Freak Wave - programme summary
The world's oceans claim on average one ship a week, often in mysterious circumstances. With little evidence to go on, investigators usually point at human error or poor maintenance but an alarming series of disappearances and near-sinkings, including world-class vessels with unblemished track records, has prompted the search for a more sinister cause and renewed belief in a maritime myth: the wall of water. Waves the height of an office block. Waves twice as large as any that ships are designed to ride over.

These are not tsunamis or tidal waves, but huge breaking walls of water that come out of the blue. Suspicions these were fact not fiction were roused in 1978, by the cargo ship München. She was a state-of-the-art cargo ship. The December storms predicted when she set out to cross the Atlantic did not concern her German crew. The voyage was perfectly routine until at 3am on 12 December she sent out a garbled mayday message from the mid-Atlantic. Rescue attempts began immediately with over a hundred ships combing the ocean.

"We hoped to find at least a life-raft with people. We never found a living soul"
Captain Pieter de Nijs, München search co-ordinator
The ship was never found. She went down with all 27 hands. An exhaustive search found just a few bits of wreckage, including an unlaunched lifeboat that bore a vital clue. It had been stowed 20m above the water line yet one of its attachment pins had twisted as though hit by an extreme force. The Maritime Court concluded that bad weather had caused an unusual event. Other seafarers could not help but consider the possibility of a mythical freak wave.

Freak waves are the stuff of legend. They aren't just rare, according to traditional views of the sea, they shouldn't exist at all. Oceanographers and meteorologists have long used a mathematical system called the linear model to predict wave height. This assumes that waves vary in a regular way around the average (so-called 'significant') wave height. In a storm sea with a significant wave height of 12m, the model suggests there will hardly ever be a wave higher than 15m. One of 30m could indeed happen - but only once in ten thousand years.

Except they do happen with startling frequency. Since 1990, 20 vessels have been struck by waves off the South African coast that defy the linear model's predictions. And on New Year's Day, 1985 a wave of 26m was measured hitting the Draupner oil rig in the North Sea off Norway. Concerned shipping operators wanted to know what was going on. The largest wave marine architects are required to accommodate in the design strength calculations is 15m from trough to crest. If that assumption were to be proved false, the whole world shipping industry would face some very tough choices.

What could cause such extreme waves? Curious about the spate of South African incidents, oceanographer Marten Grundlingh plotted the strikes on thermal sea surface maps. All the ships had been at the edge of the Agulhas Current, the meeting point of two opposing flows mixing warm Indian Ocean water with a colder Atlantic flow. Radar surveillance by satellite confirmed that wave height at the edge of this current could grow well beyond the linear model's predictions, especially if the wind direction opposed the current flow.

Problem solved: the answer was just to avoid certain ocean currents in certain weather conditions. There was nothing freakish about large waves; the mariners' myth was an explicable phenomenon. To science, this was one that didn't get away.

"Out of nowhere... a wave twice as high as average. The ship went down like freefall"
Göran Persson, Caledonian Star First Officer
Unfortunately, ocean currents could not explain two near disastrous wave strikes in March 2001. Once more two reputable ships, designed to cope with the very worst conditions any ocean could throw at them, were crippled to the point of sinking. The Bremen and Caledonian Star were carrying hundreds of tourists across the South Atlantic. At 5am on 2 March the Caledonian Star's First Officer saw a 30m wave bearing down on them.

It smashed over the ship, flooding the bridge and destroying much of the navigation and communication equipment. The Caledonian Star limped back to port, her crew and passengers grateful that the engines had kept running, despite the onslaught.

Just days earlier, the cruise liner Bremen had been less fortunate. 137 German tourists were aboard when she too faced an awesome wall of water in the South Atlantic. The impact knocked out all the instrumentation and all power, leaving them helpless in the tumultuous sea. Unable to maintain her course into the waves, there was a real risk the ship could go down and they knew none of the passengers would survive in lifeboats in such freezing conditions. With emergency power only, the crew battled to restart the engines. When they eventually succeeded, it opened the door to a very lucky escape.

