What Is An 'Internal Wave'? It Might Explain The Loss Of An Indonesian Submarine

[Michie]

An image taken by NASA's Aqua satellite as it passes over Indonesia, captures evidence of an internal wave in the same general area where the KRI Nanggala submarine disappeared earlier this month.


No official cause has yet been established for the destruction of an Indonesian submarine with 53 people aboard earlier this month, but some speculation has zeroed in on an undersea phenomenon which has been noted by submariners since at least World War II, though 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 the KRI Nanggala 402 below its crush depth, causing the loss of the vessel and all aboard. He cited satellite images showing the presence of such a wave in the area at about the time the sub disappeared.


Such waves — while seldom noticed by observers on the surface — can reach dizzying undersea heights and therefore cause concern for submarines, scientists say. They are generated by the interplay of strong tides, warmer and cooler ocean layers and the undersea geography.

Internal waves occur in specific ocean regions around the world – places such as the Strait of Gibraltar that links the Mediterranean with the Atlantic Ocean, parts of the Western Pacific and the South China Sea. They are also known to exist in the Lombok Strait area in Indonesia, where the Nanggala was lost.

Continued below.
What Is An 'Internal Wave'? It Might Explain The Loss Of An Indonesian Submarine

 

[Bob Crowley]

I lifted this paragraph off a rather old US Navy publication dated in 1966.

https://apps.dtic.mil/dtic/tr/fulltext/u2/632010.pdf

B. ... NONACOUSTIC EFFECTS Internal waves have a negligible effect on the operation of buoys, torpedoes, mines, and submarines, with the following exceptions: (1) A submarine, hovering during a power failure, may suddenly find itself in a region where it is appreciably negatively buoyant during the passage of a large-amplitude internal wave. In this situation, the submarine might sink rapidly for tens of meters....

As I said the article is dated, but I wonder if the elderly Indonesian submarine had a power failure at about the same time? One would have thought it could pull itself out of trouble using its power, unless the internal wave caused it to slam into rocks or some other object before they could adjust.

Just conjecture. It was a tragic event, but I suppose that's the submarine service. As a rule, you come back either whole or not at all.

 

[DerSchweik]

Ex-submariner. Never heard of such a phenomenon before. The usual suspects would be an uncontrollable leak (flooding - e.g. USS Thresher), water in the boat's battery / battery explosion, collision with something underwater (another submarine, underwater mountain, etc.), loss of power while negatively bouyant / inability to blow ballast tanks), jammed planes at high speed while at depth (typically addressed by procedure - speed reduction the deeper you go), torpedo issues, fire... any number of things really.