Snow Cover Dynamics and Mass Balance on Mountain Glaciers

Glaciers contribute to sea level rise and to local and regional water supply. Moreover, they are highly evident indicators of climate change. Mountain glaciers and their mass changes are particularly difficult to measure and to detect, mostly for inconvenient logistical circumstances. As a result, only from few glaciers we have annually reported bulk mass balance information from which researchers extrapolate to larger and unobserved regions with considerable uncertainties. This unsatisfying situation can be substantially improved when analyzing the mass and energy fluxes that drive glacier changes using (spatially) distributed modeling at high temporal resolution. The largest unknown to be overcome is the development of the snow cover from precipitation to wind-induced redistribution and densification and, finally, its degradation. The seasonal duration of the snow cover depends on these processes and, through its high reflectivity against sunshine, dominates the wellbeing of a glacier. Theory and understanding of processes is well advanced and models are ready to be tested and used, yet respective measurements are missing. We will combine the expertise of our team members from the Universities of Innsbruck, Erlangen-Nuremberg and Saskatchewan with the logistically suitable, data rich, and well equipped Hintereisferner in the Ötztal Alps, Austria, for developing and calibrating novel model tools that can push mass balance studies a large step forward in glaciology. In the end we aim to obtain an effective parameterization of snow drift, which will not only increase the process understanding of glacier-climate interactions, but also be available for future studies of glaciers in climatic settings around the world.

When glaciers lose mass, this contributes to sea level rise and changes the availability of water in the mountains in summer. If we know the amounts of change, we can also assign them to possible causes and we can determine whether natural climate fluctuations or man-made climate change is the reason. We know mass changes from a few dozen glaciers worldwide, from only a few of them for longer than two decades and only in the temporally coarse resolution of annual values. From this limited and insufficiently spatio-temporally resolved information, we can only inadequately investigate the questions mentioned above. Our research work centres on the dynamics of snowpack development at high temporal and spatial resolution, the most efficient process of glacier mass change apart from melting. In our FWF-DFG project, we have set ourselves the task of taking a closer look at the respective processes, measuring them and translating them into a modelling language. The measurements were carried out using a terrestrial laser scanner installed high above the Hintereisferner and controlled from the office in Innsbruck. With a spatial resolution of approx. 10 cm, we were able to measure changes in the glacier surface several times a day, correlate these with meteorological parameters and thus calibrate the snow cover dynamics model. We have thus succeeded in taking a major step towards subsequently applying this model temporally and spatially beyond the measurement periods and locations. From meteorological and terrain data, it should now be possible to calculate mass changes of any number of glaciers in the past and in the future, to determine sea level fluctuations more precisely and, above all, to improve the identification of the causes of the changes. For the most recent years, we have been able to determine the day on which the Hintereisferner lost all the mass it had accumulated over the winter since 1 October of the previous year. In the case of a glacier in equilibrium, this day should be 30 September. In 2022, it was 23 June and the Hintereisferner had lost another 3 metres in thickness or 20 million m of water by 30 September 2022. This could supply Innsbruck with water for almost 2 years.