The extraordinary life and quiet death of the world’s largest iceberg

Antarctica, the immense ice-covered wilderness at the bottom of the world, offers an illusion of permanence: everything literally frozen in place. But every now and then the continent delivers a humbling reminder to the contrary.  

Here’s an example. In the mid-1970s, the Soviet Union established a seasonal research station, Druzhnaya 1, not far from the edge of the Filchner Ice Shelf, which runs off Antarctica into the Weddell Sea, southeast of South America’s tip. For years, Soviet scientists returned to staff it each Antarctic summer, but when they prepared to do so in October 1986, a rather fundamental problem became apparent: They could find no trace of their destination.  

“The station has evidently drifted away on an iceberg that has not been detected so far,” reported the Soviet news agency TASS. “The station could be drifting away on a comparatively small fragment of ice, which turned over and in that case it has been irretrievably lost.” 

But at least in some of the most crucial details, they were mistaken. The continent had only just emerged from the 24-hour-a-day darkness of Antarctic winter, so regular satellite imagery could show nothing of what had happened in the previous months. Only by studying intermittent, low-resolution infrared images, then sending an expedition, did the Soviets come to realize that their error had, in part, been one of scale. Yes, Druzhnaya 1 was on an iceberg—but not one so small that it had tipped over. The station was adrift on a berg that was improbably large. 

In that part of Antarctica, the ice shelf advances toward the ocean at a pace of up to a mile a year, so its edges must eventually break off—a process known as calving—but they do so erratically. Soviet analysts determined that a few months earlier, a prodigious amount of advancing ice, about 40 years’ worth, had broken free and split into three parts. According to naming conventions for large icebergs established several years before, these three new ones were named A22, A23, and A24—the letter identifying the longitudinal quadrant in which they were spotted, the number indicating their order of discovery. Druzhnaya 1 had been set adrift on A23. 

The new icebergs hadn’t yet moved far—they were still just offshore from the ice shelf’s new edge. But the calving had reoriented Druzhnaya 1, exposing it to the worst of the winter weather, and it had been buried beneath snowdrifts. In January 1987 a Soviet landing party helicoptered onto the iceberg and spent two weeks digging out and salvaging the station’s most valuable equipment.  

That’s believed to have been the last time a human stepped upon A23. But it was only the beginning of the iceberg making its presence known to us.  

The expanse of ice that the Soviets left behind would, over the next four decades, find fame as the kind of baffling, awe-inspiring natural wonder that reminds us just how little we understand about our world—even while offering a few of us the chance to learn precious new lessons about it. Right now, the very last remnants of what was, for much of its existence, the world’s largest iceberg, are dwindling away to nothing somewhere in the Southern Ocean. Or maybe they have already; it’s no simple matter to document the death throes of an iceberg, even one that has been monitored as closely as what came to be known as A23a. 

Iceberg stories all end the same way, and maybe that’s part of why these frozen giants can so captivate our imagination. Their inescapable destiny mirrors a classic mythic archetype: that something so colossal is ultimately so fragile in its essence, so helpless to avoid its eventual fate. But they also fascinate us because the path they take from enormity to nothingness can be so unpredictable. A23a was just a gigantic block of inanimate material, subject to the complex interactions of this planet’s relentless chemical, physical, and meteorological forces. And yet there is something about an object like this—with all its apparent capriciousness, stoic immensity, and pure extraordinariness—that irresistibly tempts us to project upon it something more.

In 1991, still not far from its birthplace, A23 split into several pieces, the largest of which was christened A23a. At the time, A23a was at least 44 nautical miles long, 40 nautical miles wide, and somewhere close to 2,000 square miles in area, or roughly the size of Bali. Massive as it was, it was still stuck in the Weddell Sea, tethered by sea ice, its underside lodged on the ocean floor. And for many years, that’s where A23a would remain, with only a few people paying it any attention. 

(Scientists peeked underneath an iceberg and found a startling kaleidoscope of marine life.)

One of them was meteorologist and marine glaciologist Jan Lieser. In the late 1990s, Lieser was a young research scientist wintering at a German Antarctic station. He was tasked with tracking another iceberg, A38, which had just calved and, ironically, taken with it yet another research facility, this one run by the Germans. Lieser took note of A23a lying to A38’s north but didn’t think much about it. He had no idea how much of his attention this gigantic slab of ice would one day command.  

Only in 2020 did A23a finally begin to break free. A July 10 post on the Facebook page of the United States National Ice Center excitedly proclaimed, “A-23A is on the move!” While the iceberg’s southeast corner still appeared to be grounded, the USNIC noted, it had recently rotated some nine nautical miles in a clockwise direction.  

