Alpine glacier response to increasing temperature between 2009 and 2022. Insights from photogrammetric analysis in the Ötztal and Zillertal Alps (AT).

The European Alps have experienced massive glacier loss over the last decade, and 50% of all glaciers are expected to disappear even under current climate conditions by 2050. Glacier retreat, rapid meltwater production and damming, debustressing, and accelerated release of sediment massively increase the natural hazards in the region. The decline of glaciated areas in alpine regions directly impacts water reservoirs, tourist infrastructure, and alpine communities; therefore, precise quantification of rates of glacier retreat at a regional scale are paramount for foreseen prevention and mitigation plans.The location and extent of mountain glaciers are conditioned by two independent factors: topography and climatic conditions. In this contribution, we explore the glacier changes over the last decade in two contrasting regions: (i) the drier and colder Ötztal Alps, host of the largest glaciers in Austria, and (ii) the wetter/warmer Zillertal Alps. Our aim is to decipher the key factors controlling glacier retreat at the regional scale. We used photogrammetric reconstruction of high-resolution aerial imagery at a 20cm resolution to (i) manually map the glacier extent in 2009/2010 and 2022 for 87 glaciers in the Zillertal and 48 glaciers in the Ötztal. The manual mapping was supported by stereographic visualizations for a precise photo-interpretation of glacier boundaries, (ii) quantify glacier retreat for each glacier in terms of relative area change (km2) and geodetic mass balance (m w.e.a-1), and (iii) calculate morphometric parameters such as slope and slope orientation. Finally, we contrasted ERA5 precipitation and temperature data with the findings.This study presents a unique compilation of glacier extents and geodetic mass balance over 202 km² of the Ötztal and 184 km² of the Zillertal Alps from 2009 to 2022. Despite the contrasting morphological and climatic characteristics, glaciers in both mountain ranges retreat at similar rates. These findings demonstrate the dominant climatic control on glacier loss in the Eastern Alps and suggest that, under current climatic conditions, glacier morphology plays a minor role at the regional scale.