Rogue waves
(also known as freak waves
, monster waves
, killer waves
, and extreme waves
) are relatively large and spontaneous ocean surface waves that are a threat even to large ships and ocean liners. In oceanography, they are more precisely defined as waves whose height is more than twice the significant wave height (SWH), which is itself defined as the mean of the largest third of waves in a wave record. Therefore rogue waves are not necessarily the biggest waves found at sea; they are, rather, surprisingly large waves for a given sea state.
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ROGUE WAVE TICKETS
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Background
Once thought by scientists to exist only in legends, rogue waves are now known to be a natural ocean phenomenon.
Anecdotal evidence from mariners' testimonies and damages inflicted on ships have long suggested they occurred; however, their scientific measurement was only positively confirmed following measurements of the "
Draupner wave", a rogue wave at the Draupner oil platform, in the
North Sea on
January 1,
1995. During this event, minor damage was inflicted on the platform, confirming that the reading was valid.
Freak waves have been cited in the media as a likely source of the sudden, inexplicable disappearance of many ocean-going vessels. One of the very few cases in which evidence exists that
may
indicate a freak wave incident is the 1978 loss of the freighter
MS München
, detailed below. In February 2000, a British oceanographic research vessel sailing in the
Rockall Trough west of Scotland encountered the largest waves ever recorded by scientific instruments in the open ocean, with a SWH of and individual waves up to .
[1]
History
It is common for mid-ocean storm waves to reach in height, and in extreme conditions such waves can reach heights of .
However, for centuries maritime
folklore told of the existence of vastly more massive waves — veritable monsters up to in height (approximately the height of a 10-story building) — that could appear without warning in mid-ocean, 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 of up to exerted by the weight of the breaking water, and would almost certainly be sunk in a matter of minutes.
Many years of research have confirmed that waves of up to in height are much more common than mathematical
probability theory would predict using a
Rayleigh distribution of wave heights. In addition, pressure readings from
buoys moored in the
Gulf of Mexico at the time of
Hurricane Katrina also indicated the presence of such large waves at the time of the storm. In fact, they seem to occur in all of the world's oceans many times every year. This has caused a re-examination of the reasons for their existence, as well as reconsideration of the implications for ocean-going
ship design.
Rogue waves are also known to occur on the
Great Lakes, which are more like large inland seas. Perhaps most famously, such inland freak waves are believed, according to some reconstructions, to be responsible for the sinking of the in November 1975 (see below). However, other causes have been advanced, and the matter is far from settled.
A rogue wave is not the same as a
tsunami. Tsunamis are mass displacement generated waves which propagate at high speed and are more or less unnoticeable in deep water; they only become dangerous as they approach the shoreline and do not present a threat to shipping (the only ships lost in the
2004 Asian tsunami were in port). A rogue wave, on the other hand, is a spatially and temporally localized event that most frequently occurs far out at sea.
Rogue waves may sometimes be referred to as "hundred-year waves," due to the supposed likelihood of their occurrence.
[2] They should not be confused, however, with the
hundred-year wave, which is a
statistical prediction of the highest wave likely to occur in a hundred-year period in a particular body of water. These predictions are typically based on wave models which do not take rogue waves into account.
Occurrence
In the course of Project MaxWave, researchers from the GKSS Research Centre, using data collected by
ESA satellites, identified a large number of radar signatures that have been portrayed as evidence for rogue waves. Further research is under way to develop better methods of translating the radar echoes into sea surface elevation, but at present this technique is not proven.
[3] [4]
Causes
The phenomenon of rogue 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 that have been detected, several different mechanisms are likely, with localised variation. Suggested mechanisms for freak waves include the following:
- Diffractive focusing — According to this hypothesis, coast shape or seabed shape directs several small waves to meet in phase. Their crest heights combine to create a freak wave. [5]
- Focusing by currents — Storm forced waves are driven into an opposing current. This results in shortening of wavelength, causing shoaling (i.e., increase in wave height), and oncoming wave trains to compress together into a rogue wave.
- Nonlinear effects — It seems possible to have a rogue wave occur by natural, nonlinear processes from a random background of smaller waves.
In such a case, it is hypothesised, an unusual, unstable wave type may form which 'sucks' energy from other waves, growing to a near-vertical monster itself, before becoming too unstable and collapsing shortly after. One simple model for this is a wave equation known as the nonlinear Schrödinger equation (NLS), in which a normal and perfectly accountable (by the standard linear model) wave begins to 'soak' energy from the waves immediately fore and aft, reducing them to minor ripples compared to other waves. The NLS is only valid in deep water conditions, and in shallow water an alternative such as the Boussinesq equation is used.
