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The chance of North Islanders seeing an iceberg off their coastline is considered remote, but an expert says those along the South Island coast have already defied the odds.
Icebergs that have become a huge attraction floating up the Otago coast have now been spotted 60km off Timaru, in South Canterbury, which is unprecedented as far as New Zealand records go.
The massive chunks of ice have been creating a sightseeing bonanza for aircraft operators, but just how far north they will get before melting is unclear.
"If they get north of Christchurch, the [ocean] currents are now acting against them and the water is significantly warmer and will start melting them even further," said Mike Williams, an oceanographer with the National Institute of Water and Atmospheric Research.
"I would say that the chances of them being spotted from the North Island is flat-out zero. But I have made other predictions like that this week which have been proven wrong," Dr Williams said.
"We might get really lucky near Wellington. We might get one car-sized chunk."
In the 1890s icebergs were spotted around the Chatham Islands.
"The problem is going back we are relying on observation from people being in the right place at the right time. Just because we haven't seen them doesn't mean they are not there," Dr Williams said.
At least a dozen icebergs along the South Island coastline are attracting sightseers. One of the latest is a 1km-long berg off Stewart Island, which has the potential to last longer than others because of its size.
Commercial aviation companies in Otago and Southland have been run off their feet over the last two weeks taking tourists to view the spectacular sights.
At least one Christchurch helicopter company is looking to join the sightseeing fray.
Garden City Helicopters pilot Aaron Regan said the company was "certainly keeping an eye on the situation".
To date, the icebergs have been too far offshore to make it economically worthwhile for Christchurch operators to offer tours.
But if the icebergs manage to drift as far north as Banks Peninsula, several companies are believed to be ready to cash in.
Mr Regan said Garden City Helicopters had fielded several inquiries from people keen to make the trip and was taking names and contact numbers.
"We're keeping an eye on where they progress to and how far offshore they are."
In Dunedin, Helicopters Otago is making six trips a day - taking seven passengers on each at $500 a seat - to the icebergs using a twin-engined BK117 helicopter and is fully booked until tomorrow.
"We're flying until the end of Sunday, as long as the weather allows," company director Ros Gale said.
While the company was not taking bookings beyond tomorrow, Ms Gale said, she was making a list of prospective passengers on a "first-in, first-served" basis "until we see what happens later this week".
Ms Gale said the icebergs were changing continuously as they melted and broke apart. "The photographs coming back are absolutely spectacular - just amazing."
