A. IntroductionLearning outcomes - You should be able to:
describe the components of glacial mass balance;
- explain the processes affecting glacial mass balance and equilibrium line elevation;
- discuss the impact of mass balance gradient on glacier flow rates; and
- classify glaciers based on their mass balance
Glaciers classified based on:
morphology
temperature
mass balance
Classes:
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
equilibrium line (snow line)
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.
ELA increases with:
decreasing snowfall
increasing temperature
negative net mass balance
distance from moisture source
Measurements
balance year; winter balance, summer balance
bn = bw + bs
direct measurements: stakes, snow pits
remote sensing measurements
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.
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
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