The world's largest iceberg is heading towards a remote British island, endangering penguins and seals. The iceberg is heading north out of Antarctica towards South Georgia, a rugged British territory and wildlife haven where it could break apart. It is currently 280 kilometers away.
Countless birds and seals have died in icy bays and on South Georgia beaches when giant icebergs prevented them from feeding. "Icebergs are inherently dangerous. I would have been extremely happy if it had just skidded past us," said Simon Wallace, a sea captain who operates the government vessel Pharos in South Georgia.
Around the world, a group of scientists, sailors and fishermen are anxiously following the daily movements of the king of icebergs on satellite images, it is known as A23a and is one of the oldest in the world.
The iceberg broke off from the Filchner Ice Shelf in Antarctica in 1986, but got stuck on the seafloor and then got caught in an ocean vortex. It finally broke free in December and is now on its final journey, aiming for oblivion.
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Warmer waters north of Antarctica dissolve and weaken its huge cliffs, towering 400 meters higher than The Shard in London (an 87-story, 310-meter-high skyscraper that is the tallest building in the entire European Union).
A23a once covered an area of 3.9 thousand square kilometers, but recent satellite images show that it is slowly eroding. Now its area is about 3.5 thousand square kilometers, which is about the size of the English county of Cornwall.
Large plateaus of ice break off, sinking into the waters along its edges. On any given day, A23a could split into huge segments, which would then drift for years as floating cities of ice circling uncontrollably around South Georgia.
This is not the first huge iceberg to threaten South Georgia and the Sandwich Islands. In 2004, one called A38 ran aground on the continental shelf, leaving penguin chicks and baby seals dead on beaches as massive blocks of ice blocked their access to feeding grounds.
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The area is home to valuable colonies of Royal Emperor penguins and millions of southern elephant seals, as well as fur-bearing harp seals.
"South Georgia is in an alley of icebergs, so impacts on both fisheries and wildlife are to be expected, but both have a great capacity to adapt," says Mark Belchier, a marine ecologist advising the South Georgia government.
Sailors and fishermen say icebergs are becoming an increasingly serious problem. In 2023, one called A76 gave them a scare when it came close to grounding. "Chunks of the iceberg were rising up and they looked like huge ice towers, like an ice city on the horizon," said Belchier, who saw the iceberg while at sea.
These blocks still lie around the islands. "It's made up of pieces the size of several Wembley stadiums and pieces the size of your desk," says Andrew Newman of the fishing company Argos Froyanes, which operates out of South Georgia.
"These chunks practically cover the island - we have to fight our way through them," says Capt. Wallace. Sailors on his vessel have to be constantly vigilant. "We have searchlights on all night to try and see the ice - it can come out of nowhere," he explains.
According to Newman, A76 was "a turning point in the journey" that had a "huge impact on our operations and the safety of our ship and crew."
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All three men describe a rapidly changing environment where glacial retreat is noticeable from year to year and sea ice levels are inconsistent. Climate change is unlikely to have caused the birth of A23a because it formed so long ago, even before humans witnessed the significant impact of rising temperatures.
But giant icebergs are part of humanity's future. As Antarctica becomes more unstable due to warming oceans and air, more and more huge chunks of the ice sheet will break off.
But before its time comes to an end, A23a has left researchers a parting gift. A team from the British Antarctic Survey on the research vessel Sir David Attenborough found themselves near A23a in 2023. The scientists rushed to seize the rare opportunity to investigate how mega-icebergs affect the environment.
The ship entered a crack in the iceberg's giant walls, and Laura Taylor, Ph.D., collected precious water samples 400 meters from its elevations.
"I saw a massive wall of ice far above me as far as I could see. It was different colors in different places. Pieces were falling off of it - it was just grand," she explains from her lab in Cambridge, where she is now analyzing samples.
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Her work examines the impact of meltwater on the carbon cycle in the Southern Ocean. "It's not just water we drink. It's full of nutrients and chemicals and tiny living things like phytoplankton frozen inside," says Taylor.
By melting, the iceberg releases these elements into the water, changing the physical and chemical characteristics of the ocean. This will store more carbon in the deep ocean as the particles sink from the surface of the ice. This will naturally block some of the carbon dioxide emissions that contribute to
climate change.
Icebergs are notoriously unpredictable, and no one knows what exactly will happen over time. But soon, a giant as big as the territory itself is expected to appear on the islands' horizon.