Shulou(Shulou.com)11/24 Report--

This article comes from the official account of Wechat: Earth knowledge Bureau (ID:diqiuzhishiju), author: Xiao Zhe, proofread: gu Hanying / Editor: tuna

The original title: "Tokyo, why is it so hot?" "

Japan Tianbao 2009 (1838) April 29, "elderly Maru" carrying rice from Toyama, to Osaka and Niigata delivery. At that time, the Japanese coastline under the jurisdiction of the Tokugawa shogunate was filled with ships transporting goods. In early October, "Senior Maru", led by Captain Hirashiro, was loaded with kelp from Hokkaido, together with cotton and sugar purchased in Osaka, ready to return along the eastern route. Due to the weather, the fleet took a short break in Sendai.

This batch of kelp included part of the smuggling by the Qing government at that time.

Therefore, the fleet chose to make a detour on the return trip and take the eastern route to avoid regulatory ▼.

When the weather cleared up and set sail on November 23, the fleet encountered strong winds as they left the harbor, the rope supporting the canvas suddenly broke, and the ship out of control was pushed out to sea by strong currents. At noon on the 25th, the crew found in despair that the last piece of land, Jinhua Mountain, had disappeared behind the horizontal line.

With the arrival of the long and cold winter, the ship's rice and water gradually ran out, several crew members died one after another, and people had to scrape by on kelp and Rain Water. In April 1839, after nearly five months at sea, Elder Maru finally met a whaling ship called James Loper. With the help of weirdly dressed foreigners, she finally returned to Japan.

Rescued from Hawaii, sent to Sitka.

Kamchatka, Okhotsk, Alaska

It took five years to return to Japan for ▼.

In fact, in the decades before and after the accident of "Senior Maru", there were quite a number of records showing that many shipwrecked ships drifted to Alaska in the closed Edo era of Japan at that time. The strong current that pulled these ships out of closed Japan and sent them to the North Pacific is the protagonist of today's story: the Kuroshio.

The world-famous painting "Kanagawa Surfing" is painted

The scene of heroic boatmen wrestling with the Kuroshio in order to survive

(figure: wikipedia) ▼

Black tide, countless waves string Kuroshio, its English name comes from the Japanese pronunciation of the Kuroshio, also known as the Japanese warm current, is the world's second largest ocean current, after the Gulf of Mexico warm current. The Kuroshio carries warm water from the tropical western Pacific to cold high latitudes from south to north.

Because the Kuroshio contains fewer impurities and nutrients, sunlight is less reflected back to the surface after penetrating the surface of the water, so it is darker than other normal sea water and is black from a distance, hence the name Kuroshio.

Tuna shows you the Kuroshio at different times of the day.

Without filter, it is really black (taken in the South Yellow Sea and East China Sea)

(it is better to swipe across the screen) ▼

The Kuroshio originated in the sea east of Luzon Island in the Philippines, where the North Equatorial warm current is blocked northward, and the mainstream goes northward along the east coast of Taiwan Island and the west side of the Ryukyu Islands to the east coast of the Japanese archipelago. It meets the pro-tide (also known as the Kuril cold current) going south from the Okhotsk Sea near latitude 40 °N, and winds down to the east and extends to the North Pacific warm current, all the way east to the west coast of the United States.

You can remember this picture to help you read the rest.

Or you don't have to remember, because it will appear again.

(source: Korea Hydrology and Oceanography Bureau) ▼

When the mainstream of the Kuroshio enters the East China Sea from the Strait of Huna, there is a branch near the Diaoyu Islands called the Taiwan warm current, which flows northwestward into the coastal waters of Zhejiang, all the way north to the mouth of the Yangtze River in China.

Near latitude 31 °N, the ocean current meets the coastal current formed by the runoff of the Yangtze River into the sea and the cold current going south near the Zhoushan Archipelago in China, forming an obvious front, which is called "flow separation" by locals, thus forming the largest Zhoushan fishing ground in China.

Because a large amount of sediment from the Yangtze River enters the sea area near Zhoushan, it is yellowish brown.

