Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 164
Extreme Waves 8 A Confused Sea When you are on a long passage in the open ocean, you will find that a certain rhythm is established. The motion of the vessel, repeated hundreds of times every hour, becomes a ballet that sailors sense almost without thinking. It guides their movements along the deck or within the cabin. They know instinctively when to lean to the starboard because in a moment the boat will roll to the port side and so on. This ballet of movement is accompanied by a symphony of sounds—the sound of the rigging, the creaking and groaning of mast stays, the sloshing sound of water passing the hull; all become part of a familiar melody. My senses become finely tuned to sound and movement. At night, asleep in Dreams when someone else is on watch, if the roll of the boat shifts slightly, or if a certain sound changes pitch or a “clunk” becomes a “clink,” I find myself instantly awake, asking myself, “What changed?” Indeed, what changed may have been a slight shift in the wind that will be adjusted for by the wind vane that steers the boat effortlessly as we stand watch, or it may have been a subtle change in the wave patterns as Dreams’ course intersects a new set of swells and the boat’s motion establishes a new equilibrium.
OCR for page 165
Extreme Waves At any point in time the sea condition is a reflection of every storm and disturbance that has occurred within the past few weeks. Distant storms may have churned the ocean 1,000 nautical miles away from your position; a day and a half later the first swells from that storm reach the spot where you sail. For example, sailing northwest in the direction of the oncoming swell, you are likely to encounter higher waves as time passes, until finally the size of the waves once again diminishes as the last waves of that particular storm pass under the hull of the boat. Now suppose that at the same time, the wind begins to freshen in the northeast, signaling the arrival of a nearby storm or squall. All afternoon the wind from the northeast builds, soon reaching the point at which you reduce sail to just the mainsail with one reef. Soon you are sailing at 7 knots, making good progress to a distant port; meanwhile the squall has pretty much blown itself out. What of the seas at this point? Looking at the waves, it is difficult to discern a single pattern or uniformity. Instead, superimposed on the swell coming from the northwest are smaller waves from the local storm. Although the wind was out of the northeast, and thus at a right angle to the direction in which you were sailing, the storm waves do not line up downwind. Instead, wave trains arrive at various angles to the direction of the wind—some piling up on top of the swell, some opposing it, and some hitting it at an angle. The combined effect is to give the sea a chaotic appearance—any singular pattern of wave motion is difficult to perceive. Being close to the local storm, dispersion had little effect and the waves reaching the boat had many different wavelengths. Another way of stating this is that the “sea” has a wide bandwidth spectrum (meaning waves of many different frequencies) compared to swell, which has a narrow bandwidth (because of the filtering effect of dispersion). You might ask, “What is the significant wave height under these conditions?” Trying to determine how high the waves are in chaotic seas might seem to be nearly impossible, but weather forecasters have devised methods, based on the randomness of chaotic seas, that they use.1
OCR for page 166
Extreme Waves The chaotic nature of actual seas is also influenced by the vicinity of coasts or islands or by areas where the ocean depth changes significantly, such as near a continental shelf. Here additional phenomena cause wave interactions. As waves approach the shore, they slow down in shallow water. If the wavelength is long relative to the depth, the front crest (in shallower water) will travel at a slower speed than the distant following crest (remember that in shallow water, wave speed depends on depth). In shallow water, the crests also become higher. When a wave train reaches the coast or an island, a portion of the energy is lost as the waves break and a portion is reflected back in the form of new waves. Other phenomena can change the direction of the waves, causing them to meet and interact with the incoming waves. This interaction, which is discussed in Chapter 3, can result in constructive or destructive interference and inevitably produces more complex wave patterns. WAVE INTERACTIONS Waves can be reflected, refracted, or diffracted. Reflection, refraction, and diffraction are common to other energy forms exhibiting wavelike behavior, including light and sound. In the open ocean, which is constantly traversed by long-wavelength waves, islands and continents are barriers that reflect and refract waves. In the absence of storms or other unusual conditions, the wave patterns near these obstacles remain relatively constant throughout the seasons. To visualize this pattern, picture a small boulder in the middle of a rapidly flowing brook. The stream flow is both reflected from the upstream side of the obstacle and refracted around it. Since the water close to the boulder travels a longer distance, it has to speed up in comparison to the water closer to the bank. Downstream from the rock, the currents merge and once again move uniformly. Immediately downstream from the boulder is a spot of calm water, where the current eddies past the boulder. If the flow is smooth enough, various wave patterns can be seen radiating from the boulder. Now shift your imagination to the vast expanses of the ocean and picture an island as an obstruction to the prevailing currents and swell.
