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Swiss Scientists measure glacial melting with light
02 December 2009
Zurich, University of
Changes in the thickness of a glacier are traditionally measured by means of wooden poles and snow-shovels. Those methods are inexpensive and can be carried out to determine the annual or even seasonal result at individual locations. It is, however, difficult to draw conclusions about changes in the thickness of an entire glacier or all the glaciers in the region merely on the basis of those positional measurements. The scientists now want to overcome that disadvantage of direct field measurement by applying laser technology.
Philip Jörg, a Ph.D candidate involved in this project, explains how it works: «A strongly bundled beam of light is shot from an aircraft and the time is measured that the light needs to reach the surface of the ice and bounce back to the aircraft. From this so-called "run time", the distance from the plane to the glacier can be precisely determined to within just a few centimetres». The laser data and the exact location and position of the aircraft give rise to a highly precise, three-dimensional picture of the glacier's surface.
49 million cubic metres of ice lost
Researchers at the University of Zurich carried out a corresponding campaign in October of this year with a high-resolution laser scanner at the Findel Glacier close to Zermatt. The surface model that was created was compared with the results of a first flight over the glacier in the year 2005 and now enables a conclusion on the changes in thickness and volume of the entire glacier. In those four years, the Findel Glacier has lost almost 3.5 metres of average ice thickness, and as much as 25 to 30 metres at its tongue. Overall, the glacier has lost around 49 million cubic metres of ice. If that volume of ice were melted and emptied into the Lake of Zurich, the water level of the lake would rise by about half a metre.
The next flight is planned for the forthcoming spring. The researchers anticipate new findings with regard to the spatial distribution of the winter snow coverage and its characteristics in terms of water content and reflectance. «While the politicians will be in Copenhagen in the next few days, debating a continuation of the Kyoto Protocol with specific climate targets, we are already working on the basic data of tomorrow», says Michael Zemp, the head of the project and a glaciologist at the University of Zurich.
Virtual, three-dimensional view of the Findel glacier near Zermatt, based on laser data from 2005, superimposed with an aerial photograph from 2006. (swissphoto, approval from swisstopo BA091673)
The Findel glacier lit up, superimposed with changes in the thickness up to 2009. The colors green to red represent the loss of ice, blue shows increased thickness.