CAS ES 107 Chapter Notes - Chapter 6: Heat Flux, Ocean Current, Systematic Chaos
7 Jun 2018
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Chapter 6 Part 2
Glaciers and Ice Sheets
-temp gradients in snow packs together with differences in the size and shape of the ice crystals
cause localized differences in vapor pressure that result in sublimation from some crystals and
deposition in others
-this produces rounding in the crystals and compaction, which is further increased by pressure as
the snowpack increases in thickness
-the volume between the ice grains is reduced, ice crystals become compacted, density increases
and the snow turns into glaciers
-when the surface melts, the meltwater can percolate down through the pack and refreeze,
speeding up the process of glacier ice formation
-at this stage, the ice has low permeability and it can flow and move under its own weight, which
allow glaciers to move
Glacier Flow
2 types of glaciers: continental and mountain
-most of the ice is in Antarctica
-all glaciers are big enough to move
-a higher pressures, deeper within a glacier, slowly applied stress case the ice to deform more
like plastic. This stress increases as you move deeper into the ice and causes the ice to flow
-glaciers can help us understand past climates and atmospheric gas concentrations by extracting
gas from the air cavities with ice core drilling
-the ice profile (thickness and extent) depends on the accumulation, transport and melt
-if there was noice flow, there would be no ablation zone (melt) because no ice would flow from
inland and any snow in that region would just melt. There would be no melt in the accumulation
zone and snot that fell would build up as ice
-the ice would not thicken exponentially because the ice at the base would start to melt as a
consequence of high pressure, along with warming provided by geothermal heat coming from
below
-the high pressure lowers the melting point by a few degrees…but this is small… so what really
makes the ice melt is the heat from below
-when ice thickness reaches 4km, the temp at the base approaches 0 degrees C and ice begins to
melt
-higher temps have been causing meltwater to percolate down beneath these outlet glaciers,
causing them to flow faster and to increase the rate of ablation and ice loss from continents
-glacial flow is highly variable and depends on ice structure, temperature, slope, bedrock type,
and the presence or absence of water at the base of the glacier
Ice-Climate Interactions
-ice cover is measured using satellite observations of the microwave radiation emitted from the
ice surface
-because certain wavelengths of microwave radiation are not absorbed or scattered by the
atmosphere and the cloud cover, we can obtain accurate measures of the ice extent regardless of
the weather or time of day
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Temp gradients in snow packs together with differences in the size and shape of the ice crystals cause localized differences in vapor pressure that result in sublimation from some crystals and deposition in others. This produces rounding in the crystals and compaction, which is further increased by pressure as the snowpack increases in thickness. The volume between the ice grains is reduced, ice crystals become compacted, density increases and the snow turns into glaciers. When the surface melts, the meltwater can percolate down through the pack and refreeze, speeding up the process of glacier ice formation. At this stage, the ice has low permeability and it can flow and move under its own weight, which allow glaciers to move. A higher pressures, deeper within a glacier, slowly applied stress case the ice to deform more like plastic. This stress increases as you move deeper into the ice and causes the ice to flow.
