A-Level Geography: The Carbon Cycle EQ1

Question 1

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is the carbon cycle?

Answer 1

A biogeochemical cycle by which carbon moves from one sphere to another.

Question 2

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What type of system is the carbon cycle.

Answer 2

A closed system.

Question 3

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What are the types of carbon stores?

Answer 3

• Atmosphere: CO2 and compounds e.g. methane
• Hydrosphere: dissolved CO2
• Lithosphere: carbonates in limestone and fossil fuels
• Biosphere: living and dead organisms

Question 4

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What are the forms of carbon?

Answer 4

• Inorganic found in rocks as bi/carbonates
• Organic found in plant material
• Gaseous

Question 5

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is a carbon flux?

Answer 5

It refers to the movement or transfer of carbon between stores.

Question 6

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What are the largest carbon stores and their data?

Answer 6

Long term stores
- Sedimentary rocks (100,000,000 PgC)

• Deep Ocean (38,000 PgC)

Short term stores
- Soil (1500 PgC)

• Ocean Surface (1000 PgC)
• Atmosphere (560 PgC)
• Ecosystems (560 PgC

Question 7

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What are the 3 types of oceanic carbon pumps?

Answer 7

• Biological carbon pump.
• Physical carbon pump.
• Carbonate carbon pump.

Question 8

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

Explain the process of the Biological carbon pump.

Answer 8

1. These move carbon dioxide from the ocean surface to marine plants called phytoplankton through photosynthesis.
2. This effectively converts carbon dioxide into food for (microscopic animals) and their predators.
3. Most of the carbon dioxide taken up by phytoplankton is recycled near the surface. About 30% sinks into deeper waters before being converted back into carbon dioxide by marine bacteria.

Question 9

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

Explain the process of the Physical carbon pump.

Answer 9

1. These move carbon compounds to different parts of the ocean in downwelling and upwelling currents
2. Downwelling occurs in parts of the ocean where cold, denser water sinks.
3. These currents bring dissolved carbon dioxide down to the deep ocean.
4. Once there, it moves in slow-moving deep ocean currents, staying there for hundreds of years.
5. Eventually, these deep ocean currents, are part of the thermohaline. circulation, return to the surface by upwelling.
6. The cold deep ocean water warms as it rises towards the ocean surface and some of the dissolved carbon dioxides is released back into the atmosphere.

Question 10

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

Explain the process of the Carbonate carbon pump.

Answer 10

These form sediments from dead organisms that fall to the ocean floor, especially the hard outer shells and skeletons of fish, crustaceans and corals, all rich in calcium carbonate.

Question 11

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is the physical pump?

Answer 11

1. Known as thermohaline circulation. CO₂ easily dissolves into cold water, there is a high density of CO₂ at the poles and in deep ocean water. Warm water releases more CO₂ into the atmosphere.
2. Ice forms at the poles, increasing the salinity and therefore meaning the denser water sinks, this drives the thermohaline system. Warm water is therefore drawn up from the Caribbean (Gulf Stream) creating the current which is recharged at the Antarctic.

Question 12

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What factors speed up decomposition/ carbon loss from soils?

Answer 12

Climate - faster rates of decomposition due to higher temperatures or wetter conditions.

Soil type - sandy soils lose carbon quicker than clay soils since they are more porous, micro-organisms can reach the carbon-rich matter.

Human activity - intensive farming or ploughing causes soil erosion and loss of carbon from the soil due to gaps created by decomposers.

Question 13

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is a balanced carbon cycle?

Answer 13

A balanced carbon cycle is the outcome of different components working in a sort of harmony with each other

Question 14

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

How does photosynthesis help regulate the carbon cycle?

Answer 14

1. Photosynthesis by terrestrial and oceanic organisms plays an essential role in keeping carbon dioxide levels relatively constant and thereby helping to regulate the Earth’s mean temperature.
2. The amount of photosynthesis varies spatially, particularly with net primary productivity (NPP).
3. NPP is highest in the warm and wet parts of the world, particularly in the tropical rainforests and in shallow ocean waters. It is least in the tundra and boreal forests.

Question 15

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

How does soil health help balance the carbon cycle?

Answer 15

1. Soil health is an important aspect of ecosystems and a key element in the normal functioning of the carbon cycle. Soil health depends on the amount of organic carbon stored in the soil.
2. The storage amount is determined by the balance between the soil’s inputs
   (plant and animal remains, nutrients)
   and its outputs (decomposition, erosion and uptake by plant and animal growth.)
3. Carbon is the main component of soil organic matter and helps to give soil its moisture-retention capacity, its structure and fertility.
4. Organic carbon is concentrated in the surface layer of the soil. Healthy soil has a large surface reservoir of available nutrients which, in their turn, condition the productivity of ecosystems.
5. All this explains why even a small amount of surface soil erosion can have such a devastating impact on soil health and fertility.

