Mountain glaciers and climate change Flashcards
1
Q
What are two hazards associated with mountain glaciers?
A
Avalanches
Outburst floods
2
Q
What two resources do mountain glaciers provide?
A
Water
Minerals
3
Q
What do glaciers show the impacts of?
A
Increasing air temperatures
4
Q
How is ice formed?
A
Snow compacts to form ice
5
Q
Why does snow compact?
A
Due to the weight of humans or the snow itself
6
Q
In which direction does the ice in a glacier move?
A
It moves from the accumulation zone to the ablation zone
7
Q
What happens when ice reaches the ablation area?
A
It melts
8
Q
What can break off glaciers?
A
Icebergs
9
Q
What are two ways in which mass balance can be measured?
A
By direct measurement or remote sensing
10
Q
What are two forms of direct mass balance measurement?
A
Ablation stakes
Snow pits
11
Q
How do ablation stakes work?
A
Drill into the ice and insert a pipe, overtime the ice will melt and the pipe will become more and more visible
12
Q
What is an issue with ablation stakes?
A
They are time consuming
13
Q
How do snow pits work?
A
Drill into the glacier with a chainsaw and see layers that show accumulation
14
Q
What are the issues with direct measures of mass balance? (3)
A
It is difficult to scale up and there are variations in records.
In addition proximity to humans and accessibility is an issue
15
Q
Why are there variations in records for direct measurement techniques?
A
Due to money
16
Q
What is remote sensing?
A
This means finding out information about something without touching it
17
Q
Why is remote sensing good?
A
Can cover large areas
18
Q
What is an issue with remote sensing?
A
Compromises in terms of detail
19
Q
What are 3 remote sensing methods?
A
Gravitimetry
Elevation change
SMB/D
20
Q
How does gravitimetry work?
A
Look for changes in gravity
21
Q
How does gravitimetry work?
A
If the density is known, the volume can be caluclated
22
Q
How does elevation change work?
A
Use lasers to repeatedly enter the ice surface to get surface elevation changes?
23
Q
What is SMB?
A
Surface mass balance
24
Q
How does SMB work?
A
How much put in compared to how much out from models and compare to how much ice is coming out from outlet glaciers
25
For what size of glaciers is remote sensing best?
Large ones
26
What is SfM?
Structure from motion
27
What does SfM do?
Take photos and piece them together to make a model of the surface
28
Why is SfM useful?
Can get detailed info without having to be on the glacier itself
29
Why are tropical glaciers found in tropical areas?
Relics from past colder climates
30
Where is the vast majority of tropical glaciers?
The Andes but also high elevations in Indonesia and some (very little in Africa)
31
What will happen to tropical glaciers?
They will shrink and disappear
32
What percentage of the tropical glaciers have shrunk since 1970s?
Up to 50% of their surface area has gone since the 1970s
33
What is precipitation like in the inner tropics?
Similar precipitation all year round
34
What is precipitation like in the outer tropics?
Dry season May to September
| Wet season is October to March
35
What type of weather is good for glaciers and why?
Wet snowy years
| Albedo- more reflective
36
Why are glaciers in the outer tropics important?
Demand for water is needed all year round so glaciers act as a baseline throughout the wet and dry seasons
37
What is the mass balance of tropical glaciers due to?
Temperature and precipitation
38
When does snow and rain fall onto the tropical glaciers?
In the summer
39
When does melt occur on tropical glaciers?
In the summer
40
Give a location where debris covered glaciers are present
Himalayas
41
Where are the rock debris on debris covered glaciers from?
Surrounding hillslopes
42
What is an added danger as a result of debris on glaciers?
Avalanches and landslides
43
What features of the debris can have an effect on melting
Colour and packing
44
What does thick debris do to the ice?
Thick debris insulates the ice and reduces melt
45
What is the critical thickness?
This is the balance between thick and thin debris
46
What does a thin layer of debris do to the melt rate?
It increases it
47
Where on a glacier is melt highest?
Melt is highest at lower elevations
48
Where on a glacier is melt lowest?
At higher elevations because it is colder
49
What causes an inverted mass balance?
Melt being higher at lower elevations and lower at higher elevations
50
In what sort of areas are debris covered glaciers located that could cause risks?
They are at the top of catchments for highly populated areas
51
What is a feature of debris covered glaciers?
Ponds form on the glacier surface as water collects at the front of the glacier bordered by the moraines
52
What is are two issues with ponds on the glaciers?
They are dark and therefore increase the melt rate
| Lakes can easily burst leading to catastrophic effects
53
Can sea ice contribute to sea level rise?
No
54
What is UAV?
Unmanned Aerial Vehicle
55
What do UAV surveys do?
