World's largest iceberg breaks free

STORY: At almost 1,500 square miles (4,000 square km), the Antarctic iceberg called A23a is roughly three times the size of New York City.

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 speed, 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.

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. Behemoth A23a could cut off such access.