Iceberg splits from Antarctica, becoming world’s largest

An iceberg nearly half the size of Puerto Rico has broken off the edge of Antarctica, becoming what researchers said was the world’s largest iceberg.

The iceberg, known as A76, following a naming convention established by the National Ice Centre, naturally split from Antarctica’s Ronne Ice Shelf into the Weddell Sea last week through a process known as calving, the centre said.

It measures about 1,668 square miles (4,320 square kilometres), making it larger than A23a, an iceberg that formed in 1986 and had a total area of more than 1,500 square miles (4,000 square kilometres) in January.

Researchers sought to put the formation of A76 in context, saying that the forces that severed it from the Ronne Ice Shelf were part of the shelf’s normal life span and may not be directly related to climate change.

The iceberg will not add to sea level rise; as floating ice, it is already displacing the same volume of water it will add as it melts.

Christopher A Shuman, a research professor at the University of Maryland, Baltimore County, likened the Ronne Ice Shelf’s calving process to a manicure: If it’s the white part of your fingernail that gets clipped off, it’s not a problem.

“There is really essentially no sign that this is an unusual event with climate significance,” Shuman said.

The formation of the iceberg does, however, bring renewed attention to the broader issue of ice loss in both the Antarctic and Greenland, said M Jackson, a glaciologist and an explorer with the National Geographic Society. Although the Weddell Sea is not warming as quickly as other parts of the Antarctic, she said, the impact of climate change in the region cannot be discounted, and it is hard to disconnect what happened with the Ronne Ice Shelf from the larger problem.

“I am concerned with any ice loss today, because any ice loss is part of our greater global ice loss, and to me it’s terrifying,” Jackson said. “Globally, we’ve got a glacier problem; we’re losing a lot of ice.”

The largest iceberg on record, B15, broke off from the Ross Ice Shelf in March 2000, measuring more than 4,200 square miles (11,000 square kilometres). Despite being more than twice the size of A76, Shuman said, B15 did not destabilise the Ross Ice Shelf. B15 has since fractured into several icebergs, all but one of which have melted away.

According to Shuman, the last significant calving event on the Ronne shelf was in May 2000.

By studying the new iceberg, researchers hope to better understand the overall state of Antarctica’s ice shelves, said David Long, who runs the Antarctic Iceberg Tracking Database at Brigham Young University.

“Understanding when the ice sheets calve helps us understand whether some of these other more unstable ice sheets could break up or disintegrate,” he said. “And that would be important because as these more unstable ice sheets break up they can release the flow of glaciers that are held in place by the ice shelves.”

While ice shelves are floating on the water, the glaciers behind them are on land. So if they are released into the sea and melt, that would add to sea levels, he said.

The National Ice Centre names and tracks Antarctic icebergs that are at least 10 nautical miles long or 20 square nautical miles large. The centre, which is operated by the Navy, the Coast Guard and the National Oceanic and Atmospheric Administration, is currently tracking 42 named icebergs.

The question with A76 is what will happen next.

An iceberg about 100 miles long and 30 miles wide that had broken off from the Antarctic Peninsula in 2017 raised alarm in November when it appeared to be on a collision course with the British island territory of South Georgia. That iceberg, A68a, ended up grounding off the island’s coast. If A76 hits a similar current, it could reach the Antarctic Peninsula within months and could interfere with shipping lanes there, said Christopher Readinger, the Ice Centre’s Antarctica team lead.

As A76 makes its journey, Jackson said, climatologists will be watching closely — even if much of the public isn’t. Jackson cited A68a, the iceberg that briefly threatened South Georgia.

“The whole world was going crazy about that, and then everyone forgot it, right?” she said. “This one’s going to be in the imagination until the next big one, and the next big one and the next big one. And it’s part of the larger global problem. We’re losing our world’s ice, and I frankly don’t want to live in a world without ice.”

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