Journalist on climate and science
Data journalist
The world’s largest iceberg is crashing into a remote British island, potentially putting penguins and seals at risk.
The iceberg is turning north from Antarctica towards South Georgia, a rugged British territory and wildlife sanctuary, where it could crush and break into pieces. It is currently 173 miles (280 km) away.
Countless birds and seals died in South Georgia’s icy bays and beaches when huge glaciers stopped them from feeding.
“Icebergs are inherently dangerous. I would be extremely happy if it missed us completely,” sea captain Simon Wallace told BBC News, speaking from the government ship Pharos South Georgia.
Around the world, a group of scientists, sailors and fishermen anxiously check satellite images to track the daily movements of this queen of icebergs.
is known as A23a and is one of the oldest in the world.
It broke away, or broke off, from the Filchner Ice Shelf in Antarctica in 1986, but became stuck on the sea floor and then caught in an ocean eddy.
He finally broke free in December and is now on his final journey, hurtling into oblivion.
Warmer waters north of Antarctica are melting and weakening its massive cliffs that rise to 1,312 feet (400 m), higher than the Shard in London.
It used to measure 3,900 square kilometers, but the latest satellite images show that it is slowly deteriorating. It now covers about 3,500 square kilometers, roughly the size of the English county of Cornwall.
And large sheets of ice break, plunging into the water around its edges.
A23a could break into huge segments every day, which could then remain for years, like the floating cities of ice that cruise 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 its continental shelf, leaving dead penguin chicks and seal pups on beaches as massive chunks of ice blocked their access to feeding grounds.
The territory is home to precious colonies of royal emperor penguins and millions of elephants and seals.
“South Georgia is in Iceberg Alley, so both fisheries and wildlife can be expected to have impacts, both of which have great adaptive capacity,” says Mark Belchier, a marine ecologist who advises the South Georgia government.
Seafarers and fishermen say icebergs are a growing problem. In 2023, one called A76 spooked them as it came close to landing.
“The pieces were tilting, so they looked like big ice towers, an ice city on the horizon,” says Mr Belchier, who saw the iceberg while at sea.
These plates are still floating around the islands today.
“It’s in pieces the size of a couple of Wembley stadiums to pieces the size of your table,” says Andrew Newman of Argos Froyanes, a fishing company operating in South Georgia.
“Those parts basically cover the island – we have to break through,” says Captain Wallace.
The sailors on his ship must be constantly alert. “We have our floodlights on all night to try to see the ice – it can come out of nowhere,” he explains.
The A76 was a “game changer,” according to Mr. Newman, with “a major impact on our operations and on maintaining the safety of our vessel and crew”.
All three describe a rapidly changing environment, with visible glacier retreat from year to year and unstable sea ice levels.
Climate change is unlikely to be behind the birth of A23a because it calved so long ago, before most of the effects of the rising temperatures we see now.
But giant icebergs are part of our future. As Antarctica becomes more unstable with warmer ocean and air temperatures, larger chunks of ice sheets will break away.
Before his time is up, A23a left scientists with a parting gift.
A team from the British Antarctic Survey on the research ship Sir David Attenborough found themselves near A23a in 2023.
Scientists have been scrambling to take advantage of a rare opportunity to investigate what mega icebergs are doing to the environment.
The ship sailed into a crack in the huge walls of the iceberg, and Laura Taylor, Ph.D., collected precious water samples 400 meters from its cliffs.
“I saw a massive wall of ice far taller than me, as far as I could see. It’s different colors in different places. Pieces were falling – it was quite magnificent,” he explains from his laboratory in Cambridge, where he is now analyzing the samples.
Her work looks at what impact meltwater has on the carbon cycle in the Southern Ocean.
“This isn’t just the water we drink. It’s full of nutrients and chemicals, as well as tiny animals like phytoplankton frozen inside,” says Ms Taylor.
As it melts, the iceberg releases these elements into the water, changing the physics and chemistry of the ocean.
This could store more carbon deep in the ocean as particles sink from the surface. This would naturally block some of the planet’s carbon dioxide emissions that contribute to climate change.
Icebergs are notoriously unpredictable and no one knows exactly what they will do next.
But soon a giant should appear, looming on the horizon of the island, as big as the territory itself.