On the other hand, the mainstream of the Kuroshio flows to the northeast along the deep trenches in the East China Sea, and another branch is separated in the southwest of Kyushu Island, Japan, and passes through the Taiwan Strait into the Sea of Japan, which is called the warm current. The horse warm current is also divided into a small branch in the south of Jeju Island into the Yellow Sea, which is called the Yellow Sea warm current (also known as the Western Dynasty fresh warm current).

Due to the semi-closed nature of the Yellow Sea and Bohai Sea, the current situation here is more complex ▼

The Yellow Sea warm current flows northward along the longitude 124 °E, and then flows into the Bohai Sea through the Bohai Strait. This current presents a relatively high temperature and high salt tongue, extending from the South Yellow Sea to the Bohai Sea, which has an important impact on the closed Bohai Sea.

The Yellow Sea warm current is strong in winter, weak in summer, and even disappears. It is due to the influence of the Yellow Sea warm current that Qinhuangdao and Huludao in China have become famous ice-free ports in northern China.

The Bohai Sea may freeze in winter, but the tides in Anaya keep rising and falling.

In fact, the mainstream of the Kuroshio does not flow along the edge of the East Asian continent, but along the East Asian island arc, so the influence of the Kuroshio on Taiwan Island and Japan on the island arc is more significant than that of the East Asian continent. However, the tributaries of the Kuroshio can also extend into the marginal sea of the East Asian continent, thus affecting the continental region to a certain extent.

Like the Kuroshio mainstream, the Kuroshio nearshore branch

It has also greatly affected the inshore ecology of our country.

(base: ArcGIS Earth) ▼

Because the Kuroshio is located at the western boundary of the Pacific basin, intensified by the earth's rotation, the Kuroshio shows the characteristics of fast velocity, narrow amplitude and deep depth. its average width is more than 200km, depth is about 400m, and the fastest velocity is 2-3m / S. the average flow is about 22 million cubic meters per second, and the sea water flow measured off the tide headland of Shikoku, Japan can reach 65 million cubic meters per second. About 360 times the flow of the Amazon, which is the largest in the world.

Moreover, because the Kuroshio comes from the North Equatorial warm current, sufficient solar radiation heating in low latitudes and a large amount of evaporation of sea water, the water temperature and salinity of the Kuroshio are higher.

An open water exchange, warm water, plenty of food

The existence of the Kuroshio allows warm water fish such as whale sharks to haunt Japan.

The East Asian climate regulator is similar to the northward movement of the North Atlantic current to warm the European climate, and the warm Kuroshio is also closely related to the local climate. The annual average water temperature of the Kuroshio is about 24-26 ℃, about 18-24 ℃ in winter, 22-30 ℃ in summer, 7-10 ℃ higher than that of the neighboring Yellow Sea, and 20 ℃ higher in winter. While the warm current heats up the nearby air, it also makes more water vapor enter the atmosphere. So the Kuroshio brings a warm and humid climate to Japan.

Especially at the confluence of the Kuroshio and the Thousand Island cold current.

Heavy precipitation caused by the interaction between seawater and atmosphere

Let Japan be separated by 40 degrees north latitude.

The latitudes of Qingdao and Shanghai in China are similar to those of Tokyo and Kyushu in Japan respectively, but the climate is very different. When people in Qingdao wear cotton-padded clothes, people in Tokyo still wear autumn clothes; when leaves fall in Shanghai, the subtropical plants of Kyushu are still verdant.

The next time you see Tokyo people wearing skirts and shorts in winter, it is not entirely because of their cold resistance, but more importantly, thanks to the Kuroshio, the average temperature in Tokyo is 4-9 ℃ even in January. In contrast, the average temperature in Qingdao in January is only-3 ℃-2 ℃.

So there is a scientific basis for Tokyo fever.

There is a more complex relationship between the Kuroshio and the atmosphere. As early as the 1970s, Chinese scientists found a strong correlation between the north-south offset of the Kuroshio and the drought and flood in the Yangtze-Huaihe River Basin and North China.

This is due to the obvious temperature difference between the high-temperature Kuroshio and the relatively cold sea water in the north, forming a strong ocean front. Through the interaction between the ocean and the atmosphere, it affects the atmospheric frontal zone at the junction of cold and warm air, and the atmospheric frontal zone is the rain belt that brings precipitation.

