Earth’s biggest iceberg is caught in an Antarctic spin cycle

Nearly 400 miles off the coast of Antarctica, the Earth’s largest iceberg - whose sprawling surface covers more than 1,600 square miles - is spinning like a top.

The iceberg, dubbed A23a, is caught in the churn of a powerful ocean current and revolving slowly, at a rate of around 15 degrees per day, according to the British Antarctic Survey, which shared images of the twirling iceberg on social media set to the Kylie Minogue song “Spinning Around.”

The slow-motion dance is the latest act in a decades-long journey that A23a embarked on after splitting from Antarctica in 1986. It is also staving off the iceberg’s demise. The frigid Southern Ocean vortex that A23a is caught in is slowing the iceberg’s journey north to warmer waters, where most icebergs in the region eventually drift before disintegrating, scientists told The Washington Post.

“The iceberg and the ocean are doing a cooperative dance,” said Douglas MacAyeal, a glaciologist at the University of Chicago.

A23a has had an eventful life. Its separation from Antarctica stranded a Soviet research station that had been based on the iceberg. Soon after, the colossal iceberg lodged itself on the seabed and remained anchored for around 30 years. That lengthy sojourn in the cold waters near Antarctica may have contributed to A23a’s longevity.

“It’s been lucky more than once in its life journey,” Christopher Shuman, who studies the planet’s ice at the University of Maryland, Baltimore County, said of the iceberg.

The iceberg broke free from the seabed around 2020 and was floating freely by March 2023, according to NASA’s Earth Observatory. By November, the iceberg had passed the northernmost tip of the Antarctic Peninsula, the BBC reported. That should have put A23a on the path to destruction in the warmer waters of the South Atlantic.

Instead, A23a stopped for a dance break. It became caught in an oceanic phenomenon known as a Taylor column, where the contours of the ocean floor have created a column of rotating water powerful enough to slow the iceberg’s northward drift and trap it in a continuous spin.

And so the mass of ice the size of Rhode Island has spun for months in the Antarctic, delaying the conclusion of its journey with a flourish. A23a’s jig could end eventually as the iceberg slowly melts, or more quickly if a powerful storm pushes it out of the vortex and allows it to resume its path north.

“It could be a year,” said Ted Scambos, a glaciologist at the University of Colorado at Boulder. “It could be a couple of years. It might be there for a long time.”

Although experts are watching A23a closely, Scambos said it’s unlikely the iceberg will pose any risks as it spins or when it eventually drifts onward. It won’t raise sea levels when it melts, because it’s already floating in the ocean and displacing the amount of water that it would contribute when it thaws. A23a will likely disintegrate into thousands of smaller chunks of ice when it meets its end, but Scambos said those will be easy for any ships in the region to avoid.

Until then, glaciologists can enjoy the spectacle of the world’s biggest iceberg twirling to the bitter end.

“I’ve been following icebergs since the year 2000,” Scambos said. “I’ve never seen one do something like this.”