It took more than a year before A23a began drifting in earnest, carried by a current known as the Weddell Gyre. Many icebergs before it had followed the same path, along the eastern side of the Antarctic Peninsula and toward an open-ocean route nicknamed Iceberg Alley. Over two more years it traveled nearly a thousand nautical miles to the northern edge of the sea ice that fills the Weddell Sea. By then, A23a’s area was about 1,500 square miles, still large enough to claim a title it had held intermittently throughout its lifespan: the largest iceberg in the world. 

(See Iceberg Alley, where huge icebergs are driven by sea currents.)  

Up until that point, it was mostly scientists who paid A23a any mind, but its days of relative obscurity ended when the iceberg reached the open water of the Southern Ocean in November of 2023. “World’s biggest iceberg on the move after 30 years,” reported the BBC. “Iceberg Five Times the Size of New York Breaks Away From Antarctica,” announced Newsweek. “S’thern berg quits chillin’,” declared the New York Post. Much of the coverage shared a sense of incredulity, as though the planet had somehow sprung a surprise that no one had been expecting. And while some of the flurry of articles speculated whether climate change played a role in setting A23a adrift, scientists suggested otherwise. “The consensus,” one British Antarctic Survey researcher told the BBC, “is the time had just come.”   

By the time A23a took to the seas, Lieser had become a senior ice specialist at Australia’s Bureau of Meteorology, forecasting the movements of icebergs and sea ice for the shipping industry. As the world’s largest iceberg moved into shipping lanes, he was watching it closely. A23a had already endured far longer than even the largest icebergs typically do—their timespan is usually measured in years, not decades. The first time Lieser wrote about A23a in detail, just before it exited the Weddell Sea, he noted that it was expected to move into the ocean and break into small- and medium-size icebergs. As it headed inexorably toward warmer water, Lieser wasn’t the only scientist with questions: How much longer might A23a last? What path would it take? And what effect might such a gargantuan, slowly melting block of freshwater ice have on the ecosystems through which it traveled?  

In arriving at open water, A23a had also become accessible in a way it hadn’t been for 37 years, reachable by tourist vessels and scientific expeditions. In November 2023, University of Cambridge Ph.D. student Laura Taylor was aboard the British Antarctic Survey’s research vessel, the R.R.S. Sir David Attenborough, studying the biological and chemical interactions that occur when sea ice melts. She had boarded in the Falkland Islands (Islas Malvinas), and as the Attenborough headed southwest toward the Antarctic Peninsula, news spread on board that the ship would be able to detour to intercept A23a. 

During the early hours of December 1, the Attenborough reached the iceberg, and Taylor found herself face-to-face with its reality. “It looks like a giant wall, and it stretches as far as you can see in both directions along the horizon,” Taylor says today. “It’s towering way taller than the ship, so you can’t see onto the top ... and it’s very dynamic. The waves are crashing up against it. Sometimes there are chunks that are breaking off and falling into the water.” 

For Taylor, the encounter offered an unexpected research opportunity. As the Attenborough sailed alongside A23a, the ship’s submerged sampling system collected water that she would later analyze to help understand how iceberg meltwater affects the chemical composition—and thus the marine biodiversity—of surrounding waters. 

But perhaps Taylor’s most memorable moment came when the ship sailed right into a fjord-like inlet inside the towering iceberg. “That was quite amazing,” she recalls. “You can see the iceberg on all sides, just a narrow gap showing the way back out.” One of her colleagues, physical oceanography Ph.D. student Kat Turner, had been entrusted with a side task: to record sounds from their journey for a multimedia art project. While the ship was in the inlet, Turner captured the ambient noise of the water, ice, and wind, as well as the sounds of the ship and the scientists’ distant voices. Later, her recordings would be melded into a meditative piano-led soundscape, part of a nearly 14-minute track titled “A23a: The Largest Iceberg in the World.” 

Many observers presumed that A23a, once in open water, would simply drift northward toward its inevitable fate. But instead, almost as though it realized—and relished—that its story would be one of defying expectations, the iceberg arced above the South Orkney Islands and then did something very strange. In March 2024, A23a’s progress across the ocean simply halted, and it began to twirl.  

“It appears the iceberg got caught in an oceanic gyre,” reported Lieser on April 10, “and has spun 360 degrees anti-clockwise.” By the end of April, A23a—then some 40 nautical miles long and 32 nautical miles across—had completed nearly three rotations. It moved a bit farther northwest, still spinning, before stalling again. By late July, it had rotated seven times. By late October, 14 times. Imagine an island more than twice the size of Maui that one day, for no apparent reason, starts revolving.  

