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CNN The Atlantic Meridional Overturning Circulation (AMOC) -- which the Gulf Stream is a major part of -- helps maintain the energy balance in the Atlantic Ocean. It is often described as a "conveyor belt" that takes warm surface water from the tropics and distributes it to the north Atlantic. The colder, saltier water then sinks and flows south.
A study, published Thursday in Nature and Climate Change, warned of "an almost complete loss of stability of the AMOC over the course of the last century. Researchers say it could be close to a collapse from a strong circulation to a weak circulation, though the threshold for such a collapse is still uncertain.
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Boers added that he himself was surprised by his findings that the AMOC had been destabilized and was "moving toward its critical threshold, at which it could abruptly collapse."
A collapse of the circulation would mean significant cooling in Europe, Beors said, "but maybe more concerning is the effect of an AMOC collapse on the tropical monsoon systems of South America, Western Africa, and India; especially in Western Africa, an AMOC collapse could lead to permanent drought conditions."
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https://www.cnn.com/2021/08/06/world/climate-gulf-stream-collapse-warning-study-intl/index.html