Monitoring Glaciers

This section highlights why monitoring glaciers is important. For starters, monitoring glaciers gives scientists one of the most significant indicators in determining whether observed climate change is regional or global. Another reason is that resent-day glaciers and the deposits from more extensive glaciation in the past have considerable economic importance in many areas. Knowledge gained from monitoring glaciers can be used by governments to make long-range plans to better cope with the economic impacts of climate change. Click on of the topics to the left to learn more.


Benefits of Glaciers

Glaciers provide many benefits to us as humans, as well as to other species. If we realize what benefits glaciers provide, we may then recognize why they are important. Moreover, we may begin to understand why monitoring glaciers is important.

Reservoirs for Water

Glaciers are an important water resource of Alaska, the western United States, and throughout the world. For example, a number of the world’s desert regions, such as north-western China or the wine-growing area of Mendoza in Argentina, receive waters from adjacent mountain ranges. Much of this water is glacial runoff—perhaps not a large contribution but one of the greatest. Glaciers provide water when it is needed most, during hot, dry seasons and years. Glacial deposits also act as reservoirs for groundwater. Moraines are generally poor reservoirs because they contain large amounts of clay and are poorly sorted. Outwash, on the other hand, typically consists of sand and gravel and has been reworked by streams. This generally results in a sedimentary deposit that has had most of the clay flushed downstream. Wells constructed in outwash deposits can be very productive.

Commercial Value of Glacier Ice

Glacier ice itself has proved to be a profitable export commodity for some countries. Ice exports were a feature of the Norwegian economy before refrigerators were invented. Nowadays, people in Japan are able to cool their drinks with expensive ice hacked from an Alaskan glacier, and melted glacier ice is sold as an unusually pure mineral water in Iceland. Even in Peru, people make a living out of collecting glacier ice, grinding it up, mixing flavors with it, and then selling it at the markets as a local version of snow cones.

Electric Power Generation

In many parts of the world, meltwater from glaciers enhances electric power generation. In Switzerland, for example, hydro-electric power generation is big business. During the winter, half of Switzerland’s energy production if generated by water released from reservoirs. The Massa hydro-electric power station near Brig is owned by the Swiss Railways. This station runs almost entirely on meltwater from the Glosser Aletschgletscher, the largest glacier in the Alps.


Apart from the attractive scenery, which is always a benefit, glaciers are recreational resources. They are favored by skiers, mountaineers, and mountain lovers. In areas where glaciers are relatively crevasse-free, glaciers provide opportunities for skiing even in July and August. Glaciers are tourist attractions all over the world. Large vehicles with snow tracks transport visitors around the Athabasca Glacier in the Rocky Mountains of Canada. Scenic overflights with glacier landings are major attractions in the Mount Cook region of New Zealand. Tourists who take part in boat excursions to the calving front of the Columbia Glacier in Alaska are often offered a unique drink: a Martini cooled by ice from a calving glacier.

Habitat for Species

The increase or decrease in glacier area impacts high-mountain and high-latitude ecosystems. Glaciers provide habitat for many interesting species. Several new species of ice worms have been discovered during recent glacial studies in the North Cascades. Glacier retreat affects aquatic ecosystems, primarily with changes in base streamflow and temperatures. Glacial retreat also impacts wetlands, which provide habitat to plant and animal species, many of which are Threatened and Endangered. Due to glacial retreat, increased sediment is provided to wetlands and small lakes may form, providing new habitat. Glacier forelands newly exposed in front of receding glaciers provide excellent natural laboratories to study plant succession and soil development.

Hazards of Glaciers

The benefits of glaciers far outweigh any disadvantages; nevertheless, natural hazards created by glaciers are another important reason for monitoring them. If glaciers are monitored, we will begin to understand glacier “behavior” better and be better placed to avert future catastrophes.


Remember the Titanic? Glaciers pose dangers to ocean transportation and shipping, as well as offshore oil installations. The glaciers on the west side of Greenland produce a large number of icebergs that drift south into shipping lanes of the North Atlantic. Some of Greenland’s icebergs have been known to travel as far south as Delaware before completely melting. Antarctica also produces icebergs from its many ice shelves. Some Antarctic icebergs exceed the area of Rhode Island.


