Carbon Flashcards
ADD IMPACTS OF POOR OCEAN HEALTH AND FUTURE UNCERTAINTIES OF CLIMATE CHANGE
Which are the biggest and smallest carbon stores and how many PgC of carbon can they store?
Biggest: Lithosphere - 100,000,000 PgC
Smallest: Atmosphere - 750 PgC
How many times bigger is the hydrosphere store than the atmosphere?
50x bigger
What 2 elements make up the biogeochemical carbon cycle and which one is faster?
Geological and biological cycle, biological is faster
What are the 2 fast biological interactions?
- Atmosphere –> hydrosphere
- Atmosphere –> terrestrial biosphere
What is the flux when carbon moves from atmosphere to surface ocean, what rate does it occur at, and at what rate does the opposite flux occur?
Diffusion, 92 PgC/year, 90 PgC/year
What is the flux when carbon moves from atmosphere to surface ocean through phytoplankton and what % of global carbon sequestration does this account for?
Photosynthesis, 50%
What is the flux when vegetation sequesters carbon from the atmosphere, at what rate does this occur and how many times faster is it than respiration?
Photosynthesis, 123 PgC/year, 1000x faster
What is the flux when carbon moves from vegetation to soil store and at what rate does this occur?
Decomposition, 50 PgC/year
How is carbon in soil store released back into atmosphere?
Fungi/detritivores break it down and release CO2 via respiration
What is the fast biological to slow geological interaction?
Hydrosphere –> lithosphere
What is the process when carbon stored as dissolved CO2 or marine biota moves from surface ocean to deep ocean, at what rate does this occur at, and by what 3 fluxes does this occur through?
Downwelling, 90 PgC/year
1. Biological pump
2. Carbonate pump
3. Physical pump/thermohaline circulation
How much carbon is stored as surface sediment and what process occurs to transform it into CaCO3 or fossil fuels?
0.2 PgC/year, lithification
What process involves carbon moving from the lithosphere to hydrosphere then back to lithosphere again and at what rate does this occur?
Chemical weathering, 0.8 PgC/year
What is the slow geological to fast biological interaction?
Lithosphere –> atmosphere
Via what process can carbon move from lithosphere to atmosphere by anthropogenic activity and at what rate does occur?
Combustion, 35 PgC/year
What is the flux when carbon moves from lithosphere to atmosphere, at what rate does this occur, and how does it occur?
Volcanic outgassing, 0.15 PgC/year, continental crust undergoes subduction so carbon trapped within CaCO3 rocks released as CO2
Describe the process of limestone formation
- Formed from shale particles from marine organisms e.g. crabs
- Organisms die and shell fragments precipitate and sink to ocean floor
- Organic material buried under other organic materials and is lithified to limestone due to increase in pressure/compaction
Describe the process of shale formation
- Organic material precipitates onto ocean floor and covered in mud
- Material is embedded into mud layers and mud exposed to intense heat/pressure so is lithified to form shale
Describe the process of fossil fuel formation
- Organic material precipitates onto ocean floor and covered in mud
- Material decays anaerobically
- If organic material added at faster rate than it decays, becomes a fossil fuel
Describe the full process of chemical weathering to volcanic outgassing
- (Chemical weathering explanation)
- Breaks down rock into component ions e.g. Ca2+ which are transported to ocean in solution
- Ions react with bicarbonate to form CaCO3 which sinks to ocean floor and undergoes lithification to become sedimentary rock
- (Volcanic outgassing explanation)
What are the first 2 steps of an ocean pump PAD?
- Moves carbon from the surface ocean to the deep ocean
- This maintains the diffusion gradient, enabling more carbon to be sequestered from the atmosphere
Describe the process of the biological pump
- Phytoplankton use sunlight to convert CO2 into organic matter via photosynthesis
- Carbon enters food chain when phytoplankton eaten by small fish and some carbon released via respiration
- Marine biota die and precipitate to ocean floor - majority eaten by deep sea consumers or transported by ocean currents
- 0.1% carbon reaches the ocean floor to be stored as surface sediment and compacted into the lithosphere to become CaCO3
Describe the process of the carbonate pump
- Dissolved CO2 and bicarbonate ions generated from chemical weathering held in surface ocean
- Shellfish use carbon to make their shells comprised of CaCO3 and die so CaCO3 precipitates to ocean floor
- If reaches ocean floor, lithified/compacted to form limestone as part of slow geological cycle
Describe the process of the physical pump/thermohaline circulation
- At poles water is colder which leads to sea ice formation
- Increased density of water due to lower temp. and increased salinity
- Nutrient-rich, CO2-containing water sinks (downwelling)
- Colder water can hold more carbon so current picks up more carbon/nutrients
- Current gets closer to tropics so surface water gets warmer, less dense, and rises so upwelling of nutrient-rich waters
- Carbon released back into atmosphere which helps to maintain balance
What are 2 ways that coral reef ecosystems can balance the carbon cycle?
- Sequester carbon via photosynthesis
- Base of food web so maintain levels of biodiversity and ensure strength of biological pump
Describe the process of ocean photosynthesis and how it regulates the composition of the atmosphere
- Phytoplankton/coral use dissolved CO2 in oceans and sunlight to photosynthesise and convert it into carbohydrates for growth
- Maintains diffusion gradient so CO2 levels in atmosphere remain stable as carbon enters biological pump
- Supports maintenance of natural GHE
How do coral reef ecosystems regulate the carbon cycle by being the base of the food web?
