Glaciated Landscapes - Set 1 Flashcards
(50 cards)
1
Q
How do we know climate has changed
A
- Tree rings = Large gaps mean hotter year
- Pollen records = What plants were growing at different times
- Ice core = More CO2 means hotter period
- Historical records = Pictures etc
2
Q
Milankovitch Theory
A
- Eccentricity = from elliptical to circular over 100,000 yrs - changes amount of radiation from sun
- Axal Tilt = Varies from 21.8 - 24.4 degrees over 41,000 years - changes intensity of sunlight received at the poles and therefore seasonality of earths climate
- Procession = wobble - Changes point at which earth is closest to the sun - 21,000 year cycle
3
Q
Positive feedback loops
A
- More snow and ice which raises albedo and reflects suns energy which cools earth and produces more snow and ice
- Temps increase = snow and ice melt = more solar energy absorbed = permafrost melted = more CO2 released = warmer temps
4
Q
Negative feedback loops
A
- More evaporation and pollution results in more clod cover which reflects solar energy and cools earth
- Warming in arctic disrupts ocean currents - leads to cooling in northern Europe - result of Thermohaline circulation
5
Q
Glacial
A
Cold, Ice house periods within the Pleistocene
6
Q
Interglacial
A
Warmer periods similar to present day
7
Q
Stadial’s and Interstadials
A
Short term fluctuations within greenhouse conditions - Stadial’s are colder periods
8
Q
Cryosphere
A
Part of earth which stays below 0 degrees for part of each year
9
Q
Active layer
A
Top layer of soil in permafrost that thaws during the summer
10
Q
Firn
A
Crystalline snow, generally on top of a glacier, which has not yet been compressed into ice
11
Q
Short term causes of climate change - Sunspots
A
- Intense magnetic storms on the sus surface
- More sunspots = more solar radiation
- Maunder minimum = 1645 - 1715 = long period with no sunspot activity
- 20% of 20th century warming comes from sunspots
12
Q
Short term causes of climate change - Volcanic eruptions
A
- Pyroclastic flows reduce amount of solar radiation reaching earth surface
- Eruption of Tambora led to a 0.7 degree drop in global temps
13
Q
Short term climate events
A
- Little ice age = 1500 - 1850
- Crop practices had to be adapted
- Villages in Swiss alps destroyed by glaciers advancing
- Sea ice extended from Ireland
14
Q
Short term climate event - Loch Lomond stadial
A
- Rapid drop in temps 115,000 years ago
- 3 pulses of ice advanced - Most extensive happened 10,000 years ago
- Caused an ice cap in western Scotland
15
Q
Biosphere
A
Regions of earth occupied by living organisms
15
Q
Hydrosphere
A
All water on earths surface
16
Q
Atmosphere
A
Gasses surrounding the earth
16
Q
Lithosphere
A
Rigid outer part of earth, including the crust and upper mantle
16
Q
Types of ice sheet - Ice sheet
A
- Complete submergence of regional topography forms dome of ice several kilometres thick
- up to 100,000km squared
- e.g. Greenland ice sheet
16
Q
Types of ice sheet - Ice field
A
- Covers upland area - not thick enough to bury topography
- up to 10,000km squared
- e.g. Patagonia
16
Q
Types of ice sheet - Ice cap
A
- Smaller version of ice sheet occupying upland areas
- Up to 10,000km squared
- e.g. Vathajokull, Iceland
17
Q
Types of ice sheet - Valley glacier
A
- Confined between valley walls - many terminate in the sea
- up to 1500km squared
- Aletsch, Switzerland
18
Q
Types of ice sheet - Piedmont glacier
A
- Valley glacier which extends beyond the end of a mountain valley onto a flatter area and spreads out
- up to 1000km squared
- Malaspina, Alaska
19
Q
Types of ice sheet - Cirque glacier
A
- Smaller glaciers occupying a hollow on the mountain side - carves out a corrie
- up to 8km squared
- e.g. Hodges glacier, South Georgia
20
Types of ice sheet - Ice shelf
- Large area of floating glacier ice extending from the coast where several glaciers gave reached the sea
- up to 100,000km squared
- e.g. Ronne and ross ice shelf, Antarctica
21
Glaciers
Mosaic of different types of ice - Most are polythermal ( where the ice in the middle is warmer and ice on exterior is colder )
22
Polar Glaciers
- Occur in cold areas - topography is usually gentle
- Base is much colder than pressure melting point temp and so little melting occurs
23
Temperate glaciers
- Occurs is areas with milder summers - allows melting to occur
- Relief is usually steeper e.g. the Alps
- Melting point of glacier is same as pressure melting point
24
Internal flow (deformation)
- Glacier frozen to bed - no friction and thus no melting - only move 1-2 cm daily
- Polar glaciers move this way
25
Basal slippage
- Glaciers move = increase in friction with bedrock - raises temp - basal ice melts - meltwater acts as lubricant - glaciers move 1-2 metres daily
26
Surging glaciers
- AKA ice streams
- rates of flow up to 100metres daily
- e.g. Greenland outlet glaciers which average 30metres daily - lots of calving
27
Distribution of ice
- Alpine glaciers in Himalayas and coast of North America
- Unnavigable pack ice is below Antarctic circle
- All permafrost in northern hemisphere e.g. Russia
28
Altitude
Every 100m it gets 1 degree cooler
29
Latitude
High latitude - suns rays hit ground at a lower angle so solar radiation is reduced
30
How are glaciers formed
- Temps must be low but positive e.g. slightly above 0 degrees
- Lower layers compress and form neve
- Pressure induced melting and refreezing - fills gaps between ice crystals which increases density
- Can take up to 4000 years
31
Glacier inputs
- Precipitation in form of snowfall
- Avalanches
- Wind deposition
32
Glacier stores
- Snow and ice - seasonal changes in size
33
Glaciers Flows
- Glacial movement - e.g. basal slip
- Evaporation and sublimation
34
Glaciers outputs
- Water from melting close to glaciers snout
- Calving
- Evaporation of water formed by melting of ice on top of glaciers
- Sublimation = Solid turns to a gas missing out a liquid stage
35
Mass balance
Gains and losses of the ice stored in a glacier system
36
Accumulation
Results from snowfall and other inputs
37
Ablation
Snow and ice lost to the glacier system by melting etc
38
Equilibrium line
Boundary between accumulation and ablation zones - if this shifts up or down the glacier it is called a dynamic equilibrium
39
Glacier mass balance ( Ice budget )
- Shows accumulation and ablation of a glacier system throughout a year
- Positive regime = glaciers grow
- Negative regime = glaciers shrink
40
Health of glaciers today
- 75% of global ice masses are retreating
41
How to measure glaciers mass balance
- Altimetry = Measurements of ice sheet surface elevation surface
- Gravimetry = gravitational attraction of the ice sheet
- Mass budget method = amount of snow accumulated on ice sheet and volume of meltwater leaving the glacier
42
Fundamental cause of ice movement
- Gravity - ice moves downslope
43
Shear stress
- weigh of snow and ice exerts increasing force due to gravity - glacier ice pulls away and moves downslope
44
Principles of glacier movement
- Lower zone = ice behaves like plastic as it is under steady pressure
- Upper zone = brittle - can be put under sudden compression or tension which causes it to break apart
45
Glacier movement - Creep and Regelation
- Basal slip enhanced by obstacles on valley floor - large obstacles cause increase in pressure - makes ice at like plastic to het around it - causes pressure melting point to be met and therefore meltwater produced
- Process of melting ad refreezing is known as regelation
- Temperate glaciers
