2 huge icebergs let loose off Antarctica's coast

[February 26, 2010]  SYDNEY (AP) -- An iceberg about the size of Luxembourg that struck a glacier off Antarctica and dislodged another massive block of ice could lower the levels of oxygen in the world's oceans, Australian and French scientists said Friday.

The two icebergs are now drifting together about 62 to 93 miles (100 to 150 kilometers) off Antarctica following the collision on Feb. 12 or 13, said Australian Antarctic Division glaciologist Neal Young.

"It gave it a pretty big nudge," Young said of the 60-mile (97-kilometer)-long iceberg that collided with the giant floating Mertz Glacier and shaved off a new iceberg. "They are now floating right next to each other."

The new iceberg is 48 miles (78 kilometers) long and about 24 miles (39 kilometers) wide and holds roughly the equivalent of a fifth of the world's annual total water usage, Young told The Associated Press.

Experts are concerned about the effect of the massive displacement of ice on the ice-free water next to the glacier, which is important for ocean currents.

This area of water had been kept clear because of the glacier, said Steve Rintoul, a leading climate expert. With part of the glacier gone, the area could fill with sea ice, which would disrupt the ability for the dense and cold water to sink.

This sinking water is what spills into ocean basins and feeds the global ocean currents with oxygen, Rintoul explained.

As there are only a few areas in the world where this occurs, a slowing of the process would mean less oxygen supplied into the deep currents that feed the oceans.

"There may be regions of the world's oceans that lose oxygen, and then of course most of the life there will die," said Mario Hoppema, chemical oceanographer at the Alfred Wegener Institute for Polar and Marine Research in Germany.

The icebergs, weighing 860 billion tons and 700 billion tons respectively, are located in water over the Antarctic Continental Shelf, Young said.

"We expect them to head west along the Antarctic coastline," he said.

Young said it was not likely they would reach as far north as Australia, and noted icebergs are very slow movers.

Oxygen levels being fed into the world's ocean currents are now changing "and the overturning circulation currents will respond to that change," Rintoul said. Observing what happens "will ... allow us to improve predictions of future climate change," he added.

[Associated Press; By OWEN PYE]

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