This is interesting, from AALTO UNIVERSITY:
The 260-meter long German barge carrier MS München was lost mysteriously at sea in 1978. The final communication message was a garbled mayday message sent from the mid-Atlantic. Afterwards, only a few bits of wreckage were found, including an unlaunched lifeboat. The most accepted theory is that one or more rogue waves hit the MS München and damaged her.
Rogue waves – also called freak waves – are unusually large surface waves that occur in the ocean. People have usually reported them as having appeared suddenly or without warning, sometimes with tremendous force. A researcher from Aalto University has now learned how they may appear in realistic oceanic conditions.
Video: Potentially extremely dangerous realistic rogue waves can now be controlled and generated at will in laboratory environments. CREDITVisa Noronen, Amin Chabchoub, Sebastian Roede
– Potentially extremely dangerous realistic rogue waves can now be controlled and generated at will in laboratory environments, in similar conditions as they appear in the ocean. This will help us not only to predict oceanic extreme events, but also in the design of safer ships and offshore rigs. In fact, newly designed vessels and rig model prototypes can be tested to encounter in a small scale, before they are built, realistic extreme ocean waves. Therefore, initial plans may change, if models are not resistant enough to face suddenly occurring freak waves, says Professor Amin Chabchoub from Aalto University.
The birth of rogue waves can be physically explained through the modulation instability of water waves. In mathematical terms, this phenomenon can be described through exact solutions of the nonlinear Schrödinger equation, also referred to as “breathers”.
For a couple of years, the research team around Professor Chabchoub has already been able to create steered rogue waves in laboratory wave flumes. However, this has only succeeded in perfect regular wave conditions. In nature, this is rarely the case.
The article has been published today in Physical Review Letters.
Rogue, freak, or killer waves have been part of marine folklore for centuries, but have only been accepted as a real phenomenon by scientists over the past few decades.
Rogues, called ‘extreme storm waves’ by scientists, are those waves which are greater than twice the size of surrounding waves, are very unpredictable, and often come unexpectedly from directions other than prevailing wind and waves.
Most reports of extreme storm waves say they look like “walls of water.” They are often steep-sided with unusually deep troughs.
Since these waves are uncommon, measurements and analysis of this phenomenom is extremely rare. Exactly how and when rogue waves form is still under investigation, but there are several known causes:
Constructive interference. Extreme waves often form because swells, while traveling across the ocean, do so at different speeds and directions. As these swells pass through one another, their crests, troughs, and lengths sometimes coincide and reinforce each other. This process can form unusually large, towering waves that quickly disappear. If the swells are travelling in the same direction, these mountainous waves may last for several minutes before subsiding.
Focusing of wave energy. When waves formed by a storm develop in a water current against the normal wave direction, an interaction can take place which results in a shortening of the wave frequency. This can cause the waves to dynamically join together, forming very big ‘rogue’ waves. The currents where these are sometimes seen are the Gulf Stream and Agulhas current. Extreme waves developed in this fashion tend to be longer lived.