Earth's Life Support Systems
Outline of Water and Carbon Cycles
IMPORTANCE OF WATER
• Water provides a medium which allows organic molecules to mix and form more complex structures
• Water also helps to create benign thermal conditions on Earth- oceans (71% of Earth's surface) moderate
temperatures by absorbing heat, storing it then releasing it slowly
• Clouds made up of tiny water droplets reflect around a fifth of incoming solar radiation
• Water vapour, a potent greenhouse gas, absorbs long-wave radiation from the Earth to help maintain
global temperatures 15 degrees celsius higher than they would be otherwise
• Water also makes up to 65-95% of all living organisms and is crucial to their growth, reproduction and
other metabolic functions- require water for photosynthesis, respiration and transpiration
◦ Plants also require water to maintain their rigidity and to transport mineral nutrients from the soil
• Water medium used for all chemical reactions in the body, including the circulation of oxygen and
nutrients
• Transpiration and sweating cooling process- evaporative cooling also achieved by panting
• Water also essential for economic activity- used to generate electricity, irrigate crops, provide recreational
facilities and satisfy public demand- also used in manufacturing
IMPORTANCE OF CARBON
• Biologically significant- large molecules of carbon atoms in proteins, carbs and nucleic acids
• Used as a economic resource- fossil fuels power the global economy, used in manufacturing and for
power
• Agricultural crops and forest trees also store large amounts of carbon
CLOSED/OPEN SYSTEMS
• Generally, the carbon and water cycles are regarded as open systems, looking at it at a global scale
• However, on a micro scale, materials do cross the system boundaries, hence it can be regarded as a
closed system
,The Water Cycle
STORES
Primary stores of water are:
◦ Oceans (97% of global water)
◦ Cryosphere/ice (2%)
◦ Groundwater (0.7%)
◦ Atmosphere (0.001%)
◦ Biosphere/Vegetation (0.00004%)
• Paradox regarding atmospheric store- explained by rapid flux of water into and out of the atmosphere
FLOWS/PROCESSES
1) Precipitation
◦ forms when vapour in the atmosphere cools to its dew point and condenses into tiny water droplets
or ice particles to form clouds- adiabatic lapse rate
◦ varies in type, intensity, duration and climate
2) Transpiration
◦ The diffusion of water vapour to the atmosphere from the stomata of plants
◦ Responsible for around 10% of moisture
◦ Influenced by temperature, wind spreed and water availability to plants
3) Condensation
◦ The phase change of vapour to liquid water, occurring when the air is cooled to its dew point through
adiabatic expansion and rises due to atmospheric instability- a critical temperature where the air
becomes saturated with vapour, resulting in condensation
◦ As a result, clouds form
◦ Cumuliform clouds- flat bases with considerable vertical development, often formed when air is
heated through contact with Earth's surface
◦ Stratiform clouds- layer clouds which develop where an air mass moves horizontally across a cooler
surface (advection)
◦ Cirrus clouds-form at high altitude, do not produce precipitation
◦ Condensation at or near the ground produces dew and fog, which deposit large amounts of moisture
on vegetation
, 4) Evaporation
◦ The phase change of liquid water to vapour
◦ Main pathway by which water enters the atmosphere
◦ Heat required to break the molecular bonds of water
◦ Water absorbs heat energy and is released later in condensation, allowing huge quantities of heat to
be transferred globally
5) Interception
◦ When vegetation stops a proportion of precipitation, storing it temporarily on branches, leaves and
stems- eventually either evaporates (interception loss) or falls to the ground
◦ Factors that affect interception loss:
‣ Interception storage capacity
‣ Wind Speed
‣ Vegetation type
‣ Tree species
6) Infiltration, Throughflow, Groundwater Flow and Run-off
◦ If water falls to the ground and doesn't enter storage, it follows one of two flow paths to rivers or
oceans:
‣ Infiltration by gravity into the soil, followed by through flow
‣ Surface run-off
◦ Saturated Overland Flow- when the soil is saturated and reaches its infiltration capacity, water is
forced to travel by overland flow
◦ If soils are underlain by permeable rock or percolates underground, it will migrate slowly through the
rock pores and joints through groundwater flow
◦ Recharge may occur during Winter months, leading to a rise in the water table
7) Cryospheric Process/Ablation
◦ Ablation- the loss of ice from snow, ice sheets and glaciers due to a combination of melting,
evaporation and sublimation
◦ Meltwater is an important component of river flow in high latitudes and mountain catchments
