What if the ocean climate control "conveyor belt" stops?

In 2004, the movie "The Day After Tomorrow" envisioned a world in which the Atlantic Ocean current regulating climate completely collapsed, leading to catastrophic sea level rise and extreme weather events in the United States. The unusual flood flooded the building, and the biting air froze the pedestrians and the freedom of the statue. It sounds like a disaster movie, but in fact, the day after tomorrow in 2004, the collapse of the North Atlantic Ocean current brought the world to the end of a whirlwind climate.

Although the ocean current has not really collapsed, scientists have found in two new studies that the ocean current is greatly weakened. In fact, this ocean current has never been so slow in 1500 years, and this discovery may have a serious impact on global weather and sea level rise (although it is not a serious impact in disaster films). atlantic

Ocean current is called the warm surface of the Atlantic meridional overturning circulation (AMOC) ferry. According to the National Oceanic and Atmospheric Administration, seawater is transported northward (heat is released into the atmosphere) and cold water is transported southward in deeper ocean layers. Its circulation transmits heat to all parts of the world like a conveyor belt. If it stops moving, the heat will not be released and the weather will be destroyed. [The End of the World: Nine Real Ways to End the Earth]

However, AMOC is becoming weaker and weaker, and the main culprit is the injection of cold water caused by the uncontrolled melting of glaciers, sea ice and permafrost. If the earth's temperature continues to rise and the ice reserves continue to melt, AMOC may be further weakened. Scientists published reports in these two studies. In a study published in Nature yesterday (April 1 1), sand was used.

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The researchers analyzed marine sediments from a core on the east coast of the United States, most of which came from the Labrador Sea in the North Atlantic. They examined the positions of sand grains of different sizes in geological records to reconstruct how the water flow carrying these grains changed with time, said Delia Oppo, a co-author of the study and a senior scientist in the Department of Geology and Geophysics of woods hole oceanographic institution.

The researchers traced the weakening of ocean currents back to the end of the Little Ice Age in the middle of19th century, a cold period that lasted for centuries and frozen northern Europe. When the temperature starts to warm, the fresh water flowing from the melting ice to the Nordic waters will dilute the salt water near the surface. Oppo told Life Science that this weakened the current, prevented it from carrying larger grains of sand, and made scientists understand the difference in current intensity.

The meridional circulation of the Atlantic Ocean, also known as the Gulf Stream System, brings warm water from the south to the north, where it sinks deeply and transports cold water from the north to the south. The weakening of this major ocean circulation may have extensive and potentially destructive effects. (Caesar/Pique) Then, since 1950s, the northern hemisphere has started another phase of warming and ice melting-this time, it may be due to human-induced climate change-and more cold water has been injected into the ocean, further weakening the ocean circulation system, David Sonali, the main author of the study and a senior lecturer at University College London, told Life Science in an email. Sonali said:

"Theories and models show that when the climate warms and the fresh water input increases, the AMOC will weaken, both of which are part of global warming." . The research team estimates that the current has weakened by about 15% to 20% since it began to weaken in the mid-9th century.

Another study that found "fingerprints" was also published in today's Nature, and reached the same conclusion. This time, by consulting the sea surface temperature data at the end of 19. In this study, the researchers' temperature analysis confirmed the computer model's prediction of the behavior of AMOC, and proposed that the current circulation intensity would be about 65,438+05% lower than that in 1950s.

"The evidence we can provide now is by far the most powerful," study co-author Stefan Ramstoff, a professor of marine physics in potsdam institute for climate impact research, said in a statement.

The researchers found an ocean temperature pattern, which is the "fingerprint" of AMOC deceleration: the Gulf Stream and the abnormal warming of colder waters near Greenland. According to research, this shows that warm water is not transported to the north as effectively as before.

"The specific trend pattern we found in the measurement is exactly the same as the result of the slowdown of the Gulf Stream system predicted by computer simulation," Ramstoff said. I see no other reasonable explanation.

Although the two research groups used different methods, they came to a similar conclusion: on our vibrant planet, a key part of the climate system did not work as before.

"What is happening now is that evidence is coming together from different sources," Oppo told Live Science. Therefore, we are more and more confident, because we have seen some studies begin to show similar things in different ways, "[7 ways the earth changes in the blink of an eye].

In the uncertain future, although the possibility of complete disintegration of AMOC is extremely small, the ocean circulation system may continue to weaken. Oppo told Live Science that this prospect is far from reassuring. Previous studies have shown that weak AMOC will bring more drought to the Sahel region of Africa on the edge of the Sahara desert; * * * Sea level rise in American coastal cities; Encourage the pattern of getting colder and colder in winter in Europe and the northeastern United States; Let the whole of Europe become warm in summer. However, Oppo said that more research is needed to confirm the lasting relationship between "KDSP" and "KDSP", but Oppo pointed out that the weakened AMOC does reduce the efficiency of ocean absorbing atmospheric carbon dioxide. She said that if the ocean current continues to weaken, it may absorb less carbon dioxide, which will lead to an increase in the amount of greenhouse gases in the atmosphere and may aggravate the impact of global warming.

"More research on the potential weather impact of the deceleration of AMOC and the related sea surface temperature model." "Considering the results of two new studies, it is necessary to further weaken AMOC," Thornaley told Life Science.

Editor's note: This article updates and clarifies some statements made by Delia Oppo.

This is an original article about life science.