Rapid changes of Alpine glaciers in Austria tracked by ALS surveys
<p>Unprecedented glacier changes are reported for many mountain regions on earth based on surveys with different spatial resolution and repeat intervals. Eastern Alpine glaciers have been receding since the LIA maximum, with increasing relative volume loss at the beginning of the 21<sup>st</sup> century. New high-resolution data of surface elevation from ALS surveys enable the analysis of most recent glacier changes at three mountain ranges in western Austria as an impact of climate change.</p><p>Surface elevation change rates between 2007 and 2018 increased again in comparison to former periods. Volume loss takes place even in the highest elevation zones, and most of the glaciers are out of an equilibrium state, such that consolidation of mass balance towards zero appears impossible under present climate conditions. The disintegration of low lying glacier tongues and a strong depletion of the firn cover are further signs of rapid glacier changes. The frequency distributions of surface elevation change throughout the area of each glacier show distinct shifts in peak ice thickness change and patterns of surface change distribution that suggest ongoing processes of glacier disintegration. Combining recent surface elevation changes and estimations of the spatial distribution of ice thickness in Austria shows that most of glaciers will vanish in 50 years or less. Only glaciers currently larger than 5 km&#178; can be expected to exist longer at reduced size. At current rates of mass loss, glaciers are projected to retreat entirely to above 2800m in the &#214;tztal and Stubai ranges by 2050. Further concerns arise regarding methods of tracking the future development of the remaining ice bodies. In particular, in the Silvretta mountain range, the majority of glacier margins have to be delineated in debris-covered glacier zones. It is debatable whether some of the smallest glaciogenic features should still be accounted for in glacier inventories or moved to an inventory of transient cryogenic landforms.</p>