The World’s Largest Iceberg Runs Aground, Potentially Averting a Collision With Penguin and Seal Breeding Areas

The world’s biggest iceberg seems to have come to a halt near a remote island in Antarctica, after months of drifting through open ocean.

A23a, as the iceberg is known, had briefly raised alarm bells over a potential collision with South Georgia Island in the South Atlantic, which is home to penguins and seals. Now, scientists say that scenario has potentially been averted, and A23a might even be beneficial to the local wildlife. Nutrients from the iceberg’s melt could boost food availability for the regional ecosystem, according to a statement from the British Antarctic Survey.

“This isn’t just water like we drink. It’s full of nutrients and chemicals, as well as tiny animals like phytoplankton frozen inside,” Laura Taylor, a researcher studying the iceberg with the British Antarctic Survey, told Georgina Rannard of BBC News in January.

A23a has taken a decades-long journey to its current destination. It calved from Antarctica’s Filchner-Ronne Ice Shelf in 1986 and, for 34 years, had a pretty uneventful existence. It stayed put in the Weddell Sea, grounded off the coast of West Antarctica. But in 2020, the so-called “megaberg” went on the move again, drifting along with the ocean currents, until it got stuck spinning around in a rotating column of water for months in 2024.

After it made an escape from the vortex, experts feared the giant iceberg—which weighs 1.1 trillion tons—was on a collision course with a breeding ground for penguins and seals on South Georgia Island. Had it hit the island—or halted in shallow water closer to its shores—the iceberg could have disrupted the animals’ ability to care for their young by blocking off routes to feeding areas and forcing them to swim farther.

For now, A23a is grounded roughly 50 miles from the island’s shores and is no longer expected to cause serious harm to any animals, as long as it stays at its current location. “In the last few decades, the many icebergs that end up taking this route through the Southern Ocean soon break up, disperse and melt,” says Andrew Meijers, an oceanographer with the British Antarctic Survey, in the statement.

A23a megaberg escapes after months in ocean vortex | British Antarctic Survey

The Rhode Island-sized iceberg still might impact the fishing industry, however, as other icebergs have disrupted commercial fisheries in the past. “As the berg breaks into smaller pieces, this might make fishing operations in the area both more difficult and potentially hazardous,” Meijers adds.

“Now it’s grounded, it is even more likely to break up due to the increased stresses, but this is practically impossible to predict,” he says in the statement. “Large bergs have made it a long way north before—one got within 1,000 kilometers of Perth, Australia, once—but they all inevitably break up and melt quickly after.”

“It will be interesting to see what will happen now,” adds Meijers.

While icebergs like A23a form as a natural part of the life cycle of ice sheets, climate change has caused the loss of 6,000 billion tons of mass from ice shelves in the last 25 years, according to the statement.

Now, icebergs are breaking from the frozen continent at a faster rate than snowfall is adding to it, as Chad Greene, a glaciologist at NASA’s Jet Propulsion Laboratory, told New Scientist’s James Dinneen in 2023. “Climate change is causing the Antarctic Ice Sheet to lose mass at a significant rate,” he said.

As glaciers continue to lose ice, sea levels will increase. “This loss of ice shelf mass has significant implications for ocean circulation due to the addition of freshwater, acceleration of sea-level rise and possible irreversible ‘tipping points,’ particularly in the vulnerable West Antarctic,” Meijers says in the statement.