Small waves source for 'monster' waves
Swedish researchers have found that ordinary waves can turn into the 'monster' or 'rogue' waves large enough to sink ships or disturb oil platforms. The researchers have also found that these waves build up more quickly than previously thought. The research, from scientists at the University of Umeå in Sweden, has pinpointed what can turn normal waves into huge waves on apparently calm seas. These waves are not tsunamis - caused by undersea earthquakes - but ordinary waves that have mutated and grown into giant walls of water with lethal power. While sailors have reported these freak waves for centuries, it was only in 1995 that the first positive account of a monster wave was reported. On 1 January, the Draupner oil platform in the North Sea was hit by a wave of close to 20m in height, from a sea registering wave heights of no more than 6 or 7m. The wave inflicted some damage to the platform. Vessels encountering these types of wave could be rapidly overwhelmed, and rogue waves have been implicated in a number of unexplained shipwrecks over the years. Anecdotal evidence suggests waves of some 30m in height - as large as a 12-story building - although the largest wave ever recorded was 29.1m from crest to trough in Rockall, off the western Scottish coast in 2000. 'The consequences of an encounter with monster waves are catastrophic for those working on ships and oil platforms. These new research findings can enhance our knowledge of how and why monster waves form. Detailed knowledge of this phenomenon will be a cornerstone in finding methods to predict the course of these waves,' said researcher Mattias Marklund, professor of physics at Umeå University. The results are published in the latest edition of the journal Physical Review Letters The team has shown that the freak waves are the result of special interactions between ordinary waves and the wind. Waves can borrow energy from neighbouring waves. Computer simulations have shown that a 'non-linear' effect is at work, and that the waves can grow extremely quickly. This confirms research conducted by the Fifth Framework Programme (FP5) project MaxWave, which used the European Space Agency's Earth Remote Sensing satellites to scan the seas in 2001, discovering 10 waves of 25 metres in a three-week period.
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Sweden