Physical - Carbon and Water Cycles

Question 1

The cycles as natural systems:

Concept of a system:

Answer 1

A system is the ‘big picture’ of inputs, outputs, transfers and stores, and its links to other systems. They have boundaries and structures and their components interlink and work together.

Question 2

The cycles as natural systems:

Concept of a system:

Answer 2

Open Systems:
These are systems where both matter and energy can be transferred from, across the boundary into the surrounding environment.

Question 3

The cycles as natural systems:

Concept of a system:

Answer 3

Closed systems:

A system where energy can be transferred, but not matter across boundaries.

Question 4

The cycles as natural systems:

Concept of a system:

Answer 4

The components of a system:
Elements: parts that make up the system (animals, atoms, etc)
Attributes: characteristics that can be measured (size, colour, quantity, etc)
Relationships: descriptions of how the elements and their attributes work together to carry out processes (photosynthesis).

Question 5

The cycles as natural systems:

Concept of a system:

Answer 5

Systems are affected by feedbacks:
1. If the inputs and outputs are balanced, the system is in equilibrium (flows and processes can continue, but consistently so there are no overall changes
2. But, in reality many very small variations in the inputs and outputs happen, and so they stay about equal on average. This is the system in dynamic equilibrium.
3. Larger longer term changes to the balance can cause a system to change and establish a new dynamic equilibrium (an overall shift).
4. These changes can cause positive/negative feedback loops
Positive: these amplify the changes (like the albedo loop)
Negative: these counteract the change and decrease its effects (plants decreasing CO2 in the atmosphere).

Question 6

The cycles as natural systems

Water cycle systems:

Answer 6

Water cycle systems:
The water cycle on a global scale is a closed system (as no water can come from space).
But on a local scale, it is an open system (a pond with water coming from precipitation, stores of plants, transfers of photosynthesis and groundwater flow, and outputs of evaporation).

Question 7

The cycles as natural systems:

Carbon cycle systems:

Answer 7

Carbon cycle systems:
On a global scale, the carbon cycle is closed (as no carbon matter comes from space).
But, on a local scale, it is open (e.g. a forest system, with inputs of lead fall, stores of rocks or trees, flows of photosynthesis, respiration and outputs of atmospheric emissions from forest fires).

Question 8

The cycles as natural systems:

Why is the cycling of water important:

Answer 8

Water:

1. It ensures that availability and quantity of water which is fundamental to life of Earth.
2. It facilitates key interactions between the land, ocean and atmosphere.
3. It creates water vapour, which is the most abundant greenhouse gas, and regulates global temperatures.
4. It allows scientists to predict the planet’s future and climate.

Question 9

The cycles as natural systems:

Why is the cycling of carbon important:

Answer 9

Carbon:

1. It ensures that carbon is transferred to where it needs to be. Carbon is what all life is made of and must be distributed by this cycling.
2. Carbon can form greenhouse gases that regulate the Earth’s temps.
3. The cycle facilitates vital interactions and distribution processes between the land, oceans and atmosphere.

Question 10

The cycles as natural systems:

The Earth as a system:

Answer 10

The Earth can be seen as a closed system (energy input from the sun and output to space, but no matter is transferred to space).

It has subsystems:

1. Cryosphere: all ice in the world (glacial landscapes, Antractica)
2. Lithosphere: the Earth’s crust and upper mantle (rocks and soils)
3. Biosphere: all living things on Earth (plants, animals)
4. Hydrosphere: all water on earth (liquid, solid, gas, saline, fresh) (this crosses over with the cryosphere).
5. Atmosphere: the gases between the Earth’s surface and space.

These are interlinked by the water and carbon cycles, matter and energy is transferred across to each system from another (this is a cascading system).

