Systems
Systems are composed of:
● Inputs - Where matter or energy is added to the system
● Outputs - Where matter or energy leaves the system
● Stores - Where matter or energy builds up in the system
● Flows - Where matter or energy moves in the system
● Boundaries - Limits to the system (e.g. watershed)
Open systems are when systems receive inputs and transfer outputs of energy or matter with other systems. Closed systems are when energy inputs equal outputs.Dynamic equilibrium in a system is when inputs equal outputs despite changing conditions. Positive feedback occurs when a chain of events amplifies the impacts of the original event, whereas negative feedback refers to a chain of events that nullifies the impacts of the original event, leading to dynamic equilibrium.
On a local scale the carbon and water cycles are both open systems, but on a global scale, they are closed systems. Each of these systems contains flows/transfers, inputs, outputs and stores/components.
The Water Cycle: Local Scale
In a local drainage basin system, water may be lost as an output through evapotranspiration and runoff, but more water may be gained as an input through precipitation. As the inputs and outputs are not balanced, it is an open system.
Inputs:
● Precipitation
Outputs:
● Evapotranspiration - The combined return of water to the atmosphere from evaporation and transpiration (plants)
● Streamflow - Water that flows through streams and into the ocean or as tributaries to other rivers
Stores:
● Groundwater - Water stored in the pore spaces of rocks
● Soil Water
● Rivers
● Interception - Water stored temporarily by trees etc, before it reaches the ground
● Surface
Flows:
● Infiltration - Water moving from above ground into the soil.
● Percolation - Water moves from the ground or soil into porous rock or rock fractures.
● Throughflow - Flow of water through the soil
● Surface Runoff
● Groundwater Flow - Flow of water through the rocks
● Streamflow
● Stemflow - Flow of water that has been intercepted by plants or trees, down a stem, leaf, branch or other part of a plant
The water balance is used to express the process of water storage and transfer in a drainage basin system and uses the formula:
Precipitation = Total Runoff + Evapotranspiration +/- Storage
It is important to use the water balance in your answers and to know what the balance is affected by, as it could be applied to explain droughts or floods.
● Inputs - Where matter or energy is added to the system
● Outputs - Where matter or energy leaves the system
● Stores - Where matter or energy builds up in the system
● Flows - Where matter or energy moves in the system
● Boundaries - Limits to the system (e.g. watershed)
Open systems are when systems receive inputs and transfer outputs of energy or matter with other systems. Closed systems are when energy inputs equal outputs.Dynamic equilibrium in a system is when inputs equal outputs despite changing conditions. Positive feedback occurs when a chain of events amplifies the impacts of the original event, whereas negative feedback refers to a chain of events that nullifies the impacts of the original event, leading to dynamic equilibrium.
On a local scale the carbon and water cycles are both open systems, but on a global scale, they are closed systems. Each of these systems contains flows/transfers, inputs, outputs and stores/components.
The Water Cycle: Local Scale
In a local drainage basin system, water may be lost as an output through evapotranspiration and runoff, but more water may be gained as an input through precipitation. As the inputs and outputs are not balanced, it is an open system.
Inputs:
● Precipitation
Outputs:
● Evapotranspiration - The combined return of water to the atmosphere from evaporation and transpiration (plants)
● Streamflow - Water that flows through streams and into the ocean or as tributaries to other rivers
Stores:
● Groundwater - Water stored in the pore spaces of rocks
● Soil Water
● Rivers
● Interception - Water stored temporarily by trees etc, before it reaches the ground
● Surface
Flows:
● Infiltration - Water moving from above ground into the soil.
● Percolation - Water moves from the ground or soil into porous rock or rock fractures.
● Throughflow - Flow of water through the soil
● Surface Runoff
● Groundwater Flow - Flow of water through the rocks
● Streamflow
● Stemflow - Flow of water that has been intercepted by plants or trees, down a stem, leaf, branch or other part of a plant
The water balance is used to express the process of water storage and transfer in a drainage basin system and uses the formula:
Precipitation = Total Runoff + Evapotranspiration +/- Storage
It is important to use the water balance in your answers and to know what the balance is affected by, as it could be applied to explain droughts or floods.
