The world’s largest iceberg is heading toward the remote British territory of South Georgia, threatening the island’s penguin and seal populations.
Drifting northward from Antarctica, the massive iceberg is now just 173 miles (280 km) away from the rugged wildlife sanctuary. If it grounds and breaks apart near the island, it could disrupt the ecosystem, as seen in the past when similar icebergs blocked access to feeding areas, leading to the deaths of countless birds and seals.
“Icebergs are inherently dangerous. I’d be extraordinarily happy if it completely missed us,” said Simon Wallace, a sea captain aboard the South Georgia government vessel Pharos, in an interview with BBC News.
The RAF recently conducted a flyover of the massive iceberg as it approached South Georgia.Around the world, a group of scientists, sailors, and fishermen are anxiously checking satellite pictures to monitor the daily movements of this queen of icebergs.
It is known as A23a and is one of the world's oldest.
It calved, or broke off, from the Filchner Ice Shelf in Antarctica in 1986 but got stuck on the seafloor and then trapped in an ocean vortex.
Finally, in December, it broke free and is now on its final journey, speeding into oblivion.
The warmer waters north of Antarctica are melting and weakening its vast cliffs that tower up to 1,312ft (400m), taller than the Shard in London.
It once measured 3,900 sq km, but the latest satellite pictures show it is slowly decaying. It is now around 3,500 sq km, roughly the size of the English county of Cornwall.
And large slabs of ice are breaking off, plunging into the waters around its edges.
A23a could break into vast segments any day, which may then hang around for years, like floating cities of ice cruising uncontrollably around South Georgia.
This isn’t the first time a massive iceberg has posed a threat to South Georgia and the South Sandwich Islands.
In 2004, an iceberg named A38 became grounded on the island's continental shelf, resulting in the deaths of penguin chicks and seal pups as the massive ice chunks blocked access to their feeding grounds.
The territory is home to vital colonies of King penguins and millions of elephants and fur seals.
“South Georgia lies in iceberg alley, so these impacts are not uncommon for both fisheries and wildlife. Fortunately, both have a remarkable capacity to adapt,” says Mark Belchier, a marine ecologist advising the South Georgia government.
Sailors and fishermen are increasingly concerned about the growing presence of icebergs in the region. In 2023, one iceberg, named A76, caused a scare when it came dangerously close to grounding.
"Chunks of it were tipping over, making it look like massive ice towers—an ice city on the horizon," recalls Mark Belchier, who witnessed the iceberg while at sea.
Those large ice slabs are still floating around the islands today.
"They've broken into pieces ranging from the size of several Wembley stadiums down to chunks as small as your desk," says Andrew Newman from Argos Froyanes, a fishing company operating in South Georgia.
"These pieces are scattered across the island, so we have to navigate through them," adds Captain Simon Wallace.
The sailors aboard his ship are on high alert at all times. "We keep the searchlights on all night to spot ice—it can appear out of nowhere," he explains.
A76 has proven to be a "game-changer," according to Newman, with a "huge impact on our operations and the safety of our vessel and crew."
All three men describe an environment undergoing rapid change, with visible glacial retreat year after year and fluctuating sea ice levels.
While climate change is unlikely to have contributed to the formation of A23a—since it calved long before the significant impacts of rising temperatures became apparent—giant icebergs will likely be a recurring feature in our future. As Antarctica grows increasingly unstable due to rising ocean and air temperatures, more massive sections of the ice sheets are expected to break off.
Before A23a’s time comes to an end, it has left scientists with a valuable gift.
In 2023, a team from the British Antarctic Survey aboard the Sir David Attenborough research vessel found themselves unexpectedly close to the iceberg. Seizing the rare opportunity, the scientists quickly set to work studying the impact mega icebergs have on the environment.
The ship navigated into a crack in the towering walls of the iceberg, where PhD researcher Laura Taylor collected invaluable water samples just 400 meters from its cliffs.
"I saw a massive ice wall towering over me, stretching as far as I could see. The colors varied across its surface, and chunks were breaking off—it was truly magnificent," she recalls from her lab in Cambridge, where she is now analyzing the samples.
Her research focuses on how the meltwater from the iceberg affects the carbon cycle in the Southern Ocean.
"This isn't just water like we drink. It's rich in nutrients and chemicals, and contains tiny creatures like phytoplankton frozen within," says Ms. Taylor.
As the iceberg melts, it releases these elements into the surrounding water, altering the ocean’s physical and chemical makeup.
This could lead to more carbon being stored deep in the ocean as particles sink from the surface, potentially locking away some of the carbon dioxide emissions that contribute to climate change.
Icebergs are notoriously unpredictable, and no one knows exactly what A23a will do next.
However, it will soon become an unmistakable presence, looming on the horizon of the islands, as massive as the territory itself.
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