February 24, 2021 — Unlike light, noise is a long distance traveler and can go astonishing distances through the water. In 1943, the sound fixing and ranging (SOFAR) channel, a horizontal layer of water in the ocean at which depth the speed of sound is at its minimum, was discovered. The SOFAR channel was capable of transmitting low-frequency, long-wavelength sound waves produced by an explosion near the Bahama Islands to receivers stationed near the coast of Africa. Sound waves in the narrow SOFAR channel that are traveling at minimum velocity can go as far as 15,000 miles or more. Unfortunately for those that live in the ocean, this means their world has become loud – very loud.
On February 5, 2021, Duarte et al., published “Noise Pollution: The soundscape of the Anthropocene ocean” in the journal Science. A soundscape is an acoustic environment and a wide variety of noises make up the soundscape under the world’s oceans. Weather conditions, like storms, wind or rain falling, and geological processes, such as earthquakes or undersea volcanoes, are geophony; the natural sounds that animals and organisms make, such as vocalizations, calls, trills, fins flapping, etc., are biophony. And then there are humans – the sounds we and our human activities contribute to the soundscape are called anthrophony.
One of the most widely recognized incidents representative of the impact of human sound on marine life is the March 2000 stranding of seventeen marine mammals (16 of them whales) in the Bahamas. The animals had beached themselves in and around the islands, some with bleeding ears; six of them were dead. After learning that this had occurred very shortly after US Navy destroyers were using sonar in training exercises nearby, government scientists launched an investigation. An interim report released in December 2001 concluded that the strandings were caused by several factors, but admitted the sonar pings likely dazed the mammals, causing confusion and disorientation.