Taking a glimpse into the glacier demise of the European Alps – a 3D portrait

Glacier demise is palpable in mountain regions around the world. This retreat affects marine and terrestrial ecosystems, regional year-around water security as well as increases the risk for mountain hazards. Satellite remote sensing techniques have drawn a sinister picture of increasing rates of ice loss, particularly in the European Alps. There, model projections suggest that glaciers will largely disappear from the mountain landscape by the end of the century. Under most optimistic scenarios with a regional warming below ~3°C, one third of the ice volume can be preserved. Only the larger and more elevated ice bodies will survive. Most glaciers will however disappear. Here, we will redraw this picture combining 3D glacier evolution modelling with systematic data assimilation. In this way, a seamless record of glacier evolution in the European Alps is produced, spanning the time period 2000 to 2100 and considering various climate scenarios.  Its main asset is that no geometric simplifications are applied as typically done in current tools for regional glacier modelling. Together with inverse and ensemble techniques for data assimilation, our approach can directly ingest map products of observed surface velocities as well as the spatial pattern of the observed 2000-2020 elevation change. For our future projections, we exclusively rely on high-resolution regional climate models, better representing the atmospheric conditions over mountainous.

Our results largely corroborate the above-described grim fate for the European glacier population. The retreat is primarily driven by temperature increase rather than precipitation changes.  For the first time, 3D simulations make this retreat tangible in its full extent. Even under the most favourable climatic trajectories, glacier remnants will only survive as isolated ice patches at high altitudes. Like hermits or relicts from the past, they will have largely disappeared from the public perception in Central Europe - at the latest by 2100. We further break down our projections by Alpine sub-regions. We find more pronounced values of relative volume loss in southern and eastern regions (e.g., Rhaetian Alps). Regions with little coverage at present (e.g., Glarus Alps) will virtually become ice-free. Only exception is the French region of the Dauphiné Alps. In general, glaciers in the north-western ranges (Pennine, Bernese, Graian Alps) appear more resilient to future warming – as glacier there can retreat to higher altitudes.