Iceberg A23a heads north from Antarctica
The world’s largest iceberg, A23a, is drifting north from Antarctica, raising concerns as it approaches the British Overseas Territory of South Georgia.
Previously trapped for months around an undersea mountain, A23a now appears to be moving with prevailing ocean currents toward the island, according to Andrew Meijers, a physical oceanographer at the British Antarctic Survey.
“It is presently in a meander of the current and not moving directly towards the island,” Meijers explained in a statement to CNN. “But our understanding of the currents suggests that it is likely to again move towards the island soon.”
Iceberg poses hazards for shipping and wildlife
Simon Wallace, a sea captain from the South Georgia government vessel Pharos, told CNN that if A23a stays in its current form, he can see it and track it easily. However, the danger is that it could break up and create thousands of tons of smaller icebergs.
“These become an issue because I don’t know where these are until I find them. All ice is very dangerous, the bigger it is the easier it is to find and avoid, smaller ice is much harder to detect but by no means less hazardous,” he told CNN via email.
“The smaller ice can gather in strips and patches and depending on their density can be impassable as well as filling the bays and fjords of South Georgia making them inaccessible to us, which can really be an issue.”
The potential impact extends beyond shipping to the island’s wildlife. Meijers warned that if A23a becomes lodged on the continental shelf, it could block access to feeding grounds for seals and penguins that breed on the island.
World’s largest iceberg remains intact
Measured at 3,672 square kilometers (1,418 square miles) as of August, A23a is slightly smaller than the state of Rhode Island but more than twice the size of London. The iceberg calved from the Filchner-Ronne Ice Shelf in 1986 and remained grounded on the Antarctic Weddell Sea floor for over 30 years.
In December, the iceberg broke free from a Taylor column—a spinning water vortex caused by ocean currents hitting an underwater mountain. Scientists initially expected A23a to drift into warmer waters and gradually break apart. However, recent satellite images reveal the iceberg has retained its structure, defying predictions.
Environmental and ecological implications
Mark Belchier, director of fisheries and environment for the government of South Georgia and the South Sandwich Islands, highlighted the potential risks to shipping and fishing in the region.
“Whilst they are common at South Georgia, they can cause issues for shipping and fishing vessels,” Belchier said, adding that any effects on wildlife would likely be localized and short-term.
South Georgia and the South Sandwich Islands are home to rich biodiversity, including one of the world’s largest Marine Protected Areas. Scientists emphasize that while A23a’s calving is part of the natural ice shelf growth cycle, the broader Antarctic region faces increasing instability due to climate change, with significant implications for global sea levels.
A waiting game
For now, the future of A23a remains uncertain. Whether it will drift into the open South Atlantic or become stranded near South Georgia will determine its long-term impact on the region’s ecosystem and maritime activity.
“We’re closely monitoring its track,” Belchier said. “The iceberg’s next move could have wide-ranging consequences for both the environment and local industries.”