The oceans bear the brunt of the consequences of climate change, particularly rising sea levels, temperatures, and acidification of water. A new study takes a closer look at another little-talked-about consequence: modification of the ocean’s acoustic landscape and its effects on marine animals.
In fact, the acceleration of global warming is no longer a secret to anyone… The latest report of the Intergovernmental Panel on Climate Change (IPCC) sends chills down the spine and it appears that limiting global warming to approximately 1.5°C as the temperature rises, during The twenty-first century is difficult to achieve. Remember that current emissions policies and commitments put the world on a trajectory of about 2.3 to 2.7 degrees Celsius warming.
All of this has direct consequences, sometimes visible or invisible to the naked eye, for oceans, which have to deal with fundamental changes affecting ecosystems and marine life. However, we must not forget that the oceans are important carbon sinks, they produce a large part of the oxygen we need to live and have an essential role in regulating the climate.
According to a new global study published in Earth’s Future (AGU Journal of Interdisciplinary Research on the Past, Present and Future of Our Planet and Its Population), climate change, especially global warming, can negatively affect the speed at which sound propagates underwater. This is an environmental issue that must be taken seriously because these modifications can alter the natural sound and increase human-caused noise.
Currently, there are only a few studies, on a global scale, of the vulnerability of marine mammals to global warming, but none have focused on Underwater sound propagation changes. Therefore, it is the first estimate of the velocity of ocean sound under projected climate conditions in the future.
According to the researchers, it is important to analyze the sound of the ocean because A large part of life in the ocean depends on sound. For example, cetaceans have developed highly specialized auditory systems and need an appropriate acoustic environment to thrive. On the other hand, aquatic mammals do a lot through vocalization to show territorial dominance, forage for food, find a mate, or warn other individuals about the presence of a predator.
So the aim of this new study is to Predict future impacts of climate change on marine life In order to mitigate them and prevent them from becoming irreversible. Therefore, scientists have identified areas where differences in the speed of sound are the strongest – “acoustic hot spots” – Whereas, marine ecosystems can undergo significant changes.
Two areas of future acoustic hotspotwith the largest differences in the speed of sound, at depths of 50 and 500 meters, were observed by scientists: the eastern Greenland Sea and the northwestern Atlantic Ocean, in eastern Newfoundland.
“We calculated the effects of temperature, depth and salinity based on general data to model the acoustic landscape of the future”said Alice Avati, a bioacoustics researcher at Memorial University of Newfoundland and Labrador, St. John, Canada, and lead author of the study.
The ocean sound Corresponds to the cacophony of vibrations produced by living organisms, and natural phenomena, such as waves and ice cracks or marine movement and resource extraction.
The speed of sound at a depth of 50 meters ranges from 1450 meters per second in the polar regions to 1520 meters per second in tropical waters.
Sound is an essential tool for many animals allowing them to communicate and move. Therefore, changing the speed of sound can affect their ability to feed, fight, find mates, avoid predators, and eventually migrate.
… in complete transformation
According to the study, The average speed of sound should increase by 1.5%, That is, about 25 meters per second in surface waters and up to 500 meters deep by the end of the twenty-first century, in the “future acoustic hot spots” of the Greenland Sea and the northwest Atlantic, if high rates of greenhouse gas emissions continue until 2100.
The researchers pointed to other hot spots – attractions – o It can increase the speed of sound by 1%.or more than 15 meters per second: the Barents Sea, the Northwest Pacific and Southern Ocean, at a depth of 50 meters, or the Arctic Ocean, the Gulf of Mexico and the southern Caribbean, at a depth of 500 meters.
A significant impact is expected in the Arctic, where we already know that there is currently an amplification of the effects of climate change. Not the whole Arctic, but a specific part where all the factors play together to give an indication that the model predicts overcoming uncertainty in the model itself”said author Stefano Salon, a researcher at the National Institute of Oceanography and Geophysical Applications in Trieste, Italy.
The temperature and pressure associated with increasing depth and salinity in ocean waters directly affect the speed and distance that sound travels in the water. In warm water, sound waves travel faster And you need more time to disappear.
Effects on the North Atlantic right whale
Changing the acoustic landscape within the two future acoustic points will have a strong impact on right whales in the North Atlantic (Eubalaena glacialis).
According to the Red List, in 2020, the North Atlantic right whale is listed as endangered. Between 2011 and 2020, its population declined due to higher mortality rates (mostly due to entanglement in fishing gear or collisions with ships) but also lower reproductive rates than the average of previous years.
The study modeled the sounds of right whales in warmer surroundings and were more likely to travel further. “We choose to talk about one type of megafauna, but many trophic levels in the ocean are influenced by acoustic landscape or use sound”Avati said. “All these hotspots are places with great biodiversity. “
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