Climate change’s effects on ocean water temperatures and salinity could shrink sonar detection ranges underwater and make it more challenging to spot submarines.
Climate change could reduce the range of sonar detection in certain ocean regions, making it harder to hunt down submarines prowling beneath the waves.
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| The attack submarine USS Hampton is surfaced through ice on the Arctic Ocean in 2024 Specialist 1st Class Justin Yarborough/U.S. Navy |
Sonar is crucial for military efforts to track rivals’ ballistic missile submarines. These vessels can lurk in the ocean depths for months before launching a dozen or more nuclear-tipped missiles in the event of a nuclear war. Submarines can also play their more traditional role of attacking surface ships in conventional war scenarios, such as a possible Pacific conflict between the US and China.
“Our study shows that climate change will affect navies’ operations,” says Mauro Gilli at the Swiss Federal Institute of Technology in Zurich.
Gilli and his colleagues used simulations to examine sound transmission loss due to climate change in several Atlantic and Pacific deep-water regions. The researchers focused on how rising sea surface temperatures and water salinity will affect the speed and spread of sound travelling underwater, factors that determine sonar’s effectiveness at detecting sound waves emitted or reflected from objects like submarines. They compared the 30-year averages for these measures between 1970 and 1999 with an estimate for 2070-2099, based on a worst-case scenario used in Intergovernmental Panel on Climate Change assessments.
The study shows that the probability of successfully detecting submarines could significantly drop in the mid-latitudes of the eastern North Atlantic just beyond the Bay of Biscay and in the Greenland Sea, regions where both Russian and NATO submarines frequently operate. The team calculated that, at depths of 200 to 300 metres, sonar’s maximum detection range will shrink from today’s 35 to 60 kilometres, falling to 20 or fewer kilometres.
In the western Pacific, sonar detection ranges could shrink more moderately in the Sea of Japan and only decrease slightly in the Philippine Sea. But the detection range could actually improve near the surface in the Sea of Japan. This might make it easier to detect less advanced North Korean submarines, which operate only at shallow depths but still may carry nuclear-armed missiles.
“It could, on average, affect [submarine] operational deployments over the long term in the future,” says Tom Stefanick at the Brookings Institution, a think tank in Washington DC. “But any operational deployments are going to vary given the geopolitical situation and the tactical situation.”
The climate trend is just one factor among many that can affect sonar performance. Noise from busy shipping lanes and sonar countermeasures such as decoys or jammers also play a role, says Stefanick. And regardless of the long-term climate trend, short-term weather and ocean conditions also impact sonar: performance can vary greatly depending on the specific time of day or whether a given year is warmer or cooler than average, says Gilli.
Any climate impacts on sonar performance could also be offset by technological advancement, says Bryan Clark at the Hudson Institute, a think tank in Washington DC. He pointed out that China and Russia are investing in their own versions of the US Navy’s submarine detection system, which places sonar arrays on the seafloor in areas where submarines are most likely to travel.
“Those systems won’t be as affected by climate change because they’re usually in deeper water and they’re usually designed to detect submarines at a relatively short range,” says Clark. “You put the sensors where the submarine will come as opposed to trying to detect the submarine at long range.”
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