Surging glaciers suddenly and dramatically accelerate, advancing several miles in a few months and traveling many times their normal speeds. For example, the Hubbard Glacier in southern Alaska periodically surges and threatens to block the Russell Fjord. Hubbard Glacier most recently blocked the entrance to Russell Fiord in May 1986, and threatened to do so in June 2002. When an effective ice dam forms and remains stable, Russell Fjord fills with fresh water. In such a scenario, as in 1986, marine animals became trapped, and eventually perished, in water that becomes less and less salty from the glacier’s fresh water and increasingly murky from glacial sediment. As water levels rose, birds were driven from their nests, and many eggs and chicks were destroyed.

Water level rises until one of two things happens. Either the ice dam fails or the lake fills until it reaches an ancient spillway at the south end of Russell Fjord. During the 1986 closure, fresh water flowing into the fjord raised the level of the lake 84 feet before the ice dam failed, which spared the nearby village of Yukutat.

Outburst Floods

Catastrophic outburst floods result from the failure of ice-dammed lakes. In general, this happens where an advancing glacier moves across, or partway up, a river valley, blocking the drainage. Smaller lakes can also be impounded within tributary canyons along the lateral margins of large valley glaciers.

Draining of glacier-dammed lakes occurs either through or over a glacier dam. When an outlet stream overtops the ice dam, erosion occurs so rapidly that destruction of the dam and flooding are almost assured. Similar trouble arises if the lake gets so deep that the dam floats loose from its footings or if lake water, enhanced by water pressure, melts open a hole in the dam. In addition, heat sources from subglacial volcanic or geothermal activity below a glacier can cause local melting at a glacier’s base and sometimes create holes penetrating to the surface. Meltwater accumulating at these spots episodically breaks out from under the ice and floods the adjoining outwash plain.

Outburst floods can result in dense, viscous debris flows. The major hazard of debris flows is from burial or impact. People, animals, and buildings can be buried, smashed, or carried away.

Ice Avalanches

The threat of ice avalanches is apparent in densely populated mountain ranges with glaciers, such as the Alps. Ice avalanches may have volumes of millions of cubic yards and have covered whole villages in the past. A major problem with predicting ice avalanches is that, despite their spectacular effects, they are relatively rare, much rarer than snow avalanches. Glaciologists have tried to find ways of predicting the ice volume to be released in avalanches, the “run-out distance,” and the time of the event. It is now known that the ice in the unstable part of a glacier accelerates drastically prior to break-off, usually (but unfortunately not always) creating fresh crevasses. In practice it is difficult to monitor these developments because they occur most frequently at high altitudes.

Further research on ice avalanches is essential because mountain regions like the Alps are increasingly being used for recreation, with the establishment of ski resorts and transport routes, and for the generation of hydro-electric power.

Sea Level Rise

Most of the world’s glacier ice is held in two large ice sheets, Antarctica and Greenland, which together contain an estimated 97% of all the glacier ice and 77% of the planet’s freshwater supply. If all the present glacier ice were to melt from Antarctica and Greenland, the oceans would rise about 260 feet and inundate most of the coastal cities of the world. A rise in sea level would alter the position and morphology of coastlines, causing coastal flooding and waterlogging of soils. Sea level rise would also create or destroy coastal wetlands and salt marshes and induce salt-water intrusion into aquifers, leading to salinization of groundwater. Coastal ecosystems are bound to be affected as well, for example, by increased salt stress on plants. It is estimated that 70% of the world’s sandy beaches would be affected by coastal erosion induced by sea level rise.


Indicators of Climate Change

Because variations in climate cause glaciers to advance and retreat, glaciers can serve as excellent indicators of climate change. Glaciers are sensitive to climate changes of various magnitudes and different time scales. In addition, their widespread geographic distribution makes them suitable for establishing proxy data and for evaluating the nature of global climate fluctuations.

