Satellites watch world's largest iceberg break away from Antarctica (photos)

a white clump of iceberg sits below wispy clouds
International Space Station Expedition 70 astronauts shared a view of A23a, taken on Nov. 21 from the orbiting lab. (Image credit: European Union, Copernicus Sentinel-1 imagery — Processed by @CopernicusEU)

The world's largest iceberg is drifting beyond Antarctic waters and satellites are tracking its movement from space.

The iceberg, called A23a, has broken loose and is moving past the northern tip of the Antarctic Peninsula after being grounded for more than three decades. Recent satellite images reveal that the iceberg, weighing nearly a trillion tons, is drifting at a rate of three miles each day, aided by strong winds and ocean currents, Smithsonian Magazine reported

The European Space Agency's Copernicus Sentinel-1 mission has been closely tracking the movement of A23a. Copernicus EU shared four separate satellite images comparing the iceberg’s changing position over the last month in a post on X (formally Twitter). The images were taken on Oct. 19 and 31, and Nov. 12 and 24 by the Sentinel-1A satellite.

Related: Wow! Iceberg larger than London breaks off Antarctica (photos)

The British Antarctic Survey shared a timelapse video of the iceberg’' movement using the satellite imagery captured by the Copernicus Sentinel-1 imagery and Google Earth Engine. 

The Copernicus Sentinel-1 mission shared satellite images taken on October 19 and 31, and November 12 and 24, showing the trajectory of iceberg A23a.   (Image credit: European Union, Copernicus Sentinel-1 imagery — Processed by @CopernicusEU)

"The largest iceberg, A23a, is on the move!” The British Antarctic Survey said in its post on X (formally Twitter). "Here's its journey out of the Weddell Sea after being grounded on the seafloor after calving in August 1986."  

Measuring about 1,500 square miles (4,000 sq km), the iceberg is roughly three times the size of New York City and more than twice the size of Greater London. While it split from the Antarctic's Filchner Ice Shelf in 1986, it became stuck to the ocean floor in the Weddell Sea, where it had remained grounded for the last 37 years. 

While researchers haven’t identified a specific event that would have initiated the drifting, it is believed that the iceberg may have thinned over time, providing extra buoyancy that’s allowed it to lift off the ocean floor, after which strong winds and ocean currents would be able to move the iceberg along its current trajectory, according to Oliver Marsh, a glaciologist at the British Antarctic Survey. 

Astronauts on the International Space Station have also been able to track the iceberg's movement out of the Weddell Sea, which is part of the Southern Ocean between Antarctica and South America. Expedition 70 shared a view of A23a, taken on Nov. 21 from the orbiting lab. 

Expedition 70 shared a view of A23a, taken on Nov. 21 from the orbiting lab.  (Image credit: NASA)

Researchers first noticed A23a moving again in 2020. However, the iceberg has been moving faster in recent months. Now that it has reached the top of the Antarctic Peninsula, the iceberg is expected to head east along the Antarctic Circumpolar Current, which will carry it towards the South Atlantic on a path known as "iceberg alley."

The iceberg's movement has raised some concerns about wildlife, as it could disrupt seals, penguins and other seabirds that breed and forage in the surrounding waters. Therefore, scientists and satellites will continue to follow the iceberg closely. 

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Samantha Mathewson
Contributing Writer

Samantha Mathewson joined as an intern in the summer of 2016. She received a B.A. in Journalism and Environmental Science at the University of New Haven, in Connecticut. Previously, her work has been published in Nature World News. When not writing or reading about science, Samantha enjoys traveling to new places and taking photos! You can follow her on Twitter @Sam_Ashley13.