The world’s largest iceberg, A23a, is stuck again.
For more than 30 years, the giant frozen block – the size of Rhode Island – was stuck on the seafloor in Antarctica’s coastal waters. It finally broke free in 2020 and made its way out to sea last winter.
But after a few months of traveling, viewers were amazed by what they saw: the iceberg was spinning in circles.
Using satellite imagery, the British Antarctic Survey noticed the mega iceberg rotating near the South Orkney Islands, about 375 miles from the Antarctic Peninsula, starting in January. According to the survey, A32a maintains “a cool rotation of 15 degrees per day.”
Its dancing movements are likely caused by a phenomenon in fluid mechanics known as the Taylor column, which is essentially a rotating cylinder that forms when there is an obstruction in a current. In other words, A23a is caught in a kind of ocean vortex.
Till Wagner, a professor at the University of Wisconsin-Madison who studies the interaction between ice and climate, said he had never seen a real example of this phenomenon on such a large scale.
“You know, you can easily make these Taylor columns in a rotating tank experiment in your lab. But to see them on such a geophysical scale is really rare,” he said.
There is still much to be studied about how Taylor columns might affect a behemoth like A23a. It is unclear how often Taylor columns form in the ocean and how often icebergs get trapped in them.
In the case of A23a, it is completely unclear how long it will rotate in the vortex. The iceberg melts as it rotates and Wagner is curious to see what effect this will have on life in the surrounding ecosystem, such as phytoplankton.
“It would be interesting to see if we have more phytoplankton blooms at this location next spring,” he said.
Iceberg A23a was formed in 1986 when the leading edge of the Filchner Ice Shelf broke off three icebergs. For decades, A23a was stuck on a sandbar in shallow waters. In 2020, most of A23a broke away and finally began drifting into the Southern Ocean in November.
Over the next year, the astronomer was expected to migrate northward to warmer waters, where it would rapidly melt and disintegrate. Now, the fate of A23a is a little more uncertain.
Copyright: NPR
