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Sunday, October 1, 2023

An Enormous Iceberg Is Headed for South Georgia Island—Again

A massive Antarctic iceberg is headed straight for South Georgia Island, a remote outpost in the southern Atlantic Ocean that is home to millions of seabirds, penguins, and seals that may find their route to the sea blocked if the Delaware-sized chunk of ice gets stranded near their breeding grounds.

Known officially as A-68A, the iceberg has been meandering north since it broke off from Antarctica’s Larsen Ice Shelf in September 2017. Measuring 94 miles long and 30 miles wide, it's nearly as big as South Georgia Island itself, and is expected to arrive sometime in the next two weeks. “They can move their own length in one day,” says David Long, director of the Center for Remote Sensing at Brigham Young University, which keeps a database of large Antarctic icebergs that are being tracked by satellite. “A few weeks is probably a reasonable estimate. When it will impact the island is hard to say.”

The island is known as the final resting place of Ernest Shackleton, the British explorer who landed there after his ill-fated expedition to Antarctica in 1915. Shackleton and two crewmen were forced to traverse the island’s rugged peaks to reach a whaling station and to organize a rescue of the remainder of his crew, who were stranded on another island 700 miles away. He returned to South Georgia Island on a later expedition and died of a heart attack in 1922.

South Georgia sits right in the middle of an alley of currents that bring bigger icebergs north from Antarctica toward the equator. Smaller ones usually break up or melt, while larger ones can remain intact for years at a time. In 2004, iceberg A38-B ran aground off South Georgia Island, leaving huge numbers of dead seal pups and young penguins. Two years ago, a Jamaica-sized iceberg named B-15 sailed past after meandering across the Southern Ocean for some 18 years, eventually breaking apart near the equator. Long says that A-68A is being swept north and might crash into the island, or sweep past it.

Seabirds such as petrels, albatrosses, and prions find refuge on South Georgia’s rocky beaches, as well as chinstrap, gentoo, and king penguins. Tens of thousands of elephant, leopard, and Wedell seals squeeze along the shoreline and are now in the middle of their mating season. Both the seals and penguins rely on the beachfront as mating and breeding grounds, and need open access to the water to catch fish—a route that a stray iceberg could obstruct.

For the penguins, even if the iceberg doesn’t entirely block access to the sea, it may force them to walk across the ice to bring back food for their young, says Michael Polito, associate professor of oceanography and coastal sciences at Louisiana State University. While penguins can walk short distances, a long hike drains their energy and makes them weaker. A big detour around an iceberg “could have a negative impact on their ability to reproduce or feed their offspring,” he says.

But what seems like a doomsday scenario for penguins might be a happy ending for some other creatures; melting icebergs become a kind of floating salad bar for creatures below, says BYU’s Long. “Icebergs collect dust from the atmosphere. They are dirty,” Long says. “As the iceberg starts to melt, the dust is distributed into the ocean. Life flourishes around these floating icebergs, you get plankton, that attracts anchovies, krill, all the way up the food chain. Every animal likes being near an iceberg because it’s a source of nutrients.” Even if the penguins have a long walk to feed, other creatures such as seals and seabirds will probably find a bounty of small fish and shrimp-like krill in the waters below.

Today, in addition to its wildlife, the island is home to a British research station that has seen its population of scientists and hardy tourists decline during the Covid-19 pandemic. British government officials are monitoring the A-68A iceberg with drone and airplane flights from the Falkland Islands, which is about 960 miles away. South Georgia Island has no airstrip, and it's too far for a helicopter ride, so the tiny crew of researchers there might be watching and hoping the iceberg doesn’t land on their side of the island, either.

Denise Landau, president of the Friends of South Georgia Island, was scheduled to spend several months there this fall doing conservation work and running a small museum for tourists. Instead, she’s watching and waiting from afar to see which direction the iceberg will take. Landau says most of the penguins and seals have their colonies on the north shore, which is roughly the shape of New York’s Long Island.

“We think it will probably ground itself before it gets that close to South Georgia. That’s what previous ones have done,” says Landau, who runs the conservation group based in Carbondale, Colorado. “Then it will break up into many pieces and begin calving smaller icebergs, like glaciers do. That may or may not affect the distances that penguins and seals have to forage at sea.”

Landau and colleagues have a big stake in the fate of the island’s birds. She was part of a 10-year project to rid the island of rats, which were one of the biggest threats to bird eggs. The island has been rat-free since 2018, and as a result the bird population has increased, Landau says.

But the number of massive icebergs—a different kind of existential threat for the island’s creatures—has slowly increased along the generally warmer Antarctic Peninsula and in areas where ice shelves have thinned and sped up the process of calving into the sea, as in the Amundsen Sea, according to Stanley Jacobs, a research scientist at Columbia University’s Lamont-Doherty Earth Observatory.

While giant icebergs like A-68A, which are the size of states or cities, are still rare—usually calving once per decade—the rate of ice loss from Antarctica is increasing. Ice losses from Antarctica tripled between 2012 and 2018, which raised global sea levels by more than a tenth of an inch (3 millimeters) that timeframe alone, according to an international climate assessment funded by NASA and European Space Agency.

Warming on the 600-mile-long Antarctic Peninsula, where air temperatures hit a record 65 degrees last February, has been even faster. In just the past 50 years, temperatures have surged 5 degrees in response to Earth’s swiftly warming climate. Glaciers along the peninsula’s coast have been warming at an accelerated pace since 2008.

As for what effect A-68A will have on the island should it crash, Jacobs says a lot depends on ocean conditions. If it arrives during a storm and high tides, that could push it further ashore into shallow water and leave it stranded for a longer period of time. “There have been large icebergs that stayed in place a decade or longer,” Jacobs says, “but eventually they melt at the base, so they start moving again.”

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