The soil water budget shows the annual balance between inputs and outputs in the water cycle. The soil water budget also shows how inputs and outputs impact soil water storage and availability.
There is a surplus of water in the winter months, after recharge of soil water in autumn. Soil water is recharged in autumn because the inputs of precipitation exceed the outputs of evapotranspiration (because it rains more and it is cooler).
The water is utilised in spring and summer, when potential evapotranspiration of plants is highest due to warmer weather.
The stores are depleting when evapotranspiration is greater than precipitation. This can lead to a deficit of soil water.
Maximum storage of water in the soil is field capacity. The water budget is dependent on type, depth and permeability of the soil and bedrock.
There is a surplus of water in the winter months, after recharge of soil water in autumn. Soil water is recharged in autumn because the inputs of precipitation exceed the outputs of evapotranspiration (because it rains more and it is cooler).
The water is utilised in spring and summer, when potential evapotranspiration of plants is highest due to warmer weather.
The stores are depleting when evapotranspiration is greater than precipitation. This can lead to a deficit of soil water.
Maximum storage of water in the soil is field capacity. The water budget is dependent on type, depth and permeability of the soil and bedrock.
The Water Cycle: Global Scale
- Aquifers are underground water stores and on a global scale they are unevenly distributed.
- Shallow groundwater aquifers can store water for up to 200 years, but deeper fossil aquifers, formed during wetter climatic periods, may last for 10,000 years.
- From accumulation to ablation/calving, glaciers may store water for 20-100 years, which may feed lakes that store water for 50-100 years. - Seasonal snow cover and rivers, both store water for 2-6 months
- Soil water acts as a more temporary store, holding water for 1-2 months.
- Shallow groundwater aquifers can store water for up to 200 years, but deeper fossil aquifers, formed during wetter climatic periods, may last for 10,000 years.
- From accumulation to ablation/calving, glaciers may store water for 20-100 years, which may feed lakes that store water for 50-100 years. - Seasonal snow cover and rivers, both store water for 2-6 months
- Soil water acts as a more temporary store, holding water for 1-2 months.
The Water Cycle: Changes over Time
Natural Processes
Seasonal Changes:
● Less precipitation, more evaporation in summer because of higher temperatures
● Reduced flows in winter as water is stored as ice
● Reduced interception in winter, when deciduous trees lose their leaves
● Increased evapotranspiration in summer; deciduous trees have their leaves/higher temperatures
Human Impacts
Farming Practices:
● Ploughing breaks up the surface, increasing infiltration
● Arable farming (crops) can increase interception and evapotranspiration
● Pastoral (animal) farming compacts soil, reducing infiltration and increasing runoff
Land Use Change:
● Deforestation (e.g. for farming) reduces interception, evapotranspiration and but infiltration increases (dead plant material in forests usually prevents infiltration)
● Construction reduces infiltration and evapotranspiration, but increases runoff
Water Abstraction (water removed from stores for human use):
● This reduces the volume of water in surface stores (e.g. lakes).
● Water abstraction increases in dry seasons (e.g. water is needed for irrigation)
● Human abstraction from aquifers as an output to meet water demands is often greater than inputs to the aquifer, leading to a decline in global long-term water stores
Seasonal Changes:
● Less precipitation, more evaporation in summer because of higher temperatures
● Reduced flows in winter as water is stored as ice
● Reduced interception in winter, when deciduous trees lose their leaves
● Increased evapotranspiration in summer; deciduous trees have their leaves/higher temperatures
Human Impacts
Farming Practices:
● Ploughing breaks up the surface, increasing infiltration
● Arable farming (crops) can increase interception and evapotranspiration
● Pastoral (animal) farming compacts soil, reducing infiltration and increasing runoff
Land Use Change:
● Deforestation (e.g. for farming) reduces interception, evapotranspiration and but infiltration increases (dead plant material in forests usually prevents infiltration)
● Construction reduces infiltration and evapotranspiration, but increases runoff
Water Abstraction (water removed from stores for human use):
● This reduces the volume of water in surface stores (e.g. lakes).
