K.I.3 The glacier as a system.

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K.I.3 The glacier as a system.

• Dynamic Equilibrium
• Positive and negative feedback

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Inputs Throughputs Outputs Energy Transfers
(moving ice) Energy (e.g. low Storage (warmer
in summer) temperature) Processes (e.g.
abrasion) Matter Matter (e.g.
Snowfall, meltwater Avalanches direct
evaporation from valley sides
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Feedback effectsWarming will trigger some
processes which speed further warming, and other
effects which mitigate it. The balance between
these positive and negative feedbacks is a major
cause of uncertainty in climate predictions. For
example, as the diagram shows, decreasing ice
cover will mean exposed land absorbs more heat
and speeds warming further.(Positive Feedback
1) In contrast, for example, plants' CO2 intake
is likely to increase as higher temperatures
increase growth (Negative Feedback)
1 Light coloured ice reflects back the Suns
energy efficiently.2 Exposed land is darker
coloured and absorbs more energy.3 As the ice
melts, more land is exposed. This absorbs more
heat, melting more ice.4 The altitude of the
melting ice is reduced so it becomes harder for
new ice to form.
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Positive feedback 2
Glacier surge is a common phenomenon in Svalbard.
Glacier surge is a sudden advance of the glacier
where a large volume of ice is transported from a
reservoir area down to the frontal part of the
glacier, usually followed by a sudden and rapid
advance of the glacier front. The active surge
advance period usually lasts a few years, while
the quiescent, up-building period is in the order
of 100 year.
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In a glacial cirque as this is enlarged from an
initial hollow the capacity for storing
accumulating ice grows and so erosion increases.
Causing the rate of cirque growth to accelerate.
(small scale, short term, low energy) Positive
Feedback 3
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If a glacier is in steady state (that is with a
stationary snout) is affected by increased
snowfall high up in the accumulation zone of the
cirque then the ice volume will increase and the
glacier will advance and the snout will move
forward (perhaps creating a push moraine)
Negative Feedback
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Negative Feedback
This is what happens when a glacier advances into
a forest.This is on the eastern margin of the
Taku Glacier, Juneau Alaska. As you can see, the
trees didn't stand a chance against the power of
the glacier. The glacier toppled and overrode
these trees in the winter of 1992-93. Summer
melting of the ice has exposed the debris. The
ice is shown in the lower left.
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Negative Feedback
However, this will cause more of the glacier to
lie in the ablation zone and so the output of
meltwater will increase. In time the increased
output of meltwater will come to equal the
increased input of water via snowfall.
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The glacier will return to a new steady state and
the snout advance will stop ( leading to the
build up of a terminal moraine landform in that
position where the snout lies)
Terminal and lateral moraine ridges, Kazakhstan.
The glacier has retreated since it formed the
ridges. Negative Feedback.