Saturday, January 22, 2011

Glacier shrinkage will hit European Alps hardest, study claims

A fifth of the ice in the world’s mountain glaciers and ice caps will disappear by 2100, with some regions losing as much as 75 per cent of their ice, according to an international study.

In the most detailed assessment yet of glaciers, which are often described as the world’s water towers, the study found the European Alps, as well as New Zealand, could lose three quarters of their ice by the end of the century, while high mountainous regions in Asia may lose 10 per cent. In Western Canada and the United States, 50 per cent of glacier ice could disappear by 2100, which could have substantial impacts on regional power dams and water supplies.

“For the long-term, it’s not good for the economy because there will be a drop in river run-off and less water in reservoirs,” says glaciologist Valentina Radic a professor at the University of British Columbia and the lead researcher. Radic’s study is not detailed enough to project
regional affects, but she says other research underway should give a feel for the impact on Canadian water supplies, reservoirs and hydro dams.

The study, published in the journal Nature: Geoscience, concludes that, globally, mountain glaciers and ice caps are projected to lose 15-27% of their volume by 2100, although the extent of the damage varies widely. The analysis suggests glaciers in the Alps (left: Mt. Everest) and New Zealand will shrink by more than 70% but shrinkage is predicted to reach about 10% in Greenland and high-mountain Asia.

The researchers argue this will result in "substantial impacts" on regional water availability, as well as a rise in sea levels. Retreating glaciers and ice caps threaten the water supplies of cities such as Kathmandu in Nepal and La Paz in Bolivia (right), which depend substantially on glacial melt water for drinking and farming.

Scientists from the University of British Columbia in Vancouver, Canada, who conducted the research, predict that melting glaciers and ice caps will be responsible for increases in sea levels of 8.7-16.1cm by 2100. This broadly confirms the range projected by the UN's climate change body, the Intergovernmental Panel for Climate Change (IPCC).
"What is surprising here is the contribution to sea level rises of up to 16cm just from the melting of small glaciers and ice caps. This may still be a low estimate as we did not include ice loss from calving – when a piece of ice breaks off into the sea," said Dr Valentina Radic, who co-authored the study with Prof Regine Hock.
Total sea level rise is likely to be considerably higher, however, due to the effects of melting Greenland and Antarctic ice sheets – which make up more than 99% of the water on Earth bound up in glacier ice – and thermal expansion in the ocean.

Dr Murray Simpson, senior research associate at Oxford University's Center for the Environment, said: "All studies since 2007 clearly show that, in total, sea levels will rise 1-2 meters by the end of the century."

Radic and Hock arrived at the figures by simulating the response of 2,638 ice caps and 120,229 mountain glaciers worldwide to the changes in climate projected by 10 state-of-the-art climate models. These models were developed for the last IPCC report, including models produced by NASA and the UK Met Office.

The research found that melting mountain glaciers and ice caps have made a growing contribution to sea level rise over past decades. While mountain glaciers and ice caps include only a minor fraction of all water on Earth bound in glacier ice (less than 1%), their retreat has caused half of sea level rises from melting ice over the past 50 years.

Radic says the most noticeable impact will be on glaciers less than five square kilometers in size, about half of which could melt away. “Many small glaciers will actually disappear by the end of 21st century,” she says. The European Alps, she says, could lose between 40 and 90 per cent of their small glaciers depending on the climate model used. Already climate change has melted enough of the Alpine snow for Italy and Switzerland to decide to redraw their border after the Alpine glaciers that marked out the frontier between the two countries were dissolved.

The study, published Sunday in Nature Geoscience, excluded the enormous ice sheets in Greenland and Antarctica in a bid to focus on the impact of atmospheric warming on the smaller glaciers and ice caps dotting the planet.

“Small glaciers do matter,” says Radic, noting they are responsible for a substantial portion of sea level rise. The study concludes that by 2100 the sea level will rise about 12 centimeters as a result of “wastage” from smaller glaciers, with Arctic Canada and Alaska making some of the biggest contributions. The study estimates 21 per cent of the glacier ice will melt away by 2100, but Radic says it is a “low bound” figure because it does not include icebergs that calve off glaciers and tumble into the sea — a phenomenon that can account for 30 to 40 per cent of ice loss from glaciers that terminate at the sea.

While the study is the most detailed yet, she and other scientists stress the need to complete the global inventory of the glaciers, which currently only accounts for 40 per cent of the total. “We still don’t know exactly how many glaciers there are in the world,” says Radic, noting the size and mass of many remote glaciers in North America are not known.

The Guardian,"Glacier shrinkage will hit European Alps hardest, study claims", by Sylvia Rowley, accessed January 10, 2011
Climate Himalaya Initiative, "Planet faces great glacier meltdown by 2100: Study", accessed January 10, 2011

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