In the Northwest Pacific, there is a strong current like a huge river that flows from south to north day and night. Because it looks almost black from a distance, it is named the Kuroshio. In fact, the Kuroshio is not only not dark, but also clearer than the surrounding sea water. It contains very little impurities and very little marine life lives in it. When the sun shines on such a transparent sea surface, the sea water appears visually blue-black. The average width of the Kuroshio is about 150 kilometers, the thickness is about 1 kilometer, and the speed can reach 12 kilometers per hour at its fastest, which is faster than the speed of ordinary sailboats. Through long-term observation and research, scientists have found that the Kuroshio transports about 60 million tons of seawater per second, equivalent to the runoff of more than 1000 Yangtze River.
People have been paying attention to the black tide for a long time. A long time ago, some fishermen along the coast of Asia discovered that there would sometimes be a strong, warm, and salty current coming from the southern waters, and the flow rate was quite fast. Many fish migrated on this free "cruise ship". As a result, fishermen can catch a considerable number of migratory fish in the Kuroshio Basin, as well as large fish attracted by these fish to feed.
The temperature of the Kuroshio is higher than that of ordinary ocean currents, second only to the Gulf Stream, which is the highest in the world. Its impact on the climate of coastal areas of East Asia is very significant. For example, the Qinhuangdao Port in China is not frozen in winter; while Shanghai is full of leaves, Kyushu in Japan at the same latitude is still luxuriant, benefiting from the Kuroshio and its branches.
So, where did the water of the Kuroshio come from? Observations by ocean satellites and buoys have found that the Kuroshio originated in the equatorial Pacific Ocean. The seawater near the equator is subject to strong solar radiation, has higher temperatures and evaporates quickly, so it contains more salt. Under the combined effect of the earth's rotation and sea surface winds, this part of the "distinctive personality" seawater starts from the equator, passes through the Philippine waters, enters the East China Sea from the east side of China Taiwan, passes through the Tukara Strait, and winds northeast along the sea area south of the Japanese Islands, with a total length of about 4000 kilometers. The course of the Kuroshio sometimes resembles a winding snake, so it is called the "snake bend" by scientists. This "serpentine bend" changes differently every year and has different impacts on the climate. Scientists are working hard to explore in order to solve the mysteries of the Kuroshio.