‘Underwater tornadoes’ found near China’s nuclear submarine base by Paracels that could sink U-boats in treacherous abyss
Phenomena known as deep eddies not visible from surface but seen as potential threat to military activity, oil and gas exploration in the waters south of Hainan Island
Chinese scientists have discovered a series of potential “deathtraps” near the Paracel Islands, called the Xisha Islands by China, in the South China Sea where a submarine could plunge into swirling waters and be crushed by the pressure at such a deadly depth.
The archipelago of 130 islands, which are controlled by China but also claimed by Taiwan and Vietnam, are located close to China’s nuclear submarine base. Called Yulin Naval Base, it lies long the south coast of Hainan Island, a popular escape for Chinese tourists.
The phenomena in question are known as deep eddies, or rare occurrences created by deep water blowing across the sea floor, almost like a tornado in slow motion or a watery black hole.
They are not visible from the surface as they stop just short of this, meaning there are no visible waves or ripples to be observed by a ship or satellite, making them even more dangerous. They can have their roots thousands of metres below sea level.
The research team, led by Professor Wang Dongxiao with the Chinese Academy of Sciences’ South China Sea Institute of Oceanology in Guangzhou, recorded numerous deep eddy events in the Xisha Trough, an abyss between the Paracels and Hainan.
The vortexes, each more than 100 metres wide, carried such a tremendous amount of energy that they were altering the landscape of the entire sea floor in the region with their irregular but frequent occurrences, according to their paper published recently in the journal Scientific Reports.
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Currents in the vortex can flow eight times faster than regular currents, according to data collected by a pair of mooring buoys placed by the Chinese government in the region.
“These cases indicate that the Xisha Trough is an area where deep eddies are generated, and these can either dissipate locally or propagate in different directions,” the authors wrote in the paper.
“This is an important discovery,” said Dr Ma Chao, a researcher at the Key Laboratory of Physical Oceanography at the Ocean University of China, who was not involved in the study.
“Deep eddies are like ghosts that have haunted marine scientists for decades. Very, very few records are available because they are extremely difficult to observe.”
“But studying the phenomenon is important, partly because these can be a driving force behind internal waves,” Ma added.
Internal waves propagate in water without leaving any trace on the surface. These invisible ripples can cause submarines to suddenly plunge hundreds of metres in just a few minutes beyond their control.
Unlike an aircraft, which can climb back to the proper altitude after it encounters turbulence, modern-day U-boats usually can’t descend beyond 500 metres due to the enormous water pressure at such depths.
This phenomenon is suspected to have caused several major submarine accidents, including the loss of the USS Thresher off the coast of Boston in 1969. The nuclear-powered attack submarine took with it all 129 crew members. It remains the worst submarine disaster on record.
The new discovery may also help explain an incident encountered by the Chinese Navy during a recent military drill in the region that resulted in a miraculous escape.
According to a report by the People’s Daily last year, a new diesel-powered submarine referred to as “No 372” that belonged to China’s South Sea Fleet ran into an internal wave when disaster struck.
“It was like a fast car suddenly running over a cliff. We felt helpless and hopeless,” the report quoted captain Yi Hui as saying. Yi added that he had never encountered the phenomenon in his 22 years of service.
As the sub descended, the increasing water pressure caused a number of equipment failures including the bursting of a key pipe. This led to flooding that threatened to render useless the engine room.
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After three minutes of desperate effort, which included the sealing of all flooded chambers (even though there were still crewmen trapped inside), the submarine was able to ascend again. This may have been partly luck, and also partly due to quick-response contingency measures like pumping gas into the water tanks to increase the boat’s buoyancy.
China’s Navy has declined to reveal the exact time or location of the incident for reasons of national security, but it is believed to have occurred somewhere in the Xisha Trough.
This is also politically sensitive area. The Paracels are rich in fossil fuel reserves. Last year, China and Vietnam were engaged in a tense stand-off after China sent its largest drilling platform into the area.
The researchers of the latest study urged the government and oil and gas companies to consider the risk posed by deep eddies before conducting future exploration activities in the region.
The rapid movement of deep seawater could have a “very big impact” on cables and pipelines on the sea floor, they said.
