World's largest iceberg, A23a, is on the move after nearly 40 years

The world’s largest iceberg, known as A23a, has begun to drift after being anchored to the ocean floor for over three decades. 

The massive iceberg, measuring nearly 4,000 square kilometers, is more than double the size of Greater London.

Colossal size

A23a first separated from the Antarctic coastline in 1986. It was quickly grounded in the Weddell Sea and transformed into an ice island.

The sheer size of A23a is astounding. It has a thickness of approximately 400 meters, dwarfing Europe’s tallest skyscraper, the London Shard, which stands at 310 meters. 

History of A23a 

A23a was a significant part of a massive release of icebergs from Antarctica’s Filchner Ice Shelf. At the time that A23a first broke free, it was hosting a Soviet research station.

This prompted a Soviet expedition to retrieve equipment before it was lost. However, the iceberg did not drift far from the coast due to its deep keel anchoring it to the seabed of the Weddell Sea.

Losing its grip

Dr. Andrew Fleming from the British Antarctic Survey sheds light on why A23a has started moving after nearly 40 years. 

“I asked a couple of colleagues about this, wondering if there was any possible change in shelf water temperatures that might have provoked it, but the consensus is the time had just come,” said Dr Andrew Fleming, a remote sensing expert from the British Antarctic Survey.

“It was grounded since 1986 but eventually it was going to decrease (in size) sufficiently to lose grip and start moving. I spotted first movement back in 2020.”

Iceberg alley 

Now, A23a is rapidly drifting, influenced by winds and currents, and has reached the northern tip of the Antarctic Peninsula. It is likely to enter the Antarctic Circumpolar Current, following a path through “iceberg alley” towards the South Atlantic. 

This route, famously utilized by Sir Ernest Shackleton in 1916 for his escape from Antarctica, often leads icebergs to South Georgia Island.

What will happen next? 

The journey of A23a is under close scientific scrutiny. Should it ground at South Georgia, it could disrupt the feeding patterns of the island’s wildlife, including millions of seals, penguins, and seabirds. 

On the other hand, icebergs are not just hazards. They play a vital role in the environment. As icebergs melt, they release mineral dust, a key nutrient for oceanic food chains.

Ecological significance 

Dr. Catherine Walker of the Woods Hole Oceanographic Institution emphasizes the ecological significance of these ice giants. Born the same year as A23a, she sees a special connection with the iceberg, recognizing it as a source of life and biological activity.

The journey of A23a is a striking reminder of the dynamic and interconnected nature of our planet’s ecosystems. Its movement, after being stationary for so many years, marks a significant event in the study of polar ice and climate change.

Image Credit; European Union/Copernicus Sentinel-3/Handout/Reuters

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