Collapse on Aneto: Spain's largest glacier fragments and retreats to 30 hectares

The Aneto glacier , the largest in Spain and southern Europe, has suffered a critical fracture that has reduced its surface area to 30 hectares after losing 3,6 hectares during the 2024-2025 hydrological year, as reported this Monday by the CryoPyr Group of the IPE-CSIC (Spanish Institute of Pyrenean Glaciers - Spanish National Research Council ). The rupture beneath Pico del Medio has separated the main body of ice located below Collado de Coronas , which is now considered a snowfield , no longer meeting the criteria to be classified as a glacier. Monitoring carried out in September 2025 confirms an average loss of 1,2 meters in thickness and ranks this year as the third worst in terms of retreat since annual measurements began. The scientists' diagnosis is stark: if the trend continues, the Pyrenean glaciers will disappear within a decade.

A glacier melting in real time

The Aneto glacier is undergoing a visible and accelerated physical collapse. During the 2025 expedition, the main body of ice fractured completely beneath Pico del Medio , a process researchers describe as a " dismemberment ." The ice mass that had remained intact beneath Collado de Coronas no longer meets the geomorphological requirements to be considered a glacier: it has lost the internal movement that defines these ice masses and has been reduced to a residual ice patch.

Researcher Jesús Revuelto , from the CryoPyr group, succinctly described the phenomenon with a powerful image: “ It’s as if a body were being dismembered, leaving only the dead parts .” This phrase encapsulates not only what happened on Aneto, but also the shared fate of the Pyrenean glaciers, which are undergoing a process of degradation that has accelerated in the last decade.

A devastating year: the third worst balance in the historical series

The losses recorded this hydrological year place 2024-2025 as the third worst year since continuous measurements have been available, only behind the dramatic 2021-2022 and 2022-2023. All the glaciers monitored by CryoPyr lost more than one meter of thickness on average , although the magnitude of the retreat varied from one massif to another.

The glacier of Ossoue (Vignemale) It was, by far, the most punished: it lost an average of 3,4 meters and even registered occasional drops of 5,4 metersfigures reminiscent of the collapses observed in alpine glaciers during extreme summers.
In Monte Perdido and Llardana (Posets), the thickness reductions were 1,3 y 1,4 metersrespectively, while the glacier of Hells, after registering 1,8 meters of average loss, it has been officially reclassified as an ice ship.

Despite this widespread loss, researchers detected small areas of gain linked to old snow that survived the summer. Notable examples include the 2,8 meters of accumulation on Monte Perdido and the 1,6 meters in the upper reaches of Aneto. However, CryoPyr indicates that “ these local gains do not offset the negative mass balance ,” which has become structural.

The accelerated degradation of the Pyrenean glaciers

The retreat of Aneto is not an isolated phenomenon, but rather the most visible expression of a long-term climatic process that has affected all the Pyrenean glaciers. In the last ten years, according to data from the IPE-CSIC (Spanish Institute of Pyrenean Glaciers - Spanish National Research Council), more ice has been lost than remains . The trend is so pronounced that it is no longer referred to as retreat, but as terminal decline.

For Nacho López Moreno , leader of CryoPyr, the diagnosis is clear: “ There is no hope for the Pyrenees glaciers .” The researcher emphasizes that, even in optimistic climate scenarios, the combination of winters with irregular precipitation, long, hot summers, and increasing exposure of the ice to the sun makes their disappearance practically inevitable. “ If this pattern repeats itself for another decade, we will have no glaciers left ,” he states.

This process has implications that go far beyond the symbolic. Glaciers act as water reservoirs , thermal regulators , and extremely sensitive climate sensors . Their disappearance signals a profound change in the Pyrenean climate regime and in the region's hydrological balance.

Rigorous monitoring for a changing landscape

Measurements of Aneto and the other Pyrenean glaciers are carried out thanks to the support of the BBVA Foundation , the Government of Aragon , and the State Research Agency , which allows for detailed annual monitoring. Fieldwork is conducted in late summer, when snowpack has melted and the ice is more exposed, enabling measurements of losses in thickness, volume, length, and surface area.

The data accumulated over the last few decades leaves no room for doubt: climate change is dismantling the Pyrenean glaciers at an accelerated and irreversible rate. Projections indicate that even if global warming stabilizes, the remaining ice is already too degraded to recover.