OCR for page 167
Extreme Waves In an analogous manner, the patterns of waves reflecting and refracting from the island can be observed. For example, as I sail Dreams northwest around the east end of Catalina Island, I encounter the predominant west swell “on the nose” as sailors put it, where it refracts around the end of the island. Close in, in the lee of the east end of the island, there is little wave activity, while farther out there are confused interacting wave crests as the wave trains that have traveled down each side of the island cross over each other. On the west end of the island, the incident westerly swell surges against the island cliffs in some places, breaks against rocky shores in others, and then reflects back into the oncoming waves and creates a choppy and confused sea. REFLECTION Consider the simplest case first. Waves approach a shear, straight cliff that drops deep into the ocean. Since the water at the face of the cliff is very deep, the waves do not break; they surge up against it and are reflected back. If the cliff is long and straight, and the waves approach in a perpendicular direction, a pattern of standing waves could be set up. However, this is unlikely; it is more realistic to assume that the waves strike the cliff at some angle and are reflected back at an equal but opposite angle. Now consider the other extreme: a sloping beach. Here waves approach the beach, slowing down as the water becomes shallower, the wavelength diminishing, and the wave crest becoming higher and higher until the wave either becomes unstable and breaks or surges up on the beach and reflects back into the sea. If the wave breaks, much of its energy is expended and reflection may be small or nonexistent. REFRACTION Refraction is the process by which light or other energy forms are deflected by passing through the interface of two media having different densities or by passing through a medium with varying density. A simple example with which we are all familiar is a stick held in a pool of clear water (imagine trying to spear a fish). Here the media are air
OCR for page 168
Extreme Waves and water; as you look into the water the stick appears to bend because light is refracted at the interface between the air and the denser water medium. This is because the speed of light in air is greater than in water. In an analogous manner, ocean waves are refracted as the ocean depth shoals (becomes shallower) and the waves slow down as explained previously. This explains a common phenomenon that puzzled me until I began studying waves. The coast of Southern California takes the shape of a large arc, curving southeasterly from Point Conception (a short distance north of Santa Barbara) to the Mexican border. Along the coast are numerous bays and other irregular features, including beaches that face in directions ranging from northwest to west or south. As mentioned above, the predominant swell is from the west or northwest—although storms in Mexico occasionally will create a strong southerly swell. Yet go to any of the beaches along the coast and the direction of the waves as they come rolling in to break on the beach is perpendicular to shore. How can this be? As waves approach the shore at an angle, that part of the wave closest to shore will “feel” the shallow bottom first and begin to slow, so its angle of incidence changes. As the rest of the wave gradually passes that same depth, it too slows. This process repeats again and again as the water becomes shallower and shallower, effectively altering the wave direction until the waves are perpendicular to the shore and once again are all moving at the same speed and in the same direction. Coastlines on the mainland or on islands are more often irregular, featuring coves and bays or capes and headlands jutting into the sea. Consider first a canyon that can be seen onshore and extends out into the sea, forming a bay at the coast and an underwater canyon or deeper area immediately offshore. In this case, refraction causes the incoming waves to spread out, or diverge, and the wave intensity into the bay is reduced. It is the opposite situation in the case of a cape or point. Here, if the land projects out into the ocean and the sea is shallower than the surrounding area, the waves will be focused on the cape or point and are said to converge at that location. This helps explain why ships seek safety in bays but run aground on capes and points during storms. Refraction is an important consideration in harbor design. De-
OCR for page 169
