Record summer temperatures accelerated ice loss despite exceptional spring snowfall, putting the survival of the last active glaciers in doubt.
Glaciers in the Pyrenees suffered their third-largest annual loss of thickness on record in 2025-2026, as the mountain range’s hottest summer ever recorded accelerated melting despite exceptionally heavy spring snowfall.
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The losses were recorded by scientists at the Pyrenean Institute of Ecology and rank behind only those of the 2021-2022 and 2022-2023 seasons since comparable annual measurements began. Researchers warn that the remaining active glaciers could disappear within the next decade as rising temperatures and physical deterioration accelerate their decline.
The summer of 2026 was the warmest ever recorded in the Pyrenees, with temperatures averaging 3.4 degrees Celsius above the 1991-2020 baseline. Although spring snowfall reached historic highs in early March, weeks of prolonged heat stripped glaciers of their protective snow cover earlier than usual, exposing bare ice to solar radiation and accelerating melting.
Text Reads: 🏔️🧊 Pyrenean Glacier Status 2025–2026
Our annual monitoring campaign, using drones and high-resolution 3D models, confirms another year of significant mass loss. This marks the third-worst outcome since 2012, following the 2021–22 and 2022–23 seasons—and this despite a spring that saw record-high snow accumulation in early March. ❄️🔝
📉 Average thickness loss:
- Ossoue (Vignemale): −3.1 m
- Aneto: −2.4 m
- Monte Perdido: −2.3 m
- Llardana (Posets): −1.5 m
Furthermore, the Aneto glacier has fragmented once again, this time below the Pico del Medio. The darkening of the ice surface due to rock debris and dust continues to accelerate melting, most notably on the Llardana glacier. Increasingly warm and prolonged summers further underscore the high vulnerability of the glaciers in the Pyrenees.
The Ossoue Glacier, in the Vignemale massif, suffered the greatest losses, thinning by an average of 3.1 meters, with localized reductions reaching 4.9 meters. The Aneto Glacier, the largest in the mountain range, lost an average of 2.4 meters, with maximum losses of 4.8 meters.
Monte Perdido lost an average of 2.3 meters, while melting reached six meters in some areas. The Llardana Glacier, in the Posets massif, thinned by an average of 1.5 meters despite its favorable position for snow accumulation.
The latest figures extend a retreat that has transformed the Pyrenees’ glacial landscape over nearly two centuries. Around the mid-19th century, glaciers covered approximately 2,000 hectares across some 50 ice bodies. Their combined area had fallen to 806 hectares a century later and just 310 hectares by 2008.
More than half of the glaciers documented in the mid-1980s have since disappeared. The historical record shows a sustained retreat rather than a cyclical fluctuation, with the current temperature regime accelerating the process.
The decline is also changing the structure and behavior of the remaining glaciers. As they lose mass, ice flows more slowly, reducing its ability to carry away rocks and dust deposited on the surface. The accumulating debris darkens the ice, increasing its absorption of solar radiation and accelerating melting.
The process is particularly evident at Llardana, where rock fragments now cover almost the entire surface, leaving very little area where accumulated snow can develop into ice.
Fragmentation is another sign of the deterioration. The Aneto Glacier split again during the 2025-2026 monitoring season, this time beneath Pico del Medio, following an earlier division recorded in 2025 beneath Pico Coronas. What was once a continuous ice tongue has become a collection of increasingly small, isolated bodies.
Two of these sections no longer function as active glaciers. Instead, they have become stagnant remnants of ice, known as residual ice patches, which no longer flow and are gradually disappearing.
The retreat in the Pyrenees is part of a wider decline affecting mountain glaciers worldwide. Those in the Alps and Pyrenees have lost 38.7% of their mass in just over two decades, the largest proportional reduction recorded in any glacier region on Earth.
Globally, land-based glaciers lost 408 gigatons of ice during the 2025 hydrological year, equivalent to a 1.1-millimeter rise in sea levels in a single year.
With glaciers continuing to lose mass, fragment and lose their capacity to flow, scientists warn that the Pyrenees could lose their remaining active glaciers within the next decade.
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