A massive iceberg -- bigger than all of Prince Edward Island -- has broken away from an ice shelf in the Antarctic, British scientists have announced.

The 1-trillion tonne ice chunk is one of the largest icebergs ever to “calve” off the Antarctic ice shield, and has a volume twice that of Lake Erie.

Scientists from Swansea and Aberystwyth universities in Wales have been monitoring the Larsen C ice shelf on the Antarctic Peninsula, where a large crack had grown over the last year.

They announced Wednesday on their Project MIDAS blog that it appears the iceberg calved sometime between July 10 and 12. The final breakthrough was detected in images from NASA’s satellite instruments, they said.

“The calving of this iceberg leaves the Larsen C Ice Shelf reduced in area by more than 12 per cent, and the landscape of the Antarctic Peninsula changed forever,” they wrote.

The researchers say that because it was already floating before it calved away, the iceberg will have no immediate impact on sea level, much the way the melting of an ice cube doesn’t affect the volume of a drink.

But the group says the calving could now destabilize the entire ice shelf. In fact, it may follow the example of its smaller neighbour Larsen B, which completely disintegrated in 2002 following a similar calving.

The concern is that because ice shelves buttress the grounded ice behind them, when they collapse, the ice behind them accelerates toward the ocean, where it can add to sea level rise.

Prof. Adrian Luckman, the lead investigator of the MIDAS project, wrote on the blog that in the next few months and years, the ice shelf could either gradually regrow, “or may suffer further calving events which may eventually lead to collapse.”

He says the scientific community is divided on its predictions about what might happen.

“Our models say it will be less stable, but any future collapse remains years or decades away,” he wrote.

Larsen C is the fourth largest ice shelf in Antarctica and is slightly bigger than Nova Scotia.

As for the iceberg itself, Luckman says that it might remain in one piece, “but is more likely to break into fragments.”

Some of the ice may remain in the area for decades, while parts of the iceberg may drift north into warmer waters.

Shawn Marshall, a glaciologist at the University of Calgary who is not involved in the Midas project, told CTV’s Your Morning that, for the moment, the iceberg won’t be going anywhere fast.

“Right now, it’s winter down there, so it’s kind of locked into the sea ice in the Weddell Sea, so it will not move too much over the next few months,” he said. But it will probably head out to the open water come the austral summer, he said.

The iceberg will be like a big, flat island that will float around for many years, he said, and might host colonies of penguins or even be used as a platform for research.

“It’s hundreds of metres thick so it will stick out above the ocean surface by 20 or 30 metres. It will be easily visible from any of the cruise ships down there,” he said.