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‘Early warning signs’ the Gulf Stream is weakening because of the climate crisis

Coast of Norway.
A complex system of currents in the Atlantic Ocean which regulate the climate may have lost ‘stability’ (Picture: Getty)

A complex system of ocean currents which regulate Europe’s climate could be at risk because of global warming.

Scientists have warned the natural phenomenon, which includes the Gulf Stream, may have reached a point of ‘almost complete loss of stability’.

New research suggests a big change to Atlantic Meridional Overturning Circulation (AMOC) would have a ‘cascade’ of knock-on effects on the Antarctic ice sheets, tropical monsoon systems and the Amazon rainforest.

The AMOC acts like a conveyor belt carrying warm surface water to the North Atlantic, including from the tip of Florida towards Europe, making it significantly warmer than it otherwise would be.

Experts from Germany’s Potsdam Institute for Climate Impact Research are concerned the climate crisis might cause it to flip from its ‘strong’ to its ‘weak’ mode.

As the Earth warms, huge amounts of freshwater are rushing into the oceans from melting ice caps, disrupting the salinity of the ocean and potentially fundamentally changing the dynamics of its currents.

Researchers said there were early warning signs of a shift to an overall weaker current system in data looking at a range of characteristics of the Atlantic Ocean.

Diagram of the Gulf Stream
The network of ocean currents carries cold and warm water around the Atlantic Ocean, making Europe far warmer than it otherwise should be given its northernly position (Picture: Getty Images/iStockphoto)

The report ruled out a natural fluctuation or straightforward response to global warming as a cause for recent changes, instead concluding the ‘decline may be associated with an almost complete loss of stability of the AMOC over the course of the last century’.

It added: ‘The AMOC could be close to a critical transition to its weak circulation mode.’

The research said the AMOC could be entering a phase known as ‘critical slowing down’ that the Earth’s natural systems enter before their dynamic fundamentally flips to an alternative, stable state.

Grahame Madge, the Met Office’s climate spokesperson, said he didn’t expect the Gulf Stream to collapse this century and said other climate change impacts ‘are going to be a lot more apparent’ in coming decades.

He added: ‘It’s certainly the case that if it were (to collapse) it would be an extremely high impact event, but it is one that at the moment is of relatively low probability.’

Dr David Smeed, of the UK’s National Oceanography Centre, said if man-made global warming was to cause the AMOC to switch, it could be a very long time before it reverted to its strong mode.

He said: ‘If it did flip in to its (slow) state it could take a very long time before it goes back – it could be centuries.

‘The idea of the two states is that when it is in one state its hard to move in to the other, but when it does change, it is very hard to move back.’

The paper, Observation-based early-warning signals for a collapse of the AMOC, is published in the journal Nature Climate Change.

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