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|Glacier classification based on:
morphology
temperature
mass balance
Mass balance classification
advancing, stationary, retreating
current conditions
Image credit: graph and map from R.A. Rohde (2006) Global Warming Art http://www.globalwarmingart.com/wiki/Image:Glacier_Mass_Balance_png
Image credit: 2004 Bruce F. Molnia, USGS; 1941 W.O. Field, National Snow and Ice Data Center. Image composed by R.A. Rohde (2006) Global Warming Art http://www.globalwarmingart.com/wiki/Image:Muir_Glacier_jpg
Accumulation
Ablation
processes
climatic influence
precipitation
mean summer temperature
albedo: percent of solar radiation reflected
fresh dry snow
80-97%
firn
43-69%
clean ice
34-51%
dirty ice
15-25%
debris covered ice
10-15%
(source: Benn & Evans, 1998, p. 70)
Equilibrium Line (snow line)
ELA: equilibrium line altitude
Image credit: Austin S. Post (1961) Tenas Tikke Glacier. From the Online Glacier Photograph Database. Boulder, Colorado USA: National Snow and Ice Data Center/World Data Center for Glaciology. Digital media.
Image credit: Austin S. Post (1960) Honeycomb Glacier. From the Online Glacier Photograph Database. Boulder, Colorado USA: National Snow and Ice Data Center/World Data Center for Glaciology. Digital media.
ELA increases with:
decreasing snowfall
increasing temperature
negative net mass balance
distance from moisture sources
Glacier Flow
Provides dynamic link between accumulation and ablation subsystems
Ice discharge: ice volume passing through the equilibrium line during the balance year (m3/year)
Flow rate dependent on:
magnitude of input and output
net balance gradient: increase in net balance with altitude
the higher the gradient, the faster the flow
gradients steeper in maritime climates than continental climates
gradients steeper in temperate latitudes than in polar latitudes
Balance year
Stationary, advancing & retreating glaciers
Measurements
direct measurements: stakes & snow pits
remote sensing methods
Mass Balance
accumulation, flow, ablation
summer, winter, net
advancing, retreating, stationary
Current Global Picture
Greenland thinning due to ice melting and faster ice flow to the sea.
Image credit: NASA Visible Earth; NASA GSFC Scientific Visualization Studio. http://visibleearth.nasa.gov/view_rec.php?id=655
Image credit: 2004 Bruce F. Molnia, USGS; 1909 Ulysses Sherman Grant, USGS. Image composed by R.A. Rohde (2006) Global Warming Art http://www.globalwarmingart.com/wiki/Image:McCarty_Glacier_jpg
