U.S. Glaciers Have Declined Over Last 75 Years

A new study reveals that the contiguous United States has lost a third of its glacial ice volume since the mid-twentieth century.

Updated on Oct. 12, 2026 in Geography

U.S. Glaciers Have Declined Over Last 75 Years

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Researchers have documented a significant reduction in glacial ice across the lower 48 states, finding that 398 glaciers have vanished in the last 75 years. The study indicates that the total area and volume of these glaciers have dropped by approximately 33% since the mid-twentieth century.

Why it matters

The melting of these glaciers is driven by warming temperatures, which leave regional ice formations smaller and less resilient to changing climates. This loss is expected to continue as glaciers adjust to ongoing environmental shifts.

Researchers utilized U.S. Geological Survey inventories alongside satellite imagery to track changes in 1,331 glaciers. Findings show that Sierra Nevada glacial volume has fallen by 77% while the Trinity Alps have lost 88% of their total glacial area.

The players

U.S. Geological Survey

This federal agency provides scientific data on natural resources and landscapes, including the glacier inventories used in this study.

The details

By comparing historical data with modern records from 2013 to 2019, scientists mapped the drastic shrinkage of mountain ice. While most regions showed significant retreat, the North Cascades saw a counterintuitive increase in the number of glaciers, rising from 668 to 706.

The baseline for total United States glacial decline is the mid-twentieth century.
Glacier counts in the Sierra Nevada use the 1970s as a baseline period.
The study used data collected between 2013 and 2019 as its most recent source.
Data from 2020 to 2022 was excluded from the study because it was a period of extreme drought.

The Big Picture

This research builds upon the U.S. Geological Survey glacier inventories to provide a modernized, comprehensive overview of mountain ice. The study marks a significant update to historical data, confirming that glacial recession is an accelerating trend across the Western United States.

The widespread loss of mountain glaciers may lead to significant changes in local water availability and regional ecosystem stability. These shifts will likely influence future agricultural planning and the management of water resources across the Western United States.

The takeaway

The sustained retreat of mountain glaciers serves as a clear indicator of the impacts that warming temperatures have on high-altitude landscapes. Residents in these regions may see further changes to local water cycles as the total volume of glacial ice continues to drop.