World’s Biggest Iceberg on the Move After 30 Years

A23a ice

The title of the world’s largest iceberg has been contested several times. Increasingly massive pieces of the ice shelf are breaking off due to climate change. Earlier this year, a 1,550-square-kilometer iceberg named A81 broke away.

Nevertheless, A23a, covering an area of nearly 4,000 square kilometers—roughly the size of Mallorca—remains the leader. A23a detached from the Filchner Ice Shelf on the Antarctic coast as part of a mass breakout in 1986 but came to a halt in the Weddell Sea shortly afterward. Since 1991, the tabular berg has been firmly anchored on the seafloor, essentially forming an ice island.

Accelerating Pace

This changed in 2020. Since then, the massive ice colossus has begun to move slowly, as satellite data has shown. With a thickness of about 400 meters, it is roughly twice as high as the Vienna DC Tower. In recent months, A23a, driven by winds and currents, has gained momentum and is now on its way to pass the northern tip of the Antarctic Peninsula.

However, what is the reason for A23a suddenly detaching from the seafloor? “I have consulted some colleagues about whether there may have been a change in shelf water temperatures that could have triggered this, but we agree that the time has simply come,” said Andrew Fleming, a remote sensing expert at the British Antarctic Survey (BAS), who discovered the movement in 2020, to the BBC.

The giant iceberg will most likely be carried by the Antarctic Circumpolar Current, like most icebergs from the Weddell sector, and turn into Iceberg Alley, a kind of waterway for icebergs. When A23a reaches the island of South Georgia in the Southern Atlantic, the ice masses could pose a problem for the millions of seals, penguins, and seabirds breeding there, possibly disrupting their feeding routes. On the other hand, large icebergs and the minerals trapped in them are a nutrient source for many organisms.

Iceberg Tracking with AI

Iceberg A23a first began to stir from its long static slumber in 2020
Iceberg A23a first began to stir from its long static slumber in 2020. Image: BBC.

To better predict how icebergs move and change throughout their entire life cycle, from calving to melting, BAS researchers have developed an artificial intelligence tool. It is designed to process data and microwave signals from Sentinel-1 satellites, providing a more accurate picture of dynamics in the Southern Ocean. In initial tests between October 2019 and September 2020, the software identified 30,000 icebergs, most of them relatively small, ranging from one to two kilometers, as reported in the journal Remote Sensing of Environment.

Currently, all available satellite data since 2014 is being analyzed. The insights are expected to assist in detecting signals of sea level rise due to Antarctic ice melt. A digital twin of Antarctica is also being developed to depict the processes. “Monitoring and predicting how many billions of tons of ice are melting into the oceans is one of the greatest challenges due to the complex physics and the interplay of ocean, ice, and atmosphere,” says Scott Hoskin of BAS and the Alan Turing Institute, which supports the research project.

One thing is certain: It is only a matter of time until A23a continues to melt, relinquishing its title as the world’s largest iceberg.