The world’s largest iceberg, known as A23a, is now nearing the end of its life – 40 years after it broke off the edge of Antarctica. This “megaberg” was once more than twice the size of Greater London and around the same size as Rhode Island, weighing a little under a trillion tonnes.
At one point, A23a even briefly threatened penguin feeding grounds on the remote South Atlantic Ocean island of South Georgia. However, the megaberg is now splintering into smaller pieces and is unlikely to survive through the end of November. According to University of Colorado ice scientist Ted Scambos, it may face a sudden and spectacular collapse, like an avalanche of ice at sea. “It’s an interesting thing to watch, certainly not unprecedented,” Mr Scambos explained to AP News. “But every time these happen, it’s sort of a big spectacular event.”
A23a first broke away from Antarctica’s Filchner–Ronne Ice Shelf in 1986 along a massive crack that scientists first noticed in the 1950s and called “the Grand Chasm.” It then floated close to the world’s southernmost continent for around three-and-a-half decades, grounded in the seafloor of the Weddell Sea, until it broke free in 2020 and began to drift northwards in late 2023.
Then, in August last year, it got stuck again, spinning in an ocean vortex known as the Taylor Column. In March, it became grounded 40 miles off the coast of South Georgia.
The iceberg has already created smaller chunks named A23D, A23E and A23F. NASA satellite images from last week have shown that the smaller bergs were still attached to A23a just a few days earlier.
“It’s drifted so far north, it’s in a place where icebergs this size can’t survive,” Mr Scambos explained, adding that this is part of the normal life cycle of icebergs – something that has been occurring for thousands of years and does not appear to be part of climate change.
“It’s still quite thick, but it’s a lot thinner than it was when it left the continent,” he continued. “And so now it’s being flexed by long period waves, by tides, which sweep across the area […] It’s finding weak spots in the iceberg, and those are breaking off.”
“I expect its fracturing will accelerate,” added Andrew Meijers of the British Antarctic Survey, who predicts that by the end of the season, A23a will likely rapidly fall apart as it moves further north.
Mr Scambos added that if the iceberg survives the Antarctic spring, the summer could be even more brutal, with the possibility of it falling apart in a single day.
The world’s new biggest iceberg is D15A, which is nearly twice as big as the shrunken A23a, according to Mr Meijers.