Water and Carbon cycles: The carbon cycle

Question 1

What is acidification?

Answer 1

The gradual reduction of pH of the oceans, use to dissolving carbon dioxide from the atmosphere.

Question 2

Define carbon fluxes:

Answer 2

The movement of carbon between stores.

Question 3

Define enhanced greenhouse effect:

Answer 3

The build-up of greenhouse gases in the atmosphere, reducing the amount of solar radiation reflected into space.

Question 4

Define inorganic carbon:

Answer 4

Carbon stored in carbonated rocks.

Question 5

Define organic carbon:

Answer 5

Carbon stored in plant martial and living organisms.

Question 6

Define outgassing:

Answer 6

The release of dissolved carbon dioxide

Question 7

Define inorganic carbon:

Answer 7

Carbon stored in carbonated rocks.

Question 8

Define phytoplankton:

Answer 8

Small organisms that rely on photosynthesis to survive, so intake carbon dioxide from the atmosphere.

Question 9

What is combustion?

Answer 9

• When fossil fuels and organic matter, e.g. trees, are burnt they emit CO2 into the atmosphere that was previously stored inside of them.
• Occurs when fossil fuels are burnt and in wildfires.

Question 10

What is decomposition?

Answer 10

• When living organisms die they are broken down by decomposers which respire, returning CO2 into the atmosphere.
• Some organic matter is also returned to the soil where it is stored adding carbon matter to the soil.

Question 11

What is diffusion?

Answer 11

• The oceans absorb CO2 from the atmosphere in vast amounts, which has increased ocean acidity by 30% since pre-industrial times.
• The ocean is the biggest carbon store, but with carbon levels increasing the oceans are becoming harmed e.g. coral bleaching.

Question 12

What is weathering and erosion?

Answer 12

• Rocks are eroded on land or broken down by carbonation weathering (occurs when CO2 in the air mixes with rainwater to create carbonic acid which aids erosion of rocks e.g. limestone).
• The carbon is moved through the water cycle where marine organisms use this carbon to build up their shells.

Question 13

What is burial and compaction?

Answer 13

• When shelled marine organisms die their shell fragments fall to the ocean floor and become compacted over time to form limestone.
• Organic matter from decaying marine organisms is compacted over time to form fossil fuel deposits.

Question 14

What is carbon sequestration?

Answer 14

• The transfer of carbon from the atmosphere to other stores (natural and artificial).
• E.g. a plant sequesters carbon when it photosynthesises and stores the carbon in its mass.
• Factories are starting to use carbon sequestration via carbon capture and storage (carbon is captured and transported via pipelines to depleted gas fields and saline aquifers).

Question 15

Outline predominant carbon stores:

Answer 15

Marine sediment and rocks: Stored long-term in the lithosphere, contains 66,000 - 100,000 million gigatons of carbon.

Oceans: Stored in the hydrosphere, stores 38,000 billion tonnes of carbon which is constantly being transferred e.g. used by marine organisms, lost to lithospheres.

Fossil fuel deposits: Stored in the lithosphere, humans have developed technology to exploit them rapidly.

Atmosphere: Human activity has caused CO2 levels in the atmosphere to increase by 40% since pre-industrial times (now 750 billion tonnes of stored carbon).

Question 16

Outline the lithosphere as the main carbon store:

Answer 16

Global stores are unevenly distributed- e.g. oceans in the Southern hemisphere are larger, storage in the biosphere mostly occurs on land.

Question 17

Outline how changes in forests has caused changes in the carbon cycle:

Answer 17

• Non-tropical forests have seen an increase in carbon sequestration (especially in Europe and Eastern Asia) due to conversion of agricultural land and plantations to new forests.
• Forests in industrialised regions are expected to increase by 2050, but in the global south forested areas are expected to decrease.
• Rate of forest loss has decreased from 9.5 million hectres annually in 1990 to 5.5 million hectres annually in 2010.

