a sonar could normally detect a target at a certain range or less, these “Convergence Zones” where sonar waves are reflected back to the surface create annular rings of detection beyond the normal detection range.
This bending of soundwaves can also create “dead zone” where the soud waves just do not reach from a particular location. creating sound shadows where the sonar does not see.
In many locations in deep water, there can be a sudden shift in the rate of temperature change, usually located between the upper part of the ocean where temps can vary with seasons and the lower Isothermic layer where the temps change very little. This creates a layer called the thermocline Sonar detection across the layer Where the sonar and target lay on opposite sides, above and below the layer…is reduced compared to sonar detection where both sonar and target are on the same side of a layer.
So the temperature of water, which varies widely with depth, can cause the ray path of soundwaves to bend and reflect and even converge, creating both increased areas of detection as well as blind zones of reduced detection.
Salinity also affects density, With salt water being denser than Freshwater.
So areas wher there is a high degree of turbidity and mixing of these two types of water, like near the mouth of a large volume discharge of water, can create very unpredictable sound channels that are constantly changing. this make sonar performance prediction very difficult and affects the Sonar’s ability to detect targets.