World’s Largest Iceberg A23a Runs Aground Near South Georgia Island

The world’s largest and oldest iceberg, A23a, has run aground near South Georgia Island in the sub-Antarctic, according to confirmation from the British Antarctic Survey (BAS).

This trillion-tonne ice giant, comparable in size to Rhode Island, began its journey when it calved from Antarctica’s Filchner Ice Shelf in 1986.

After remaining stationary in the Weddell Sea for over three decades, A23a began drifting with Southern Ocean currents in 2020, finally reaching its current position approximately 90km from South Georgia Island.

Dr. Andrew Meijers, an oceanographer with the British Antarctic Survey and co-leader of the OCEAN:ICE project, reports that the iceberg “appears to be maintaining its structure and has not yet broken up into smaller chunks, as previous ‘megabergs’ have done.” However, he predicts that “now it’s grounded, it is even more likely to break up due to the increased stresses.”

The massive berg’s journey featured an unusual scientific phenomenon in late 2024 when it became trapped in a Taylor Column – an oceanographic occurrence where rotating water above a seamount temporarily immobilized the iceberg, delaying its northward drift.

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While researchers don’t anticipate significant impacts on South Georgia’s wildlife, the berg may create challenges for commercial fishing operations. “As it breaks up over time, the smaller bergs are much harder to track,” notes Dr. Meijers. “Discussions with fishing operators suggests that past large bergs have made some regions more or less off limits for fishing operations due to the number of smaller – yet often more dangerous – bergy bits.”

Scientists are closely monitoring A23a to study its environmental effects. “From a scientific perspective we are keen to see how the iceberg will affect the local ecosystem,” explains Meijers. “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.”

The British Antarctic Survey has been collecting valuable data around the iceberg, deploying ocean gliders and taking samples to understand how such “megabergs” influence ocean circulation, chemistry, and ecosystems. Of particular interest is how icebergs may fertilize the ocean with nutrients and micronutrients, potentially boosting biological productivity and carbon sequestration.

While A23a itself isn’t directly linked to climate change – icebergs are a natural part of Antarctic ice sheet lifecycle – researchers note that ice shelf mass loss has accelerated since 2000, with approximately 6000 billion tonnes lost, attributed to anthropogenic climate change. This mass loss has significant implications for ocean circulation, sea level rise, and potential tipping points in vulnerable Antarctic regions.

The fate of A23a now depends on environmental forces, with warmer waters, waves and tides expected to eventually break up the massive structure into smaller icebergs that will ultimately melt.

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