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Swiss glaciers shrinking fasterPosted: 21 Dec 2008
Two new studies presented at the latest American Geophysical Union meeting in San Francisco 15-19 December show that Swiss glaciers are shrinking, and shrinking at an increasingly rapid rate. This means that researchers are observing the same phenomena in the Alps that have already been reported in the Himalayas and in the Andes.
Swiss glaciers are melting away at an accelerating rate and many will vanish this century if climate projections are correct, two new studies suggest.
One assessment found that some 10 cubic km of ice have been lost from 1,500 glaciers over the past nine years.
The other study, based on a sample of 30 representative glaciers, indicates the group�s members are now losing a metre of thickness every year. Both pieces of work come out of the Swiss Federal Institute of Technology.
�The trend is negative, but what we see is that the trend is also steepening,� said Matthias Huss from the Zurich university�s Laboratory of Hydraulics, Hydrology and Glaciology.
The investigators reported that there has been no measured change in snowfall accumulation, which when combined with melt rates, determines a glacier�s mass balance. Rather the melting away of the Swiss glaciers is attributed entirely to a longer melt season resulting from global warming.
Daniel Farinotti and his team tried to assess the total volume of ice in Swiss glaciers - 1,500 of them, from the mighty Aletschgletscher (the largest glacier in the Alps) to small ice fields that cover less than three square km.
The research used direct measurements where available, and combined this with modelling to estimate ice volumes for areas that are data-deficient.
The assessment found a total ice volume present in the Swiss Alps of about 75 cubic km by the year 1999 (a baseline for the purpose of the study). It is a bigger figure than previously thought.
�However, 1999 is quite some time ago now, so what we did was try to calculate the volume lost since this baseline; and we estimate a figure of 13 per cent - from 1999 to today,� explained Mr Farinotti.
For 2003, remembered for its strong heatwave across Europe, the team estimates that 3-4 per cent of the volume in Switzerland at that time was lost in that one year alone.
Farinotti points out that the largest 50 Swiss glaciers hold 80 per cent of the total ice, which is fortunate since the smaller glaciers will all be gone within a few years. The largest glacier, the Aletschgletscher, is expected to survive until the end of the century.
|Area covered by the glaciers - Aletsch: 83.01sq km; Rhone: 16.45sq km; Gries: 5.26sq km; Silvretta: 2.89sq km. The cumulative mass balance is given in "metres of water equivalent". Essentially, it records the net thickness change of the glaciers. Thickness change over the entire period - Aletsch: -65m; Rhone: -43m; Gries: -97m; Silvretta: -35m. Credit: BBC
The other study by a team lead by Matthias Huss analysed four glaciers in the Swiss Alps over the period from 1900 to 2007.
The conclude that "mass balance evolution of these four glaciers has undergone significant fluctuations. Two decadal periods of mass gains are found, which are due to less negative summer balances. The general trend since 1865 is strongly negative, however, displaying large differences between neighbouring glaciers. The most negative mass balances occurred in the 1940s. This is due to extraordinarily low winter accumulation and high summer temperatures."
The glaciers' loss would have profound ecosystem and economic consequences. "Glaciers store the water in winter and release it in the summer when it is dry and warm when there is more need for water," said Mr Huss. "And they can also store it in the wet and cold years and release it in the hot and warm years. That's an important reservoir.
"In the south-western part of Switzerland, almost all run-off water from glaciers is temporarily stored and used for electricity production. More than half the electricity consumed in Switzerland is produced from hydropower."