Iceberg A23a Approaching South Georgia Island, Feb. 20, 2025. (Photo: MODIS Land Rapid Response Team, via Wikimedia Commons, Public domain)
In 1986, the world’s largest and oldest iceberg calved from the Antarctic shelf. Known as A23a, the iceberg weighs one trillion tonnes and was stuck on the seabed for decades before breaking free in 2020. Now, scientists are grappling with a new development. As of early March, A23a has run aground in the water about 50 miles from the remote British island of South Georgia.
Located in the South Atlantic Ocean, South Georgia is renowned for its rugged landscape, freezing climate, and extraordinary wildlife. A23a’s trajectory toward the island was, at first, met with worry, given its position as a critical breeding ground for penguins, seals, and albatrosses. Researchers have since determined that the iceberg may, in fact, have critical benefits to the island’s ecosystem.
“Nutrients stirred up by the grounding [of the iceberg] and from its melt may boost food availability for the whole regional ecosystem, including for charismatic penguins and seals,” Andrew Meijers, an oceanographer with the British Antarctic Survey (BAS), tells The Guardian.
Nadine Johnston, also with the BAS, expressed a similar opinion: “It’s like dropping a nutrient bomb into the middle of an empty desert,” she explained to the BBC.
Further easing anxieties is the fact that, as of this writing, the iceberg is stuck and is expected to break up on the island’s southwest shores, thus avoiding complete collision.
“[A23a] is probably going to stay more or less where it is, until chunks break off,” Meijers added.
The iceberg is already displaying signs of erosion, steadily shedding huge amounts of freshwater as it advances into warmer seas. Sky News joined members of the Royal Air Force on a routine flyby of the area and got a firsthand look at the situation. They not only noted erosion at the iceberg’s edges, but “large icebergs hundreds of meters across have already broken off and are drifting closer to South Georgia.”
The melting of A23a’s freshwater ice into the surrounding salt water may reduce the amount of food, such as krill, that macaroni penguins eat, forcing them to migrate toward other feeding grounds and thus enter into competition with other species.
Fishermen, harbors, and vessels in the area may also suffer as a result of the iceberg and its gradual decay into smaller particles.
“If [A23a] breaks up, the resulting icebergs are likely to present a hazard to vessels as they move in the local currents and could restrict vessels’ access to local fishing grounds,” ecologist Mark Belchier tells the BBC.
Despite this, scientists have expressed that, overall, A23a’s lodging will result in an immense flow of nutrients across both South Georgia’s and the world’s oceans.
“Without ice, we wouldn’t have these ecosystems. They are some of the most productive in the world, and support huge numbers of species and individual animals, and feed the biggest animals in the world like the blue whale,” Huw Griffiths, a professor with BAS, says. “Where it is destroying something in one place, it’s providing nutrients and food in other places.”
It’s currently unclear how much ice will break away from or melt off of A23a, preventing scientists from making sweeping conclusions about how disruptive it will ultimately be to fishing, mating, and feeding patterns in the region. The BAS is monitoring the iceberg aboard the Sir David Attenborough polar research ship and is collecting data about possible nutrient flow.
The world’s largest and oldest iceberg, known as A23a, has run aground in the waters off South Georgia island in the South Atlantic Ocean.
The island of South Georgia as seen from The Copernicus Sentinel-2 mission, 2018. (Photo: European Space Agency, via Wikimedia Commons, CC 3.0)
For decades, A23a has remained stuck on the seabed but, in 2020, it began moving toward the remote British island, which is home to millions of penguins and seals.
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British scientists aboard the Sir David Attenborough polar research ship are researching the nutrients that may be stored inside of A23a, all of which would greatly benefit the surrounding region.
RRS Sir David Attenborough berthed at Liverpool Cruise Terminal. (Photo: Rodhullandemu, via Wikimedia Commons, CC 4.0)
Get a bird’s eye view of the enormous iceberg thanks to Sky News, who tagged along with the Royal Air Force on a routine flyby of the area.
Sources: World’s biggest iceberg runs aground after long journey from Antarctica; World’s largest iceberg runs aground off remote island; What we learnt flying over the world’s largest iceberg A23a – and why it’s not long for this world
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