How do we know glaciers are shrinking?

Repeat photography and aerial / satellite photo analysis provide evidence of glacier loss in terms of shape and area. The USGS Benchmark Glacier project has collected mass balance data on a network of glaciers in Alaska, Washington, and Montana for decades, quantifying trends of mass loss at all sites. Extensive field data collection at these sites includes twice yearly visits to measure seasonal change of snow/ice at ablation stakes and snow-pit analysis to measure snow density for extrapolating ice gain or loss across the glacier surface.

Emerging technologies, complemented by the availability of satellite imagery, allow USGS scientists to create Digital Elevation Models (DEMs) that provide data on the elevation of glacier ice.  By comparing DEMS from different times, scientists calculate ice volume change on a regional scale, broadening the understanding of ice loss and its link to climate.  

Learn more: USGS Water Science School: Glaciers and Icecaps 

Related Content

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Date published: August 28, 1998

Alaskan Glaciers Yield Massive Floods

Torrents of meltwater are unleashed suddenly from the margins of the great moving sheets of snow and ice, known as glaciers. In Alaska, these pulses of activity, called "outburst floods," are usually caused by the failure of ice dams that restrain the meltwater of glacial margin lakes.

Attribution: Region 11: Alaska
Filter Total Items: 24
This is a glacier animation for Glacier National Park.
April 5, 2016

Glacier Animation

The simulation below reflects the predicted exponential rise in atmospheric CO2 concentrations, a 2xCO2 "global warming" scenario, with a concurrent warming of 2-3 degrees centigrade (4-5 degrees Fahrenheit) by the year 2050. In addition it assumes that precipitation, primarily in the form of rain, will increase over the same time period about 10 percent (based on the

Mapping the glacier's edge in Glacier National Park.
April 5, 2016

Mapping the glacier's edge in Glacier National Park.

Mapping the glacier's edge in Glacier National Park.

March 13, 2012

Climate Connections: Questions from Glacier National Park, MT (Ep 4)

America has questions about climate change, and the USGS has real answers. In this episode of Climate Connections, USGS scientists answer questions gathered from the beautiful Glacier National Park in Montana. Questions include:


  • When I come back in ten years, what will I see in Glacier National Park?
  • How is climate change impacting the
August 25, 2011

PubTalk 8/2011 — Through the Lens of Time

Repeat Photography in an Era of Global Change

by Robert Webb, Hydrologist

  • Repeat photography remains an essential and cost-effective technique for scientists and researchers working to track and study changing environmental conditions
  • Scientists worldwide are exploring methods to apply this technique in various
Image: Getting the Shot, Grinnell Glacier, Glacier National Park.
January 1, 2010

Getting the Shot, Grinnell Glacier, Glacier National Park.

USGS scientist shoots a repeat photograph of Grinnell Glacier in Glacier National Park to illustrate glacial recession due to impacts of climate change.

*note – logo on scientists hat is logo from USGS Northern Rocky Mountain Science Center, not private. 

Attribution: Land Resources
video thumbnail: USGS Public Lecture Series: Baked Alaska--What's Happening to the Glaciers in Alaska?
September 1, 2009

USGS Public Lecture Series: Baked Alaska--What's Happening to the Glaciers in Alaska?

Glaciers are Earth's largest reservoir of freshwater. As they change, so does global sea level. Alaska has one of the largest accumulations of glaciers anywhere on Earth outside of the Polar regions. For most of the past half century, Alaska has experienced a significant increase in temperature that has profoundly impacted its glaciers. Join USGS scientist Dr. Bruce F.

Attribution: Region 11: Alaska
USGS CoreCast
August 6, 2009

The Cold Facts About Melting Glaciers

Most glaciers in Washington and Alaska are dramatically shrinking in response to a warming climate.

USGS scientist Edward Josberger discusses research from the past 50 years to measure changes in the mass (length and thickness) of three glaciers in Alaska and Washington. These are the longest such records in North America and among the longest in the world.