Question 18

Outline how natural processes have caused the carbon cycle to change overtime:

Answer 18

Wildfires: Transfer of carbon from biosphere to atmosphere as CO2 released by burning- this can encourage plant growth long term.

Volcanic activity: Volcanic eruptions release CO2 gas. Contributes a relatively low amount of CO2 gas.

Question 19

Outline how human processes have caused the carbon cycle to change overtime:

Answer 19

Fossil fuel use: Combustion trasfers CO2 from a long-term carbon sink to the atmosphere.

Deforestation: Land is cleared for use, e.g. farming, housing, which rapidly released carbon stored in plants via slash and burn techniques.

Farming practices: Pastoral farming releases CO2 as animals respire. Ploughing can release CO2 stored in the soil. Farm machinery, e.g. tractors, can release CO2.

Question 20

What is meant by the carbon budget?

Answer 20

The balance between carbon inputs and outputs to a store, or the balance pf exchanges between the four major stores of carbon.

Question 21

Outline what is meant by the ENHANCED greenhouse effect?

(a good topic to talk about if discussing human impacts on the global climate)

Answer 21

• The process where abnormally high amounts of greenhouse gases are being produced by humans, trapping radiation from the sun, causing global warming and climate change.
• Radiative forcing (difference between incoming solar radiation absorbed by the earth and energy radiated back out) has increased over the years, leading to more heat being trapped.

Question 22

Outline causes of the enhanced greenhouse effect:

Answer 22

Land use change: Accounts for 1/10 of carbon release annually and has short term impacts on soil and the atmosphere e.g. in the Amazon 70% of deforestation is for cattle ranching.

Fertilisers: Significant source of greenhouse emissions, alongside rice plantations (methane emissions have also increased due to increased plant productivity due to higher CO2 levels). More sustainable crops e.g. quinoa are being considered as substitutes which require less water to grow.

Deforestation: Accounts for 20% of all global greenhouse emissions. The main impact is when the cycle is interrupted and land is used for other purposes, reducing carbon sequestration and the land becomes a carbon source.

Urbanisation: Countryside is replaced by buildings. Affects the local and global carbon cycles by replacing vegetation and covering soils. Urban areas cover 2% of the worlds land mass yet account for 97% of all human CO2 emissions.

Question 23

Outline Milankovitch Cycles:

Answer 23

• Variations in the Earth’s orbit causes time periods where we experience greater heating from the sun, increasing global temperatures.
• This increase allows for more glaciers to melt, increasing flows to the carbon cycle, allowing more CO2 to enter the atmosphere.

Question 24

What is the impact of the carbon cycle on tropical rainforests?

Answer 24

• High rates of photosynthesis and respiration in forests leads to greater humidity, cloud cover and precipitation.
• Deforestation reduces photosynthesis and respiration, reducing humidity, cloud cover and precipitation.

Question 25

What is the impact of the carbon cycle on oceans?

Answer 25

- Warmer oceans cause more plankton growth through plankton chemical production, leading to cloud formation. - Warm oceans store less CO2. Means higher temperatures lessen the effects of oceans as carbon sinks. - Positive feedback loop: Warmer oceans are classified as carbon sinks, emphasising the greenhouse effect.

Question 26

Outline 2 positive feedback loops in the carbon cycle:

Answer 26

- Wildfires are more likely to occur in hotter and drier climates caused by climate change, which release vast amounts of CO2 into the atmosphere, increasing climate change. - Higher temperatures stimulate the thawing of permafrost, releasing CO2 and methane, causing global warming on a global scale. Higher temperatures causes more permafrost to melt, causing further gas release and warming.

Question 27

Outline 2 negative feedback loops in the carbon cycle:

Answer 27

- Increased photosynthesis by plants and rising global temperatures allows vegetation to grow in new areas. New vegetation absorbs CO2 from the atmosphere, decreasing the warming effect. - Higher CO2 levels causes phytoplankton to grow (as they feed off CO2). They use CO2 in photosynthesis causing CO2 leels to decrease, causing phytoplankton to decrease.