- Normal part of the wave spectrum — Rogue waves are not freaks at all but are part of normal wave generation process, albeit a rare extremity.
- Wind waves — While it is unlikely that wind alone can generate a rogue wave, its effect combined with other mechanisms may provide a fuller explanation of freak wave phenomena. As wind blows over the ocean, energy is transferred to the sea surface. Theories of instability mechanisms for the generation and growth of wind waves—although not on the causes of rogue waves—are provided by Phillips [6] and Miles. [7]
The spatio-temporal focusing seen in the NLS equation can also occur when the nonlinearity is removed. In this case, focusing is primarily due to different waves coming into phase, rather than any energy transfer processes. Further analysis of rogue waves using a fully nonlinear model by R.H. Gibbs (2005) brings this mode into question, as it is shown that a typical wavegroup focuses in such a way as to produce a significant wall of water, at the cost of a reduced height.
A rogue wave, and the deep trough commonly seen before and after it, may last only for some minutes before either breaking, or reducing in size again. Apart from one single rogue wave, the rogue wave may be part of a wave packet consisting of a few rogue waves. Such rogue
wave groups have been observed in nature.
[8]
There are three categories of freak waves:
- "Walls of water" travelling up to through the ocean
- "Three Sisters", groups of three waves [9]
- Single, giant storm waves, building up to fourfold the storm's waves height and collapsing after some seconds [10]
A research group at the
Umeå University,
Sweden in August 2006 showed that normal
stochastic wind driven waves can suddenly give rise to monster waves. The nonlinear evolution of the instabilities was investigated by means of direct simulations of the time-dependent system of nonlinear equations.
[11]
Applications
The possibility of the artificial stimulation of rogue wave phenomena, has attracted research funding from
DARPA, an agency of the
United States Department of Defense. Bahram Jalali and other researchers at
UCLA studied microstructured
optical fibers near the threshold of
soliton supercontinuum generation and observed rogue wave phenomena. After modeling the effect, the researchers announced that they had successfully characterized the proper initial conditions for generating rogue waves in any medium.
[12]
Reported encounters
It should be noted that many of these encounters are only reported in the media, and are not examples of open ocean rogue waves. Often, in popular culture, an endangering huge wave is loosely denoted as a
rogue wave
, while it has not been (and most often cannot be) established that the reported event is a rogue wave in the scientific sense —
i.e.
of a very different nature in characteristics as the surrounding waves in that
sea state and with very low probability of occurrence (according to a
Gaussian process description as valid for
linear wave theory).
This section lists a limited selection of notable incidents.
Twentieth century
- The Eagle Island lighthouse (1861) – water would have had to surmount a seaside cliff measuring 40 m (133 ft) and a further 26 m (87 ft) of lighthouse structure. [13]
- AO-12}} (1933) – triangulated at . [14]
- (1942) – broadsided by a wave and listed briefly about 52 degrees before slowly righting.
- Michelangelo
1966) – hole torn in superstructure, heavy glass smashed above the waterline, and 3 deaths.
- (1975) – lost on Lake Superior. A Coast Guard report blamed water entry to the hatches, which gradually filled the hold, or alternatively errors in navigation or charting causing damage from running onto shoals. However, another nearby ship, the , was hit at a similar time by two rogue waves, and this appeared to coincide with the sinking around ten minutes later. A Discovery Channel
reconstruction pointed towards freak waves as the cause.
- MS München ()| (1978) – lost at sea leaving only "a few bits of wreckage" and signs of sudden damage including extreme forces above the water line. Although more than one wave was probably involved, this remains the most likely sinking due to a freak wave. [15]
- Draupner wave (North Sea, 1995) – First rogue wave confirmed with scientific evidence, it had a maximum height of .
- – North Atlantic, September 1995, , during Hurricane Luis:The Master said it "came out of the darkness" and "looked like the White Cliffs of Dover."
[16] ''Newspaper reports at the time described the cruise liner as attempting to "surf" the near-vertical wave in order not to be sunk.
Twenty-first century
- MS Bremen ()| and Caledonian Star
(South Atlantic, 2001) encountered freak waves. Bridge windows on both ships were smashed, and all power and instrumentation lost. There was a video camera on the bridge recording the event.
