The real-life Day After Tomorrow? The Gulf Stream is weakening thanks to climate change - and it could plunge Europe into a deep freeze if it collapses, scientists warn

Back in 2004, The Day After Tomorrow might have seemed like nothing more than another far-fetched climate disaster flick.

But scientists warn this film might soon become a reality, as a new study shows that climate change could plunge Europe into a deep freeze. 

Researchers from University College London have discovered that the Gulf Stream - a vital current of warm water - could be especially sensitive to changes in the climate.

Their research suggests that global warming could lead to the collapse of the Gulf Stream, which would drop temperatures in Europe by up to 15°C (27°F).

Lead researcher Dr Jack Wharton said: 'If in the future winds are weaker, as shown in a recent study using climate models, it could mean a weaker Gulf Stream and a cooler Europe.'

The Gulf Stream is a current of warm water which flows up the East Coast of North America and across the Atlantic to Europe.

As it arrives, it releases heat energy into the atmosphere, keeping Europe at a higher temperature than it might otherwise be.

Some research has already pointed to a weakening of the patterns of ocean currents which drive our planet's climate.

But to understand how a big shift in climate conditions might affect the Gulf Stream in the future, the researchers had to look far back into the past.

Around 20,000 years ago, the planet was in the grips of the last Ice Age which covered much of the Northern Hemisphere in a thick ice cap. 

However, the researchers now think that Europe might have been kept warm despite the surrounding climate by a particularly strong Gulf Stream. 

Researchers collected sediment samples from locations all along the coasts of North Carolina and Florida to look for the presence of ancient microorganisms called foraminifera.

Co-author, Professor David Thornalley, told MailOnline: 'The fossils of foraminifera that lived during the last Ice Age were used because the chemistry of their shells records the density of the water they lived in when they were alive.'

Because Gulf Stream water is very warm, it is less dense than subpolar water so the researchers could use the density recorded by the shells to work out where the Gulf Stream would have flowed. 

Since this faster current is able to carry larger pieces of material, the researchers also looked at the different sizes of grains in sediment to work out its speed.

Using their measurements and some ocean physics, the researchers calculated that the Gulf Stream was twice as deep and twice as fast as it is today.

Dr Wharton says: 'We found that during the last ice age, the Gulf Stream was much stronger because of stronger winds across the subtropical North Atlantic.

'As a result, the Gulf Stream was still moving lots of heat northwards, despite the rest of the planet being far colder.'

These findings have worrying implications for our future as they suggest the strength of the Gulf Stream is dependent on factors in the climate. 

Professor Thornally told MailOnline: 'The ocean moves vast amounts of heat around the globe - equivalent to the energy from millions of power stations. 

'Changing the strength of ocean currents can therefore alter how much heat goes where. This alters our climate, and on shorter timescales our weather.'

The Gulf Stream itself is just one part of the Atlantic Meridional Overturning Circulation (AMOC), a vast network of currents which pump hot water around the globe.

Although it is often described as a conveyor belt, Professor Thornally says it is better to think of AMOC as 'a series of interconnected loops'.

He adds: 'There is the subtropical loop—that the Gulf Stream is part of—and a subpolar loop, which carries heat further northwards into the Arctic.

'During the last ice age, our findings show that the subtropical loop was stronger than it is today, whereas the subpolar loop is thought to have been weaker.'

One of the biggest concerns is that warming global temperatures will disrupt the engine which drives that subtropical loop.

As ocean water meets ice around Greenland in the sub-polar North Atlantic it rapidly cools, becoming extremely dense and salty.

This causes the water to plunge downwards, pulling hot water in behind it and creating a vast circulation pattern.

But as freshwater from Greenland's Ice sheet melts it is diluting these cold salty waters and making them less dense.

Some studies suggest this could slow down the turnover of the subtropical loop and weaken the Gulf Stream.

Likewise, the authors of this paper point out that recent studies indicate climate change is already weakening the strong North Atlantic winds which help drive the Gulf Stream.

Co-author Professor Mark Maslin says: 'It’s not always recognised how much ocean currents are responsible for transferring heat around the planet and shaping our climate. 

'Paradoxically, the warming of the climate could cool down much of Europe by disrupting the AMOC.'

Although the researchers say they cannot be sure how much of an impact this will have, in the unlikely event of the Gulf Stream's complete collapse temperatures could fall between 10 to 15°C (18-27°F) in Europe. 

The researchers point out that current climate models show a weakening Gulf Stream 'wreaking havoc' on continental agriculture and weather patterns.

And, just like in the movie The Day After Tomorrow, the researchers note this could also lead to rising sea levels across North America. 

Professor Thornally adds: 'Changes in AMOC will also cause sea-level changes around the North Atlantic, with significant increases (tens of centimetres) along the North American east coast. 

'However, even a more modest weakening of AMOC will still alter where heat is being moved around, which will disrupt our normal weather patterns, and is thought to lead to more extreme weather events, including flooding, and heatwaves and droughts.'

This paper has been published in Nature.