However, the weather in summer is decisive for the rate of melting of the glaciers, underlined the ZAMG in a program on Tuesday. As part of the ZAMG glacier monitoring program, the glaciers of the Hoher Sonnblick (Goldbergkees and Kleinfleikees) are measured every spring and the mass balances calculated in cooperation with the University of Natural Resources and Life Sciences in Vienna. “In order to calculate the increase in mass last winter, we determined the depth of the snow with probes at about 600 points on the glacier and dug snow wells at seven other positions to measure the density and temperature of snow,” explained glacier expert Anton Neureiter of ZAMG. “The mass of water contained in the snowpack was then calculated from the measured snow depths and densities.”
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“The most important weather in summer”
This year’s measurements paint a less than encouraging picture: the average spring snow depth on the Goldbergkees was 330 centimeters (70 centimeters less than the average for previous years). This corresponds to a mass increase of 1,355 kilograms per square meter, or 20% less than the average of recent years. On Kleinfleikees the average snow depth was 260 centimeters – 90 centimeters below average. This corresponded to a mass increase of 1,028 kilograms per square meter (28% below average).
According to ZAMG, there has rarely been so little snow here since the start of the measurements. The Goldbergkees have been measured regularly since 1987, the Kleinfleikees since 1999.
However: “For the long-term development of glaciers in Austria, the weather in summer is more important than in winter,” explained Neureiter. “The deciding factor is whether occasional cold air storms bring snow to glaciers in summer. Because fresh, very white snow cover reflects nearly 100% of the sun’s rays and can prevent glacier to melt for up to a week. A glacier without fresh snow, on the other hand, is much darker, therefore absorbs a lot of solar radiation and can lose up to half a meter of ice thickness in a week.”
Pasterze as a showcase project
According to ZAMG, the regular determination of the mass balance of glaciers in the Sonnblick and Pasterze region is now a flagship project for standardized monitoring in the Global Cryosphere Watch program of the World Meteorological Organization (WMO). The methods are constantly evolving and drones have also been used since 2019.
Using drones, a very precise 3D digital model of the glacier is created. The flights take place during the winter balance measurement at the end of April and at the end of the melting period around the end of September. By comparing height models, the volume change of glaciers is calculated and can then be compared with the directly measured glaciological method.
According to ZAMG, this comparison makes it possible to record the surface mass change of glaciers even more precisely and to be able to better quantify the contribution of melting to the glacier bed. In addition, it allows conclusions to be drawn about the vertical movement of the ice, which increases the accuracy of snow depth measurements using drones on the moving glacier.
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