Another gigantic iceberg breaks off

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Another gigantic iceberg breaks off

By ANDREW DARBY HOBART Wednesday 5 April 2000

The break-up of Antarctica's largest ice shelf has continued with the "calving" of a second gigantic iceberg.

The breakaway of the iceberg, which covers about 2500 square kilometres, means that more than half of the seaward edge of the Ross Ice Shelf has broken away in two weeks - and other icebergs are expected to follow.

The second iceberg has taken with it around 130 kilometres of ice front at the eastern end of the shelf, the United States National Science Foundation said.

It follows the break-off of the 293-kilometre-long iceberg B-15, and the 36-kilometre-long B-16 last week. About 459 kilometres of towering ice cliffs have sheared away since 17March, almost two thirds Ross Ice Shelf's total length of around 750kilometres.

The new iceberg, which is yet to be named, was found by the Antarctic Meteorological Centre at the University of Wisconsin on satellite photographs. It quickly broke into four smaller pieces. As a whole it covered 2480 square kilometres, compared with B-15's 11,000 square kilometres.

The NSF said that the new iceberg appeared to have been loosened by the movement of B-15. Tide movements make it likely that B-15 will repeatedly collide with the Ross Ice Shelf in the coming weeks. One researcher from the University of Chicago, Mr Douglas MacAyeal, likened it to "a bull in a china shop".

Dr Neal Young, of the University of Tasmania's Antarctic Cooperative Research Centre, said that rifts around the new iceberg had been visible for two years, and that it was possible that the motions of B-15 caused its release.

Dr Young said it was most likely that B-15 would drift north-west, taking it across the shipping lanes to Antarctica's largest base, the US McMurdo. Its drift rate might be several kilometres per day.

He said the icebergs' potential to "dam" winter sea ice could cause difficulty during next summer's shipping season. "They could clog up the Ross Sea with heavy ice," he said.

Dr Young said that rifts near the western end of the Ross Ice Shelf front indicated that it too could break away, but that this was believed to be part of the normal pattern of growth and decay of the shelf. Despite the increasing scale of the ice break-off, Dr Young said that the shelf was further advanced into open sea than it was when it was first charted in 1841.

http://www.theage.com.au/news/20000405/A49110-2000Apr4.html

-- Martin Thompson (mthom1927@aol.com), April 04, 2000


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