Images of the world’s largest glacier have been captured by NASA as it moves towards its demise in warmer waters.
The iceberg, named A-23A (sometimes called A23a), had just escaped an ocean current eddy that had trapped it just north of the South Orkney Islands for months, rotating more or less counter-clockwise in place at about 15 degrees each day.
Now the iceberg has broken free from this watery cage and is drifting northeast toward South Georgia Island, where it is expected to break up and melt into oblivion.
NASA images reveal the path of this huge ice sheet as it broke into the open waters of the Southern Ocean and eventually escaped the grip of Antarctica.
NASA Earth Observatory images by Lauren Dauphin
These images were taken by MODIS (Moderate Resolution Imaging Spectroradiometer) and VIIRS (Visible Infrared Imaging Radiometer Suite) instruments on several NASA and National Oceanic and Atmospheric Administration satellites.
As of Friday, A-23A has an area of about 1,062 square miles, according to the U.S. National Ice Center, which is about twice the size of Los Angeles. The glacier was previously larger, about the size of Rhode Island, reaching 1,700 square miles in November 2023.
In 1986, the A-23A initially broke off the Filchner-Ronne Ice Shelf near the Antarctic Peninsula, but almost immediately anchored to the seabed in the southern Weddell Sea. The iceberg remained there for more than 30 years until it finally floated free in 2020, probably due to melting, and drifted north along the Antarctic Peninsula. Then, in the summer of 2024, the A-23A got stuck in a Taylor plume – a rotating current – over a hump on the ocean floor called Pirie Bank.
“It’s exciting to see A23a moving again after periods of being stuck. We wonder if it will follow the same path as the other large glaciers that have calved off Antarctica,” said Andrew Meijers, an oceanographer at the UK Antarctic Survey and co-leader of the OCEAN:ICE project. in the statement.
Map created using data from the Antarctic Glacier Monitoring Database and the US National Ice Center
More than 90 percent of the Antarctic ice sheets end up floating in a clockwise current called the Weddell Gyre, which winds along the east coast of the Antarctic Peninsula just as the A-23A did originally. This route is called Iceberg Alley and is the last route for most icebergs as they are driven north into warmer waters to their inevitable demise.
However, some glaciers take a detour along the way, including glacier A-68A, which briefly spun in the Drake Passage in 2017, and A-23A itself. During its time in the Taylor column, the A-23A was seen to make a total of 15 turns while turning.
“I am not aware of an iceberg that has been trapped in such a persistent manner in such a small area,” Jan Lieser, an ice specialist with the Antarctic Weather Service who tracked the A-23A, said on the NASA Earth Observatory blog. post.
The glacier has traveled about 150 miles since escaping from Taylor’s column and headed northeast. What exactly caused the A-23A to emancipate itself from the current remains unknown.
“My hypothesis is that a random perturbation in the system may have caused a slight change in the ‘usual’ rotation, so the glacier found an escape route,” Lieser said.
In the coming months, A-23A will slowly shrink, break up and melt, and the title of “largest glacier” will pass to another.