"We had said, 'This kind of thing can't happen; this kind of thing is too strange'"
Al Osborne, wave mathematician
No current could have created such huge waves. There is none in that part of the Atlantic. Clearly, there was another effect investigators needed to find. Except someone already had: it existed (on paper at least) in the world of quantum physics. Al Osborne is a wave mathematician with 30 years experience devising equations to describe open ocean wave patterns. Quantum physics has at its heart a concept called the Schrodinger Equation, a way of expressing the probability of something happening that is far more complex than the simple linear model. Al's theory is based on the notion that in certain unstable conditions, waves can steal energy from their neighbours. Adjacent waves shrink while the one at the focus can grow to an enormous size. His modified Schrodinger Equation had been rejected in the past as implausible, but with research attention centred on analysing these rogue waves - including global satellite radar surveillance by the new European Remote Sensing Satellite - data began to emerge backing his case. When Al came across the New Year's Day 1985 wave profiles from the Draupner oil rig, he saw his mathematical model played out in the real world.

Al's work - if correct - suggests that there are two kinds of waves out on the high seas; the classical undulating type described by the linear model and an unstable non-linear monster - a wave that at any time can start sucking up energy from waves around it to become a towering freak. The consequences for ship design could be stark.

Currently the biggest wave factored into most ship design is smooth, undulating and 15m high. A freak wave is not only far bigger, it is so steep it is almost breaking. This near-vertical wall of water is almost impossible to ride over - the wave just breaks over the ship. According to accident investigator, Rod Rainey, such a wave would exert a pressure of 100 tonnes per square metre on a ship, far greater than the 15 tonnes that ships are designed to withstand without damage. It's no wonder that even ships the size of the huge freighter München can sink without trace.

For full programme transcript, go to;

www.bbc.co.uk/science/hor...etrans.shtml

Record ocean waves are recorded

British scientists report observing some of the largest waves ever measured -- reportedly so big, some computer models indicate they shouldn't even exist.

The observations occurred Feb. 8, 2000, aboard the Royal Research Ship Discovery during a scientific expedition to the North Atlantic, 155 miles west of Scotland, when a series of gigantic waves hammered the vessel.

The scientists set to sea because an intense storm was forecast and the researchers from Britain's National Oceanography Center, located in Southampton, wanted to closely observe it, der Spiegel reported.

The scientists' measuring instruments showed the tallest of the waves was nearly 98 feet high and the giant waves shook the ship for 12 hours, said Naomi Holliday, the leader of the expedition.

The Discovery's crew witnessed waves of up to 95 feet from trough to crest -- the highest waves ever measured by a scientific instrument on the open sea, according to an article the scientists published in the journal Geophysical Research Letters.

The new data may be troubling for shipbuilders, said der Spiegel, since the scientists' data suggest giant waves may be much more common than has been thought.


www.physorg.com/news63294887.html

Rogue Giants at Sea

By WILLIAM J. BROAD
Published: July 11, 2006
The storm was nothing special. Its waves rocked the Norwegian Dawn just enough so that bartenders on the cruise ship turned to the usual palliative — free drinks.

, off the coast of Georgia, early on Saturday, April 16, 2005, a giant, seven-story wave appeared out of nowhere. It crashed into the bow, sent deck chairs flying, smashed windows, raced as high as the 10th deck, flooded 62 cabins, injured 4 passengers and sowed widespread fear and panic.

“The ship was like a cork in a bathtub,” recalled Celestine Mcelhatton, a passenger who, along with 2,000 others, eventually made it back to Pier 88 on the Hudson River in Manhattan. Some vowed never to sail again.

Enormous waves that sweep the ocean are traditionally called rogue waves, implying that they have a kind of freakish rarity. Over the decades, skeptical oceanographers have doubted their existence and tended to lump them together with sightings of mermaids and sea monsters.

But scientists are now finding that these giants of the sea are far more common and destructive than once imagined, prompting a rush of new studies and research projects. The goals are to better tally them, understand why they form, explore the possibility of forecasts, and learn how to better protect ships, oil platforms and people.

The stakes are high. In the past two decades, freak waves are suspected of sinking dozens of big ships and taking hundreds of lives. The upshot is that the scientists feel a sense of urgency about the work and growing awe at their subjects.

