The world’s largest iceberg spins in the same place

The largest iceberg in the world, named A23a, has been spinning in circles in the same place in the ocean for months. And that is special, because usually such an iceberg would move away and melt quickly due to the powerful currents of the ocean.

It concerns a very large iceberg just north of Antarctica, says oceanographer Erik van Sebille from Utrecht University in Looking forward to tomorrow. “It is almost twice the size of the North Holland area and 400 meters thick.” The iceberg would barely fit in the Channel between the United Kingdom and France.

The ice has broken out of a glacier at the South Pole. “We then thought with all oceanographers: now the iceberg is free,” says Van Sebille. “Now it gets into the open ocean, the then it will run through and start to melt very quickly.”

Because the iceberg ended up in the ‘Antarctic circumpolar current’, the strongest ocean current on Earth. That would allow the mountain to move north, where it is warmer.

But against all expectations, this did not happen, which also meant that the expected meltdown did not happen. The A23a stayed in the same area and started turning in circles. “The iceberg does a kind of pirouette in a little less than a month. Around an undersea mountain.”

“The strange and fun thing is that the mountain under the sea is only a few hundred meters high,” says Van Sebille. So there are still miles of water between the top of the mountain and the surface of the ocean. “So that an iceberg feels like that mountain under the sea. It’s kind of a princess and a pea.”

“That pile on the sea floor ensures that the iceberg remains locked,” said the scientist. This phenomenon is called a Taylor column. “If you have an obstacle on the sea floor, in some cases the current can’t get over it. The current has to go around it,” Van Sebille said. This causes the flow to split and a rotating mass of water is created.

“The water above the mountain is all locked up,” says Van Sebille. “That can’t go away anymore, it stays there. The iceberg got in there and now it won’t get out.”

And that could take some time. The oceanographer believes the iceberg could remain there for years, “perhaps decades.”