Future retreat of Great Aletsch Glacier and Hintereisferner – an East-West comparison

Glaciers in the European Alps play an important role, e.g. for water storage, water supply and the ecosystem. Here, we model the future evolution of two valley glaciers in the European Alps over the course of the 21st century. The Great Aletsch Glacier is located in the Western Alps (Switzerland), while the Hintereisferner is in the Eastern Alps (Austria). The two different glacier locations allow us to compare glacier development in the Western and Eastern Alps in a changing climate. We use a three-dimensional model that combines the full Stokes ice dynamics and basal friction inversion on a 25m horizontal grid. The coupled energy balance model computes the surface mass balance based on high-resolution regional RCP8.5 and RCP2.6 climate model (RCM) data from the EURO-CORDEX ensemble (a total of 62 different GCM-RCM combinations). In addition, SSP5-8.5 and SSP1-2.6 of the newer CMIP6 generation have been calculated based on the ISIMIP3b ensembles (10 different GCMs in total). All simulations show a dramatic volume loss, with the GAG disappearing in 2100 under the high-emission scenarios (RCP8.5 and SPP5-8.5) and the HEF already disappearing in around 2060. A special feature is that the HEF shows a similar volume loss under SSP5-8.5 and SSP1-2.6. The GAG has the ability to stabilize under SSP1-2.6.