For more than a thousand years, the natural conveyor belt, which is important for the planet, has been working properly in the Atlantic. But humanity has spoiled it. In what way – let’s check the Chas News survey.
Do you believe in the fountain of eternal youth? Most likely not, because it is difficult for modern man to believe in a legend that cannot be reasonably explained. But Juan Ponce de Leon, a Spanish navigator who lived 500 years ago, believed in this kind of miracle and even tried to find it during an expedition to the New World in 1513. At least, this is a common myth.
Intentionally or not, but during that trip, the traveler did not find any fountain. However, he made another discovery that went down in history. He discovered the Gulf Stream, a warm ocean current that carries water from the Gulf of Mexico to European shores. Ponce de Leon would probably be surprised to learn that in five centuries, a powerful natural phenomenon will begin to weaken and slow down. But a new study by scientists from Britain, Ireland, and Germany shows that this is exactly what is happening to him. And it does not promise anything good to the planet.
A look into the past
Researchers from three European countries have identified problems not with the Gulf Stream itself, but with the Atlantic Meridian Circulation (AMOC), the system of currents in the Atlantic Ocean of which it is a part. They looked at 1,600 years into the past of the system and found out how it worked during that time.
For the most part, the AMOC functioned stably, but in the middle of the 19th century the situation changed. The system began to slow down. In the middle of the XX century this process intensified and since then the circulation has slowed down by 15%. “Such a weakening of the AMOC has not been observed for more than 1,000 years,” said Niamh Cahill, a mathematician at the University of Maynooth in Ireland who participated in the study.
In general, scientists have recently been monitoring this natural system. Direct observations began only in 2004. So how did European researchers learn about its distant past? The used the indirect ways.
The planet is full of natural archives that contain information for decades and hundreds of years. Take at least the annual rings of trees. They can “tell” not only about the age of the tree but also about the weather conditions in which it grew at one time or another. For example, warm and humid years leave wider rings, and cold and dry – on the contrary, thin.
Of course, in this case, European researchers did not look at trees. Information about bottom sediments and ice cores from Greenland helped to look into the past. In addition, they predicted how the Atlantic current system will work in the coming years. Scientists predict an intensification of the trend that emerged the century before last. According to Stefan Ramstorf, a climatologist and initiator of the AMOC study, by 2100 it will slow by 34-45%.
Song of water and salt
Our planet functions as a well-balanced system, manifested, for example, in the distribution of heat. It is larger near the equator, as this region receives more sunlight, but it is not delayed there. The heat goes north to the colder poles, and from there to the south goes the cold. The atmosphere is largely responsible for such heat transfer, but ocean current systems, including AMOC, are also involved.
The Atlantic meridional circulation is compared to a conveyor belt, which is driven by the difference in density and salinity of water in different parts of the ocean. The flow of warm saltwater moves from the equator to the north, towards Greenland. There it cools, becomes denser and heavier, due to which it sinks deeper under the surface of the ocean and goes back south.
Recently, the work of this mechanism is hampered by global warming. Because of it in Greenland, ice melts, and this process is quite intense. In 2019 alone, the white island lost 532 billion tons of ice. As a result, so much water got into the ocean that it could flood the whole of California with a layer 1.25 m thick.
But the problem lies not only in the enormous volumes but also in the fact that this water is fresh. Once in the ocean, it dilutes the salt. As a result, the density of water near the surface decreases, the AMOC “tape” becomes harder to dive into the ocean, and it slows down. But what can it lead to?
The study authors note that the slowdown in circulation will have consequences for both North America and Europe. In the New World, this could raise sea levels, which will significantly affect the east coast of the United States. On the other side of the Atlantic, a slowdown in circulation will provoke stronger storms in winter and more frequent heatwaves in summer. But that’s not all.
“AMOC models show that there is a critical point of circulation power, after which it will become unstable or break completely,” says Andrew Meyers, Deputy Director of Research at the British Antarctic Survey, an organization that studies the polar regions.
When exactly the Atlantic conveyor reaches the point at which it will stop completely, no one knows for sure. However, previously Stefan Ramstorf suggested that the planet should warm up by 3-4 ° C compared to pre-industrial levels. At the same time, according to Richard Wood, a mathematician who builds climate models in the UK Meteorological Service, this is unlikely to happen in the next hundred years.
If the pipeline stops, the entire North Atlantic ecosystem, in which AMOC plays an important role, will suffer. Moreover, the Northern Hemisphere will be much cooler, which will be especially felt by residents of Western Europe and the eastern United States. According to Wood, the temperature drop can reach 5° C.
However, this is not all. The fact is that in the Earth’s climate system there are critical elements, changes in which can affect the entire planet. For example, such an element is the Amazon rainforest. Today, they absorb much of the CO₂ produced by mankind. But deforestation, which is called the “lungs of the planet”, can turn into a fire-hazardous savannah, which, in turn, will pollute the atmosphere with carbon dioxide.
Such critical elements are interconnected, and the collapse of one can strike another. This is exactly the case with the Atlantic meridional circulation. According to the UN Intergovernmental Panel on Climate Change, its destruction could lead to a change in the characteristics of El Niño, the extinction of the Amazon rainforest, and the reduction of the western Antarctic ice sheet. All this can exacerbate the effects of global warming.
However, UN experts see this prospect as a worst-case scenario, in which, moreover, there are many gaps, as much of the response of natural systems, such as AMOC, to global warming remains unclear. However, it should not be discounted.
Stopping the Atlantic conveyor belt is another part of the picture called “global warming”. Maybe this phenomenon is not quite clear yet, but it’s already obviously gloomy. Unlike the source of the fountain of youth, it is quite real. You can’t believe it or not. You can only fight not to see it completely and without jewelry.
Notes: El Niño mentioned in the text is irregular fluctuations in winds and water surface temperature in the equatorial part of the Pacific Ocean, which significantly affects the climate of the tropics and subtropics.
You can read about El Niño and La Niña as major – but not the only – drivers of the Earth’s climate system, in our news compilation.Read also the explanation of a widespread myth that human beings cannot “move” such a colossus as “the Earth’s climate system”.