February 26, 2010

Enormous Icebergs Could Affect Ocean Currents

A mammoth iceberg that struck a glacier off Antarctica, dislodged a newer chunk of ice that could affect ocean currents and also lower the levels of oxygen in the world's oceans, according to Australian and French scientists.

The two icebergs are drifting together about 62 to 93 miles off Antarctica after the Feb 12-13 collision, said Neal Young, a glaciologist for the Australian Antarctic Division.

The first iceberg, measuring 60 miles long, collided with the Mertz Glacier Tongue and shaved off a new, smaller chunk. "It gave a pretty big nudge," Young told The Associated Press. The two large icebergs are floating right beside each other, he added.

The second iceberg measured 48 miles long and nearly 24 miles wide. Young estimated that it holds roughly the equivalent of 20 percent of the world's yearly total water usage.

Experts are concerned that the massive displacement of ice will have a huge impact on the world's ocean currents. The open, ice-free water in the area is an important factor in the circulating the currents, but now with the two huge ice blocks and the hundreds of smaller chunks floating around the glacier, it could disrupt that important cycle.

Climate expert Steve Rintoul said now that part of the glacier is gone, the area could fill up with sea ice, which would hinder the ability for dense, colder water to sink. The sinking water is what flows into ocean basins and feeds the global ocean currents with oxygen, he explained.

There are only a few places like this one on Earth. If the waters here are affected "there may be regions of the world's oceans that lose oxygen, and then of course most of the life there will die," Mario Hoppema, chemical oceanographer at the Alfred Wegener Institute for Polar and Marine Research in Germany, told AP.

The icebergs, weighing a combined total of 1560 billion tons, are located northeast of the Antarctic Continental Shelf, due south of Melbourne, Australia. "We expect them to head west along the Antarctic coastline," said Young.

The icebergs are very slow movers, and it is unlikely they will reach as far north as Australia. If the icebergs run aground or drift northward into warmer waters, they will not have an impact on the ocean currents. However, it is possible they could remain where they are, and that would be bad for the ocean currents.

The lifespan of the icebergs depends on their course. If they head into warmer seas, they could melt in a few decades. If they remain anywhere near the Antarctic landmass, they could persist far longer.


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