Outline of Water and Carbon Cycles
IMPORTANCE OF WATER
• Water provides a medium which allows organic molecules to mix and form more complex structures
• Water also helps to create benign thermal conditions on Earth- oceans (71% of Earth's surface) moderate
temperatures by absorbing heat, storing it then releasing it slowly
• Clouds made up of tiny water droplets reflect around a fifth of incoming solar radiation
• Water vapour, a potent greenhouse gas, absorbs long-wave radiation from the Earth to help maintain
global temperatures 15 degrees celsius higher than they would be otherwise
• Water also makes up to 65-95% of all living organisms and is crucial to their growth, reproduction and
other metabolic functions- require water for photosynthesis, respiration and transpiration
◦ Plants also require water to maintain their rigidity and to transport mineral nutrients from the soil
• Water medium used for all chemical reactions in the body, including the circulation of oxygen and
nutrients
• Transpiration and sweating cooling process- evaporative cooling also achieved by panting
• Water also essential for economic activity- used to generate electricity, irrigate crops, provide recreational
facilities and satisfy public demand- also used in manufacturing
IMPORTANCE OF CARBON
• Biologically significant- large molecules of carbon atoms in proteins, carbs and nucleic acids
• Used as a economic resource- fossil fuels power the global economy, used in manufacturing and for
power
• Agricultural crops and forest trees also store large amounts of carbon
CLOSED/OPEN SYSTEMS
• Generally, the carbon and water cycles are regarded as open systems, looking at it at a global scale
• However, on a micro scale, materials do cross the system boundaries, hence it can be regarded as a
closed system
,The Water Cycle
STORES
Primary stores of water are:
◦ Oceans (97% of global water)
◦ Cryosphere/ice (2%)
◦ Groundwater (0.7%)
◦ Atmosphere (0.001%)
◦ Biosphere/Vegetation (0.00004%)
• Paradox regarding atmospheric store- explained by rapid flux of water into and out of the atmosphere
FLOWS/PROCESSES
1) Precipitation
◦ forms when vapour in the atmosphere cools to its dew point and condenses into tiny water droplets
or ice particles to form clouds- adiabatic lapse rate
◦ varies in type, intensity, duration and climate
2) Transpiration
◦ The diffusion of water vapour to the atmosphere from the stomata of plants
◦ Responsible for around 10% of moisture
◦ Influenced by temperature, wind spreed and water availability to plants
3) Condensation
◦ The phase change of vapour to liquid water, occurring when the air is cooled to its dew point through
adiabatic expansion and rises due to atmospheric instability- a critical temperature where the air
becomes saturated with vapour, resulting in condensation
◦ As a result, clouds form
◦ Cumuliform clouds- flat bases with considerable vertical development, often formed when air is
heated through contact with Earth's surface
◦ Stratiform clouds- layer clouds which develop where an air mass moves horizontally across a cooler
surface (advection)
◦ Cirrus clouds-form at high altitude, do not produce precipitation
◦ Condensation at or near the ground produces dew and fog, which deposit large amounts of moisture
on vegetation
, 4) Evaporation
◦ The phase change of liquid water to vapour
◦ Main pathway by which water enters the atmosphere
◦ Heat required to break the molecular bonds of water
◦ Water absorbs heat energy and is released later in condensation, allowing huge quantities of heat to
be transferred globally
5) Interception
◦ When vegetation stops a proportion of precipitation, storing it temporarily on branches, leaves and
stems- eventually either evaporates (interception loss) or falls to the ground
◦ Factors that affect interception loss:
‣ Interception storage capacity
‣ Wind Speed
‣ Vegetation type
‣ Tree species
6) Infiltration, Throughflow, Groundwater Flow and Run-off
◦ If water falls to the ground and doesn't enter storage, it follows one of two flow paths to rivers or
oceans:
‣ Infiltration by gravity into the soil, followed by through flow
‣ Surface run-off
◦ Saturated Overland Flow- when the soil is saturated and reaches its infiltration capacity, water is
forced to travel by overland flow
◦ If soils are underlain by permeable rock or percolates underground, it will migrate slowly through the
rock pores and joints through groundwater flow
◦ Recharge may occur during Winter months, leading to a rise in the water table
7) Cryospheric Process/Ablation
◦ Ablation- the loss of ice from snow, ice sheets and glaciers due to a combination of melting,
evaporation and sublimation
◦ Meltwater is an important component of river flow in high latitudes and mountain catchments
