The world’s largest iceberg, A23a, is finally on the move again after months of being stuck in swirling ocean currents. The massive iceberg had been trapped in a rotating water current near the South Orkney Islands but managed to break free on Dec. 13, according to the British Antarctic Survey (BAS).
This isn’t A23a’s first escape. The iceberg originally calved — or broke off — from Antarctica’s Filchner Ice Shelf in 1986. After breaking free, it became lodged on the seafloor for 37 years before escaping in 2023.
However, it didn’t travel far before becoming trapped again in what scientists call a Taylor column — a rotating water current caused by ocean flows swirling around an underwater mountain, known as a seamount.
At its fastest, A23a was spinning about 15 degrees counterclockwise each day, BAS researchers reported. Now, with its latest breakaway, scientists are eager to see where the iceberg’s journey will lead.
A massive ‘Megaberg’
A23a is known as a “megaberg” because of its immense size. It covers an area about three times larger than New York City and weighs nearly 1 trillion tons. Despite being adrift for decades, it has remained relatively intact due to the cold waters around Antarctica, which slow its melting.
Since May 2023, A23a has held the record as the largest iceberg on Earth after the previous record-holder, A-76A, broke apart. “It’s exciting to see A23a on the move again after periods of being stuck,” said Andrew Meijers, an oceanographer with BAS.
“We are interested to see if it will take the same route the other large icebergs that have calved off Antarctica have taken. And more importantly what impact this will have on the local ecosystem.”
The iceberg graveyard: Drake Passage
Most massive icebergs that break away from Antarctica drift north through the Drake Passage, a stretch of the Southern Ocean known as the “iceberg graveyard.” This region propels icebergs into warmer waters, where they eventually melt and break apart. This fate befell iceberg A-76A in 2023 and A68a in 2020, when strong ocean currents tore it in half.
Scientists are closely monitoring A23a’s path through this region. They believe giant icebergs like A23a play a key role in ocean health by providing essential nutrients. As icebergs melt, they release minerals into the water, encouraging the growth of tiny plants and animals that form the base of the ocean food chain.
“We know that these giant icebergs can provide nutrients to the waters they pass through, creating thriving ecosystems in otherwise less productive areas,” said Laura Taylor, a doctoral researcher in biogeochemistry with BAS.
“What we don’t know is what difference particular icebergs, their scale, and their origins can make to that process.”
To answer these questions, scientists have collected water samples along A23a’s predicted path. They plan to take more samples after the iceberg passes. By comparing these samples, researchers hope to learn how icebergs impact ocean ecosystems and whether larger icebergs make a bigger difference than smaller ones.