Gulf Stream shutoff could happen this century, scientists warn

The Atlantic Ocean current that keeps large parts of Europe warm could come to an abrupt and catastrophic stop any time in the coming decades, according to a new study published Tuesday.

A collapse of the Atlantic Meridional Overturning Circulation (AMOC) was likely to occur “around mid-century under the current scenario of future emissions” — perhaps as soon as 2025 and not later than 2095, said Peter Ditlevsen and Susanne Ditlevsen from the University of Copenhagen in a peer-reviewed study published in Nature Communications.

Other scientists urged caution in interpreting the findings.

Niklas Boers of the Technical University of Munich, said the modeling was “heavily oversimplified.” The authors of Tuesday’s study themselves admitted they made assumptions that were uncertain. 

AMOC pushes warm water north along the Gulf Stream. As a result, England, which is at the same latitude as Canada, is much warmer.

Its sudden end is a long-standing climate change prediction but there are deep divisions among scientists as to if and when it could happen. There is no disagreement about the consequences if a collapse were to happen.

“A collapse of the AMOC would be disastrous,” said Jonathan Bamber, director of the Bristol Glaciology Centre, who was not involved in the study.

He warned that other “plausible” assumptions in the modeling than those used in the study would lead to “a different conclusion.”

This July is almost certain to be the hottest month ever recorded. Greenhouse gas emissions from burning fossil fuels are causing cold, fresh water to sluice off melting Greenland ice sheets into the North Atlantic, creating a cold blob in the warming ocean. That was behind an observed slowing of the currents that regulate the seas that bathe the European and North American Atlantic coastlines, noted the Ditlevsens’ study.

“This is indeed a worrisome result, which should call for fast and effective measures to reduce global greenhouse gas emissions,” said the pair.

However, the U.N.’s Intergovernmental Panel on Climate Change’s (IPCC) recently found the current was unlikely to suddenly stop this century.

“The work provides no reason to change the assessment of the [IPCC],” said Jochem Marotzke of the Max-Planck-Institute for Meteorology in Hamburg.

If the current were to switch off, said Penny Holliday, head of marine physics and ocean circulation at the U.K.’s National Oceanography Centre, it would transform the global climate.

Much of the Northern Hemisphere would be gripped by freezing temperatures; sea ice would creep south from the North Pole toward Europe. Rainfall would be affected across the planet, drying out some continents and soaking others. 

“This would lead to dramatic change in every nation’s ability to provide enough food and water for its population,” said Holliday.

While a sudden collapse is still seen as unlikely by many scientists, there is broad agreement the current is becoming more erratic. That in itself could have consequences that are poorly understood, said Levke Caesar from the University of Bremen, ranging from worse winter storms in Britain, to harsher heat waves in Europe.

“There is a large number of people who would be affected by a weaker AMOC,” said Caesar.