 (1).png){kind=spacer}
1 month ago
17
The world's biggest iceberg has turned bright blue, as scientists warn this transformation heralds its imminent disintegration.
The iceberg A-23A first separated from Antarctica's Filchner Ice Shelf in 1986 and has been drifting around the Southern Atlantic ever since.
However, new satellite images taken by NASA show that the former 'King of the Seas' is now covered with meltwater and 'blue slush'.
Experts say these signs suggest one of the largest and longest-lived icebergs now has only days or weeks before total collapse.
At its peak, A-23A boasted an area of around 1,540 square miles (4,000 km squared) - more than twice the size of Greater London.
However, as it drifts through warmer waters between South America and South Georgia Island, known as the 'graveyard' of icebergs, A-23A is rapidly shrinking.
In January, scientists from the US National Ice Centre estimated that A-23A's area had dwindled to just 456 square miles (1,182 square km).
Dr Chris Shuman, a scientist from the University of Maryland, Baltimore County, who has tracked this iceberg his entire career, says: 'I certainly don't expect A-23A to last through the austral summer.'
The world's largest iceberg has turned bright blue, as experts warn that this transformation means the structure could collapse within days or weeks. Pictured: Iceberg A-23A as seen by an astronaut aboard the International Space Station on December 27, 2025
Satellite images captured by NASA's Terra satellite on December 26 show just how extensive the collapse of A-23A has become.
The blue areas show regions where meltwater has collected and pooled on the surface in vast 'melt ponds'.
An astronaut on the ISS captured a closer view a day later, revealing an even larger melt pond than before.
The incredible patterns of blue and white stripes revealed by these pictures are actually striations that were scoured hundreds of years ago when A-23A was still part of a glacier.
As the glacier moved and dragged itself over the ground, it carved deep grooves parallel to the direction of movement that now direct the flow of meltwater.
Dr Shuman says: 'It's impressive that these striations still show up after so much time has passed, massive amounts of snow have fallen, and a great deal of melting has occurred from below.'
These stunning images also show a thin white line extending all the way around the edge of the iceberg.
This 'rampart moat', which holds back the blue meltwater, forms as the edge of the iceberg melts at the water line and bends upwards.
The iceberg A-23A first separated from Antarctica's Filchner Ice Shelf in 1986, but NASA's satellites now show that the surface is covered in meltwater. Pictured: A-23A as seen by NASA's Terra satellite on December 26, 2025
How do icebergs form?
An iceberg is a piece of freshwater ice that has detached from a glacier and is floating in the ocean.
Icebergs form when pieces of ice break off the end of an ice shelf or a glacier that flows into a body of water.
This is called 'calving' and it's a natural process that is responsible for ice loss at the edges of glaciers and ice sheets.
Source: antarcticglaciers.org
However, NASA's satellite image suggests that the rampart wall has now sprung a leak.
In what Dr Shuman describes as a 'blowout', the weight of the water piling up in the melt pools became so great that it punched through the edges and spilt out into the ocean below.
This might be the explanation for the white, dry region on the left side of the iceberg.
Dr Tedd Scambos, a senior research scientist at the University of Colorado Boulder, says: 'You have the weight of the water sitting inside cracks in the ice and forcing them open.'
This is not a good sign for the former largest iceberg on the planet, as scientists predict that its total collapse is likely to come soon.
After being released into the South Ocean in the 1980s, A-23A grounded itself in the shallow waters of the Weddell Sea, where it remained almost unchanged for over 30 years.
After freeing itself in 2020, the iceberg spent several months spinning in an ocean vortex known as the Taylor column, before heading North.
After almost colliding with South Georgia Island and becoming stuck for several months, A-23A finally escaped into the open ocean, where it has been breaking up since 2025.
At its peak, A-23A (pictured) had an area of around 1,540 square miles (4,000 km squared) - more than twice the size of Greater London. The iceberg has been rapidly shrinking since entering the open ocean
After reaching open water at the start of 2025, A-23A has been rapidly shrinking. In July (left), it had an area of 969 square miles (2,510 km squared). In September (right), this had fallen to just 580 square miles (1,500 km squared)
In January 2025, A-23A had an area of roughly 1,410 square miles (3,650 km squared).
However, by September, it had shrunk to just 656 square miles (1,700 km squared), after several large chunks broke away.
A-23A is already in water that is about 3°C (5.4°F) warmer than around Antarctica, and currents are pushing it into even warmer waters in the iceberg 'graveyard'.
Dr Schuman adds: 'A-23A faces the same fate as other Antarctic bergs, but its path has been remarkably long and eventful. It's hard to believe it won't be with us much longer.
'I'm incredibly grateful that we've had the satellite resources in place that have allowed us to track it and document its evolution so closely.'
What are icebergs and why are they important?
Icebergs are pieces of freshwater ice more than 50 feet long that have broken off a glacier or an ice shelf and are floating freely in open water.
Icebergs that break off from an already floating ice shelf do not displace ocean water when they melt - just as melting ice cubes do not raise the liquid level in a glass.
Some icebergs contain substantial amounts of iron-rich sediment, known as 'dirty ice'.
'These icebergs fertilise the ocean by supplying important nutrients to marine organisms such as phytoplankton,' said Lorna Linch, lecturer in physical geography at the University of Brighton.
Icebergs can also pose danger to ships sailing in the polar regions - as demonstrated in April 1912, when an iceberg led to the sinking of RMS Titanic in the North Atlantic Ocean.
Icebergs may reach a height of more than 300 feet above the sea surface and have mass ranging from about 100,000 tonnes up to more than 10 million tonnes.
Icebergs or pieces of floating ice smaller than 16 feet above the sea surface are classified as 'bergy bits', while those smaller than 3 feet are 'growlers'.
