Cryosphere 1- introduction Flashcards
What are the main general parts of the atmosphere?
Snow
Sea ice
Ice shelves
Ice sheets
Glaciers and ice caps
Permafrost continuous
Permafrost discontinuous, isolated
What are the timescales for lifetime/ rate of change in different parts of the cryosphere?
Snow - day to month (seasonal)
River and lake ice - seasonal
Glaciers and ice caps- seasonal to century
Frozen ground- daily to millennium
Ice sheet margin- monthly
Ice shelves- yearly
Ice sheet- millennium
What are the 2 present day ice sheets in the cryosphere?
Greenland
Antarctic
Where can permafrost be found?
Siberia
Northern Russia
Northern north America
What is permafrost?
permanently frozen ground at a certain depth
What is the active layer when considering permafrost?
the top most layers that will experience seasonal freezing and thawing
What can lead to the changing of lifespan for different parts of the crysosphere?
climate forcing - warming, cooling, changing weather patterns
What affects how quickly a reservoir will react with the environment?
the size of reservoir
What would happen to sea level if the Greenland ice sheet instantly melted?
would rise by around 8m
What would happen to sea level if the Antarctic shelf melted instantly?
50 m rise
What is the last largest ice sheet which is no longer present?
the Laurentide
Where was the Laurentide ice sheet located?
North America extended past New York and Mid-west to Rockies
How has ppm of CO2 changed over time? (numbers)
present day - 420
Pre Industrial revolution - 280
Last glacial maximum - 180
How much lower was sea level 22 Ka?
180m lower at max ice sheet size
120m average for ice age (last 80 Ka)
Why was sea level lower in the last glacial maximum?
the water becomes locked in ice sheets
What happens when a continental ice sheet becomes large enough?
pushes to edge of continental land then land dips down leading ice to float on top of the water
What does ice that floats on water form? (when still attached to main ice sheet)
Ice shelves
What is ice berg calving?
ice berg creation this is when ice breaks off from the edge of the ice shelf
What will the stability of floating ice generally be like?
Inherently unstable
What is buttressing with ice shelves?
how the ice shelf interacts with the topography beneath it especially high points
What can happen to ice contact with underlying topography is there is any rise in sea level?
ice lifted off these points causing fractures and breaks increasing melting risk from both sides ocean below and atmosphere above
Why are strong Katabatic winds present in the Antarctic?
due to change in altitude and temperature regional density currents are created
What is the effect of the strong Katabatic winds on the ice shelfs and ice margin environment?
push sea ice away from ice shelf
creating an open water area
How do katabatic winds lead to upwelling?
winds create current which pushes surface water away by wind meaning deep nutrient rich water rises to take place
What do ice streams do to the energy in ice sheets?
focus energy allowing movement of ice in plastic form
Act as river system bringing ice mass to edge
When did the Larsen B ice shelf break up?
98-01
What were the stages that lead to the break up of Larsen B?
Cracks appeared which filled with meltwater leading to huge calving event (explosion/ shattering of shelf)
What problems arise form large ice shelves like Larsen B breaking up?
expose land ice behind making calving and melt more likely which can significantly affect sea level
What are the 2 main types of mountain glacier?
Cirque
Valley
What is a cirque?
circular bowl shape cut into mountain side
What is an arete?
when two headwalls of cirque erode back to back creating a knife edge ridge
What can lead to the formation of a pyramidal peak?
3 or more cirques erode back to back creating a steep pointed peak
What is the transition of mountain glaciers like?
Cirque will flow into a small valley glacier which will in turn flow into the main valley glacier
What is an examples of a valley glacier?
Franz Josef New Zealand
What will valley glaciers do to the surrounding valley?
erode and smooth it down creating a U-shaped valley
What do U shaped valleys provide a visual reminder of in the UK?
Glaciated past of the British isles
What is a piedmont glacier?
when the valley ends and the glacier flows into an open lowland area it will spread out showing how glaciers can be plastic (weight and heat)
What is an example of a piedmont glacier?
elephant foot glacier Greenland
What is a nunatak?
when some of the mountainous topography sticks out the top of the glacier
How can you tell nunataks from the surrounding rock?
as they lie above the glacial erosivity line they are instead affected by freeze thaw for will be weak/ easier to break with hammer
How much of fresh snow is air? (first stage glacial ice formation)
90%
What will happen to fresh snow with continual compaction?
it will transition into firmer more dense layers until glacial ice is formed
How much air is in granular ice? (2nd stage of glacial ice formation)
50%
How much air is in firn? (3rd stage og glacial ice formation)
20-30%
How much air/ air bubbles are present in glacial ice?
20%
At what rate does Greenland ice accumulate?
50cm yr-1
At what rate does Antarctica ice accumulate?
5cm yr-1
How can seasonal variation be seen in ice cores?
will be a darker summer layer and lighter winter layer which form one year
What is the important factor that can be measured in ice cores?
The gas bubbles they contain can be radiometrically dated to used to analyse past climate composition
What is an archive?
record of information (not how stored just where)
What are ice archives key evidence of the connection between in?
the atmosphere
What past variables can be found through ice cores?
Temp
CO2
Dust
How might the Milankovitch cycles link to the saw tooth pattern of past temperature?
Cooler interglacial 100 Ka cycle maybe linked to eccentricity
warmer interglacial 40 Ka time scale maybe linked to obliquity
20 Ka peaks in these period procession
What was pre-industrial CO2 PPM like?
180-280ppm 100ppm range due to sheet shift and sea level change
Why is dust concentration typically higher in glacial periods?
due to colder air which can hold less moisture/ water vapour- dry atmosphere- dust production
What is glacial mass balance?
the balance between input and output from a glacier
What is the zone of accumulation?
area of added mass to a glacier accumulation greater than ablation
Usually lighter due to fresh snow
What is the zone of ablation?
greater ablation than accumulation
Darker/ dirty due to material present
Where loss of glacial mass occurs
How do glaciers move?
Combination of 3 factors:
1&2) internal flow in solid ice
3) Sliding along the base
What type of glacier is internal flow more common in?
cold based glaciers as the ice is stuck to the bedrock
What basic physics is internal flow defined by?
thickness
density
acceleration
sin/ angle of slope
What counteracts internal flow?
friction
How do warm based glaciers predominantly move?
basal slip where water acts as lubrication between rock and ice
(meltwater produced as PMP lowers melt temp slightly)
What temp of ice will cold glaciers be made of?
only cold ice which is very strong and well below freezing point
What will warm glacial ice co-exist with?
water at pressure melting point
What is pressure melting point?
when the melting point is lowered under a column of ice
What temp of ice are temperate glaciers made of?
only warm ice
apart from top 10-15m in winter
What are polythermal glaciers?
they have both warm and cold ice
What allows water to move around the glacial system?
complex plumbing system of supra and sub glacial streams combined with moulins and supraglacial ponds
What is the problem with the formation of melt-ponds in the supraglacial environment?
Darker low albedo go through 90 to 10% reflected
feeds positive feedback
What is the problem with meltwater ponds and moulin production?
Meltwater can sink and erode its way through the glacial ice creating a hole/ channel to the sub-glacial environment allowing vast amounts of meltwater to base lifting glacier making movement easier and shifting more mass to ablation zone.
How can deforming beds be a way of glacial movement?
if sediment under glacier instead of rock they will deform faster so less obstruction to movement