● Water abstraction increases in dry seasons (e.g. water is needed for irrigation)
● Human abstraction from aquifers as an output to meet water demands is often greater than inputs to the aquifer, leading to a decline in global long-term water stores
Flood Hydrographs
Some of the factors which would increase surface runoff of a river and therefore act to create a flashy hydrograph are shown on the OS Map, and others are listed below:
the carbon cycle local scale
The carbon cycle occurs on a local scale in a plant, or sere such as the lithosere, which is a vegetation succession that occurs on bare rock. Over time a soil builds up on the rock from decaying organic matter. The climatic climax (final stage of a vegetation succession) is achieved when the ecosystem can develop no further. E.g. when a woodland is formed.
The carbon cycle global scale
Transfers:
●Photosynthesis - Living organisms convert Carbon Dioxide from the atmosphere and Water from the soil, into Oxygen and Glucose using Light Energy. This removes CO2 from the atmosphere
● Respiration - The opposite of photosynthesis
● Combustion (Burning fossil fuels, wildfires etc.) - Releases CO2 into the atmosphere
● Decomposition - When living organisms die, they are broken down by decomposers which respire, returning CO2 into the atmosphere. Some carbon is also returned to the soil
● Diffusion - The oceans can absorb CO2 from the atmosphere, but this harms aquatic life by causing coral bleaching
● Weathering and Erosion - Rock particles broken down and transferred to the ocean, where the carbon is used by marine organisms to create shells
● Burial and Compaction - Sea shell fragments become compacted over time to form limestone and organic matter may form fossil fuels
● Carbon Sequestration - Transfer of carbon from the atmosphere and can be bothnatural and artificial
●Photosynthesis - Living organisms convert Carbon Dioxide from the atmosphere and Water from the soil, into Oxygen and Glucose using Light Energy. This removes CO2 from the atmosphere
● Respiration - The opposite of photosynthesis
● Combustion (Burning fossil fuels, wildfires etc.) - Releases CO2 into the atmosphere
● Decomposition - When living organisms die, they are broken down by decomposers which respire, returning CO2 into the atmosphere. Some carbon is also returned to the soil
● Diffusion - The oceans can absorb CO2 from the atmosphere, but this harms aquatic life by causing coral bleaching
● Weathering and Erosion - Rock particles broken down and transferred to the ocean, where the carbon is used by marine organisms to create shells
● Burial and Compaction - Sea shell fragments become compacted over time to form limestone and organic matter may form fossil fuels
● Carbon Sequestration - Transfer of carbon from the atmosphere and can be bothnatural and artificial
Main Carbon Stores (In order of magnitude):
● Marine Sediments and Sedimentary Rocks - Lithosphere - Long-term
● Oceans - Hydrosphere - Dynamic
● Fossil Fuel Deposits - Lithosphere - Long-term but currently dynamic
● Soil Organic Matter - Lithosphere - Mid-term
● Atmosphere - Dynamic
● Terrestrial Plants - Biosphere - Mid-term but very dynamic
The lithosphere is the main store of carbon, with global stores unevenly distributed. For example, the oceans are larger in the southern-hemisphere, and storage in the biosphere mostly occurs on land. Terrestrial plant storage is focussed in the tropics and the northern hemisphere.
● Marine Sediments and Sedimentary Rocks - Lithosphere - Long-term
● Oceans - Hydrosphere - Dynamic
● Fossil Fuel Deposits - Lithosphere - Long-term but currently dynamic
● Soil Organic Matter - Lithosphere - Mid-term
● Atmosphere - Dynamic
● Terrestrial Plants - Biosphere - Mid-term but very dynamic
The lithosphere is the main store of carbon, with global stores unevenly distributed. For example, the oceans are larger in the southern-hemisphere, and storage in the biosphere mostly occurs on land. Terrestrial plant storage is focussed in the tropics and the northern hemisphere.
