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Glacier Change in the American WestANDREW G. FOUNTAIN, KRISTINA THORNEYCROFT, HASSAN J. BASAGIC, GREGORY J. McCABE
Departments of Geology and Geography, Portland State University, Portland, Oregon, USA
IntroductionGlaciers are located throughout the American West in the states of Washington, Oregon, California, Montana, Wyoming, Colorado, Idaho, and Nevada. The glaciers occupy a range of climates, are important indicators of climate trends in alpine regions, and play a significant role in the hydrology of alpine ecosystems.
We have compiled a 100-year history of glacier change using historic maps and photographs to identify the magnitude and rate of glacier change across the West.
Map-based Glacier InventoryWe inventoried all glaciers, perennial ice, and snow to define the number and area of these features. The GIS database is based on USGS 7.5 minute topographic quadrangle maps (1:24,000 scale). The USGS created these topographic maps from aerial photos. A total of 8303 glaciers, ice and snow features were found with a total area of 688 km2.
ConclusionsOverall warming is affecting all glaciers in the American West. Depending on altitude, warming winter temperatures may or may not play a role at this time. Differential shrinkage across the West appears to be controlled by variations in snow fall. Elevation range is an important factor in glacier response.
Adios icy amigos.
ReferencesBasagic, H.J., and Fountain, A.G (submitted). Quantifying Twentieth Century Glacier Change in the Sierra Nevada.
Fountain, A. G., Hoffman, M. J., Jackson, K. M., Basagic, H. J., Nylen, T., and Percy, D., 2007: Digital Outlines and Topography of the Glaciers of the American West. U.S. Geological Survey Open-File Report 2006–1340, 23 pp..
Granshaw, F. D., and Fountain, A. G., 2006: Glacier change (1958-1998) in the North Cascades National Park Complex, Washington, USA. Journal of Glaciology, 52: 251-256.
Hoffman, M. J., Fountain, A. G., and Achuff, J. M., 2007: Twentieth-century variations in area of small glaciers and icefields, Rocky Mountain National Park, Rocky Mountains, Colorado, USA. Annals of Glaciology, 46: 349-354.
Jackson, K. M., and Fountain, A. G., 2007: Spatial and morphological change on Eliot Glacier, Mount Hood, Oregon, USA. Annals of Glaciology, 46: 222-226.
Meier, M. F., 1965: Glaciers and climate. In Wright, H. E., and Frey, D.G. (eds.) The Quaternary of the United States. Princeton: Princeton University Press, 795-805.
Nylen, T., 2004: Spatial and Temporal Variations of Glaciers on Mount Rainier between 1913 and 1994. MS thesis. Portland State University, Portland, Oregon, 94 pp.
Darwin Glacier, Sierra Nevada, California
South Cascade Glacier, Washington
2004 H. Basagic
1908G.K. Gilbert
Grinnell Glacier, Montana
Eliot Glacier, Mount Hood, Oregon
Andrews Glacier, Colorado Glacier
66%
24%
30%
55%
40%
Glacier Area Lost since 1900
42%
25%%46%
Quantifying Glacier ChangeGlacier boundaries were delineated from historic maps, ground and aerial photographs into a GIS for a subset of glaciers in different regions in the American West.
(Top to bottom) Historic map of Lyell Glacier, CA (1885), aerial photo of Garnett Glacier, WY, repeat photos of Lyell Glacier, and moraines of Eliot Glacier, OR.
GIS Glacier Change Database
Historic Maps
1938 1981 1998 2006Hileman, GNP Key,USGS Fagre, USGS Holzer, USGS1960 USGS 2004 J. Scurlock
1901
H.F. Reid (courtesy the Mazamas)
2005
K.M. Jackson
1916 W.T. Lee 2001 J. Achuff
Aerial Photos
Net Mass Change
Surface MassAnd
Energy Exchange
Effect onLandscape
Climate
Local Meteorology
Dynamic Response
Changes In
Geometry
Repeat Photos
Geologic evidence
(Meier, 1965)
ClimatePrinciple component (PC) analysis was used to estimate annual glacier area change based on seasonal temperatures and precipitation (Pwin, Psum, Twin, Tsum) for 1900 through 2008. Two components emerged (right). Stacked bar charts of the relative contributions of standardized cumulative departures of seasonal precipitation and temperature to departures of estimated glacier area change for each of PC sites (the relative contributions were computed using the regression for PC) shown below.
Elevation DifferencesGlaciers that span large elevation differences (e.g. on stratovolcanoes) are less sensitive to the effects of rising winter temperatures (rain vs snow), whereas those glaciers with a small elevation range are more susceptible. This highlights the role of local topographic effects.
0
1000
2000
3000
4000
5000
-10% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
Area Change
Ele
vatio
n (m
)
1913-1971
0
1000
2000
3000
4000
5000
-10% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%
Area Change
Ele
vatio
n (m
)
1971-2002
Glaciers of Mount Rainier (right)glaciers with area above 3000m glaciers below 3000m
Mount Rainer (below) and winter temperatures (modeled PRISM data)
3079
1411
1475
1778
1158
463
450
4.8
73.3
68.6
46.2
42.5
0.09
2082.6
State totalsglacier count in redtotal area (km2) in grey
Our website contains more information including our glacier inventory map, our photo archive with over 14,000 historical and contemporary photographs, state and featured glacier articles, reports, and glacier repeat photography.
Check it out: www.glaciers.us
Glacier of the American West Website
31%
Glaciers
US Forest Service lands
National Park Service lands
percent of area lost
percent of area lostcurrently being updated
stratovolcano
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1 21 41 61 81 101
Series2
Series1
PwinTsum
1900 19401920 19801960 2000Year
2.0
1.5
1.0
0.0
-1.0
-2.0
-1.5
-0.5
0.5
Con
tribu
tion
to E
stim
ated
Gla
cier
Mas
s Ba
lanc
e
wet winters, cool summers
dry winters, cool summers
mixed winters, warm summers
PC1 55%PC2 31%
ExplainedVariance
PC1
For PC1 sites, the recent negative effects of temperature on glacier mass balance appear to be unprecedented during the last century
Glacier mass balance for PC2 sites are highly sensitive to temperature variability.
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
1 21 41 61 81 101
Series3
Series2
Series1
2.0
1.5
1.0
0.0
-1.0
-2.0
-1.5
-0.5
0.5
Con
tribu
tion
to E
stim
ated
Gla
cier
Mas
s Ba
lanc
e
1900 19401920 19801960 2000Year
PsumTwinTsumdry summers,
warm summers
wet summers, cool winters and summers
dry summers, cool winters and summers
wet summers, warm winters
PC2
periods with increases in glacier mass balance
periods with decreases in glacier mass balance
wet summers, warm winters and summers
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