“I never met, and hope I never will meet, such a monster,” said Wolfgang Rosenthal, a German scientist who helped the European Space Agency pioneer the study of rogue waves by radar satellite. “They are more frequent than we expected.”

Drawing on recent tallies and making tentative extrapolations, Dr. Rosenthal estimated that at any given moment 10 of the giants are churning through the world’s oceans.

In size and reach these waves are quite different from earthquake-induced tsunamis, which form low, almost invisible mounds at sea before gaining height while crashing ashore. Rogue waves seldom, if ever, prowl close to land.

“We know these big waves cannot get into shallow water,” said David W. Wang of the Naval Research Laboratory, the science arm of the Navy and Marine Corps. “That’s a physical limitation.”

By one definition, the titans of the sea rise to heights of at least 25 meters, or 82 feet, about the size of an eight-story building. Scientists have calculated their theoretical maximum at 198 feet — higher than the Statue of Liberty or the Capitol rotunda in Washington. So far, however, they have documented nothing that big. Large rogues seem to average around 100 feet.

Most waves, big and small alike, form when the wind blows across open water. The wind’s force, duration and sweep determine the size of the swells, with big storms building their height. Waves of about 6 feet are common, though ones up to 30 or even 50 feet are considered unexceptional (though terrifying to people in even fairly large boats). As waves gain energy from the wind, they become steeper and the crests can break into whitecaps.

The trough preceding a rogue wave can be quite deep, what nautical lore calls a “hole in the sea.” For anyone on a ship, it is a roller coaster plunge that can be disastrous.

Over the centuries, many accounts have told of monster waves that battered and sank ships. In 1933 in the North Pacific, the Navy oiler Ramapo encountered a huge wave. The crew, calm enough to triangulate from the ship’s superstructure, estimated its height at 112 feet.

In 1966, the Italian cruise ship Michelangelo was steaming toward New York when a giant wave tore a hole in its superstructure, smashed heavy glass 80 feet above the waterline, and killed a crewman and two passengers. In 1978, the München, a German barge carrier, sank in the Atlantic. Surviving bits of twisted wreckage suggested that it surrendered to a wave of great force.

Despite such accounts, many oceanographers were skeptical. The human imagination tended to embellish, they said.

Moreover, bobbing ships were terrible reference points for trying to determine the size of onrushing objects with any kind of accuracy. Their mathematical models predicted that giant waves were statistical improbabilities that should arise once every 10,000 years or so.

That began to change on New Year’s Day in 1995, when a rock-steady oil platform in the North Sea produced what was considered the first hard evidence of a rogue wave. The platform bore a laser designed to measure wave height.

During a furious storm, it registered an 84-foot giant.

Then, in February 2000, a British oceanographic research vessel fighting its way through a gale west of Scotland measured titans of up to 95 feet, “the largest waves ever recorded by scientific instruments,” seven researchers wrote in the journal Geophysical Research Letters.

Once-skeptical scientists were soon holding conferences to discuss the findings and to design research strategies. A large meeting in Brest, France, in November 2000 attracted researchers from around the world.

It quickly became apparent that the big waves formed with some regularity in regions swept by powerful currents: the Agulhas off South Africa, the Kuroshio off Japan, and the Gulf Stream off the eastern United States, where the Norwegian Dawn got into trouble off Georgia. The Gulf Stream also flows through the Bermuda Triangle, famous for allegedly devouring large numbers of ships.

Dr. Bengt Fornberg, a mathematician at the University of Colorado who studies the giants, said the strong ocean currents appeared to focus waves “like a magnifying glass concentrates sunlight.”

“It’s the same idea,” he said. “There are a few places in the world where there is a regular current, like a steady magnifying glass. In other places, the eddies come and go, and that makes the waves less predictable.”

One way that rogue waves apparently form is when the strong currents meet winds and waves moving in the opposite direction, he said. The currents focus and concentrate sets of waves, shortening the distance between them and sending individual peaks higher. “That,” Dr. Fornberg said in an interview, “makes for hot spots in a fairly predictable area.”

