Melting glaciers provide clue to tracking climate change

Such measurements are the benchmark and several decades of data is regarded as the best way to build up an accurate picture of what's happening to a glacier.

Glaciers originate on land and represent a sizeable accumulation of snow and ice over the years. They tend to carve their way through valleys as more and more ice accumulates until the point where more is lost through melting than is gained.

That Shrinking Feeling

“We probably know less about the total volume of glaciers than we do about how much ice there is in the big ice sheets in Greenland and Antarctic because a lot of it is in small mass areas and a lot of it is inaccessible,” said Allison, leader of the Australian Antarctic Division's ice, ocean, atmosphere and climate program.

The World Glacier Monitoring Service in Switzerland analyses mass balance data for just over 90 glaciers and says their average mass balance continues to decrease.

Since 1980, cumulative thickness loss of the reference glacier group is about 12 meters of water equivalent, it says in its latest 2007/08 report.

Estimates vary but glaciers and mountain caps could contribute about 70 centimeters (2.3 feet) to global sea levels, a 2009 report authored by Allison and other leading scientists says.

The “Copenhagen Diagnosis” report from the Climate Change Research Centre at the University of New South Wales says there is widespread evidence of more rapid melting of glaciers and ice-caps since the mid-1990s.

That means run-off from melting glaciers and ice-caps is raising sea levels by 1.2 millimeters a year, translating to up to 55 centimeters (1.8 feet) by 2100 if global warming accelerates.

In Nepal, the International Centre for Integrated Mountain Development says “mass-balance” measurements would provide direct and immediate evidence of glacier volume increase or decrease.

It said that based on studies, the majority of glaciers in the region are in a general condition of retreat.

Glaciers have almost vanished from New Guinea Island and in Africa and many on Greenland, the Antarctic Peninsula and West Antarctica are also melting quickly, dumping large amounts of ice into the sea.

Part of the problem is that glaciers are fickle things to measure, said Allison, and requires legwork and lots of bamboo stakes. These are placed in holes top to bottom, a potentially dangerous job, although satellites and lasers fitted to aircraft are changing this.

After a year or so, stakes placed up high will have had snow build up on them, so you can estimate how much snow fell there.

Those down low will have lost mass due to melt and evaporation, so there would be more of the canes sticking out.

For the millions that live downstream, it is the impacts that are of most concern and among them is the threat of sudden bursting of lakes created as glaciers retreat.

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