West Antarctic Ice Sheet is on the verge of COLLAPSING - sparking 13 feet of irreversible global sea level rise, scientists warn

Daily Mail​

2 days ago

Containing around 750,000 cubic miles of ice – enough to fill Wembley stadium nearly 3 billion times – the West Antarctic Ice Sheet is a rich reservoir of precious frozen freshwater.
Now, scientists warn that the vast natural feature is on the brink of a disastrous 'irreversible' collapse.
The collapse would cause a devastating sea-level rise globally over the next few hundred years of 13 feet (4 metres), the experts say.
And it could be triggered with ocean warming only slightly above the rate that we're seeing in the present day.
'As little as 0.25°C deep ocean warming above present-day can trigger the start of a collapse,' said study author David Chandler at Norwegian Research Centre (NORCE).
'With our present-day climate, the transition to the collapsed state will be slow, maybe 1,000 years, but it will likely be much faster if there is additional global warming.'
In a future scenario of sea level rises, cities and towns are flooded more easily, meaning people would have to flee their homes and move further inland.
Other small island nations might be gradually plunged underwater entirely, forcing inhabitants to emigrate.
Ice sheets are masses of glacial ice extending more than 19,000 square miles (50,000 square kilometers).
There are two ice sheets on Earth – the Greenland Ice Sheet and the Antarctic Ice Sheet – and together they contain about 99 per cent of the freshwater on Earth.
As the name suggests, the West Antarctic Ice Sheet is the western segment of the latter – and is more strongly affected by climate change.
And unlike its eastern counterpart, the West Antarctic Ice Sheet largely rests on the sea bed.
In other words, the West Antarctic Ice Sheet is sitting in water – and today this water is getting warmer and warmer due to global warming.
'Both East and West Antarctica have really thick ice – well over 3km (2 miles), even 4.9km (3 miles) at its thickest,' Chandler told MailOnline.
'West Antarctica is important for two reasons; first, if even a small fraction of all that ice melts it will cause devastating sea-level rise.
'Second, the ice sheet itself influences climate, so if you melt some of it, that could cause climate changes even as far away as Europe.'
What is an ice sheet?
An ice sheet is a a layer of ice covering an extensive tract of land - more than 20,000 square miles (50,000 square kilometers).
The two ice sheets on Earth today cover most of Greenland and Antarctica.
During the last ice age, ice sheets also covered much of North America and Scandinavia.
Together, the Antarctic and Greenland ice sheets contain more than 99 per cent of the freshwater ice on Earth.
Source: National Snow and Ice Data Center
The research team – also including experts from academic institutions in the UK and Germany – ran model simulations through the glacial cycles over the last 800,000 years.
During this period, the Earth's climate has switched several times between cold periods known as 'glacials' and warmer periods called 'interglacials'.
Some of these past interglacials were likely warmer than our present-day climate and give a picture of how the vast Antarctic Ice Sheet could respond to future warming.
During interglacials, warm ocean water would have melted and thinned out the floating ice shelves that surround and protect West Antarctic Ice Sheet, leaving it vulnerable.
'In the past 800,000 years, the Antarctic Ice Sheet has had two stable states that it has repeatedly tipped between,' said Chandler.
'One, with the West Antarctic Ice Sheet in place, is the state we are currently in. The other state is where the West Antarctic Ice Sheet has collapsed.'
Because the heat needed to melt ice in Antarctica is supplied mostly by the ocean, the concern now is that warming waters from climate change will tip the West Antarctic Ice Sheet to the collapsed state again.
Ice loss from this 'vast freshwater reservoir' could threaten coastal communities and the global economy if the ice volume decreases by just a few per cent.
Once the ice sheet has tipped to the collapsed state, reversal back to the stable present-day state would need several thousands of years of relatively cool temperatures (at or below pre-industrial conditions).
'Once tipping has been triggered it is self-sustaining and seems very unlikely to be stopped before contributing to about four meters of sea-level rise – and this would be practically irreversible,' Chandler said.
In 2023, experts at the British Antarctic Survey (BAS) said the West Antarctic Ice Sheet will continue to increase its rate of melting over the rest of the century, no matter how much we reduce fossil fuel use.
Even if greenhouse gas emissions are controlled to achieve the best possible scenario, melting of the ice sheet will continue to accelerate this century, at a speed three times faster than during the 20th century, the BAS team found.
If it melts completely, the ice sheet will release enough water to raise sea levels worldwide by 17ft (5.3 metres).
However, scientists say that it is 'only' likely to make them rise by 3.2ft (one metre) by the end of the century.
Antarctica's ice sheets contain 70% of world's fresh water - and sea levels would rise by 180ft if it melts
Antarctica holds a huge amount of water.
The three ice sheets that cover the continent contain around 70 per cent of our planet's fresh water - and these are all to warming air and oceans.
If all the ice sheets were to melt due to global warming, Antarctica would raise global sea levels by at least 183ft (56m).
Given their size, even small losses in the ice sheets could have global consequences.
In addition to rising sea levels, meltwater would slow down the world's ocean circulation, while changing wind belts may affect the climate in the southern hemisphere.
In February 2018, Nasa revealed El Niño events cause the Antarctic ice shelf to melt by up to ten inches (25 centimetres) every year.
El Niño and La Niña are separate events that alter the water temperature of the Pacific ocean.
The ocean periodically oscillates between warmer than average during El Niños and cooler than average during La Niñas.
Using Nasa satellite imaging, researchers found that the oceanic phenomena cause Antarctic ice shelves to melt while also increasing snowfall.
In March 2018, it was revealed that more of a giant France-sized glacier in Antarctica is floating on the ocean than previously thought.