How does the SOFAR channel allow sound to travel long distances through the ocean?

The SOFAR channel (Sound Fixing and Ranging channel) is a layer in the ocean, typically found at a depth of approximately 1,000 meters, where the speed of sound reaches a minimum value.12

In this region, the combination of temperature, salinity, and pressure creates a unique environment that traps sound waves through refraction. When a sound is generated within this zone, the sound waves are continuously bent back toward the channel's center whenever they attempt to move into layers where the speed of sound is higher.12

Because the sound is trapped and dispersed horizontally rather than spreading in three dimensions, the energy is conserved, allowing the signal to travel over vast distances with minimal loss. This phenomenon enables hydrophones located many kilometers away to detect the sound pulse, which can then be used to triangulate the source of the signal.12