Colorado Glaciers Lost Up to 12 Feet of Ice After Record-Low Snow and Heat

Colorado’s remaining glaciers lost ice at a pace that sharply exceeded recent years in 2026, as record-low mountain snow was followed by record summer heat. The Andrews Glacier thinned by more than 12 feet (3.7 meters), while Arapaho Glacier lost nearly 10 feet (3 meters) and Isabelle Glacier about 6.5 feet (2 meters), according to research by Colorado State University glaciologist Dan McGrath.

Those losses were roughly double the glaciers’ thinning rate over the previous five years. In the decade before that, annual thinning measured a foot or less. The contrast points to how quickly conditions in one unusually warm, snow-poor year can affect small, high-elevation ice masses that depend on seasonal snowfall to replace what melts.

McGrath focused on 2026 because the year’s conditions were exceptional. Colorado had its worst snowpack on record, followed by record summer heat. With less fresh snow covering them, the glaciers were left more exposed as temperatures rose. St. Mary’s Glacier, a perennial snowfield popular with hikers and skiers, melted completely in September.

A sharp shift in the pace of ice loss

The latest measurements fit a broader pattern of glacier retreat across mountain ranges. McGrath said the thinning in Colorado resembles changes observed in the Alps, other western U.S. ranges and glaciers worldwide. That consistency matters: it suggests Colorado’s losses reflect a wider response to warmer conditions and reduced snowfall, even as local weather shapes the severity in any given year.

The scale of the change is especially stark at Andrews Glacier, which McGrath said has lost half its ice since 2017. He believes the state’s remaining glaciers could disappear within the next 20 years if the recent pace continues. That estimate is a projection based on observed thinning and the glaciers’ current imbalance with the climate; it is not a fixed deadline for every ice mass.

Mountain glaciers in the contiguous United States are small and scattered across high elevations. They average 0.16 square miles (0.41 square kilometers), or about 100 acres (about 40 hectares). Since the mid-1900s, about one-quarter have disappeared, while those that remain have lost a third of their area and volume, according to a study co-authored by Brian Menounos, an earth sciences professor at the University of Northern British Columbia.

Why the losses matter downstream

Glacier runoff feeds high-alpine and downstream ecosystems across the western United States. As the ice retreats, those areas could become more vulnerable to extreme drought, Menounos said. The immediate effect of a shrinking glacier is not simply less ice on a mountainside: over time, it can also mean less meltwater available to the landscapes and communities connected to that runoff.

Glacier surfaces can become more vulnerable to melting when soot and dust darken the ice, allowing it to absorb more sunlight. Wildfires can contribute to that effect, creating what Menounos described as a “one-two punch” alongside warming and low snowfall. The source material does not quantify how much this process contributed to Colorado’s 2026 losses, so its role in the state’s measurements remains unclear.

There is a long-term path by which glaciers could form again: carbon pollution would need to decline substantially, and temperatures would need to fall enough for snow to accumulate year-round and compress into ice. Menounos said that rebuilding could take several hundred years. The gap between the pace of present losses and the time needed for new ice to form underscores why this year’s measurements carry consequences beyond a single season.

Evidence from other mountain ranges

Conditions in Switzerland offer another measure of how vulnerable alpine ice is to heat and weak winter snowfall. The country’s glaciers lost 5.5% of their ice volume this year, the second-largest percentage drop on record, according to the GLAMOS Swiss glacier monitoring service and the Swiss Academy of Sciences. Switzerland has more glaciers than any other country in the Alps.

In Washington state, researchers with the North Cascade Glacier Climate Project surveyed six glaciers on Mount Baker during their annual summer trip. Director Mauri Pelto said this year’s survey showed the fastest average retreat since 1950. Researchers also recorded the collapse of several large ice caves, which form as warm air moves through retreating glaciers.

Across these locations, the common pressures are higher temperatures and reduced snowfall. The exact outcomes differ by glacier and mountain range, but the comparison helps put Colorado’s annual losses in context: 2026 was an exceptional year locally, while rapid retreat is also evident elsewhere.

Documenting a changing landscape

Harlan Ulmer, a 20-year-old Colorado State University student, has photographed Colorado’s glaciers each year since 2022 and volunteers with McGrath’s research project. He said he never saw the glaciers at their largest, but sees value in recording their changes for future generations.

That record helps researchers compare what they see from one year to the next, particularly when a single season brings unusually little snow and intense heat. The measurements now show an abrupt acceleration: losses that had been measured in inches are, at some sites, being counted in several feet. The next readings will show whether 2026 remains an extreme year or marks a faster pace of decline that persists.