Karteikarten
PW2
Karten in diesem Stapel (19)
- 1Define accumulation-All processes through which material is added to the glacier
- 2Define Ablation-All processes through which material is removed from the glacier.
- 3What are the ways in which accumulation and ablation can occur?
- 4Why does ice have to move?-If it didn’t then eventually there would be a huge accumulation of ice in one part and no ice in the evaporation and sublimation part. The only way that this can work is if the ice can move from the areas where the precipitation falls to the areas where it can evaporate.
- 5What is the definition of mass balance?-The mass balance of a glacier is defined as the difference between gains and losses.
B= c-a in conclusion Mass Balance =accumulation- ablation
-Expressed in equivalent water per unit area which is the water equivalent depth of snow per m2.
-This is because density and many other facts can impact on what the mass balance is. - 6What is the net balance?Net balance=winter balance – summer balance.
- 7How can this be demonstrated (Benn and Evans)
- 8What is the specific balance?-When it is recorded at a specific balance
- 9What is the ELAThe altitude at which the net balance is 0 know as the equilibrium line altitude (ELA)
- 10Why do ELA vary?-ELA fluctuates annually, if the temperature drops then area of glacier can receive snow is raised, thus ELA moves down the glaciers
-End of the summer- upper area snow, lower area is covered in ice. The snow line represents the point of equilibrium
-This is a theoretical concept, it can only be observed at the end of summer. - 11What is the gradient balance like in artic Canada?-Shallow gradient of net balance, doesn’t change much over the year- only fluctuating around half a meeter.
- 12What is the gradient balance like in Norway?-Fluctuates a lot and thus is a less steep gradient.
- 13What factors can affect gradient variation?-Finite moisture source, less snowfall with height.
-Local topographic and climatic factors affecting the distribution of net balance with altitude.
-Ablation: gradient, temperature, cloudiness, humidity, proximity to rock walls, shading, aspect, debris.
-Accumulation gradient: Increasing snowfall with altitude, distance from the moisture source, mass redistribution - 14How did net balance used to be measured?-Ablation syakes
-Use tape on stake at summer in winter, can get net balance.
-Needs to be scaled up - 15How can net balance be calculated now?-Photogrammetric methods- digital elevation models.
-Digital evaluation models
-Mass balance calculated from changes in geometry of Midre-Lovenbreen
-DEM’ produced from digitising aerial photographs.
-Darker areas show surface lowering (thinning and mass loss), lighter areas show glacier thickening
-The hydrologic method
-Bn= P- R – E
Bn net balance
P precipitation
R runoff
E evaporation - 16Other than climate what may mass balance respond to?-Area, altitude relationship
-For a given climatic change, one glacier may display a positive balance whilst another may display a negative balance.
-This all depends on the shape of the glacier basin and the proportion of the glacier which is in the accumulation zone as opposed to the ablation area. - 17What impact does hypsometry and the position of the ELA?-+ve mass balance- expansion of accumulation areas and lowering of the ELA.
--ve mass balance- reduction in accumulation area and raising of ELA.
-For any changes in ELA, amount of mass lost depends on hypsometry
-Glaciers with large areas of snow and ice near the ELA show large response to climate change. - 18What is the median elevation of glacier method (MEG?)-The area weighted mean altitude
-The altitude at which there is an equal area of glacier above and below is taken to represent the ELA.
- 19What are the assumptions for this?-The glaciers are in equilibrium with climate
-Linear relationship between altitude and accumulation
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- Karteikarten am PW2, erstellt von erossmae am 25/08/2015.
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