Extreme Waves pending on bottom conditions and the geometry of the harbor entrance, refraction can cause waves to dissipate energy and be smaller in the harbor. Or, under certain conditions, refraction can focus wave energy into the harbor, creating larger waves. Through refraction, the narrow opening of a harbor can concentrate waves within a confined space. For this reason, understanding the prevailing local conditions of wind direction, current, wave periods, and wavelengths is extremely important to harbor design. With good design and the right dimensions, a harbor can be designed to attenuate incoming waves and produce calm waters. If prevailing conditions are not understood and considered in harbor design, exactly the opposite can occur; waves inside the harbor are larger than those outside. As another example, refraction causes waves to focus and become higher as they approach a submarine ridge, but to defocus and spread over a submarine valley.2 For similar reasons, entering any harbor can be tricky when big seas are running. Storms can alter conditions at harbor entrances in a matter of days or sometimes hours, moving sand and creating shoals—and atypical waves can toss an unwary vessel sideways. DIFFRACTION Diffraction is the spreading or focusing of waves by a narrow aperture or the edge of an obstacle. If waves impinge on a narrow channel such as the mouth of a harbor or a breakwater, diffraction occurs. Diffraction can cause some wave energy to propagate in a direction perpendicular to the direction of the waves. For example, a cape or point jutting out from the coast will diffract the incident waves, causing them to change direction and “bend” around the point, as shown in Figure 17. This sketch is a view of the entrance to Newport Harbor as I observed it one morning from a plane taking off from the Orange County Airport. The prevailing westerly swell can be seen approaching from the right. As it impacts on the west breakwater, it bends to the northeast, in the direction of Little Corona Cove. Some of the diffracted waves bend around and roll into the main channel between the breakwaters. A similar effect takes place when waves hit a gap in a harbor break-
OCR for page 170
Extreme Waves FIGURE 17 Wave diffraction, Newport Harbor entrance. water. Within the harbor, the incoming waves are diffracted to both sides of the gap. These waves in turn can interfere with both incoming and reflected waves, producing very complex wave patterns. It is possible that under certain conditions, substantial wave action can take place within the harbor behind the breakwater. Even though making landfall in rough seas can be hazardous, that is not the main focus of this chapter. As storms arise in distant parts of the ocean, their waves disperse and eventually impact landmasses or islands. The reflected or refracted waves from these distant storms create complex wave patterns, often superimposed on the dominant swell for that area. POLYNESIAN NAVIGATION BY WAVE PATTERNS The early Polynesian navigators discovered that there were repetitive patterns in the confused seas they experienced as they ventured from island to island. They saw that swell in the Pacific followed predictable paths, depending on the time of year. When one of the prevailing swells struck an island, certain wave patterns were established in a manner analogous to the boulder in the center of a rapidly moving stream described above.
OCR for page 171
Extreme Waves The navigational capabilities of Polynesian sailors became apparent at the time of Captain James Cook’s first voyage. In his July 13, 1769, entry in his sea journal, Cook relates that he was able to convince a priest and navigator named Tupia to accompany him on the continuation of his voyage when he sailed away from Matavai Bay, Tahiti.3 From his experiences with Tupia, Cook concluded that the Polynesians were fully capable of sailing from one island to another, for a distance of several hundred leagues (more than 600 nautical miles.) Over a period of time, Polynesians populated a vast area of the Pacific Ocean, more than 4,800 nautical miles long and 3,600 nautical miles wide. In most cases, they did it on island-hopping journeys of 50 to 200 nautical miles. How did they do it? How did they manage to avoid deadly reefs and make accurate landfalls on remote islands without benefit of compass, chart, or sextant? In the 1900s it became apparent that some navigators who knew the ancient techniques were still alive, but they were the last of a small group that was slowly dying off. In 1965, while circumnavigating the world in a 40-foot catamaran, sailor David Lewis learned the rudiments of their techniques and then successfully sailed from Tahiti to New Zealand, a distance of around 2,200 nautical miles, without using navigation instruments.4 About 15 years later, after conducting some preliminary research, a young sailor, Steve Thomas, took passage to Satawal Island in the Caroline Island group, where he succeeded in apprenticing himself to a navigator named Mau Piailug. Thomas lived as a member of Piailug’s family, learned the navigational techniques that had been handed down orally from generation to generation, and documented them. Modern navigation uses the compass to establish heading (direction of travel), charts to locate the position of the vessel relative to its destination, and instruments such as chronometers, sextants, loran, or global positioning satellites to “fix” (determine) the position of the vessel. In the Polynesian system, an initial heading was established by back-sighting landmarks on the departure island; from this, an estimate of the set of the current could be made and the course adjusted
