Light Measures Glacial Melt

Changes in the thickness of a glacier traditionally are 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.

This virtual, three-dimensional view of the Findel Glacier near Zermatt, based on laser data from 2005, is superimposed with an aerial photograph from 2006. (Image: Swissphoto, approval from Swisstopo BA091673)

“A strongly bundled beam of light is shot from an aircraft, and the time that it takes for the light to reach the surface of the ice and bounce back to aircraft is then measured,” explained Philip Jörg, a PhD candidate involved in this project. “From this so-called ‘run-time,’ the distance from the plane to the glacier can be precisely determined to within just a few centimeters.”

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.

1.7 billion cubic feet 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 11.5 ft of average ice thickness and as much as 80 to 100 ft at its tongue. Overall, the glacier has lost 1.7 billion ft³ 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 more than 1.5 ft.

The Findel Glacier, lit up, is superimposed with changes in the thickness up to 2009. The colors green to red represent the loss of ice, and blue shows increased thickness.

The next flight is planned for the upcoming 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,” said Michael Zemp, the head of the project and a glaciologist at the University of Zurich.

The research project “Laser Scanning Experiment Oberwallis” is being carried out jointly by the Glaciology and Remote Sensing units of the University of Zurich’s Geographical Department. The project will continue until 2012 and is supported by the Swiss energy utility Axpo. The laser scanning flights are carried out in cooperation with BSF Swissphoto.

For more information, visit: www.uzh.ch