BBC News Brazil
The world’s largest iceberg is on the move after being trapped at the ocean floor for more than 30 years.
A23a, as it is called, appeared off the coast of Antarctica in 1986 but almost immediately ran aground in the Weddell Sea, essentially turning into an ice island.
At almost 4,000 square kilometers, the “island” has an area that is half the size of the greater São Paulo area and more than twice the size of the Greater London region.
The iceberg has been moving over the last year and now it is about to cross Antarctic waters.
The A23a is a true colossus and it’s not just its width that’s impressive.
This huge layer of ice is about 400 meters thick.
A23a was part of a mass calving of icebergs from the Filchner Ice Shelf in Antarctica, the White Continent.
At the time of separation there was a Soviet research station on the site.
Moscow sent an expedition to remove equipment from the Druzhnaya 1 base, fearing the material might be lost.
But the iceberg had barely moved away from the shore before its deep keel anchored it firmly in the mud at the bottom of the Weddell Sea.
But why is the A23a still in motion after almost 40 years?
“I asked a few colleagues about this and was wondering if there were any possible changes in water temperatures on the platform that could have caused this. But everyone agrees that it’s time.” [de ele se movimentar] has arrived,” explains Andrew Fleming, remote sensing specialist at the UK Antarctic Survey.
“The iceberg had been on the ground since 1986 but would eventually sink [de tamanho] enough to lose your footing and start moving. I saw the first movement in 2020.
A23a has risen in recent months, driven by winds and currents, and is now passing the northern tip of the Antarctic Peninsula.
Like most icebergs in the Weddell sector, A23a will almost certainly be thrown into the Antarctic Circumpolar Current, which will hurl it toward the South Atlantic along a path known as “iceberg alley.”
This is the same water movement and the associated westerly winds that famous British explorer Ernest Shackleton used to escape Antarctica in 1916 after his ship, the Endurance, was smashed into sea ice.
Shackleton aimed his lifeboat at South Georgia and on this island you can often see the large tabular icebergs off the coast. Because of their keels, the blocks tend to get stuck on the shallow continental shelf of the British Overseas Territory.
Ultimately, all icebergs, no matter how big, are doomed to melt.
Scientists will closely monitor the progress of A23a.
If it runs aground off South Georgia, it could cause problems for the millions of seals, penguins and other seabirds that breed on the island.
The large amount of A23a could disrupt the animals’ regular feeding routes and prevent them from adequately nourishing their young.
But it would be wrong to think of icebergs only as dangerous objects since we usually associate them with the events on the Titanic. Their importance to the environment is increasingly recognized.
When these large icebergs melt, they release a mineral powder that was incorporated into the ice when the structure was part of the glaciers that scraped away Antarctica’s long bedrock.
This type of dust is a source of nutrients for the organisms that form the basis of oceanic food chains.
“In many ways, these icebergs give life. They are the starting point of many biological activities,” says Catherine Walker from the Woods Hole Oceanographic Institute in the USA, who was born in the same year as A23a.
“I can understand that. A23a was always there for me,” she says.