The last years of Infiernos Glacier and its transition to a new paraglacial stage

Abstract Recent observations have shown a fast decrease in thickness and area of Pyrenean glaciers in some cases leading to a stagnation of ice flow. However, their transition to a new paraglacial stage is not well understood. Through the combination of uncrewed aerial vehicles imagery, airborne LiDAR, ground-penetrating radar and ground temperature observations, we characterized the recent evolution of Infiernos Glacier. In 2021, this glacier had small sectors thicker than 25 m, but most of area did not exceed 10 m. The thickness losses from 2011 to 2023 reached 9 m in average, of which 5 m occurring during the period 2020–23. This trend demonstrates the significant ice melt under current climatic conditions. In the last years, the glacier has also shown a remarkable increase of debris cover extent. In these areas, the ice loss was reduced by half when compared to the thickness decrease in the entire glacier. Sub-freezing ground temperatures evidence the highly probable presence of permafrost or buried ice in the surroundings of the glacier. The clear signs of ice stagnation and the magnitude of area and thickness decrease support the main hypothesis of this work: After 2023, the Infiernos Glacier can no longer be considered a glacier and has become an ice patch.