The world's largest iceberg seems to have run aground near Antarctica, threatening to block supply ships from scientific bases and starve tens of thousands of penguins.

Experts had predicted that B15A – which measures 3,000 square kilometres, about half the size of Prince Edward Island – would likely slam into a huge glacier floating near McMurdo Sound by last weekend.

They hoped the collision between the two titans would send the iceberg drifting back to sea.

Adelie penguins like these may face starvation if the iceberg doesn't drift away from Antarctic's McMurdo Sound. (AP photo / Australian Antarctic Division)
Adelie penguins like these may face starvation if the iceberg doesn't drift away from Antarctic's McMurdo Sound. (AP photo / Australian Antarctic Division)

But the iceberg's progress toward the Drygalski Ice Tongue has slowed, leading scientists to speculate Thursday that it is hooked in shallow waters about five kilometres offshore.

"This berg has wedged itself between two shallow areas. ...It really hasn't gotten any closer for a week now," said Dean Peterson, science strategy manager at the New Zealand Antarctic Institute.

"It's kind of shimmying back and forth now ... so I don't know whether it's ever going to get to the Drygalski or not."

Ice blocks supply route for research bases

If the massive iceberg turns out to be grounded, it could cause serious problems for scientific bases on the continent, including three research bases at McMurdo Sound run by the United States, New Zealand and Italy.

The monster iceberg – which measures 160 kilometres along one side – has already blocked water currents and winds that break up ice floes during the Antarctic summer, plugging the narrow stretch of sea.

B15A and the ice buildup lie on the routes of ships scheduled to arrive within the month carrying a year's-worth of fuel and food for the stations. The bases aren't in immediate danger, officials said.

They're considering using icebreakers to blast a 130-kilometre path through the floes or unloading the supplies at the ice edge.

In the latter case, fuel would have to be pumped through temporary pipelines and food supplies would have to be dragged to the scientific bases.

The ice blockage also threatens penguin breeding colonies.

Tens of thousands of Adelie penguin chicks face starvation, as their parents are forced to waddle as far as 180 kilometres to reach the open water and food.