The world’s largest iceberg looks set to collide with a group of remote islands in the southern Atlantic, risking the safety of wildlife in a region renowned for rich biodiversity that surpasses even that of the Galapagos.
Currently around 173 miles (280 kilometers) away, the massive iceberg, A23a, could crash into South Georgia and surrounding islands, and its grounding stands to endanger millions of penguins, seals, and rare marine species not found anywhere else on Earth.
“Icebergs are inherently dangerous. I would be extraordinarily happy if it just completely missed us,” Simon Wallace, captain of South Georgia government vessel Pharos, told BBC News.
This isn’t the first time a giant iceberg has put animal lives in the region at risk. After splitting in half, part of an iceberg known as A38-B was grounded off South Georgia for months in 2004, blocking penguins and seals’ access to feeding grounds.
With a surface area more than twice that of Greater London, A23a calved from the Filchner-Ronne Ice Shelf in 1986.
Its first few decades of freedom were anticlimactic, sitting anchored on the sea floor until gradual melting allowed it to begin inching towards the Southern Ocean in 2020, breaking loose in 2023, only to become trapped by a swirling vortex of water last year.
The frozen leviathan took off across Antarctic seas once more in December after having spent the previous few months going round in circles.
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These particular ocean vortexes are known as Taylor columns, caused by the presence of underwater mountains. The circulating currents that result can make it difficult for icebergs to break free, but the trillion-ton A23a did just that, and scientists continue to closely monitor it.
We know that icebergs can make a huge difference to the levels of carbon and nutrients in the water as they melt, which in turn affects food chains and aquatic life under the waves.
Including more than three decades of being grounded in the Weddell Sea, trapped by its own size and weight on the ocean floor, the interrupted progress of A23a has significantly slowed its melting.
BAS scientists on the research vessel Sir David Attenborough were able to take a closer-than-usual look at A23a after it started moving again in 2023, and collected samples to look at the impact of melt water on ecosystems.
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“We are interested to see if it will take the same route the other large icebergs that have calved off Antarctica have taken,” said oceanographer Andrew Meijers from the British Antarctic Survey (BAS) in December. “And more importantly what impact this will have on the local ecosystem.”
The BAS team predicts winds and currents will carry A23a into the Southern Ocean as it follows the Antarctic Circumpolar Current, taking it closer to an area known as ‘iceberg alley‘.
“South Georgia sits in iceberg alley so impacts are to be expected for both fisheries and wildlife,” marine ecologist Mark Belchier told BBC News.
Considering the scale of A23a, it’s difficult to predict what the consequences of its melting would be when it hits warmer waters – but past research has shown a boost in iron from melting glaciers can increase phytoplankton levels, for example, trapping a portion of CO2 from the atmosphere.
“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas,” explains BAS biogeochemist Laura Taylor, who is studying the samples collected in 2023.
“What we don’t know is what difference particular icebergs, their scale, and their origins can make to that process.”
This article has been updated from an earlier version published in December 2024.