- Increase biodiversity so biological pump can function and carbon can work its way up food chain
- More carbon move from surface to deep ocean and diffusion gradient maintained
- Less carbon remaining in surface ocean and atmosphere (small, sensitive store)
What are the 2 ways the terrestrial (vegetation) store regulates the carbon cycle?
- Photosynthesis/respiration
- Decomposition
How does terrestrial photosynthesis/respiration regulate the carbon cycle?
Plants sequester carbon from atmosphere and convert into biomass and photosynthesis 1000x faster than respiration - maintains low CO2 conc. in atmosphere and supports natural GHE
How does terrestrial decomposition regulate the carbon cycle?
Detritivores/fungi break down leaf litter so biomass becomes part of humus soil store - decreases CO2 conc. in atmosphere and supports natural GHE as carbon now held in larger store
By the end of the 19th century, what had UK % forest cover decreased to and what did it increase to after forestry conversions were set up?
From 80% to 10%, 14%
Between 1990-2020, how much afforestation took place in China?
0.63 million km2
What are 2 positives of afforestation?
- Globally, programmes could remove 191 GtC from atmosphere by 2100
- Economic benefits (for every $1 spent on afforestation, $9 in benefits e.g. employment)
What is a negative of afforestation?
Often uses monocultures so less diverse ecosystem and less resilience so would become carbon source if whole forest was destroyed
What are 3 impacts of deforestation on the carbon cycle?
- More wildfires
- Increased EGHE
- Forest dieback (positive feedback mechanism)
What is the case study for deforestation creating more wildfires?
Amazon Drought 2016
What caused the 2016 Amazon drought, by what % did the no. of fires increase by, and how many trees were killed as a result?
El Nino, 36% increase, 2.5 billion trees killed
What did the 2016 Amazon drought turn the Amazon rainforest into and how many estimated tonnes of CO2 did it generate over the following 3 years?
Carbon source, 495 million tonnes
What is the linked evaluation for deforestation creating more wildfires and unbalancing the carbon cycle?
Longer term carbon store in soils is pyrogenic carbonaceous carbon produced from biomass by wildfires
How does forest dieback happen as a result of decreased forest cover due to drought (positive feedback mechanism)?
Less forest cover so trees prioritise growth over health so decreased immunity to pests/pathogens so decrease in canopy layer so more soil baking and less infiltration so more hydrological drought so less forest cover
How does the conversion of grasslands create an unbalanced carbon cycle?
Ploughing causes immediate loss of CO2 from top soils so grasslands become net emittors of carbon, removed grasses and shrubs also can’t pull CO2 from atmosphere
How many tonnes of CO2 would avoiding grassland conversion prevent from being released?
35 million tonnes
What impact does grassland conversion have on humans (application)?
Savanna grasslands are home to Africa’s Big 5 and contribute to Africa’s GDP through tourism
What is the linked evaluation for grassland conversion creating an unbalanced carbon cycle?
Conversion is slowing due to growing challenges associated with water insecurity (irrigation) which will make it more expensive to convert and maintain production
What are 3 impacts of forest loss on humans?
- Increased food insecurity in Indigenous populations
- Increased exposure to malaria
- Increased exposure to zoonotic diseases
How does forest loss cause increased food insecurity in Indigenous populations?
Bushmeat e.g. bats is an important food source as main source of protein and livestock farming isn’t available - less amino acids so malnutrition and decreased immunity to disease
How does forest loss cause increased exposure to malaria?
Ground is less shaded so increased exposure to sunlight so increased standing water (heated by solar radiation) so perfect breeding ground for mosquitoes so increased malaria
By what % did malaria transmission increase in Malaysia after a 10% increase in deforestation?
3% increase
How does forest loss cause increased exposure to zoonotic diseases?
Human encroachment on habitats of forest-dwelling animals caused forced displacement of animals so more contact with human pops. so more likely to transmit disease
What % of new infectious diseases originated in forest-dwelling animals and what is an example?
60%, Ebola
What % of carbon do soils store?
20-30%
How do marshes act as carbon sinks?
Waterlogged all year round so soils are largely anaerobic so slower decomposition so carbon held in dead plant material remains intact rather than being broken down
How do peatlands act as carbon sinks?
Dead organic matter added to soil in waterlogged conditions which occurs at faster rate than decomposition so carbon held in dead plant material remains intact rather than being broken down
How many tonnes of carbon do the Scottish peatlands hold?
1.7 billion tonnes
How much more carbon do mangroves store than rainforests?
5x more carbon
Describe the positive feedback mechanism of permafrost
Increased thawing of permafrost so more decomposition by microbes so CO2 released via respiration and CH4 released from permafrost so increased EGHE so increased thawing of permafrost
Describe the negative feedback mechanism of permafrost
Increased thawing of permafrost so more decomposition via microbes so increased soil nutrient levels so more boreal forest growth more CO2 sequestration via photosynthesis so decreased EGHE so decreased thawing of permafrost