When the Kuroshio is stronger, the temperature is higher and can extend to the north, it will enhance the intensity of the western Pacific subtropical high in summer and move northward. The northward movement is followed by the rain bands that affect the precipitation in China, which may further lead to more precipitation in North China and less precipitation in the Yangtze-Huaihe River Basin. Therefore, the sea surface temperature of the Kuroshio can be used as a predictor of summer precipitation in China.

At the same time, the Kuroshio extension line meridian oscillation line of sea surface temperature (SST)

It is also significantly related to the number of coastal landfall typhoons in East Asia in summer.

Typhoon plum blossom (photo: Wikipedia) ▼

The storm axis refers to the area where the rapidly changing atmospheric vortex is the most active, with a life span of about 2.5-6 days, where many cyclones and anticyclones are generated and died out. Therefore, the location of the storm axis not only has a profound impact on the local weather change, but also affects the weather and climate change by affecting the atmospheric circulation.

There are three storm tracks in the Northern Hemisphere, namely, the North Atlantic Storm, the North Pacific Storm and the Siberian Storm. The strong heat transport of the Kuroshio to the atmosphere can "anchor" the North Pacific storm axis, thus profoundly affecting the weather and climate change in East Asia.

The interaction between the Kuroshio and the surrounding cold water masses in the North Pacific Ocean

Makes it easier for storms to be born along the route.

(source: earth.nullschool.net) ▼

The current of the Kuroshio, a precarious fishing resort, is very fast, and many migratory fish are riding northward on the Kuroshio, so a considerable number of migratory fish can be caught in the Kuroshio basin, as well as other large fish attracted by these fish. large fish that come looking for food.

Among these vast armies of migratory fish, we refer to those born and died in rivers and growing up in the ocean as retrograde migration, such as salmon, while those born and died in the ocean and growing up in rivers are called downriver migration, such as eel.

Although the eel usually nests in the hole

But in fact, he has a very drifting life.

Although humans have a long history of hunting and cooking eels, its life history has always been a mystery. In the millennia of living with eels, the Japanese have only observed that adult eels disappear quietly in autumn, and young eels return in the following spring, but no one knows the blank pieces in the middle.

Its popularity at the dinner table gave birth to the obsession with human eel farming.

If you want to breed artificially, you have to figure out the whole life history.

It was not until 1991 at the end of the 20th century that Katsumi Hashimoto of the Institute of Oceanography of the University of Tokyo in Japan preliminarily determined the spawning site and migration route of the eel according to the survey results of the "Baifeng Maru" research ship. The story of the eel's life was finally restored in 2005 when scientists confirmed that a more detailed location should be in the western Mariana Islands, 2000 kilometers from Japan.

The western waters of Mariana are the spawning ground for all Japanese eels.

(source: WWF) ▼

The life cycle of eel can be divided into seven developmental stages: egg, early willow eel, willow eel, glass eel, eel line, yellow eel and silver eel. After growing in land and rivers for 5-6 years to sexual maturity, Japanese eels metamorphosed from yellow eels to silver eels and spent half a year migrating to a deep sea more than 5000 kilometers apart to lay eggs. The change of body color is to adapt to the deep-sea environment of Jianghe migration and spawning.

Eels can actually be colorful if necessary.

It's just that no one can see clearly in the deep sea, so they just grow up.

Eels are produced in the oceanic region because of their barren water, few natural enemies and high survival rates of their offspring. The Japanese eel lays eggs downstream from September to November in the western waters of the Mariana Islands in the Pacific Ocean, laying eggs only once in its lifetime, and then safely ending its legendary life at the bottom of the sea.

With a lifetime of debauchery and freedom, and finally going home for love, the eel is better than anyone else.

In the early stage after hatching, willow eel and willow eel, with flat sides and shaped like willow leaves, are very suitable for long-distance drifting at sea. After drifting from east to west with the North Equatorial current to the eastern waters of the Philippines, they use the Kuroshio highway and many branches of the Kuroshio to disperse their offspring to grow in the inland rivers of Chinese mainland and Taiwan Island, South Korea and Japan.

So next time before eating eel, you can think of fish that come from thousands of kilometers with the help of the Kuroshio.

