The World’s Largest Iceberg Is Drifting Three Miles Into the Ocean Each Day

The world’s largest iceberg, which had been grounded on the seafloor since the mid-1980s, is moving away from Antarctica and picking up speed, reports BBC News’ Jonathan Amos. Now, scientists say the massive chunk of ice is drifting at a rate of three miles each day, per CNN’s Amy Woodyatt.

The movement appears to be a natural occurrence, and researchers haven’t found a specific inciting event that started the drifting.

“Over time, it’s probably just thinned slightly and got that little bit of extra buoyancy that’s allowed it to lift off the ocean floor and get pushed by ocean currents,” Oliver Marsh, a glaciologist at the British Antarctic Survey, tells Reuters’ Gloria Dickie.

Still, the incident has raised some concerns about wildlife. The drifting iceberg could end up at the island of South Georgia, located a little over 1,000 miles east of the southern tip of South America. There, it could disrupt the foraging of seals, penguins and other seabirds, writes BBC News.

Double-whammy iceberg news this morning:

The largest iceberg, A23a, is on the move!

Here's its journey out of the Weddell Sea after being grounded on the sea floor after calving in August 1986.

Copernicus Sentinel-1 imagery, Google Earth Engine pic.twitter.com/KseKTD1Wrg

— British Antarctic Survey (@BAS_News) November 24, 2023

Called A23a, the iceberg measures around 1,500 square miles—more than 20 times the size of Washington, D.C.—and it’s roughly 1,300 feet thick, making it two and one-third times the height of the Washington Monument. It weighs nearly one trillion metric tons.

Chad Greene, a glaciologist at NASA’s Jet Propulsion Laboratory, tells New Scientist’s James Dinneen that large icebergs like A23a break off from Antarctica around once per decade. Sometimes, they get stuck in the Antarctic’s cold waters, which staves off their melting, but only for a while.

“Icebergs this big can hang around for decades in one place, then one day decide to go for a jolly,” Greene says to the publication. “That’s when things get interesting.”

A23a did just that—it broke off from Antarctica in August 1986, then it became grounded on the floor of the Weddell Sea, which is part of the Southern Ocean between Antarctica and South America.

Andrew Fleming, the remote sensing manager at the British Antarctic Survey, first noticed the iceberg was moving again in 2020, he tells BBC News. Satellite imagery from the British Antarctic Survey showed currents and winds pushed the iceberg thousands of kilometers through the Weddell Sea in 2022 and 2023.

The iceberg has been moving faster in recent months and is now reaching the top of the Antarctic Peninsula. Scientists say it will probably head east, likely ending up on a path—called “iceberg alley”—that carries many icebergs from this region toward the South Atlantic.

Since it’s unusual for such a large iceberg to be on the move, scientists will follow it closely, Marsh tells Reuters.

People are not at risk from A23a, though it may cause issues for wildlife if it runs aground in breeding areas. But melting icebergs can also benefit the ecosystem: They release mineral dust accumulated from Antarctica’s rock bed that serves as a source of nutrients for oceanic organisms.

While A23a’s breakaway from Antarctica in 1986 was likely a natural occurrence, climate change is causing the continent to lose ice, Marsh and Ella Gilbert, a climate modeler at the British Antarctic Survey, say to CNN. The National Snow and Ice Data Center announced in September that Antarctic sea ice reached its lowest annual maximum in recorded history this year.

“Climate change is causing the Antarctic Ice Sheet to lose mass at a significant rate,” Greene tells New Scientist.

In 2021, A23a briefly lost its title of the world’s biggest iceberg, when the larger iceberg A76 broke off from Antarctica. But A23a regained its crown after A76 split into three smaller pieces.

Will Sullivan | | READ MORE

Will Sullivan is a science writer based in Washington, D.C. His work has appeared in Inside Science and NOVA Next.