Swiss glaciers lose 5.5 percent of their ice in a single hydrological year

Swiss glaciers lost 5.5 percent of their ice volume in the hydrological year 2025/26, the second-largest percentage drop on record. The Glacier Monitoring Switzerland office, GLAMOS, put the average mass balance at minus 2.86 metres of water equivalent. Only 2022, at minus 3.13 metres, was more negative.

The figures come from the annual report by Matthias Huss, Andreas Bauder, Andreas Linsbauer and Martina Barandun, published on 23 September 2026 under doi 10.18752/annualrep_2026. Extrapolated across the country, the specific balance equals a further 5.5 percent cut in the national ice stock. GLAMOS and the Swiss Academy of Sciences said Alpine glaciers have no chance of surviving in the long term under these conditions. Some individual glaciers set all-time records for annual loss.

By the end of 2026 Switzerland still held about 42.6 cubic kilometres of glacier ice. That is more than 30 cubic kilometres less than in 2000. The remaining glacier area is estimated at 714 square kilometres, about one third smaller than at the turn of the century. The year removed 2.5 cubic kilometres of ice. That volume ranks only third in recent decades for water delivered downstream, behind years when the ice area was larger. In 2003 the specific melt rate was about 25 percent lower than in 2026, yet the absolute runoff was higher because there was simply more ice to melt.

The mechanism is the same one glaciologists have described since the hot summers of 2022 and 2023, only tighter. Winter snow was thin. Summer heat waves arrived early and stayed. The protective snow cover on the tongues disappeared, and bare ice, which absorbs more sunlight than snow, took the rest of the season. Thickness on individual glaciers fell by about 2.5 to 4 metres. On some tongues the loss reached 10 metres. The Independent, citing the same monitoring groups, put the July to September melt at 2.2 trillion litres, about four times the annual water use of a country of 9.1 million people.

The percentage drop looks larger than older bad years because the base is smaller. A 3.5 percent loss in 2003 came off a much bigger stock. A 5.5 percent loss now comes off an ice body that has already shed a third of its area. That is why a year that is only the second worst in specific balance can still feel, in the valleys, like a structural change rather than a bad season.

Downstream the water is not a free gift. The 2.5 cubic kilometres that left the ice this year entered rivers in summer, when hydropower and irrigation already count on melt. The problem is the trend line. Once the tongues retreat above the elevation where summer snow used to persist, the same heat removes a larger share of what remains. Hydropower operators on the Rhone and the Rhine tributaries have already shifted reservoir rules to catch earlier peak melt. Those rules do not replace the ice.

GLAMOS measures a network of reference glaciers and extrapolates. The 2026 report is the operational account, not a model run of 2050. The number that matters for the next winter is the one on the page: minus 2.86 metres of water equivalent, 5.5 percent of the volume gone, 42.6 cubic kilometres left. Another year at this rate would take the stock under 40 cubic kilometres before the decade is out.