Glaciation - Unit 1 Flashcards
What is a glacier?
A moving body of ice
What is a system?
Consists of inputs, outputs, stores and transfers
Why might a glacier be considered a system?
It is considered a dynamic system as it’s in a constant state of flux
How are glaciers formed?
- Snowflakes fall (density = 0.1gm/cc + contain air)
- Collects in hollows
- Begins to compact
- Forms neve (compacted snow that has experienced 1yr of freezing and melting)
- Summer meltwater percolates into neve
- Becomes more dense when it refreezes
- Air is squeezed out
- After a number of years, a glacier can form (density = 0.9gm/cc)
What is a positive balance?
When Inputs are greater than outputs so glacier advances
What is a negative balance?
When outputs are greater than inputs so glacier retreats
Inputs?
Snowfall
Avalanches
Outputs?
Evaporation
Sublimation
Meltwater
Ablation?
Natural removal of snow/ice from surface of glacier
Accumulation?
Build up of glacier and snow is compacted into ice
Calving?
Splitting end of glacier into smaller sections
Glacial budget?
Mass balance - determines if glacier will advance/retreat
Accumulation zone?
Located at head of glacier
Inputs > outputs over 1 year
Equilibrium zone?
Located at centre of glacier
Inputs = outputs over 1 year
Ablation zone?
Located at snout of glacier
Inputs < outputs over 1 year
What are the short term changes to mass balance?
Annual changes
Anthropogenic climate change
What are the long term changes to mass balance?
Natural climate variations
What are some of the potential changes for our planet in the next 100 years?
- CO2 levels increase by almost 200ppm
- Average temp increase by 2°C
- Sea level increase by almost 5m
How does positive feedback affect the glacial mass balance system?
Snow and ice cover-
If it increases:
- Raises surface albedo (reflectivity of Earth’s surface)
- More solar energy reflected back into space
- Further cooling
- More snow/ice cover
If it decreases;
- Lowers surface albedo
- Less solar energy reflected back into space
- Increases heating
- Permafrost melts and methane is released
- Less snow/ice cover
How does negative feedback affect the glacial mass balance system?
Increase in our current global warming trend leads to increased evaporation from oceans = more cloud cover
Cloudy skies reflect more incoming solar energy
Decrease in global warming = decrease in melting ice cover
