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Geo: ELSS > The Carbon Cycle > Flashcards

The Carbon Cycle Flashcards

1
Q

What is the importance of the Carbon Cycle

A
  • Used by humans for energy
  • ‘building blocks of life’
  • used for photosynthesis to be turned to O2 as CO2 is toxic to humans.
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2
Q

Consequences of disruptions to the Carbon Cycle

A
  • Sea level rises (80cm by the end of the century)
  • Forest fires become more frequent and areas losing the amazon could feel the greatest impact
  • Food shortages - wheat yields have decreased by 40% in Africa
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3
Q

How much carbon is stored in the atmosphere?

A

720GT

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4
Q

How much carbon is stored in the Ocean (Surface and Deep Layers)

A

Surface - 670GT
Deep - 37,000

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5
Q

How much carbon is stored in the Lithosphere (Sedimentary and Kerogens)?

A

Sedimentary - >60.000,000GT

Kerogens - 15,000,000GT

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6
Q

How much carbon is stored in the Biosphere (dead and alive)?

A

Dead - 1,200GT

Alive - 600-1,000GT

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7
Q

How much carbon is stored as Fossil Fuels?

A

5330GT

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8
Q

Is the Global carbon cycle an open or closed system?

A

Closed - The amount of carbon on the earth doesn’t change, it only changes form.

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9
Q

What is an example of an open carbon system?

A

Forest - Trees can be cut down or die, and leave the carbon system. Any system that carbon can leave or enter is open.

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10
Q

What are the 3 largest global carbon stores?

A

1st: Lithosphere - stored as fossil fuels and in rocks, the lithosphere stores most of the carbon on Earth
2nd: Oceans - stored as dissolved carbon and calcium carbonate in the shells of marine life. Only 4% of carbon is stored near the surface
3rd: Biosphere - stored in organic molecules in living or dead plants and animals. Decaying releases CO2 to the atmosphere.
4th: Atmosphere - Stored as the gas CO2.

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11
Q

What are key fluxes in the carbon cycle?

A
  • Precipitation
  • Respiration
  • Carbon sequestration
  • Photosynthesis
  • Weathering
  • Decomposition
  • Combustion
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12
Q

Explain Precipitation - CC

A

An increase in CO2 levels have led to a dramatic increase in the acidity of seawater and therefore rainfall.

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13
Q

Explain Respiration - CC

A
  • 6 O2 + C6H12O6 —> 6 CO2 + 6 H2O + ATP
  • Plants and animals absorb oxygen to provide energy which is needed for metabolism and growth.
  • The volume of carbon exchanged by respiration and photosynthesis each year is 1000x higher than through the slow carbon cycle.
  • Stays in balance with photosynthesis (biosphere -> atmosphere -> biosphere.)
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14
Q

Explain Carbon Sequestration Physical Pump - CC

A

Physical inorganic pump:
- CO2 enters the ocean from the atmosphere by
diffusion.
- Surface ocean currents then transport the water
and dissolved CO2 towards the poles where it
cools, becomes more dense and sinks.
- Downwelling carries dissolved carbon to the
oceans depths where individual carbon
molecules remain for centuries.
- Eventually deep ocean currents transport the
carbon to areas of upwelling causing the water to
rise and CO2 to diffuse into the atmosphere.

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15
Q

Explain Carbon Sequestration Biological Pump - CC

A

Biological pump:
- Marine organisms (phytoplankton) combine
sunlight, water and dissolve CO2 to produce
organic material.
- This causes carbon to be locked in the
sediment on the ocean floor or decomposed to
release CO2 into the ocean.
- Some crustaceans extract carbon and calcium
ions from sea water to manufacture shells and
skeletons.
- Most carbon-rich material ends up on the
seafloor undergoing lithification to form chalk or
limestone.

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16
Q

Explain Photosynthesis - CC

A
  • 6 CO2 + 6H2O —> 6O2 + C6H12O6
  • Using the sun’s energy to cover the light energy into chemical energy for the formation of glucose and growth in plants.
  • O2 is released balancing respiration.
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17
Q

Explain Weathering - CC

A

Chemical: Carbonation - rainwater (weak carbonic acid) dissolves limestone & chalk slowly. This releases carbon from linestomes to streams or rivers or the atmospheres. This transfers 0.3 billion tonnes of carbon a year. Increased rate in colder temps.

