Is there only waves on the sea? Waves and undulations on the ocean surface are common phenomena. These are waves, which are mainly surface waves formed due to the influence of wind. Generally, the wavelength of surface waves is about tens of meters, and the amplitude ranges from tens of centimeters to several meters. Only in extreme circumstances can stormy waves form.
In fact, as long as there is stratification in the fluid, the interface between flowing air and seawater will fluctuate. The ocean surface is the interface between the ocean and the air, which is naturally prone to fluctuations, which in turn forms waves. So what is the situation inside the ocean? As the depth increases and the temperature, salinity, and pressure of the seawater change, the density of the seawater gradually increases. Due to the difference in density from top to bottom, the seawater is divided into many layers, like a cocktail, but the hierarchical interfaces are not obvious. Atmospheric pressure, earthquakes, and even the movement of ships and submarines will cause disturbances to such layered seawater, resulting in fluctuations at the density layered interface. This is the internal wave in the depths of the ocean.
Although internal waves are not as obvious as waves on the surface of the ocean, they are hidden in the water and secretly cause trouble, making it difficult for people to prevent them, so they are called "underwater devils." While exploring the Arctic from 1893 to 1896, the explorer Frijjoff Nansen discovered that the scientific research ship would somehow slow down. After research, he understood that the ship triggered waves under the sea when sailing, which greatly consumed the ship's kinetic energy. As a result, internal waves deep in the ocean began to attract people's attention. In 1963, the USS Northtail Shark nuclear submarine incident made people realize the tremendous power of internal waves. China's submarine also encountered internal waves and was suddenly dragged from a depth of 8 meters to a depth of 80 meters during the voyage, narrowly encountering an accident.
Is Neibo so powerful? That's right, the amplitude of internal waves is much larger than that of sea surface waves, ranging from tens of meters low to hundreds of meters high; the wavelength is at least several hundred meters, or even more than 10,000 meters. In fact, it is not difficult to understand. The density difference between seawater and atmosphere at the ocean surface is huge, while the density difference between layered seawater deep in the ocean is very small. According to Archimedes's Law (Law of Buoyancy), it is much easier to lift heavy objects in water than from the sea surface to the air, so the same external force produces much greater fluctuations inside the sea than on the sea surface. The largest internal wave discovered so far in the world was discovered by scientists from China Taiwan in the South China Sea. Its amplitude reaches 170 meters and is 50 stories high; the sand wall rolled up by strong currents at the bottom is like a desert storm, which can form sand dunes 16 meters high.
Unlike waves on the sea surface, internal waves cannot be directly observed. So how do oceanographers study them? With the advancement of science and technology, scientists can place a large number of advanced instruments deep in the ocean to observe changes in seawater flow velocity, temperature, and density in the deep sea. Using the large amount of observation data obtained and complex computer calculations, we can simulate internal waves that cannot be seen with the naked eye.
The internal wave is extremely powerful and is an important sea water movement. It can not only transfer the energy of the upper ocean to the deeper layers, but also bring the colder seawater in the depths and the nutrients in it to the warmer shallow layers, thereby promoting the growth of organisms. The study of internal waves is of more important significance to the military. Although a submarine may be very dangerous when encountering internal waves, the fluctuations caused by internal waves will also strongly interfere with the function of sonar, which will make it difficult for the enemy to monitor and be beneficial to the submarine. Concealment.