World's Largest Iceberg No Longer Headed to 'Oblivion'

At least not yet: A23a, trapped in a water vortex, is expected to survive for years more
By Arden Dier,  Newser Staff
Posted Aug 6, 2024 12:28 PM CDT
World's Largest Iceberg 'Refuses to Die'
This image shows the A23a iceberg moving through the sea near Antarctica on Nov. 15.   (Satellite image 2023 Maxar Technologies via AP)

To be an iceberg is to be on the verge of death. Once broken off a glacier or ice shelf, icebergs typically melt within a few years. But the world's largest iceberg, which appeared to be on a slow death march late last year, is now expected to survive quite a bit longer. A23a—which measures 1,500 square miles, or three times the size of New York City, per CBS News—has for months been stuck on top of a rotating column of water just north of Antarctica, where it's expected to stay for years. As polar expert and Open University researcher Mark Brandon tells the BBC, "A23a is the iceberg that just refuses to die."

A23a first broke off Antarctica's coastline in 1986 before grounding on the bottom of the Weddell Sea. It survived as an ice island until 2020, when it refloated and again began to drift. It moved northward toward warmer waters and, in April, met the Antarctic Circumpolar Current, which should've carried it to "certain oblivion" in the South Atlantic, per the BBC. Instead, A23a has essentially stayed put, just north of South Orkney Islands. Sitting on top of a churning column of water, known as a Taylor column, it's slowly spinning counterclockwise on the spot, per the Telegraph.

When a current meets an obstruction—like the Pirie Bank, a long "bump" on the ocean floor beneath the now-spinning iceberg—it can separate into two distinct flows, which spin together, creating a vortex. Taylor columns "can be just a few centimeters across in an experimental laboratory tank or absolutely enormous, as in this case where the column has a giant iceberg slap-bang in the middle of it," Mike Meredith of the British Antarctic Survey tells the BBC. It's not known how long this vortex will hold the trillion-ton A23a, preventing its death in warmer waters. But Brandon left a scientific buoy in another Taylor column, just east of Pirie Bank, and found it still in place four years later. (More icebergs stories.)

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