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Wednesday, December 11, 2013
- Receding Alpine glaciers are appearing a sure telltale of global warming. In Switzerland, 84 out of 85 glaciers under observation became shorter in 2006.
The hot summers and the lack of precipitation in recent years will accelerate the melting process even more, scientists say.
Glaciers are large masses of snow, ice and rock debris that accumulate in great quantities and begin to flow downwards under pressure of their own weight. They are formed when yearly snowfall in a region far exceeds the amount of snow and ice that melts in a given summer, like in the Swiss Alps.
The results published by the Swiss Academy of Sciences confirm the measurements of previous campaigns, which clearly showed that Swiss glaciers are shrinking. Approximately three-quarters of the observed shrinkage in 2006 is between one and 30 metres.
On top of the list this year was the small Suretta glacier in the canton of Graübunden, which lost 725 metres of its length. This is due to the fact that since last year the ice tongue has been broken up in separate patches that melt more rapidly.
The 24-km long Aletsch glacier in the canton of Wallis, Europe’s biggest glacier and part of the United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage, receded 114 metres.
“The Aletsch has been receding steadily over the past 150 years,” Swiss glaciologist Andreas Bauder of the Zürich-based Federal Institute of Technology (ETH) told IPS. “The smaller glaciers have shrunk and then grown again, but in the last 20 years they are all getting smaller.”
The measurements clearly show the sensitivity of Alpine ice masses to global warming, though with a certain delay depending on their length. “A big glacier like the Aletsch gives you the long-term picture and will remain unaffected by a series of hot summers. A smaller glacier will react more quickly to climate changes, which makes them more vulnerable,” Bauder said.
Two variables enter into the glacier equation: temperature and precipitation. “Typically you would expect rising temperatures to lead to more precipitation, because warmer air can contain more water,” Bauder said. “We do measure a bit more rain and snowfall, but apparently not enough to compensate for the rising temperatures.”
To get an immediate feedback on the weather pattern of the last year, the survey teams also measured the “mass balance”. The measurement reflects the balance between the fresh snow the glacier receives from the surrounding area and the ice that melts away in a given year, and thus gives an idea of the state of health of a glacier.
The three glaciers under examination show a negative mass balance for several years in a row, which leads to expectation of a further recession. Last year was particularly bad because of little snowfall in the winter of 2005/2006. The Basodino glacier on the southern slopes of the Alps lost even more of its mass than after the extremely hot summer of 2003.
In Switzerland, glaciers play an important role as water reservoirs for hydro-power production (generating half of all electricity). They are a vital source of water, and without them summer water levels in Europe would drop substantially. Moreover, they are frequently associated with natural hazards endangering humans and infrastructure.
Steep glaciers are prone to ice avalanches, like the one from the Gutz Glacier in Grindelwald in 1996, which affected road infrastructure and injured tourists.
Glacier retreat can lead to the formation of lakes, typically in the recently de-glaciated area in front of a glacier. Such lakes are often dammed by large moraines consisting of loose glacial sediments. The potential instability of moraine dams makes the lakes prone to water outbursts, with potentially devastating effects on the steep yet densely populated Alpine valleys.
Scientists of the Laboratory of Hydraulics, Hydrology and Glacioloy of the ETH Zürich have compiled a list of 82 glaciers which in the past have inflicted damage on persons or property. Fifty-one of these are expected to cause new damage within the next 10 to 20 years.
The lower Grindelwald glacier already made the headlines in 2006. On Jul. 13 500,000 cubic metre of rock crashed down because it was no longer supported sideways by glacier ice, which had receded. The rockslide had been announced in advance, which allowed spectators on the terrace of a mountain hut on the opposite slope to watch the spectacle having coffee and cake.
Research using satellite images by the University of Zürich indicates that Switzerland’s glaciers lost 18 percent of their surface between 1985 and 2000, at a rate seven times faster than between 1850 and 1973.
Small glaciers contributed disproportionately to the total loss of glacier area: they represent 18 percent of total glacier area but 44 percent of the losses incurred. By 2025, scientists expect a glacier area loss of 30 percent. (END/IPS/EU/EN/KP/MC/SS/07)