Trillion-ton iceberg sparks debate over climate change factor

MELBOURNE, Australia - One of the biggest icebergs ever recorded, a trillion-ton behemoth more than five times the size of Hong Kong, has broken off Antarctica, triggering disagreement among scientists over whether global warming is to blame.

The event, captured by satellite, happened sometime in the past few days when the giant chunk snapped off an ice shelf.

While such "calving" of icebergs is not unusual, this is an especially big one, covering roughly 6,000 square kilometers.

Its volume is twice that of Lake Erie, the fourth-largest of the five Great Lakes in North America, and the 13th-largest globally if measured in terms of surface area.

The iceberg, known as A68, broke loose from the Larsen C ice shelf, which scientists had been monitoring for months as they watched a crack grow more than 200 km long.

Scientists say global warming has caused a thinning of such shelves, but they differ on whether the latest event can be blamed on climate change.

The iceberg is considered unlikely to pose any threat to shipping. And since the ice was already floating, the breakup won't raise sea levels in the short term, the project said in a statement.

But it removed more than 10 percent of the ice shelf, and if that eventually hastens the flow of glaciers behind it into the water, there could be a "very modest" rise in sea level, the project said.

Watching closely

Two other Antarctic ice shelves, farther north on the Antarctic Peninsula, collapsed in 1995 and 2002. That sped up the slide of glaciers, which contributed to sea-level rise, David Vaughan, director of science at the British Antarctic Survey, said in a statement.

"Our glaciologists will now be watching closely to see whether the remaining Larsen C ice shelf becomes less stable than before the iceberg broke free," he said.

Swansea University glaciologist Martin O'Leary, a member of the MIDAS project, called it "a natural event, and we're not aware of any link to human-induced climate change."

However, Ian Simmonds, a professor at the School of Earth Sciences at the University of Melbourne, said man-made global warming had accelerated the process.

"The calving of this huge iceberg from the Larsen C ice shelf is deeply troubling. This follows the collapse of part of the Larsen B ice shelf in February 2002," Simmonds said.

"The causes of these breakups are similar. Temperatures have risen dramatically in the region over recent decades. This has meant that summer temperatures now frequently get above freezing, and the associated surface melting significantly weakens the ice shelves."

A spokeswoman for the British Antarctic survey said there's not enough information to say whether the calving is an effect of climate change, though there's good evidence global warming has caused thinning of the ice shelf.

As for any danger to navigation, scientists said the iceberg will probably break up and its pieces will circle Antarctica for years or decades rather than drifting northward into shipping lanes.

Xinhua - Ap