Cruise-Ship Disaster: How Do 'Rogue Waves' Work?

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1 Cruise-Ship Disaster: How Do 'Rogue Waves' Work? By Bryan Walsh Thursday, Mar. 04, 2010 Manu Fernandez / AP Workers clean up broken windows on the cruise ship Louis Majesty, anchored at the port in Barcelona It was like something out of a Hollywood disaster movie. On March 3, a sudden wall of water hit a cruise ship sailing in the Mediterranean Sea off the northeastern coast of Spain, killing two people, injuring 14 and causing severe damage to the vessel. According to Louis Cruise Lines, the owner of the vessel, the Louis Majesty was hit by three "abnormally high" waves, each more than 33 ft. (10 m) high, striking in clear weather and without warning. "We heard a loud noise, and it was the wave that hit us," Claudine Armand, a passenger from France, told the Associated Press Television News. "When we came out of [our room], we saw the wave had flooded everything." The Louis Majesty wasn't hit by a sudden storm or any of the other expected dangers of maritime travel. Rather, it may have been the victim of rogue waves. For centuries mariners have told stories about sudden waves that would emerge out of the open ocean without warning, strong enough to topple even large ships. The S.S. Waratah, which vanished on a journey to Cape Town; the M.S.München, lost en route to Savannah, Ga.; even the S.S. Edmund Fitzgerald, "the good ship and true" of the Gordon Lightfoot song, which disappeared on Lake Superior all were rumored to have been sunk by rogue waves. Until recently, however, marine scientists dismissed the idea of rogue waves as little more than a sailors' fantasy, with reason there was little evidence to back it up. But in 1995, an oil rig in the North Sea recorded an 84-ft.-high (25.6 m) wave that appeared out of nowhere, and in 2000, a British oceanographic vessel recorded a 95-ft.-high (29 m) wave off the coast of Scotland. In 2004, scientists from the European Space Agency (ESA), as part of the MaxWave project, used satellite data to show that freak waves higher than 10 stories were rare but did occur on the oceans. Scientists still don't know exactly how rogue waves occur, nor do they know how to predict them. Open ocean waves, possibly including rogue waves, form when wind produces distortion over the surface of the sea the stronger the wind, the higher the wave, which is why hurricanes can create such destructive walls of water. Tsunamis, on the other hand, like the one produced by the 8.8-magnitude earthquake in coastal Chile on Feb. 27, don't create rogue waves; tsunamis barely make a ripple on the open ocean and gather in size only when they reach shallow land near a coastline. Rogue waves generally occur out in the open ocean. They may be the result of a number of factors coming together strong winds and fast currents coinciding, for instance or of a focusing effect, in which several smaller waves join together to form one big wave. There may even be a nonlinear effect at work, in which just a small change in wind speed multiplies to form a big wave. And certain areas of the ocean, like the strong waters off Africa's coast, may be more vulnerable to rogue waves than others.

2 Creating artificial rogue waves in a laboratory has always been a challenge. But in 2009, scientists from Harvard University and Tulane University examined patterns of microwaves, rather than water waves, to get a better sense of how rogues might arise. They created a metal platform in a lab measuring 26 cm by 36 cm (about 10 in. by 14 in.) and randomly placed 60 small brass cones on the platform to mimic the effect of unexpected ocean eddies in the current. When they beamed microwaves at the platform, the scientists found that "hot spots" the microwave equivalent of rogue waves appeared up to 100 times more often than standard wave theory would predict. Those results indicate that rogue waves might be a lot more common than scientists had believed and could explain why so many large ships as many as two a week sink even in the absence of bad weather. One day we might even be able to predict when these earthquakes of the sea occur sparing future cruisegoers the trauma suffered by those on the Louis Majesty. Questions: Answer on your own paper in complete sentences (or copy the question): 1. What happened to the Louis Majesty? 2. Why were rogue waves thought to be folklore? 3. Describe the circumstances of the first recorded incident. 4. How have satellites been used? 5. Can hurricanes produce rogue waves? Can tsunamis create rogue waves? 6. Where are rogue waves most common? 7. What did scientists use to recreate rogue waves? 8. What did their findings suggest? Rogue wave ahead New prediction tool gives 2-3 minute warning of incoming rogue waves. Sailing history is rife with tales of monster-sized rogue waves huge, towering walls of water that seemingly rise up from nothing to dwarf, then deluge, vessel and crew. Rogue waves can measure eight times higher than the surrounding seas and can strike in otherwise calm waters, with virtually no warning. Now a prediction tool developed by MIT engineers may give sailors a 2-3 minute warning of an incoming rogue wave, providing them with enough time to shut down essential operations on a ship or offshore platform. The tool, in the form of an algorithm, sifts through data from surrounding waves to spot clusters of waves that may develop into a rogue wave. Depending on a wave group s length and height, the algorithm computes a probability that the group will turn into a rogue wave within the next few minutes. It s precise in the sense that it s telling us very accurately the location and the time that this rare event will happen, says Themis Sapsis, the American Bureau of Shipping Career Development Assistant Professor of Mechanical Engineering at MIT. We have a range of possibilities, and we can say that this will be a dangerous wave, and you d better do something. That s really all you need. Sapsis and former postdoc Will Cousins have published their results this week in the Journal of Fluid Mechanics. See how MIT engineers developed a prediction tool that could give sailors a 2-3 minute warning of an incoming rogue wave. Not just bad luck Like many complex systems, the open ocean can be represented as a chaotic mix of constantly changing data points. To understand and predict rare events such as rogue waves, scientists have typically taken a leave-no-wave-behind approach, in which they try to simulate every individual wave in a given body of water, to give a high-resolution picture of the sea state, as well as any suspicious, rogue-like activity. This extremely detailed approach is also computationally expensive, as it requires a cluster of computers to solve equations for each and every wave, and their interactions with surrounding waves.

