World's largest iceberg breaks free, heads toward Southern Ocean

The world’s largest iceberg is on the move for the first time in more than three decades, scientists said on Friday. At almost 4,000 square kilometres, the Antarctic iceberg, A23a, is roughly three times the size of New York City.

Since calving off West Antarctica’s Filchner-Ronne Ice Shelf in 1986, the iceberg, which once hosted a Soviet research station, has largely been stranded after its base became stuck on the floor of the Weddell Sea.

Not anymore. Recent satellite images reveal that the berg, weighing nearly a trillion tonnes, is now drifting quickly past the northern tip of the Antarctic peninsula, aided by strong winds and currents. “It’s rare to see an iceberg of this size on the move,” said British Antarctic Survey glaciologist Oliver Marsh, so scientists will be watching its trajectory closely.

As it gains steam, the colossal berg will likely be launched into the Antarctic circumpolar current. This will funnel it toward the Southern Ocean on a path known as “iceberg alley”, where others of its kind can be found bobbing in dark waters.

Why the berg is making a run for it now remains to be seen. “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,” said Marsh.

A23a is also among the world’s oldest icebergs.

It’s possible A23a could again become grounded at South Georgia island. That would pose a problem for Antarctica’s wildlife. Millions of seals, penguins, and seabirds breed on the island and forage in the surrounding waters.