Jeff Schmalz /, MODIS Rapid Response Team, NASA GSFC
No official reason has yet been established for the destruction of an Indonesian submarine with 53 people on board earlier this month, but some speculation has focused on an underwater phenomenon noted by submarines since at least World War II, although it has become better understood. only in recent decades.
A senior Indonesian navy official suggested earlier this week that an “internal wave” may have pushed KRI Nanggala 402 below the depth of the crash, causing the loss of the ship and everyone on board. He cites satellite images showing the presence of such a wave in the area at the time the sub disappeared.
Such waves – although rarely seen by observers on the surface – can reach dizzying underwater heights and therefore cause concern for submarines, scientists say. They are generated by the interaction of strong tides, warmer and cooler ocean layers and underwater geography.
Inland waves occur in certain oceanic regions of the world – places such as the Strait of Gibraltar, which connects the Mediterranean Sea with the Atlantic Ocean, parts of the Western Pacific and the South China Sea. They are also known to exist in the Lombok Strait region of Indonesia, where Nanggala is lost.
Matthew Alford, assistant director of the Marine Physics Laboratory at the Scripps Institute of Oceanography in San Diego, says the United States, China and Russia have “spent a lot of money” studying inland waves in the South China Sea because of their potential impact on naval operations. the strategic waterway.
“[I]The internal waves are very strong and dangerous because they engulf the ocean (and potentially everything in them, including divers or submarines) down hundreds of meters in just a few minutes, “Alford said in an email to NPR.
“The Lombok Strait is also a known region of strong internal waves,” said Alford, who is studying the phenomenon.
Although he has never heard of an internal wave sinking a submarine, this is a “plausible” scenario, Alford said.
Indonesian Navy / AP
A 1966 U.S. Navy study notes that “the passage of high-amplitude internal waves can make it difficult to control the submarine’s depth, especially when the submarine is operating quietly at low speeds.” The report entitled Internal waves: Their impact on naval operations, added that such waves “could initiate an uncontrolled sinking of a submarine”.
During World War II, submarines avoided the Strait of Gibraltar in part because they were aware of its reputation for propagating unusual underwater waves that are considered dangerous, David Farmer, a physical oceanographer at the University of Rhode Island, told USA Today in 2014.
At the height of the Cold War in 1984, a Soviet submarine, apparently operating under a tanker to mask its exit from the Strait, suddenly crashed into the hull of the tanker, causing damage to both ships and forcing the submarine to float. The collision is believed to have been caused by an internal wave that unexpectedly pushed the submarine to the surface.
Maarten Buisman, a marine scientist at the University of Southern Mississippi, agrees that an internal wave may have caused Nanggala’s sinking. “Some internal waves can have large amplitudes and displace submarines,” he said.
The waves “are generated by a steep topography due to surface tides,” he told NPR. “In the South China Sea, the amplitudes of internal waves can be about 100 meters (330 feet).”
In the case of Nanggala, what happened may be the exact opposite of what happened to the Soviet submarine in the Strait of Gibraltar in the 1980s – instead of an internal wave pushing the submarine to the surface, the Indonesian ship may have been pushed much deeper. than is designed for safe operation.
Nanggala’s death is still under investigation. According to Indonesian Admiral Judo Margono, the ship was located at least three pieces on the ocean floor at a depth of nearly 840 meters (2750 feet) – far deeper than the “collapse depth” of the submarine of 200 meters (655 feet).
The internal wave is just one of the possible explanations for the destruction of the diesel submarine built in Germany. Although it underwent repairs in South Korea, which was completed in 2012, it is an old boat – entered service by the Indonesian Navy in the early 80’s.
It is also reported that Nanggala was preparing for a torpedo exercise at the time the radio link was lost – and torpedo accidents have been the cause of some submarine losses in the past. In August 2000, a torpedo explosion in a tube aboard the Russian submarine Kursk released the remaining torpedoes, as a result of which the submarine landed in the Barents Sea, along with all 118 of its crew, according to an official investigation.
Decades earlier, in 1968, the nuclear USS Scorpion was lost with its 99 crews. The cause of the Scorpion’s sinking has never been conclusively proven, but one theory suggests that the submarine succumbed to a “hot” torpedo that unexpectedly activated while still in its tube.
During a media briefing in Jakarta earlier this week, counter-administrator Ivan Isnurvanto, the former submariner himself, painted a grim picture of KRI Nanggala’s final moments.
If it was an inner wave, he said, “that would be the nature we face.”
“We would be dragged by the waves, sending us downhill,” he said, adding, “No one can fight nature.”