World's largest iceberg is on the move again

The threat of sea access being blocked to United States and New Zealand bases in Antarctica may have receded after the world's largest iceberg broke free from the McMurdo Sound sea bed last month, New Zealand Antarctic officials said.

Iceberg B-15A - equivalent in size to Luxembourg - has started moving again into deeper water after becoming stuck in relatively shallow seas in January.

The previous position of the iceberg had caused a build up of sea ice in McMurdo Sound, threatening access by US ice-breaking ships to New Zealand's Scott Base and the nearby US McMurdo Sound base.

Antarctica New Zealand Chief Executive Lou Sanson said staff were watching the situation with interest but, after past experiences, were making no predictions about the massive iceberg's likely course.

"We know very little about what makes this thing tick. Every time someone has made a prediction about it, they've been proved wrong," Sanson said.

He added the renewed drift of the iceberg had loosened the build up of sea ice in McMurdo Sound, hopefully allowing access to the bases by ice-breakers in the next summer season, starting late this year.

Before the grounding, the iceberg had been on a course for what scientists called "the collision of the century" with a huge floating glacier, the 70km-long and 20km-wide Drygalski Ice Tongue, which juts into McMurdo Sound.

The iceberg, 120km-long, with an area exceeding 2 500km�, is so large that scientists have been worried about its effects on sea life and penguin colonies in the region.

"This thing is so big it creates its own weather. It's the largest moving thing on Earth," Sanson said.

The European Space Agency (ESA), which monitors the iceberg by satellite, said last month that after the iceberg floated free of the seabed, it drifted to within only a few kilometres of the Drygalski Ice Tongue.

Mark Drinkwater of ESA's ice/oceans unit said the likelihood of a collision depended on tides and currents and whether the shallowness of the seabed prevented the iceberg swinging around far enough to hit the ice tongue.

B-15A is the largest remaining section of the even larger B-15 iceberg, which broke off from the Ross Ice Shelf in March 2000. The B-15 iceberg had an area equivalent to Jamaica.