The Amoc brings lukewarm water to the northern tropics near the surface and takes cold water in the opposite direction in the deep ocean
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It is unlikely that a critical ocean current stops before the end of this century, even in the most extreme climatic scenarios, according to new discoveries which undermine the apocalyptic predictions of an imminent catastrophic collapse.
The southern Atlantic reversing traffic (AMOC) transports lukewarm water from the tropics to the north, helping to keep northern temperate Europe. Warming temperatures and an influx of cold water from the melting Arctic ice weaken the current and, scientists fear it, could close it completely. This would plunge oceanic ecosystems into chaos and quickly cool the climate of Europe from several degrees.
Some researchers Say that an irreversible closure of the amoc could occur this century. But this worst scenario is unlikely, says Jonathan Baker at the Met Office of the United Kingdom.
To explore if a complete collapse of the AMOC This century is possible, Baker and his colleagues used 34 climate models to simulate changes made to the Amoc under extreme climate change, with greenhouse gas levels that managed to levels today overnight. The team has also modeled huge volumes of fresh water entering the North Atlantic several times the current Ice Ice rate.
They found that although the Amoc weakens considerably in these two scenarios, the current of the ocean would continue in its weakened state, supported by deep waters of the North Atlantic trained by winds in the southern ocean. “The winds in the south of the ocean continue to blow and this pulls the deep waters to the surface, which acts as a powerful pump,” explains Baker. “It makes the Amoc operate this century in the models.”
The results help to explain why climatic models generally simulate a more stable Amoc in a world of warming in relation to research based on statistical methods, which tend to suggest that the Amoc is more fragile.
Niklas Boers At the Potsdam Institute for Climate Impact Research in Germany, the results are “good news” for those who are worried about the collapse of the imminent Amoc. “All ultramodern climatic models agree not to show a complete collapse of the Amoc in the 21st century – due to the stabilization mechanisms induced by the Southern Ocean,” he said.
But although the models do not provide for a complete collapse of the Amoc, they show that the concentrations of CO2 quadrules would cause a significant reduction in the strength of the current, from 20 to 81%.
If the Amoc weakens about 50%, the effects on the climate would be significant, known as Baker, with a disturbance of marine ecosystems, an increase in sea level on the Côtes de la Atlantique Nord and changes in world precipitation patterns with an impact on crop yields in the world. But this type of weakening would not provide rapid cooling to Europe, he says.
In comparison, an Amoc is 80% lower than today would have catastrophic effects, underlines the Boers. “It is of course an almost closed Amoc,” he says. “This will give all the impacts in terms of cooling in Europe and change of tropical monsoon models and everything that worries us.”
Stefan Rahmstorfwhich is also located at the Institute of Research on the Impact on Climate in Germany, the world could end up with a weak and shallow amoc current this century under extreme warming. Some studies even define a collapse of the Amoc as this type of substantial weakening, he says, rather than a total stop of any circulation. “The new study is studying in more detail the (current) overthrow of the remaining wind, which is a precious contribution to scientific literature,” he said. “However, this does not modify the assessment of the risk and the impact of future Amoc changes in response to global warming caused by humans.”
