Largest iceberg in the world moves again after 30 years – 11/24/2023 – Science

The world’s largest iceberg is on the move after more than 30 years trapped at the bottom of the ocean.

A23a, as it is called, appeared off the coast of Antarctica in 1986 — but almost immediately ran aground in the Weddell Sea to become, essentially, an island of ice.

With almost 4,000 square kilometers in area, it is more than twice the size of the London metropolitan area.

Over the last year, the iceberg has been moving — and now it is about to go beyond Antarctic waters.

The A23a is a true colossus — and it’s not just its width that’s impressive.

This huge sheet of ice is about 400 meters thick.

A23a was part of a mass calving of icebergs from the Filchner Ice Shelf, located in Antarctica, the white continent.

At the time of separation, the site housed a Soviet research station.

Moscow dispatched an expedition to remove equipment from the Druzhnaya 1 base, fearing that the material would be lost.

But the iceberg didn’t move far from shore before its deep keel anchored it rigidly in the mud at the bottom of the Weddell Sea.

But then why is the A23a on the move now, after almost 40 years?

“I asked a few colleagues about this, wondering if there were any possible changes in water temperatures on the platform that could have caused this. But the consensus is that the time [de ele se movimentar] has arrived,” explains Andrew Fleming, remote sensing specialist at the UK Antarctic Survey.

“The iceberg had been grounded since 1986, but would eventually subside [de tamanho] enough to lose grip and start moving. I saw the first movement in 2020.”

A23a has soared in recent months, driven by winds and currents, and now passes the northern tip of the Antarctic Peninsula.

Like most icebergs in the Weddell sector, A23a will almost certainly be ejected into the Antarctic Circumpolar Current, which will launch it toward the South Atlantic in a path that has become known as “iceberg alley.”

This is the same movement of water — and the westerly winds that accompany it — that famous British explorer Ernest Shackleton used in 1916 to escape Antarctica after losing his ship, the Endurance, crushed against sea ice.

Shackleton pointed his lifeboat towards South Georgia — and it is on this island that the large tabular icebergs located off the coast are often seen. The blocks’ keels mean they tend to get stuck on the shallow continental shelf of the British Overseas Territory.

Eventually, all icebergs, no matter how big, are doomed to melt.

Scientists will closely monitor A23a’s progress.

If it does run aground off South Georgia, it could cause problems for the millions of seals, penguins and other seabirds that breed on the island.

The large volume of A23a could disrupt the animals’ regular feeding routes, preventing them from adequately nourishing their young.

But it would be wrong to think of icebergs as just objects of danger — as we usually link them to what happened with the Titanic. There is growing recognition of their importance to the wider environment.

As 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 Antarctica’s long bedrock.

This species 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 point of origin of a lot of biological activity”, assesses Catherine Walker, from the Woods Hole Oceanographic Institute, in the USA, who was born in the same year as A23a.

“I relate to that. A23a has always been there for me,” she says.