AbstractThe last remaining very small glaciers (< 0.5 km2) of the Pyrenees are the southernmost glaciers in Europe and respond rapidly to climate variability. Most of them are also influenced by local topographic factors and geomorphological processes impacting the energy and mass balance. This paper presents the first temporal study on the changes in debris cover on Pyrenean glaciers from 2000 to 2022 at a regional scale. The data allowed for the first analysis of the lithological characteristics of each glaciarised cirque in order to identify possible factors that determine the evolution of debris input. We manually mapped the extent of supraglacial debris with corresponding glacier outlines using very high-resolution aerial imagery and the existing glacier inventories from 2000, 2011, 2020 and 2022. The results show that debris cover on Pyrenean glaciers has increased significantly in number and extent over the study period whilst glaciers continue to decline and shrink. In 2022, 14 of the 18 remaining glaciers have debris cover greater than 10% of their area, and six have debris cover greater than 40%. The observed increase in debris cover is much stronger for glaciers determined by topoclimatic factors and located on metamorphic and sedimentary cirques, which underlines the important role of paraglacial processes in their development. Meanwhile, glaciers on granitic cirques have lower debris cover and have shown a lesser increase compared to initial measurements conditions. Future work should focus on understanding debris sources and their characteristics to determine the role of debris cover in the response of Pyrenean glaciers to climate change.
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