A23a, an iceberg five times the size of New York City, was caught in a giant vortex and could be stuck there for years.
The iceberg, called A23a, is about 1,600 square miles (4,248 square kilometers) in area, slightly larger than the state of Rhode Island and five times larger than New York City. A23a broke away from Antarctica’s Filchner-Ronne Ice Shelf in 1986 but became trapped in the Weddell Sea after pushing against the seabed, eventually drifting away from the icy continent in 2020, according to Newsweek.
Now, instead of entering the warmer waters of the South Atlantic via the Antarctic Circumpolar Current, the iceberg is trapped in a rotating current called the Taylor Column. The iceberg, which is located north of the uninhabited South Orkney Islands, rotates counterclockwise about 15 degrees a day. As a result, instead of melting slowly as expected, the giant iceberg may persist until it leaves the Taylor Column. “A23a is an iceberg that refuses to die,” said Mark Brandon, a polar expert and professor at the Open University.
A Taylor Column eddy occurs when a liquid, such as ocean water, flows over a submerged object in a rotating system similar to Earth. In this case, the eddy is the result of a hump on the seafloor called Pirie Bank. This type of obstruction causes the ocean current to split, creating a rotating eddy above the object. The iceberg gets trapped in this eddy, spinning continuously.
According to Mike Meredith, a professor at the British Antarctic Survey, a Taylor Column can form in the air. It can be just a few centimeters wide in a tank in the lab or be as huge as this one, taking the iceberg with it.
For now, A23a has escaped the inevitable fate of icebergs that break away from Antarctica: melting. Antarctica had its lowest winter sea ice extent last year, nearly 1.8 million square kilometers below average. Antarctica is losing ice at an accelerating rate. The rate of sea ice loss increased sixfold in the 30 years leading up to 2020. According to a study published in the journal Nature in 2018, Antarctica lost about 3,000 billion tons of ice between 1992 and 2017. The rate of ice loss increased from 76 billion tons per year before 2012 to 219 billion tons per year in recent years.
The melting of Antarctic ice is a significant contributor to global sea level rise, with current estimates suggesting that ice loss in Antarctica alone is responsible for a global sea level rise of 0.4 millimeters per year. If the West Antarctic Ice Sheet were to collapse completely, sea levels would rise by several meters, affecting coastal communities around the world.
