December 1, 2009

Strong Winds Divert Icebergs Away From New Zealand

Powerful westerly winds in the south Pacific have steered a flotilla of icebergs initially headed toward New Zealand to the east, away from the nation, according to an oceanographer at New Zealand's National Institute of Water and Atmospheric Research.

A shipping alert was distributed last week while maritime authorities monitored the icebergs as they drifted from Antarctica toward New Zealand's South Island.

"It looks like they've all disappeared east of New Zealand," oceanographer Mike Williams of New Zealand's National Institute of Water and Atmospheric Research told the Associated Press on Tuesday.

It is not likely they would be seen anywhere near the coastline, he added.

A week ago, the closest iceberg, which was 330 to 660 feet long, was located about 160 miles southeast of New Zealand's Stewart Island.

But satellite imaging reveals no sign of any icebergs northeast of Auckland Islands, 250 miles south of New Zealand, said Australian glaciologist Neal Young.

"If ice is there, it's below 500 feet in length," the smallest size satellite imaging can detect, Young told the Associated Press.

Since many of the bergs would have been made small by now from melting and erosion, they were not likely to have been seen on satellite images.

The last time large numbers of icebergs drifted close to New Zealand was in 2006.  Some of those bergs were visible from the coastline -- the first such sighting since 1931.

Scientists believe the current group of icebergs likely split off Antarctica in 2000, when parts of two large ice shelves - the Ross Sea Ice Shelf and Ronne Ice Shelf "“ cracked.  The Ross Sea Ice Shelf, roughly the size of France, is also thought to be the source of the 2006 icebergs.  Icebergs are commonly shed as part of the natural development of ice shelves. 

The icebergs in waters south of New Zealand depend as much upon weather patterns and ocean currents as upon the pace at which the bergs are sloughed off the Antarctic ice shelves.

Rodney Russ, who leads the Spirit of Enderby eco-tourism vessel east of New Zealand, said his expedition had previously seen two large icebergs north of Macquarie Island.

"Traffic in this part of the world is pretty light at all times of the year. We're probably one of the only vessels that ply this area regularly," he said during an interview with the Associated Press.

Russ' vessel includes a fully ice-strengthened hull, and employs as many as three sailors on permanent watch in iceberg-affected seas.  It also uses continuous radar scanning and strong searchlights during the short six-hour nights, Russ said.

"It would be a foolhardy captain who would come down here and not step up the (iceberg) watch and increase the lookouts."

Image Courtesy Susan Ferguson, Australian Antarctic Division


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