Regional disparities and topo-climatic controls of glacier darkening across the European Alps since 2000

Climate warming causes increased glacier ablation around the globe. This leads to decreasing surface albedos, which trigger positive melt-albedo feedbacks, fostering continuous glacier darkening whose intensity depends on glacier-specific, topo-climatic factors. Here, we present an analysis of regional disparities of glacier darkening across the European Alps over the period 2000-2023. We derive temporal means and trends of the summer albedo of 152 glaciers from the MODIS MOD10A1 snow product. Based on this data we introduce and calculate a new measure called "glacier darkening resilience", which combines albedo mean and trend to a theoretical time span needed for the albedo to reduce to zero. Our results reveal negative albedo trends on all glaciers (-0.037±0.012 per decade). On 112 glaciers, these trends are statistically significant. The Silvretta Alps are identified as the hot spot of Alpine glacier darkening, with a decadal albedo trend of -0.059 and a darkening resilience of 69.1 years. The Adamello-Presanella Alps, in contrast, show the highest darkening resilience (215.9 years) with a decadal albedo trend of just -0.021. We find that the mean glacier albedos are primarily governed by local climates, while their trends are rather influenced by topographic factors that differ between Western and Eastern Alps.