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Underwater sonar transmissions will travel longer distances as the oceans undergo temperature change and bring implications for submarine warfare, according to a recent study published by Sydney defence consultancy ADROITA.
The pilot study into how climate change will affect the transmission of sound in the ocean over the next 80 years concluded that the oceans of tomorrow will be much noisier than they are today, with soundwaves travelling up to 87 per cent further in some cases, according to information collected by ADROITA systems engineer Rhys Kissell.
The information was privately conducted with temperature predictions from the Intergovernmental Panel on Climate Change with data from the United States’ National Oceanic Atmospheric Administration.
That data was, in turn, drawn from the 3,000-strong fleet of ocean-going Argo data-collection robots tracking changes and being fed into a custom-built simulator to simulate the effect of higher temperatures, decreased salinity, and greater acidity on sound propagation and attenuation.
“My research found that ultrasonic sonar transmissions in the 30 kilohertz range will propagate between 40 to 87 per cent further than they do today, while mid-frequency sonar transmissions in the 10 kilohertz range will propagate between 15 to 25 per cent further,” Kissell said.
“This will have a pronounced impact on technology that relies on hydroacoustics such as active and passive sonar, hydrophones, echo sounders, fish finders, and sub-seafloor profiling devices.
But the most significant consequence will be for the underwater stealth technologies that are essential for military operations. It will be a lot harder for them to remain undetected.
“The year 2100 may seem a long way off, and yet the time involved in taking a submarine from the concept stage to transition into service, and the extended service life that many of today’s classes of submarines are experiencing, means that the marine engineers who are designing submarines need to begin taking these things into account today.”
The research indicated that effects would differ based on oceanic characteristics: low-latitude oceans will undergo a substantial acoustic transformation compared to the present, while polar oceans will experience a more extreme transformation.
The study also indicated that while the ocean environment will be louder and underwater platforms like submarines will become more detectable, there will also be greater opportunities for platforms to hide among the ocean noise.
There will be a need for better sensors and processors that can be upgraded over time to enhance their processing power to give them greater ability to filter out ambient noise.
The paper calls for further research into the effects of climate change on hydroacoustics to guide the technological and policy response from government, and the ADF especially. It also contributes to the relatively small existing body of literature by providing a multifaceted view of anticipated changes in oceanic hydroacoustics due to climate change.
Kissell aims to address the literature gap with this pilot study and acknowledges its limitations due to a small sample size and simulator constraints.
Robert Dougherty
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