Ships are on alert and maritime authorities are monitoring the movements of hundreds of menacing icebergs drifting toward New Zealand in the southern Pacific Ocean, officials said.
The area is not a major shipping lane and few sailors are out this month — spring in the southern hemisphere — but ships that traverse the area have little hull protection and could be significantly damaged by a collision with an iceberg, which typically has 90 percent of its mass under water.
“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 of an official navigation warning issued for the area south of the country.
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.
The current flotilla of icebergs that split off Antarctic ice shelves is slowly drifting in the direction of New Zealand. The nearest one, measuring about 100m to 200m long, was 260km southeast of New Zealand’s Stewart Island on Tuesday, Australian glaciologist Neal Young said.
He said it was impossible to tell from the satellite image how tall the iceberg is.
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.
New Zealand oceanographer Mike Williams said the icebergs are drifting at a speed of about 25km a day and he expects most won’t reach New Zealand, similar to the 2006 flotilla, many of which were directed away from the country by ocean currents and wind.
Williams, a scientist with the National Institute of Water and Atmospheric Research, said he was “pretty sure these icebergs came from the break up of the Ross Sea Ice Shelf in 2000” — an ice shelf the size of France and the origin of the 2006 flotilla of icebergs.
Icebergs are routinely sloughed off as part of the natural development of ice shelves. As temperatures have risen in the Antarctic Peninsula area near South America by as much as 5°C in the past 60 years, “whole ice shelves have broken up,” Young said.
But Young said the iceberg flotilla south of New Zealand came from the Ross Sea, a completely different area of Antarctica, and is unrelated to climate change.
The appearance of the bergs in waters south of New Zealand 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 favorable ocean currents conspired to push the towering visitors, which have drifted around Antarctica for the past nine years, into the region’s ocean.
“Icebergs this far north [near New Zealand] are not that unusual,” said New Zealand glaciologist 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,” she said. “Its movement and where it ends up is determined by the weather, wind, ocean currents and the temperature.”
On Monday, Rodney Russ, expedition leader on the tourist ship Spirit of Enderby, spotted an 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.
RSS