A particularly threatening spot, he said, turned out to be where big oil tankers coming from the Middle East ride the Agulhas current around South Africa. There, the westward-flowing current meets prevailing easterly winds, at times disastrously.

“Three or four tankers a year there get badly damaged,” Dr. Fornberg said. “That’s one of the few places in the world where the phenomena is regular.”

“With a big storm, you get lots of big waves,” he added. “You have regular waves and then one or two giants. Then it’s back to regular again.”

The scientists who met at Brest in 2000, eager to track the phenomenon globally, laid plans to use radar satellites to conduct a census, calling it MaxWave.

They worked with the European Space Agency, which had lofted radar satellites in 1991 and 1995, as well as the German Aerospace Center and several other European research bodies. The radar beams were seen as potentially ideal for measuring the height of individual waves, based on the time it took the beams to bounce from orbit to the sea and back to space.

The MaxWave team, led by Dr. Rosenthal, examined three weeks of radar data and to its amazement discovered 10 giants, each at least 82 feet high. “We were quite successful,” he said.

The team even tracked monster waves in a region of the South Atlantic where two cruise ships, the Bremen and the Caledonian Star, had come under assault.

Further confirmation with a different set of instruments came in September 2004 when Hurricane Ivan swept through the Gulf of Mexico.

It passed directly over six wave-tide gauges that the Naval Research Laboratory had deployed about 50 miles east of the Mississippi Delta. Dr. Wang and his colleagues analyzed the data and found to their surprise waves measuring more than 90 feet from trough to crest.

“We had no idea,” Dr. Wang recalled. “It was the right time and the right place.”

Already, the scientists said, naval architects and shipbuilders are discussing precautions. Some of the easiest are seen as increasing the strength of windows and hatch covers. But even the best physical protections may fail under assault by tons of roiling water, so the best precaution of all will be learning how to avoid the monsters in the first place.

Increasingly, scientists are focusing on better understanding how the big waves form and whether that knowledge can lead to accurate forecasts — a feat that, if achieved, may save hundreds of lives and many billions of dollars in lost commerce.

A suspected culprit, in addition to wind-current interactions, is the amplification that occurs when disparate trains of waves (perhaps emanating from different storms) come together. Such intersections are seen as sometimes canceling out waves, and other times making them higher and steeper.

Another birth ground is seen as choppy seas where several waves moving independently merge by chance. But scientists say a giant of that sort would live for no more than a few seconds or minutes, whereas some are suspected of lasting for hours and traveling long distances.

As for forecasts, oceanographers are focusing on the interplay of exceptionally strong winds and currents, especially in the Agulhas off South Africa.

Dr. Fornberg said that several years ago South African authorities began issuing predictions. “That’s the only place the theory has succeeded,” he said.

Dr. Rosenthal said that in the future the continued proliferation of radar satellites should create an opportunity to better understand not only the habitats of the giants but in theory also individual threats, bringing about a safer relationship between people and the sea.

“There will be warnings, maybe in 10 years,” he said. “It should be possible.”


www.nytimes.com/2006/07/11...11wave.html

Researchers capture optical 'rogue waves'
Maritime folklore tells tales of giant "rogue waves" that can appear and disappear without warning in the open ocean. Also known as "freak waves," these ominous monsters have been described by mariners for ages and have even appeared prominently in many legendary literary works, from Homer's "Odyssey" to "Robinson Crusoe."

Once dismissed by scientists as fanciful sailors' stories akin to sea monsters and uncharted inlands, recent observations have shown that they are a real phenomenon, capable of destroying even large modern ships. However, this mysterious phenomenon has continued to elude researchers, as man-made rouge waves have not been reported in scientific literature — in water or in any other medium.

Now, researchers at the UCLA Henry Samueli School of Engineering and Applied Science have succeeded in creating and capturing rogue waves. In their experiments, they have discovered optical rogue waves — freak, brief pulses of intense light analogous to the infamous oceanic monsters — propagating through optical fiber. Their findings appear in the Dec. 13 issue of the journal Nature.

"Optical rogue waves bear a close connection to their oceanic cousins," said lead investigator Daniel Solli, a UCLA Engineering researcher. "Optical experiments may help to resolve the mystery of oceanic rogue waves, which are very difficult to study directly."

