Atlantic Ocean circulation nearing ‘devastating’ tipping point, study finds

The Atlantic Meridional Overturning Circulation is weakening and has collapsed in the distant past

The system is being eroded by the faster-than-expected melt-off of Greenland’s glaciers and Arctic ice sheets. These pour freshwater into the sea and obstruct the sinking of saltier, warmer water from the south. Amoc is in its weakest state in more than a millennium, according to previous research.

The paper mapped some of the consequences of Amoc collapse. Sea levels in the Atlantic would rise by a metre in some regions, inundating many coastal cities. The wet and dry seasons in the Amazon would flip, potentially pushing the already weakened rainforest past its own tipping point. Temperatures around the world would fluctuate far more erratically. The southern hemisphere would become warmer. Europe would cool dramatically and have less rainfall. While this might sound appealing compared with the current heating trend, the changes would hit 10 times faster than now, making adaptation almost impossible.

“What surprised us was the rate at which tipping occurs,” said the paper’s lead author, René van Westen, of Utrecht University. “It will be devastating.” 

He said there was not yet enough data to say whether this would occur in the next year or in the coming century, but when it happens, the changes are irreversible on human timescales.