300 Western Glaciers Vanish as Ice Cover Shrinks by a Third

A new study published in the Proceedings of the National Academy of Sciences confirms that more than 300 glaciers have disappeared entirely from the western United States since the mid-20th century. The research team from Portland State University and the U.S. Geological Survey analyzed data from 1,331 Western glaciers. They compared current size and volume figures to historical USGS mapping records collected between 1950 and 1980.

The inventory reveals that the total glacier area in the West has shrunk by 35%. Total volume has decreased by 33% over the same period. In the 1950s, the region held more than 1,450 glaciers. Researchers now calculate that nearly one-quarter of those mid-century ice masses are gone. The study covers six states: California, Colorado, Idaho, Montana, Oregon, and Washington.

Andrew Fountain, a geology professor at Portland State University who led the study, described the findings as tangible evidence of continued climate warming. He noted that the lost volume, if averaged across all remaining glaciers, would equal each one dropping by 38 feet. Geologists define a glacier as an ice mass covering at least 25 acres. This threshold explains why some smaller ice fields no longer qualify as glaciers.

Washington state holds the vast majority of the West’s ice. It contains 89% of the country’s total glacial volume among the lower 48 states. Mount Rainier alone has more glacial cover than all other states combined. Despite this concentration, the Cascade Range glaciers in Washington and Oregon have lost 13% of their volume in recent decades. The Sierra Nevada mountains in California have suffered a more drastic loss of 77% of their glacial volume.

An earlier analysis by the same team focused on 612 federally recognized glaciers. That review found 50 no longer met the size criteria for glaciers. Twenty-five of those were in the Cascade Range and seven were in Oregon. Two federally recognized glaciers in Washington and Wyoming have vanished completely. The new study expands the scope to include non-federally recognized ice masses to provide a fuller picture of regional loss.

Current snowpack levels in the Northwest and the Cascade Range stand at some of the lowest levels since records began in 1985. Fountain explained that smaller glaciers result in less cold water flowing into high alpine streams and riparian habitats. This water serves as a critical source for communities during the hot, dry months of late summer. The region also experienced its warmest fall on record last year, according to National Oceanic and Atmospheric Administration data.