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New Zealand's glaciers


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« on: January 26, 2011, 11:57:34 am »


NZ glaciers smallest since records began

By TOM CARDY - The Dominion Post | Monday, 15 September 2008

WARMING SIGN: Marion Glacier in Arawata Valley has recently withdrawn from its proglacial state. Most of New Zealand's glaciers are the smallest they've been since records began. — DR TREVOR CHINN/NIWA.
WARMING SIGN: Marion Glacier in Arawata Valley has recently withdrawn from its proglacial state.
Most of New Zealand's glaciers are the smallest they've been since records began.
 — DR TREVOR CHINN/NIWA.


MOST OF New Zealand's glaciers are now the smallest they have been since records began — and they continue to shrink at a rapid rate.

The National Institute of Water and Atmospheric Research, which made the discovery, said global warming was the main culprit.

Between April last year and March this year, glaciers in the Southern Alps lost about 2.2 billion tonnes of permanent ice — the equivalent in weight to the top section of Mount Taranaki. It is the fourth highest annual loss since monitoring began 32 years ago.

The total ice for the glaciers now comprises an estimated 44.9 cubic kilometres — the lowest on record. The volume of ice dropped by 50 per cent during the last century.

NIWA principal scientist Jim Salinger said glaciers were fed by snow, but because of the La Nina weather system over New Zealand, more easterly winds and warmer than normal temperatures during the period, there was less snow in the Southern Alps and more snowmelt.

Dr Salinger said while the glaciers were sensitive to changes in wind and precipitation as well as temperature, global warming was a big factor in their shrinking.

"It's one of the clearest signs that our climate is warming and that [the shrinkage] is a definite physical response. To have that amount of melting you would have to reduce the precipitation at least by a half or more or warm a degree," he said.

"We know that precipitation has not gone down in the Southern Alps. In the last quarter of a century it's gone up. So to make them retreat you've got to have more melting, which is higher temperatures.

"This is certainly a definite sign of warming in the New Zealand area."

Niwa has surveyed 50 glaciers in the Southern Alps for the past 32 years, recording the height of the snowline at the end of each summer. On average the snowline this year was 130 metres above where it would need to be for the glaciers not to shrink, Dr Salinger said.

It was unlikely the glaciers would disappear entirely, as that would require a temperature rise of 7 degrees celsius and no snow even at the top of our highest mountain, Aoraki Mount Cook.

But they would continue to retreat. Another sign of warming were 12 glacial lakes, including ones at Marion Glacier and Tasman Glacier.

"They are definitely a sign of warming. There is no doubt about it. You get a very rapid loss of snow and ice and that's what's been happening."


http://www.stuff.co.nz/dominionpost/4692547a6479.html



Media Release

Glaciers continue to show significant ice loss

15 September 2008
National Institute of Water & Atmospheric Research (NIWA)

The large Tasman Glacier in Aoraki-Mount Cook National Park. (Photo: Dr Trevor Chinn, Alpine and Polar Research, Hawea)
The large Tasman Glacier in Aoraki-Mount Cook National Park.
(Photo: Dr Trevor Chinn, Alpine and Polar Research, Hawea)


NEW ZEALAND'S GLACIERS are showing the lowest total ice mass on record and most are continuing to shrink at a rapid rate.

Research released by the National Institute of Water & Atmospheric Research (NIWA) shows the Southern Alps glaciers have lost 2.5 km³ (2.2 billion tonnes) of permanent ice from April 2007 to March 2008, the fourth highest annual loss since monitoring started.

The 2008 total ice volume estimate for the Southern Alps glaciers of 44.9 km³ is the lowest on record.

For the past 32 years NIWA has been surveying 50 glaciers in the Southern Alps, using a small fixed wing aircraft, to record the height of the snow line at the end of summer.

NIWA Principal Scientist Dr Jim Salinger says the photographs taken on this year’s survey showed the glaciers had lost much more ice than they had gained during the past glacier year.

“As a result of La Niña conditions over New Zealand, more easterlies, and warmer than normal temperatures, there was less snowfall in the Southern Alps and more snowmelt.

The higher the snow line, the more snow is lost to feed the glacier. On average, the snow line this year was about 130 metres above where it would need to be to keep the ice mass constant,” Dr Salinger says.

Dr Salinger says these results match trends of ice mass lost globally. International monitoring of mountains glaciers by the World Glacier Monitoring Service in Switzerland shows most glaciers are retreating. Of the glaciers where continuous data is available, the mean annual average loss in ice thickness since 1980 is close to half a metre per year.

For more information contact:

Dr Jim Salinger
NIWA, Auckland
Tel: +64 9 375 2053
Mob: +64 27 521 9468


______________________________________

Background Information:

Worldwide, glaciers are regarded as a useful indicator of global warming, but New Zealand’s glaciers are more complicated because they have their source in areas of extremely high precipitation. West of the Main Divide in the Southern Alps, more than 10 metres (10 000 mm) of precipitation falls each year as clouds are pushed up over the sharply rising mountain ranges. This means the mass and volume of New Zealand’s glaciers is sensitive to changing wind and precipitation patterns as well as to temperature. So, for example, the glaciers advanced during most of the 1980s and 1990s when the area experienced about a 15% increase in precipitation, associated with more El Niño events and stronger westerly winds over New Zealand. The glaciers in parts of Norway are similar.

Despite the sensitivity of New Zealand glaciers to changes in both precipitation and temperature, the volume of ice in the Southern Alps dropped by roughly 50% during the last century. New Zealand’s temperature increased by about 1°C over the same period.

Globally, most glaciers are retreating. Of the glaciers for which there are continuous data from the World Glacier Monitoring Service, the mean annual loss in ice thickness since 1980 remains close to half a metre per year. The Service has said that the loss in ice mass “leaves no doubt about the accelerating change in climatic conditions”. For world glacier data, see www.geo.unizh.ch/wgms
.

The level of the glacier snow lines is not necessarily closely related to the amount of snow that falls on the country’s ski fields during winter. Most of the popular ski fields are east of the Main Divide, or in the North Island. Mount Hutt, for instance, gets its snow from big southeasterlies, whereas most of the glaciers are fed by westerlies.[/size]

Change in glacier ice volume since NIWA survey began.

http://www.niwa.co.nz/news/mr/2008/2008-09-15
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