Freak wave
Freak waves, also known as rogue waves or monster waves are relatively large and spontaneous ocean surface waves which can sink ships. Once thought to be legendary, they have in recent years come to be recognised as a natural and relatively common ocean phenomenon. ESA satellites, Project MaxWave, and the GKSS Research Centre have positively confirmed that these 30 metre high waves do exist.
They are a possible source of the sudden inexplicable disappearance of many ocean-going vessels.
History
Mid-ocean storm waves that are 7 metres, (23 feet), in height are common, and in extreme conditions such waves can reach heights of 15 metres, (50 feet), but for centuries maritime lore told of the existence of vastly more massive waves – veritable monsters, up to 30 metres, (100 feet), in height (approximately the height of a 12-story building) that could appear in mid-ocean, without warning, against the prevailing current and wave direction, and often in perfectly clear weather. Such waves were said to consist of an almost vertical wall of water preceded by a trough so deep that it was referred to as a "hole in the sea"; a ship encountering a wave of such magnitude would be unlikely to survive the tremendous pressures exerted on its hull by the weight of the breaking water, and would almost certainly be sunk in a matter of moments.
Scientists long dismissed such stories, asserting that mathematical probability indicated that ocean waves of greater than 15 metres in height were likely to be rare, "once in 10,000 years" type events. However, satellite imaging has in recent years confirmed that waves of up to 30 metres in height are much more common than mathematical probability, based on a linear model of wave size, indicates – and that in fact they occur in all of the world's oceans many times every year. This has caused a re-examination of the reason for their existence, as well as calling into question many long-established principles of maritime engineering.
Note that the localized freak waves discussed here are not the same as tsunami, formerly called "tidal waves". Far from the shore, tsunami
are shallow, large-scale phenomena which travel at high speed more or less unnoticed where crossing deep water, and only become dangerous as they "break" near the shoreline. In the deep sea, tsunami do not represent a threat to shipping.
Freak waves, in contrast, are localized deep phenomena which can occur far out to sea.
Possible causes of freak waves
The phenomenon of freak waves is still a matter of active research, so it is too early to say clearly what the most common causes are or whether they vary from place to place. The areas of highest predictable risk appear to be where a strong current runs counter to the primary direction of travel of the waves; the area near Cape Agulhas off the southern tip of Africa is one such area. However, since this thesis does not explain the existence of all waves which have been detected, several different mechanisms are likely, with localised variation. Suggested mechanisms for freak waves include the following:
According to some research , it is completely feasible to have a freak wave occur by natural nonlinear processes from a random background of smaller waves.
See also
Reports of freak waves