OCR for page 172
Extreme Waves appropriately. By lengthy training and memorization, the navigator learned the positions of 32 prominent rising or setting stars, arranged in a manner analogous to the points of a compass. During the night the vessel was steered in the direction of a star known to rise over the destination island. Once this star had risen too high above the horizon to be useful for steering, the navigator steered to a second star that rose in the same direction, or to an alternate star that was “offcourse” a known amount, for which the heading of the vessel was adjusted. The rising and setting stars constitute a type of star map. Thus Polaris marks north, rising Little Dipper (Ursae Minoris) marks roughly 15 degrees; rising Big Dipper (Ursae Majoris), 27 degrees; rising Vega, 40 degrees. Similarly, setting Little Dipper marks roughly 345 degrees; setting Big Dipper, 333 degrees; setting Vega, 320 degrees. Other stars fill out the remaining points on the star map; the formal name for such a system is a sidereal compass.5 The Polynesian navigation method is unique in another respect. The navigator imagines that his vessel is fixed and the destination island “moves” into position under various stars, until the island reaches a position under the star that tells him he has arrived. Contrast this to today’s navigation method whereby a vessel is moving and the destination island is a fixed point toward which the vessel moves. During daylight, when no stars were visible, the navigator made use of the ocean swell to judge the heading of the vessel. Navigators were trained to recognize eight dominant swells. During the winter months, dominant swells came from the northeast or east under the influence of the trade winds. With a northerly heading and an east swell, the navigator knew the heading was correct if the vessel rocked. On an easterly course into an east swell, the vessel would pitch, bow rising and then falling as the vessel rode over the swells. To maintain a northwesterly heading, the navigator would adjust the sail and steering oar positions until the vessel responded with a combined pitching and rolling motion in the right proportions. The best way to do this, I’ve been told, is to lie flat on your back on the deck and look up at a cloud or star. The motion of the boat is easier to sense this way than staring at the horizon. To pass on the knowledge from generation to generation, naviga-
OCR for page 173
Extreme Waves tors constructed “charts” made of sticks laced together to illustrate the wave patterns, using shells to mark the positions of islands.6 Examples can be seen in the Bishop Museum, Honolulu, and in the Newport Harbor Nautical Museum, Newport Beach, California. The most skilled navigators could sense when they approached their destination by subtle shifts in the motion of their vessels as the wave pattern changed. They could recognize a number of different wave patterns; each was given a specific name. Considerable practice and skill are required to navigate in this manner. In addition, certain seagoing birds, known to frequent specific islands, would start appearing at distances of 20 to 30 nautical miles. Floating vegetation and even certain species of fish could also provide positive identification. Once, while on a fishing trip out from Midway Island, we left in the morning at dawn. Later in the day I happened to look back in the direction of the island. The low-lying island was now over the horizon and invisible, but its location was clearly evident by a turquoise-green color in the clouds above it. This was caused by sunlight reflecting the island and lagoon onto the clouds and could be seen at a great distance. Clouds are formed by moisture-laden warm air rising over islands. At other times, a bright column or glow can be seen on the horizon, due to the reflection of the sun or moon from shallow water or a lagoon; this is known as the loom of land. Because the Polynesians had no means of determining longitude, on longer voyages they usually sailed north or south to the approximate latitude of their destination. They watched zenith stars, or stars known to pass directly over the island to which they were steering. Once they came abreast of that position, they would tack and run downwind to their destination. In the 1970s, a group of Hawaiian researchers constructed the Hokule’a, a 60-foot-long replica of an ancient Polynesian double voyaging canoe. Hokule’a departed from Honolua, Maui, on May 1, 1976, and reached Papeete, Tahiti, 33 days later. The navigator on that trip was Mau Piailug, whom Stephen Thomas was later to meet and study under. Also on the crew were Ben Finney and Tommy Holmes, two of the cofounders of the Polynesian Voyaging Society; David Lewis, who had studied Polynesian navigation methods in the late 1960s; and 11