3 It s accurate, but it s extremely slow you cannot run these computations on your laptop, Sapsis says. There s no way to predict rogue waves practically. That s the gap we re trying to address. Sapsis and Cousins devised a much simpler, faster way to predict rogue waves, given data on the surrounding wave field. In previous work, the team identified one mechanism by which rogue waves form in unidirectional wave fields. They observed that, while the open ocean consists of many waves, most of which move independently of each other, some waves cluster together in a single wave group, rolling through the ocean together. Certain wave groups, they found, end up focusing or exchanging energy in a way that eventually leads to an extreme rogue wave. These waves really talk to each other, Sapsis says. They interact and exchange energy. It s not just bad luck. It s the dynamics that create this phenomenon. Going rogue In their current work, the researchers sought to identify precursors, or patterns in those wave groups that ultimately end up as rogue waves. To do this, they combined ocean wave data available from measurements taken by ocean buoys, with nonlinear analysis of the underlying water wave equations. Sapsis and Cousins used the statistical data to quantify the range of wave possibilities, for a given body of water. They then developed a novel approach to analyze the nonlinear dynamics of the system and predict which wave groups will evolve into extreme rogue waves. They were able to predict which groups turned rogue, based on two parameters: a wave group s length and height. The combination of statistics and dynamics helped the team identify the length-scale of a critical wave group, which has the highest likelihood of evolving into a rogue wave. Using this, the team derived a simple algorithm to predict a rogue wave based on incoming data. By tracking the energy of the surrounding wave field over this length-scale, they could immediately calculate the probability of a rogue wave developing. Using data and equations, we ve determined for any given sea state the wave groups that can evolve into rogue waves, Sapsis says. Of those, we only observe the ones with the highest probability of turning into a rare event. That s extremely efficient to do. Sapsis says the team s algorithm is able to predict rogue waves several minutes before they fully develop. To put the algorithm into practice, he says ships and offshore platforms will have to utilize high-resolution scanning technologies such as LIDAR and radar to measure the surrounding waves. If we know the wave field, we can identify immediately what would be the critical length scale that one has to observe, and then identify spatial regions with high probability for a rare event, Sapsis says. If you are performing operations on an aircraft carrier or offshore platform, this is extremely important. The approach is original it is fast, easy to implement, and it does not require computational power, says Miguel Onorato, professor of physics at the University of Turin, who was not involved in the research. Tests in wave basins and field measurements data are needed in order to establish reliability of the tool in realistic conditions. This research was supported in part by the Office of Naval Research, the Army Research Office, and the American Bureau of Shipping. Questions: Answer on your own paper in complete sentences (or copy the question): 1. What have scientists at MIT recently developed? 2. How does it work? 3. Why have past simulation systems not been effective? 4. What two parameters did they use to predict rogue waves? 5. What technology does their algorithm rely on? 6. Is the technique well tested yet?

