A23a: The world's largest iceberg starts moving after 30 years. BBC
The world's largest iceberg, A23a, has been spinning in place for several months and may continue to do so. The British Antarctic Survey confirmed that this massive iceberg, about the size of Cornwall, is stuck in an ocean vortex near the South Orkney Islands, rotating at a steady 15 degrees per day.
This giant iceberg, which is around 3,900 square kilometres (twice the size of Greater London or four times the size of New York City), broke off from the Filchner-Ronne Ice Shelf in 1986. It remained stationary in the Weddell Sea until 2020 when it began moving due to underwater melting.
Throughout the summer of 2023, A23a drifted with the currents in the Weddell Sea. However, by November, it had settled into a spin near the Antarctic Peninsula. The British Antarctic Survey has been tracking the iceberg's journey using satellite imagery, noting its significant movements.
In February, the iceberg made a full rotation and started moving towards a northerly current. However, it soon got trapped in a Taylor column, a phenomenon where water flows around a submerged object, causing it to spin in place. This can be visualized by imagining a hockey puck in a rotating aquarium, with the water forced to move around the puck.
Professor Kent Moore from the University of Toronto Mississauga explained that this effect is caused by underwater mountains, or seamounts, which are keeping the iceberg in its current position. He believes that the iceberg will likely remain stuck in the Taylor column and eventually melt there.
As of August 2, the U.S. Ice Center reported that the iceberg is located roughly halfway between the Antarctic Peninsula and South Georgia Island, near the South Orkney Islands, within the Antarctic Circumpolar Current (ACC). The ACC is the world's largest ocean current, circulating water across the Atlantic, Pacific, and Indian Oceans, and plays a role in the warming of the Southern Ocean.
It's rare for an iceberg to get trapped in a Taylor column, and Moore mentioned that this is likely the first time such a phenomenon has been observed. The iceberg is expected to stay in place and gradually melt over time.
