Icebergs may threaten shipping

A flotilla of hundreds of icebergs that split off Antarctic ice shelves is drifting toward New Zealand and could pose a risk to ships in the southern Pacific Ocean, officials said.

Australian glaciologist Neal Young said he couldn't say how many icebergs in total were roaming the Pacific, but he counted 130 in one satellite image alone and 100 in another.

Large numbers of icebergs last floated close to New Zealand in 2006, when some were visible from the coastline - the first such sighting since 1931.

Maritime officials have issued navigation warnings for the area south of the country.

"It's an alert to shipping to be aware these potential hazards are around and to be on the lookout for them," Maritime New Zealand spokeswoman Sophie Hazelhurst said.

No major shipping lanes or substantial fishing grounds are in the area, but most ships there have little hull protection if they collide with an iceberg - which typically has 90 percent of its mass underwater. Very few adventure sailors would be in the waters in November.

Icebergs are routinely sloughed off as part of the natural development of ice shelves, but Young said the rate appeared to be increasing as a result of regional warming in Antarctica.

"Whole ice shelves have broken up," he said, as temperatures have risen in Antarctica, where they are up as much as 3 degrees Celsius in the past 60 years.

But he cautioned against linking the appearance of the bergs in New Zealand waters to global warming: The phenomenon depends as much on weather patterns and ocean currents as on the rate at which icebergs are calving off Antarctic ice shelves.

In the current case, a cold snap around southern New Zealand and favourable ocean currents conspired to push the towering visitors, which have drifted around Antarctica for the past nine years, to the region intact.

"Icebergs this far north (near New Zealand) are not that unusual," said New Zealand glaciologist Dr Wendy Lawson, noting that an iceberg's reach was determined by its size.

"If an iceberg starts off large, it will last longer in the sea. Its movement and where it ends up is determined by the weather, wind, ocean currents and the temperature," Lawson, head of the department of geography at Canterbury University, told The Associated Press.

On Monday, Rodney Russ, expedition leader on the tourist ship Spirit of Enderby, spotted a 150m-long iceberg about 100km northeast of Macquarie Island and heading north - about 800km south of New Zealand. Australian scientists reported another mass of 20 icebergs drifting north past Macquarie Island two weeks ago.

Young said satellite images showed the group of icebergs, spread over a sea area of 1000km by 700km, moving on ocean currents 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 of the floating ice shelves. Eventually, pieces around the edge break off.

- AP