Question 11

The Carbon Cycle:

Global distribution and major global carbon stores:

Answer 11

Carbon is in both organic (living) and inorganic (non-living, rocks, gases, fossil fuels) stores.
Main global sotres:
1. Lithosphere: Over 99.9% of carbon is stored in sedimentary rocks, and 0.004% is stored in fossil fuels.
2. Hydrosphere: The oceans are the next biggest store (0.04%) with most being from deep oceans in the form of dissolved inorganic carbon (CO2 and other gases are dissolved in water). Some carbon is at the surface and is transferred into the atmosphere.
3. Atmosphere: Carbon is stored as CO2 or methane here (0.001% overall).
4. Biosphere: Carbon is stored in the tissues of living organisms (transferred to the lithosphere when they die and decay) (contains 0.004% overall).
5. Cryosphere: contains less than 0.01% of carbon. Most is in permafrost, where decomposing organic matter is frozen into the ground.

Question 12

The Carbon Cycle:

Carbon is transferred between stores:

Answer 12

The carbon cycle is a process where carbon is stored and transferred.
It is a closed system, but some carbon is locked away (sequestered) in long term stores (rocks, fossil fuels) and they effectively become inputs when they are released.

Question 13

The Carbon Cycle:

Main stores and flows of the cycle:

Answer 13

Stores:
- Soils, Earth’s crust (rocks), fossil fuels, vegetation, sediments, oceans, atmosphere.
Flows:
1. Inputs: photosynthesis, decomposition, sequestration, weathering, ocean uptake.
2. Outputs: volcanic eruptions, burning fossil fuels, combustion, respiration, ocean loss.

Question 14

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 14

Carbon flows between stores that force the change:
1. Photosynthesis:
This transfers between the atmosphere and biomass.
Plants use energy from the sun to change CO2 and water into glucose and oxygen, enabling growth.
Carbon is passed through the food chain and released through respiration and decomposition (longer term).

Question 15

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 15

2. Respiration:
   This transfers carbon from living organisms to the atmosphere.
   Plants and animals break down glucose for energy, releasing CO2 and methane into the atmosphere.

Question 16

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 16

3. Decomposition:
   This is the transfer of carbon from dead biomass to the atmosphere and soils.
   After death, bacteria and fungi break down the organic matter and release CO2 and methane.
   Some carbon is transferred into the soil in the form of humus (dark organic material).

Question 17

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 17

4. Combustion:
   This is the transfer of carbon in living, dead or decomposed biomass into the atmosphere, by burning.
   Wildfires are natural forms of this.

Question 18

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 18

5. Weathering
   Chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere
   Atmospheric carbon reacts with the water vapour to form acid rain. When this falls onto rocks, a chemical reaction occurs, dissolving the calcium in the rocks. This is washed into the sea and reacts with the CO2 in the water, forming Calcium Carbonate that forms the shells of sea creatures.

Question 19

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 19

6. Ocean uptake and loss:
   Uptake:
   CO2 is dissolved from the atmosphere to the ocean (through diffusion).
   It is also transferred to the oceans when it is taken up by marine organisms (through photosynthesis or respiration)
   Loss:
   Carbon is also transferred from the ocean to the atmosphere when carbon-rich water from deep oceans rise to the surface and release CO2.
   Or, when the marine organisms die and fall to the sea floor.

Question 20

The Carbon Cycle:

Carbon stores change in size over time due to carbon flows:

Answer 20

7. Sequestration:
   Carbon from the atmosphere is sequestered (captured and held) over time through photosynthesis of organisms.
   These form sedimentary rocks or fossil fuels over millions of years when the dead organic matter falls to the floor and is compacted.
   Carbon in fossil fuels is sequestered until we burn them (combustion).

Question 21

The Carbon Cycle:

Carbon flows happen over different time and spatial scales:

Answer 21

1. Temporal: Fast carbon flows quickly transfer carbon between sources (photosynthesis, respiration, combustion, decomposition).
   But, other flows are long term (like sequestration).
2. Spatial: These flows also depend on spatial scales. At a plant scale, respiration and photosynthesis are the main flows. At an ecosystem scale, flows like combustion and decomposition are also occurring. At a continental scale, all the flows happen.

