How Do Glaciers Change The Surface Of The Earth

Sizing Up the Earth's Glaciers by Evelyne Yohe

Visit the world'southward loftier mountain ranges and you'll probably see less ice and snow today than you would accept a few decades ago. More than 110 glaciers have disappeared from Montana'due south Glacier National Park over the by 150 years, and researchers estimate that the park'southward remaining 37 glaciers may exist gone in another 25 years. Half a world abroad on the African equator, Hemingway's snows of Kilimanjaro are steadily melting and could completely disappear in the side by side 20 years. And in the Alps, glaciers are retreating and disappearing every year, much to the dismay of mountain climbers, tourist agencies, and ecology researchers.

"Receding and wasting glaciers are a telltale sign of global climatic change," said Jeff Kargel, head of the Global Country Ice Measurements from Space (GLIMS) Coordination Center at the United States Geological Survey (USGS) in Flagstaff, Arizona. Kargel is role of a research squad 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 back-trail climatic change, the charge per unit of their growth or refuse can serve as an indicator of regional and global climate change. Tracking and comparing recent and historical changes in the globe's glaciers tin help researchers empathise global warming and its causes (such as natural fluctuations and human being activities). Glacial changes can also take a more immediate impact on communities that rely on glaciers for their h2o supply, or on regions susceptible to floods, avalanches, or landslides triggered by abrupt glacial cook.

June 22, 2004

Championship graphic image: South Cascade Glacier in the Washington Cascade Mountains, in 1928, 1979, and 2000 (Images courtesy of the National Snowfall and Ice Data Center)

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Scientists rails glacial modify by measuring private glaciers and comparison their size over time with records of the local and regional climate. Only measuring every major glacier on World would be a monumental task. Approximately 160,000 glaciers occupy the Globe'southward polar regions and loftier mountain environments, and sending a squad to each one every year would be costly and difficult to coordinate. In add-on, although a few inquiry teams travel to a few glaciers each year to measure water ice depth, size, movement, and h2o content, the data from individual glaciers don't necessarily reveal how other glaciers in the same region—much less in other parts of the world—are changing. Even glaciers within the same region tin react differently to environmental changes. For instance, while nearly glaciers in Glacier National Park are retreating, some are advancing.

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 the Country Processes Distributed Active Annal Center (LP DAAC), to track the size and motion of glaciers. For the first time, scientists will exist able to appraise and track glacial alter on a global scale through a worldwide database of glacier information.

This ASTER image shows the lakes left behind past retreating glaciers in the Bhutan-Himalaya. (Paradigm courtesy of Jeffrey Kargel, USGS/NASA JPL/AGU) Click hither for more data.

More than 100 investigators in 24 countries are helping to build the GLIMS database. "These investigators collect and analyze satellite images of the glaciers in their own region, such every bit the Alps or the Andes, and so send their analyses and results to the Coordination Center for inclusion in the GLIMS database," Kargel explained. The researchers also compare the satellite images with historical maps and information to determine a glacier's advance or retreat over the past few decades. Satellite imagery can assist reveal short- or long-term trends in glacier activeness that could impact water supplies or crusade glacial hazards.

Almost three-quarters of the Globe'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 condition and intense sunlight, such as during dry seasons and droughts, glaciers melt vigorously and provide a h2o source for the surrounding ecosystems and communities. Conversely, during common cold, rainy seasons, glaciers produce less meltwater. "Glacier changes, particularly recent melting, tin affect agriculture, drinking water supplies, hydroelectric ability, transportation, tourism, coastlines, and ecological habitats," he added.

This ASTER image, acquired on July 23, 2001, shows Aletsch Glacier, the largest glacier of Europe. (Image by Globe Observatory Team, based on data provided past the ASTER Science Squad)

Retreat of the Gangotri Glacier

In areas with very large glaciers, increased melting could result in temporary increases in meltwater available for human use. But as the world'due south glaciers keep to melt and shrink, over time at that place volition exist less water to sustain the communities that have come to depend on that meltwater. In Kazakhstan, for instance, glaciers feed many of the rivers used for agricultural irrigation, and the recent glacial retreat in that region is now compromising the area's water supply. "It'due south kind of like a bank business relationship—when y'all've withdrawn all the water, there isn't any more," said Kargel.

Excessive glacial melt can also event in increased hazards or disasters for communities living about glaciers. "Glaciers don't always acquit nicely. They're a blazon of natural reservoir with a temper, in some cases. Some glaciers have a nasty habit of storing up big amounts of water and so releasing information technology suddenly in a massive cook 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 caused for the GLIMS project permit researchers to recognize and track changes in glacial hazard indicators such as crevasses, avalanche and debris-catamenia traces, and glacial lakes.

While electric current melting trends can't exist slowed or reversed, the information nerveless through the GLIMS project will enable researchers to amend understand the relationship betwixt climate and glaciers, and to better predict areas of hereafter glacier changes.

The ASTER images of each glacier, along with the data collected and analyzed by the GLIMS squad, are stored in a big database jointly developed past the USGS in Flagstaff and the National Snow and Ice Data Centre (NSIDC) in Boulder, Colorado. Previous glacier databases stored information such as location, length, orientation, blazon, and altitude for i bespeak near the middle of each glacier. "The GLIMS database will store detailed information for the unabridged outline of each glacier, providing more complete spatial data," said Bruce Raup, technical pb for the GLIMS project at NSIDC. "As the information get available in the database, users volition be able to do online searches and run into the resulting data in multiple formats, including views of glacier extent and elevation superimposed on ASTER images."

This composite ASTER image shows how the Gangotri Glacier terminus has retracted since 1780. Profile lines are estimate. (Image by Jesse Allen, Earth Observatory; based on information provided by the ASTER Scientific discipline Team; glacier retreat boundaries courtesy the State Processes Distributed Active Archive Center)

Ane of the challenges of the GLIMS glacier inventory is the authentic identification of each glacier. "While it may seem piece of cake to define what a glacier is, it tin be quite difficult to identify individual glaciers in highly glacierized areas where the glaciers branch or run together," said Raup. Also, contempo glacial melt has resulted in some dramatic glacial changes; for example, some large Y-shaped glaciers that are numbered and described in the older World Glacier Inventory take recently shrunk into ii separate water ice masses. "We're currently creating protocols that enable u.s. to describe accurate boundaries around individual glaciers and properly classify glaciers that previously were part of other glaciers," Raup added. This process will help identify the extent to which large, glacierized areas take become smaller and more than fragmented.

Although the GLIMS project is still in a determinative phase, the yearly satellite data being compiled and stored with historical data from the last three to five decades will enable scientists to rails worldwide glacier changes and the furnishings of such change on surrounding communities and habitats. "I call back nosotros'll have some interesting information that will be publicly accessible within the coming year," said Raup. "It won't be global coverage yet, only there should be some skillful snapshots of glacier wellness within a few regions. This is a fascinating time to report and inventory the globe's glaciers because of the recent dramatic changes."

"I think a hundred years from at present, the GLIMS effort to study the earth's glaciers will withal exist going potent," said Kargel. "There will still be glaciers to study, although far fewer than there are today. But GLIMS volition somewhen consist of well over a century's worth of glacial data."

Left: This 1929 photograph shows Taku Glacier equally it winds through the mountains of southeastern Alaska, calving pocket-sized icebergs into Taku Inlet. (Paradigm courtesy of U.Due south. Navy)
Right: This photo illustrates outlet glaciers with unlike period rates in the inner Royal Society Fiord, Northeast Baffin Island, Canada. Although these adjacent glaciers come up 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)