Navy ‘worried’ global warming may affect sonar

‘Sound travels faster through cold water and slower through warmer water.’

The media release is below.

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The future of sonar in semiheated oceans
Naval researchers are studying the effect of climate change on underwater sound propagation and sonar

ACOUSTICAL SOCIETY OF AMERICA

WASHINGTON, D.C., May 25, 2016 – Scientists are studying how climate change will affect the speed of sound under water to help prepare the U.S. Navy for operating in progressively warmer oceans.

Light doesn’t travel very far underwater so the navy uses sound to transmit messages. The speed of underwater sound depends on a combination of temperature, salinity and pressure. It’s a complicated equation, but temperature is the biggest factor, says Glen Gawarkiewicz, an oceanographer at Woods Hole Oceanographic Institution in Massachusetts.

Understanding sound speed is crucial for transmitting messages, detecting enemy submarines and avoiding marine animals. As climate change elevates temperatures, understanding underwater sound speed will become increasingly important.

“[We] haven’t had to deal with this issue of climate change until the last 15 years, but the temperature changes are significant enough that it really is having an impact on how sound travels in the ocean,” Gawarkiewicz said. He and his colleagues will present their research on the effect of climate change on sonar this week at the 171st meeting of the Acoustical Society of America, held May 23 – 27 in Salt Lake City.

Gawarkiewicz and his team, with funding from the Office of Naval Research, use a torpedo-like autonomous underwater vehicle to study temperature’s influence on sound speed. The vehicle emits sounds that are picked up by a receiver. Sound travels faster through cold water and slower through warmer water. By measuring the exact speed of different temperatures, scientists can help create better communication and detection tools.

This is important because enemy submarines have become more challenging to detect. In the 1980s, Japan sold Russia computerized machines that could make much quieter propellers, which means their submarines are difficult to detect. As technology has improved even more over the past 30 years, it’s become even more difficult to discover underwater craft. Climate change will only make detection more challenging.

“It’s getting harder and harder to detect these subs, and the ocean is getting noisier and noisier with commercial shipping,” Gawarkiewicz said.

“You have snappy shrimp making noise and fish making noise, and you might be hearing oil platforms,” he added. “It’s a huge challenge to try and detect underwater sources.”

Experts use underwater sound research to locate missing planes. The black boxes on airplanes have signals on them that send out bursts of sound. If the water is significantly warmer or cooler than normal, this could throw off any hope of finding the plane wreckage and figuring out what happened.

Sound speed is also important for the health of wildlife. Major shipping routes and oil platform construction often take wildlife into consideration. By mapping the speed of sound, scientists can prevent harmful noises from traveling far enough to mess up an animal’s migratory patterns or mating grounds.

“If you know that whales hang out in a certain area and you’re thinking of putting in an oil platform you’d want to know how close you can be without affecting the whales,” Gawarkiewicz said.

Presentation #3AUW3 “Recent oceanographic variability and warming of the continental shelf south of New England and implications for acoustic propagation and sub-bottom characterization,” by Glen Gawarkiewicz will take place on Wednesday, May 25, 2016, at 8:45 AM MDT in Salon A. The abstract can be found by searching for the presentation number here: http://acousticalsociety.org/content/spring-meeting-itinerary-planner

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12 thoughts on “Navy ‘worried’ global warming may affect sonar”

  1. Funny, but unless I am mistaken, the Navy sonar works in conditions ranging from underneath the arctic ice (North Pole) to the deep sea trenches at the equator. Now if the sonar did not work in the areas where El Nino conditions are generated, there might be something to it. Temperature compensation is a normal portion of equipment operation. If it was not known what differences temperature makes to the propagation of sound in water, then there might be something to it all. But as I recall, submarines having been using the thermoclines to hide under ever since it was discovered that differing layers of salinity / temperature bend sound waves away from the target.

    Ignorance can be cured, stupidity is a life long affliction. Sigh.

  2. This on top of the Navy worrying about a few extra mm in sea levels. Perhaps some new people in charge is called for, people with a modicum of common sense?

  3. Well this is my area of expertise have been a naval engineer for twenty years. This all looks like bunk to me. To start, the speed of sound increases in warmer water up to about 160F when it starts to decline.

    Second, they talk about technology making quieter submarines harder to detect. And yes, other underwater sounds hinder that as well. However, the speed of sound has nothing to do with any of that.

    The only time speed of sound underwater comes into play for submarine hunting is when using active sonar. The time it takes a ping to reach the sub and return is used to calculate the distance. And the warmth of the water needs to be factored in. Even still, the effect of a few degrees is on the order of less than one percent change.

    This is clearly research for propaganda’s sake.

  4. As climate alarm propaganda goes this is stupidity run amok.
    Here is the kicker, it doesn’t rate in the top hundred silliest.

  5. Was in the ASW business ’67-to-’96. Sounds like WHOI is on the take from NAVSEA. Should be ashamed of themselves – they’re better than that!

  6. So? Honestly, they’ve had subs operating all over the world dealing with all kinds of water temps….I don’t see how climate change is going to do anything to affect them. Besides, the deeper you go, the colder it gets.

  7. This is absolute bunk (to be polite). Mr. mcraig has the salient point. Generally speaking, the top 200FT is most effected by temperature variations over a large part of the temperate latitudes. Increasing pressure with depth drives the rest and is the primary parameter for wavefront curvature in the deep ocean, especially with increasing range. Littoral seas and shallow water are a whole different situation. I can’t believe the ASA is fronting this crap. To quote a well worn phrase I learned in 1968: ASW is tough, it’s tougher if you’re stupid, and it’s impossible if you’re stupid and don’t know it. Mr. wyoskeptic and I are in “violent agreement”.

  8. Really? the designers of nuclear powered submarines haven’t compensated for sonar/water temperature? This is must be directed to the really stupid CAGW zombies. I’m really surprised this problem wasn’t announced on the weather channel in prime time. The worry channel would have declared nuclear submarines unsafe with total withdrawal from all oceans the only recourse. That would have interrupted all their nightly weather disaster re-runs.

  9. I doubt that either the Russians or the Chinese Navies are concerned about climate change.

    So if the US Navy is worried about trivia like this , it either means the Russian and Chinese Navies combined don’t amount to a hill of beans, or the US Navy has become incapable of defining real threats to the nation.

    Maybe there no military threats exist that the navy must prepare for and maybe they have to pretend that climate change is a threat. Maybe that’s why they concocted this ridiculous story about sonar and climate change.

    America believed once that the Japanese navy was not a threat. I just hope they are not wrong again.

    I suspect that in November voters will cast their votes based on a more realistic world view than what the present Commander-in-Chief is now imposing upon his commanders.

  10. The Navy should first ask how atmospheric CO2, trapping IR between 13 and 18µ can possibly be warming the oceans. Once you can explain how atmospheric Co2 can warm the oceans, then you have a case, but until then, you have a real problem. Visible light warms the oceans, IR between 13 and 18µ doesn’t penetrate nor warm water, in fact it causes surface evaporation and cooling. More ironic, CO2 has absolutely no measurable impact on temperature in the first 100m of the atmosphere, absolutely none. You can verify that by using the online MODTRAN calculator at the U of Chicago. H2O is the GHG that dominates the temperature near the earth’s surface, and ironically the Navy ignores that.

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