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New Zealand's glaciers


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Author Topic: New Zealand's glaciers  (Read 2177 times)
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« on: January 26, 2011, 12:00:43 pm »


Tasman Glacier about to calve

By JEFF TOLLAN - The Timaru Herald | 5:00AM - Tuesday, 03 August 2010

READY TO ROLL: The terminal face of the Tasman Glacier has risen 20 metres out of water and is now 50 metres high. Its original depth can be seen by the notches cut by the lake. — Photo: GLACIER EXPLORERS.
READY TO ROLL: The terminal face of the Tasman Glacier
has risen 20 metres out of water and is now 50 metres high.
Its original depth can be seen by the notches cut by the lake.
 — Photo: GLACIER EXPLORERS.


A 20-METRE RISE in the height of the Tasman Glacier's terminal face is "a prelude" to an iceberg calving — a year after the largest recorded calving.

Aoraki/Mount Cook Alpine Village tourism general manager Denis Callesen said the latest change of the glacier's appearance was amazing. It followed a 250 millimetre downpour in the weekend.

"We've never ever seen the face rise up like that. The whole process that's going on at the moment is incredible."

"In the coming weeks it's inevitable there's going to be a massive calving."

In February 2009, a giant slab of ice, estimated to be 250m long by 250m wide and 80m high, plunged into the lake. It sent a three-metre surge of water down the terminal lake. A second iceberg about a quarter of the size calved from the face shortly afterwards.

The glacier is the country's largest, at just under 30km long, 600m deep in the middle and 1.6km wide. At its deepest point it sits below the bottom level of Lake Pukaki.

Its face is now 600m across by 100m deep by 50m high.

While it is a popular tourist attraction, Mr Callesen said boats touring the glacier would not be allowed to go within 1.5 kilometres of the terminal face. Up until now they had been able to travel to within 800 metres of it.

In spite of the risk of a 3 or 4 metre swell, he said it would not be a big issue if boats were on the lake, as the crews were trained.

"It's not a breaking wave and the boats are relatively safe."

"As it comes through the first thing that happens is the jetty grounds out on the bottom of the lake and then bounces up."

Speaking to the Herald last night, glaciologist Trevor Chinn said the rise in the face was likely to be caused by extra water getting in between the ice and the bedrock. "Ice is one-tenth lighter than water. The ice is so deep, with a bit more water in the lake, the central ice is held down by the sides and if the ice on the bottom gets water under it then it floats."

Mr Chinn said it was likely the part that rose out of the water could have broken from the glacier already.

"It's dreadfully unstable because it's probably leaning back against the glacier."

"When it's floating, there's nine times more underneath."

Mr Chinn said the climate was no longer playing a part in the Tasman's retreat and large chunks would continue to calve off until it reached equilibrium, to which it was about "half way there". "It's going to go on for another decade really. It's far too big for this climate, it's quite dramatic, this change. It's a tipping point."

"You can't reverse this. If the climate got colder, no, you wouldn't get your glacier back for years and years. Huge bits coming off is to be expected."


http://www.stuff.co.nz/timaru-herald/news/3983628/Tasman-Glacier-about-to-calve



Tasman Glacier calving awaited

The Timaru Herald | 5:00AM - Saturday, 14 August 2010

ALL EYES are still on the rising face of the Tasman Glacier, waiting for the birth of an iceberg.

Aoraki-Mount Cook Alpine Village Ltd tourism general manager Denis Callesen said the only movement on the glacier front had been vertical, as the face of the 20-kilometre-long ice flow continued to rise out of the terminal lake.

Mr Callesen said plans to install a camera to watch over the glacier had been hampered by power supply problems and the weather.

"Our problem at present is access, as the Tasman Valley Road beyond Blue Lakes has a very high avalanche danger."

At the beginning of the month a 250mm deluge of rain caused the face of the glacier to rise 20 metres out of the water — a prelude to the face snapping off, a process known as calving. The broken ice would then be an iceberg.

In February 2009, a giant slab of ice, estimated to be 250 metres long by 250 metres wide and 80 metres high, fell into the lake. It sent a three-metre surge of water down the terminal lake. A second iceberg about a quarter of the size calved from the face shortly after.

The glacier is the country's largest, at just under 30km long, 600 metres deep in the middle and 1.6km wide.


http://www.stuff.co.nz/timaru-herald/news/4024293/Tasman-Glacier-calving-awaited



Glacier wait ‘a bit like Jaws’

The Timaru Herald | 5:00AM - Tuesday, 17 August 2010

WAITING FOR THE BIG ONER: Glacier Explorers' manager Bede Ward looks over the rising face of the Tasman Glacier after the closest glimpse in days at what is happening at the terminal face. Part of it is expected to shear off and become an iceberg. — Photo: GLACIER EXPLORERS.
WAITING FOR THE BIG ONER: Glacier Explorers'
manager Bede Ward looks over the rising face of
the Tasman Glacier after the closest glimpse in
days at what is happening at the terminal face.
Part of it is expected to shear off and become
an iceberg. — Photo: GLACIER EXPLORERS.


AFTER RAIN and avalanche threats, conditions have cleared to allow a closer look at the rising, cracked face of the Tasman Glacier.

A team from Glacier Explorers, which gives tours of the terminal lake, yesterday got within 690 metres of the ice floe that recently gained international attention following reports the face will soon break off into an iceberg.

Heavy rain in the Aoraki/Mount Cook National Park has seeped underneath the base of the glacier, pushing the terminal face up by 30 metres since August 02. As a result, millions of tonnes of ice are expected to snap from the rest of the glacier, and become one or more large icebergs.

A chunk of ice, about 250 metres long, 250 metres wide and 80 metres high, fell into the terminal lake in February last year, generating a 3 metre surge of water.

Denis Callesen, tourism general manager of Aoraki/Mount Cook Alpine Village, said a lowering of the avalanche risk allowed several staff members to get alongside the glacier, though from the safety of the moraine wall above it.

"The scope is enormous. There were cracks in the glacier before, but they've certainly gotten bigger, possibly as wide as one or two metres."

While the wall of ice keeps climbing out of the water, Mr Callesen said there was still no idea when it would calve off into an iceberg. "The fellow upstairs will decide that. It's a new phenomenon, there's no telling what will happen."

He said it was the magnitude that made this event unique — a much smaller rise happened following torrential rain in 1994 — and so far the event was "running as predicted".

Glacier Explorers' manager Bede Ward said it was "a bit like the movie Jaws; it's what is below the water — and you can't see — that you worry about".


http://www.stuff.co.nz/timaru-herald/news/4030214/Glacier-wait-a-bit-like-Jaws
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