Question 22

The Carbon Cycle:

Natural processes that change the cycle:

Answer 22

These alter the magnitude of the carbon stores on Earth:
1. Wildfires:
These rapidly transfer large amounts of carbon from biomass (trees or soil) to the atmosphere.
- In the short term, It decreases the amount of carbon removed from the atmosphere in the future, as there are less plants to photosynthesise.
- In the long term, fires can encourage the growth of new plants, which take in carbon from the atmosphere (photosynthesis).
- But, depending on the amount and type of regrowth of vegetation, fires can have a neutral effect on the amount of atmospheric carbon.

Question 23

The Carbon Cycle:

Natural processes that change the cycle:

Answer 23

2. Volcanic activity:
   Carbon stored in the Earth in magma is released in eruptions. The majority is transferred to the atmosphere as CO2.
   Recent eruptions have not changed the cycle too much, as they release less CO2 than humans emit, but there is potential for a larger eruption to shift the cycle’s equilibrium.

Question 24

The Carbon Cycle:

Natural processes that change the cycle:

Answer 24

3. Earth’s orbit:
   In the long term, Milankovitch cycles are a factor in naturally fluctuating CO2 levels in the atmosphere.
   These cycles change the shape of the orbit (its eccentricity), the angle that the Earth’s axis is tilted on its orbital plane (obliquity) and the direction the Earth’s spin axis is pointed (seasonality/precision).
   During glacial periods, the concentration of CO2 in the atmosphere has fluctuated from 180ppm to 280ppm, partly in response to Milankovitch cycles.

Question 25

The Carbon Cycle:

Natural processes that change the cycle:

Answer 25

4. Seasonal variations:
   There is more vegetation to remove carbon from the atmosphere in summer and spring months.
   Remember that the northern and Southern Hemispheres have different season times.

Question 26

The Carbon Cycle:

Human processes that change the cycle:

Answer 26

Humans are causing carbon flows from the lithosphere and biosphere to the atmosphere happen much faster than what is natural.
The main causes are:
1. Hydrocarbon extraction and use (fossil fuels):
Extracting and burning fossil fuels (combustion), releases CO2 into the atmosphere.
Without humans, this carbon would stay sequestered in the lithosphere.

Question 27

The Carbon Cycle:

Human processes that change the cycle:

Answer 27

2. Deforestation:
   Forests are cleared for agriculture, logging, or to make space for infrastructure.
   Clearance reduces the size of the forest as a carbon store.
   If the wood is burned, there is a large flow of carbon from the biosphere to the atmosphere, unnaturally.

Question 28

The Carbon Cycle:

Human processes that change the cycle:

Answer 28

3. Farming practices:
   Agricultural activities release carbon into the atmosphere:
   - Animals release CO2 and methane when they respire and digest food
   - Ploughing can release CO2 trapped in soils.
   - Growing rice releases a lot of methane
   Population growth has meant that food demand is increasing, and the mechanisation of farming too. All of this adds to CO2 in the atmosphere.

Question 29

The Carbon Cycle:

Human processes that change the cycle:

Answer 29

4. Land use changes:
   The change of land use from natural or agricultural to urban is a large source of carbon:
   - Vegetation is removed, reducing the biosphere store and their ability to remove atmospheric carbon.
   - Concrete production releases CO2.

Question 30

The Carbon Cycle:

Overall changes in the cycle:

Answer 30

1. Increasing atmospheric CO2 (more input):
   - Natural: volcanic eruptions and wildfires.
   - Human: burning fossil fuels, causing wildfires, increasing meat eating, climate change resulting in melting tundra (releasing methane and CO2).
2. Increasing atmospheric CO2 (less removal):
   - Natural: Glacial periods (less vegetation), interglacial periods (warmer oceans absorb less CO2), winter in northern hemisphere (biomass is less productive).
   - Human: Clearing natural vegetation for urban/farming or industrial uses, climate change resulting in warmer oceans.
3. Reducing atmospheric CO2 (less input):
   - Natural: Long-term natural reduction of volcanic activity and wildfires
   - Human: Carbon-capture schemes (artificial carbon sequestration).
4. Reducing atmospheric CO2 (more removal of carbon):
   - Natural: Glacial periods (cooler oceans absorb more CO2), interglacial periods (more vegetation), summers in northern hemisphere (more biomass productivity).
   - Human: Reforestation and afforestation projects

Question 31

The Carbon Cycle:

The slow carbon cycle:

Answer 31

This is a series of chemical reactions and tectonic activities. The carbon takes 100-200 million years to move between rocks, soils, oceans and the atmosphere in this cycle.
The movement of carbon to the lithosphere from the atmosphere starts with acid rain.