Glaciers tend to “average out” the short term meteorological variations and reflect longer term variations that take place over several decades or centuries. The remarkable signal characteristics of changes in glacier length, for example, are readily apparent by looking at cumulative values and different size categories. Cirque and other small glaciers reflect yearly changes in climate and mass balance almost without any delay. Mountain glaciers dynamically react to decadal variations in climatic and mass balance forcing with enhanced amplitudes after a delay of several years. The largest valley glaciers give strong and most efficiently smoothed signals of secular trends with a delay of several decades. Large ice sheets as in Greenland and Antarctica have even greater response times, probably over several millennia (thousands of years) or tens of millennia.


Libraries of Atmospheric History

Scientists widely recognize ice sheets and ice caps as libraries of atmospheric history from which past climatic and environmental conditions can be extracted. These large glaciers contain ice that dates back millennia to past ice ages. Reliable meteorological observations for climate reconstruction are limited or absent prior to A.D. 1850; therefore, valuable and unique information is trapped in the snow that piles up each year in the accumulation area of a glacier. Ice cores from accumulation areas provide information about the fluctuations of important atmospheric trace gases like carbon dioxide and methane, which are trapped in air bubbles in the ice. Moreover, measurements of oxygen isotopes in the ice can tell us the air temperature when the snow accumulated on the glacier’s surface.

Such information about Earth’s past climate can help us predict the direction and magnitude of future climate changes. By studying the response and changes in glaciers, we can better understand—and anticipate - the range of past and possible future climate changes.


Why Monitoring is Important

The benefits and hazards of glaciers provide us with reasons for why monitoring glaciers is important.

Reservoirs for Water

Glaciers are natural reservoirs of freshwater, and monitoring glaciers is important for assessing and predicting the impacts of glacial retreat on water resources in mountainous areas.

Commercial Value of Glacier Ice, Electric Power Generation, Tourism, and Sea Level Rise

The information gained from monitoring programs can be used by governments and individuals to make long-range plans to better cope with economic impacts of the loss of glaciers as valuable commodities and the loss of coastal settlements and resources due to sea level rise.

Habitat for Species

The increase or decrease in glacier area impacts high-mountain and high-latitude ecosystems. A diversity of species and populations constitutes the world’s available gene pool, which is an important and irreplaceable resource. Monitoring glaciers can provide data to land managers, for example in national parks, for making decisions about protecting rare species that live in glaciers. Furthermore, monitoring will provide land managers with information regarding new and changing habitats created by glacial retreat.


Dangerous glaciers impinge directly on the lives of people in mountain regions, and some have been responsible for huge loss of life. We need to understand glaciers better if catastrophes are to be averted.


Features Monitored

There are many different aspects of a glacier that might be monitored. Below is a list of some of the more common features monitored.

Areal Extent of Glaciers

Direct observations of glaciers are often difficult because they exist in cold, polar regions or high mountain areas that are inaccessible or inhospitable to humans. Furthermore, ice sheets and ice caps are so huge and change so slowly that repeat measurements are needed over large areas and long periods of time. Until the launches in 1972, 1975, 1978, and 1982 of the Landsat series of spacecrafts, glaciologists had no accurate means of measuring the areal extent of glacier ice on Earth. Satellite images provide means for delineating the areal extent of ice sheets and caps, and for determining the position of the termini of valley, outlet, or tidal glaciers for the entire globe. NASA satellite missions will also measure ice sheet elevations, changes in elevation through time, approximate sea ice thicknesses, and global sea level.

Scientific understanding of glaciers owes much to the ability of remote sensing systems to extend human observations in time and space. This ability is important because understanding the worldwide extent, timing, and relative magnitude of glaciation is significant for understanding the mechanism responsible for abrupt climate change. [Provide link to USGS Landsat images and NASA ICESat program on the Web]

Glaciers at 65° North Latitude

According to Milankovitch and other 20th century theoretical climatologists, the glaciers in the area around 65° N latitude are especially sensitive to astronomical variations in Earth’s orbital cycles. In the Northern Hemisphere, glaciers on Baffin Island, Canada; in the Alaska Range, Alaska; in the southern tip of Greenland; in Iceland; and in Norway are at the right locations. The glaciers in Iceland, as with some of these other areas, are important as long-term indicators of climate change because of their latitudinal location. In addition, these glaciers are apparently just large enough not to be affected by short-term climatic variations, yet are small enough and dynamic enough to respond to changes caused by climatic variations over several decades.

