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The oceanic circulation system in the Atlantic, a crucial element in the regulation of the planet's climate, has weakened by about 15-20 percent compared to 1850, and is currently at its lowest in the last 1600 years. If the trend continues, weather conditions in a large region - including Europe, North Africa and the Sahel belt on one side of the ocean, and the northern coast of the United States - will be significant changes. 

This is the conclusion reached by two separate researches - both published in "Nature" - conducted first by researchers at the University College of London and the Woods Hole Oceanographic Institution, in the United States, and the second by scientists from the Potsdam Institute for climate research in Germany and Princeton University.

<center> ![](https://cdn.pixabay.com/photo/2013/06/19/07/08/globe-140051_1280.jpg)
[Credits Pixabay](https://pixabay.com/en/globe-earth-water-wave-setting-140051/) </center>
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The ocean water circulation system, also called thermohaline circulation, has a fundamental role on the global climate: in particular its Atlantic branch, which is one of its main engines. In fact, the currents push warm and salty water from the Gulf Stream towards the North Atlantic, where it releases heat to the atmosphere and warms Western Europe. The colder water then descends to great depths and travels back to the Antarctica to finally return to feed the Gulf Stream. 

But the melting of the Arctic sea ice and the glaciers surrounding the Arctic pours a huge amount of freshwater into the North Atlantic. This inflow of fresh water reduces the salinity of surface seawater, making it lighter and less likely to sink deeper, thus slowing down the system.


The [first study](https://www.nature.com/articles/s41586-018-0007-4?error=cookies_not_supported&amp;code=7f36b424-9bbb-4925-82b9-9027a48165b8) David Thornalley and colleagues have reconstructed the historical evolution of these Atlantic currents on the basis of paleo-oceanographic, obtained mostly by sediment coring, and have come to the conclusion that the Atlantic currents have begun to weaken compared to previous eras starting from the end of the so-called "little ice age". 

In the [second study](https://www.nature.com/articles/s41586-018-0006-5?error=cookies_not_supported&amp;code=fed20173-e92b-47e7-ab99-9251d25d4f2b) , based mainly on the reconstruction of sea surface temperatures in historical periods on climate models, Levke Ceasar and colleagues concluded that this weakening would have largely occurred since 1950, in direct correlation with the increase in levels of carbon dioxide in the atmosphere. 

As noted [in a commentary to the articles](https://www.nature.com/articles/d41586-018-04086-4?error=cookies_not_supported&amp;code=23cc693d-ad19-4a57-b04e-389ad9205c75) Summer K. Praetorius, of the US Geological Survey in Menlo Park, 
>"it is reassuring, at least from the scientific point of view, that the two studies converge on the conclusion that the global circulation system is in a state relative weakness "

Despite the different reconstruction of the timing of the phenomenon, due to the limits present in both the methods adopted. 

However, concludes Praetorius, in the context of future climate change scenarios, while Thornalley's study allows ample space for natural climatic fluctuations, the scenario envisaged by Ceasar and colleagues is less reassuring, because it reveals the possibility of considerable changes in climate and climate. precipitation patterns throughout the northern hemisphere.

### References for further Reading 

[Chicago Tribune](http://www.chicagotribune.com/news/nationworld/science/ct-ocean-circulation-climate-change-20180411-story,amp.html)

[Eurek Alert](https://eurekalert.org/pub_releases/2018-04/nnfs-rom041118.php)

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