Gulf Stream Collapsing Again!

 The network of ocean currents which keep the Earth's climate stable could be about to collapse, scientists have warned.

In an open letter, 44 of the world's leading climate scientists say that key Atlantic Ocean currents - including the Gulf Stream - are on the brink of failure.

The resulting climate fallout could plunge the UK into a 'new Ice Age', with winter temperatures plummetting up to 15°C below the current average.

While the collapse of the Gulf Stream would be disastrous for Britain, that vital current is just one small part of AMOC's massive global system.

Without urgent action, the scientists warn that AMOC could fail completely within the next few decades.

As warm water travels northwards from the tropics, it hits the sea ice around Greenland and the Nordic countries, cooling and becoming much saltier.

As the water cools it becomes denser, sinking rapidly towards the bottom of the ocean where it flows back southwards before once again warming and rising to the surface.

This process of 'deep water formation' is the engine for a vast global conveyor belt which pumps heat and water all around the Atlantic Ocean.

Studies suggest that AMOC's deep water engine has started to slow and is now showing worrying signs of breaking down altogether.

As global temperatures rise, melting ice pours fresh water back into oceans, diluting the denser salty water and preventing it from sinking.

Oceanographers have been measuring the AMOC continuously since 2004.

The measurements have shown that the AMOC varies from year to year, and it is likely that these variations have an impact on the weather in the UK. However it is too early to say for sure whether there are any long term trends.

All were associated with changes in Atlantic currents and the AMOC. The Warming in the North occurred because of the influx of warm Atlantic seawater, in exactly the same way as with recent Arctic warming.

As the Met Office explain, warm water evaporates leaving saltier water, which sinks because it is more dense.

Saltier water of course freezes at lower temperatures, so Arctic sea ice tends to contract.

As fresh, polar water replaced warmer Atlantic water, salinity levels fell - hence the name given to the event.

Just as Arctic sea ice had retreated during the Warming, it expanded rapidly during this period.

The GSA was not just a phenomenon in the Norwegian Sea, because the polar gyre carried this fresh water around the whole of the Arctic Ocean.

Another factor identified by Dickson and Osterhus in the freshening of the Arctic Ocean is increasing discharge from Eurasian rivers into the basin.

A warming climate means a wetter climate in those regions.

More river discharge leads to more sea ice and a colder Arctic.

Milder weather leads eventually to more sea ice and a colder climate, until eventually the AO flips back to positive again. 

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