Ben Kharakh

A twister swallows up the Hollywood sign; a tidal wave sweeps through New York City; and, in the aftermath, highrise apartments are covered in sheets of ice. 2004’s The Day After Tomorrow capitalized on climate fears to deliver a cinematic blockbuster, but the real culprit behind the cinematic calamity, the collapse of ocean currents, may no longer be a work of fiction. Scientists warn that water currents are on the verge of becoming dysregulated, leading to significant global changes in temperature, rising sea levels, and food and water shortages.

The AMOC, which stands for Atlantic Meridional Overturning Circulation, plays a crucial part in stabilizing temperatures worldwide. It takes warm water from the tropics and carries it northwards, where the colder, denser water sinks deep into the ocean and slowly makes its way south.

Science Advances published a research paper on February 9th, 2024 where three Dutch oceanographers identified strong indications that the AMOC is slowing and could even stop flowing entirely. The paper’s lead author René van Westen, of Utrecht University, warned that, “It will be devastating.” London’s average temperature would cool by an average of 18°F, the sea levels along the North American east coast would rise dramatically, and the wet and dry seasons in the Amazon would flip, potentially triggering the forest to hit its own tipping point.

There’s not yet enough data to indicate whether the tipping point will be reached next year or by the end of the 21st century, but, when it does happen, the catastrophe will be impossible to remedy on a human timescale. It may be of some comfort to know that the United Nations’ Intergovernmental Panel on Climate Change, a group of hundreds of scientists, said, with medium confidence, that AMOC will not collapse before 2100.

Danish researchers Peter and Susanne Ditlevsen reached a less optimistic conclusion in 2023. Their paper stated that the AMOC collapse was a matter of if and not when, leading to the disruption of rainfall that billions of people worldwide depend on. India, South America, and West Africa would find their food supply disrupted, while storms and lower temperatures would plague Europe. “I think we should be very worried,” Peter Ditlevsen said. Meanwhile, a separate study published by Nature Geoscience warned that the AMOC was at its weakest point in the past 1,000 years.

It’s only since 2004 that AMOC has been directly monitored, which is not enough time to fully comprehend the full trajectory of current trends. Indirect indicators like salinity levels have been turned to to fill in knowledge gaps.  The paper published in Science Advances used a computer model called the Community Earth System Model, which breaks up the Earth into smaller chunks than previous models, making the predictions more accurate.

The collapse of AMOC, along with the melting of the Greenland ice sheet and the collapse of the boreal permafrost, is one of a handful of key tipping points that, if hit, would signal an onslaught of irreversible changes to Earth’s climate systems.