Is the Gulf Stream about to collapse? Mysterious ‘cold blob’ in the Atlantic suggests key current is weakening, scientists warn

A mysterious ‘cold blob’ has emerged in the North Atlantic – and scientists say it indicates a critical ocean current is on the verge of collapsing.

While the rest of the Earth’s oceans have grown warmer amid the building El Niño, one patch of sea southeast of Greenland has remained stubbornly chilly.

For decades, scientists have been baffled over why this ‘hole’ is cooling down while everywhere else heats up.

Now, a group of researchers argue that it is because the critical Atlantic Meridional Overturning Circulation (AMOC) is slowing down.

AMOC is a vast network of ocean currents carrying warmth from the tropics to Europe, of which the Gulf Stream is one small part.

However, recent data suggests that human–caused climate change could be driving this system to a tipping point that could trigger its total collapse.

Were AMOC to collapse, it would plunge northern Europe into a ‘new Ice Age’ and trigger famines by disrupting crucial monsoon rains in Africa and Asia.

Lead author Professor Stefan Rahmstorf, of Potsdam University, told New Scientist: ‘Even if, in some modelling approaches, it seems possible that the cold blob is caused by the atmosphere, in fact, the data show it is caused by the ocean.’ 

AMOC plays a crucial role in keeping the planet’s current climate stable by moving heat, nutrients, and carbon around the world.

The ‘engine’ driving this global conveyor belt is the cold, salty waters that form in the North Atlantic around Greenland.

As this dense water sinks towards the bottom of the ocean, warm water from the Tropics is pulled northwards, and the cycle keeps the current moving.

However, scientists are concerned that fresh water from Greenland’s melting glaciers is disrupting this process by diluting the water and making it less dense.

Studies have shown that AMOC has already slowed by about 15 per cent since the mid–20th century due to climate change, and could be driven into total collapse in the future.

Since a slowing AMOC would result in less warm water arriving in the North Atlantic, scientists had suggested that it could be part of the explanation for the cold blob.

However, our direct observations of AMOC only date back around 20 years, which makes drawing a strong connection challenging.

Likewise, other researchers have proposed a competing theory, arguing that the cold blob is actually being caused by changing wind conditions.

In 2022, scientists claimed that the rapid warming in the Arctic has shifted the jet stream over the cold blob region and that these strong westerly winds are drawing more heat out of the ocean.

However, a group of researchers led by Professor Rahmstorf now say they have found strong evidence linking the cold blob to AMOC’s decline.

Instead of using computer–based climate models, the researchers used ‘climate reanalyses’, which are based on direct measurements from satellites, buoys and ships.

They found that surface heat loss has actually decreased in the cold blob since 1995, meaning that the wind is not taking more heat away.

Likewise, they discovered that the cold blob is not just cooling at the surface, but also at 3,280 feet (1,000 m) below the waves.

According to the researchers, this clearly shows that the warming hole is being caused by a change in the way ocean currents distribute heat and not by the wind.

This is vitally important because it would make the North Atlantic cold blob one of the ‘early warning signals’ that AMOC is weakening.

In their paper, published in Geophysical Research Letters, the researchers conclude: ‘Our analysis supports the interpretation of the observed “cold blob” as a sign of a weakening AMOC.’

More immediately, this means that the cold blob could also threaten the ‘subpolar gyre’, a massive swirling current that surrounds the North Atlantic.

This current helps to bring salty water to the surface to feed the process of cooling and sinking that drives AMOC.

However, if the subpolar gyre failed, it would actually cool the UK and northern Europe even faster than a full AMOC collapse.

A recent Parliamentary report warned that the collapse of the subpolar gyre could create 2°C (3.6°F) and 3°C (5.4°F) of cooling over the North Atlantic, threatening the viability of agriculture in the UK.

Professor Rahmstorf warns: ‘The subpolar gyre passing this tipping point could already lead to serious climate impacts in western Europe as early as in the 2040s’