End of a giant: Trillion-tonne iceberg, twice the size of Greater London, breaks just before 40th birthday

The extraordinary journey of the world’s largest iceberg has finally come to an end. After drifting thousands of miles across the Southern Ocean, A-23A has now shattered into smaller fragments just months before its 40th anniversary. The trillion-tonne megaberg had long fascinated scientists with its size, longevity, and slow-moving voyage.

For decades, the massive iceberg remained nearly unchanged, only to begin a dramatic final chapter marked by melting, fragmentation, and eventual collapse. Its end closes one of the most remarkable stories ever tracked in polar science.



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How did the iceberg begin its journey?

The world’s largest iceberg has finally reached the end of its extraordinary ocean journey, breaking into fragments after nearly 40 years, as per a report by The Daily Mail.

Known as A-23A, the colossal Antarctic megaberg had once weighed close to a trillion tonnes and covered around 1,540 square miles at its peak, making it more than twice the size of Greater London. Its sheer scale and unusual lifespan made it one of the most closely watched ice masses in modern scientific observation.

A-23A first broke away from Antarctica’s Filchner Ice Shelf in 1986. After calving, it remained grounded on the seabed in the Weddell Sea for more than three decades, staying largely unchanged during that period.

For over 30 years, the iceberg barely moved, becoming one of the most long-lasting giant icebergs ever recorded. Its long stillness finally ended in 2020, when it broke free and began a slow drift northward. Over the next few years, it traveled more than 2,000 miles, drawing the attention of scientists around the world who tracked every stage of its movement, as per a report by The Daily Mail.

For a time, it became trapped in a Taylor column, an ocean vortex where water rotates above an underwater mountain. This phenomenon caused the iceberg to spin in place for several months before it was able to continue its journey.

In late 2024, satellite images confirmed that A-23A was once again moving north through the Southern Ocean, reigniting interest in its path.

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What happened during its final months?

The iceberg’s final chapter was marked by rapid deterioration. As it drifted into warmer waters, its massive sides began to erode. Waves repeatedly struck the structure, while warmer temperatures accelerated melting across its surface. By early 2025, concern grew as the iceberg appeared to be moving dangerously close to South Georgia, a remote British territory known for its wildlife, including thousands of penguins and seals.

At one point, it was only 173 miles from the island. Fortunately, instead of directly colliding with the coast, A-23A ran aground in shallow waters off South Georgia in March 2025. It remained stuck there for months while ocean waves and rising temperatures steadily chipped away at it.

As it later moved along the eastern side of the island, the iceberg began to splinter into increasingly smaller pieces. Scientists observed meltwater and slush spreading across its surface, even turning parts of it a vivid blue. Eventually, the once-enormous mass shrank to just over 66 square miles before finally disintegrating completely. The latest image, captured on April 3, showed only tiny fragments remaining, as per a report by The Daily Mail.

Why was A-23A so significant?

A-23A was remarkable not just for its size, but for its extraordinary longevity. NASA described it as one of the giants ever known to calve from Antarctica, noting that while larger icebergs have existed, few have survived for so long. Its journey also had an environmental impact. As it moved through warmer waters, iron-rich meltwater from the iceberg helped fuel phytoplankton blooms, which provided food for local marine ecosystems.

NASA wrote in a blog post, "Iceberg A–23A ranks among the giants known to have broken, or 'calved', from Antarctica. Though several other icebergs in the satellite era have been larger, A–23A was remarkable for its longevity. After spending its early days in the Weddell Sea, its journey came to an end in the South Atlantic Ocean, months shy of its 40th birthday."


At the same time, the same meltwater contributed to its destruction by cutting through the ice and accelerating fractures. Dr Jan Lieser, who tracked the iceberg using remote sensing, reflected on its final days by saying, "I noticed in recent weeks how Mother Nature seemed to keep a veil of clouds over the dying iceberg as if trying to give it some privacy at this stage."

Now, after nearly four decades, only scattered fragments remain of the once-mighty A-23A, bringing one of the most remarkable polar journeys ever observed to a quiet end.

FAQs

How old was iceberg A-23A?
It broke apart just months before turning 40 years old.

Where did it finally disintegrate?
It fragmented after moving through waters near South Georgia in the South Atlantic.