Australasian Science: Australia's authority on science since 1938

Freaks of the Sea

Image of freak wave

In 1978 the German cargo vessel MS München was struck by a freak wave 24–30 metres high. Image from Horizon – Freak Wave courtesy of BBC Worldwide. © BBC/Monkey Experiment

By Murray Rudman

Once the stuff of maritime legend, rogue waves up to 30 metres high have been detected by satellites, posing a significant threat to shipping and oil rigs. Now computational scientists are smashing virtual rogue waves into virtual oil and gas platforms to help design stronger, safer structures.

Dr Murray Rudman is Program Leader of Computational and Mathematical Modelling at CSIRO Mathematics, Informatics and Statistics in Melbourne.

The full text of this article can be purchased from Informit.

Rogue waves were once thought to be the folklore of mariners who had spent too much time at sea. Giant waves rising out of the blue in the open ocean, towering more than 20 metres in height, terrified sailors and damaged vessels.

Satellite and direct observations have now revealed that these freak waves really exist and pose a risk to ocean structures like oil rigs, as well as the workers on them. Fortunately, they are a risk that can be managed.

Freak waves, rogue waves or extreme waves, as they are variously called, are unpredictable, potentially deadly walls of water rising many times higher than neighbouring waves. To oceanographers, they are waves whose height is more than twice the significant wave height (SWH), which is defined as the mean of the largest one-third of waves in a given sea state. They are often preceded by a deep trough, which makes them appear even larger, and they may occur singly or in groups.

Unlike tsunamis, rogue waves are not caused by undersea earthquakes or landslides. What they are caused by is still largely a puzzle. Possible causes include currents, the shape of the sea bed, wind, storms and non-linear effects or interactions among these.

While rogue waves have been observed in storms like Hurricane Katrina, they have also been recorded in fine weather. Further research is needed to determine their causes....

The full text of this article can be purchased from Informit.