Measurements on the Tyrolean Hintereisferner
The project team has chosen the Hintereisferner as the starting point for their work. The Hintereisferner is a comparatively large glacier covering an area of six square kilometres, but nevertheless easily accessible. It is situated in the rear Ötztal valley near the border between Tyrol and Italy – not far from the place where the mummified ice man nicknamed “Ötzi” was found. What recommends the Hintereisferner is the fact that it is one of the best researched glaciers in Austria and the Alps in general. A measurement infrastructure, globally unparalleled in this form, has been in place here since 2016: a permanently installed laser scanner that is remotely controlled from Innsbruck and can produce daily scans of the glacier surface. Changes in height, volume and mass can be calculated from the terrain models that are produced on the basis of the extensive measurement data. Complementing the traditional compilation of mass balance using level bars, this technical tool is an important aid for Goger and the research team to produce advanced modelling of glacier physics.
In the first phase of the project, Annelies Voordendag, a PhD student at the Department of Atmospheric and Cryospheric Sciences, had the task of investigating how accurate and how prone to error the measurement system was. These factors depend on aspects such as measurement distance, weather and wind, and are thus essential for meaningful models using them as a basis. “We have learned that we are able to achieve measuring accuracy with maximum deviations of about ten centimetres – that is good enough also to be able to derive the daily snowdrift from the terrain models,” says Goger, who is using the data to develop her own “snowdrift module” for glacier modelling.
Interaction Between Ice and Atmosphere
The results will enable the researchers to interrelate the data on the glacier surface, which changes daily because of precipitation, melt or snowdrifts, with an atmospheric model. As Goger points out, the air movements above the glacier are particularly complex: “The heat exchange between the ice surface and the atmosphere above it is very inhomogeneous, and this has a great influence on local air movements. This is yet another aspect that influences the glacier’s mass balance.” Moreover, the ice masses are usually surrounded by a cold layer of air, which counteracts warm currents near the surface and slows down faster melting. The modelling could also provide information on how much mass a glacier can lose without losing this “protective shield”.
Just as the measurement data from the laser scanner improve the glacier models, the findings from the models should provide information about sources of error and inaccuracy in the measurements – thus leading to further improvements. Upcoming publications in the context of the project, which was recently extended by one year, will provide information about this improved accuracy of measurements of snowdrift. In addition, Goger is also working on a first winter case study showing a simulation of snowdrift based on the measurement data. According to Goger, researchers in other regions of the world could thereby profit from these computational approaches: “If the models work well with the Hintereisferner, other colleagues, in Canada, for example, who have to deal with much larger ice masses, could also try them out – and optimise them for their own areas of investigation.”