The ominous sign the Gulf Stream is nearing COLLAPSE: One of the ocean's saltiest regions has become 30% less salty - and it could wreak havoc on major circulation systems

One of the ocean's saltiest regions has become 30 per cent less salty – sparking fears the Gulf Stream could be inching closer to a catastrophic collapse. 

The southern Indian Ocean off the southwest coast of Australia has historically been very salty, thanks to the dry conditions in the area. 

But a new study has revealed that over the past 60 years, the area of salty seawater has decreased by 30 per cent. 

Worryingly, experts from the University of Colorado at Boulder say this could have devastating consequences. 

They predict the changes could alter the interactions between the ocean and the atmosphere. 

In addition, the decrease in salinity could disrupt major ocean circulation systems that help regulate climates around the world. 

'We're seeing a large–scale shift of how freshwater moves through the ocean,' said Professor Weiqing Han, lead author of the study. 

'It's happening in a region that plays a key role in global ocean circulation.' 

On average, the water in our oceans has a salinity of around 3.5 per cent. 

However, this varies around the world. 

For example, the southern Indian Ocean off the southwest coast of Australia is particularly salty, while a region stretching from the eastern Indian Ocean into the western Pacific Ocean in the Northern Hemisphere tropics is naturally less salty. 

This difference in salinity creates a giant 'conveyer belt' of ocean circulation, distributing heat, salt, and freshwater around Earth. 

This system, dubbed the 'thermohaline circulation', transports warm, fresh water from the Indo–Pacific toward the Atlantic Ocean, contributing to the mild climate in western Europe.

When it reaches the northern Atlantic Ocean, the water cools, and becomes saltier and denser. 

Eventually, the water sinks, before flowing southward back to the Indian and Pacific oceans, where the system starts again. 

In their new study, the team analysed how the salinity in the southern Indian Ocean has changed over the last 60 years. 

Their results revealed that this patch is becoming less salty at an 'astonishing rate'. 

'This freshening is equivalent to adding about 60% of Lake Tahoe's worth of freshwater to the region every year,' said first author Gengxin Chen.

'To put that into perspective, the amount of freshwater flowing into this ocean area is enough to supply the entire U.S. population with drinking water for more than 380 years.'

So, why is this happening? The researchers carried out computer simulations, and found that changes in local precipitation are not to blame. 

Instead, they say climate change is driving the freshening. 

According to the researchers, global warming is altering surface winds over the Indian and tropical Pacific oceans. 

These wind shifts are pushing ocean currents to channel more water from the Indo–Pacific freshwater pool to the southern Indian Ocean.

'As seawater becomes less salty, its density decreases,' the researchers explained. 

'Because fresher water usually sits on top of saltier, denser water, the surface water and deep ocean water become more separated into layers. 

'These stronger contrasts in salinity between layers reduce vertical mixing, an important process that normally allows surface waters to sink and deeper waters to rise, redistributing nutrients and heat throughout the ocean.'

The Gulf Stream is only a small part of a much wider system of currents, officially called the Atlantic Meridional Overturning Circulation or AMOC. 

Scientists have previously warned that the collapse of the AMOC could be devastating for global weather systems. 

Professor David Thornalley, a climate scientist at University College London said temperatures would plummet if the AMOC collapsed.

'An AMOC collapse could cause more weather extremes, so as well as overall colder–than–average conditions, we also expect that there would be more winter storms caused by stronger westerly winds,' he told the Daily Mail.

'Unfortunately people would die due to stronger winter storms and flooding, and many old and young would be vulnerable to the very cold winter temperatures.'