Glaciology L1: Glaciers, ice sheets and their temporal and spatial distribution

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What is a glacier?
A body of ice that moves downslope under its own weight and formed from the compaction of snow
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Why is the description of glaciers: "rivers of ice" not particularly accurate?
They are not formed from frozen water. They are produced when snow persists and contributes to layers over time. This build up compacts deeper snow into first Firn then ice.
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What are valley glaciers? Provide an example.
Glaciers bounded by valley walls. Mer de Glace, France.
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What is the name of the system including everything that is frozen on the planet?
Cryosphere
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Why is the term "glacier" a little simplistic?
This consists of many landforms i.e. ice sheets, caps, permafrost, etc.
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What are the three main ice sheets on the planet today?
Greenland. East Antarctica. West Antarctica
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Define: ice sheet
A large body of ice >50,000km2 that submerges topography
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What are ice caps? Example?
Less than 50,000km2 but still submerge some topography. Vatnajokull, Iceland (2 dots above the "o")
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What are nunataks? Example
Mountain peaks that emerge from beneath ice caps. E.g. Cathedral Peak, Yosemite National Park, USA
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What features often extend outwards from ice caps/sheets?
Outlet glaciers
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What are tidewater glaciers? Example?
Glaciers that terminate in the sea, also tend to be highly dynamic e.g. Kronebreen, N.W. Svalbard- moves 2 metres a day
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How is ice lost from tidewater glaciers?
Calving- where large blocks break off from the ice into the sea.
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How is sea ice different to glacial ice?
Sea ice= NOT glacial ice. Sea ice=frozen seawater.
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How are the majority of glaciers worldwide changing? Example?
Majority= shrinking as global average temperature is increasing e.g. Peyto, Canada
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How does the cryosphere change over the long-term?
Glaciers and interglaciers?
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What has been the effect of the latest interglacial on the cryosphere
Since LGM (21,000 BP)- 50 million km3 ice has melted
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What factors contribute to the fluctuations between glacials and interglacials?
Milankovitch cycles (1930)- variations in the Earth's orbit which affects the solar radiation reaching the Earth.Eccentricity- how much radiation=received on earth. Precession+obliquity determine how energy= distributed. "Orbital forcing"
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What are the 3 components of the Milankovitch cycles?
Eccentricity- Cycle lasting 90,000-100,000 years- orbit changes from highly eliptical to nearly circular. Axial tilt/obliquity- 40ka cycle from 22.1-24.5 degrees- affects severity of seasons. Precession-wobble around poles-affects timing of seasons
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What are the main factors that lead to glaciation?
Temperatures in the N. hemisphere =crucial. If temp= cool enough- winter snow persists and accumulates. Glaciations coincide with periods of reduced summer insolation and increased winter precipiation in the N. hemisphere.
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What contributes to deglaciation periods?
Increase in sumer solar radiation- ablation of ice and mass loss. Lower winter solar insolation= cooler dried conditions and less precipitation.
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Which feedback mechanisms amplify the Milankovitch cycles?
Sea level & ice sheet elevation; surface albedo; Carbon dioixde concentration in the atmosphere
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How does sea level link to the size of ice sheets?
Ice growth causes sea level to fall- allowing marine regions to become glaciated- lowers sea level further. Build up of ice=more land @ higher altitude- more area for snow accumulation. Further ice growth= further sea level fall et.
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How does surface albedo affect glacial/interglaciations?
As snow builds up- higher surface albedo- more energy= reflected back out into space- temperatures fall further. Less melting of ice. Earth can't warm up. Important @ low latitudes- most radiation is received between 30N and 30S.
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How does C02 concentration affect glacial extent?
Low C02- global temperature falls- less absorption of longwave IR radiation- reduced greenhouse effect. As ice covers oceans- limits exchange of C02 between ocean and atmosphere further= further decreasing of C02 in atmsophere
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How many meters of global sea level rise are held in glaciers?
75m (Glaciers hold 75% freshwater on Earth)
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Other cards in this set

Card 2

Front

Why is the description of glaciers: "rivers of ice" not particularly accurate?

Back

They are not formed from frozen water. They are produced when snow persists and contributes to layers over time. This build up compacts deeper snow into first Firn then ice.

Card 3

Front

What are valley glaciers? Provide an example.

Back

Preview of the front of card 3

Card 4

Front

What is the name of the system including everything that is frozen on the planet?

Back

Preview of the front of card 4

Card 5

Front

Why is the term "glacier" a little simplistic?

Back

Preview of the front of card 5
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