Physical: Freeze-thaw breaks rocks down into smaller particles with no chemical change releasing carbon. Increased rate at fluctuating temps.

Biological: Chelation - rainwater mixed with dead and decaying organic matter to form humid acids which attack rock minerals.
Roots can destroy rocks. Increased rate at warmer moist temperatures.

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18
Q

Explain Decomposition - CC

A

Bacteria or fungi break down dead organic matter, extracting energy and releasing CO2 into the atmosphere.
This occurs faster in warm humid environments (places with rainforest).

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19
Q

Explain Combustion - CC

A

Organic material earths or burns in oxygen, releasing CO2 as well as sulphur dioxides and nitrogen oxides.
Usually occurs from human activity (deliberate firing of forest & combustion of fossil fuels) but occurs naturally in forest fires.
This increases the amount of CO2 in the oceans and atmosphere adding to the greenhouse gas effect.

20
Q

How does temperature influence carbon moving between the atmosphere and oceans?

A

Increase in temperature - speeds up diffusion of CO2 out of the ocean but slows absorption into the ocean from the atmosphere.
As temperatures increase due to global warming more carbon will be released from pumps resulting in a downwards spiral.

21
Q

What processes does the fast carbon cycle include?

A

Includes the processes of photosynthesis, respiration, combustion, decomposition & air-sea gas exchange.
Carbon moves between the atmosphere, oceans and biosphere.
Phytoplankton are key components in absorbing CO2 from the atmosphere.

22
Q

What processes does the slow carbon cycle include?

A

Includes the processes of chemical weathering, fixing dissolved carbon, volcanic activity & subduction.
Marine organisms fix dissolved carbon with calcium to form calcium carbonate.
Decomposed organic material is buried beneath younger sediments.
Lithification

23
Q

What is the total carbon circulation for the slow carbon cycle?

A

10-100 million tonnes a year

24
Q

What is the total carbon circulation for the fast carbon cycle?

A

10,000 to 100,000 million tonnes a year

25
Q

Explain diurnal changes in the carbon cycle

A
  • there is a significant change in the flux of photosynthesis over the course of the day
  • the respiration flux remains constant throughout the course of the day.
  • during the day, more carbon is stored as biomass in the plant, and during the night more carbon is released from the biomass through the process of respiration.
26
Q

Explain seasonal changes in the carbon cycle

A
  • During the northern hemisphere winter, more carbon is released as dead plants decompose, so the biosphere store decreases and the soil and atmosphere stores increase.
  • During the summer there are much higher rates of photosynthesis and respiration meaning there is less carbon in the atmosphere and soil, and more in the biosphere
27
Q

What is the correlation between CO2 ppm in the atmosphere and global temperatures over the earth history?

A

There is a very strong correlation between temperature and CO2 ppm, because when the graphs have a very similar shape. When the levels of CO2 rise, so does the temperature, suggesting a strong link of causality between the 2.

28
Q

What are the impacts of long term climate change on the carbon cycle stores?

A
  • At times of glacial maxima CO2 concentrations fall to around 180ppm, while in warmer inter-glacial periods they are 100ppm higher.
  • The carbon pool in vegetation shrinks during glacials as ice sheets advance.
  • expanses of tundra beyond the ice-limit sequester huge amounts of carbon in permafrost
  • As forests are replaced by grasslands due to human activity the amount of carbon stored in tropical biomes will diminish.
  • global warming will allow the boreal forests of Siberia and Canada to expand polewards increasing the biosphere store.
  • long-term climate change will probably see an increase in carbon stores in the atmosphere, a decrease in carbon stores in the biosphere and possibly a decrease in the ocean carbon stores.
29
Q

What are the impacts of long term climate change on the carbon cycle fluxes

A
  • As vegetation decreases due to human activity NPP and the total volume of carbon fixed in photosynthesis will decline.
  • During glacials an overall slowing of the carbon flux and smaller amounts of CO2 returned to the atmosphere through decomposition
  • Higher global temperatures will in general increase rates of decomposition and accelerate transfers of carbon from the biosphere and soil to the atmosphere.
  • Carbon frozen in the permafrost of the tundra is being released as temperatures rise above freezing and allow oxidation and decomposition of vast peat stores.
  • acidification of the oceans through the absorption of excess CO2 from the atmosphere reduces photosynthesis by phytoplankton
  • Movement of carbon into and out of the atmosphere will vary regionally, depending on changes in rates of photosynthesis, decomposition and respiration.
30
Q

