Rogue Waves

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  • Topic: Tsunami, Wave, Rogue wave
  • Pages : 6 (2072 words )
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  • Published : March 23, 2012
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Rogue Waves
For centuries, mariners have spread stories about giant sudden waves which appeared out of nowhere without warning which were strong enough to capsize even the mightiest and largest ships. Several vessels—such as the S.S. Waratah, the M.S. Munchen, and the S.S. Edmund Fitzgerald—were all rumored to have been sunk by rogue waves (Walsh par. 3). Further, rogue waves have been blamed for ripping the bow off of a Norwegian freighter near the tip of South Africa in 1974, almost capsizing the Queen Elizabeth in 1942 off the coast of Greenland, striking the Queen Elizabeth H in 1995, and for swamping military aircraft carriers and tearing tankers in half (McDonald A21). These waves have also been immortalized in popular culture, as evidenced by the 1972 film The Poseidon Adventure and its 2006 remake Poseidon. These huge waves are called rogue waves—or monster or freak waves—and can be encountered during bad weather storms or even in calm seas, but the fundamental aspect is that they appear with little warning. The biggest problem is the lack of scientific data from shipboard measurements of such waves because of their propensity to appear quickly and without warning. Rogue waves can also disappear as quickly as they form. Scientists have been studying the formation and characteristics of rogue waves with the goal of creating an accurate prediction and detection method to mitigate the potential damage of these waves. 2

Generally, ocean waves are created by “random pressure fluctuations in the turbulent wind … [and] reinforced in a feedback process that involves the airflow over the wavy surface” that creates a wave’s crests and troughs which travel at the wave’s phase speed (Garrett & Gemmrich 62). In other words, waves are created when the wind produces a ripple across the surface of a body of water that increases with the wind’s intensity and speed. Waves can also interact with currents, seabeds, and coastal features of shallow waters (Wallace par. 6). Initial waves are relatively short and succumb to wind pressure; however, interactions between multiple waves have the potential to transfer energy into creating longer and faster ones. As the wind increases in strength and duration, waves become larger and longer and the variations in different wavelengths produce the appearance of a turbulent and rough sea. Waves tend to travel at the “group speed”—defined as “half the phase speed for all but the shortest waves” (Garrett & Gemmrich 62). Hurricanes can increase the wave amplification to a few stories; however, rogue waves can be as high as ten stories. Accordingly, rogue waves occur when a regular wave “exceed[s] the surrounding waves by a certain proportion” (Perkins 328). The basis for comparison is significant wave height—an oceanographic parameter calculated by “taking the average of the tallest one-third of the waves in a particular patch of ocean” (Perkins 328). Consequently, scientists classify a wave as a rogue if it is “2.2 times as tall as the significant wave height” (Perkins 328). Rogue waves can range from 20-foot waves which suddenly appear in two- to three-foot surf as was the case in Daytona Beach, Florida in 1992 to over-100-foot waves during a nor’easter with 20-foot swells (McDonald A21). Basically, rogue waves are those waves which “don’t fit the pattern” (McDonald A21). 3

Rogue waves also differ from “regular” waves in their shape. Whereas regular waves have “the approximate shape of a smoothly curving sine wave”, rogue waves’ profiles are more divergent from this sine wave with much higher crests and deeper troughs which have been described as “mountains of water” and “holes in the sea” (Perkins 328). Some mariners who have experienced rogue waves describe these troughs as riding a down elevator. Further, rogue waves differ from tsunamis and tidal waves in that the latter are both extremely rare instances which are caused by an earthquake, volcanic eruptions, or landslide which...
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