World’s biggest iceberg runs aground off South Georgia

(CNN) — The biggest iceberg in the world, named A23a, appears to have run aground after drifting around the Southern Ocean near Antarctica since 2020.

Weighing nearly a trillion metric tonnes (1.1 trillion tons), A23a has come to a stop off the island of South Georgia, a British Overseas Territory in the southern Atlantic Ocean, according to a statement from the British Antarctic Survey (BAS) published Tuesday.

The iceberg spanned an area of 3,672 square kilometers (1,418 square miles) when measured in August 2024 – slightly smaller than Rhode Island and more than twice the size of London.

It calved from the Filchner Ice Shelf in Antarctica in 1986 and then rested on the seabed in the Weddell Sea for more than 30 years.

In 2020 it started to drift with the ocean currents, but in late 2024 it got stuck for months spinning around an undersea mountain, delaying its expected journey north.

After it finally broke free, it was feared that A23a would head towards South Georgia and impede access to feeding grounds for seals and penguins that breed on the island.

But these concerns have abated as the iceberg appears to be grounded on the continental shelf around 90 kilometers (56 miles) from shore.

“If the iceberg stays grounded, we don’t expect it to significantly affect the local wildlife of South Georgia,” said Andrew Meijers, an oceanographer at the BAS, in the statement.

On the contrary, its arrival could have some benefits for wildlife.

“Nutrients stirred up by the grounding and from its melt may boost food availability for the whole regional ecosystem, including for charismatic penguins and seals,” he said.

And although the iceberg appears to be maintaining its structure for now, in recent decades large icebergs that have taken this route “soon break up, disperse and melt,” said Meijers.

“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 said in the statement.

“Large bergs have made it a long way north before – one got within 1000km of Perth Australia once – but they all inevitably break up and melt quickly after.”

When A23a does eventually break up, the smaller icebergs it produces will pose a hazard to fishing and shipping operations as they are harder to detect and track than one megaberg, said Meijers.

“Discussions with fishing operators suggests that past large bergs have made some regions more or less off limits for fishing operations for some time due to the number of smaller – yet often more dangerous – bergy bits,” he said.

Scientists have said that this particular iceberg probably broke away as part of the natural growth cycle of the ice shelf and not because of the fossil fuel-driven climate crisis.

But global warming is driving worrying changes in Antarctica, with potentially devastating consequences for global sea level rise.

CNN’s Rosa Rahimi contributed to this report.

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