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A little more than 300 glaciers disappeared from the contiguous United States between a mid-20th-century baseline and the inventory reviewed in 2026, according to Portland State University glacier researcher Andrew Fountain. The surviving glaciers also lost 35% of their total area. The count covers six western states—not Alaska or the entire United States—and the reported comparison does not assign one exact endpoint year to every glacier observation.
How many glaciers have disappeared in the American West?
Fountain’s October 2026 account of a review published in the Proceedings of the National Academy of Sciences describes a mid-20th-century inventory of more than 1,450 glaciers across six contiguous western states. Together, those glaciers covered 562 square kilometers (217 square miles). Compared with that baseline, a little more than 300 glaciers have disappeared and total glacier area is down 35%. Fountain wrote, “A little more than 300 glaciers have disappeared, way more than I had anticipated.” Andrew Fountain’s account
The count and area change describe different things. A glacier can shrink substantially while remaining in the inventory; disappearance means it no longer qualifies as a glacier. The 35% figure refers to area, not thickness or glacier count. And the 300-plus figure is a cumulative change over the comparison period, not an annual loss rate.
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Regional warming matters, but local terrain and snow supply help determine which glaciers persist. Rocky Mountain survivors often occupy shaded, sheltered places less exposed to direct sunlight. Avalanches can add snow to these niches, replenishing ice. “The surviving Rocky Mountain glaciers inhabit shaded niches less exposed to direct sunshine and gain additional snow from avalanches,” Fountain wrote. Fountain’s explanation of surviving glaciers
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Washington’s Mount Rainier and Mount Baker glaciers benefit from cooler summers and greater snowfall than some glaciers farther inland. These local advantages do not make them immune to loss; they help explain why change is uneven across mountain ranges.
Where are glaciers thinning fastest?
Fountain’s account identifies the Beartooth-Absaroka Mountains as the fastest-thinning region in the comparison. It reports ice-thickness loss of about 0.5 meters per year there, versus about 0.15 meters per year for glaciers on Mount Rainier and Mount Baker. Fountain’s reported thinning rates
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These are rates of thickness change, not area loss. They cannot be used to calculate how many glaciers disappeared or how quickly a glacier’s footprint is shrinking. The source account does not specify a common observation endpoint for every glacier, so the rates should be understood as reported regional comparisons, not a precise forecast for an individual glacier.
| Region or measure | Reported finding | What it indicates |
|---|---|---|
| Six western states, mid-20th-century baseline | More than 1,450 glaciers; 562 km² (217 mi²) total area | Starting inventory reported by Fountain |
| Contiguous-U.S. inventory comparison | A little more than 300 glaciers disappeared; total area fell 35% | Cumulative count and area change, not an annual rate |
| Beartooth-Absaroka Mountains | About 0.5 m of thickness lost per year | Fastest thinning reported in Fountain’s account |
| Mount Rainier and Mount Baker | About 0.15 m of thickness lost per year | Slower thinning reported for these Washington glaciers |
| Glacier size | Average area about 0.25 km²; Mount Rainier’s largest glacier 11.24 km² | Illustrates the wide difference between a typical glacier and a large one |
The size figures are also reported in Fountain’s 2026 account. They help put the total area in context: a large glacier such as the one cited on Rainier is not representative of the many much smaller glaciers in the inventory. Fountain’s inventory and size figures
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What happens to streams and ecosystems as glaciers disappear?
Glacier melt helps sustain cool alpine streams in late summer, after seasonal snow has melted. That water supports headwater ecosystems during a period when other sources of meltwater may be dwindling. In Washington, glaciers also contribute water used for hydropower. The importance varies by watershed; the inventory’s glacier count alone does not quantify how much water a particular community or stream receives. Fountain’s account of glacier-fed waters and hazards
Water from ice glaciers and rock glaciers also differs in composition. A U.S. Geological Survey field study sampled 25 alpine ice glaciers and 24 rock glaciers across three western mountain regions over three summers. The USGS reported that meltwater chemistry varies between glacier types and regions, with implications for headwater chemistry and biological activity. This is evidence that glacier loss can affect more than the volume or timing of water: it can alter the chemical conditions of mountain streams. U.S. Geological Survey summary of the field study
Can retreating glaciers also increase hazards?
As glaciers retreat, the loose deposits left behind—moraines—can be undercut by water on volcanic mountains. That can trigger debris flows, fast-moving mixtures of water, sediment, and rock. Fountain cites events on Mount Hood and Mount Rainier in 2006 and expects retreat-related debris flows to become more common. The account does not provide a quantified forecast or event-frequency estimate, so this is a stated expectation rather than a measured rate of increase. Fountain’s discussion of debris-flow hazards
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The inventory comparison documents substantial glacier loss across the contiguous West, but its headline count should not be stretched beyond its scope. It is a six-state account, not a count for Alaska or all U.S. glaciers. The comparison is framed as extending from the mid-20th century, without one exact endpoint year for every observation. The figures above are reported in Fountain’s 2026 account of the PNAS review; the DOI identified for the paper is 10.1073/pnas.2600941123, but the full paper’s methods and original tables are not available in that account.
A separate model result says Olympic Peninsula glaciers may mostly disappear by 2070. That is a projection for a particular region, not part of the observed inventory count and not a forecast for every glacier in the West. Olympic Peninsula projection
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