Melting Glaciers & Floating Icebergs

New Zealand’s glaciers are melting away. Scientists are seeing about a 50% decrease in the ice volume of the Southern Alps. While 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 south Pacific Ocean.

By Lachlan Forsyth for 3 News New Zealand (23 November 2009):

On the eve of the Copenhagen climate summit, New Zealanders have been presented with dramatic evidence that we are not immune to climate change.

The country’s glaciers are melting away. According to a National Institute of Water and Atmospheric Research (Niwa) report they have lost half of their snow and ice in the last century.

Scientists are warning the big glacier melt will continue.

It has long been known that the Tasman Glacier – the country’s longest – is shrinking. But the latest information from Niwa shows virtually every other glacier in the country is doing likewise.

“We’ve seen about a 50 percent decrease in the ice volume of the Southern Alps,” says Jordy Hendrikx, snow and ice scientist. “So if you were considering a health status, they’ve lost half of their health already.”

Niwa says glacier length is misleading because total volume can be decreasing even while length is increasing. Their concerns surround the glaciers’ mass balance – the snowfall required to replace the snow melt, and thereby maintain a glacier’s size.

Since 1997, less snow has been falling and more ice has been melting. And since 2000, the southern glaciers have been below their tipping point – meaning that, apart from a small spike earlier this decade, the mass balance has declined sharply.

“That’s a very slight warming over that time, and we’re looking in the future that we’re going to see continued warming and therefore continued ice loss,” says Mr Hendrikx.

Worldwide it’s not much better, the number of glaciers retreating now far outnumber those advancing – a huge turnaround since the late 1970s when advancing glaciers were the norm.

“The ends of our glaciers are just snapping off like chocolate and melting very rapidly, so we are losing a lot of ice mass very quickly,” says climate scientist Jim Salinger.

Prime Minister John Key says he takes the demise of our glaciers seriously, just not seriously enough to attend Copenhagen himself.

“No, it doesn’t prompt me to go to Copenhagen but it does show we need to take climate change seriously,” he says.

Despite this, sceptics will claim there is still no evidence that climate change is caused by human activity.

“The physics of climate change are bloody obvious, which is if you put more greenhouse gases in the planet, it will warm,” says Mr Salinger.

“Over the long period of time there’s a clear trend that we’re seeing a reduction in ice,” says Mr Hendrikx. “It’s undeniable that we have altered the atmosphere.”

Man-made threat or not, there is no denying our famed glaciers may soon be in short supply.

Source: www.3news.co.nz

Wednesday November 25, 2009

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 south Pacific Ocean, officials say.

The nearest one, measuring about 30 yards (metres) tall, was 160 miles (260 kilometres) southeast of New Zealand’s Stewart Island, Australian glaciologist Neal Young said. He couldn’t say how many icebergs in total were drifting 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 per cent of its mass under water.

Very few adventure sailors would be in the waters in November, when it is still the southern hemisphere’s spring.

Maritime New Zealand safety services general manager Nigel Clifford said as the icebergs drift closer ‘the more the potential risks grow of them posing a hazard to shipping’ as they break up and float lower in – or just under – the ocean surface.

The agency was ‘keeping a close eye on the increasing risk … it’s tracking iceberg positions and has begun initial planning for any incident,’ he told The AP.

He noted the area is not a major shipping lane, with commercial fishing vessels and a limited number of passenger cruise ships passing through and reporting positions for the drifting ice.

New Zealand oceanographer Mike Williams said the icebergs are drifting at a speed of about 25 kilometres (16 miles) a day and he expects most won’t reach New Zealand, as happened during the last major flotilla in 2006 when ‘a lot of them went out east (carried by ocean currents and wind) away from New Zealand.’

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 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 5 degrees Fahrenheit (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 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 500-foot-long (150-metre-long) iceberg about 60 miles (100 kilometres) northeast of Macquarie Island and heading north – about 500 miles (800 kilometres) 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 600 miles by 440 miles (1,000 kilometres by 700 kilometres), 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.

Source: www.skynews.com.au