Climate change has weakened the Gulf Stream system ‘near the tipping point’

Climate change has weakened ocean currents, dropping the Gulf Stream to more than 1,000 years.

Formally known as the Atlantic Meridional Overturning Circulation (AMOC), it is the driving force that brings hot water from the Gulf of Mexico to the United Kingdom.

It is a complex system responsible for mild winters in Western Europe and which also affects rainfall.

The analysis of its strength over time has revealed an unprecedented slowdown over the past century, likely linked to rising greenhouse gas emissions.

Experts warn that by the end of the century it could be so weak that it would reach a tipping point that would lead to devastating weather conditions around the world.

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“The Gulf Stream system works like a giant conveyor belt that transports hot surface water from the equator to the north and sends cold, low-salt cold salt water south again,” says study author Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research PIK .

“It moves almost 20 million cubic meters of water per second, almost a hundred times the Amazon flow.”

Direct data from the AMOC is difficult to obtain, and researchers have gathered information from a variety of proxy sources that are approximately 1,600 years old.

This confirms previous findings of the same team that in 2018 found that ocean current has declined by 15 percent since the middle of the 20th century.

The new study puts this figure in a stark perspective by comparing the winding pace with that of the last one and a half millennium.

Until the 1800s it was relatively stable, but the current slowed down after the so-called ‘Little Ice Age’ ended in 1850.

This was probably not due to the impact of man, because the Industrial Revolution still had to reach full swing.

But by the 1950s, the AMOC had slowed down severely, as large amounts of pollution disrupted its formation.

Increased rainfall and improved melting of the Greenland ice caused by global warming add fresh water to the ocean, which reduces the salinity and density of the water.

This then prevents the hot water that has traveled northward from sinking as it cools, and it breaks the convection cycle, which eventually weakens the flow of the AMOC.

Experts warn that the Gulf Stream system could weaken by as much as 45 percent by 2100, bringing humanity dangerously close to a ‘tipping point’ where the great ocean current becomes unstable.

If that were to happen, the eastern American coast would have a rising sea level and Western Europe would have more extreme weather.

Winters, for example, will be much colder and it is possible that heat waves will occur more and less rain will fall during the summer.

“This work provides a new long-term context and reveals that before the era of human climate change, the revolution of the Atlantic Ocean was relatively stable and stronger than it is now,” said Dr Andrew Meijers, deputy polar science leader at the British Antarctic Survey . , who were not involved in the study.

‘This indicates that the slowdown is probably not a natural change, but the result of human influence.

‘The AMOC has a profound impact on the global climate, and especially in North America and Europe, so this evidence of a continuing weakening of the circulation is a critical new evidence for the interpretation of future projections of regional and global climate.

‘In addition, the AMOC is often modeled as a tipping point under a degree of circulatory strength, a point at which the relatively stable reverse circulation becomes unstable or even collapses.

“The continuing weakening of the turnaround means that we can find the point, which would have a profound and probably irreversible impact on the climate.”

The study was published in Nature Geoscience.