The World’s Largest Iceberg Is Free-Floating Again, and It Could Help Build ‘Thriving Ecosystems’

After spending the last few months stuck in a swirling ocean vortex, the world’s largest iceberg is floating freely once again.

Called A23a, the massive hunk of ice spans roughly 1,500 square miles—which makes it about the same size as Rhode Island. It weighs nearly one trillion metric tons and measures around 1,300 feet thick.

A23a broke off from Antarctica in August 1986. It was part of the Filchner-Ronne ice shelf on the continent’s northwest side and had been home to a Soviet research station. (After the iceberg separated from Antarctica, however, Soviet scientists recovered their equipment.)

A23a megaberg escapes after months in ocean vortex | British Antarctic Survey

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A23a didn’t travel far before becoming grounded on the floor of the Weddell Sea between Antarctica and South America. It stayed there, motionless, for decades.

Then, in 2020, the iceberg started moving again. Ocean currents and the wind were pushing A23a through the Weddell Sea at a rate of up to three miles per day, researchers said late last year. But in August 2024, it got sidetracked—A23a became trapped in a spinning ocean vortex near the South Orkney Islands. It rotated roughly 15 degrees each day in what’s known as a Taylor column, but did not move otherwise.

Now, A23a has broken free from that aimless rotation and is on the move again. On Friday, the British Antarctic Survey announced that the mega-iceberg is drifting in the Southern Ocean.

Scientists have been following A23a’s journey in hopes of learning more about how icebergs influence the world’s oceans. Last year, a team sailed aboard the research vessel RRS Sir David Attenborough to take photos and gather data near A23a.

More specifically, researchers took surface water samples from behind, next to and in front of A23a. They hope to understand how icebergs like A23a affect the waters around them.

“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas,” says Laura Taylor, a biogeochemist with the British Antarctic Survey and the University of Cambridge, in a statement. “What we don’t know is what difference particular icebergs, their scale and their origins can make to that process.”

New animation shows track of giant A23a iceberg | British Antarctic Survey

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Experts expect A23a to travel northward along the Antarctic Circumpolar Current. It will likely head toward South Georgia Island, where warmer waters await. The higher temperatures will probably cause A23a to melt and break into smaller chunks.

Large icebergs periodically break away from Antarctica as part of the natural growth cycle of ice shelves. Christopher A. Shuman, a cryospheric scientist at NASA’s Goddard Space Flight Center and the University of Maryland, Baltimore County, has compared the process to trimming your fingernails. Calving icebergs are like the white tips of fingernails, he told the New York Times’ Claire Fahy in 2021—they separate from the ice sheet but are gradually replaced.

Scientists say natural iceberg calving is not linked to climate change and that mega-icebergs do not contribute to sea-level rise. However, as global temperatures continue to increase, experts are concerned about melting ice sheets in Antarctica, as well as in Greenland.

A23a may be the largest iceberg on the planet at the moment—but it hasn’t always held that title. In July 2017, A68 became the world’s largest iceberg after it calved from the Larsen C ice shelf on the Antarctic Peninsula. Measuring roughly 2,200 square miles, A68 drifted north toward South Georgia and split into smaller pieces.

Similarly, in May 2021, A76 separated from the Filchner-Ronne ice shelf and temporarily became the world’s largest iceberg. A76 split into three smaller pieces, however, leading A23a to reclaim its crown.

The largest iceberg ever recorded was named B15. It broke off from Antarctica’s Ross Ice Shelf in March 2000 and slowly drifted northward. At its peak, the iceberg had a surface area of 4,250 square miles—making it bigger than Jamaica. But in 2015, even it broke down, separating into eight chunks that got smaller and smaller as they melted. By 2018, just four large segments remained, and they showed signs of degrading, too.

Sarah Kuta | READ MORE

Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.