Carbon 2.2

Question 1

What are carbon cycle pumps?

Answer 1

The processes operating in oceans to circulate and store carbon. There are three sorts: biological, carbonate and physical

Question 2

What is the biological carbon pump?

Answer 2

This is the part of the carbon cycle which moves slightly faster than the other parts and happens at the surface of the ocean. There’s always an exchange of CO2 as some dissolves into the water and some is vented to the air above

Question 3

How much carbon does the biological carbon pump transfer from the atmosphere to the deep ocean each year?

Answer 3

between 5 and 15 gigatonnes

Question 4

How does the biological pump work?

Answer 4

This involves the organic sequestration of CO2 to the oceans by phytoplankton through photosynthesis. They also take up carbon in their shells, creating calcium carbonate as the shells develop. Carbon is then passed up the food chain by consumer fish and zooplankton which in turn release CO2 back into the water. However, some may die and reach the sea floor, where they decompose or turn into sediment

Question 5

What are phytoplankton like?

Answer 5

They are microscopic, usually single-celled, marine plants which float near the surface to access sunlight so they can photosynthesise.
They contain chlorophyll and need sunlight to live
They are the base of the marine food web.
Although minute, their huge number’s makes up half of the planet’s biomass

Question 6

How quick do phytoplankton growth rates tend to be? Where are they most effective?

Answer 6

Rapid
They have especially fast growth rates in shallow waters of continental shelves, where rivers carry out nutrients to the sea. The Arctic and Southern oceans are very productive areas.

Question 7

What is the carbonate pump?

Answer 7

This relies on inorganic carbon sedimentation. Marine organisms utilise calcium carbonate to make hard outer shells. When organisms die and sink many shells dissolve before reaching the floor; this becomes part of deep ocean currents. Those that do make the floor build up slowly on the sea floor forming limestone sediments

Question 8

What is the physical pump?

Answer 8

Based on the oceanic circulation of water: upwelling, downwelling and the thermohaline current

Question 9

To what extent is there spatial difference in CO2 concentration in the water?

Answer 9

CO2 in the ocean is mixed much more slowly than in the atmosphere, so there are large spatial differences in CO2 concentration

Question 10

How does the temperature of the water affect CO2 sequestration?

Answer 10

The colder the water is, the more potential for CO2 to be absorbed: polar oceans can dissolve twice as much CO2 than tropical oceans. Warm tropical waters release CO2 to the atmosphere, whereas colder oceans take in CO2.

Question 11

How does CO2 concentration vary in the deep ocean compared to the surface water?

Answer 11

CO2 concentration is 10% higher in the deep ocean than at the surface

Question 12

What are the factors that affect carbon absorption into the ocean and release back into the atmosphere?

Answer 12

wind
sea surface mixing
concentration of CO2
Temperature of the water

Question 13

How long does it take a cubic metre of water to travel around the thermohaline current?

Answer 13

1000 years

Question 14

What is the thermohaline circulation?

Answer 14

1. At the poles, the water is cold, gets saltier and increases in density meaning it sinks
2. The current is recharged as it passes Antarctica by extra cold, salty, dense water
3. Division of the current: north into Indian Ocean and into the Western Pacific
4. The two branches warm and rise as they travel north, then loop back round south/westward
5. The warmed water continues to circulate the globe, where they will eventually return to the North Atlantic. Here they cool and the cycle starts again

Question 15

Why is the thermohaline circulation vulnerable to climate change?

Answer 15

Slight changes in water temperature can alter the flow and pollution and turbulence reduces light penetration, slowing the pump down

Question 16

How does terrestrial sequestration work?

Answer 16

-Primary producers (plants) take carbon out the atmosphere through photosynthesis and release CO2 back into the atmosphere during respiration
-When primary consumers eat plants, carbon from the plants becomes part of its fats and proteins
-Micro-organisms and detritus feeders like Beetles feed on waste material from animals, and so carbon becomes part of these micro-organisms. They are known as biological decomposers
-Decay then releases CO2 back to the atmosphere or organic content of soil

Question 17

Where is decomposition fastest and where is it slowest?

Answer 17

It’s fastest in tropical climates with high rainfall, high temps and high oxygen levels. However, it’s slow in cold, dry conditions where there is a shortage of oxygen

Question 18

What % of a tree’s biomass is made from CO2? What does it do with this CO2?

Answer 18

95%
It sequesters the carbon and then converts it to cellulose

Question 19

What is the name of the process by which gaseous carbon turns into organic compounds that grow?

Answer 19

Carbon fixation

Question 20

What does the amount of carbon stored in a tree depend on?

Answer 20

Depends on the balance between photosynthesis and respiration

Question 21

Why are tropical rainforests important biological organic carbon stores?

Answer 21

-one of the largest stores on earth, sequestering 17% of all terrestrial carbon.
- The Brazil Nut tree is particularly impressive and 1% of Amazon’s 16,000 species of tree store 50% of its carbon

Question 22

Why are wetlands and peatlands important biological organic carbon stores?

