An Atlantic current system that controls sea levels and heat waves is on the brink of collapse

If Atlantic circulation weakens too much, we will see flooded cities, heatwaves and major winter storms

By Matthew Rozsa

Staff Writer

Published February 25, 2021 6:58PM (EST)

Rough Seas (Getty Images)
Rough Seas (Getty Images)

A massive current system that runs deep throughout the vast Atlantic Ocean has an effect on temperatures, climate, sea levels and weather systems around the world. Any disruption to its flow could have rapid and catastrophic effects on the global climate. And a new study has some dreary predictions about the future of the Atlantic Meridional Overturning Circulation, as it is known, and whether it might cease completely in the coming decades.

This comes from a new study published Thursday in the journal Nature Geoscience, which reconstructs the history of the circulating current since about 400 AD. Researchers say that the circulation is now at the weakest that it has ever been in that span. 

But understanding what that means — and whether the circulation will stop — requires a bit of background on how this all works. 

The Atlantic meridional overturning circulation — or "AMOC" for short — can be likened to a series of conveyor belts. The directions of the belts and their "contents" vary: One belt, containing warm water, flows north, cools and evaporates, increasing the salt content in that region of the ocean. As that water becomes colder and heavier it sinks and flows south, creating a second south-moving belt. These belts are connected by regions in the Labrador Sea, the Nordic Sea and the Southern Ocean. They are responsible for bringing mild, warm weather to Europe and keeping sea levels down on the United States' eastern seaboard.

According to the authors of the Nature Geoscience study, AMOC is weakening. The culprit is likely the global climate crisis. As Arctic ice and the Greenland Ice Sheet melt, while rain and snow levels increase, the water that flows north becomes less salty and dense. This, in turn, slows down the extent to which it flows back south and weakens AMOC overall.

The authors of the paper estimate that AMOC could be weakened by about 34% to 45% by the end of this century. If that happened, one could expect massive winter storms, heatwaves and droughts in Europe. In the United States, sea levels could rise to dangerous levels, threatening large coastal cities like New York City, Boston and Miami and creating millions of climate refugees in the process.

Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, who co-authored the study, told The Guardian that "we risk triggering [a tipping point] in this century, and the circulation would spin down within the next century. It is extremely unlikely that we have already triggered it, but if we do not stop global warming, it is increasingly likely that we will trigger it."

These are not the only significant and apocalyptic consequences that will ensue if climate change goes unchecked. There will be more wildfires in the West Coast states and more extreme weather events like massive hurricanes, thunder storms and winter storms. Large sections of the planet will be too hot and dry to inhabit, and it will be more difficult to produce enough food to sustain the human population. As people are forced to live in closer proximity to each other, it is likely that there will be increased conflict, particularly as resource scarcities increase.

By Matthew Rozsa

Matthew Rozsa is a staff writer at Salon. He received a Master's Degree in History from Rutgers-Newark in 2012 and was awarded a science journalism fellowship from the Metcalf Institute in 2022.

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Aggregate Amoc Atlantic Ocean Circulation Climate Change