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Saturday, November 14, 2009

Antarctic iceberg on walkabout toward Australia

Trip of iceberg on walkabout from Antarctica towards Australia

by The Press and Journal, Aberdeen, November 13, 2009

A large iceberg was about halfway between Antarctica and Australia, a rare sight in waters so far north, Australian scientists said yesterday.

Australian Antarctic Division researchers working on Macquarie Island, about 930 miles south-east of Tasmania, first saw the iceberg last Thursday about five miles off the north-west coast of the island.

The iceberg, about 160 ft. high and 1,640 ft. long, is probably part of one of several larger icebergs that broke off Antarctica’s Ross Ice Shelf between 2000 and 2002, Australian Antarctic Division glaciologist Neal Young said.

Several icebergs have been drifting slowly northward with the ocean current towards the island over the past year, but it is uncommon for them to move so far into warmer northern waters, he said.

The scientists believe the iceberg will break up and melt rapidly as it continues its journey north. Before it melts, however, it could present a danger to ships navigating the region, Mr Young said.

In 2000, several massive icebergs broke off from Antarctica’s Ross Ice Shelf and the Ronne Ice Shelf.

The first iceberg was about 190 miles long and 23 miles wide. Those icebergs are now drifting away from Antarctica.

Icebergs are formed as the ice shelf develops. Snow falls on the ice sheet and forms more ice, which flows to the edges, on to the floating ice shelves. Eventually, pieces around the edge break off.

A new study of the Greenland ice sheet suggests it is melting at an accelerating rate.

Scientists used two different techniques to measure the ice cap’s loss.

Both indicated that shrinkage of the ice sheet had been speeding up since the 1990s.

The Greenland ice sheet contains enough water to raise global sea level by 7 m.

The new research showed that it lost around 1,500 gigatons of mass between 2000 and 2008, representing a rate of sea level rise of about 0.46 mm per year.

However, between 2006 and 2008 the rate of loss was much higher, producing a 0.75 mm annual sea level rise.

Icebergs flowing to the sea and melting surface ice played an equal role in eroding the ice sheet.

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