Sizing up the Earth's Glaciers
In the Alps, glaciers are retreating and disappearing every year, much to the dismay of mountain climbers, tourist agencies, and environmental researchers.

South Cascade Glacier in the Washington Cascade Mountains, in 1928, 1979, and 2000 (Images courtesy of the National Snow and Ice Data Center)
By Evelyn Yohe
Visit the world’s high mountain ranges and you’ll probably see less ice and snow today than you would have a few decades ago. More than 110 glaciers have disappeared from Montana’s Glacier National Park over the past 150 years, and researchers estimate that the park’s remaining 37 glaciers may be gone in another 25 years. Half a world away on the African equator, Hemingway’s snows of Kilimanjaro are steadily melting and could completely disappear in the next 20 years. And in the Alps, glaciers are retreating and disappearing every year, much to the dismay of mountain climbers, tourist agencies, and environmental researchers.
“Receding and wasting glaciers are a telltale sign of global climate change,” said Jeff Kargel, head of the Global Land Ice Measurements from Space (GLIMS) Coordination Center at the United States Geological Survey (USGS) in Flagstaff, Arizona. Kargel is part of a research team that’s developing an inventory of the world’s glaciers, combining current information on size and movement with historical data, maps, and photos.
In response to climate fluctuations, glaciers grow and shrink in length, width, and depth. Because glaciers are sensitive to the temperature and precipitation changes that accompany climate change, the rate of their growth or decline can serve as an indicator of regional and global climate change. Tracking and comparing recent and historical changes in the world’s glaciers can help researchers understand global warming and its causes (such as natural fluctuations and human activities). Glacial changes can also have a more immediate impact on communities that rely on glaciers for their water supply, or on regions susceptible to floods, avalanches, or landslides triggered by abrupt glacial melt.

This ASTER image shows the lakes left behind by retreating glaciers in the Bhutan-Himalaya. (Image courtesy of Jeffrey Kargel, USGS/NASA JPL/AGU)
The GLIMS team uses high-resolution satellite images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument and the Landsat Enhanced Thematic Mapper Plus (ETM+), archived at NASA's Land Processes Distributed Active Archive Center (LP DAAC), to track the size and movement of glaciers. For the first time, scientists will be able to assess and track glacial change on a global scale through a worldwide database of glacier information.

This ASTER image, acquired on July 23, 2001, shows Aletsch Glacier, the largest glacier of Europe. (Image by NASA Earth Observatory Team, based on data provided by the ASTER Science Team)
About three-quarters of the Earth’s fresh water is held in ice sheets and mountain glaciers, so recognizing glacial changes is crucial to monitoring water supplies. “Glaciers serve as a natural regulator of regional water supplies,” said Kargel. During periods of warm weather and intense sunlight, such as during dry seasons and droughts, glaciers melt vigorously and provide a water source for the surrounding ecosystems and communities. Conversely, during cold, rainy seasons, glaciers produce less meltwater. “Glacier changes, especially recent melting, can affect agriculture, drinking water supplies, hydroelectric power, transportation, tourism, coastlines, and ecological habitats,” he added.

This composite ASTER image shows how the Gangotri Glacier terminus has retracted since 1780. Contour lines are approximate. (Image by Jesse Allen, NASA Earth Observatory; based on data provided by the ASTER Science Team; glacier retreat boundaries courtesy the Land Processes Distributed Active Archive Center)
Excessive glacial melt can also result in increased hazards or disasters for communities living near glaciers. “Glaciers don’t always behave nicely. They’re a type of natural reservoir with a temper, in some cases. Some glaciers have a nasty habit of storing up large amounts of water and then releasing it suddenly in a massive melt or calving episode, which may involve floods, landslides, or avalanches,” said Kargel.
As settlements, farming, and tourism extend toward the edges of glaciated regions, melting glaciers and the avalanches and floods that often accompany rapid melt increasingly threaten lives and infrastructure in mountain regions. The ASTER images acquired for the GLIMS project allow researchers to recognize and track changes in glacial hazard indicators such as crevasses, avalanche and debris-flow traces, and glacial lakes.
While current melting trends can’t be slowed or reversed, the information collected through the GLIMS project will enable researchers to better understand the relationship between climate and glaciers, and to better predict areas of future glacier changes.
The ASTER images of each glacier, along with the data collected and analyzed by the GLIMS team, are stored in a large database jointly developed by the USGS in Flagstaff and NASA's National Snow and Ice Data Center (NSIDC) DAAC in Boulder, Colorado. Previous glacier databases stored information such as location, length, orientation, type, and altitude for one point near the center of each glacier. “The GLIMS database will store detailed information for the entire outline of each glacier, providing more complete spatial data,” said Bruce Raup, technical lead for the GLIMS project at NSIDC DAAC. “As the data become available in the database, users will be able to do online searches and see the resulting data in multiple formats, including views of glacier extent and elevation superimposed on ASTER images.”

Left: This 1929 photograph shows Taku Glacier as it winds through the mountains of southeastern Alaska, calving small icebergs into Taku Inlet. (Image courtesy of U.S. Navy) Right: This photo illustrates outlet glaciers with different flow rates in the inner Royal Society Fiord, Northeast Baffin Island, Canada. Although these adjacent glaciers come from the same ice cap, they have different surface character because they are flowing at different rates. (Image by Douglas Hodgson, Copyright © Terrain Sciences Division, Geological Survey of Canada)
Although the GLIMS project is still in a formative stage, the yearly satellite data being compiled and stored with historical data from the last three to five decades will enable scientists to track worldwide glacier changes and the effects of such change on surrounding communities and habitats. “I think we’ll have some interesting data that will be publicly accessible within the coming year,” said Raup. “It won’t be global coverage yet, but there should be some good snapshots of glacier health within a few regions. This is a fascinating time to study and inventory the world’s glaciers because of the recent dramatic changes.”
“I think a hundred years from now, the GLIMS effort to study the world’s glaciers will still be going strong,” said Kargel. “There will still be glaciers to study, although far fewer than there are today. But GLIMS will eventually consist of well over a century’s worth of glacial data.”
References
Global Land Ice Measurements from Space (GLIMS). Accessed February 6, 2004.
For more information
NASA Land Processes Distributed Active Archive Center (LP DAAC)
NASA National Snow and Ice Data Center DAAC (NSIDC DAAC)
About the remote sensing data used | ||
---|---|---|
Satellite | Terra |
|
Sensor | Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) |
|
Parameter | inventory of Earth's glaciers |
|
DAACs |
NASA Land Processes Distributed Active Archive Center (LP DAAC) NASA National Snow and Ice Data Center DAAC (NSIDC DAAC) |
Page Last Updated: Jul 28, 2020 at 11:06 AM EDT