International team measures how fast the Cerro Blanco glacier is shrinking

A team of glaciologists from five countries has returned from three weeks on the Cerro Blanco glacier, high in the Andes, with the most detailed measurements yet of how quickly it is shrinking. Their initial findings suggest the glacier has lost around a fifth of its surface area over the past 20 years, and that its tongue has retreated by roughly 900 metres over the same period.

The expedition was organised by the Andean Ice Observatory, a research network that monitors glaciers supplying meltwater to valleys below. Cerro Blanco feeds a river that provides water to farming communities and two small towns during the dry season, when rainfall is scarce.

Related · WorldNight train linking six northern European coastal cities confirmed for next spring

Radar across the ice

Team members dragged ground-penetrating radar across the glacier on sledges to measure the ice depth, which reaches around 140 metres at its thickest point. Drones flew repeated surveys to build a three-dimensional map of the surface, and a weather station was installed at 4,900 metres to record conditions through the year.

Dr Lucía Arandia, a glaciologist and the expedition's leader, said the thickness data mattered as much as the area. "A glacier can look much the same from above while thinning dramatically," she said. "Knowing how much ice is left lets us estimate how many years of meltwater the valley can count on."

The question for people downstream is not whether the glacier will shrink, but how fast, and how they can prepare.

Among the team were two researchers from the University of Wrenhaven, who brought radar equipment previously used on smaller glaciers in Norway. Dr Tobias Hartley, one of them, said working at altitude had been gruelling, with temperatures falling to minus 18 degrees at night and the team carrying equipment up steep moraine slopes.

The full results will be analysed over the coming months and published in a peer-reviewed journal. The observatory is also working with local water committees to plan new storage ponds and more efficient irrigation channels, so that farms are less dependent on summer meltwater in the decades ahead.