After months of drifting, the world’s largest iceberg has come to a halt near the island of South Georgia in the South Atlantic Ocean.
While a “Titanic II” scenario isn’t very likely, and the area’s penguins seem to be mostly safe, the berg may be a symptom of unwelcome change to the Antarctic and the planet.
How did we get here?
A23a, as the iceberg is officially known, was born in 1986 when it broke off from another iceberg, A23, that had torn away from Antarctica earlier that year. The separation of a smaller ice chunk from a larger one is called calving.
Its early life was uneventful; it sat in the Weddell Sea, east of the Antarctic Peninsula, for decades.
A23a’s travels began in 2020, when it freed itself from the sea floor and began to move. By 2023, it was ready to leave Antarctic waters entirely.
This spring its progression hit a snag when it began spinning about in place, caught in a current known as a Taylor column near the South Orkney Islands.
Escaping after several months of spinning, it then headed for South Georgia, an island east of the southern tip of South America that is a British territory and home to a couple dozen people and many seals and penguins.
So, after that it just stopped?
Yes. It couldn’t make it all the way to South Georgia, and is now stuck on the continental shelf, about 50 miles from the island.
So far it seems to be sitting peacefully and has not begun breaking into smaller pieces, as some other giant bergs have after splitting from Antarctica.
How big is this thing?
Initially it was measured to be about 1,500 square miles. It has lost some of that girth, but still is believed to be more than 1,300 square miles. In contrast, New York City is 300 square miles.
Icebergs that big are rare, Andrew Meijers, an oceanographer at British Antarctic Survey, said in a statement on the group’s website. “There have been two other similarly sized bergs in the same region over the past five years or so, and sporadically before that,” he said.
“It looks like land, that’s the only way to describe it,” Alexander Brearley, a physical oceanographer at the British Antarctic Survey, said last summer.
The iceberg that sank the Titanic was perhaps a quarter-mile long, a laughably tiny thing in comparison.
“A23a” is kind of dry. You’d think they could do a bit better.
That’s science for you. “A” indicates the region of Antarctica in which the iceberg was formed. The numbers are assigned sequentially, and the little “a” means it broke off from a bigger berg.
More colorful coinages like “superberg” or “icemonster” would be sadly unscientific.
What’s next?
A23a will begin to break up and melt, though it will probably take a while, maybe years.
“Now it’s grounded, it is even more likely to break up due to the increased stresses, but this is practically impossible to predict,” Dr. Meijers said. “Large bergs have made it a long way north before — one got within 1,000 kilometers of Perth, Australia once — but they all inevitably break up and melt quickly after.”
Is this all a good or bad thing?
It is unlikely that the seals and penguins of South Georgia will be affected by the iceberg. Still, “Potentially, it could interrupt their pathway to feeding sites and force the adults to expend more energy to travel around it,” Dr. Meijers said. “This could reduce the amount of food coming back to pups and chicks on the island, and so increase mortality.”
The iceberg also contains nutrients that are released into the sea as it melts: “If the berg is stimulating ocean productivity, this could actually boost populations of local predators like seals and penguins,” he said.
There is little fear of a “Titanic II” as boats in the region will be well aware of the iceberg’s location. Once A23a breaks up, though, the smaller bergs will be harder to track, increasing the danger.
But while the berg itself may pose little direct threat, it could be a symptom of what is unwell in the Antarctic.
The ice shelves have lost billions of tons of ice over the last 25 years, which scientists attribute to climate change. Losing all this ice can contribute to a rise in the level of the sea.
“The climate is changing, and it is impacting how ice shelves melt,” Indrani Das, a glaciologist at the Lamont-Doherty Earth Observatory at Columbia University, said in 2023, when the berg was still moving. “Ice shelves are losing mass because the ocean is warming. Calving is a natural process, but that natural calving could be enhanced by climate.”
Still, it was ever thus. Mammoth icebergs “are a completely normal part of the life cycle of the Antarctic and Greenland ice sheets,” Dr. Meijers said.
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