Question 16

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is the natural greenhouse effect?

Answer 16

1. 31% of solar radiation is reflected by clouds, GHGs and the land surface. 69% of the radiation is absorbed by the Earth’s surface and warms it, converting it into longwave infrared radiation.
2. 69% then is re-radiated and then trapped by GHGs in the atmosphere, warming the Earth’s surface and troposphere.

Question 17

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is the anthropogenic greenhouse effect?

Answer 17

The enhancement of the natural greenhouse effect is due to human activities. Less radiation is escaping due to the thicker atmosphere absorbing outgoing longwave radiation leading to global warming.

Question 18

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is arctic amplification?

Answer 18

The Arctic is warming much faster than the rest of the planet since as the sea ice melts, the more exposed ocean absorbs more heat and has less reflectivity means that more heat is absorbed. Thawing permafrost releases methane as warming temperatures lead to more decomposition, so more GHGs.

Question 19

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

What is sequestration?

Answer 19

A process that removes carbon from the atmosphere and stores it in a liquid or solid form.

Question 20

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

How does the presence of phytoplankton move around the world?

Answer 20

• It changes throughout the year, summer is the most prominent due to increased sunlight for photosynthesis.
• Cold upwelling, shallow waters, and river estuaries are all packed with nutrients for phytoplankton to grow.

Question 21

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

Which compound is used by organisms in the carbonate pump?

Answer 21

Calcium carbonate. It is used in order to make hard shells or skeletons.

Question 22

6.2 Biological processes sequester carbon on land and in the oceans on shorter timescales.

Where does carbon flux in the carbonate pump?

Answer 22

• Some cells that use calcium carbonate dissolve before reaching the seafloor and become part of the deep ocean carbon store once they die.
• Some do not break down and are sedimented into carboniferous limestones.

Question 23

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

What is the natural greenhouse effect?

Answer 23

Short-wave radiation passes through gases of Earth’s Atmosphere which is then absorbed by the Earth (warming planet). Earth gives off long-wave radiation that mostly absorbed by the atmosphere

Question 24

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

State the percentages of greenhouse gases produced.

Answer 24

CO2 - 89%

Methane - 7%

Nitrous oxide - 3%

Question 25

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

What do greenhouse gases do?

Answer 25

Trap infrared radiation (which is heat that is radiated from the earth) and prevent loss of heat to space

Question 26

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

What is meant by the enhanced greenhouse effect?

Answer 26

The increase in the greenhouse effect is said to be caused by human activities that increase the number of greenhouse gases in the Earth’s atmosphere.

Question 27

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

How does the carbon cycle help regulate the composition of carbon in the atmosphere?

Answer 27

• Phytoplankton

- Terrestrial photosynthesis

Question 28

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

How much of the world’s carbon is stored in the soil.

Answer 28

Soils store between 20-30% of the world’s carbon. The amount of CO2 sequestered or emitted depends on local conditions.

Question 29

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

What are the factors affecting soil capacity to store organic carbon?

Answer 29

• Climate - this affects the rate of plant growth and microbial activity. Decomposition occurs at a fast rate in places with higher temperatures and rainfall.
• Soil type - clay-rich soils contain more carbon than sandy soils.
• Use of soils - Land use, cultivation and disturbance can affect how much carbon can be held.

Question 30

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

How much of a tree’s biomass consists of CO2.

Answer 30

95% of the tree’s biomass consists of CO2 which is sequestered and converted to cellulose.

Question 31

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

Explain the process of terrestrial sequestering.

Answer 31

1. Plants (primary producers in an ecosystem) sequester carbon out of the atmosphere during photosynthesis. In this way, carbon enters the food chains and nutrients cycles of terrestrial ecosystems.
2. When animals consume plant matter, the carbon sequestered in the plant becomes part of their fat and protein. Respiration, particularly by consumer animals, returns some of the carbon back to the atmosphere.
3. Waste from animals is eaten by micro-organisms (bacteria and fungi) and detritus feeders (e.g. beetles).
4. As a consequence, carbon becomes part of these creatures. When plants and animals die and their remains fall to the ground, carbon is released into the soil.

Question 32

6.3 A balanced carbon cycle is important in sustaining other earth systems but is increasingly altered by human activities.

Carbon fluxes within ecosystems vary on two timescales. What are they?

Answer 32

Diurnally - during the day, fluxes are positive - from the atmosphere into the ecosystem. The reverse applies at night when respiration occurs but not photosynthesis.

Seasonally - during winter, carbon dioxide concentrations increase because of the low levels of plant growth. However, as soon as spring arrives and plants grow, these concentrations begin to decrease until the onset of autumn.