The factors that affect this are:
Weathering, carbon sequestration in oceans, volcanic eruptions and diffusion.

Question 32

The Carbon Cycle:

The fast carbon cycle:

Answer 32

This is largely the movement of carbon through lifeforms, or the biosphere. For example, photosynthesis.
This is much faster as organisms only live a short amount of time.

Factors that affect this are:
Photosynthesis, respiration, combustion, decomposition, burning fossil fuels, wildfires, land use change, farming practices, volcanic eruptions, natural sequestration (peat bogs, reforestation, ocean sequestration), and human sequestration (carb capture and storage).

Question 33

The Carbon Cycle:

The carbon budget:

Answer 33

This is the balance between inputs and outputs (the difference between them).
EX:
- In the atmosphere, carbon is inputted from volcanic eruptions, burning fossil fuels, respiration, ocean loss. It is outputted through photosynthesis, sequestration, decomposition, chemical weathering and ocean uptake.

This balance determines whether this subsystem is a carbon source or sink (it is a source when the outputs > inputs of carbon).

To calculate the carbon budget: outputs - inputs = budget.

Question 34

The Carbon Cycle:

The natural greenhouse effect:

Answer 34

The NGE:

• Earth gets energy from the sun (30% is reflected back to space by ice or clouds, and 70% is absorbed into the land and oceans and the atmosphere). This heats up the planet.
• As the rocks, air and oceans warm, they radiate heat energy (thermal and infrared). From the surface, this energy travels into the atmosphere where much of it is absorbed by water vapour and GHGs like CO2 or methane.
• When they absorb this energy, they turn into heaters and radiate heat back to earth in all directions.
• This heat radiated back is heating the lower atmosphere and the surface, enhancing the heating they get from direct sunlight.
• This cycle that heats the earth for us means we can survive. Without it, the average surface temp would be -18 degrees, rather than 15 degrees.

Question 35

The Carbon Cycle:

The Enhanced Greenhouse Effect (EGE):

Answer 35

EGE:

• This is the impact caused by human emissions of greenhouse gases (CO2, methane, water vapours), mainly from burning fossil fuels and deforestation.
• These gases are unnaturally released and remain in the atmosphere.
• When the sun releases radiation towards the earth, some is absorbed by the earth’s surface, causing temp increases, but some is also reflected back to space by the layer of gases.
• This layer of GHGs traps this radiation and prevent it escaping, reflecting it back to the earth’s surface.
• This causes global temperatures to rise and leads to global warming.

Question 36

The Carbon Cycle:

The cycle affects the atmosphere:

Answer 36

Atmosphere and climate:

• The carbon cycle affects the amount of gases containing carbon (CO2 and methane) in the atmosphere.
• Too much can lead to the EGE, causing temp rises and global warming.
• This affects other parts of the climate too (more extreme storms, etc).

Question 37

The Carbon Cycle:

The cycle affects the land:

Answer 37

Land:

• The carbon cycle is responsible for the formation and development of soils. When the climate warms, these soils lose moisture and become less fertile and less able to decompose matter.
• Less vegetation will grow, meaning less food and less photosynthesis to take carbon out the atmosphere.
• Wildfires will increase in probability
• Food security will decrease
• Crops will take longer to grow.
• Land ice will melt
• Permafrost will melt and release methane (positive feedback loop).

