Glacial Loss: West loses a third of ice cover since 1950

The total volume of glacial ice in the western United States has declined by 33% since the mid-20th century, a figure that translates to an average drop of 38 feet in height for every remaining glacier. This new data comes from the first comprehensive inventory of western glacial area and volume, compiled by researchers at Portland State University and the U.S. Geological Survey.

The study, published in the Proceedings of the National Academy of Sciences, marks a shift in how scientists track these features. While earlier analyses focused on the 612 federally recognized glaciers in seven states, this new work examines 1,331 glaciers. The team compared current size and volume data against historical USGS mapping records from 1950 to 1980.

In the 1950s, the region contained more than 1,450 glaciers. The new inventory shows that nearly one-quarter of those mid-century glaciers no longer exist. Andrew Fountain, a geology professor at Portland State University who led the study, noted that 50 glaciers are no longer classified as glaciers because they have fallen below the minimum size threshold of 25 acres. Two federally recognized glaciers in Washington and Wyoming have disappeared entirely.

The loss of ice is not evenly distributed across the region. Washington state holds 89% of the total glacial volume in the lower 48 states. The glacial cover on Mount Rainier alone exceeds the combined cover of all other states. However, the Sierra Nevada mountains in California have suffered the sharpest decline, losing 77% of their glacial volume.

Fountain described the losses as tangible evidence of continued climate warming. Global average temperatures have risen 2 degrees Fahrenheit since the 1850s, driven by greenhouse gas emissions from burning fossil fuels. The study indicates that glaciers in the Cascade Range of Washington and Oregon have lost 13% of their volume in recent decades.

The reduction in ice mass affects water availability for communities that rely on snowmelt. Snowpack levels in the Northwest and Cascade Range are among the lowest recorded since 1985. Fountain explained that smaller glaciers result in less cold water flowing into high alpine streams and riparian habitats during the hot, dry late-summer months.

National Oceanic and Atmospheric Administration data shows the region experienced its warmest fall on record in the previous year. The inventory confirms that six western states, including Oregon, have lost more than one-third of their glacial cover since 1950.