The world’s largest iceberg, known as A23a, has run aground off the remote British island of South Georgia, raising concerns among scientists, conservationists, and the fishing industry.
The massive iceberg, approximately twice the size of Greater London, appears to be stuck in shallow waters and is expected to begin breaking up along the island’s southwestern shores.
A Threat to Local Wildlife and Fishing
South Georgia is home to millions of penguins, seals, and other marine species. The grounding of A23a has sparked fears that it could disrupt ecosystems and interfere with the feeding habits of certain species, particularly macaroni penguins. These birds rely on krill and small fish, which could become scarce if the iceberg melts and alters the salinity and nutrient balance of the surrounding waters.
Fishermen are also worried that as A23a breaks apart, large chunks of ice could obstruct key fishing grounds. Ecologist Mark Belchier, an adviser to the South Georgia government, highlighted the potential hazard posed by drifting icebergs, stating, “If it breaks up, the resulting icebergs are likely to present a hazard to vessels as they move in the local currents and could restrict access to local fishing grounds.”
A Long Journey Comes to a Halt
A23a’s journey began nearly four decades ago when it broke away from the Filchner-Ronne Ice Shelf in 1986. For years, it remained trapped in an ocean vortex before finally breaking free in December 2023. As it drifted north into warmer waters—through an area known as Iceberg Alley—scientists tracked its movement via satellite images.
Despite spending months in increasingly warmer seas, A23a remained surprisingly intact, even rotating at times before accelerating in mid-February, moving at a speed of approximately 20 miles (30km) per day. On March 2, 2025, the iceberg struck the shallow continental shelf about 50 miles (80km) from South Georgia, where it now appears firmly lodged.
Signs of Decay and Potential Ecological Impact
Although A23a remains massive—currently measuring approximately 3,234 square kilometers, down from its original 3,900 square kilometers—it is beginning to show signs of decay. “Instead of a big, sheer pristine box of ice, you can see caverns under the edges,” said Professor Andrew Meijers from the British Antarctic Survey (BAS). As tides lift and lower the iceberg, it will grind against the seabed, gradually eroding both the ice and the underlying rock.
The impact of this grinding is already being felt by thousands of tiny sea creatures living on the ocean floor. Professor Huw Griffiths, a marine biologist aboard the Sir David Attenborough research vessel, described the situation: “Their entire universe is being bulldozed by a massive slab of ice scraping along the sea floor.” While this destruction is significant in the short term, he also emphasized that it is a natural part of the Antarctic ecosystem’s cycle.
A “Nutrient Bomb” for the Ocean
Despite concerns, A23a’s melting could also bring significant benefits. As the iceberg releases freshwater into the ocean, it will also unleash vast quantities of nutrients that have been locked in the ice for decades.
This process, described by Professor Nadine Johnston from BAS as “dropping a nutrient bomb into an empty desert,” is expected to fuel enormous phytoplankton blooms. These microscopic organisms form the foundation of the marine food chain, supporting krill populations and, in turn, larger species such as whales and seabirds.
Scientists anticipate that satellite images will soon reveal a vast green halo of phytoplankton surrounding A23a, marking the start of an oceanic nutrient boom.
The Role of Climate Change
A23a’s story is part of a broader pattern of increased iceberg activity linked to climate change. As Antarctic temperatures rise, more icebergs are calving from the continent’s ice shelves. This trend could have long-term consequences for global ocean currents, marine ecosystems, and human activities such as fishing and shipping.
While A23a’s fate remains uncertain, its presence off South Georgia highlights both the fragile balance of the polar ecosystem and the interconnectedness of climate processes. As researchers continue to monitor the iceberg, they hope to gain further insights into the evolving relationship between Antarctica’s ice shelves and the planet’s changing climate.
For now, South Georgia’s inhabitants—both human and animal—will have to adapt to the imposing presence of the world’s largest iceberg.
