(ORDO NEWS) — Scientists have elucidated the mechanism of the weakening of the Atlantic meridional circulation. An article about this was published in Nature Communications.
The Atlantic Meridional Circulation (AMOC) is a system of currents in the Atlantic Ocean that is driven by differences in temperature, salinity, and water density across its various regions.
The most famous current in this system is the Gulf Stream. AMOC is one of the main regulators of the Earth‘s climate, which ensures heat exchange between waters in tropical, temperate and subpolar latitudes. At the moment, this mechanism is seriously weakened due to global warming.
Cristiano Chiessi from the University of São Paulo and his colleagues decided to find out the reason for this. It is known that AMOS has already been violated in the past, approximately 71,000 and 12,000 years ago.
The authors of the work studied sediments on the ocean floor and found that in past epochs, icebergs broke off from North American glaciers and floated to the Atlantic (icebergs carried with them fragments of the mainland, which scientists discovered).
The huge volume of fresh water added by melting icebergs has changed the composition of the ocean at high latitudes in the northern hemisphere. This has had a huge impact on the global climate because the region between Canada and Greenland is a particularly sensitive part of the AMOC.
It was with the increase in the number of icebergs that the warming of water and the violation of circulation were associated. “This giant conveyor carries lighter, warmer surface waters from the South Atlantic to the North Atlantic.
In the high latitudes of the North Atlantic, this surface water gives off heat to the cold atmosphere, becomes heavier, and sinks down the water column.
Deeper, colder, denser water then flows south again until it reaches the vicinity of Antarctica, where it returns to the surface due to intense upwelling. On the surface, it heats up, loses density and completes circulation,” the scientists explain.
The process, apparently, begins with a slight weakening of AMOS, causing subsurface warming of water in the high latitudes of the North Atlantic. This warming is melting the sea portions of the glaciers, rapidly moving the ice out to sea and unleashing armadas of icebergs.
As icebergs melt, the salinity of surface waters in the region decreases. As a result of low salinity, the surface layer becomes too dense to sink, and therefore AMOC is destroyed.
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