Changes in the carbon cycle - FORESTRY

A

· Plantations result in an increased carbon store – mature plantation forest trees in UK contain 170-200 tonnes C/ha (10x grassland, 20x heathland)

· When felling occurs (to renew growth in forests) then the above ground carbon store will reduce and the soil will be more vulnerable to oxidation and erosion without the binding effect of plant roots. This may reduce the soil organic carbon. 

· Soil has even larger carbon pool through the addition of roots (below ground biomass). In England forest soil carbon around 500 tonnes C/ha.

· Forest trees sequester CO2 from atmosphere for hundreds of years. Most carbon is stored in wood of trunk.

· Forest trees only absorb more than they release for the 1st 100 years after planting, then levels off and balanced by inputs of litter to soil, respiration and soil decomposers. Consequently plantations have a rotation period of 80-100 years. They are then felled and reforestation begins.
31
Q

How does burning fossil fuels influence the carbon cycle?

A
  • Releases large levels of CO2 into the atmosphere

- reduces the amount of carbon stores as fossil fuels in the lithosphere

32
Q

What percentage of global energy consumption came from fossil fuels in 2019?

A

79%

33
Q

How much carbon does burning fossil fuels release into the atmosphere each year?

A

35bn tonnes - Increases CO2 concentration by 1ppm

34
Q

Land use changes: deforestation associated with farming and urbanisation

A
  • Deforestation has reduced the planet’s forest cover by nearly 50%.
  • Soils have been degraded by erosion caused by deforestation and agricultural mismanagement, reducing its carbon store.
  • Carbon stores in wetlands have also been depleted as they are drained for cultivation and urban development (dry out and are oxidised).
35
Q

Changes in the carbon cycle - FARMING

A

· Ploughing reduces soil carbon storage as it exposes organic matter (biomass) to erosion by wind or water.

· Ploughing also exposes soil organic matter to oxidation, releasing carbon dioxide to the atmosphere.

· It has been estimated that US soils may have lost between 30 and 50% of the soil organic carbon that they contained prior to the establishment of agriculture there.

· Approximately 12% of soil C is held in cultivated soils, which cover around 35% of the terrestrial land area of the planet - so it proportionally holds less than we would expect for the area it covers.

· Crops harvested in the summer months reduces carbon storage above ground and reduces amounts of organic matter returning to the soil as vegetation is removed for eating.

· Where farming replaces natural grasslands carbon cycle changes are less apparent but photosynthesis is generally lower than in natural ecosystems. This is due to a lack of biodiversity in farmed systems and the growing season compressed into 4-5 months.

36
Q

How has the NPP changed since 1750?

A

Gone from 280ppm to 418ppm

37
Q

What is the aim of carbon sequestration?

A

To capture and store atmospheric carbon dioxide, aiming to reduce the amount of carbon dioxide in the atmosphere to help reduce global climate change.

38
Q

What are the 2 key types of carbon sequestration?

A

Biological

The storage of atmospheric carbon dioxide in vegetation, soils, woody products, and aquatic environments.

Geological

The storage of atmospheric carbon dioxide in underground geologic formations. CO2 is often pressurized until it becomes a liquid.

39
Q

How can humans carry out carbon sequestration?

A

Encouraging the growth of plants, especially larger ones like trees, this advocates biological sequestration. Grow plants who have a high carbon content as they will store more carbon.

40
Q

What is CCS?

A

Carbon Capture and Storage

41
Q

How does CCS work?

A

Mixes CO2 with amine that absorbs the CO2, and then the CO2 is separated and kept in liquid form.

42
Q

How many operational CCS plants are there in the world?

A

27

43
Q

How many CCS plants are planned?

A

135

44
Q

What has the UK pledged with regards to CCS?

A

Investment of £1bn - this is not enough to reach net 0

45
Q

Sizes of stores in order

A 
Lithosphere 
Ocean - deep layer 
Biosphere - dead
Biosphere - living 
Atmosphere 
Ocean - surface layer

Geo: ELSS (4 decks)

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