Crazy dog waves of sea monsters
On November 1th, 1975, the American cargo ship Edmund Fitzgerald sank into the Lake Superior area between the United States and Canada in a storm. This cargo ship is no small thing. Its hull is 22 meters long and its width is 22 meters. It is definitely a monster. But it seems that the strong and safe freighter has not stood the test. When the disaster happened, the freighter lost its chance to survive before it could send out a distress signal. All the 22 crew members on board were killed, and their bodies have not been found yet.
According to the initial report of the US Coast Guard, the tragedy occurred due to the negligence of the crew and the failure to cover the hatch safety cover of the cargo ship's top cabin as required. This statement has always been controversial, and many colleagues said that the crew would not be so careless. In 21, diving detectives put forward another possible cause of disaster by exploring the underwater situation of the accident site-the cargo ship may have encountered a powerful "killing wave"-crazy dog wave. Perhaps, when the cargo ship was on the water, it was shot in half by this wave.
Lake Superior is the largest freshwater lake in the world, with an area of 82, square kilometers and a maximum depth of 45 meters, and its storage capacity accounts for more than half of the entire Great Lakes. On the vast lake, surges from all directions are fast and slow, pushing and competing with each other, and the energy accumulated underwater sometimes suddenly pushes up the surge. In addition, in winter, the wind and waves are sharp, and there is little ice on the lake in November, so it is more prone to sudden surges of big waves, resulting in crazy dog waves that make people smell pale.
However, it is extremely rare to have crazy dog waves in lakes, and "mad dogs" prefer to make waves at sea.
Is there a "killer wave"
Since ancient times, there have been legends about strange waves at sea, and Ernest shackleton, a legendary British explorer, described a thrilling experience of encountering a crazy dog wave. In 1916, he sailed from Elephant Island near Antarctica to South Georgia Island in the Atlantic Ocean. He described: "we were driven by the ups and downs of the waves and walked forward for several days, but one day, a huge wave with a thin momentum emerged from the surging waves." I've been praying that God can protect us and get us through this difficult time. The huge waves were heavily photographed, and our ship was shot down under the water. Under the impact of the surrounding current, the hull continued to tremble, but maybe God heard my prayer, and finally our ship actually escaped the disaster and carried us away from the strange waves on this sea. "
For the height of this crazy dog wave, those who have seen it can only describe it as "very high", and there is no specific data to prove how big the "strange wave" they described is. Therefore, in the past few centuries, people's impression of huge waves has only stayed in the "exaggerated" description of survivors, and scientists often disagree.
Until January 1st, 1995, the offshore oil platform in Draupna, off the coast of Norway in the North Sea, experienced a wave of 26 meters high, which was twice as high as other waves around it, and was about equivalent to a 1-storey building. This time, the laser equipment on the offshore oil platform measured the height of the huge waves, which was more accurate.
it was once thought that such an abnormal wave came once in a million years. However, in 21, Europe began to carry out the "big wave plan", using two satellites of the European Space Agency to study the state of the ocean. The satellites of the European Space Agency emit pulse signals of radio waves. When the radio waves reach the sea surface and then bounce back to the satellites, the collected information can be converted into the situation of the sea surface through complex algorithms. After that, the German earth observation satellite TerraSAR-X was also used for the research of mad dog waves, and its resolution can reach 1 meter, which is more accurate than the previous satellite data. In just three weeks, the "Big Wave Plan" found more than 1 huge waves with a wave height of more than 25 meters.
These specific figures obtained by scientific means make this kind of "talk about capital" that stays in legends and stories suddenly become a truly strange phenomenon, and scientists flock to discuss the formation mechanism of this crazy dog wave at major academic conferences.
Understanding the Crazy Dog Wave
Crazy Dog Wave is not only a common wave like the big wave in a storm, but actually much higher than all other waves around it, which is the visual effect of "standing out from the crowd" from a height. If defined by accurate scientific standards, the wave height of crazy dog waves is at least twice as high as that of meaningful waves (sea waves are actually irregular, and they are composed of waves with different wavelengths, wave heights and steepness. According to observation statistics, the wave height of 1/1 wave is twice the average wave height, which is called the maximum wave height. One-third of the wave height is 1.6 times of the average wave height, which is called trinity average wave height or meaningful wave height), so many high waves caused by tsunami or typhoon do not belong to crazy dog waves. Crazy dog waves often come unexpectedly, suddenly appear, suddenly disappear, come and go without a trace.
There are about 5 to 1 shipwrecks around the world every year. Of course, these are not all caused by crazy dog waves, but the phenomenon of crazy dog waves may help explain some mysterious accidents. Moreover, understanding the formation mechanism of this huge wave is helpful for human beings to make predictions, stay away from dangerous areas and reduce the occurrence of marine tragedies.
