A-68A – the largest iceberg in the world – broke off the Larsen C – ice shelf in the Weddell Sea on the Antarctic Peninsula in July 2017 and has since drifted about 1,400 kilometers north along the “Iceberg Alley”. Current satellite images suggest that it could hit the sub-Antarctic island of South Georgia, which is politically part of the British Overseas Territory. A collision of the giant with the nature paradise in the South Atlantic would have serious consequences – at around 150 kilometers in length and 48 kilometers in width, A-68A is somewhat larger than South Georgia itself.
The iceberg is only about 500 kilometers from South Georgia and the probability that it will run aground in the immediate vicinity of the island seems quite high. However, according to Dr. Sue Cook, glaciologist from Australian Antarctic Program Partnership difficult to predict which route he will actually take. “It lasted three years, which is longer than expected,” she says. Scientists had expected it to break up much sooner. But although two larger pieces have broken off already – A-68B and A-68C – its area is still around 4,200 square kilometers, from originally just under 6,000 square kilometers. The area of South Georgia is 3,700 square kilometers.
The ocean depths around South Georgia are between 200 and 400 meters. This means that the iceberg, which is about 200 meters thick underwater, could come very close to the coast before it becomes wedged on the sea floor.
Should A-68A really run aground off South Georgia, this would be a serious threat to the four species of penguin that breed there (king penguins, gentoo penguins, chinstrap penguins and macaroni penguins) as well as to various seal species (especially Southern elephant seals and Antarctic fur seals). Due to its massive size, the iceberg would block the animals’ usual routes to their hunting grounds.
Professor Geraint Tarling from British Antarctic Survey (BAS) told the BBC: “If you look at penguins and seals in this the time that is really crucial for them – during the rearing of pups and chicks – what matters is the actual distance they have to travel to find food. If they have to make a big detour, it means that they cannot get back to their offspring in time to prevent them from starving to death in the meantime. “
When the colossus A-38 ran aground northeast of South Georgia in 2004, countless dead penguin chicks and young seals were found on the beaches.
In addition, all organisms that live on the sea floor would be rolled down by the iceberg. The ecosystems will recover of course, said Professor Tarling. But with this iceberg there is a risk that it will remain there for ten years if stranded. “That would make a very big difference, not just to the ecosystem of South Georgia, but its economy as well,” he says. South Georgia is considered a highlight among expedition travelers and, depending on where the iceberg ends up, could be difficult or impossible to reach for ships. It is also a potential obstacle for fishing vessels.
However, there are positive effects of an iceberg stranding. Large amounts of dust are trapped in the ice and released into the water when it melts, providing nutrients for the plankton. As a result, many other organisms in the food web also benefit from this.
Now it depends on the currents which route A-68A takes. Dr. Peter Fretwell, a remote sensing and mapping specialist at BAS, says anything is possible. “The currents should loop it around the southern end of South Georgia before turning it along the edge of the continental shelf and back to the northwest. But it is very difficult to say exactly what will happen. “
If the evasive maneuver dictated by the currents succeeds and the iceberg does not get stuck close to the island, it will probably move further north and break up relatively quickly in warmer and more turbulent waters, says Dr. Andrew Fleming from BAS.
Julia Hager, PolarJournal
More on the subject: