Watch: Satellite video shows world's biggest iceberg, A23a, break free

A23a, the world's largest and oldest iceberg, is finally cruising again through icy ocean waters after an unexpected delay.

This summer, A23a got stuck near the South Orkney Islands, twirling in what's known as a Taylor column.

Satellite video showed the iceberg spinning whimsically in place, a process that also delays melting, and then finally breaking free.

As NPR's Juliana Kim reported in August, the Taylor column is a fluid mechanics phenomenon that can be described as "a rotating cylinder that forms when there's an obstruction in a flow" — in other words, an ocean vortex.

Of course, this is just a blip in the long, storied life of A23a. After first calving, or breaking off, from Antarctica's Filchner Ice Shelf in 1986, the iceberg spent some 30 years grounded in the seafloor of the Weddell Sea.

In 2020, A23a escaped and began its slow journey north before being caught up in the Taylor column.

The mega iceberg weighs nearly a trillion tons and is about the size of Rhode Island, according to the British Antarctic Survey.

Laura Taylor, a biogeochemist, observed A23a up close and personal last year aboard the British Antarctic Survey's BIOPOLE cruise.

"We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas," she said. "What we don't know is what difference particular icebergs, their scale, and their origins can make to that process."

Samples from the environments touched by A23a's path will give insight into the life that could come in its wake, the impact it could have on carbon levels in the ocean water and its balance with the atmosphere, Taylor said.

That is increasingly important as climate change leads to warmer temperatures and rapidly melting ice caps and glaciers.

So what's next for this Antarctic darling? The British Antarctic Survey says that if all goes according to their predictions, A23a will "continue its journey into the Southern Ocean following the Antarctic Circumpolar Current, which is likely to drive it towards the sub-Antarctic island of South Georgia."

There, the survey predicts, the iceberg "will encounter warmer water and is expected to break up into smaller icebergs and eventually melt."

But if there's anything we've learned about this funky iceberg, it's that things don't always go according to plan.