How to balance the voids? Tackling rapid ice loss in western Austria

The extreme melt during the years 2022 and 2023 resulted not only in up to 3 m w.e. ice loss, but also to rapid shrinkage of glacier area. As a result of thinning in all altitudes, an increase in pace of area loss can be expected for the next years. The area loss for long term mass balance glaciers reached up to 10% in 2023 for Jamtalferner. This similar to the area loss of the last decade and rises the question, how significant the tracking of the area loss influences the accuracy of in situ mass balance, as we traditionally calculate mass balance based on the area of the previous year.

Another open question regarding mass balance methods are effects of the repositioning of stakes into flat areas with low debris cover which is forced by increasing rock fall activities. There also is evidence of wide spread melt at the base of the glacier which is so far unquantified.

With rapidly shrinking areas, specific mass balance curves and total balance show larger differences, i.e. although specific mass balance increases, the areas shrink so rapidly that the total melt water runoff decreases. Equilibrium line is above summits for most of the mass balance glaciers in western Austria in most years of the last decade.

So far, the Austrian glacier inventories did not split up glaciers in smaller entities, to allow to tackle the evolution of formerly larger glaciers without accounting for parent and child IDs. Now, for some glaciers the ice remnants are clearly not fulfilling the criteria for a glacier, as they consist only of a small part of the former glacier tongue, where the ice has been thicker and survived the former ablation area. Tackling glacier loss in a consistent way turns out to be tricky, as remote sensing data often does not allow to distinguish debris covered glaciers from cold rocky landforms as frozen base moraines. Aerial photography or LiDAR elevation models would be needed in shorter repeat periods as the decadal intervals used so far. During summer 2023, some smaller glaciers disappeared within weeks, and it is also the pace of this loss which is quite informative and relevant for local hydrology and hazard situation.