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Research helps shed light on the mystery of internal waves

UniSQ research is doing a deep dive into the power of a formidable force lurking beneath the surface

There is a hidden power lurking under the surface of the ocean, which has enough force to damage structures and sink submarines.

While this sounds like something from the pages of 20,000 Leagues Under the Sea, it’s instead caused by a common phenomenon – waves.

University of Southern Queensland Professor of Applied Mathematics Yury Stepanyants has been studying internal waves, which can occur at hundreds of meters below the sea surface.

Invisible from above, internal waves can reach amplitudes of more than 150 metres.

“These waves are often generated by tides or currents passing over an underwater obstacle, such as sills or mountains. They can also be caused by underwater landslides, volcanic eruptions, and variations of atmospheric pressure,” Professor Stepanyants said.

“They can propagate across the whole ocean, but their appearance depends on a geographical zone – in some places internal waves appear fairly regularly, approximately twice a day.

“It’s important to study them because they have big amplitudes and can move long distances with speeds of up to three metres per second, which can have substantial impacts on submarine navigation, coastal engineering constructions and the marine ecosystem.”

In his recent paper, Professor Stepanyants explored the possibility that internal waves caused the past wreckage of both American and Indonesian submarines.

In April 2021, the Indonesian diesel submarine KRI Nanggala 420 sank in the Bali Sea, killing all 53 crew members on board.

It is suspected internal waves played a crucial role in the tragic event.

“Internal solitary waves in the deep sea usually have a form of trough in contrast to surface waves, which form as humps in shallow basins,” Professor Stepanyants said.

“These troughs can change the buoyancy of a submarine, causing it to sink to a dangerous depth.

“Submarines usually operate in the upper ocean, up to 350 metres below the surface - if they drop lower than this, they can be crushed by the higher hydrostatic pressure.”

Professor Stepanyants said researchers hope to develop a theory that allows them to predict where and when dangerous internal waves are likely to occur.

“The ocean doesn’t forgive mistakes. Therefore, we need a reliable theory,” he said.

“To reduce the risks, we need to allocate funding for expedition work, conduct ocean zoning to identify areas of intense internal waves and collect statistical data.

“In the future I believe we will have the whole picture on these wave phenomena, which will help us mitigate their negative effects.”

The study of physical oceanography is tightly intertwined with applied mathematics. Combining the rigour and logic of a scientific approach with the specifics of a professional area, the University of Southern Queensland’s Bachelor of Science in Applied Mathematics is designed for those interested in finding patterns in the nature, space and everyday events.

Find out more about studying a Bachelor of Science (Mathematics).

man smiling at the camera
University of Southern Queensland Professor of Applied Mathematics Yury Stepanyants.