Comprehensive revision notes and essay for the A-Level Geography Water and Carbon Cycles. Includes notes for both cycles including key essay themes, alongside one essay plan and an example A* essay.
- The water contained in the Earth’s oceans and seas but not including such inland
seas like the Caspian Sea
- There are five oceans: Pacific, Atlantic, Indian, Arctic and Southern
- They cover approx. 72% of the planets surface
- Only 5% of oceanic waters have been studied and explored
- Oceans have a high salinity to prevent them from freezing due to cold temperatures
- However with the increase in global warming the ocean’s salinity is decreasing as
more ice caps are melting therefore there is more fresh water which decreases the
concentration of the salinity of the oceans
Cryospheric Water
- The cryosphere is the forms of water on the Earth in a solid form
- There are 5 locations of cryospheric water: Sea Ice, Ice caps, ice sheets, alpine
glaciers, permafrost
- Sea Ice: sea ice forms when water in the oceans is cooled to temperatures below
freezing, sea ice does not raise sea levels when it melts because it forms ocean water
from when it was previously in water form
- Ice shelves are platforms of ice sheets and glaciers that move into the oceans –
icebergs are chunks of ice that break off glaciers and ice shelves that drift into the
oceans
- They raise sea level only when they leave land and push into the water but not when
they melt
- Ice Sheets: An ice sheet is glacial ice extending more than 50,000km 2 – the two main
ice sheets cover Greenland and Antarctica
- Together those ice sheets contain more than 99% of freshwater ice on Earth
,- Ice sheets form in areas where snow that falls in winter does not melt entirely over
summer – over thousands of years the layers of snow pile up into thick masses
growing thicker and denser as the weight of the new snow compresses the older
layers of ice
- Near the coast the ice moves through outlets called ice streams
- Ice sheets contain huge volumes of water – if the Antarctica sheet was to melt sea
level would rise by 60m
- Ice Caps: Thick layers of ice on land that are smaller than 50,000km
- They flow outwards covering almost everything in their path and becoming the
major source for glaciers
- Alpine Glaciers: Thick masses of ice found deep in valleys and hollows
- Most valley glaciers are fed by ice from ice caps or smaller corrie glaciers
- Permafrost: Ground that remains at or below 00C for at least two consecutive years,
permafrost can reach 1,500m in thickness
- Most of the permafrost that exists today was formed during cold glacial periods
- Subsea permafrost occurs at close to 00C over large areas of the Arctic continental
shelf where it formed during the previous glacial period when sea levels were lower
- Permafrost has began to melt as the climate warms, this melting is releasing large
amounts of carbon dioxide and methane which further damages the climate
- Terrestrial Water: 4 types: Surface, ground, soil and biological water
- Surface Water: Is the free flowing water of rivers and ponds/lakes
- Rivers act as a store and transfer of water, they transfer water from the
ground/atmosphere/soils to a store (wetland, lakes, oceans)
- Rivers make up very little of all water (0.0002%) with the Amazon producing the
largest discharge of water and accounts for approx. 1/5 of the world’s total river flow
- Lakes are collections of fresh water found in hollows on the land – a lake is defined
by being larger than two hectares in size and any body of water smaller than this is
classed as a pond
- The majority of lakes on Earth are fresh water and lie in the Northern Hemisphere at
higher latitudes
- The largest lake in the world is the Caspian Sea (78,200km) generally fresh water but
becomes more saline in the South where rivers flow into it
- Wetlands: Wetlands are areas of marsh, fen, peatland or water whether natural or
artificial or permanent or temporary with water that is flowing or static where there
is a dominance by vegetation
- They are areas where water covers the soil or is present either at/near the surface of
the soil all year but for varying times during the year
- Water saturation determines how the soil develops and the types of plant/animal
communities living there
- Wetlands help to support both aquatic and terrestrial species
, - Wetlands vary widely because of regional and local differences in soil, topography,
climate, hydrology, water chemistry and vegetation
- They are found on every continent except Antarctica
- Wetlands are the main ecosystem in the Arctic and cover nearly 60% total surface
area
- Groundwater: Water that collects underground in the pore spaces of rock
- The depth when soil pore spaces or fractures and voids in rock become completely
saturated with water is the water table
- Natural discharge occurs at springs and seeps and forms wetlands
- The volume of groundwater available is rapidly decreasing because of extensive
extraction for irrigation use in dry areas
- Soil Water: Water held together with air in unsaturated weathered layers of earth
- Soil water affects the weather, climate, run-off potential, flood control, soil erosion,
reservoirs and water quality
- Soil moisture is key in controlling the exchange of water and heat energy between
the land surface and atmosphere through evaporation and transpiration
- This results in soil water playing a key role in weather patterns and precipitation
- Biological Water: Constitutes the water stored in all biomass – this varies due to
vegetation type and cover (e.g – a rainforest will store more water than a desert)
- Trees take water up via roots (stored in trunk and branches) the water is lost as a
process of transpiration
- The storage helps provide a form of reservoir that maintains some climatic
environments
- If the vegetation is destroyed the water is lost to the atmosphere and the climate
can become more desert like
- Many plants have adapted to store water in large quantities
- Atmospheric Water: Exists in three states, most common is water vapour
- Water vapour absorbs, reflects and scatters incoming solar radiation keeping the
atmospheric temperature stable and able to maintain life
- The amount of vapour that can be held depends upon its temperature, cold air
cannot hold as much vapour as warm air resulting in the air over the poles being dry
whereas the tropics very humid
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