The circulation of the Atlantic Ocean that sustains the gulf current, the meteorological system that brings a warm and mild climate to Europe, is the weakest in more than a millennium and the probable fall of the climate is, according to new data .
A further weakening of the South Atlantic headland circulation (AMOC) could lead to more storms reaching the UK, more intense winters and an increase in harmful heat waves and droughts across Europe.
Scientists predict that the AMOC will weaken even further if global warming continues and could fall by between 34% and 45% by the end of this century, which could bring us closer to a “turning point ”In which the system could become irrevocably unstable. A weakening gulf current would also raise sea levels off the U.S. Atlantic coast, with potentially disastrous consequences.
Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, who co-authored the study published in Nature Geoscience on Thursday, told the Guardian that a weakening of the AMOC would increase the number and severity of storms hitting Britain and they would bring more heat waves to Europe.
He said traffic had already slowed by around 15% and the impacts were being seen. “In 20 to 30 years it is likely to weaken further, and this will inevitably affect our time, so we would see an increase in storms and heat waves in Europe and sea levels will rise on the east coast of the USA, ”he said.
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Rahmstorf and scientists from the University of Maynooth in Ireland and University College London in the UK concluded that the current weakening had not been seen for at least the last 1,000 years, after studying sediments, the nuclei of Greenland ice and other proxy data that revealed past weather patterns. time. The AMOC has only been measured directly since 2004.
The AMOC is one of the largest ocean circulation systems in the world, transporting warm surface water from the Gulf of Mexico to the North Atlantic, where it cools and becomes saltier until it sinks in northern Iceland. , which in turn draws more warm water from the Caribbean. This circulation is accompanied by winds that also help bring a mild, humid climate to Ireland, the United Kingdom and other parts of Western Europe.
Scientists have long predicted a weakening of the AMOC as a result of global warming and have expressed concern that it could collapse completely. The new study found that this point is likely to be decades away, but that high greenhouse gas emissions would bring it closer.
Rahmstorf said: “We risk being unleashed [a tipping point] in this century, and circulation would be reduced within the next century. It is extremely unlikely that we have already triggered it, but if we do not stop global warming, we are increasingly likely to trigger it.
“The consequences of this are so massive that even a 10% chance of causing a breakdown would be an unacceptable risk.”
Research conducted in 2018 also showed a weakening of the AMOC, but the Nature Geoscience paper says this was unprecedented over the last millennium, a clear indication that human actions are to blame. Scientists have previously said that a weakening of the Gulf Stream could cause icy winters in Western Europe and unprecedented changes in the Atlantic.
The AMOC is a large part of the Gulf Stream, often described as the “conveyor belt” that provides warm water from the equator. But the larger weather system would not break completely if ocean circulation became unstable, because winds also play a key role. Circulation has been broken down earlier, in different circumstances, for example at the end of the last ice age.
The Gulf Stream is separated from the lightning current that has helped bring the extreme weather to the northern hemisphere in recent weeks, although, like the lightning current, it is also affected by the increase in temperatures in the Arctic. Typically, very cold temperatures in the Arctic create a polar vortex that keeps a constant stream of air currents keeping that cold air in place. But higher temperatures in the Arctic have caused a faint, wandering ray of lightning, which has helped the cold climate to spread much further south in some cases, while bringing a warmer climate to the north in others. contributing to the extremes of time seen in the UK. Europe and the US in recent weeks.
Similarly, the Gulf Stream is affected by the melting of Arctic ice, which pours large amounts of cold water into southern Greenland, disrupting the flow of the AMOC. The impacts of variations in the Gulf Stream are seen for much longer periods than variations in the stream, but they will also lead to a more extreme climate as the climate warms.
In addition to causing a more extreme climate across Europe and the east coast of the U.S., the weakening of the AMOC could have serious consequences for Atlantic marine ecosystems, disrupting fish and other marine species populations.
Andrew Meijers, the deputy scientific leader of the polar oceans in the British Antarctic Survey, who did not participate in the study, said: “The AMOC has a profound influence on the global climate, particularly in North America and Europe, so that this evidence of a continuous weakening of circulation is new critical evidence for the interpretation of future projections of regional and global climate.
“AMOC is usually modeled with an inflection point below a certain circulation intensity, a point at which relatively stable fall circulation becomes unstable or even collapses. Continuous weakening of the fall means that we risk finding that point, which would have profound and probably irreversible impacts on the climate. “
Karsten Haustein, of the Climate Services Center in Germany, also independent of the study, said the U.S. could be at risk from stronger hurricanes as a result of the weakening Gulf Stream.
“While the AMOC will not collapse soon, the authors warn that the current could become unstable by the end of this century if warming continues unabated,” he said. “The risk of stronger hurricanes on the east coast of the United States has already increased due to warmer ocean waters, as well as possible traffic disruptions in Western Europe.”