4 The Wave That Changed Science Over the centuries many sailors described seeing huge ocean waves, monsters of the seas that towered to heights of 30 meters and more. Those Rogue Waves, as they were called, appeared suddenly and rammed into the unfortunate vessel. Scientists tended to ignore these stories. They considered them to be legends, fairy tales that sailors tell each other to pass the time on long journeys. They had good reason to doubt these stories: contemporary mathematical models predicted that the biggest possible ocean storm wave could be twelve to fifteen meters high. But those tales, passed from one sailor to another in pubs or late at night on the ship s bridge, told also of a massive hole in the water, tens of meters deep. This hole was followed by a nearly-vertical wall of water a wave so steep no ship could climb it. According to the stories, when a ship was hit by such a wave it usually drowned within seconds. Historical image of a possible Rouge Wave (Credit: NOAA Photo Library) For a long time, scientists thought their understanding of ocean waves was reasonably good. The way they saw it, the mathematical models that were developed for other kinds of waves, like sound waves and electromagnetic waves, could be applied to waves in the ocean. And why should these models not be appropriate? A wave is just a wave, after all an interference making its way from point A to point B, energy being transported from one place to another. Based on these mathematical models, scientists believed a thirty meter may exist, but is likely to occur only once every thirty-thousand years. Thus, Rogue Waves reports were placed in the same category sea-dragon stories, Bermuda Triangle oddities, and mermaid tales. Munich was ever found. A single wave that crashed on a tall oil-rig in the northern Atlantic Ocean shocked the foundations of these scientific models. In 1978, the merchant ship Munich set sail on a regular voyage across the Atlantic Ocean, transporting goods from Germany to the United States. The Munich was the jewel in the German merchant fleet s crown; it was over two hundred meters long and equipped with the best technology money could buy. No storm or hurricane could possibly harm the Munich. At 3 A.M, on December 12 th, 1978, a Greek ship received an S.O.S message from the Munich. An emergency task force of almost a hundred ships and planes combed the Atlantic, but no trace of the The Munich s disappearance was a great mystery. The weather had been rough, but should not have posed any serious danger to the large vessel. The matter became even more mysterious when the search party located an empty life boat that had belonged to the Munich, floating in the water. Bent and broken pins on the life boat s side indicated that the boat was not purposefully lowered to from the ship by the Munich s crew, but was thrown over-board as a result of a massive impact. However, the Munich s life boats usually hanged twenty meters above the water s surface! What tremendous force could have reached that height, knocking the raft out of place and possibly sinking the entire ship? The formal investigation team concluded that the Munich drowned as a result of an unknown weather-related event, but many suspected that a Rogue Wave was the real culprit. Since no proof was available, this view was never adopted by the authorities. This all changed on New Year s Eve, The Draupner oil rig (Credit: Garve Scott-Lodge) The North Sea, off the coast of Norway, was angry that day, my friends. Hurricanestrong winds were blowing and twelve meter waves crashed on the Draupner oil rig. The rig s workers were not worried, because the rig was designed to withstand hurricanes. At roughly 3 p.m. that afternoon, the order was given that all personnel must enter the rig s structure- no one volunteered to stay outside and watch the ocean. For this reason, no one saw the monstrous wave that hit the Draupner oil rig at 3:20 pm. The wave did not harm the rig itself (the platform was high above the water), but was recorded by a special laser-based wave-height detector. The rig s engineers

5 were shocked when they went over the detector s logs. The wave was almost 20 meters high. It was practically impossible- this kind of wave should only occur once every ten thousand years. Yet the laser detector was accurate to within an inch and worked flawlessly. The wave s existence was undeniable. Where then did the Draupner Wave, as it came to be known, come from? It could not have been a Tsunami wave, since Tsunami waves grow large only when approaching land. It could not have been a Tidal Bore, a wave caused by tidal forces, since these only occur near the shore and are a much more localized phenomena. It became obvious that a new theory must be developed to explain Rogue Waves. The first stage of every theory development is searching for facts. When the researchers looked back at all the data collected from sea buoys and ocean-waves radars, they were amazed at what they found. Instead of one report of a giant wave every thirty thousand years, Rogue Waves seemed to occur very often. Why, then, did ships encounter them only rarely? The answer was obvious- Rogue Waves exist for several minutes only, and disappear almost as soon as they are formed. It was now also possible to open the history books and re-examine past mysteries in the light of the new knowledge. One such historical enigma is the Flannen Island Mystery; In 1899, a new lighthouse was built on a remote group of islands off the coast of Scotland, some 20 miles from the mainland. Three light house keepers were stationed at the lighthouse, and cared for the structure. A year after the light house was erected, a supply ship came to the islands- as it did every week- to replenish the keepers food supply. The ship s crew found the light house was empty. Its three keepers had vanished almost without a trace. Upon examining the scene, the ship s crew found that coats had been left behind, and a chair had fallen in the kitchen. These were considered as clues that hinted to a sudden catastrophe. An examination of the lighthouse itself revealed damage to a metal box