Ocean warming makes water ‘stronger’, impacting marine life
According to a new global study that has identified future “acoustic hotspots” in the oceans, climate change will dramatically alter the way sound travels underwater, potentially affecting natural soundscapes and amplifying human-generated noise. .
These changes to ocean soundscapes could impact the essential activities of marine life.
(Photo: Peter Brown/Pexels)
Sound waves travel faster and persist longer in warmer water before dissipating.
They used public data to model the future soundscape, according to Alice Affatati, a bioacoustics researcher at Memorial University of Newfoundland and Labrador in St. John’s, Canada, and lead author of the new study, which was published today in Earth’s Future.
The new study predicted that at depths of 50 and 500 meters, two hotspots in the Greenland Sea and part of the North Atlantic Ocean east of Newfoundland would experience the greatest weathering.
Given ongoing high greenhouse gas emissions, the average speed of sound in these seas, from the surface to depths of 500 meters (1,640 feet), is expected to increase by more than 1.5%, or approximately 25 meters per second (55 miles per hour), by the end of the century (RCP8.5).
“The major impact is expected in the Arctic, where we already know that there is now an amplification of the effects of climate change,” said author Stefano Salon, a researcher at the National Institute of Oceanography and applied geophysics from Trieste, Italy.
“Not the whole of the Arctic, but a specific part where all the factors play together to signal that, according to the model’s predictions, overcomes the uncertainty of the model itself,” Salon said.
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music in the ocean
(Photo: Photo by Alexis Rosenfeld/Getty Images)
The soundscape of the ocean is a cacophony of vibrations caused by living species, natural events such as waves and the cracking of ice, maritime traffic and the exploitation of resources. At 50 meters depth, sound speeds range from 1,450 meters per second in polar seas to 1,520 meters per second in tropical waters (3,243 to 3,400 miles per hour, respectively).
Many aquatic species communicate with each other and navigate their underwater environment through sound. Scientists said altering the speed of sound can affect their ability to feed, fight, locate mates, escape predators and move around.
Along with the well-known hotspots around Greenland and in the northwest Atlantic Ocean, the new research found a 1% increase in the speed of sound, or more than 15 meters per second, at 50 meters in the Barents Sea, the Pacific Northwest and the Southern Ocean. (between 0 and 70E), and 500 meters in the Arctic Ocean, the Gulf of Mexico and the southern Caribbean Sea.
Sound traveling in water
The speed and distance traveled by sound in water is affected by temperature, pressure as depth increases, and salinity. The current study focused on hotspots where the climate signal was more important than seasonal fluctuations and clearly demarcated from model uncertainty.
The current study also replicated the frequent vocalizations of the North Atlantic right whale, a critically endangered species that lives in the two North Atlantic acoustic hotspots, under projected future conditions. The researchers found that the whales’ regular “recall” at 50 Hertz would likely spread farther into a warmer future ocean.
They chose to focus on one species of megafauna, although the soundscape affects or is used by many trophic levels in the ocean, Affatati explained. All these hotspots are rich in biodiversity.
The overall soundscape will be merged with other maps of anthropogenic impacts in waters in the future to indicate locations of coupled stresses or to guide essential observational study.
“Combining multiple methodologies is the way to deal with difficult problems like climate change,” said author Chiara Scaini, an environmental engineer at the National Institute of Oceanography and Applied Geophysics.
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