World’s Biggest Iceberg Is on a Collision Course With Wildlife-Filled Island

World’s Biggest Iceberg Is on a Collision Course With Wildlife-Filled Island
A68a is the object that resembles a pointed finger. It's currently 250 miles (400 km) southwest of South Georgia island. (Image: Copernicus Sentinel 3 Mosaic/Polar View)
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The world’s biggest iceberg — called A68a — is heading directly towards the sub-Antarctic island of South Georgia, where it could wreak havoc on the local wildlife for years to come.

Satellite imagery shows the iceberg, which is larger than Rhode Island, drifting northeast towards the British overseas territory of South Georgia. As the British Antarctic Survey (BAS) explained in a release yesterday, the gigantic chunk of ice, should it reach the island and become anchored to the seafloor, would disturb the local wildlife, which includes seals and penguins.

Iceberg A68a broke off from the Larsen C ice shelf back in 2017, and it’s currently the world’s largest iceberg at 4,850 square km, according to recent figures provided to Gizmodo by a BAS spokesperson. The iceberg has shrunk a bit since it plopped into the ocean, but it’s still a behemoth, measuring about 158 km long and 48 km at its widest point. But A68a’s depth is less than 200 metres, which means it’ll likely clear the seafloor along the shallow shelf surrounding the island.

“The iceberg was measured using satellite altimetry shortly after calving at 200 metres thick,” explained the BAS spokesperson. “This measurement has not been repeated recently, so the current thickness will be a bit thinner than this due to some melting in the last three years.”

The iceberg is currently a few hundred kilometres to the southwest of South Georgia island, and it could reach the territory in about 20 to 30 days.

South Georgia hosts large numbers of whales, seals, and penguins.  (Image: Martin Collins/2020 South Georgia right whale project) South Georgia hosts large numbers of whales, seals, and penguins. (Image: Martin Collins/2020 South Georgia right whale project)

Should the iceberg park itself ashore, A68a would “cause disruption to the local wildlife that forage in the food-rich ocean,” according to BAS. Geraint Tarling, a BAS ecologist, said in the release the iceberg might stay there for as long as 10 years. This would pose a major problem to both terrestrial and marine ecosystems, including seafloor organisms smothered by the encroaching iceberg.

“When you’re talking about penguins and seals during the period that’s really crucial to them — during pup- and chick-rearing — the actual distance they have to travel to find food,” like fish and krill, “really matters,” said Tarling. “If they have to do a big detour, it means they’re not going to get back to their young in time to prevent them starving to death in the interim.”

Interestingly, this encounter was predicted as early as 2017. And indeed, such unions between icebergs and islands in the southern Atlantic ocean are not without precedent.

Tarling said there is a glass-half-full perspective to consider. Icebergs hold on to vast quantities of dust, which fertilize ocean plankton — major players in the marine food web and also consumers of atmospheric carbon dioxide.

Peter Fretwell, a remote-sensing and mapping specialist with BAS, said there’s an equal chance the iceberg could continue north instead of getting stuck on the island. As one possible outcome, he said the iceberg could loop around the south end of the island, move up along the continental shelf, and then head northwest. But “it’s very difficult to say precisely what will happen,” he said in the BAS release.

Should A68a veer north, as opposed to smashing into the island, that would likely spell doom for this historically big iceberg, which has managed to keep itself intact for three years. The iceberg would “very quickly get into warmer waters, and wave action especially will start killing it off,” explained BAS remote sensing manager Andrew Fleming.

BAS has asked the European Space Agency for more satellite imagery to track A68a’s progress. We’ll be watching these developments closely.