Glaciers and Permanent Snow - Glacier National Park

Overview

Since its establishment in 1910, Glacier Park has lost most of its glaciers. Over two-thirds of the estimated 150 glaciers existing in 1850 had disappeared by 1980.

Data Layer Description

Source

US Geological Survey, Northern Rocky Mountain Science Center

What this data layer represents

This layer depicts glacier and permanent snow levels in Glacier National Park at 50-year intervals starting in 1850 and ending in 2000.

Location

Glacier National Park, Montana

Description

Since its establishment in 1910, Glacier Park has lost most of its glaciers. Over two-thirds of the estimated 150 glaciers existing in 1850 had disappeared by 1980 (Carrara and McGimsey 1981). Furthermore, over that same time period, the surviving glaciers were greatly reduced in area. The local summer mean temperature increased 1.66ºC between 1910 and 1980. These events reflect a worldwide pattern of glacial retreat and regional climatic change that, in aggregate, has been viewed as evidence of global warming.

The global retreat of mountain glaciers could have direct consequences for humanity. Fifty percent of the freshwater that humans consume yearly comes from mountains (Liniger et al. 1998). Disappearing glaciers have a significant impact on mountain hydrology (Fagre et al. 1997) and leave new terrain for plant colonization. In many parts of the world, distant mountain glaciers provide lowland rivers with the hydrological base flow (i.e., the minimum flow when snowmelt’s contribution to flow is at its lowest) upon which agriculture depends in late summer. The reduction in the Zongo Glacier in the Bolivian Andes has created water supply problems for downstream communities (Liniger et al. 1998). Globally, a 10 to 25-centimeter (cm) rise in sea level has been recorded during this century; Meier (1984) and others attribute part of this rise to the worldwide retreat of alpine glaciers. Thus even those who live far from mountains have experienced the consequences of melting glaciers.

However, the most significant aspect of glacial retreat may be that it is tangible and intuitive evidence of broader environmental changes that are more difficult to measure. Glaciers are excellent barometers of climate change, because they respond directly to trends in temperature precipitation, and cloud cover (which mediates solar radiation). These same climatic factors also drive ecosystem change. Unlike plants and animals, however, glaciers do not adapt behaviorally or physiologically in ways that mitigate the impacts of climatic change. Although many abiotic aspects of ecosystems, such as stream hydrology, are greatly modified by plant community responses to changed conditions, glaciers are merely a physical reflection of the surrounding conditions. Moreover, they provide a signal that integrates climatic change over time, because they do not respond to year-to-year variability. Rather, they change their dimensions and mass slowly in response to decadal trends in climate. Thus, the global retreat of glaciers can be attributed to real climatic changes, not to temporary anomalies.

For this layer, The climatic causes of glacier retreat were analyzed, the melt rate (change in glacier area/decade) determined, and the topographic influences on the spatial pattern of melt were examined. Analysis of glacial area extent per decade from 1850-1979 versus a variety of climatic drivers reveals that annual precipitation and summer mean temperature together explain 92% of the loss over time. Analysis of the spatial distribution of these glaciers as a function of three topographic variables --elevation, slope and solar aspect shows elevation (or temperature) to be twice as important as slope or aspect in determining the pattern of glacier shrinkage. Using this information to parameterize the simulation model GLACPRED , the potential future glacier behavior was predicted: all glaciers in the basin will disappear by the year 2030 if current trends continue. Even if no further climatic forcing occurs, the glaciers are predicted to be all but gone by 2100 (Hall and Fagre 2003).

How you might make use of this data layer

This data layer clearly demonstrates that the iconic glaciers of Montana's Glacier National Park have been shrinking rapidly over the last 150 years.

How to get more information

Visit the webpage for USGS's model of climate-induced glacier change in Glacier National Park.

Cited above:

Carrara PE, McGimsey RG. 1981. The late-neoglacial histories of the Agassiz and Jackson Glaciers, Glacier National Park, Montana. Arctic and Alpine Research 13: 183–196.

Fagre DB, Comanor PL, White JD, Hauer FR, Running SW. 1997. Watershed responses to climate change at Glacier National Park. Journal of American Water Resources Association 33: 755–765.

Liniger H, Weingartner R, Grosjean M. 1998. Mountains of the World: Water Towers for the 21st Century. Berne (Switzerland): Paul Haupt.

Meier MF. 1984. Contribution of small glaciers to global sea level. Science 226: 1418–1420.

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