OCR for page 174
Extreme Waves other crew members. Under Piailug’s guidance, the 3,000-nautical-mile trip was accomplished without instruments. The voyage was significant because it established beyond question that the Polynesians, using the ancient methods of navigation, were able to explore and eventually settle vast expanses of the Pacific Ocean.7 After Hokule’a returned to Hawaii, there was strong interest in further explorations, and in 1978 Hokule’a set sail again. However, the vessel encountered rough weather almost immediately, and before leaving Hawaiian waters, a tragedy occurred. Through my brother, Ken Smith, a well-known water polo coach and educator in Hawaii, I was introduced to Marion Lyman-Mersereau, who told me about her experiences on Hokule’a. Marion: “We left near sundown on March 16, 1978, from Oahu. Our captain wanted to delay the departure because of the weather—heavy wind and seas—but was overruled. Hokule’a had rough seas crossing the Kaiwi Channel and by midnight was past Penguin Bank, somewhere off of Molokai, between Oahu and Lanai, on a southeast heading. Winds were gale force (35 to 40 knots) out of the northeast, impacting the port side of Hokule’a. Swells were running 6 to 8 feet. We became aware that the starboard hull was taking on water and Hokule’a was riding low on the starboard side. The captain rousted everyone to sit on the port hull to help balance the canoe. We also came off the wind so the crew could shorten sail. Before we could get the sail down we were hit by gusts of wind and a large wave and Hokule’a capsized. Besides me, the crew included our navigator, Nainoa Thompson, Eddie Aikau, and 13 others. I was the only woman. When we capsized, we scrambled back to hang on the upside-down hulls, consoling ourselves by saying that as soon as it became light someone would surely see us. “By the next day we were drifting farther away from the islands—both Molokai and Lanai could be seen in the distance—but no rescuers appeared. Several of the crew—including me—were sick and everyone was wet and tired. Later that morning Eddie volunteered to go for help on a surfboard. The officers gave their approval, as with his reputation and skill it seemed like our best hope at the time. He was asked to take a lifejacket; but later this came floating back, so no one knows if he ditched it intentionally or it was lost when something happened to him.
OCR for page 175
Extreme Waves “Eddie was never seen again after he paddled away from us that morning. It was a terrible tragedy. Everybody liked Eddie. He was well known, not just in Hawaii, but internationally, because of his surfing abilities. But he never lost his lifeguard instincts, from all those years of being a lifeguard at Waimea. He wanted to get help for us before the canoe was lost. As it was, we were in the water for 22 hours. Eventually Hokule’a was spotted by a passing Hawaiian Airlines pilot and coast guard helicopters picked us up that night. When the coast guard showed up we told them about Eddie and they launched an intense search for him. Some of the crew stayed with the Hokule’a until it could be towed back. It was salvaged and repaired and made many more trips for thousands of miles through Polynesia and Micronesia.” I happened to be in San Francisco in 1995 as part of a large welcoming crowd when Hokule’a sailed down from Seattle and passed under the Golden Gate Bridge. It was a very moving experience. By then, Hokule’a had sailed the equivalent of halfway around the world on its numerous trips to Polynesia. On several trips to Catalina Island in Dreams I charted the predominant swell that comes from the west and how it is modified by reflection, refraction, and diffraction around the island. From numerous trips I was aware of the swell but previously never paid attention to the subtler aspects of how the boat moved under its influence. Hearing about Hokule’a and Piailug, and listening to Lyman-Mersereau, kindled my interest. On the next trip I made to Avalon, Catalina Island, I closed the compass binnacle and tried to steer by keeping the swell at 45 degrees on my starboard bow. (The heading for Avalon from Newport is 225 degrees magnetic, so for a west swell I needed to subtract 45 degrees.) The island was obscured by early morning overcast skies. When it finally cleared a few hours later, I could see I was on course. Coming back was a different story. By then a south swell had set in and we had confused seas. As I looked astern, it seemed the waves came first from one direction and then another, and sometimes I could not determine from what direction they were coming! I could see that it would take considerable practice, along with the ability to sense the predominant swell, to become proficient at this method, especially over much longer distances. I have great respect for the Polynesian navigators thanks to my amateur experiments.
