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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

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3000

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5000

-10% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

Area Change

Ele

vatio

n (m

)

1913-1971

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-10% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

Area Change

Ele

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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

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-1.0

-2.0

-1.5

-0.5

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Con

tribu

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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

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1.5

2

1 21 41 61 81 101

Series3

Series2

Series1

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1.5

1.0

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-1.5

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Con

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to E

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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