Imagine spending over 30 years grounded in the Weddell Sea, finally breaking free, only to get stuck again less than four years later – and this time, you can’t stop spinning. That’s the unfortunate reality for the world’s largest iceberg, A23a.
It was first declared in its “spinning era” by the British Antarctic Survey (BAS) earlier this year, after imagery captured by instruments aboard NASA satellites between December 2023 to February 2024 showed the iceberg beginning to rotate in place in early January.
Since then, the 4,000 square-kilometer (1,500 square-mile) berg has remained trapped near the South Orkney Islands – but why?
A23a is the unfortunate victim of what’s known as a Taylor column, a rotating cylinder of water that can form when an ocean current – in this case, the Antarctic Circumpolar Current – meets a seamount – Pirie Bank in the Scotia Sea.
The prospect of A23a ending up stuck and spinning in such a way wasn’t entirely unpredictable – it’s happened to other icebergs traversing similar routes in the past. However, the berg’s giant size makes this a particularly unusual sight.
“You know, you can make these Taylor Columns quite easily in a rotating tank experiment in your lab,” Till Wagner, Assistant Professor in Ice and Climate Physics at the University of Wisconsin-Madison, told NPR. “But to see it on a geophysical scale like this is really rare.”
A23a getting spinny with it this month so far.
Image credit: NASA Worldview
Though it might be fun to be the star of a rare event, if icebergs were sentient, we imagine A23a would be more than a bit fed up by now with its unexpectedly long journey away from its birthplace.
The berg, which is bigger than the state of Rhode Island, first calved off Antarctica’s Filchner–Ronne Ice Shelf back in 1986 – but became grounded on nearby seabed shortly after.
It took until 2020 for A23a to finally get moving again and start making its way out of the Weddell Sea, after which it briefly lost its title as “world’s biggest iceberg” to A76, though the competitor would eventually end up in pieces thanks to the extreme conditions of the Drake Passage.
Fast forward to today, and A23a is stuck once again, having been so for coming up to eight months. As for how much longer it’ll stay spinning before eventually breaking free and continuing its journey, that’s unclear – others have stayed like that for several weeks, so it’s already beating the odds.
As Open University researcher and polar expert Professor Mark Brandon put it to the BBC: “Usually you think of icebergs as being transient things; they fragment and melt away. But not this one.”
“A23a is the iceberg that just refuses to die.”
Source Link: The World’s Biggest Iceberg Has Been Stuck Spinning For Nearly 8 Months
