Lesson 6: Glacial Mass Balance Flashcards
What are glaciers primarily formed from?
Compacted snow
Describe the formation of ice
-Snow falls and collects on the glacier. Fresh layers of snow fall each day and build up
-As snow becomes compacted it starts freezing together becoming quite granular – this is called granular snow
-As the granular snow becomes increasingly compressed it forms névé or firn
-As the snow layers increase and the process continues and layers become deeper. The névé (or firn) transforms into glacier ice
Time for ice to form from neve
Little as 25 years up to 150 years in polar regions like Greenland
Time for transformation from snow to ice?
Little as 1000 years in some temperate areas, but can take up to 4000 years in Antarctica
Factors affecting rate of accumulation and ablation
Amount of precipitation
Levels of solar insolation
Latitude
Average temp.
Levels of wind speed
Continentality
Define continentality
Distance from the sea (seas/water are warmer influencing temperature around glaciers/permafrost)
Define positive regime
glacier is increasing in mass i.e. a usual situation would be accumulation exceeding ablation during the winter period
Define negative regime
glacier is decreasing in mass i.e. when ablation exceeds accumulation during the summer. Glacier begins to think/shrink
When does glacial mass balance run between?
Autumn to Autumn
Role of long-term trends
Determine the ‘health’ of a glacier and whether it will significantly advance or retreat and if thinning/retreating contributes to increased concerns over global sea level rises
% world ice experiencing ‘rising trends’ in their net negative balances
75%
% Greenland covered by ice?
80%
Minimum sea level rise if Greenland ice sheet lost?
27cm increase
How many tonnes of sea ice in Greenland will melt?
110 trillion tonnes
What could sea level rises reach in Greenland?
78cm