The carbon cycle - changes over time
Natural Processes
Wildfires: Transfer carbon from biosphere to atmosphere as CO2 is released through burning. Can encourage the growth of plants in the long term Volcanic Activity: Carbon stored within the earth is released during volcanic eruptions, mainly as CO2 gas
Human Impacts
Fossil Fuel Use - Combustion transfers CO2 to the atmosphere from a long-term carbon sink Deforestation - Often used to clear land for farming/housing, rapidly releases carbon stored in plants using slash and burn techniques and interrupting the forest carbon cycle
Farming Practices - Arable farming releases CO2 as animals respire. Ploughing can release CO2 stored in the soil. Farm machinery such as tractors may release CO2.
The Carbon Budget is the balance between carbon inputs and outputs to a store at any scale: E.g. The carbon budget in the atmosphere has inputs from respiration and combustion, but outputs including the oceans/photosynthesis
Carbon Source - A store that emits more carbon than it absorbs: E.g. a damaged rainforest
Carbon Sink - A store that absorbs more carbon than it emits: E.g. a virgin rainforest
Wildfires: Transfer carbon from biosphere to atmosphere as CO2 is released through burning. Can encourage the growth of plants in the long term Volcanic Activity: Carbon stored within the earth is released during volcanic eruptions, mainly as CO2 gas
Human Impacts
Fossil Fuel Use - Combustion transfers CO2 to the atmosphere from a long-term carbon sink Deforestation - Often used to clear land for farming/housing, rapidly releases carbon stored in plants using slash and burn techniques and interrupting the forest carbon cycle
Farming Practices - Arable farming releases CO2 as animals respire. Ploughing can release CO2 stored in the soil. Farm machinery such as tractors may release CO2.
The Carbon Budget is the balance between carbon inputs and outputs to a store at any scale: E.g. The carbon budget in the atmosphere has inputs from respiration and combustion, but outputs including the oceans/photosynthesis
Carbon Source - A store that emits more carbon than it absorbs: E.g. a damaged rainforest
Carbon Sink - A store that absorbs more carbon than it emits: E.g. a virgin rainforest
the enhanced greenhouse effect
The Enhanced Greenhouse Effect is the process that is currently causing global warming as abnormally high levels of greenhouse gases are being produced by humans, trapping radiation from the sun, causing global warming and leading to climate change. It is important that you discuss the Enhanced Greenhouse Effect when assessing human impacts on the global climate, not the Greenhouse Effect, which is a natural process
Impact of the Carbon Cycle on Regional Climates
Tropical Rainforests:
● High rates of photosynthesis and respiration in forests lead to greater humidity, cloud cover and precipitation
● Deforestation reduces photosynthesis and respiration, further reducing humidity and cloud cover and decreasing precipitation Oceans:
● Warmer oceans cause more plankton growth and through plankton chemical production, cause clouds to potentially form
● High rates of photosynthesis and respiration in forests lead to greater humidity, cloud cover and precipitation
● Deforestation reduces photosynthesis and respiration, further reducing humidity and cloud cover and decreasing precipitation Oceans:
● Warmer oceans cause more plankton growth and through plankton chemical production, cause clouds to potentially form
feedback loop
Positive Feedback:
● Wildfires are more likely in hotter and drier climates due to global warming, which release large quantities of CO2 into atmosphere, which in turn then increases the warming effect
● Ice reflects radiation from the sun, reducing surface warming. As sea temperatures rise and ice melts, the warming effect is amplified as there is less ice to reflect the radiation. Further melting occurs and the process continues
● Higher temperatures are thawing the permafrost releasing CO2 and methane (which has 20 times the warming effect of CO2), causing warming on a local and global scale. The higher temperatures cause more permafrost to melt, causing further gas releases and further warming
Negative Feedback:
● Increased photosynthesis by plants and rising global temperatures allows vegetation to grow in new areas, e.g. where permafrost has melted. New vegetation absorbs CO2 from the atmosphere, decreasing the warming effect