Mass Balance

Mass balance is the difference between annual snow and ice accumulation and snow and ice ablation. It can be represented as an average thickness added to or lost from a glacier for a given year. It is the most sensitive annual glacier climate indicator. Mass balance is evaluated by measuring the addition and loss of snow and ice mass at points on a glacier’s surface and extrapolating the point data to the whole glacier surface. Ablation is measured by emplacing stakes in the glacier. As the glacier surface melts that amount of the stake emerging from the glacier is measured. The total melt at each stake by the end of the melt season is the net ablation. Most of the stakes must be replaced during the summer. Accumulation is measured by either probing or ice and snow stratigraphy in crevasses. Analyzing crevasse layering is similar to reading the widths of tree rings.

Glacier Length Change

Change in glacier length is one of the variables used to evaluate the effect of climate change. After a certain reaction time, following changes in mass balance, the length of a glacier will start changing and finally reach a new equilibrium. This means that, for a given change in mass balance, the length change is a function of a glacier’s original length. Furthermore, the change in mass balance can be quantitatively inferred from the easily observed length change. The extreme clarity of this signal makes it possible to apply very simple observational methods, for instance, repeated tape-line measurements from a fixed location beyond the terminus. This, in turn, enables the cooperation of numerous non-specialists with long-term measurements at hundreds of glacier snouts throughout the world.


Glaciers are natural reservoirs that store water as ice instead of using a dam. Most significantly, glaciers yield the most water during the driest period, i.e., late summer, when it is often needed most. Glacier runoff is a combination of melt rates and glacier area. Melt rates are dependent on temperature. As temperatures increase (regionally and globally) and glaciers retreat, the size of the reservoir shrinks, and so does the available runoff. Even a small area of glacier cover is important to total basin runoff. In Stehekin Basin in the North Cascades, for example, the glaciated area is only 3.1% of the total basin, but the glaciers provide 35-40% of late summer runoff. The observed changes in glacier and alpine runoff make it apparent that we can no longer intelligently manage water resources without considering the changes in glacier runoff.

Bed Topography

Glacier-bed topography, a one-time measurement, is important for determining absolute volume changes in glaciers. It is also a significant parameter for predicting glacier movement, estimating the hydraulics of basal water flow, and modeling glacier dynamics. Bed topography can be determined by using ice radar.

Rate of Ice Movement

Rate of ice movement links mass balance with glacier geometry—area, terminus position, and surface elevation. Ice movement is detected by repeated surveying of targets on a glacier or by photogrammetric analysis of natural (crevasse) or artificial targets on a glacier. For a long-term monitoring program, where the mass and volume of a glacier are expected to change, a coincident data set of flow information is useful for determining the dynamic response of glaciers to changes in mass input.


Monitoring Glaciers in National Parks

Glacier-monitoring efforts in national parks provide valuable information to park managers and interpreters, as well as to the scientific community at large, about the effects of regional and global climate change. Click on a park below to find out what kinds of information monitoring programs in parks are producing.

Monitoring in Glacier National Park

Past published reports, dating back to 1914, and anecdotal evidence prior to that, show that the glaciers of Glacier National Park are excellent barometers of climate change. In recent years, researchers have compiled all existing information on all glaciers at Glacier National Park and have added measurements of glacial extent for the period 1979 to present. Most past efforts focused on only one or a few well-studied glaciers; recent studies have found and incorporated previously unused information into a more extensive picture of glacier activity in the park. Researchers mapped the area of each glacier in a standard spatial framework that was digitized within a geographic information system to create a time series for interpretation and analysis.

General shrinkage has occurred for every glacier for which researchers have measurements but rates of change varied. The larger glaciers are now approximately 1/3 their size in 1850, and numerous smaller glaciers have disappeared. There has been a 73% reduction in the area of the park covered by glaciers from 1850-1993. Out of 84 watersheds, 18 have 1% glacier cover, 8 have 2% cover, and 4 have 3%. Average glacier area in the accumulation zone for September 1993 was 35%, indicating negative mass balances for most glaciers and continued shrinkage.