OCR for page 176
Extreme Waves SOLITARY WAVES A somewhat unusual phenomenon is the solitary wave that travels on the surface or beneath the surface of the sea. Such waves are called solitons. Originally, as in the case with other unusual marine phenomena, the existence of such waves was doubted. The advent of satellite observation of the oceans has provided evidence of their existence. As many as seven solitons have been captured by satellite photographs crossing the Andaman Sea at the same time. Today, because of the December 26, 2004, Andaman-Sumatra earthquake and tsunami, more people are aware of the Andaman Sea than before. It is a relatively shallow body of water lying east of the Andaman and Nicobar Islands and west of the Malay Peninsula. Theory has it that tidal currents squeezed between the islands generate internal (subsurface) solitons. As these propagate, they interact with the surface of the sea to produce a large number of randomly directed small waves, making the sea surface look as if it is boiling. The “boiling” sea appearance has also been photographed by a drill ship working in the area. On a much larger scale, on February 17, 1846, the harbor on the island of Saint Helena was suddenly violently agitated, causing the loss of 13 vessels. At distances of more than about 1,600 feet from shore, the water was calm. No one is sure how solitons arise in the open ocean. It may be that long-wavelength (faster-moving) waves overtake slower waves, canceling out a portion of them and creating a single wave group that is compact, higher, and long-lived. This resembles a pulse that approximates and propagates as a solitary wave.8 CONFUSED SEAS It is not uncommon to have more than one storm at a time in different parts of a sea. Also, any given storm is most likely moving. The net result of this is that multiple wave trains can be crossing the sea at a given location, intersecting at various angles with waves from other storms or with waves reflected or refracted from some distant shore. As mentioned earlier, these waves can interfere with each other. If the wavelengths are nearly equal and the waves are in phase or nearly in
OCR for page 177
Extreme Waves phase, they can combine and create a larger wave. Or, if the wavelength and phasing are just right, one wave can tend to cancel another. If they intersect at an angle, complex diamond-shaped wave patterns can be produced. Wave patterns lose all semblance of regularity, and instead become random and irregular. Under these circumstances with severe storm conditions and large waves, the seas seem to come at a boat from every angle, creating a chaotic situation as the helmsman tries to maneuver the boat. This condition is described (with a certain degree of understatement) as confused seas. Navigating in confused seas can be particularly harrowing in rough weather. Confused seas, combined with a rogue wave, created one of the most bizarre transatlantic passenger liner incidents I encountered in my research. The vessel was the SS Pennsylvania; she was barely a year old when the incident in question took place. The SS Pennsylvania was a football field long, at 336 feet, with a beam of 43 feet. She was equipped to carry both passengers and freight, and could accommodate 76 first-class passengers and more than 800 persons in “steerage class.” The period commencing with the winter of 1873 and continuing until the winter of 1874 saw a number of severe storms roil the North Atlantic steamship routes, causing the loss of 12 passenger ships. One of them, a White Star Line vessel appropriately named the Atlantic, went down with a loss of 585 lives on April Fools Day, 1873. One of the survivors was a man named Cornelius Brady, the third officer on the Atlantic.9 As the SS Pennsylvania prepared to sail on February 21, 1874, from Liverpool to Philadelphia, she carried only 12 steerage passengers and one first-class passenger. However, at the last minute a second first-class passenger boarded the vessel. Fortuitously, the last passenger happened to be Cornelius Brady. The SS Pennsylvania entered the Irish Sea, traveled southwest past the east coast of Ireland, through St. George’s Channel, and into the North Atlantic. After several days of steaming she encountered increasingly foul weather, culminating in a terrific hurricane that pounded the ship with heavy waves and confused seas. Heavy waves broke over the bow, damaging the front portion of the vessel and flooding the
OCR for page 178
Extreme Waves lower decks. Around midnight, a mountainous rogue wave swept over the vessel, demolishing the bridge, crushing the forward hatches, ripping loose and carrying away lifeboats, life rafts, much of the vessel’s superstructure, lifelines, stanchions, and rails—and the crew navigating the boat! All of those who had been on the bridge fighting the storm—the captain, first mate, second mate, and two crew—were lost overboard. But this fact was not known to the passengers and remainder of the crew, who were fighting for their lives belowdecks by trying to stop the flooding and by reinforcing the damaged portions of the vessel. The third officer—apparently paralyzed by fear—cringed belowdecks and would do nothing. At this point, Brady and a group of passengers and crew took it upon themselves to replace the damaged hatches with others from belowdecks to try to halt the influx of seawater. Brady sought the approval of the captain for this measure; at this time the loss of the bridge and all of the ship’s officers who had been on deck was discovered. Brady went on deck, saw the extent of