This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: According to a new study led by researchers from Brazil and Germany, the main system that transports heat from one end of the Atlantic Ocean to the other may undergo sudden changes in intensity driven by climate change similar to what we are experiencing now, even when it is already weakened. The Atlantic Meridional Overturning Circulation (AMOC) is a vast system of ocean currents that functions as a conveyor belt for heat across the Atlantic.
It carries warm water from equatorial and tropical regions to high latitudes in the North Atlantic. This helps regulate the climate in both hemispheres by moderating temperatures in Europe and parts of North America. It also influences rainfall patterns in intertropical regions of Africa and South America.
Global warming has gradually weakened the AMOC, and researchers have warned for decades about the risk of the circulation reaching a critical threshold that would trigger an abrupt slowdown and radically alter the climate in various regions of the planet. Previous research indicated that the circulation could remain in this weakened, relatively stable state for thousands of years. However, a new study shows that the AMOC may be much more dynamic than previously thought, indicating that society needs to prepare not only for abrupt climate change but also for a series of such changes.
The study, led by Cristiano Mazur Chiessi of the School of Arts, Sciences, and Humanities at the University of São Paulo (EACH-USP) in Brazil and Stefan Mulitza of the University of Bremen in Germany, found evidence of two episodes of significant AMOC intensification between 17,800 and 14,800 years ago. During this period, known as "Heinrich Stadial 1," the circulation was, for the most part, much weaker than it is today. However, the analysis of marine sediments by the German–Brazilian team concluded that the AMOC experienced two abrupt surges in intensity during this time: one lasting from 16,500 to 15,800 years ago and a shorter one lasting about 100 years around 15,400 years ago.
During the latter episode, the AMOC's intensity even exceeded its current level. These results were published in the journal Nature Communications. "This is the first time it's been shown that the AMOC can experience bursts of strengthening during periods when it's weakened," says Chiessi, a specialist in paleoceanography and paleoclimatology (sciences that study the past of the ocean and climate).
"As one of the article's reviewers wrote, this completely changes the way we understand the Atlantic Meridional Overturning Circulation." The main driver of the AMOC is the sinking of cold, salty water off the coast of Greenland. This deep water then flows southward and returns to the surface primarily in the Antarctic Circumpolar Current, where strong winds promote upwelling. Surface currents then carry some of this water back north, completing the circuit.
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