● Higher temperatures and more CO2 cause a greater carbon fertilisation in plants, so they absorb more CO2, reducing the levels of CO2 and the rates of warming and then the carbon fertilisation, if temperatures decline. The process repeats
● Phytoplankton photosynthesise to gain energy and warmer oceans and more sunlight due to climate change boost this and the production of a chemical by the plankton which causes cloud formation. Increased cloud cover decreases warming by the sun and more photosynthesis reduces CO2 levels, reducing the levels of warming. The plankton grow less quickly and less of the chemical is increased decreasing cloud cover. The cycle continues
● Wildfires are more likely in hotter and drier climates due to global warming, which release large quantities of CO2 into atmosphere, which in turn then increases the warming effect
● Ice reflects radiation from the sun, reducing surface warming. As sea temperatures rise and ice melts, the warming effect is amplified as there is less ice to reflect the radiation. Further melting occurs and the process continues
● Higher temperatures are thawing the permafrost releasing CO2 and methane (which has 20 times the warming effect of CO2), causing warming on a local and global scale. The higher temperatures cause more permafrost to melt, causing further gas releases and further warming
Negative Feedback:
● Increased photosynthesis by plants and rising global temperatures allows vegetation to grow in new areas, e.g. where permafrost has melted. New vegetation absorbs CO2 from the atmosphere, decreasing the warming effect
● Higher temperatures and more CO2 cause a greater carbon fertilisation in plants, so they absorb more CO2, reducing the levels of CO2 and the rates of warming and then the carbon fertilisation, if temperatures decline. The process repeats
● Phytoplankton photosynthesise to gain energy and warmer oceans and more sunlight due to climate change boost this and the production of a chemical by the plankton which causes cloud formation. Increased cloud cover decreases warming by the sun and more photosynthesis reduces CO2 levels, reducing the levels of warming. The plankton grow less quickly and less of the chemical is increased decreasing cloud cover. The cycle continues
Tropical Rainforests: Interrelationships between the Cycles
Natural Rainforest Water Cycle:
● Precipitation falls
● 75% intercepted by trees and through stem flow 35% reaches the ground and infiltrates the soil and another 35% is used by plants and through transpiration returns to the atmosphere
● 25% evaporates almost immediately and returns to the atmosphere
Deforested Rainforest Water Cycle:
● Precipitation falls
● Most reaches the ground immediately with little vegetation to intercept the rainfall, leading to high surface runoff, with higher flooding risk
● Less evapotranspiration, so the atmosphere is less humid and rainfall decreases
Natural Rainforest Carbon Cycle:
● Trees suited to humid and warm conditions, which promotes photosynthesis
● They absorb large amounts of oxygen from the atmosphere acting as an important carbon sink
● Decomposition and respiration releases CO2 back to the atmosphere and soil, where carbon is stored
Deforested Rainforest Carbon Cycle:
● Lack of trees so photosynthesis is reduced
● Fires to clear land leads to CO2 being released into the atmosphere. Forests become a carbon source instead of a carbon sink
● Lack of life until new plants grow
● Low rates of decomposition occurs in this environment
● Precipitation falls
● 75% intercepted by trees and through stem flow 35% reaches the ground and infiltrates the soil and another 35% is used by plants and through transpiration returns to the atmosphere
● 25% evaporates almost immediately and returns to the atmosphere
Deforested Rainforest Water Cycle:
● Precipitation falls
● Most reaches the ground immediately with little vegetation to intercept the rainfall, leading to high surface runoff, with higher flooding risk
● Less evapotranspiration, so the atmosphere is less humid and rainfall decreases
Natural Rainforest Carbon Cycle:
● Trees suited to humid and warm conditions, which promotes photosynthesis
● They absorb large amounts of oxygen from the atmosphere acting as an important carbon sink
● Decomposition and respiration releases CO2 back to the atmosphere and soil, where carbon is stored
Deforested Rainforest Carbon Cycle:
● Lack of trees so photosynthesis is reduced