It is thought that rogue waves are a nonlinear, perhaps chaotic, phenomenon, able to develop suddenly from seemingly innocuous normal waves. While the study of rogue waves has focused on oceanic systems and water-based models, light waves traveling in optical fibers obey very similar mathematics to water waves traveling in the open ocean, making it easier to study them in a laboratory environment.

Still, detecting a rogue wave is like finding a needle in a haystack. The wave is a solitary event that occurs rarely, and, to make matters worse, the timing of its occurrence is entirely random. But using a novel detection method they developed, the UCLA research group was able to not only capture optical rogue waves but to measure their statistical properties as well.

They found that, similar to freak waves in the ocean, optical rogue waves obey "L-shaped" statistics - a type of distribution in which the heights of most waves are tightly clustered around a small value but where large outliers also occur. While these occurrences are rare, their probability is much larger than predicted by conventional (so-called normal or Gaussian) statistics.

"This discovery is the first observation of man-made rogue waves reported in scientific literature, but its implications go beyond just physics," said Bahram Jalali, UCLA professor of electrical engineering and the researcher group leader. "For example, rare but extreme events, popularly known as "black swans," also occur in financial markets with spectacular consequences. Our observations may help develop mathematical models that can identify the conditions that lead to such events."

Source: University of California - Los Angeles


www.physorg.com/news116691200.html

Freak wave 'hot spots' identified
By Griet Scheldeman
Science reporter, BBC News


Scientists in the US have made a major advance in their understanding of so-called freak waves.

These monster waves present a major risk to ships and offshore platforms.

A computer simulation developed by oceanographers in the US could help locate where and when these "rogue" phenomena are most likely to occur.

The theoretical study shows that coastal areas with variations in water depth and strong currents are hot spots for freak waves.

The history of seafaring is littered with tales of rogue waves capable of rending ships asunder.

A freak wave is one that measures roughly three times higher than other swells on the sea at any one time. These phenomena can measure up to 18m (60ft) - the height of a six-storey building.

The new computer simulation was developed by Tim Janssen of San Francisco State University (SFSU) and Thomas HC Herbers of the Naval Postgraduate School in Monterey, California.

Their findings are published in the Journal of Physical Oceanography.

Focal zone

Sandbanks and strong currents may cause waves to change direction and speed. This concentrates wave energy into a single point, which oceanographers call a "wave focal zone".

This zone is like a burning glass, Dr Janssen explained, where the light comes in and focuses all the energy on a single point, forming a hot spot.

The same happens when a wave travels over, for example, a sandbank, or over a current. The energy is being focused on to a single point.

The researchers found these hot spots were much more likely to drive the formation of extreme waves.

"In a normal wave field, on average, roughly three waves in every 10,000 are extreme waves," Dr Janssen explained.

"In a focal zone, this number could increase to about three in every 1,000 waves."

The scientists fed data on real waves into their computer model. Then, they repeated a single experiment over and over, each time using different data.

The SFSU oceanographer said he next hoped to go to known freak wave hotspots such as the Cortez Banks on the coast of California to test whether his simulations held true.

"What's really important about this research, is that it is easy to validate. We have a theory now, a prediction, and we can go to areas and actually measure whether this happens or not," he told BBC News.

Vital knowledge

Understanding where and when freak waves are most likely to occur could assist shipping and navigation in coastal areas.

The knowledge could be used for marine weather forecasts and could also inform the design of offshore platforms.

"If you know that a certain area is very prone to freak waves, then you might wish to stay away from it," Dr Janssen said.

"Anybody out in the ocean would like to [have this information]."

However, Dr Janssen was keen to stress that the study is theoretical.

"We have tried to be as realistic as we could, but we are a long way away from making a prediction solid enough for people to actually use. However, it might be something to work towards," he said.

Dr Janssen added that the word "freak wave" was unfortunate, as it suggests these types of wave are unexpected. But, he explained, the random nature of ocean waves means that any size of wave can happen at any time.



news.bbc.co.uk/1/hi/sci/tech/8188550.stm