What processes operate within glacial systems? Flashcards
what are some glacial inputs
precipitation
Avalanches
meltwater
rock debris
what are the glacial stores/ processes? (General)
the moving glacier erodes transports and deposits rock debris
what are the glacial outputs
meltwater
icebergs
water vapour
rock debris
what is accumulation
the input of snow and ice into a glacier
what processes cause accumulation
precipitation
wind deposits
avalanches
what is ablation
the output of snow and ice from a glacier
What are some ablation processes?
melting
ice berg calving
sublimation
evaporation
what is iceberg calving
when chunks of ice break off at the terminus, or end. of the glacier
what can cause accumulation rate to vary
high levels of inputs
low average temperatures
low levels of insolation
low wind speed
where are the highest rates of ablation
higher altitudes
on slopes with a poleward aspect
where/ what is the accumulation zone?
the uppermost section where there is greater accumulation than ablation
where/ what is the ablation zone
lower part of the glacier when the rate of ablation is higher then accumulation
what is the equilibrium line
the boundary between zones where rate of accumulation and ablation are equal
how is glacial mass balance calculated
subtracting total ablation away from total accumulation for the year
what is positive mass balance
when total accumulation exceeds ablation
what is negative mass balance
when ablation is higher than accumulation
how does the glacier move in positive mass balance
the glacier will advance as there is greater ice content
how will the glacier act when in negative mass balance
it will retreat as the input into the glacier is reduced
what will happen to the snout when in dynamic equilibrium
the glacier snout will remain stationary
what are feedback loops
deviations in in puts or outputs that move systems away from a balanced state
what do negative feedback cycles act to do?
minimise the effect of the new input, in order to re-establish stability
what is an example of a negative feedback loop
more snow in accumulation zone
increased ice volume, glacial advance
more ice volume in ablation zone
more ablation
overtime output of meltwater equals snow input
return to balance
what do positive feedback loops do?
Amplify the initial change and might cause a shift in the system to a new state of equilibrium
what is an example of a positive feedback loop (glacier)
positive mass balance
surface area increases
increased albedo
reduced air temperatures
increased accumulation
initiating positive feedback (continued advance)
how fast does the Jakobshavn glacier moving
20 meters per day at its snout