into nature Shout out loud and only nearby birds, frogs and squirrels will hear you. Although perceiving noise is a key survival strategy for land animals, it is a limited warning system because sound—except for things like massive volcanic eruptions—don’t travel very far in the air. They travel better in water, where seafloor noise travels hundreds or even thousands of miles depending on conditions.

These conditions are changing rapidly as the oceans warm. Changes in salinity, temperature and pressure alter the sound of the ocean, with unknown effects on life forms that depend on this noise to survive. Whales talk to each other and navigate and use the tones of the earth by listening to the waves on the shoreline. Dolphins use sounds to echolocate their prey. Coral-dwelling fish are born in the open ocean and then use the noise of bustling reefs to find their homes. Joining the sound of life is the sound of the Earth system: winds swept across the sea, requiring extra shock during storms. Earthquakes and submarine landslides rumbled across the ocean. The resulting tsunami accelerates along the sea’s surface, creating a racket that marine animals are very accustomed to.

This is a key and understudied aspect of how rising temperatures and increased noise activities such as shipping may affect marine ecology. “Natural soundscapes have really come to the forefront of people’s thinking in the last 10 or 15 years,” says Ben Halpern, a marine ecologist at the University of California, Santa Barbara, who studies stress in marine ecosystems. For example, scientists are now better understanding forest biodiversity by listening to life that may be hidden from the human eye—insects, birds, amphibians. “It’s only recently that people have begun to appreciate the role of soundscapes in the ocean, telling us what’s going on underwater as human influence expands,” Halpern added.

Since sound travels faster and farther in water than in air, the “neighborhood” in the ocean is larger. (Birds can communicate hundreds of feet, but for whales it’s hundreds of miles.) How sound travels in the area depends on the temperature, pressure and salinity of the water. This is because sound itself is a pressure wave that compresses and decompresses molecules in the water. When the water warms, the molecules vibrate faster, allowing the sound waves to travel faster. The deeper you go, the higher the pressure. For example, salinity also changes if you are near a glacier that feeds fresh water into the sea.

This creates a layering: temperature, salinity, and pressure combine in different ways, affecting how sound travels. “Think of salad dressing as oil and vinegar before you shake it, but the ocean is made up of different salinities,” said Alice Afatati, a bioacoustics researcher at Memorial University of Newfoundland and Italy’s National Institute for Oceanography and Applied Geophysics. layers and different temperatures.” . Because the layers are different, the sound can bounce off of them. “So if you think of a whale as a source of sound waves, it matters where the whale is. If it’s in a deeper or shallower layer, even the same sound it’s producing will change the propagation,” she said.

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Affatati and her colleague Chiara Scaini, also at the National Institute of Oceanography and Applied Geophysics, published a study last month on how changing oceans may affect the soundscape of a specific species of North Atlantic right whale. They used a wealth of data on these variables — temperature, pressure and salinity — to identify two hotspots of change, one in an area of ​​the Greenland Sea and the other near Newfoundland. Here, the average speed of underwater sound could jump by more than 1.5 percent by 2100. This would allow whale calls to travel farther, with unknown effects on how the species communicate.

The two researchers hope that other scientists will use the same framework to study the changing soundscapes of other marine life. “It provides a starting point for other studies that can investigate, for example, how different species respond to the same changes,” says Scarney. “The impact of this on marine life is unknown because there are so many variables involved. So it’s not a simple problem that we can model.”

Still, it’s no accident that Scaini and Affatati see the Greenland Sea as a place of change. The Arctic is warming four times faster than the rest of the planet, in large part because as ice melts, it exposes deeper seawater that absorbs more solar energy. According to a 2016 paper, the Pacific Ocean also feeds a shallow “acoustic pipe” of warm water to the North Pole, which has been enhancing and dramatically changing the soundscape. In other words: the Pacific is essentially injecting sound into the Arctic marine ecosystem.