A23a & Taylor Columns

In 1986, a gargantuan ice chunk calved from the Filchner-Ronne Ice Shelf in Antarctica.

The size of this iceberg – creatively dubbed A23a – is hard to comprehend. It was so big that, after it separated, it did not move. Estimated to be more than 1,100 feet tall and weighing nearly a trillion tons, the ice stuck into the seabed.

For more than 30 years.

Slowly, the edges of the iceberg melted. In 2020, enough mass had dissipated that the ice finally began to float away from its former home. Scientists watched the world’s largest iceberg via satellite and boat, waiting to see where it would go.

As it bobbed in the frigid Atlantic, drifting northward with ocean currents, A23a remained incredibly large. As the BBC pointed out, in early 2024, almost 40 years after it broke from the shelf, the iceberg was still larger than 29 countries, twice the size of Greater London, and would take up a large swath of the English Channel.

Despite its size, A23a would someday succumb to warmer waters, warmer air, and wave action. It passed South Orkney Island and seemed to be on a course for South Georgia Island, where Ernest Shackleton famously sailed for rescue in 1916.

Many icebergs turn to slush by the time they reach South Georgia. Scientists believed that fate belonged to A23a, as well, but something curious happened on the way to the remote isle.

By April 2024, the iceberg stopped moving.

In the middle of the planet’s most potent ocean current.

And it started spinning.

Sadly, the culprit of this bizarre phenomenon is not the influence of extraterrestrials but the complex fluid dynamics of a spinning planet. This natural occurrence is no less fascinating than out-of-this-world intervention, though.

Picture a bathtub. If you place a hockey puck on the bottom, introduce some food coloring, and then produce a current across the puck, the dye will move over and around the puck. The important factor of the system is that the water in the tub is not rotating.

When the frame rotates, a spectacle known as the Coriolis effect kicks in. Physicist Sir Geoffrey Ingram Taylor realized that an ocean current that hits an impediment would, instead of moving over the object, flow around it. The Coriolis effect is an inertial force that deals with rotating frames of reference in which potential vorticity is maintained. This fancy terminology means that the horizontal movement of the water is maintained but the vertical movement is suppressed. The result is a column of water that forms over the impediment at all heights, fittingly called a Taylor column. These vertical areas effectively become invisible vortexes.

Watching the effect in the lab might be more beneficial than reading a clunky explanation:

Back to A23a.

On its journey toward South Georgia, the iceberg passed over a feature called the Pirie Bank. This “bump” is 62 miles wide, large enough for the ocean currents to create a massive Taylor column.

A23a, the truly monumental hunk of ice, unable to escape the physics of the water, currently resides in a vortex. The iceberg began to spin counterclockwise in the column, by as much as 15 degrees a day.

And, just like that, the iceberg’s march toward oblivion hit the pause button. Spinning in the relatively cold water of the Pirie Bank will keep the ice from melting too quickly.

A23a could be stuck in this Taylor column for quite a while. A buoy above another Taylor column to the east has been unable to escape for more than four years.

It’s possible that, unlike Earnest Shackleton, A23a never makes it to South Georgia Island. Ironically, while getting there saved Shackleton, not reaching it might prolong the life of the world’s biggest iceberg.