The Great Current is Heading for a Collapse

A new study warns that the disappearance of a vital current in the Atlantic Ocean is no longer a low-probability scenario. The Atlantic Meridional Overturning Circulation (AMOC), the Atlantic Ocean's primary current system, is a crucial component of the global climate system. This system transports sun-warmed tropical waters to Europe and the Arctic, where they cool and sink, creating a deep-sea current that returns.

It was already known that the AMOC was at its weakest level in 1,600 years due to the climate crisis. Climate models had previously suggested that a collapse was unlikely before 2100. However, the new analysis examined scenarios where the models were run for longer periods, up to 2300 and 2500. These models suggest that the critical threshold that would make the AMOC collapse inevitable will likely be crossed within the next few decades, but the collapse itself could occur 50 to 100 years later.

The research found that if carbon emissions continue to rise, the AMOC collapses in 70% of models. This figure drops to 37% if emissions remain at moderate levels. Even if a low-emissions future scenario materializes, the AMOC collapses in 25% of models.

If It Collapses, Tropical Rain Belt Will Shift North

Scientists have previously warned that the collapse of the AMOC must be prevented “at all costs.” Such a collapse would shift the tropical rain belt, on which millions of people depend for agricultural production, northward. It would also plunge Western Europe into extremely cold winters and dry summers, adding another 50 centimeters to already rising sea levels.

Prof. Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany, who participated in the study, called the new findings “quite shocking,” adding:

"Because I used to say the probability of the AMOC collapsing as a result of global warming was less than 10%. But now, even in a low-emissions scenario that complies with the Paris Agreement, the probability looks to be 25%."

Rahmstorf emphasized that the figures are not absolute, saying, "We found that the point of no return, beyond which collapse becomes inevitable, will likely be crossed within the next 10 to 20 years. This is a very striking finding and demonstrates why we need to reduce emissions rapidly."

The Climate Crisis Has Created a Self-Feeding Cycle

The study, published in the academic journal Environmental Research Letters, analyzed standard climate models used by the Intergovernmental Panel on Climate Change (IPCC). The scientists' most alarming finding was that, in many models, the threshold that would make AMOC collapse inevitable is expected to be passed within the next decade or two, and that this will occur through self-reinforcing feedback mechanisms.

Air temperatures in the Arctic are rising rapidly due to the climate crisis, causing the ocean there to cool more slowly. Warmer water, being less dense, sinks more slowly to the depths. This slowing causes more rainwater to accumulate in the salty surface waters. This, in turn, makes the water even less dense, further slowing the sinking, creating a self-perpetuating feedback loop.

Another recent study, using a different approach, found that the threshold will likely be reached by the middle of this century. Only a handful of IPCC (Intergovernmental Panel on Climate Change) models have been run beyond 2100. Therefore, the researchers looked at which models run to 2100 showed the AMOC already entering a period of irreversible collapse. The results from this analysis were 70%, 37%, and 25%, respectively.

Professor Stefan Rahmstorf said the models do not include the influx of freshwater from the Greenland ice sheet, which has a further diluting effect on the ocean, and therefore the real risk could be even greater.

As it weakens, it will affect the climate

Dr. Aixue Hu of the NSF National Center for Atmospheric Research in Colorado, USA, who was not part of the study team, called the results significant. But she cautioned:

"It is still very uncertain when the AMOC collapse will occur or when the threshold will be crossed because direct observations of the ocean are insufficient and model results vary."

The study, which suggests the AMOC will not collapse completely this century, was led by Dr. Jonathan Baker of the Met Office Hadley Centre in the UK. Baker noted that the new study emphasized that the risk will increase after 2100, adding the following warning:

"These rates should be treated with caution. The sample size is small, so more simulations are needed beyond 2100. The ocean is already changing, and projections for convective vertical water movements in the North Atlantic are truly alarming. While the AMOC is unlikely to collapse completely, it is expected to weaken significantly, and even this could have serious impacts on European climate in the coming decades. However, the future of the Atlantic circulation is still in our hands."