Scientists are preparing for an urgent mission to the world’s biggest iceberg, which is on a collision course with the island of South Georgia in the southern Atlantic Ocean.
The A-68A iceberg, which is larger than Luxembourg, broke off from the Larsen C ice shelf in Antarctica in 2017 and has been drifting towards the island ever since.
It threatens to wreck the rich ecosystem around South Georgia by tearing up the sea floor, which is home to molluscs, crustaceans, sponges and other life, and by chilling the water and releasing meltwater into the sea.
Researchers at British Antarctic Survey (BAS) will fly out to the Falklands on 11 January, quarantine themselves to ensure they are free from coronavirus, and then embark on a three-day voyage to the iceberg onboard the research ship the RRS James Cook.
“Even though icebergs are common, we’ve never had anything this size before, so it’s a first for us,” said Prof Geraint Tarling, a biological oceanographer at BAS. “It brings a wholesale change to the environment.”
Strong ocean currents are steering the iceberg, which has a surface area of around 1,500 sq miles (4,000 sq km), from deep water towards the shallower waters of the continental shelf that surrounds South Georgia.
The edge of the shelf is rich in phytoplankton, krill and other species low on the food chain, making it an important feeding ground for penguins, seals and whales. “The biodiversity of this area is as rich as you’d find in the Galapagos,” said Tarling.
The waters around South Georgia are about 4C, but in the vicinity of the iceberg the temperature could fall a couple of degrees. The cooler temperature and release of what could potentially be billions of tonnes of fresh water into the region could be devastating for the feeding ground.
“If the iceberg does ground, we could be looking at this being there for up to 10 years because it’s so large. It’ll be a huge problem,” said Tarling.
Beyond disrupting the ecosystem, if the iceberg gets stuck on the continental shelf it will block off a large stretch of feeding ground where krill are most abundant. That could prevent penguins and seals from finding food nearby for themselves and their young in the breeding season.
Tarling said that while whales might be able to find other feeding grounds, large colonies of penguins and seals could not leave the island to go far. “They are fixed to their base and without being able to get out, feed and get back quickly, they have got a real problem.”
When the research ship arrives at the iceberg, the scientists will use nets and bottles to collect and study animals in the water. Two robotic submarines called gliders will be launched to measure the temperature, salinity and levels of phytoplankton in the water around the iceberg.
The gliders will patrol the region for four months, rising from their dives and transmitting data back to the ship. By combining this information with that from the ship-based studies, scientists will build up a picture of the iceberg’s impact on the environment.
Povl Abrahamsen, the chief scientist on the mission at BAS, said the latest images showed the iceberg was about 60 miles off the coast of South Georgia. “It may be the iceberg ends up bumping and scraping along the edge of the shelf or breaks clear of the islands. But it may also get grounded and stay around for months or years. At this stage it’s very difficult to predict what will happen next,” he said.