the damage, and directed the crew to slow the vessel and heave to in a better position to ride out the storm. Brady secured a vote of confidence from the surviving crew members and the passengers, took charge of the vessel, and succeeded in bringing the SS Pennsylvania safely into Philadelphia—albeit six days late—where he was accorded a hero’s welcome. SURVIVAL STRATEGIES Under stormy conditions the helmsman’s goal is to keep enough way (forward movement) on the vessel so that a safe course can be maintained. (At very low speeds, the rudder has little effect, and steering the vessel becomes almost impossible.) There are several options, assuming there are no nearby rocky shores. The first is to “run” before the storm, or keep the wind and waves behind the vessel and go in the same direction as the waves. If this is not possible, the next choice is to slow down and head into the waves, taking them on the bow but at an angle to minimize slamming of the vessel as it rides up and over the wave. The third alternative is to “heave to,” which means to position the vessel so it remains nearly stationary in the water, with a slight sidewise motion.10
OCR for page 179
Extreme Waves With high winds and heavy seas, it is important to reduce the vessel’s speed and to maintain a safe course relative to the wave direction. If the speed is too high, there is a risk that the vessel will sail rapidly over the crest of a wave, bury its bow in the trough, and then flip end over end. This is known as pitchpoling and invariably results in damage to the vessel and its occupant, and possibly loss of the vessel. If a vessel is traveling too fast—even after reducing sails to a minimum—it becomes necessary to slow it by other means, including dragging long lines, called warps, behind the vessel (or in front of it if the goal is to keep the bow headed into the waves) or deploying a drogue (small parachute). These methods are collectively called sea anchors and are used to slow the vessel in high winds. In addition to slowing the vessel, they help the helmsman keep the vessel on the right heading so a large wave does not break broadside on the vessel and roll it over. Sea anchors work for yachts and smaller ships, but are impractical for commercial vessels. Any vessel is designed to be self-righting through a specific angle. A weighted keel or ballast in the hold of a vessel brings it back to a vertical position. However, once a critical angle of roll is exceeded, the restoring moment of the keel is ineffective, and the vessel can roll over completely. Under heavy seas the helmsman typically wants to maintain a course down seas at a slight angle to the waves. This way the vessel will ride up on the oncoming wave and slide down the crest (rather than nosedive straight down into the trough). The helmsman’s objective is to keep the big waves astern and not let the vessel turn sideways to the waves, resulting in broaching or rolling over. When the seas consist of swell from several distant storms, each wave train will, through dispersion, separate into a group of waves with a predominant period. When these waves come together, they will combine in a pattern that is determined by their respective wavelengths. The resultant composite wave will have a series of low crests where the waves interfered destructively, followed by several large ones where they did so constructively. These conditions create the wave “sets” familiar to surfers. With practice, the helmsman also can determine the rhythm of the waves, steering the desired course when the waves are smaller, and falling off the course when the large waves come, to avoid unnecessary pounding of the vessel.
OCR for page 180
Extreme Waves The helmsman of a vessel faces many hazards in heavy weather. In confused seas, life is much more difficult, because the vessel is likely to be battered and tossed from multiple directions, from time to time being buried under tons of water landing on the bow or in the cockpit. Under these conditions, the sturdiness of the vessel and how water-tight it is (windows and hatches) are as vital as the seamanship of the captain. Constant vigilance is required. Staying with the ship is usually the best idea, although not all would agree. One man in recent times carried the idea of “staying with the ship” to a remarkable extreme. STAYING THE COURSE Late in December 1951, the American cargo ship Flying Enterprise sailed from Hamburg, Germany, for New York. The Flying Enterprise was about 400 feet long and carried a cargo of pig iron, coffee, and other goods, as well as 10 passengers. Her master was Captain Henrik Kurt Carlsen, with more than 20 years of sea experience, including 40 Atlantic crossings. By Christmas day, the Flying Enterprise had passed through the North Sea, gone southwest down the English Channel, and entered the North Atlantic—just in time for one of the worst storms of the decade.11 The storm extended from Norway at the latitude of the Arctic Circle to Gibraltar in the south. A number of ships were lost in hurricane-force winds and seas that reached 40 to 60 feet, including the Norwegian tanker Osthav off the coast of Spain, the German ship Irene Oldendorff in the North Sea, and several others off the English coast. By the day after Christmas, the Flying Enterprise had progressed to a point about 300 nautical miles southwest of Ireland. At this point the weather was so threatening that Captain Carlsen decided to heave to and go with the storm until conditions improved. Early on the morning of December 27, Flying Enterprise was hit on the starboard side by a rogue wave more than 60 feet high. As the ship rolled to port under the impact, cargo shifted, the crew reported hearing the cracking sound of rending steel, and the vessel took on a heavy list to port. When the crew inspected the vessel, they found water flooding the number three hold and two cracks extending across the weather deck. The crew at-
