The Pyrenean glaciers, monitored with drones and satellites to prevent accidents

The Nepal disaster, where a Himalayan glacier collapsed, has also focused attention on the nearly 140,000 mountain glaciers estimated to exist on Earth, which are losing ice at a rapid pace. Currently, few glaciers have thorough on-site monitoring, although much progress has been made with new technologies. In Spain, the 14 existing glaciers, all in the Pyrenees and retreating, are monitored and pose little risk. What is now of particular concern is the permafrost, the frozen ground and rocks, given the increase in rockfalls that cause accidents.

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Scientists conduct monitoring using drones, satellites, sophisticated laser technologies, and radars. In Spain, these days the Pyrenean Institute of Ecology (IPE-CSIC) begins its glacier monitoring campaign, a control that is delayed each year due to the extended summer.

Geographer Juan Ignacio López Moreno explains that all the snow fallen this year has already melted due to high temperatures. “Looking at the webcam images of Monte Perdido and Aneto, it is clear that this is a very bad year for the mass balance of these glaciers.” Everything indicates it will be negative. “We try to visit each glacier at the same time every year, although we know it will continue melting this month.”

Until recently, the method to assess the glacier’s balance and evolution consisted of placing stakes, located by GPS, to count the fallen snow and check how the ice moved. In 2011, a terrestrial laser scanner began to be used, increasing data points from a dozen to 500,000.

“They allow centimeter resolutions to see the snow. For movement, we use an interferometric radar, which detects accelerations caused in the glacier as meltwater accumulates, infiltrates, and generates the risk of collapse in some part. Recently, such an anomaly was detected in the French Alps,” explains López Moreno. This method has helped them verify that a large part of the Monte Perdido glacier no longer moves, but another part moves about three meters per year.

This laser system, however, had problems: there were blind angles and it weighed 50 kilos, so since 2019 the equipment has been replaced by drones. “With the five we have, we make a complete digital map of each glacier and compare it each campaign. We have gained much precision and control capacity every year,” he assures.

Not only do they take photos, but they also carry thermal cameras to measure surface temperature and a laser sensor. The information captured on the ground is complemented by satellites from space (Sentinel or Cosmo SkyMed).

“Even if there were a small glacier collapse, it would be far from human activities. More problematic are rockfalls caused by permafrost degradation, frozen rocks above 2,500 and 3,000 meters. With melting, between Aneto and Madaleta, block falls already occur in summer,” he recalls.

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This presence of Pyrenean permafrost has recently begun to be studied in detail, thanks to the European project PermaPyrenees, active until the end of 2027 to study its evolution in the mountain range. “After a campaign at the rocky glacier of Besiberri, in Lleida, a mountaineer was injured. Ice glaciers will disappear, but permafrost will remain and it is necessary to know where it is and its condition.

We have been working for two and a half years and see that its distribution is more complex than we thought because it depends not only on altitude but also on topography or rock type,” says the project coordinator, Marc Oliva, from the University of Barcelona. If that ‘glue’ melts, the mountains collapse… “To know if the rock loses stability, you have to know where that ice is, at what temperature, if it is north or south facing, if it is granitic or limestone, or the altitude,” he explains.

To carry out this work, they insert thermometers into boreholes up to 15 meters deep and send electrical signals to map what is up to 45 meters. With this, they create melting models by zones.

They thus discover a type of permafrost invisible on the surface: rocky glaciers, which are covered by stones and may have an ice core inside that moves slowly, as in Besiberri. “We are finding more active glaciers of this type than we thought. This week we went to collect data from Argualas, in Huesca, because on the surface it leaves arches that indicate it moves,” López Moreno indicates.

Recently, in the Madaleta massif, they have installed two new devices: a seismograph to receive signals associated with rockfalls, and an instrument that measures crack openings. “It is about understanding the behavior in unstable high mountain zones that can cause impacts much further down,” says the IPE-CSIC scientist. “Until a few years ago, glacier study was marginal in the Pyrenees. We don’t have large ones, but against melting, especially of permafrost, monitoring is essential. And if there is an unusual displacement, notify the corresponding authorities,” he concludes.