However, it is not easy to collect enough effective data. We can't reconstruct the historical information of Crazy Dog Wave, and only the wave height in the nearby sea area can be measured through the measurement of offshore platform. Moreover, the waves will move, and it is difficult to track the crazy dog waves once only for 1~2 minutes.
due to the lack of data, and the wave-making pool (equipment for simulating waves) can't simulate the mad dog waves, the only way to study this kind of waves is to put marine observation equipment in the sea area where mad dog waves may occur, and wait for the rabbit to collect relevant data when the mad dog waves appear. From this point of view, Cape Agules in South Africa is undoubtedly one of the best observation areas. The Indian Ocean and the Atlantic Ocean meet here, and the shipping channel is busy, and there have been many reports of big waves over 3 meters high here.
The "roaring westerly belt" from east to west passes through the waters near Cape Aguilar, pushing the waves to travel in the same direction, while the Aguilar current moves in the opposite direction. The impact of the ocean current and the waves raises the waves and causes huge waves.
crazy dog wave training
but not all the formation of crazy dog waves can be explained by the confrontation between these waves and strong ocean currents. According to the research on crazy dog waves for many years, scientists have given some conjectures that under the action of one or more factors, such a ghostly strange sea wave may be produced.
ocean current collision
it's not a good thing if the ocean current runs counter to the direction of the main body of the wave, as in the case of Cape Aguilar in South Africa. The ocean current pushed in the opposite direction will hinder the progress of the waves, reduce their speed and make the waves surge upward.
But the problem is by no means over here. The wave facing the ocean current in front slowed down first, but the wave behind did not slow down. The second wave hit the first wave, and the third wave hit the first two waves. In this way, under the obstruction of the reverse ocean current, a number of small waves will converge into a big wave, and several waves will be combined to move forward together. Finally, this wave is getting bigger and bigger, which may evolve into a huge strange sea wave.
In addition to reverse ocean currents, ocean currents in other directions will also bring together a number of small waves from all directions, which will spawn mad dog waves on the sea surface. However, because the velocity and direction of each solitary wave are different before the collision, and they still maintain the original velocity, waveform and direction after the collision, the huge wave can not continue to spread, and will soon disintegrate, and the sea will return to calm, as if nothing had ever happened.
the change of depth is the bane
if a wave originally moves in the deep sea area, but the seabed topography ahead is raised and the depth of the ocean becomes shallow, then the waves coming from the deep sea will suddenly be lifted up. Water is incompressible, so when waves rush from deeper waters to shallower waters, the only way to go is to push them up. In some areas along the east coast of the United States, the continental shelf extends far away, and the depth of the seabed will change sharply, which will lead to higher waves.
nonlinear irregular waves
As early as the early 196s, the physicist Brooke Benjamin of Cambridge University and his graduate student Jim Fell found that there were no regular waves in the wave-making pool, and some waves were always bigger than others. Even if regular wind is used to make waves, irregular waves are still obtained. In other words, there is no linear relationship between the input energy and the generated waves, but a chaotic nonlinear relationship. These unstable waves can get energy from other nearby waves and quickly form a huge crazy dog wave.
Tide adds fuel to the fire
Tide phenomenon is the periodic movement of seawater under the tidal force of celestial bodies (mainly the moon and the sun). Tides will change because of the position of celestial bodies. For example, when the sun, the moon and the earth are in a straight line at the full moon and the new moon, the tides will be even greater. When the moon reaches perigee, the spring tide will reach its peak, which is the perigee spring tide. This kind of regular fluctuation of waves may not fully explain the formation of crazy dog waves, but when the moon is near the moon and the spring tide is seen, if the sea waves are aroused for other reasons, the wave height will be higher and the power of the waves will be greater under the pull of huge tidal energy, and the superposition of other factors may turn into a crazy dog wave that is daunting.
Prediction of Crazy Dog Waves
The progress of modern remote sensing image technology also provides more detailed technical support for the study of Crazy Dog Waves. The wave height can be measured more accurately by radar data, and the separation and combination of these waves and ocean currents can be seen more clearly by current technology.
Using various technologies, scientists have worked together to develop a "big wave software" that can predict the crazy dog waves, which can accurately predict the abnormal changes within 8 kilometers around the ship in 36 degrees and give a warning through radar signals. In this way, the configuration of such equipment on the ship can actively monitor the surrounding waters and give the ship a buffer opportunity to avoid the crazy dog waves. However, since the occurrence of crazy dog waves is often very sudden and lasts for a short time, whether such early warning information can effectively reduce the occurrence of tragedies remains to be tested.
In the future, the ocean weather forecast may include crazy dog waves, but the occurrence of crazy dog waves is more often a random event, and the accuracy of the forecast may be difficult to guarantee. However, it is not a bad thing to have such a forecast to make people alert and prepare in advance.
this article comes from the magazine article "The Mystery of Big Technology * Science", No.12, 216. Welcome readers to pay attention to WeChat official account: hdkj1997.