After breaking free, why the world’s largest iceberg is stuck spinning in circles

Sub: Geo

Sec: Hydrology

Context:

For over three decades, the world’s largest iceberg, A23a, was trapped in the Antarctic, measuring about 1,500 square miles in area and over 1,000 feet deep.
It broke free in 2020 and began a slow drift towards the Southern Ocean.
Currently, A23a is spinning in place near the South Orkney Islands, about 375 miles northeast of the Antarctic Peninsula, stuck in a vortex above a seamount.

About A23a iceberg:

A23a originated from A23, one of three massive icebergs calved from the Filchner Ice Shelf in 1986. It remained lodged in the Weddell Sea until 2020.
Freed in December 2020, A23a began moving out of Antarctic waters but was caught in a Taylor column, a type of ocean current formed around underwater mountains.

The Phenomenon of Spinning:

Taylor Column: A23a is caught over a seamount about 62 miles wide and 3,280 feet high, causing it to rotate slowly in place.
This stagnation, caused by the current’s flow diverging around the seamount, creates a cylinder of water that spins the iceberg counterclockwise.

Impact and Implications:

Marine Environment: If A23a remains in the vortex for a long time, it could significantly melt, affecting plankton and other marine organisms in the area.
Global Sea Levels: Melting icebergs like A23a, which come from floating ice shelves, do not directly contribute to sea level rise because they are already in the ocean. However, the degradation of ice shelves could increase the vulnerability of Antarctic glaciers to warming.

Observations and Future Outlook:

The British Antarctic Survey began observing A23a’s spinning motion in April 2021.
It is unknown how long the iceberg will continue to spin in place, as similar phenomena have previously lasted for several years.

Source: IE