Question 38

The Carbon Cycle:

The cycle affects the oceans:

Answer 38

Oceans:

• As temps rise, the sea levels rise due to melting land ice and the warming waters expanding slightly.
• Oceans acidify as the increased levels of CO2 in the atmosphere mean that more is absorbed into the oceans. This lowers the pH of the water and makes it more acidic. The new carbonic acid created is then used by animals to create their shells, and when they decompose into the lithosphere, this is incorporated into the whole cycle (more carbon overall).
• Animals and organisms: food chains and other organisms are harmed by temp changes and ocean acidification (like coral reefs bleaching), meaning less carbon is used by them in photosynthesis and removed from the atmosphere.

However, on the other hand, warmer water doesn’t absorb carbon as well, so that does counteract the effects to a limited extent.

Question 39

The Carbon Cycle:

The cycle affects regions of Europe:

Answer 39

How the EGE will affect regions of Europe:

• Mediterranean regions (Spain, Italy, Greece, Turkey): drier and less fertile soils, vegetation loss and more food demand, potential desertification, more wildfires and heatwaves.
• Temperate climates (France, Germany, UK): more wildfires, less food security and energy demand, longer crop growing seasons.
• Northern regions (Scandinavia, Russia): more crop yields, less land ice coverage, less energy demands, less risk of storms.
• Polar and mountain regions (Alps, Norway): Land ice, ice caps and glacial melt, permafrost melt (positive feedback loops), new shipping routes created.
• Coastal zones: More ocean acidification, higher sea levels, increased risk of flooding.
• All regions: loss of biodiversity, warming temps..

Question 40

Water, Carbon, Climate and life on Earth

The cycles are essential for life on Earth:

Answer 40

1. Carbon is the fundamental building block of life - all living things contain carbon
   Water is essential for all living things to survive.
2. Plants form the base of most food chains. They use photosynthesis to grow and live, which requires both water and carbon
3. Water is present in the atmosphere as water vapour, and carbon as CO2 and methane. These are greenhouse gases and they cause the NGE that keeps the Earth a suitable temperature for life.
4. Human activities increase the concentration of greenhouse gases in the atmosphere and cause the EGE. This increases global warming.

Question 41

Water, Carbon, Climate and life on Earth

Feedback loops in the water cycle:

Answer 41

Positive feedback loop:
Global temperatures increase – Evaporation increases – the amount of water in the atmosphere increases – greenhouse effect increases – (back to start).
OR:
Global temps rise – land ice melts – temps warm further as the ocean has less albedo than ice and absorbs more heat – causes more temp rise and more sea ice melt – (cyclical repeat)

Negative feedback loop: (promotes dynamic equilibrium)
Global temps rise – evaporation increases – amount of water vapour in the atmosphere increases, causing more clouds to form – increased cloud cover reflects more of solar energy back (more albedo) – temps fall.

Question 42

Water, Carbon, Climate and life on Earth

Feedback loops in the carbon cycle:

Answer 42

Positive feedback loops:
Global temps rise – plant respiration rates increase – amount of CO2 in atmosphere increases – EGE increases – (cyclical repeat).
OR:
Global temp rise – permafrost melts – releases methane – methane enhances the EGE – temps rise more – (cyclical repeat).

Negative feedback loops:
CO2 in the atmosphere increases – extra CO2 causes plants to increase growth – plants remove and store more CO2 from the atmosphere – amount of CO2 in the atmosphere reduces

Question 43

Water, Carbon, Climate and life on Earth

Interactions between the cycles:

Answer 43

They depend on each other:

1. Carbon combines with water in the atmosphere, forming acid rain and chemical weathering, removing carbon from the atmosphere.
2. Water is needed for photosynthesis, which removes carbon from the atmosphere
3. The amount of CO2 in the atmosphere affects global temps, which increases evaporation rates, and therefore precipitation rates, increasing the water cycle.
4. Ocean acidification and ocean uptake and loss.
5. Permafrost positive feedback loop

Question 44

Water, Carbon, Climate and life on Earth

Ocean currents example:

Answer 44

How they regulate the Earth’s temp (Thermohaline Pump)

• They counteract the unequal distribution of solar radiation, taking warm water from tropical/equatorial regions, to the poles, and cold water from the poles to the equator.
• They then cool down/warm up the air above them and regulate the land temps too (e.g. without the Gulf Stream, the UK would be as cold as Canada).
• This happens as warmer, less dense and less saline water travels into deeper and colder oceans, which increases its salinity and density and lowers its temp. This happens like a conveyor belt.

