LONDON: The world’s biggest iceberg is moving after more than 30 years of being stuck to the ocean floor.
In 1986, an iceberg named A23a detached from the Antarctic coastline but quickly grounded in the Weddell Sea, transforming into an ice island. With an expansive area of nearly 4,000 sq km (1,500 sq miles), it surpasses the size of Greater London by more than twice.
Over the past year, A23a has been in swift motion and is now on the verge of extending beyond Antarctic waters. Not only is A23a notable for its considerable width, but its thickness is also remarkable, measuring about 400m (1,312 ft). To put this in perspective, the London Shard, Europe’s tallest skyscraper, stands at a comparatively modest height of 310m. A23a originated from a substantial release of icebergs from the Filchner Ice Shelf in Antarctica.
How long ago its calving occurred is demonstrated by the fact that at the time it hosted a Soviet research station.
Fearing that the equipment at the Druzhnaya 1 base would be lost, Moscow sent out an expedition to retrieve it. However, before the tabular berg got too far from the coast, its thick keel secured it firmly to the bottom muds of the Weddell.
Why is A23a moving now?
Dr. Andrew Fleming, a remote sensing expert from the British Antarctic Survey, said, “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.”
“It was grounded since 1986, but eventually, it would decrease (in size) sufficiently to lose grip and start moving. I spotted the first movement back in 2020.”
A23a has experienced a surge in movement in recent months, propelled by winds and currents, and is traversing the northern tip of the Antarctic Peninsula. Similar to the trajectory of most icebergs from the Weddell sector, A23a is expected to be expelled into the Antarctic Circumpolar Current, directing it towards the South Atlantic through a route known as “iceberg alley.”
This path aligns with the same water movement and westerlies that the renowned explorer Sir Ernest Shackleton utilized in 1916 to escape Antarctica after losing his ship, the Endurance, in the grip of crushing sea ice.
Shackleton navigated his lifeboat toward South Georgia, an island frequently frequented by large tabular icebergs. Due to their keels, these icebergs tend to become lodged on the shallow continental shelf of this British Overseas Territory. Regardless of their size, all icebergs are destined to melt and gradually disappear over time.
Scientists will be closely following the progress of A23a.
If A23a ground in South Georgia, it could pose challenges for the island’s diverse wildlife, including millions of seals, penguins, and seabirds that breed there. The substantial size of A23a has the potential to disrupt these animals’ usual foraging routes, hindering their ability to feed their offspring adequately.
However, it would be a misconception to view icebergs solely as hazards, reminiscent of the Titanic incident. There is a growing acknowledgment of their significance in the broader environment. As these large icebergs undergo melting, they release mineral dust that was initially embedded in their ice during their time as part of glaciers scraping along the rock bed of Antarctica. This dust serves as a valuable source of nutrients for the organisms forming the foundation of ocean food chains.
Dr. Catherine Walker, from the Woods Hole Oceanographic Institution, born in the same year as A23a, said, “In many ways, these icebergs are life-giving; they are the origin point for a lot of biological activity. I identify with it; it’s always been there for me.”
