1: The Formation, Distribution And Mass Balance Of Glaciers Flashcards
Two main requirements for the formation of glaciers?
Low temperatures, precipitation in form of snow
Once a __ depth has been reached, ice begins to deform and flow
Critical
What % of earth is covered by ice?
10%
How much of earths ice is stored in ice sheets, and how much in glaciers and ice caps?
97% in ice sheets, 3% in glaciers/ice caps
Name 5 factors which influence mass balance of ice sheet
Latitude, Altitude, Distance from source, Aspect, Relief
Name 4 ways in which a large ice sheet such as Antarctica maintains its own climate
Decreasing precipitation, high albedo, high altitude, very low temperature in centre
Which two variables define a balance gradient
Volume of ice (water equiv) against meters above sea level
What would the gradients of both a long shallow glacier and a short steep glacier look like?
Long/shallow = more vertical gradient (small change in balance with increasing height). Short/steep = more horizontal (large change in balance with increasing height)
Give examples of both a long/shallow glacier and a short/steep glacier
Long/shallow = Norway (?), short/steep = arctic Canada (?)
What is the equation for the balance ratio?
Balance ratio= (∂bnb/∂z)⁄(∂bnc/∂z) where bnb is mass balance in ablation area, and bnc is mass balance in accumulation area.
What does the balance ratio do?
It gives a useful generalization that summarizes overall mass balance curve of a glacier
What would the curve look like for a glacier which experiences high volumes of debris cover at the bottom, patchy debris in the middle, and snowfields and avalanche cones nearer the top?
Net ablation at debris cover, decreasing towards equilibrium in patchy area with net accumulation with avalanche cones and snowfields near top. (See fig 2.28 and 2.29 in Benn and Evans.)
Name three methods for direct measurement of ablation (know how each works)
Ablation stakes, rangefinder technique, pressure transducer
Name three methods for direct measurement of accumulation (know how each works)
Excavated pits in snowpack, dirt layer ID, ID of changes in density and crystal size
What is the hydrological method of measuring mass balance, and what are the main factors needed to deduce mass balance of a glacier?
Measures the change in water storage in catchment and thus change in water storage of glacier – requires annual precipitation, evapotranspiration and runoff figures, as well as change in water storage which is not direct storage on glacier, such as aquifer, snowcover which is not on glacier, water stored as water in/on/under glacier. All of these factors plus the storage of water as ice in the glacier must equal 0, thus we can deduce the final factor.
Give examples of geodetic methods used in measuring mass balance of glaciers
Remote sensing, aerial photographs, satellite data.
Give an example of a gravimetric method and explain how it works in measuring mass balance of a glacier
Satellites which detect small changes in gravity pull, can then detect the mass of an ice sheet – perhaps crude.
What is the area-altitude relationship?
The direction of balance for a given climate change is specific to the glacier, and the shape of basin in which it resides and the proportion of the glacier in accumulation zone as opposed to ablation zone
What happens to the ELA in a state of +ve mass balance and why?
In +ve mass balance, the ELA will move downwards due to expansion of accumulation area
What is the relationship between the ELA and hypsometry?
With a change in ELA, the amount of mass lost or gained depends on hypsometry – glaciers with large areas of snow and ice near ELA show large responses to climate change.
Explain the units of mass balance
Meters of water equivalent – represents average thickness gained or lost from glacier.
What is superimposed ice?
Water saturated snow which is frozen
Where is superimposed ice most commonly found?
At the surface between the equilibrium line and the snow (firn) line in the accumulation zone.
What is the name for superimposed ice that survives a season of ablation?
Internal accumulation
