Assassin waves between the ocean

On a clear day the sky stopped, on the surface of the ocean suddenly appeared a wall of water from ten to thirty meters high - you had a "ghost wave" or "killer wave".

Ghost waves or killer waves on the ocean

Workers clean up debris on Louis Majesty at Barcelona port on March 4.The ship was damaged after meeting assassination waves on March 3.(Photo: AP.)

The ship - called Louis Majesty - was attacked when it was moving on the northeast coast of Spain. According to Louis Cruise Lines, which owns the ship, the waves have a height of up to 10 m. The shocking thing was that they appeared on a cloudy day without any warning signs.

'We heard a loud noise, then the waves hit us. When we ran out of the room, we found water overflowing on everything on the ship , 'Claudine Armand, a passenger from France, told AP.

Louis Majesty has no storm. In fact, it hit the ' killer waves '. For centuries, sailors and ocean explorers have told dozens of stories about waves that appear on the sea without warning. They are big and strong enough to dump massive ships.

The list of ships missing by assassination waves is getting longer. For example, Australia's SS Waratah - about 150 meters long - went missing on its way to South Africa in 1909 and 211 people.

German cargo ship MS München disappeared after leaving Germany's Bremerhaven port to Georgia on December 7, 1978. Even SS Edmund Fitzgerald - a 220m-long cargo ship of the United States and one of the largest ships in the Great Lakes region in North America - also mysteriously sank on November 10, 1975. The similarity is an accident that happens on a quiet, calm sea day (ie no warning signs). They did not encounter any storms (storms were always forewarned a few days). Until today it is thought that the ship met the assassin wave.

However, by the early 90s, the ocean experts still dismissed the story of assassination waves in sailors' stories. They thought it was just a product of imagination, because there was too little evidence of the existence of the killer wave. But in 1995, workers working on an oil rig in the North Sea recorded an image of a wave as high as 25.6 meters. By 2000, a British ocean research vessel recorded a 29-meter-high wave near the Scottish coast. In 2004, scientists from the European Space Agency discovered waves higher than 10-storey buildings on the ocean after analyzing images taken by satellites.

Scientists still do not know exactly how the killer wave formed and what to do to predict their appearance. Waves on the ocean form when the wind blows on the water. The stronger the wind, the higher the wave. That explains why big storms can create high water walls. In contrast, tsunamis do not create killer waves. In fact, tsunamis rarely ripple on the ocean but they only show the destructive power of approaching the mainland near the coast.

Assassin waves often appear in open waters - meaning they are not surrounded by mountains or land - on the ocean. It is possible that they are born by a combination of factors such as strong winds, fast-moving currents . Even small waves can create huge water walls if they combine. A small change in wind speed can also cause killer waves. Some waters have strong ocean currents, such as those near the coast of Africa, that have more killer waves than other waters.

Miguel Onorato and colleagues at the University of Turin in Italy and Swinburne University of Technology in Australia have made computer simulations that show how these ghosts can form when ocean waves normally touch a strong ocean current flowing in the opposite direction.

The above work builds on the notion that a pulse of three or four such waves can be described mathematically as a ' breather' , which is an exact solution of nonlinear Schrodinger development (NLS). . No ambiguity with its quantum brothers, NLS applies to classical physics, including water and optics.

Ghost waves can form near strong currents.(Photo: iStockphoto.com/Mlenny)

Focus on a breather

The team began to simulate with the flat wave type you encountered in the ocean - rising peaks with a amplitude of 2.5 m travel in a certain direction. These waves then encounter a stream of currents flowing in the opposite direction. When planar waves propagate from a region without a current to the ocean current, they cut through a flow gradient. The simulations show that the encounter with the gradient causes the energy of the plane wave to focus on a tiny region. This concentration causes an imbalance in the flat wave, triggering the appearance of a breather.

The simulation shows that formation of breather can occur when flat waves have a period of about 10 s - a typical condition in a storm - encounter a stream of currents flowing at a speed of about 1.5 m / s, a speed is not unavailable for the ocean currents.

Efim Pelinovsky of the Institute of Applied Physics at the Russian Academy of Sciences agrees with the research team on how the breather can form, and he said that the above process takes place in areas with Annual winds blow against the ocean currents. This condition is commonly found in the Indian Ocean off South Africa , where the Agulhas line has long appeared with ghost waves.