Willow eel: "I have taken many detours in my life" (source: Bilibili) ▼

The Hokkaido fishing ground is located at the confluence of the Japanese warm current and the Thousand Island Cold current. Due to the difference in sea water density, the cold water with high density sinks and the warm water with low density rises, which stirs the sea water vertically and brings the organic matter deposited on the seafloor to the sea surface. Provide rich bait for fish.

And because the confluence of cold and warm currents will also produce a front, this "water barrier" also hinders the mobility of non-migratory fish to a certain extent, thus making the Hokkaido sea area a world-famous fishing ground. The main fish production types include salmon, haddock, Pacific herring, far eastern sardines, saury and so on.

Hokkaido fishing ground, one of the four largest fishing grounds in the world

It is also the most famous natural fishing ground ▼ in Asia.

However, according to the fishery report of Hokkaido Agricultural Affairs Office in September 2020, due to the problems of overfishing and pollution, compared with the 1980s and 1990s, the sea surface catch of the main fish species in Hokkaido area has decreased to varying degrees.

Zhoushan fishing ground, which is the same as Hokkaido fishing ground.

At one point, there was "no fish to fish" in the East China Sea because of overfishing and other problems.

In particular, an earthquake measuring 9.0 on the Richter scale followed by a tsunami occurred in the northeastern Pacific region of Japan in 2011, which led to the leakage of radioactive material from the Fukushima Daiichi nuclear power plant.

In April 2021, the Japanese government formally decided to discharge millions of tons of nuclear contaminated water from the Fukushima nuclear power plant into the sea in spite of the doubts and objections of other countries. These radioactive materials will have a devastating impact on the fishing ground along the Kuroshio around Japan, and what is more serious is that these radioactive materials will circulate through the Pacific Ocean and even the global ocean, affecting the marine environment of the whole earth.

After the incident, the Ministry of Health and Labor of Japan detected the radioactivity of the fish caught in Fukushima.

The results showed that the sample exceeded the Japanese food hygiene standard by 14 times.

This warm current along the East Asian island arc will have a profound impact on the weather, climate, marine ecology and even human civilization.

And its scope of influence will extend not only to the East Asian region, but also to the whole world through a variety of possible complex mechanisms and roles in the Earth system. In the context of today's global warming, there will be more uncertainty about the response and state of the Kuroshio.

The only thing that is certain is that--

Man's karma created by nature will eventually be added to himself.

(source: GEOMAR) ▼

References:

1. Https://wuu.wikipedia.org/ wiki / Kuroshio

2. Https://www.britannica.com/place/Kuroshio

3. Http://www.baiven.com/baike/220/258171.html

4. Https://www.timeanddate.com/weather/japan/tokyo/climate

5. Https://www.wwf.or.jp/activities/basicinfo/3671.html

6. Https://www.data.jma.go.jp/gmd/kaiyou/data/db/kaikyo/knowledge/kuroshio.html

7. Https://seafood-reference.com/unagi/unagi-seitai/entry1476.html

8. Https://homepage.ntu.edu.tw/~yshan/subpage/eel%20classroom/biology/4.html

9. Https://www.maff.go.jp/hokkaido/toukei/kikaku/gurafu_gaiyou/gyogyou2010/attach/pdf/gyogyo2013-55.pdf

10. Doufu Hoshino's "the Tree of Travel"

11.Alan P. Trujillo, Harold V. Thurman, Zhang Ronghua et al. An introduction to Marine Science

twelve。 Marine Climate Group, Climate Research Office, Institute of Geography, Chinese Academy of Sciences. The relationship between the Kuroshio, drift ice and precipitation in eastern China [J]. Meteorological Science and Technology data (1973)

13.Young-Oh Kwona, Michael A. Alexander et al. Role of the Gulf Stream and Kuroshio-Oyashio Systems in Large-Scale Atmosphere-Ocean Interaction: a Review [J]. Journal of Climate. (2010)

14.Buesseler K, Aoyama M, Fukasawa M. Impacts of the Fukushima nuclear power plants on marine radioactivity [J]. Environmental science & technology, 2011, 45 (23): 9931-9935.

15. Yu Peilong, Wang Yongqiang. Relationship between winter Kuroshio extension SST and summer precipitation in eastern China under the future RCP scenario [C] the 32nd annual meeting of the Chinese Meteorological Society in 2015

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