The only plausible explanation, scientists agreed, was what’s known as a Taylor column, a phenomenon in fluid mechanics in which, under certain conditions, a solid protuberance causes liquids flowing above it to fix in place. Here, an undersea mountain—rising significantly off the ocean floor, but still far from the bottom of the iceberg—was forcing the water above into a static rotating cylinder. Taylor columns, although well studied, are rarely found on a scale capable of trapping the world’s largest iceberg. The capture of A23a was a striking reminder that the seafloor, which we have only begun to accurately map, has the power to shape our world in startling ways. 

A23a’s imprisonment—and its resilience against the column’s violent force—fascinated Catherine Walker, an American scientist who specializes in studying ice fractures both on Earth and elsewhere in the solar system. She’d become aware of A23a about 15 years earlier, while mapping rifts across Antarctica, cracks that would likely eventually form icebergs. “The fact that it sat in a Taylor column for a good amount of time, this sort of tornado in the ocean, and it was just spinning,” she says. “The way we think about those things usually is that puts a tremendous amount of stress on the ice ... That it sort of sat there, spun around for a really long time, and didn’t completely self-destruct was really interesting.”  

But Walker was also drawn to A23a for reasons that went beyond pure scientific curiosity. “I tend to anthropomorphize things,” she says, “which is probably not good as a scientist because you sort of get attached to things, right? And then they disappear.” She had noted years before that she and A23a shared a connection—they had been born in the same year—and she now watched and wondered whether this might be its strange final fate: to slowly shed smaller icebergs as it spun, round and round and round, until there was nothing left to spin. 

When, in mid-November, after eight months trapped in the Taylor column, A23a somehow broke free, Walker felt a conflicted sense of relief and disappointment. “In the vortex,” she says, “I think it would have been really interesting, scientifically, if it had been torn apart by that.” There might have been valuable lessons to learn from when and how it fractured. “But from a personal standpoint,” she admits, “I wanted it to survive and keep going.” 

And it did. Still rotating, moving northeast at around five miles a day, A23a resumed its wanderings.  

As it headed into warmer water, A23a continued shedding ice, occasionally giving up more of its secrets. In January 2025, a Chinese expedition guide on a tourist ship photographed, then blogged about, a cluster of what appeared to be rusted barrels and storage tanks, once buried deep within the iceberg and now exposed at its edges. The detritus was soon identified as unsalvaged remnants of the Soviet Druzhnaya 1 station, carried for over 38 years and 2,000 miles.

In France, documentarian Jérôme Bouvier, learning that A23a had resumed its journey, hastily assembled a crew to fly to the Falkland Islands (Islas Malvinas). He’d planned to film A23a the year before but called off the project after the iceberg became trapped in the Taylor column. In early February, Bouvier, a three-person crew, and two divers boarded a 50-foot sailing boat, planning to spend several weeks filming around the iceberg.

As they neared A23a, the weather conditions were already concerning enough that the captain insisted they cut the engines and heave to for the night. But before dawn, he woke them to see the line of the iceberg on the horizon, lit by the moon. And that first day was a good one—sun, not too much wind. They neared the iceberg’s edge and started to work. “It was a mix between fascination and fear,” Bouvier remembers. “It’s so powerful. It’s like a wall. An infinite wall. And with caverns. And there is ice falling, part of the cliffs falling everywhere.”

They swiftly learned just how precarious the environment around a giant, disintegrating iceberg can be. Scouting a safe place to dive alongside it, the team settled upon an underwater terrace that extended some 200 feet from the cliff, where the divers might be safe from falling fragments while still filming ice up close. With the location selected, they sailed off to do some further exploring. When they returned to the spot later, they found the underwater terrace was gone. It had presumably fractured off the iceberg in their absence—a reminder of just how unpredictable and dangerous the conditions around A23a could be.

As they filmed, one thing that surprised Bouvier and his crew was how much life surrounded the iceberg. “The first day we saw whales and a lot of birds and penguins and so many leopard seals ... snow petrels too, normally a species that you meet in Antarctica,” Bouvier says. “We really had the thought that it was a piece of Antarctica that came to us with all the inhabitants of Antarctica—like a ship with a whole crew coming and traveling all together ... It’s like an island and just moving.”

During their second night alongside A23a, Bouvier’s team knew a storm was coming, so they positioned their boat within an arched side of the iceberg, in a kind of bay they figured would offer some protection. “It was a really, really tough night,” Bouvier says. “Nobody slept.” The boat drifted in the rough seas, and the small crew had to keep navigating blindly back toward the ice face. After one more day of shooting, the team’s captain insisted they recuperate in a safe harbor at the island of South Georgia, a British territory with a small seasonal population of researchers.