- Naval Research Laboratory ocean-floor pressure sensors detected a freak wave caused by Hurricane Ivan in the Gulf of Mexico, 2004. The wave was around high from peak to trough, and around long. [17]
- Aleutian Ballad
, (Bering Sea, 2005) Footage of a rogue wave appears in an episode of Deadliest Catch
. The wave cripples the vessel, causing the boat to tip for a short period onto its side. One of the few video recordings of (what might be) a rogue wave. [18]
- It has also been suggested that these types of waves may be responsible for the loss of several low-flying aircraft, namely U.S. Coast Guard helicopters on Search and Rescue missions. [19]
Loss estimates
Freak waves have been cited in the media as a likely source of the sudden, inexplicable disappearance of many ocean-going vessels. However, although this is a credible explanation for unexplained losses, there is to date little clear evidence supporting this hypothesis nor any cases where the cause has been confirmed, and the claim is contradicted by information held by Lloyd's Register. [20] [21] One of the very few cases in which evidence exists that may
indicate a freak wave incident is the 1978 loss of the freighter München
.
In popular culture
- The film Poseidon
from 2006 explores the capsizing of an ocean liner by a rogue wave and the struggle of passengers to survive. The film is a remake of The Poseidon Adventure
from 1972, itself an adaptation of Paul Gallico's novel, which was published in 1969. In the original novel and film, the ship was hit by a tsunami, which raised some criticism.
- New York alternative rock band Brand New references rogue waves in "Play Crack the Sky", a track on their second album, Deja Entendu
. The exact line is "They call them rogues, they travel fast and alone; one hundred foot faces of God's good ocean gone wrong".
- Rogue Wave is the name of an indie rock band from Oakland, California.
- In the final minutes of The Perfect Storm
(2000), a massive rogue wave appears just as the title storm of the movie appears to be dying down, and capsizes the Andrea Gail
. In the real-life loss of the Andrea Gail
, there is no evidence that the boat encountered or was destroyed by a rogue wave.
See also
- Antarctic Circumpolar Current (ACC) or West Wind Drift
- Agulhas Current
- Bermuda Triangle
- Clapotis
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- Extreme value theory
- Gulf Stream
- Kuroshio Current
- Megatsunami
- Ocean current
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- Ocean surface wave
- Sneaker wave
- Soliton
- White squall
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References
- Holliday, NP, MJ Yelland, RW Pascal, VR Swail, PK Taylor, CR Griffiths, and EC Kent (2006). Were extreme waves in the Rockall Trough the largest ever recorded? Geophysical Research Letters, Vol. 33, L05613
- ''A Dictionary of Slang and Unconventional English''
- Critical review on potential use of satellite date to find rogue waves
- Freak waves spotted from space
- Rogue Waves
- Phillips 1957, ''Journal of Fluid Mechanics''
- Miles, 1957, ''Journal of Fluid Mechanics''
- Frederic-Moreau. The Glorious Three, translated by M. Olagnon and G.A. Chase / Rogue Waves-2004, Brest, France
- ''Endeavour'' or ''Caledonian Star'' report, March 2 2001, {{Coord|53|03|S|63|35|W|}}
- MS Bremen
report, February 22 2001, {{Coord|45|54|S|38|58|W|}}
- P. K. Shukla, I. Kourakis, B. Eliasson, M. Marklund and L. Stenflo: "Instability and Evolution of Nonlinearly Interacting Water Waves"
nlin.CD/0608012, ''Physical Review Letters'' (2006)
- R. Colin Johnson: "EEs Working With Optical Fibers Demystify 'Rogue Wave' Phenomenon" ''Electronic Engineering Times'' (Dec 24, 2007)
- [1]
- Rogue Giants at Sea, Broad, William J, ''New York Times'', July 11, 2006
- Freak Wave, BBC.co.uk programme summary for ''Horizon'' episode aired on 14 November 2002
- {{PDFlink|Freak waves|1.07 MiB}}, ''Beacon'' #185, Skuld, June 2005
- Hurricane Ivan prompts rogue wave rethink, ''The Register'', 5 August 2005
- Deadliest Catch Season 2, Episode 4 "Finish Line" Original airdate: April 28 2006; approx time into episode: 0:40:00 - 0:42:00. Edited footage viewable online at Discovery.com
- {{PDFlink|Monster waves threaten rescue helicopters|35.7 KiB}}, U.S. Naval Institute, December 15, 2006
- [1]
- The story that "200 large ships lost to freak waves in the past two decades" was published in ''The Times'' (May 2006). The earliest reference seems to be in the press release by the European Space Agency (cited at the page bottom), and first quoted as "200 large ships of 600ft long or more in the past two decades sunk without trace". At the time the claim was made, there had only been 142 ships of that size lost at sea in the time frame, all with clear, known causes (source: Lloyd's Register - Fairplay). The main culprits were the Iranian and Iraqi air forces in the 1980s (See: Iran-Iraq war).