● Fires to clear land leads to CO2 being released into the atmosphere. Forests become a carbon source instead of a carbon sink
● Lack of life until new plants grow
● Low rates of decomposition occurs in this environment
relationships between the two cycles
● Rain that forms over intact tropical rainforest may fall over deforested land due to wind, causing erosion, with soil and ash flowing into rivers, increasing the carbon content of rivers. The water leaves the rainforest cycle as an output through streamflow due to reduced interception and increased surface runoff
● Alternatively there is reduced rainfall in the intact forest, as there is less evapotranspiration in the deforested area, causing drought periods and the intact rainforest to deteriorate
● Deforestation on peatlands and the digging of drainage channels reduces water storage. The organic peat matter is no longer preserved underwater and decomposes quickly, releasing CO2 into the atmosphere. Weathering and erosion increase speeding up decomposition. There is a greater wildfire risk from the hotter temperatures
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● Blocking drainage ditches in peatland rainforests, helps restore the natural environment, by increasing soil water storage and decreasing runoff. This can raise the water table and decrease the flood risk. However, a managed forest is often less effective at sequestering CO2 than a virgin forest
● Alternatively there is reduced rainfall in the intact forest, as there is less evapotranspiration in the deforested area, causing drought periods and the intact rainforest to deteriorate
● Deforestation on peatlands and the digging of drainage channels reduces water storage. The organic peat matter is no longer preserved underwater and decomposes quickly, releasing CO2 into the atmosphere. Weathering and erosion increase speeding up decomposition. There is a greater wildfire risk from the hotter temperatures
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● Blocking drainage ditches in peatland rainforests, helps restore the natural environment, by increasing soil water storage and decreasing runoff. This can raise the water table and decrease the flood risk. However, a managed forest is often less effective at sequestering CO2 than a virgin forest
managing climate change
Global Intervention - Paris Climate Deal (COP21):
● Aim to limit global temperatures to 2°C above pre-industrial levels
● Support for developing countries
● Public interaction and awareness schemes
● Meet every 5 years to review and improve goals
Regional Intervention - EU 20-20-20:
● 20% reduction in GHG emissions and commitment to 20% of energy coming from renewable sources and 20% increase in energy efficiency by 2020
● EU has suggested it will increase its emissions reduction to 30% if major GHG producing countries also improve their targets National
Intervention - Climate Change Act 2008 UK:
● Legally binding target for the UK to reduce GHG emissions by 80% of 1990 levels by 2050 with a target of 26% by 2020 which has recently increased to 34%
● Created national carbon budgets and the Independent Committee on Climate Change to help the government and report on progress that is being made
Local Scale:
● Improving home insulation
● Recycling
● Using energy more wisely and use of smart meters and using public transport or car sharing schemes and calculating personal carbon footprints
● Aim to limit global temperatures to 2°C above pre-industrial levels
● Support for developing countries
● Public interaction and awareness schemes
● Meet every 5 years to review and improve goals
Regional Intervention - EU 20-20-20:
● 20% reduction in GHG emissions and commitment to 20% of energy coming from renewable sources and 20% increase in energy efficiency by 2020
● EU has suggested it will increase its emissions reduction to 30% if major GHG producing countries also improve their targets National
Intervention - Climate Change Act 2008 UK:
● Legally binding target for the UK to reduce GHG emissions by 80% of 1990 levels by 2050 with a target of 26% by 2020 which has recently increased to 34%
● Created national carbon budgets and the Independent Committee on Climate Change to help the government and report on progress that is being made
Local Scale:
● Improving home insulation
● Recycling
● Using energy more wisely and use of smart meters and using public transport or car sharing schemes and calculating personal carbon footprints