While Bouvier’s crew was on South Georgia, awaiting a weather window for a return trip, A23a continued moving northeast, toward the island. Its trajectory touched off another spate of headlines, this time heralding the iceberg’s “collision course” with South Georgia. The island was never truly at risk of a collision, as an iceberg of A23a’s size would run aground on offshore ledges well before reaching land—but if it were close enough, even that circumstance might disrupt the travel and feeding patterns of the island’s many penguins and seals.

(The world's largest iceberg is on a collision course with vital penguin sanctuary.)

At the beginning of March, however, A23a hit a rising ocean ridge about 70 miles away from South Georgia, pivoting a little before sticking in place. The French filmmaking team was still on South Georgia at the time, but after a month on the island, their weather window never reopened. A23a had allowed them a fleeting moment in its presence and had let them leave safely, but it was offering no more.

“We were not able to come back to the iceberg,” Bouvier says. “So frustrating, because the three days we spent along the iceberg were completely fantastic.” They had filmed enough, however, as the iceberg closed in on the island, to tell a compelling story. Bouvier’s film, Le Radeau Des Glaçes (or Ice Nomads, its English title) aired on French TV last month. It documented a dramatic moment in A23a’s long journey. But not, it turned out, its final one.  

Many of the next wave of media stories suggested A23a had reached its final resting place. But once again, the iceberg surprised its forecasters. In late May 2025, A23a loosened from the shelf and drifted away, this time on a trajectory that took it east beneath South Georgia Island, then looped it back westward over the island’s northern coastline.

In early June, A23a’s size shrunk below 1,200 square miles, and it relinquished for the last time its title as the world’s largest iceberg. (The iceberg that inherited the distinction, D15a, remains in first place.) What would happen next, as A23a moved northward into progressively warmer water, was described last year in a paper by Lieser and others, listing the esoteric processes that conspire to take down a giant: “A23a will succumb to basal thinning, flexure by long-period ocean waves, and meltwater-driven hydrofracture leading to rapid calving and disintegration.”

Last December, when a crew member on the International Space Station took a photograph of A23a, its center was no longer white but blue, filled with meltwater held in place by ramparts around the iceberg’s upper edges.

Laura Taylor’s analysis of the samples she took on the Sir David Attenborough, published this year, suggested that meltwater from A23a was at that time only minimally affecting the biochemical environment around it. But this year, in the iceberg’s final months, as huge amounts of its original trillion-ton mass melted into the ocean, satellite imagery appeared to show plumes of chlorophyll trailing around it, suggesting a life-giving phytoplankton bloom in the dying iceberg’s wake.

The USNIC tracks icebergs until they fall below a size of 20 square nautical miles—or about 26 square miles—with no axis greater than 10 nautical miles. In their bulletin of March 20, 2026, the report noted that A23a had become too small to warrant further mention. In such official terms, it was gone.   

But not everyone stopped looking for A23a in March. Lieser, for one, kept watching. In April, he told a NASA blogger that he “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.” The same article linked to a satellite image from March 31, showing the once great iceberg over 2,000 miles from where its journey had started, with cracks running through it as it split apart. Three days later, another image showed the broken pieces, a little farther north, dispersing. 

“Watching it go away, as with all things that melt in Antarctica, is sort of sad,” Walker says. “I’ll definitely miss having it there and miss having something to constantly look at and be like, Where’s it today? or Where’s it gone? It sort of takes away a little bit of the excitement that I had to look at the images every week.” 

Of course, it’s hard to say whether all of A23a is truly gone. Given the thousands of small- and medium-size icebergs in the southern oceans, Lieser says, “it becomes increasingly difficult to identify the last remaining fragments of individual bergs.” He shared a link with me to an image captured April 25, through a rare cloud break, showing, as he carefully phrases it, “a patch of icebergs which I attribute to the demise of A23a”—scattered pieces, still moving away and melting.  

In May, Walker pointed me to a NASA satellite image, showing two small icebergs she believes were once part of A23a. “Not sure it will make it to exactly 40 years,” she wrote in an email, “but getting closer!”  

Walker’s email sparked a gentle global debate: Lieser suggested that her pieces, farther south than his April 25 objects, technically are classified as part of A23e, which split off from A23a earlier in the year. I started looking too, and a few weeks back, I spotted, in another break in the clouds, what appears to be one of Walker’s remnants. When I sent the link to her, she concurred. “Yes indeed,” she wrote. “Looks like it’s still hanging on.” And she appended a smiley face emoji.  

Maybe this was it: the very final glimmer we’ll see of that huge block of ice that wandered so far and for so long. Somewhere, either hidden by clouds or too small for us to see from orbit, other pieces will hang on a while longer, stubborn fragments of a natural wonder whose improbable journey transfixed us for a while. Until A23a, its story finally over, inevitably succumbs to the same fate as every iceberg before it, as its last frozen shard vanishes back into the water.