New York: An iceberg larger than Rhode Island that broke off an Antarctic ice shelf in 2017 is closing in on South Georgia Island, a British territory in the South Atlantic Ocean. The iceberg, designated A68a by the National Ice Center, is being steered by ocean currents to a position closer to the island, which is home to large colonies of penguins, seals and other unique wildlife.
The iceberg is less than 31 miles off the coast of South Georgia Island, and a shallow shelf area is extending from the island, possibly toward a collision if ocean currents push the iceberg northward.
The iceberg is more than 650 feet thick, with about nine-tenths of it underwater, according to David Long, director of the center for remote sensing at Brigham Young University who has been tracking the iceberg. Above the water, the iceberg features steep cliffs along its edges.
"If it does hit the island, it will hit the undersea shelf and ground offshore," Long said via email. "Note that the island and iceberg are about the same size!"
Should the iceberg, which is about 93 miles long and 30 miles wide, become grounded just off the coast, it could become difficult for the millions of king and macaroni penguins, seals and seabirds to find food, such as fish, forcing them to travel long distances around the iceberg. Blue whales feed just off the coast of the island, and this could complicate their access to krill.
Long had thought the iceberg would be at risk of getting stuck on South Georgia Island's eastern side, but it has not met those expectations.
"I originally thought that A68a would pass south of South Georgia Island, then be swept back to ground on the east side of the island like previous similarly large icebergs," he said.
The iceberg's precise movements in coming days and weeks are unpredictable because the mass is steered by ocean currents and storms can affect it. But its proximity to the island makes a collision probable.
Mark Belchier, director of fisheries and environment for the government of South Georgia and the South Sandwich Islands, told BBC News that wildlife on the island are at a particularly sensitive point in their life cycle because it's a critical time of year for breeding.
"The nests have been built for Gentoo penguins, and eggs will be laid soon. And the first seal pups have been born in the last two weeks," he said. "Christmas is normally the peak of breeding activity."
Geraint Tarling, an ecologist at the British Antarctic Survey, said in a Nov. 4 news release that the iceberg could have "massive implications" for local species, especially if becomes stuck there for a long time.
"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 [fish and krill] really matters," Tarling said. "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."
The Royal Air Force flew over the iceberg this week to get a better idea of its size, stability and motion. "The imagery stills, video footage and visual observations will all assist in predicting the iceberg's future behaviour and ascertaining the scale of the threat to the local area," the British Forces South Atlantic Islands said on Facebook.
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When A68a broke away from the Larsen C ice shelf in Antarctica in July 2017, it measured nearly 2,300 square miles - about the size of Delaware. By shedding ice at its edges and breaking off chunks as it travels through the rough waters of "Iceberg Alley," the mass is now smaller, at about the size of Rhode Island.
The Antarctic Peninsula, where the Larsen C Ice Shelf is located, is one of the fastest-warming areas in the world. In February, a temperature of nearly 70 degrees was recorded on Seymour Island in the Antarctic Peninsula.
As ice shelves such as Larsen C melt, they free up inland ice to move into the ocean, raising sea levels. Many other parts of the Antarctic ice sheet are showing signs of instability.
The Pine Island Glacier is melting, shedding icebergs. An international scientific effort is underway to better understand the fate of Pine Island and Thwaites glaciers, which already constitute about 5% of global sea level rise.
Should Thwaites be lost, it could cause the West Antarctic Ice Sheet to slide into the sea, raising global average sea levels by about 10 feet.
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