World’s Largest Iceberg Escapes Antarctica Heading Towards Open Ocean

Roughly three times the size of New York City, the world’s most enormous iceberg is on the move for the first time in more than three decades. Rounded by winds and ocean currents, iceberg A23a is escaping Antarctica’s Weddell Sea and heading into the open Atlantic. The colossal glacier, almost 4,000 square km (1,500 square miles) in area, was born in 1986 when it broke off from West Antarctica’s Filchner-Ronne Ice Shelf. It formerly accommodated a Soviet research station called Druzhnaya 1, but it has remained chiefly immobile since that period.

However, it’s beginning to make its way out of the Weddell Sea and into open waters — and scientists are monitoring it with satellites. “We can see it is picking up speed,” Em Newton, a digital communications officer with the British Antarctic Survey (BAS). “At the moment, it is passing the northern tip of the Antarctic Peninsula and will soon be swept along into the Antarctic Circumpolar Current, which funnels it into a region of the Southern Ocean known as ‘iceberg alley.'”

At the moment, the berg is moving about three miles a day. It’s not yet clear what has caused it to make a break for freedom. It may have gotten “that little bit of extra buoyancy that allowed it to lose its grip on the seafloor and get pushed by ocean currents,” Andrew Fleming, a remote sensing expert at BAS, told the BBC. But he added that the berg could also be heading for a collision with South Georgia Island, a breeding ground for seals and penguins.

Either way, the iceberg is a reminder of how dynamic Antarctica’s polar regions are. Its movement is the latest in a long line of iceberg milestones, including the record-breaking split of A68A in 2017 and A76 in 2021.

While it’s unlikely that A23a will break off into a separate chunk of the ice sheet like those icebergs, it could still cause problems if it drifts far enough north. That’s because the Southern Ocean is a busy shipping zone, and a massive iceberg that could run aground could disrupt commercial operations.

The European Space Agency’s Copernicus Sentinel-1 satellite has been tracking the iceberg’s movement. It shared photos comparing the A23a’s position from Oct. 19 to Nov. 12 in a post on X (formerly Twitter). It will likely remain on a trajectory to reach the South Atlantic, where it can expect to encounter warmer waters and swells. “An iceberg of this scale has the potential to survive for quite a while, even in the much warmer Southern Ocean,” Marsh said. “But as it moves closer to sub-Antarctic South Georgia, it’s going to be a nuisance for ships.” (In this case, the iceberg is expected to run aground on South Georgia on Dec. 10) — but it will probably break up into smaller pieces on the way.