The circulation of the Atlantic Ocean is heading toward a tipping point, which is “bad news for the climate system and humanity” as the collapse in the system of currents that regulate global climate would be at a speed impossible to adapt to, a new study has found.

The scientists who conducted this research expressed shock at the forecast speed of collapse once the point is reached, even though it is not yet possible to predict how soon that would happen.

In their research, they created an indicator for the breakdown of the Atlantic meridional overturning circulation (Amoc), which is a system of ocean currents that plays a major role in regulating global climate, using computer models and past data.

Amoc, which includes part of the Gulf Stream and other powerful currents, is a marine conveyor belt that carries heat, carbon, and nutrients from the tropics toward the Arctic Circle, cooling and sinking it into the deep ocean, in turn, distributing energy around the Earth and regulating the impact of human-caused global heating.

The research found that the Amoc appears to already be on track toward an abrupt shift, the first for more than 10,000 years, which has dreadful implications for many parts of the world. This is due to the extremely fast-paced melt-off of Greenland's glaciers and Arctic ice sheets as the latter pours freshwater into the sea disrupting the sinking of saltier, warmer water from the south. 

Is an abrupt shift really possible?

Since 1950, Amoc has decreased by 15% and is currently in its weakest state in more than a millennium, according to previous research speculating about a nearing collapse.

One study last year, based on changes in sea surface temperatures, predicted the possibility of reaching the tipping point between 2025 and 2095, which was refuted by the UK Met Office which claimed that large, rapid changes in Amoc were “very unlikely” in the 21st century.

The new paper, published in Science Advances, has simulated changes over a period of 2,000 years on computer models representing the global climate. This revealed that an abrupt collapse over less than 100 years could result from the slow decline. It was based on watching for warning signs in the salinity levels at the southern extent of the Atlantic Ocean between Cape Town and Buenos Aires. 

“This is bad news for the climate system and humanity as up till now one could think that Amoc tipping was only a theoretical concept and tipping would disappear as soon as the full climate system, with all its additional feedbacks, was considered,” revealed the paper, stating that the outcome of this research gave a "clear answer" on the possibility of an abrupt shift. 

What are the consequences?

The research revealed part of the consequences of such a shift, one of which is the sea levels in the Atlantic rising by a meter in some regions, flooding many coastal cities. Another one is the wet and dry seasons in the Amazon flipping, in turn, pushing the already weakened rainforest past its tipping point. In addition, temperatures around the world would fluctuate far more chaotically with the southern hemisphere becoming warmer and Europe cooling dramatically with less rainfall. These changes would hit 10 times faster than now, making adaptation almost impossible.

The paper's lead author, René van Westen, of Utrecht University, stated, “What surprised us was the rate at which tipping occurs,” expressing that “it will be devastating.”

He added that the data piled so far is not enough to indicate when this would happen exactly, stressing, however, that its consequences will be irreversible. 

“We are moving towards it. That is kind of scary,” van Westen stated with concern, then urged, “We need to take climate change much more seriously.”