To counteract the melting of permafrost caused by climate warming, St. Moritz is testing an unprecedented solution: artificially cooling the mountain to stabilize the ground.
Permafrost, invisible yet essential, is a cornerstone of alpine stability. When it warms, it loses its “glue-like” function, and the mountain cracks, slips, and sometimes collapses.
Geologists estimate that about 5% of Switzerland’s territory is affected by permafrost. Although this percentage is low, it concerns very sensitive areas, especially above 2,500 meters, where ski resorts, hiking trails, and lift systems are concentrated.
Faced with this threat, the company that manages the lift systems, Engadin St. Moritz Mountains AG, has decided to take action. This summer, it began major work: installing thermosiphons. These devices, known in the heating sector, are used here in reverse, to cool the mountain.
The principle is quite simple: a thermosiphon is a metal pipe filled with a refrigerant fluid (compressed carbon dioxide). When the surface air cools, even slightly during the night, the fluid naturally circulates downward, dissipating the heat accumulated in the ground. The expected result: stabilize the temperature of the permafrost and slow its melting.
“What we’re doing with this system is giving nature a helping hand: we remove more heat from the ground. This way, it’s colder than it would naturally be, which allows the permafrost to survive the summer,” explained Lukas Arenson, a geotechnical engineer specializing in permafrost at the Canadian firm BGC Engineering, responsible for the project. In concrete terms, sixteen thermosiphons have been installed on the slopes of Piz Nair, at around 3,000 meters above sea level. Each one is 15 meters long, anchored deep into the rock, and connected to a monitoring system. The device is designed to last about 30 years.
The investment is significant: €1.9 million (1.8 million Swiss francs) to equip Piz Nair.
These thermosiphons are not an entirely new concept. They are already used in some regions of Canada, Russia, and even the United States, in Alaska, to protect roads and pipelines built on permafrost. But this is the first time they have been installed in Switzerland—and in Europe in general—on this scale and with a purpose explicitly linked to mountain tourism.
