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2 weeks ago
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Melting the West Antarctic Ice Sheet could save the Gulf Stream, a remarkable new study reveals.
The vast icy mass in the southern hemisphere contains around 750,000 cubic miles of ice – enough to fill Wembley Stadium nearly three billion times.
As it melts, the West Antarctic Ice Sheet sends salty water towards the North Atlantic, which helps the water stay dense enough to keep the crucial ocean current moving, the study authors reveal.
However, the scientists stress that in other ways the melting of the West Antarctic Ice Sheet would be a total disaster.
If the ice sheet melted, it would raise sea levels by up to 14 feet (4.3 metres) – causing flooding, fatalities, infrastructure damage and more.
The findings suggest we may have to choose between saving the Gulf Stream (which would stop Europe from entering a deep freeze) and saving the West Antarctic Ice Sheet (which would prevent global flooding).
According to study author Dr Sacha Sinet, climate scientist at Utrecht University, which terrifying scenario is worse is 'hard to tell'.
Ultimately, reducing greenhouse gas emissions might be the only way to save both the Gulf Stream and the ice sheet – and avoid both eventualities.
There are two ice sheets on Earth: the Greenland Ice Sheet in the Northern Hemisphere and the Antarctic Ice Sheet in the Southern Hemisphere (divided into east and west). According to the study's findings, melting of the West Antarctic Ice Sheet could keep the AMOC from collapsing
The Gulf Stream is only a small part of a much wider system of currents, officially called the Atlantic Meridional Overturning Circulation or AMOC.
A 'conveyor belt of the ocean', AMOC moves warm water near the ocean's surface northwards – from the tropics to the northern hemisphere.
When the warm water reaches the North Atlantic (Europe and the UK, and the US east coast), it releases the heat and then freezes.
As this ice forms, salt is left behind in the ocean water.
Due to the large amount of salt in the water, it becomes denser, sinks, and is carried southwards – back towards the tropics – in the ocean depths below.
Eventually, the water gets pulled back up towards the surface and warms up ('upwelling'), completing the cycle.
Experts think AMOC brings enough warmth to the northern hemisphere to keep temperatures there relatively mild, so if the AMOC were to slow down or collapse, large parts of Europe and the US could enter a deep freeze.
But according to the Utrecht University researchers, the West Antarctic Ice Sheet is potentially the AMOC's unlikely saviour.
The researchers used a complex computer model, CLIMBER-X to examine how the AMOC would respond to different speeds and timing of ice sheet collapse
Scientists think AMOC brings enough warmth to the northern hemisphere that without it, large parts of Europe could enter a deep freeze. This remarkable satellite picture showing the extent of snow across Britain on January 7, 2010 gives an idea of what this could be like
The world's ice sheets
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.
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.
The team used a computer model called CLIMBER-X to predict what would happen if both Greenland and Antarctica started melting rapidly in the future due to continuing global warming.
CLIMBER-X simulates the response of the Earth to changes in different climate-related factors, such as changes in greenhouse gas concentrations.
Amazingly, the model revealed that the West Antarctic Ice Sheet's melting water didn't always increase the risk of an AMOC collapse.
Under some conditions, such as when its melting was rapid and began to slow down as Greenland's melt peaked, it could prevent a total collapse.
The effect happens because Antarctic meltwater changes how layers of water behave in the Southern Ocean, which eventually sends slightly saltier water toward the North Atlantic.
Over time, this helps the water stay dense enough to keep the AMOC moving, at least according to the computer model.
Previous studies have already shown that melting of the Greenland Ice Sheet destabilises the AMOC. When its meltwater pours into the North Atlantic, it can slow down or stop the sinking of dense water that helps drive it.
Amazingly, the study, published in Science Advances, seems to suggest the opposite for West Antarctic Ice Sheet.
An ice sheet is a mass of glacial land ice extending more than 50,000 square kilometers (20,000 square miles). The West Antarctic Ice Sheet is the western segment of the Antarctic Ice Sheet - and is more strongly affected by climate change
'Greenland melt generally destabilises the AMOC, whereas, as we have shown, West Antarctic Ice Sheet's melt may, under certain conditions, stabilise it,' Dr Sinet told the Daily Mail.
However, if the timing is wrong, such as if the West Antarctic Ice Sheet's melt peaks too late or is too slow, its stabilising effect vanishes.
In fact, the West Antarctic Ice Sheet's meltwater could even accelerate the AMOC's tipping point.
Dr Sinet stressed that greenhouse gas emissions need to be curtailed to avoid both collapse of the AMOC and melting of the West Antarctic Ice Sheet.
But the new findings may be helpful to understand the nuances of a warming world.
'If emissions remain too high to preserve the stability of key tipping elements, then understanding whether the AMOC collapses or not becomes essential for anticipating the climate impacts that societies will need to prepare for,' he told the Daily Mail.
'The important distinction is that the Greenland effect is well established and broadly accepted, whereas the influence of West Antarctic melt remains poorly understood and lacks consensus, and will likely continue to be debated for some time.'
How does global warming affect global currents?
Scientists think melting glaciers could cause the collapse of the Atlantic Meridional Overturning Circulation or AMOC, the system of ocean currents.
Described as 'the conveyor belt of the ocean', the AMOC transports warm water near the ocean's surface northwards – from the tropics up to the northern hemisphere.
When the warm water reaches the North Atlantic (Europe and the UK, and the US east coast), it releases the heat and then freezes. As this ice forms, salt is left behind in the ocean water.
Due to the large amount of salt in the water, it becomes denser, sinks, and is carried southwards – back towards the tropics – in the depths below.
Eventually, the water gets pulled back up towards the surface and warms up in a process called upwelling, completing the cycle.
Scientists think AMOC brings enough warmth to the northern hemisphere that without it, large parts of Europe could enter a deep freeze.
Prior studies have already shown that due to climate change, the AMOC is weakening (meaning the movement of heat is slowing down)
The engine of this conveyor belt is off the coast of Greenland, where, as more ice melts from climate change, more freshwater flows into the North Atlantic and slows everything down.
Why could the AMOC collapse?
Scientists think melting glaciers could cause the collapse of the AMOC, the system of ocean currents.
Described as 'the conveyor belt of the ocean', the AMOC transports warm water near the ocean's surface northwards – from the tropics up to the northern hemisphere.
Prior studies have already shown that due to climate change, the AMOC is slowing down.
The engine of this conveyor belt is off the coast of Greenland, where, as more ice melts from climate change, more freshwater flows into the North Atlantic and slows everything down.
