The story of one of the world’s oldest icebergs is nearly at an end, after a breathtaking 40-year journey that has captivated scientists.
The iceberg, known as A23a, was once the largest on Earth, covering an area more than twice the size of Greater London, according to BBC.
But after a path full of twists and turns, A23a has melted, fractured and spectacularly disintegrated over the past year.
Now, far from the icy seas of Antarctica, what’s left of A23a is being eaten away by warmer waters. It’s in its death throes, not expected to last more than a matter of weeks.
All icebergs melt eventually, but scientists have been looking at how it's disintegrated for clues about how other parts of Antarctica might respond as the climate changes.
“It’s been an extraordinary journey,” said Prof Mike Meredith of the British Antarctic Survey in Cambridge. “But it is on its last legs now.”
This is the story of A23a’s final months.
But first we have to go back to 1986. That year, a nuclear reactor exploded at the Chernobyl power plant in what is now northern Ukraine, Gary Lineker won the golden boot at the Fifa World Cup in Mexico, and Whitney Houston received her first Grammy award.
Away from the world’s gaze, the Filchner Ice Shelf - a massive floating tongue of ice extending from the Antarctic continent and into the Weddell Sea - was changing dramatically. One of the icebergs to break off - or calve - was A23a, then about 4,000 sq km.
It soon became anchored in the muds of the Weddell Sea, where it remained stuck for more than 30 years. It wasn’t until 2020 that scientists noticed signs that A23a was on the move again.
While it’s likely icebergs have lived longer in the Earth’s distant past, A23a is thought to be the oldest iceberg in the world today, at least among those picked up by satellites and tracked by scientists.
“Its journey is really pretty impressive, just for sheer longevity,” said Dr Christopher Shuman, a retired scientist formerly with the University of Maryland, Baltimore County, in the US. He likens tracking its path to watching a TV drama “where you don't know what you're going to see next.”
As A23a moves across the vast South Atlantic Ocean, it can be hard to grasp its scale - but if you could drop it into the English Channel its size would be much more striking.
At the start of 2025 - even after 39 years - A23a was still a collosus. It would have almost stretched between the Isle of Wight and Normandy in France. Now, it wouldn’t even reach halfway from Dover to Calais.
“To watch it be so stable for so long, and then just disintegrate over one year, has been fascinating,” said Dr Catherine Walker of the Woods Hole Oceanographic Institution in the US, who was born the same year as A23a.
Over the past two weeks A23a has been carried by ocean currents in a near-complete clockwise loop. This could be its final dance.
Recent satellite images suggest further hydrofracturing of what was left of it - “tantalizing evidence of sudden disintegration”, according to Prof Adrian Luckman of Swansea University.
While other icebergs have travelled further in the past, A23a is the furthest north of any Antarctic iceberg being tracked by scientists today. It’s closer to the equator than London.
The prolonged exposure to sea warmth means the berg’s remains will inevitably fragment and eventually melt away, even though the Southern Hemisphere winter is on the horizon.
By 5 March, A23a had shrunk to approximately 180 square km, although estimates can vary slightly.
Once it gets to roughly 70 square km, scientists will stop tracking it. That moment’s not far away, according to Luckman.
“All traces will probably have disappeared in a matter of weeks now, at most,” Luckman said.
