• Warming oceans are getting louder

    From ScienceDaily@1:317/3 to All on Thu Mar 24 22:30:46 2022
    Warming oceans are getting louder

    Date:
    March 24, 2022
    Source:
    American Geophysical Union
    Summary:
    Climate change is speeding sound transmission in the oceans and
    the way it varies over the globe with physical properties of the
    oceans. Two 'acoustic hotspots' of future sound speed increases are
    predicted east of Greenland and in the Northwest Atlantic Ocean,
    East of Newfoundland. In these locations, the average speed of
    sound is likely to increase by more than 1.5% if 'business-as-usual'
    high rates of greenhouse gas emissions continue through 2100.



    FULL STORY ========================================================================== Climate change will significantly alter how sound travels underwater, potentially affecting natural soundscapes as well as accentuating human- generated noise, according to a new global study that identified future
    ocean "acoustic hotspots." These changes to ocean soundscapes could
    impact essential activities of marine life.


    ==========================================================================
    In warmer water, sound waves propagate faster and last longer before
    dying away.

    "We calculated the effects of temperature, depth and salinity based
    on public data to model the soundscape of the future," said Alice
    Affatati, an bioacoustics researcher at the Memorial University of
    Newfoundland and Labrador in St. John's, Canada, and lead author of
    the new study, published today in Earth's Future, AGU's journal for interdisciplinary research on the past, present and future of our planet
    and its inhabitants. It is the first global- scale estimate of ocean
    sound speed linked to future climate.

    Two hotspots, in the Greenland Sea and a patch of the northwestern
    Atlantic Ocean east of Newfoundland, can expect the most change at 50
    and 500 meter depths, the new study projected. The average speed of sound
    is likely to increase by more than 1.5%, or approximately 25 meters per
    second (55 miles per hour) in these waters from the surface to depths
    of 500 meters (1,640 feet), by the end of the century, given continued
    high greenhouse gas emissions (RCP8.5).

    "The major impact is expected in the Arctic, where we know already there
    is amplification of the effects of climate change now. Not all the Arctic,
    but one specific part where all factors play together to give a signal
    that, according to the model predictions, overcomes the uncertainty of
    the model itself," said author Stefano Salon, a researcher at the National Institute of Oceanography and Applied Geophysics in Trieste, Italy.

    The ocean soundscape is a cacophony of vibrations produced by living
    organisms, natural phenomena like waves and cracking ice, and ship
    traffic and resource extraction. Sound speed at 50 meters depth ranges
    from 1,450 meters per second in the polar regions to 1,520 meters per
    second in equatorial waters (3,243 to 3,400 miles per hour, respectively).



    ==========================================================================
    Many marine animals use sound to communicate with each other and navigate
    their underwater world. Changing the sound speed can impact their ability
    to feed, fight, find mates, avoid predators and migrate, the authors said.

    Changing soundscapes In addition to the notable hotpots around Greenland
    and in the northwestern Atlantic Ocean, the new study found a 1% sound
    speed increase, more than 15 meters per second, at 50 m in the Barents
    Sea, northwestern Pacific, and in the Southern Ocean (between 0 and
    70E), and at 500 m in the Arctic Ocean, Gulf of Mexico, and southern
    Caribbean Sea.

    Temperature, pressure with increasing depth and salinity all affect how
    fast and how far sound travels in water. In the new study, the researchers focused on hotspots where the climate signal stood out clearly from the
    model uncertainty and was larger than seasonal variability.

    The new study also modeled common vocalizations, under the projected
    future conditions, of the North Atlantic right whale, a critically
    endangered species inhabiting both north Atlantic acoustic hotspots. The whales' typical "upcall" at 50 Hertz is likely to propagate farther in
    a warmer future ocean, the researchers found.

    "We chose to talk about one megafauna species, but many trophic levels
    in the ocean are affected by the soundscape or use sound," Affatati
    said. "All these hotspots are locations of great biodiversity." Future
    work will combine the global soundscape with other maps of anthropogenic impacts in the oceans to pinpoint areas of combined stressors, or direct
    needed observational research.

    "With complicated problems like climate change, to combine different
    approaches is the way to go," said author Chiara Scaini, an environmental engineer at the National Institute of Oceanography and Applied Geophysics.


    ========================================================================== Story Source: Materials provided by American_Geophysical_Union. Note:
    Content may be edited for style and length.


    ========================================================================== Journal Reference:
    1. Alice Affatati, Chiara Scaini, Stefano Salon. Ocean Sound
    Propagation in
    a Changing Climate: Global Sound Speed Changes and Identification
    of Acoustic Hotspots. Earth's Future, 22 March 2022 DOI: 10.1029/
    2021EF002099 ==========================================================================

    Link to news story: https://www.sciencedaily.com/releases/2022/03/220324130319.htm

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