Map the surface
56
What do ground penetrating radars do?
They go down through the ice to measure the thickness
57
Why is it important to know ice thickness?
To know how long the glacier will last
58
What are ice cliffs?
Areas of ice with string melting
59
What do moraines show?
Previous extent of the glacier
60
What are moraines made of?
Unconsolidated, weak sediment
61
How do glacier lakes burst?
Through moraines
62
When do glaciers flow?
On longer time scales
63
In which direction do glaciers flow?
Downhill
| From the accumulation zone to the ablation zone
64
Why do glacial crevasses form?
When the ice flows too quickly and fractures
65
Where is the fastest ice flow?
In the middle
66
Why does the ice at the edges and the bottom flow smaller?
Friction
67
What is the velocity at the top of the glacier?
0
68
In which direction does the ice in the glacier flow?
Top to bottom
69
What are 3 methods of ice flow?
Internal deformation
Basal sliding
Deformation of sediment under the glacier
70
In what type of glacier does internal deformation occur?
All glaciers
71
What is internal deformation?
Ice deforming under its own weight
72
How does internal deformation occur?
Ice moves along boundaries of grains and recrystalises
73
What factors affect the rate of deformation? (5)
Slope
Thickness
Temperature
Water content and crystal properties
74
What does basal shear stress do?
It drives glacier flow
75
What is basal shear stress caused by?
Density of ice and gravitational acceleration which are constant
Ice thickness
Ice surface slope
76
What effect does ice thickness have on the movement of the glacier?
Thicker ice = faster movement- faster deformation
77
What effect does ice surface slope have on glacier movement?
Steeper slope = faster movement - faster deformation
78
What is ice thickness?
How much ice there is
79
What does Glen's flow law give?
The amount of deformation for a given amount of stress
80
What is deformation also known as?
Creep
81
How easily does warm ice deform?
Ice deforms easily when warm
82
What type of glaciers are polar glaciers?
Cold- based
83
What type of glaciers are temperate glaciers?
Warm- based
84
What is PMP?
Pressure Melt Point
85
What is the melt point dependent on?
Pressure
| Temperature
86
Why can liquid water be present at colder temperatures?
Because of pressure
87
What is meant by cold-based glaciers?
They don't reach PMP
88
What is meant by warm-based glaciers?
They reach PMP
89
In which type of glacier does basal sliding and sediment deformation occur?
Warm-based glaciers
90
What are 6 factors that affect the PMP?
```
Ice thickness
Accumulation rate
Ice surface temperature
Meltwater
Geothermal heat
Friction
```
91
What are polythermal glaciers?
They have some warm ice and some cold ice so some parts are at the PMP but others aren't
92
In what two ways can basal sliding occur?
Enhanced basal creep
| Regelation
93
What is enhanced basal creep?
Ice hits an obstacle which increases the stress, causing the ice to deform more quickly around the obstacle
94
What is regelation?
This involves transfer of heat
| Ice heats an obstacle, causing it to melt. Once the obstacle has been overcome, the ice refreezes again
95
What is sediment deformation?
Material at the bottom of glaciers is weak, watery and unconsolidated which allows the glacier to slide along on top
96
What is glacial hydrology?
This is the movement of water through the glacier
97
What is supraglacial water movement?
On top of the glacier e.g.streams
98
What is englacial water movement?
Within the glacier (through cravasses and moulins)
99
What is subglacial water movement?
Beneath the glacier
100
What is proglacial water movement?
In front of the glacier
101
What does glacial hydrology apply to?
All glaciers
102
What is sheet flow?
A thin film of water at the bottom of the glacier
103
What is channelised flow?
Channels of water that remove water efficiently by having an aborescent network
104
What are the two types of channelised flow?
R channels
| N channels
105
Where are R channels?
Cut up into the ice
106
Where are the N channels?
In the sediment
107
What are linked cavities?
These are pockets under the glacier that are linked. Quite inefficient and hard to get the water out
108
What are canals?
Networks cut down into the rock or sediment under the glacier
109
Why is glacial hydrology important?
It has an effect on the melt rate and glacial flow
110
What does the water interact with, making glacial hydrology important?
It interacts with the melt rate
111
What is warmer, the ice or the water?
The water
112
For channelised flow, is the effect of the ice or water stronger?
The effect of water is stronger which means that more water melts the ice as it is over a small surface area and causes the ice to expand, this leads to a low pressure
113
What happens in linked cavities?
Water can't expand the cavities quickly enough, causing the cavities to raise up and increases the pressure
114
By how much can cavities raise up?
Cm to M
115
What effect do linked cavities have on ice flow?
Increased speed of ice flow