A computer model indicates that present rates of increasing warming will eliminate all glaciers in Glacier National Park by 2030 (Hall, 1994). Even with no additional warming over that which has already occurred in the area, the glaciers are likely to be gone by 2100.

Hall, M. H. P., 1994, Predicting the impact of climate change on glacier and vegetation distribution in Glacier National Park to the year 2100: Syracuse, State University of New York, M.S. Thesis, 192 p.

Monitoring in Mount Rainier National Park

Both the National Park Service and the U.S. Geological Survey have made systematic measurements of Mount Rainier’s glaciers since the late 1890s, making it one of the longest and most detailed records of glacier change in the United States. Monitoring techniques include: (1) mapping the terminus of glaciers, (2) determining glacier characteristics using remote imaging and digital mapping technology, (3) determining glacier volume, (4) monitoring glacier motion, (5) measuring mass balance, and (6) determining the extent of ancient glaciers using post-glacial landforms.

Monitoring has revealed that in 1994 Mount Rainier’s glaciers had a combined area of 35 square miles, and an estimated total volume of 1.0 cubic mile. Between 1913 and 1994, the combined area dropped by 21% and total volume by 25%. In general, glaciers on the south side of the mountain shrank more than glaciers on the north side (total area losses of 27% and 17% respectively). The changing position of glacier termini indicate that all of the mountain’s major glaciers retreated between 1913 and the late 1950s, then advanced until the early 1980s, and then retreated significantly during the 1990s.


Monitoring in North Cascades National Park

Measuring glaciers can be difficult and expensive because glaciers are often located in remote areas where travel is complicated by rugged alpine terrains and adverse weather. This is true in the North Cascades Range of Washington, where dense forests, steep slopes, and poor weather make foot travel slow and often rigorous. Furthermore, helicopter support is limited by flight regulations in wilderness areas and is highly weather dependent.

One approach for tracking glacier change is to monitor a single, relatively accessible glacier in a region and treat it as representative member of the glaciers in the region. In 1958, the U.S. Geological Survey (USGS) selected South Cascade Glacier, a valley glacier to the southwest of North Cascades National Park, to represent the North Cascades Range. Several times each year (in spring, summer, and autumn) ground crews make measurements of changes in the glacier’s mass, and researchers analyze that year’s aerial photographs. The result is a nearly 50 year record of the size, shape, and dynamics of the glacier, one of the longest continuous detailed records of glacier change in the world.

In 1993, the National Park Service began a glacier monitoring program within the North Cascades National Park Complex in order to determine how representative the changes of South Cascade Glacier are to glacier changes in the rest of the North Cascades. Researchers selected four glaciers of different size, type, and location to represent a wider cross section of the region’s glacier population. Like the USGS program, researchers acquired yearly aerial photographs and made ground based measurements of the changing glacier mass. A similar program, conducted by the North Cascades Glacier Climate project, has provided additional information by conducting mass change studies on 48 other glaciers spread throughout the North Cascades.

Researchers calculated changes in glacier area and volume between 1958 and 1998 for approximately 80% of the glaciers of the Upper Skagit River Basin. The majority of these glaciers shrank. Because the regional benchmark, South Cascade Glacier, also lost mass between 1958 and 1998, researchers assume that its mass-balance record can be used to represent yearly mass changes for most of the glaciers of the Upper Skagit Basin. Therefore most of the glaciers of the Upper Skagit Basin had more years when they lost mass than years when they gained mass. Furthermore, most of the mass they lost between 1958 and 1999 was lost between 1976 and 1998.

Tangborn, W., 1980, Two models for estimating climate-glacier relationships in the North Cascades Washington, U.S.A.: Journal of Glaciology, v. 25, no. 91, p. 62-67.



Glaciers Index

Introduction to Glaciers

Ice Ages

Nature's Landscape Architect

Glaciers and National Parks


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