What would happen to the circulation when Arctic ice melts:

• In the short term, melting ice means oceans become cooler, slower moving and less saline. The new added freshwater makes the currents flow slower.
• But, in the long term after it is redistributed, means the colder ocean areas are less cold and the extremity of the whole system is lessened. It will make all the oceans warmer and eventually cause sea level rise and ocean acidification.

How this represents a negative feedback loop:
The loop: Global temps rise – there is more evaporation – more low lying clouds – more solar radiation is reflected back into space as albedo increases – temps reduce.

But it also creates a positive feedback loop:
The loop: Global temps rise – land ice melts, exposing the land underneath – increases albedo – less radiation is reflected back – global temps increase more – (cyclical repeat).

Question 45

Water, Carbon, Climate and life on Earth

Climate change affects life on Earth:

Answer 45

Climate change will have major impacts on life

1. The pattern of precipitation is expected to change (wet areas will get wetter and dry areas drier). This will cause water shortages in areas and possible conflicts
2. Extreme weather events (storms, floods, droughts) will become more frequent. LICs will be worst affected as they are most vulnerable.
3. Agricultural productivity will decrease in areas as the soils get less productive in more heat (causing food shortages).
4. Sea levels will rise further (flooding low lying areas).
5. The geological range of species will change, and species will migrate elsewhere and disrupt the food chains and ecosystems. It will also make some species extinct.
6. Plankton numbers will decline if temps rise, which will have a knock on effect on marine food chains.

Question 46

Water, Carbon, Climate and life on Earth

Human efforts in influencing the carbon cycle and mitigating climate change:

Answer 46

Humans can mitigate climate change impacts by reducing transfers of carbon into the atmosphere.
This can be done at different scales:
1. Individual:
- people can use their cars less and buy more energy efficient cars.
- people can make their homes more energy efficient (double glazing, insulation)
- People in Peru are painting their Andes mountainsides white, to increase albedo.
- People in India and Nepal mountains are making artificial glaciers with dams (holding the water higher up so it freezes in the winter, then releasing it as run off in the summer).
2. Regionally/Nationally:
- Govs can reduce their reliances on fossil fuels for heating and powering homes by making renewables less expensive.
- Afforestation can increase carbon uptake through the biosphere
- Planners can increase sustainability by making better public transport and more green spaces.
- Govs can invest in carbon capture and storage. CO2 emitted from fossil fuel burning is captured and stored underground, taking it out of the atmosphere.
3. Global:
- Countries can co-operate to reduce emissions (Kyoto Protocol 1997 or Paris agreement 2015). These international treaties control the amount of carbon countries can release.
- There are also international carbon trading schemes where nations and businesses are given limits on their emissions, and they get extra credits to sell for less emissions, but if they go over the limit, they need to buy more credits as punishment. (The EU has a scheme, it is also done nationally like in Australia and South Korea).

Question 47

Water, Carbon, Climate and life on Earth

CCS - pros and cons:

Answer 47

Pros:

• It removes the problem at its source (the CO2).
• Scientists estimate CCS reduces CO2 emissions by 19% globally.
• Coal power plants can use CCs to capture the emissions they create before they reach the atmosphere (one in Canada captures over 90% of their emissions).
• CCS can also remove other pollutants, like Nitrogen oxide and sulphur dioxide (both greenhouse gases that produce acid rain).
• CCS can also reduce the price of carbon and create room for a carbon tax.

Cons:

• It is an expensive process, for both the plant and consumers (coal plants that use it have to increase their prices by 70-90%).
• There are no regulations in place for CCS now.
• Using CCS for oil recovery defeats the point as CO2 emissions are created when obtaining the oil to create space underground.
• Long term storage is also uncertain (scientists think it is only viable for the next 100 years).
• CO2 transport and storage sites can be dangerous (a leak or fault can cause a lot of atmospheric damage)
• Public perception is also not so good.