Summary notes of A-level Geography AQA Water and Carbon Topic
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Course
Water and Carbon Cycle
Institution
AQA
This document is a summary of all the content of this topic, accept for key case studies. This document is written using class notes, own research and textbook.
Water and Carbon Cycle Notes
Systems
A system – a system is a set of interrelated components working together towards a process.
Input – addition of energy/ matter into a system
Output- removal of energy/matter from a system
Store (component) – the parts of a system where energy/matter is stored or transformed.
Flow (transfer) – links between the stores within the system and movement of energy/matter
Closed system – energy can come in and out, but matter cannot e.g. the Earth- sun’s energy can
come in and out but nothing leaves the earth’s system.
Open system – matter and energy can come in and out of the system (often smaller scale like
drainage basins)
Isolated system – no interaction with anything outside system boundary
Dynamic equilibrium – inputs balance outputs
Feedback loops – occur when a system loses and attempts to regain its balance.
Positive feedback – makes situation worse, effects of an action are amplified/ multiplied by
subsequent knock-on effects. E.g. building on floodplain
Negative feedback – puts system back into equilibrium, effects of an action are nullified by the
subsequent knock-on effects. E.g. flood defences can put drainage basin back to equilibrium.
Positive feedback example:
Drainage Basin – Houston’s urban sprawl – building on flood plains meant less salt marshes and
therefore more flooding etc
,The water cycle.
Global distribution and size of major stores of water
Hydrosphere (liquid water)
Water on earth is estimated at 1.338 ×109 km 3
Ocean water (saline) -> 97%
Fresh water (cryosphere, terrestrial, atmosphere) -> 3% (of which 69% is in the cryosphere and 30%
is groundwater)
Ocean water:
72% of planet’s surface is ocean/seas
Has a lower freezing point as its saline
Alkaline (pH of 8.14)
pH is falling due to increase CO2 -> acidification.
Ocean currents play a huge part in the distribution of heat across the planet.
Desalination can be used to make potable water from ocean water.
Cryosphere (ice)
Water in solid form:
Sea ice – Arctic Ocean and waters around Antarctica.
Ice shelf – platforms of ice that form where ice sheets and glaciers move out into the ocean e.g. In
Greenland, Antarctica, Alaska, Canada
Ice caps – often on top of mountains e.g. Himalayas
Ice sheets – large expanses of ice, e.g. in Greenland and Antarctica, cover more than 50,000 km2 of
land e.g. Greenland ice sheet
Glaciers – move downhill due to gravity, found in deep valleys and upland hollows e.g. the Rockies. A
loss in glaciers impacts those who rely on it as a water source and will cause short term flooding.
Permafrost – ground that remains at or below 0*c for at least 2 consecutive years. E.g. in Arctic
Continental shelf, ice free areas of Antarctic continent. Melting released methane and carbon
dioxide.
Terrestrial water
Water that is terrestrial is the most useful
Surface water:
Free-flowing water in rivers, ponds and lakes (rivers make up 0.0002% of earth’s water)
e.g. The Pantanal of South America is the world’s largest freshwater wetland
Canada has 32,000 lakes
Amazon is largest river by discharge
Groundwater:
Water collected in the pore spaces of rock
Lower level set at 4,000m deep
Soil water:
Water held in pore spaces of soil – saturated soil
Biological water:
Water stored in biomass which varies globally depending on density and type of vegetation cover –
dense forest has the most
Inputs via roots
Phytoplankton – hold 90% of ocean’s biomass and are sun harvesters
Atmospheric water
Water vapour is a greenhouse gas
Atmosphere is the superhighway used to move water around the globe
Evaporation and transpiration
Condense into clouds and winds move these clouds around the world
Positive feedback of warming temperatures -> more water vapour -> warmer temperatures
, Processes driving change in magnitude of these stores over time and space, including
flows and transfers:
Water in the atmosphere:
Evaporation – water changing to gas
Transpiration – loss of water from plants via their leaves
Sublimation – ice or snow transforms directly into water vapour without going through a liquid
phase (don’t melt)
Respiration – animals emit water through respiration
Evaporation:
When energy from solar radiation hits the surface of water or land and causes liquid water to change
state to gas.
Energy is in the form of latent heat and is either absorbed or released depending on the process.
Rate of evaporation depends on amount of solar energy, water availability, air humidity,
temperature of air
Transpiration is also important.
Evaporation uses latent heat energy and cools its surroundings.
Water stays in atmosphere for about 10 days
90% of atmospheric water is from evaporation and 10% is from transpiration
Condensation
Warm air can hold more moisture than cold air
As air rises it cools and its relative humidity increases.
Air is saturated when relative humidity is 100% this is called dew point, water vapour then
condenses onto a condensation nuclei and forms clouds.
Condensation releases latent heat
Happens due to:
Air temperature is reduced to dew point – when warm air passes over a cold surface, when
ground gets colder
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