1.2- Global Water Cycle Flashcards
What are the processes involved in transferring water within global water cycle?
1- precipitation= transfers water from atmosphere back to Earth’s surface
2- evaporation= water transferred back to atmosphere
3- water may INFILTRATE the ground or PERCOLATE slowly through the rocks as GROUNDWATER FLOW
Water is stored within 4 physical systems:
- lithosphere (lands)
- hydrosphere (liquid water)
- cryosphere (frozen water- snow and ice)
- atmosphere (air)
Liquid water dominates with about 98% of water in liquid form, predominantly in oceans
Of all the water on plant Earth what % is oceans and what % is freshwater?
- oceans =97%
- freshwater= 3%
Of the 3% of freshwater on Earth, what % is ice caps and glaciers, ground water and % easily accessible freshwater?
- ice caps and glaciers= 79%
- groundwater= 20%
- easily accessible surface freshwater=1%
Of the 1% of easily accessible surface freshwater what % is lakes, soil moisture, atmospheric water vapour, rivers and water within living organisms?
- lakes = over 50%
- soil moisture= around 40%
- atmospheric water vapour=8%
- rivers=1%
- water within living organisms= less than 1%
Regarding global distribution and size, what are the major water stores?
- cryospheric water
- oceanic water
- terrestrial water
- atmospheric water
Regarding oceanic water, oceans dominante the amount of available water and covers approximately __% of the planet’s surface
72
Oceanic water tastes salty because
It contains dissolved salts that allow it to stay liquid water below 0 degrees Celsius- they are alkaline with a PH of 8.4 but PH steadily falling however due to increase in atmospheric carbon
Major oceans include:
- Atlantic
- Arctic
- Indian
- Pacific
- Southern
What are the 5 main locations of cryospheric water?
1- sea ice 2- ice sheet 3- ice caps 4- Alpine glaciers e.g. mer de Glace, France 5- permafrost e.g. Alaska North slope
Discuss sea ice
- much of Artic ocean= frozen and the amount of which grows in summer and shrinks in winter
- same is true of waters surrounding Antarctica
- sea ice forms when water in oceans is cooled below freezing
- sea ice does not raise sea level when it melts because it is frozen from ocean water
Discuss ice sheets
- mass of glacial ice extending more than 50,000km squared e.g. Antarctic and Greenland ice sheets
- ice sheets form in areas where snow falls in winter and doesn’t entirely melt in summer
- ice sheets contain vast amounts of frozen water= if Antarctic Ice sheet melted, scientists estimated sea levels would rise by 60m
Discuss ice caps
- thick layer of ice on land smaller than 50,000km squared
- usually found in mountainous areas such as Himalayas and Andes
- major source for many glaciers
Discuss alpine glaciers
- thick masses of ice found in deep valleys or in upland hollows
- many feed major rivers such as 15,000 Himalayan glaciers support rivers such as Indus and Ganges that are the lifeline of millions of people in south east Asia
Discuss permafrost
- permanently frozen group that remains at or below 0 degrees Celsius for at least 2 consecutive years
- covers 1/4 of Earth’s surface including Northern Canada, Alaska and Siberia
Terrestrial water falls into 4 classes:
1- surface water
2- ground water
3- soil water
4- biological water
Discuss surface water
- free-flowing water of rivers, lakes and ponds
- rivers= both transfer and store of water
- make up minute % of all global water
- Amazon= largest river by distance of water in the world and accounts for approx 1/5 of world’s total river flow
- lakes= mostly lie in Northern hemisphere at high latitudes- Finland and Canada have high number of lakes
- largest lake by area = Caspian Sea
Regarding surface water, also discuss wetlands
- wetlands= areas of marsh, fen or peatland whether there is a dominance of vegetation areas where water covers soil
- found on every continent minus Antarctica
- world’s largest wetland system = Pantanal of South America
- it is a complex system of marshlands and lagoons and provides economic benefits by being huge areas for water purification and water supply
- wetland= main ecosystem in Arctic and stores enormous quantities of greenhouse gases and critical for biodiversity
Discuss groundwater
- groundwater= water that collects underground in pore spaces of rock
- just over 20% of all freshwater= stored in rocks deep below ground surface forming vast underground reservoirs called aquifers
- these sources= crucial for sustaining civilisation across the world
- depth at which rock becomes completely saturated with water = water table
- level of water table rises in response to:
Groundwater flow, abstraction by people, or recharge - groundwater flow eventually flows to the surface and can form wetlands
- amount of available groundwater = rapidly reducing due to extensive extraction for use in irrigation agriculture land in dry areas
Discuss soil water
- affects run-off and water quality
Discuss biological water
- biological water= all water stored in all biomass and varies depending on type and amount of vegetation
- e.g. areas of dense rainforest store much more water than deserts
- if vegetation is destroyed, store of water in trunk and branches lost to the atmosphere
Discuss atmospheric water
- exists in all 3 states (gas, liquid, solid)
- most common atmospheric water exists as a gas: water vapour (WV)
- WV absorbs, reflects and scatters incoming solar radiation keeping the atmosphere at a temperature that can maintain life
- amount of WV that can be held in the air depends on its temperature- cold air cannot hold as much WV as warm air= poles quite dry whereas air over tropics= fairly humid
- small increase in WV will lead to increase in global temperatures leading to further rise in global WV level, thus further enhancing atmospheric warming = POSITIVE FEEDBACK
- clouds= visible mass of water droplets or ice crystals suspended in the atmosphere
- cloud formation is the result of air in lower atmosphere becoming saturated
- when cloud droplets grow they can eventually fall as rain
What are the key processes driving change in the magnitude of these stores over time and space?
1- evapo-transpiration
2- condensation
3- runoff generation
4- cryospheric processes
What is the approximate residence time for following stores: 1- groundwater 2- oceans 3- soil moisture 4- atmospheric moisture
1= approx 10,000 years 2= approx 4000 years 3= 2-50 weeks 4= 10 days
What is evaporation?
Transfer of water from a liquid state to a gaseous state (water vapour) and can occur from open water or wet surfaces- vast majority occurs from oceans-> atmosphere (makes sense as oceans cover approx 72% of planet’s surface)