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By Adam Vaughan

Sentinel Hub EO Browser, Sentinel-3

An iceberg the size of Cyprus is on a collision course with South Georgia, posing a major threat to the remote Atlantic island’s globally important penguin and seal colonies.

Icebergs breaking off from Antarctica often fragment in the South Atlantic, earning the region the nickname of the iceberg graveyard. But the sheer scale of this 158 kilometre-long and 48 kilometre-wide chunk of ice, named A68a, is unusual, say researchers following it by satellite.

The iceberg is tracking a route that historically ends at South Georgia. Travelling at around a kilometre a day, it could arrive at the island within a month. A close grounding threatens to block access to offshore feeding grounds for the island’s macaroni, gentoo, king and chinstrap penguins, as well as fur, leopard and elephant seals. This would make it difficult for the animals to feed their young.

“Potentially it could be very bad if it grounds and stays at the entrance to one of a number of important bays,” says Peter Fretwell at the British Antarctic Survey (BAS). South Georgia, a British overseas territory, is a global biodiversity hotspot, and is home to huge seabird colonies, including those of albatross.

But it is the seals and penguins that are most at risk, says Geraint Tarling at BAS. “A major decrease through a catastrophe of this sort will impact worldwide population size of these species by some margin,” he says.

Organisms on the seabed near the island would also be pulverised by the ice, potentially releasing their large stores of carbon to the atmosphere, he adds. And the addition of so much cold freshwater could harm marine algae, with knock-on effects up the food chain that would affect birds, seals and whales.

Fortunately, it is still “touch and go” whether A68a will arrive at South Georgia, says Fretwell. Currently, it is on the northern edge of historical trajectories reaching the island. In addition, even though the iceberg is estimated to have a relatively shallow “keel” below the water – about 200 metres thick – some rocky submarine shelves around the island are shallower than that, so may stop it getting too close.