some thirty meters above the water s surface, a railing that was bent beyond repair, and a huge rock that was somehow moved from its place. The official examiner speculated that a giant wave had hit the lighthouse- but since it was considered impossible that a wave this size might exist, alternative theories were invented to explain the men s sudden disappearance. Some speculated a fight had broken out between the keepers, others suggested murder, suicide, abduction by foreign agents, and even abduction by alienseverything was possible. It is now believed that two of the keepers were working near the water, when the third spotted a Rogue Wave approaching the island. He ran outside to warn the others, not stopping to pick up the fallen chair or take his coat with him, but the monstrous wave washed all three. RMS Queen Mary Arriving in New York Harbor, 1945, with thousands of U.S. troops (Credit: National Archives and Records Administration) A different, even more famous case involved the Queen Mary, a giant passenger ship. During the second world-war it was used to transport troops from the U.S. to Europe. In December 1942, with sixteen-thousand soldiers on board, it was hit by a huge wave. This monster wave, almost thirty meters high, crashed into the ship side and caused it to reach a 52 degrees tilt. The ship slowly straightened, and barely managed to sail back to harbor. The engineers who examined the damage remarked that had the ship tilted by just three more degrees it would have capsized, killing everyone on board. This incident had the potential to end so tragically that it would have made the Titanic disaster seem negligible. Using satellite imagery, it became obvious the there are certain areas around the globe that are more prone to Rogue Wave activity. Places where ocean currents meet waves that travel at opposite directions are especially dangerous. Those areas were quickly removed from shipping lanes listings. But Rogue Waves occur in other places as well, places that have no strong currents or high waves. Today, the scientists opinions remain divided as to the source of these waves. Generally speaking, two kinds of theories are competing for supremacy: linear theories versus non-linear theories. Linear theories explain Rogue Waves as the additive sum of two smaller waves: that is, when a ten meters high wave climbs upon another ten meter high wave, we get a single monster wave that reaches a height of twenty meters. For example, it is well know that high frequency waves travel slower over the ocean than low frequency waves. It is possible for a slow frequency series of waves to chase and overtake a higher frequency group of waves, and climb over them.

6 Critics of the linear theories say that these theories can only explain how under a very specific set of circumstances a Rogue Wave is produced. These are circumstances that occur very rarely, and can not account for the high number of Rogue Waves that have been reported over the years. Non-linear theories take a very different approach. They try to explain Rogue Waves using equations and ideas taken from quantum mechanics. Schrodinger s Equation, for example, is a famous equation used to explain and predict the behavior of electrons in orbit around the atom s nucleus. It does so by treating the electrons as waves traveling around the atom. A version of this equation, known as the Non-Linear Schrodinger Equation, is highly effective when used in optics, and as it turns out- in explaining Rogue Waves. According to this equation, an ocean wave might start to suck energy from nearby waves, gaining height at the expense of the surrounding waves. This could account for the hole in the water phenomenon reported by sailors who survived encounters with Rogue Waves. As mentioned above, all Rogue Wave theories are still very much a work in progress. Technological advances might have given us the impression that we have managed to tame the sea, that our huge ships and sophisticated radars have made the voyage over the ocean safe, almost boring. However, nature proves time and again that we are neither as smart nor strong as we like to think we are. At least for the near future, sailors still need to keep their binoculars close at hand, and should keep scanning the horizon for Rogue Waves, and maybe for other sea monsters science has yet to recognize. About the author: Ran Levi has a B.Sc in Electrical Engineering from the Technion- Israel Institute of Technology. He has published a book about the history of Perpetual Motion Machines, and writes about various scientific and technological issues. Questions: Answer on your own paper in complete sentences (or copy the question): 1. What events or locations does the author say rogue waves were compared to? 2. Describe what happened to the Munich. 3. What was special about the Draupner Oil Rig? 4. What two events were considered for the Draupner wave before rogue waves were decided upon? Why are these not viable options? 5. What is the Flannen Island Mystery? 6. Describe what the Queen Mary was, and what amazing event occurred. 7. Describe in detail linear theories and non-linear theories and why both are disputed. Choose one: A. Some scientists believe that rogue waves may explain mysterious ship disappearances, such as those that may occur in the Bermuda Triangle. Write a news article about what rogue waves are, how they may form, and whether or not you support this theory of the Bermuda Triangle being a rogue wave hot spot. Include scientific details from these articles, and if available, research the topic yourself on your device and include this information to support your viewpoint. B. Create a comic book spread about rogue waves, using sailors or pirates talking on the dock about these incredible waves, where one is explaining to another how rogue waves form and why they are rare. You should include details from one of the ships in this article to prove your point to the disbelieving friend. C. Using a few sheets of folded paper, create a book for children to teach them about rogue waves, how they form, what research is being done to study them. Use lots of pictures and color!