OCR for page 181
Extreme Waves tempted to make emergency repairs but later that day the engines stopped and could not be restarted. Huge waves continued to batter the vessel and the Flying Enterprise listed 45 degrees. On December 28, Carlsen radioed for assistance; half a dozen vessels answered the SOS. However, it would be another day before they could reach the stricken ship. On December 29, as a number of vessels were standing by, he gave the order to abandon ship. The starboard lifeboat had been smashed to kindling by the rogue wave and the port lifeboat was unusable due to the list of the vessel, now around 50 degrees, so the only alternative was for passengers and crew to jump into the water, where they were picked up by lifeboats from the waiting vessels including the SS Southland and USNS General A. W. Greely. Captain Carlsen refused to leave the Flying Enterprise. The crew and passengers safely off and his vessel still afloat, he was determined to see her into port so the cargo could be salvaged. On December 30, he again radioed for assistance, this time seeking a seagoing tug to tow the Flying Enterprise to the nearest port. Thus began Carlsen’s incredible one-man fight against the sea, a modern Danish saga that would continue for another 12 days. Imagine trying to survive on a ship that constantly is being battered by waves, capable of sinking at any moment, with everything wet. Just trying to walk around with the decks at an angle of 50 degrees was a challenge. Half the time he’d be walking on the walls and bulkheads of the vessel! This was how Captain Carlsen welcomed in the New Year, still refusing entreaties from several ships now on the scene that he abandon the Flying Enterprise. “Not while she floats,” was his implicit answer. On January 3, 1952, the British deep-sea salvage tug Turmoil finally reached the Flying Enterprise. For two days, Carlsen tried to connect a towline, but in the rough seas, single-handedly, he was unable to do so. On January 5, the seas had calmed considerably, and Keith Dancy, the mate from Turmoil, had the tug brought close to the Flying Enterprise so he could make a daring leap onto its deck and help Carlsen attach the towline. With the towline finally attached and the seas moderate, the tug was able to make 3 knots toward the coast of England. Captain Carlsen
OCR for page 182
Extreme Waves finally had reason to be optimistic. The storm had blown the Flying Enterprise 200 nautical miles closer to England, and he now hoped that he could get the Flying Enterprise into Falmouth for salvage. For three more days they progressed—Carlsen and Dancy alone on the Flying Enterprise, the tug in front, the USS Willard Keith (DD775) now on the scene as an escort vessel. On January 7, the list was 70 degrees. On January 8, only 60 nautical miles from Falmouth, the weather once again deteriorated and Turmoil and Flying Enterprise heaved to in gale-force winds. Flying Enterprise was rolling up to 80 degrees. On January 9, the towline separated, but the weather continued to move the Flying Enterprise in an easterly direction. On January 10, only 40 miles from Falmouth, the two men on board observed unmistakable signs that the ship was going down. They walked along the ship’s funnel (now nearly horizontal), and stepped off into the sea—Carlsen, of course, being the last to leave. They were picked up within minutes by Turmoil, in time to watch the Flying Enterprise sink stern first into the sea. On January 11, when the Turmoil docked in Falmouth, Captain Carlsen was greeted as a hero by a crowd of thousands. He received numerous honors and awards, including a ticker-tape parade up Broadway when he returned to New York. But amid the attention, he remained modest and declined to capitalize on his accomplishment, stating that he didn’t think he was entitled to any special treatment, because “I failed to bring my ship back to port.” In truly bad weather, there are times when all you can do is hunker down and wait for the weather to abate. Tania Aebi sailed away from New York at age 18 in an 26-foot-long sloop to return two and a half years later in 1987 as the youngest woman ever to sail around the world single-handedly. On the last leg, after leaving Gibraltar to cross the Atlantic for home, her log book recorded her fear when she was hit by a sudden gale. Mountainous waves taller than the length of her boat engulfed her vessel from every angle, rolling it, tossing it forward, water breaking into, over, and all around the boat. On deck in the darkness as she struggled to reduce sail, she saw the silhouettes of gigantic waves bearing down on the boat like “freight trains.” Unable to watch any longer, she resigned herself to her fate and went below. To get her
OCR for page 183
Extreme Waves mind off the situation, she played solitaire while the boat basically sailed itself through rough and confused seas. Forty-eight hours later—her boat still afloat—the storm finally let up.12 Tania was fortunate that her small boat survived this onslaught of waves from every direction. The next chapter shows that even the mightiest ships are not immune to the danger of waves so large that they are best called extreme waves.
Representative terms from entire chapter: