WCC: Water Cycle - Global Distribution of Water Stores Flashcards
Where is cryospheric water stored?
Ice caps, permafrost, alpine glaciers, sea ice, ice sheets
Where is terrestrial water stored?
Surface water (wetlands, rivers, lakes), groundwater, biological water, soil water
Example of sea ice
Ross Ice Shelf
Example of ice caps
Icelandic ice cap
Example of ice sheets
Greenland ice sheet
Example of alpine glaciers
Mer de Glace, France
Example of permafrost
Alaska North Slope
Does sea ice raise the sea level when it melts?
No as it forms from ocean water
Which 2 ice sheets contain more than 99% of the freshwater on Earth?
Antarctic and Greenland ice sheets
How big is the Antarctic ice sheet?
14 million km^2, covering an area roughly the size of Mexico and the USA combined
How much would sea levels rise if the Greenland ice sheet melted and if the Antarctic ice sheet melted?
Greenland ice sheet - 6m
Antarctic ice sheet - 60m
Where are ice caps usually found?
Mountainous areas such as the Himalayas, the Rockies, the Andes and the Southern Alps of New Zealand
How much does the thickness of permafrost vary?
From 1m to over 1500m
How much of the Earth’s surface does permafrost cover?
Around 1/4, including vast areas of Northern Canada, Alaska and Siberia
What allows the ocean to stay as liquid water below 0C
Dissolved salts
What is the pH of the oceans?
8.4 - alkaline
Why is the pH of oceans steadily falling?
An increase in atmospheric carbon
What is the largest lake? What is its area?
The Caspian Sea at 78,000km^2
What is the deepest lake? Give data to support this
Lake Baikal in Siberia, mean depth 749m, deepest point 1637m
Global distribution of wetlands
Wetlands are found in every continent except Antarctica
What is the world’s largest freshwater wetland system?
the Pantanal of South America
How does the Pantanal provide economic benefits to South America?
It’s a huge area for water purification, climate stabilisation, water supply, flood abatement, and provides an extensive transport system
What ecosystem covers nearly 60% of the Arctic?
Wetlands
Where do aquifers most commonly form?
In rocks such as chalk and sandstone, which are porous and permeable
What is the water table?
The depth at which rock becomes completely saturated with water
What changes the level of the water table?
Groundwater flow, abstraction by people or recharge
What can soil water impact?
Weather and climate, run-off potential, flood control, oil erosion, reservoir management and water quality
Why is it dry over the poles and humid over the tropics?
Because cold air cannot hold as much water vapour
What are aquifers?
Vast underground reservoirs formed by water stored in rocks deep below the ground surface
Through which soil types is water easily transferred and through which soil types is it had for water to be transferred?
Easy - porous, sandy soils
Hard - clay
What is the water budget?
Soils capacity to store and transfer water
What are aquifers in the deserts called?
Fossil aquifers
Where do saline aquifers exist?
Where seawater had infiltrated into the rocks, often due to over-abstraction
What can shortages of water lead to?
Migration and famine
Name the 4 main physical systems that store water.
Atmosphere
Cryosphere
Hydrosphere
Lithosphere
Rank these 9 water stores by size: Rivers Soil water Atmosphere Oceans Living things Glaciers, ice caps, ice-sheets Swamps, marshes Lakes Groundwater
- Oceans
- Glaciers, ice caps, ice-sheets
- Groundwater
- Lakes
- Soil water
- Atmosphere
- Swamps, marshes
- Rivers
- Living things
What percentage of global water is saline water?
97.4%
Where is the majority of saline water stored?
Oceans
What percentage of global water is freshwater?
2.5%
What kind of water is needed to sustain life?
Freshwater
What percentage of freshwater is stored in the glaciers, ice caps and ice-sheets?
68.7%
What percentage of freshwater is stored as groundwater in aquifers?
30.1%
What percentage of freshwater is stored as surface water?
1.2%
What percentage of accessible surface water is stored in lakes?
52%
What percentage of accessible surface water is stored in rivers?
1%
Where do humans get a large proportion of water from?
Rivers
What percentage of the Earth’s surface do oceans cover?
72%
When does sea ice form?
When the oceans are cooled below freezing
What is an ice shelf?
A platform of sea ice formed where ice sheets and glaciers move out into the ocean
How is sea ice distributed globally?
Mainly in the Arctic ocean and waters surrounding Antarctica
How are ice shelves distributed globally?
They exist mostly in Antarctica and Greenland, and in the Arctic near Canada and Alaska
What are icebergs?
Chunks of ice that break off glaciers and ice shelves and drift into the ocean
When do icebergs raise sea level?
When they initially enter the water, but not when they melt
How big is the Greenland ice sheet?
1.7 million km^2, covering most of the island of Greenland
What is an ice sheet?
A mass of glacial land ice extending more than 50,000km^2
In what areas do ice sheets form?
Areas where snow that falls in winter does not melt entirely over the summer
How do ice sheets form?
Snow falls in winter and doesn’t entirely melt in summer. Over thousands of years, the layers of snow pile up into thick masses of ice. They grow thicker and denser as the weight of new snow and ice layers compresses the older layers.
In what way are ice sheets moving?
They are slowly flowing downhill under their own weight
What are ice streams?
Relatively fast-moving outlets of ice that occur where ice-sheets meet the coast, discharging ice and sediment from the ice sheet.
How do ice sheets remain stable?
By accumulating the same mass of snow as they lose to create a state of dynamic equilibrium, aided by ice streams.
What percentage of ice and sediment does the Antarctic Ice Sheet discharge through ice streams?
90%
How large are Antarctic ice streams?
U p to 50km wide, 2km thick and 100s of km long
What is sea ice?
Free-floating frozen ocean water that melts and refreezes throughout the year
What percentage of Antarctica is ice shelf?
11%
What percentage of evaporated water entering the water cycle is supplied by oceans?
90%
What are ice caps?
Thick layers of ice on land that are smaller than 50,000km^2
Describe the shape of an ice cap.
Usually dome-shaped and centred over the highest point in an upland area.
What are the major sources for many glaciers?
Ice caps
What is the name of Africa’s only remaining ice cap and where is it located?
The Furtwangler Glacier on Kilimanjaro
In what direction do ice caps flow?
Outwards
What are alpine glaciers?
Thick masses of ice found in deep valleys or upland hollows
When do glaciers form?
When snow remains in one location long enough to transform into ice
What percentage of Earth’s total land area is covered by glaciers?
10%
Why are glaciers particularly important in the Himalayas?
About 15,000 Himalayan glaciers form a unique reservoir which supports perennial rivers such as the Indus, Ganges and Brahmaputra which are the lifeline of millions of people living in SE Asia.
What is permafrost?
Ground that remains at or below 0C for at least 2 consecutive years
What are the 4 classes of terrestrial water?
Surface water
Groundwater
Soil water
Biological water
Give 3 types of surface water
Rivers
Lakes
Wetlands
What is the largest river by discharge?
The Amazon
How much of the world’s total river flow does the Amazon account for?
1/5
What are lakes?
Collections of freshwater found in hollows on the land surface of at least 2 hectares in area
Where do most of the world’s lakes lie?
In the Northern hemisphere at high latitudes
How many lakes does Canada have in total?
At least 2 million
Where in Asia is 20% of accessible surface freshwater stored?
Lake Baikal in Siberia
What percentage of accessible surface freshwater is stored in North America’s Great Lakes?
20%
What are wetlands?
‘Areas of marsh, fen peatland or water … where there is a dominance in vegetation’ - the Ramsar Convention
Why do wetlands vary so widely?
Because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation and human disturbance
Why are wetlands critical for global biodiversity?
They provide a unique environment that can support both aquatic and terrestrial species. The prolonged presence of water creates conditions that favour the growth of specially adapted plants. Water saturation determines the types of communities living in and on the soil.
Describe the Panatal
A complex system of marshlands, flood plains, lagoons and interconnected drainage lines, extending through millions of hectares of central-western Brazil, eastern Bolivia and eastern Paraguay.
What is groundwater?
Water that collects underground in the pore spaces of rock
Where does groundwater eventually flow to?
The surface
Where does natural discharge of groundwater often occur?
At springs or seeps
What can natural discharge of groundwater form?
Oases or wetlands
Why is the amount of available groundwater rapidly reducing?
Extensive extraction for use in irrigating agricultural land in dry areas
Describe the global distribution of fossil aquifers.
In the deserts of Africa, the Middle East, and Australasia
When were fossil aquifers formed?
Formed thousand of years ago when the climate in those regions was much wetter
What stops groundwater from continuing to percolate downwards?
Impermeable rock below e.g clay or granite, which has very limited water transfer
What forms where the water table is reaches the surface?
A lake or river
Within an aquifer system, where is water lost?
Within a discharge area such as a river or lake where the water table reaches the ground surface
Describe the global distribution of aquifers.
Globally, there are major aquifers in every continent. There are many in South America, Europe and Africa.
What is soil water?
Water held together with air in unsaturated upper weathered layers of the earth
What is biological water?
Water stored in all biomass
What happens to biological water stores if vegetation is destroyed?
The water is lost to the upper atmosphere
How many different states does atmospheric water exist in?
3 - gas, liquid, solid
What is the most common atmospheric water?
Water vapour
How does water vapour keep the atmosphere at a temperature that can maintain life?
It absorbs, reflects and scatters incoming solar radiation
How will a small increase in water vapour affect atmospheric temperatures?
Atmospheric temperatures will increase
What is cloud?
A visible mass of water droplets or ice crystals suspended in the atmosphere
What results in cloud formation?
Air in the lower atmosphere becoming saturated
Briefly describe the global distribution of water
Nearly all oceanic water. The majority of the small percentage of freshwater on Earth is stored in ice caps and glaciers. Most of the rest is groundwater. The small amount of surface freshwater is mainly stored in lakes and soil.