Answer 22

Peat is an organic sediment
Many peatlands were formed during the Holocene and have been a store of carbon for thousands of years. However, overuse means that peatlands are now becoming an overall carbon source

Question 23

What is the role of soil in carbon storage?

Answer 23

Soils store about 20-30% of carbon, sequestering 2x that of the atmosphere and 3x that of terrestrial vegetation

Question 24

What are the two sources of carbon is soil?

Answer 24

Inorganic carbon (geological): formed in limestone or arid/semi-arid soils
Organic carbon: photosynthesis, decomposition of plants and activity in soil micro-organisms

Question 25

What is the role of leaf litter in storing carbon?

Answer 25

Any loss to the ground is a flux of carbon from plants to soil. It’s stored as dead organic matter for years before being broken down by microbes and released into the atmosphere

Question 26

What is hummus?

Answer 26

The organic component of soil, formed by decomposition of leaves and other plant materials by soil micro-organisms
It has a darker, richer colour
60% carbon so important carbon store

Question 27

What does the capacity of soil to store carbon depend on?

Answer 27

The amount off organic carbon stored within soil = inputs (litter/animal waste) - outputs (decomposition, erosion and uptake in plant growth)
This will depend on:
Climate
Soil type and biome
Use and management

Question 28

How does climate affect soils capacity to store organic carbon?

Answer 28

-Warmer and wetter conditions mean more rapid decomposition by microbes and detritivores
-Higher rainfall means increased potential to store carbon
For example, arid soils store only 30 tonnes per hectare compared to 800 tonnes per hectare in cold regions

Question 29

How does the soil type affect the soil’s capacity to store organic carbon?

Answer 29

Clay protects carbon from decomposition and so clay rich soils have a higher carbon content than sandy soils

Question 30

How does use and management affect the soil’s capacity to store organic carbon?

Answer 30

Cultivation and soil disturbance mean that since 1980, soils have lost 40-90Gt of carbon

Question 31

What are healthy soils like?

Answer 31

Dark, crumbly and porous
Contains worms and other organisms
Improve resilience to wetter weather because they enable infiltration and percolation
Sequester carbon
They contain more organic material, which is what helps to give soil its water retention capacity, structure and fertility
Provides air, water and nutrients for micro-organisms and plants
Retains moisture

Question 32

What is a carbon balance?

Answer 32

carbon stores in the atmosphere, ecosystems and soils are all in constant exchange and is regulated

Question 33

How do the season’s affect the carbon balance?

Answer 33

In winter, organic decay increases the amount of CO2, while springs renewed plant growth causes a reduction

Question 34

How could climate change alter the carbon balance?

Answer 34

It’s possible if winters become shorter that less CO2 will be released.

However it may also create a natural response and more CO2 will be absorbed, altering the balance

Question 35

What is primary productivity?

Answer 35

The rate at which plants produce biomass by photosynthesis

Question 36

What is net primary productivity?

Answer 36

The amount of biomass produced by plants, minus energy lost through respiration

Question 37

What are mangroves like as a carbon store?

Answer 37

Mangroves show how how deforestation and land use change can release carbon rapidly.
Mangroves are vital processors, sequestering almost 1.5 tonnes of carbon per hectare

Question 38

Why do mangroves have the ability to store so much carbon?

Answer 38

Mangrove soils consist of thick organic layers of litter, hummus and peat which have a high level of carbon. Submerged below high tides twice a day, their soils are anaerobic (without oxygen). This oxygen poor environment causes very slow break down of plant materials, meaning carbon remains here for thousands of years, resulting in significant carbon storage. This is because bacteria and microbes cannot survive without oxygen

Question 39

How are mangroves being affected by deforestation and clearage?

Answer 39

When cleared, carbon is quickly removed back into the atmosphere. Throughout the world, they are being cleared for tourism, shrimp farms and aquaculture. If just 2% of the world’s mangroves are lost, the amount of carbon released will be 50 times the natural sequestration rate

Question 40

What is tundra like in storing carbon?

Answer 40

Much of the soil in the tundra region is permanently frozen and contains ancient carbon that has been trapped for thousands of years. Microbe activity is only active in the surface layer of the soil when it thaws. The rest of the time, roots and dead/decaying organic matter are frozen, locking any carbon into it

Question 41

In tropical rainforests, where is carbon largely stored?

Answer 41

In trees, plant litter and dead wood. Soils are relatively thin and lacking in nutrients, because litter is decomposed quickly and nutrients consumed by vegetation. Even carbon given off by decomposers is rapidly recycles

Question 42

What would happen if the rainforest died off?

Answer 42

More trees die and decompose or burn, releasing CO2
Less water pumped into atmosphere
Less rainfall
Temperature rise
Drought and wildfire increase in the amazon
More trees die and decompose (positive feedback loop)

Question 43

What is the equation for photosyntheisis?

Answer 43

carbon dioxide + water –» (light energy and chlorophyll above and below arrow) oxygen and carbohydrates