下にあるような内容だが、日本海の異変を取り上げつつ地球全体の海洋の変化に警告を発している。
日本海の海水の循環の変化がこのまま進行すると100年後には日本海の生態系に大きな変化が起こると言う予測である。
同じ記事の中に全地球を巡る熱塩循環（海洋大循環）の図が掲載されている。日本海での100～200年周期の循環で起こる変化は1000～2000年周期で循環している熱塩循環に起こる変化を先取りしているのだと示している。
この記事をきっかけに、しばらく海洋の温暖化について書いていく予定である。
A very interesting article appeared on the Nikkei newspaper of 14 April , 2018, more than a year ago, though.
Contents are below, it warns the change of the oceans of the whole earth while taking up the change of the Japan Sea.
It is predicted that if the change in the seawater circulation in the Sea of Japan proceeds as it is, a major change will occur in the ecosystem of the Sea of Japan in 100 years.
In the same article, the figure of the thermohaline circulation (ocean circulation) around the whole earth is raised. The changes that occur in the 100-200 year cycle in the Sea of Japan indicate that they anticipate changes that occur in the circulating thermohaline cycle in the 1000-2000 year cycle.
From now, I will write about ocean warming several times.
English text translated from the Japanese text is below the figures. (Sorry translation was done by just using "Google translate", and no revision is done.)
A quiet anomaly in the Sea of Japan, reduced oxygen in the deep sea. Is global warming affecting?
Something is wrong with the circulation of seawater in the Sea of Japan. Seawater in the surface layer, which contains a large amount of oxygen, does not sink deep, and oxygen deficiency in the deep sea is progressing. It seems that the winter cold of Eurasia has become milder. Although the remarkable effects have not come out yet, ecosystems such as fish and shellfish may change. Researchers around the world have begun to draw attention as a model sea area to investigate the relationship between climate change and seawater circulation.
Associate Professor Tomoharu Chite of Kyushu University observing the current velocity in the deep sea of about 2000 meters was surprised to see the analysis results of the latest data obtained off the west of Aomori Prefecture.
A device for recording the flow velocity of seawater was investigated by sinking it in the deep sea of the Sea of Japan (provided by Associate Professor of Kyushu Univ.)
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A device for recording the flow velocity of seawater was investigated by sinking it in the deep sea of the Sea of Japan (provided by Associate Professor of Kyushu Univ.)
The average flow velocity from August 16 to May 17 was about 3.3 centimeters per second, which was more than 30% slower than the average flow velocity in 1994-95. The same phenomenon has not been confirmed in all sea areas. Although it can not be concluded, Associate Professor Sentei said, "There is a possibility that the deep sea flow in the Sea of Japan has weakened."
It is thought that the cause of the slowing of the deep sea velocity is that the surface seawater is not cooled in winter.
Cold and strong northwesterly wind especially blows around Vladivostok in the Russian Far East. Chilled seawater becomes denser. In other words, it becomes heavy. In addition, if part of the seawater freezes, the saltiness of the frozen seawater will increase and become heavy. The heavy seawater in the surface part sinks toward the deep sea, and the seawater in the deep layer is pushed out and rises to the surface. The warm winter year is increasing and the circulation seems to be slowing down.
There are other observations that support this phenomenon. The Japan Meteorological Agency (JMA) continuously investigates the sea water temperature and oxygen concentration in the "Nippon Basin" and the "Yamato Basin", which are basin-shaped at the bottom of the Japan Sea. Since the 1990s, the sea water temperature at a depth of 2000 meters has risen at a pace of about 0.02 degrees in 10 years, and the oxygen concentration in seawater continues to decrease.
Nohra Noragaki, a senior researcher at the National Institute for Environmental Studies, measured the concentrations of three types of fluorocarbons in seawater and examined how much of the surface seawater sinks. Freon used for refrigerants such as refrigerators and air conditioners has different proportions according to the year. Freon in the atmosphere is slightly soluble in seawater and can be estimated if the concentration in seawater is accurately measured. If we separate 75 years ago and later, the amount of sinking has been reduced to less than 40% compared to that before 75 years.
Dr. Aramaki predicts that "the deep sea oxygen will be depleted after 100 years, assuming that this sinking is completely eliminated in the Sea of Japan."
What kind of influence is there in the decrease of oxygen in the deep sea? Although there are many unknown points, many experts say that the ecosystem of the Sea of Japan changes.
Oxygen is essential for the respiration of marine life, and it is also necessary for plankton to break down organic matter. If there is a lack of oxygen and the plankton decreases, then the seafood that eats the plankton will be less likely to be dull. The Sea of Japan, including cold yellowtail and crabs, is rich in seafood. Surveys that keep track of the amount of plankton will be important.
In the surface area, the rise in sea temperature is said to reduce the amount of snowfall in winter on the Japan Sea side of the Japanese archipelago, and increase rainfall throughout the year. However, detailed analysis and prediction have just begun and are for further study.
There is another major reason why researchers are interested in the anomalies in the seawater circulation in the Sea of Japan.
The Sea of Japan is surrounded by the Japanese Archipelago and the Eurasian continent, and the water depth reaches about 3800 meters deep. It is a highly closed structure where salt water is accumulated in a deep bath. Although the area is a small sea less than 1% of the Pacific Ocean, there is a circulation similar to that of the seawater circulation found in the Pacific Ocean, the Atlantic Ocean, and the three oceans of the Indian Ocean. It has been found that the period is very short, 100 to 200 years, compared to 1000 to 2000 in the ocean.
In considering the impact of climate change on the ocean, the Japan Sea can be said to be a good place to quickly detect change. Aramaki, a senior researcher at the Environment Research Institute, compares the information that can be observed in the Sea of Japan to "seeing possible changes in the world's oceans as fast-forwarding to DVDs."
In fact, the Sea of Japan is positioned as a "mini-ocean", and the United Nations Intergovernmental Panel on Climate Change (IPCC) points out that it is an important area to study the effects of global warming.
However, the Sea of Japan is bordered by Russia, South Korea, and North Korea, making it difficult to conduct free surveys for research purposes. Professor Toshiro Takao, Professor of the University of Tokyo, who began focusing attention on the changes in the Sea of Japan quickly, said that it is necessary to cooperate with neighboring countries to establish a system that enables continuous observation.
(Science and Technology Department Tomoya Koshikawa)
