Sea color and water color, which sound the same, are actually two different concepts.
Sea color is a large area of sea color that people see. People who often contact the sea will feel this way, and the color of the sea will change because of the weather. Wan Li is sunny, and when Wan Li is clear, the color of the sea water will be bright blue; When the sun rises, the morning glow shines, or the sun sets, Guanghua reflection can dye the sea golden; When the clouds are gathering and the storm is fierce, the sea looks gloomy and hazy, and it is dark blue. Of course, this visual impression caused by weather conditions is only an appearance, and it can't reflect the true color of ocean water.
Water color refers to the color displayed by the sea itself. It is the result of the selection, absorption and scattering of solar radiation energy by seawater, and has no direct relationship with weather conditions. Usually, the bright sunshine we see is composed of seven colors of light: red, orange, yellow, green, cyan, blue and purple. These different colors of light have different wavelengths. However, seawater has obvious selectivity for light with different wavelengths, whether it is absorption or scattering. In terms of absorption, long-wave rays such as red, yellow and orange entering the seawater are almost completely absorbed by the seawater at a depth of 30-40 meters, while green, blue and cyan rays with shorter wavelengths, especially blue rays, are not easily absorbed, and most of them are reflected by the sea surface; In terms of scattering, blue light is the color most scattered by water molecules in the whole incident light spectrum. So, it looks like the sea is blue.
The transparency and color of seawater depend on the optical properties of seawater itself, and they have a certain relationship with the sun's rays. Generally speaking, the stronger the sunlight, the greater the transparency of the seawater and the higher the water color (scientists classify the water color into different grades according to the different colors of the seawater to determine the water color), and the deeper the light penetrates the seawater. On the contrary, the weaker the sunlight, the more opaque the seawater, the lower the water color and the shallower the penetration. Therefore, with the gradual decrease of transparency, the color of the ocean generally changes from green and turquoise to cyan, blue and dark blue.
In addition, the nature and condition of suspended solids in seawater also have a great influence on the transparency and color of seawater. In the marine part, the water area is vast, with less suspended matter, smaller particles, greater transparency and blue water color. For example, Sargassum in the middle of the Atlantic Ocean is the most transparent sea area in the world, with little influence from mainland rivers, high salinity, weak seawater movement, fast sinking of suspended solids, slow biological reproduction and high transparency of 66.5 meters. In the shallow sea area on the edge of the ocean, the water color is green, yellow-green or yellow due to the turbidity of continental sediments, large suspended solids and low transparency. For example, the transparency of Jiaozhou Bay in China's coastal area is 3 meters, while the sea area near the Yellow River estuary in Bohai Sea is only 1 ~ 2 meters.
Geographically, the color and transparency of water in the ocean change with latitude. In tropical and subtropical waters, the water layer is stable and the water color is high, mostly blue; In temperate and cold regions, the water color is low and the sea water is not so blue. Of course, the salt content of seawater or other factors will also affect the color of water. The salt content of seawater is less, and the water color is mostly light blue; If there is too much salt, it looks blue.
Besides transparency and water color, other factors can also determine the color of a certain sea area, such as the famous four oceans of red, yellow, black and white.
The Red Sea is an inland sea in the Indian Ocean. Like a huge arm of the Indian Ocean, it is deeply inserted between northeast Africa and Arabian Peninsula, and becomes the natural dividing line between Asia and Africa. The color of the sea water in the Red Sea is very strange, usually blue-green, but sometimes it turns red-brown. Why is this?
It turns out that there is a kind of seaweed called blue-green algae, which breeds in the surface water of the Red Sea. After plankton died, the body changed from blue-green to reddish brown. A large number of dead algae are floating on the sea surface. Over time, the sea looks like a red coat, which makes the sea look red. At the same time, there are many red coral reefs in the narrow shallow sea on the east and west sides of the Red Sea, and the rocks on both sides are ochre. Their foil and reflection make the sea more reddish brown. In addition, the nearby deserts are widely distributed, and the hot air is blowing gently. Red sand often fills the sky and falls into the sea, thus "dyeing" the Red Sea more red. The reddish-brown seawater has earned it the reputation of "Red Sea".
The Yellow Sea, located between Chinese mainland and the Korean Peninsula, starts from the mouth of the Yalu River in the north, reaches the Qidong corner on the north bank of the Yangtze River estuary in the south, and reaches the southwest corner of Jeju Island in Korea. The Yellow Sea has low transparency and light yellow color. Because the yellow sea water is very shallow, it can't completely absorb red light, orange light and yellow light, and some of it is reflected and scattered. When they are mixed together, the seawater should be yellow-green. However, for a long time in history, the Yellow River once carried a lot of sediment into the sea from northern Jiangsu. Later, although the Yellow River diverted into the Bohai Sea, the Yangtze River, Huaihe River and other large and small rivers also brought a lot of sediment, and the sediment concentration in seawater was relatively high. In addition, shallow water and low salinity make it difficult for sediments to precipitate, thus turning seawater yellow. The "Yellow Sea" got its name.
The Black Sea is located between the Balkan Peninsula in southeastern Europe and Asia Minor Peninsula in western Asia, and is a typical inland sea. The northern part of the Black Sea is connected with the Azov Sea through the narrow Kerch Strait, and the southwestern part is connected with the Mediterranean Sea through the Turkish Strait. The salinity of the Black Sea is lower than that of the Mediterranean Sea, but the water level is higher than that of the Mediterranean Sea. Therefore, the light seawater on the surface of the Black Sea flows to the Mediterranean Sea through the Turkish Strait, while the salty and heavy seawater of the Mediterranean Sea flows to the Black Sea from the bottom of the Strait. The water in the southern part of the Black Sea is very deep, and the lower layer constantly receives deep seawater from the Mediterranean Sea. These seawater are salty and heavy, and there is little convection exchange with the surface seawater, so the deep seawater is anoxic, like a stagnant pool, containing a lot of hydrogen sulfide. Due to the toxicity of hydrogen sulfide, shellfish and fish in the ocean cannot survive in the deep sea. The sewage secreted by organisms in the upper seawater and the bodies of animals and plants sink to the depths to rot and stink, turning the seawater into bluish brown. Sailing on the Black Sea by boat, looking down from the deck, you will find that the color of the sea water is very deep, hence the name "Black Sea". It is also said that the Black Sea is called the Black Sea because there are strong storms in winter, towering black cliffs on both sides and the weather in the storm warning. In fact, the water in the Black Sea is not black. Its blackness is only the result of mud on the seabed. In normal weather, the Black Sea is black and clear.
Located near the Arctic Circle, the White Sea is the marginal sea of the Arctic Ocean. White sea looks white. However, its seawater is no different from other seawater. It is colorless and transparent, not white, except that the White Sea is located in high latitudes with a cold climate, and the ice age lasts for six months in a year. Due to the snow and ice cover and the floating of white icebergs, we seldom see the common rough waves on the sea, which makes the long winter form a white world of snow and ice. Looking up, I saw the snow-covered sea, boundless and dazzling. Therefore, the white sea has become a veritable "white sea".