The world’s biggest iceberg, once larger than Rhode Island, has lost nearly 80% of its size since May, according to scientists at the British Antarctic Survey.
The massive ice formation, known as A23a, is rapidly disintegrating as it drifts northeast in the South Atlantic Ocean. The breakup marks the final chapter in a decades-long journey for one of the most notable icebergs ever recorded.
A23a was carried into a strong circular current near South Georgia Island earlier this year. Researchers say the current, known as the Southern Antarctic Circumpolar Current Front, has played a key role in the iceberg’s ongoing collapse.
The US National Ice Center has confirmed that A23a is now shedding enormous fragments, each large enough to be tracked independently.
In January, the iceberg measured roughly 1,418 square miles (3,672 square kilometers) and weighed about 1.1 trillion tons (1 trillion metric tons). By late August, its size had dropped to approximately 656 square miles (1,700 square kilometers), or about one-fifth of its former area.
Rapid decline in size and movement toward breakup
British Antarctic Survey oceanographer Andrew Meijers said A23a is breaking up more slowly than some past icebergs in the same current, but the outcome appears inevitable.
He noted that similar icebergs, such as A68 and A76, disintegrated more quickly after passing near South Georgia Island. With spring approaching in the Southern Hemisphere, warming conditions are expected to accelerate the melting process even further.
The world's biggest #iceberg, codenamed A23a, is rapidly breaking up, and researchers predict that it could shrink to the point of being unrecognizable within weeks, according to the British Antarctic Survey. pic.twitter.com/c55HnJ0D30
— Beijing Daily (@DailyBeijing) September 4, 2025
A23a originated in 1986 when it broke off Antarctica’s Filchner-Ronne Ice Shelf. It grounded soon after in the Weddell Sea, where it remained stuck to the seabed for more than 30 years.
Scientists believe it began moving again in 2020, likely because the ice anchoring it melted. However, it was soon trapped in a swirling ocean feature caused by an underwater mountain.
It finally broke free in December 2024 and was spotted heading toward South Georgia the following month.
Climate change and the future of mega icebergs
Although it remains the second-largest iceberg for now, researchers expect A23a to fall further down the ranks as it continues to fragment.
The title of world’s largest iceberg has since passed to D15a, which spans about 1,160 square miles (3,000 square kilometers) and is currently stationary near Australia’s Davis research station.
A spokesperson from the British Antarctic Survey said climate change may increase the number of large icebergs near South Georgia in the future.
While it’s unclear if more megabergs are forming as a direct result of warming, Meijers noted a rise in iceberg calving from Antarctica. Scientists warn that the continent remains highly vulnerable to rising temperatures.
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