Swiss glaciers lost more than 5% of their ice volume after a snow-poor winter

A glacier can help keep a river flowing through a hot, dry summer by releasing water stored in earlier years. When melting exceeds replenishment, that useful flow also spends part of the reserve for future summers.

Swiss glaciers lost more than 5% of their ice volume in the 2025–2026 monitoring year, according to an October 1 Reuters report, hosted by Internazionale, on findings from the Swiss Glacier Monitoring Network, GLAMOS, and the Swiss cryosphere commission. Over five years, they have shed almost a fifth of their ice volume.

GLAMOS director Matthias Huss attributed this year’s exceptional melting to a winter with too little snow followed by record summer temperatures. That sequence matters because winter snow does two jobs for a glacier.

First, it brings new water to the store. Snow that survives summer can eventually become part of a glacier’s longer-lasting ice. Winter snowfall therefore offers potential replenishment. Whether that addition lasts depends on how much survives the warmer months: a deep winter covering can still disappear before the next accumulation season.

Second, snow helps protect older ice. Its bright surface reflects sunlight, reducing the energy available for melting. When that covering disappears, the ice beneath becomes exposed. Snow-cover duration and surface reflectivity are among the processes discussed in research on Switzerland’s 2022 drought. These mechanisms explain why winter conditions matter without assigning snow a separate numerical share of the reported 2026 loss.

The October 1 announcement describes a winter and summer already completed. GLAMOS lists its annual report as covering 2025/2026. Its standard monitoring year, known as the hydrological year, runs from October 1 to September 30—here, October 1, 2025, through September 30, 2026. That calendar brings the preceding winter’s accumulation and the following summer’s melting into the same annual account.

GLAMOS calls the balance between snow gained and snow or ice lost a glacier’s “mass balance.” Its measurement description says observations on selected glaciers are typically collected in April or May and September. The actual field dates can vary; the fixed annual period is distinct from those visits. Spring measurements establish how much accumulated before summer, while the later observations help establish what remained.

The headline percentage concerns ice volume: the amount of ice, rather than simply the area it covers or the distance its lower end has retreated. GLAMOS defines relative annual volume change against the previous year. It describes the combined change across Swiss glaciers, which can have different individual outcomes.

The national loss remained below the record reached in 2022, Huss told Reuters. Yet Aletsch, Switzerland’s largest glacier, experienced its greatest recorded melting, while Tsanfleuron lost more than four metres of average thickness. Those examples show how a severe national year can include a record at one glacier without setting a national record. Reuters

An earlier drought illustrates the water-storage tradeoff. A peer-reviewed study published in January 2026 combined observations and modelling and estimated that 60–80% of glacier melt in 2022 came from net mass loss. Melting supported rivers while drawing down the frozen reserve. That finding concerns 2022; it does not establish water availability for particular communities in 2026.

For water users downstream, current river flows, rainfall, seasonal snow and reservoir records provide the local picture. The national ice-volume loss alone cannot predict a restriction at someone’s tap.