Submarines could be much harder to find as ocean temperatures rise, according to a new study.
Boat crews may change their activities and seek out warmer waters, leveraging their different acoustics to hide. In turn, that could change the way militaries hunt subs.
Submarines are strategically important for a range of missions, from coastal defense to conventional and nuclear strike options. They need to operate quietly as they sail through key areas, especially near adversaries. Similarly important is the ability to detect enemy or adversary submarines through recognition of a boat’s acoustic profile in the water.
Submarines are often located and tracked by passive and active sonar by aircraft such as maritime patrol and reconnaissance planes, surface vessels, and other submarines. Stealthier vessels with designs that notably increase hydrodynamic efficiency are harder to find and consistently track, but environment plays a role as well.
Last week, scholars Andrea Gilli and Mauro Gilli released a NATO Defense College paper on the impacts of climate change on submarine warfare. The former is a senior lecturer and NDC senior non-resident associate fellow, while the latter is a senior researcher in military technology and international security at ETH Zürich.
Their research compared historical values on water temperature and salinity from 1970 to 1999 and simulated future values for 2070 to 2099. The report’s authors concluded that “in most areas, the range at which submarines can be detected is shrinking.”
That’s particularly true, they wrote, in the North Atlantic and, to a less extent, the Western Pacific. Both of these areas were identified as having critical relevance for deterrence and defense against adversaries such as Russia, China, and North Korea. Some of these areas are experiencing faster warming than others.
The changing temperatures and salinity of the ocean affect how sound travels through the water. The change wouldn’t impact just the surface water, either, but also deeper depths, as warming spreads and melting ice decreases the salinity, or saltiness, of the water.
Off the Bay of Biscay in the North Atlantic, for example, the Gillis found that the range of detection of a submarine decreased from 60 km to 35 km. Between the first and second Island Chains in the Western Pacific, the decrease was 10 km to 7 km.
One exception, though, is in the Sea of Japan/East Sea, where North Korean submarines might operate. The range of detection could increase in this area from 10 km to 45 km “due to a mix of variation in water salinity and temperature, as well as currents.”
The study says that if submarines become harder to detect, then detection methods will need to evolve. It’s also, the authors said, one aspect of the larger adaptation to the realities of global climate change, and how environmental changes may render traditional military tactics, doctrines, and technologies obsolete.
“Under some circumstances, detecting submarines will become more difficult,” the authors said. “Whereas this change is going to be an advantage for NATO submarine forces, it is also going to be a challenge for NATO anti-submarine forces, which will require more and different resources to deal with current and potential future adversaries.”
The topic hasn’t been widely discussed, but other studies have raised similar concerns.
In 2023, Rhys Kissell, a system engineer at the defense engineering firm ADROITA, concluded that it might be harder to detect submarines when a thermal layer is present. But if it isn’t, they may be easier to find because sound could travel further. This could matter more in open ocean versus coastal waters and other shallow areas, where hiding could be easier.
And last year, the Gillis and a few other experts reported that the acoustic detection of submarines would be significantly more difficult in the mid-latitudes of the North Atlantic and moderately so in the high latitudes as climate change continues to affect water temperatures and salinity.
US and European militaries have been taking steps to counter more active Russian submarines across the Atlantic, Arctic, Baltic, and other bodies of water for years now. That’s raised questions on how to improve capabilities to detect these vessels — and remain hidden in those areas as well.
China, too, has been stepping up its submarine game. After decades of struggling to field a formidable submarine force, its boats are showing signs of being quieter and more capable. That’s also part of China’s wider naval forces buildup, which includes pumping out warships and military vessels at rates that have alarmed the US and its allies.
North Korea maintains one of the world’s largest submarine fleets. There are questions surrounding their operability given the age of the vessels, but North Korea has prioritized rebuilding their submarines and capabilities.
Research like the new NDC report puts emphasis on climate-change considerations. The new US Department of Defense leadership has, however, dismissed these types of concerns. In a recent tweet, Pentagon chief Pete Hegseth said “the @DeptofDefense does not do climate change crap.”
And within the Defense Department, there have been efforts to purge climate change efforts, which Hegseth says are “not a good use of taxpayer dollars.” There are some exceptions, but these efforts clearly are no longer a priority for the department the way they were in the past.
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