The world’s attention has once again turned to the remote and icy waters near South Georgia Island, where the once-mighty A23A iceberg—long regarded as the planet’s largest and most enduring floating slab of ice—is now rapidly disintegrating. Scientists tracking its decline say the megaberg, which broke away from Antarctica’s Filchner–Ronne Ice Shelf nearly four decades ago, is splintering into smaller and smaller fragments, and its days as a record-breaking behemoth are numbered.
“It’s an interesting thing to watch, certainly not unprecedented,” University of Colorado ice scientist Ted Scambos told the Associated Press, reflecting on the spectacle of A23A’s demise. “But every time these happen, it’s sort of a big spectacular event.” His words carry the weight of experience, as the world has seen several such giants come and go—but few with the longevity and drama of A23A.
The story of A23A began in 1986, when it calved from the Filchner–Ronne Ice Shelf along a crack ominously dubbed the “Grand Chasm”—a rift scientists had been eyeing since the 1950s. At the time, the iceberg’s sheer scale was staggering: it covered 3,672 square kilometers (1,418 square miles), slightly larger than Rhode Island, and weighed in at a jaw-dropping one trillion tons. For over thirty-five years, it hovered near the Antarctic continent, largely stationary and unremarkable, until recent years set it adrift on a journey north.
According to Andrew Meijers, an oceanographer at the British Antarctic Survey (BAS), A23A’s odyssey has been anything but smooth. In 2020, ocean currents swept the iceberg away from its icy birthplace, only for it to become ensnared in a Taylor column—a swirling vortex of water created by currents colliding with an underwater mountain. It remained trapped until December 2024, when it finally broke free. The following March, it ran aground on a continental shelf near South Georgia, before floating loose again in May 2025.
Since then, A23A has been caught in the powerful grip of the Southern Antarctic Circumpolar Current Front (SACCF), a strong current jet that whips around South Georgia Island. “The iceberg is rapidly breaking up, and shedding very large chunks, themselves designated large icebergs by the US national ice centre that tracks these,” Meijers told CNN. NASA satellite images from Thursday reveal the dramatic pace of this fragmentation, with new bergs—named A23D, A23E, and A23F—splintering off in just a matter of days.
Earlier this year, A23A was still the size of Rhode Island. Now, its area has shrunk to about 1,700 square kilometers (656 square miles), roughly equivalent to Greater London or Houston. The world’s largest iceberg title has since passed to D15A, which, at around 3,000 square kilometers (1,158 square miles), is nearly twice the size of A23A’s shrunken remains and currently sits near Australia’s Davis base, according to Meijers. “A23A currently still holds the title of the world’s second-largest iceberg, but this is likely to rapidly change as it continues to fragment in the coming weeks,” he predicted.
What’s driving this spectacular breakup? The answer lies in a combination of natural forces and, increasingly, the fingerprints of climate change. “It’s still quite thick, but it’s a lot thinner than it was when it left the continent,” Scambos explained. “And so now it’s being flexed by long period waves, by tides, which sweep across the area. And with that flexing, even though it’s incredibly gentle and subtle, it’s finding weak spots in the iceberg, and those are breaking off.” Meijers expects the fracturing to accelerate as the southern spring advances, with warmer water temperatures hastening the process. If A23A somehow survives spring, the Antarctic summer ahead promises even harsher conditions—potentially causing the berg to collapse “sort of like an avalanche that’s floating,” Scambos said, possibly disintegrating in a single day.
Despite the drama, scientists reassure that the breakup of floating ice shelves like A23A will not directly raise sea levels, since the ice is already displacing ocean water. However, the broader implications are more troubling. As ice shelves shrink, the land-based glaciers behind them can flow more freely into the ocean, contributing to sea level rise over time—sometimes by several feet, according to the Associated Press.
The saga of A23A is not unique. Other megabergs, such as A68 in 2021 and A76 in 2023, also met their end near South Georgia, succumbing to the region’s warmer waters and relentless currents. Yet A23A has outlasted them, holding together for decades longer than most of its peers. “It has been following a similar fate to other megabergs,” Meijers noted, but its longevity has offered scientists a rare opportunity to study the life cycle of these icy giants up close.
Indeed, the British Antarctic Survey’s polar research ship, the RRS Sir David Attenborough, visited A23A while it was grounded on the South Georgia shelf. Samples taken during the expedition have been returned to the UK for analysis. “The grounding and enormous release of cold freshwater are likely to have had a major impact on organisms on the seabed and in the surrounding water,” a BAS spokesperson told CNN. “It is important to understand these impacts as large icebergs may become a more common feature at South Georgia as a result of global warming.”
Iceberg calving—the process by which chunks of ice break off from a glacier or ice shelf—is a natural phenomenon that has occurred for centuries. Scientists like Meijers caution that, while there is no definitive evidence that the frequency of megabergs is increasing due to global warming, the loss of trillions of tons of ice from Antarctic shelves in recent decades is well documented. Much of this loss, they say, is driven by warmer ocean waters and shifting currents—trends linked to human-caused climate change.
What does the future hold for A23A and its kin? As the southern hemisphere’s spring gives way to summer, the prospects for the world’s former largest iceberg look grim. “I expect its fracturing will accelerate,” Meijers said. Soon, the once-colossal berg may break into pieces too small to track, lost amid the churning waters of what scientists call “iceberg alley.” If that happens, the world will have witnessed the end of an era—one that stretched from the icy stillness of Antarctica to the turbulent seas near South Georgia, and that now serves as a stark reminder of the planet’s changing climate.
For now, A23A’s fading presence on the ocean’s surface is a testament both to the relentless power of nature and to the mounting pressures of a warming world. As scientists continue to analyze the environmental impact of its journey and demise, the lessons drawn from this icy giant may prove crucial in understanding—and preparing for—the changes yet to come.
