Carbon Cycle Flashcards
What is the carbon cycle?
The natural C Cycle is the movement (fluxes) and storage of C between the land, ocean and the atmosphere
What is inorganic Carbon?
Inorganic carbon refers to carbon found in non-living forms
Found as carbon dioxide (CO₂) in the atmosphere carbonates in rocks and minerals, and bicarbonates in water.
It plays a key role in the carbon cycle, moving between the atmosphere, oceans, and Earth’s surface.
What is organic carbon?
Organic carbon is carbon found in living organisms or derived from them, such as in plants, animals, and decaying matter.
It plays a key role in the carbon cycle, moving between organisms, the atmosphere, soil, and oceans.
What is Gaseous carbon and where is it found?
Gaseous carbon is carbon in the form of carbon dioxide (CO₂) in the atmosphere, which plays a role in photosynthesis, respiration, and the greenhouse effect.
Found in C02 and CH4
What is carbon sequestration?
It is the capturing, storage and transfer of C from the atmosphere to other stores and can be natural and artificial (e.g. Carbon Capture and Storage).
A plant sequesters C when it photosynthesises and stores the C in its mass.
Where is carbon stored, and which is the highest store and which is the lowest store?
Highest:
Lithosphere
Hydrosphere
Pedosphere
Cryosphere
Atmosphere
Biosphere
Lowest:
Large
Hamster
Pigs
Cry
At
Butchers
What are the lithosphere stores?
- Marine sediments (ocean floor) and sedimentary rocks (biggest store). Long-term (up to millions of years).
- Fossil fuel deposits (e.g. coal) – originally long-term, but dynamic due to human exploitation
- Soil organic matter – mid-term (deforestation, agriculture and land-use change are affecting this store)
What are the hydrosphere stores?
Oceans – dynamic.
The second biggest store, but only a tiny fraction of that stored in the lithosphere.
The C is constantly being utilised by marine organisms, lost as an output (diffusion) to the lithosphere (sedimentation on the ocean floor), or gains from inputs from rivers and coastal weathering and erosion
What are Atmosphere stores?
Stores Co2
A dynamic store
Human activity has caused CO2 levels to increase by 40% since 1750 and is accelerating in the 21st Century.
What are Biosphere stores?
Terrestrial plants (mid-term, but very dynamic). Vulnerable to Climate Change deforestation.
What are Cryosphere stores?
Methyl clathrates are molecules of methane that are frozen into ice crystals. If the temperature rises or pressure changes, the ice that imprisons the methane will break apart, and the methane will escape.
Organic matter frozen in permafrost. Permafrost is permanently frozen ground, and it contains a lot of frozen organic matter. This organic matter is made of dead plants and animals that have been frozen deep in permafrost for thousands of years. The carbon in this organic matter is locked up because it is frozen. With global warming, if this permafrost melts the organic matter will decay, and this will release carbon dioxide or methane into the atmosphere.
What are fluxes between carbon stores?
The transfers in the C Cycle cause changes in C stores over varying degree of time.
They can be categorised as either fast flows or slow flows.
Why is photosynthesis a fast flow?
Plants sequester C by converting CO2 from the atmosphere and water from the soil into O2 and glucose using light energy. This helps to maintain the balance between O2 and CO2 in the atmosphere.
Why is respiration a fast flow?
Respiration occurs when plants and animals convert O2 and glucose into energy, which is opposite of photosynthesis. Plants photosynthesise by day and respire at night. Plants are net oxygen producers because they absorb more than they emit.
Why is combustion a fast flow?
When fossil fuels and organic matter e.g. trees are burnt they emit CO2 into the atmosphere. This is obviously a human influence on the C Cycle (indirectly for some wildfires due to CC).
Why is decomposition a fast flow?
When living organisms die they are broken down by decomposers (e.g. bacteria and fungi) which respire returning CO2 in to the atmosphere. Some organic matter is returned to the soil where it is stored.
During the water cycle, why is diffusion a fast flow?
The oceans can absorb CO2 from the atmosphere which has increased ocean acidity by 30% in the last 250 years, which is harming aquatic life by causing coral bleaching. At the surface, where air meets water, carbon dioxide gas dissolves in and ventilates out of the ocean in a steady exchange with the atmosphere.
Why is sedimentation a slow flow?
Can happen on land or sea floor.
When shelled marine organisms die, their shell fragments sink to the ocean floor and become lithified over time to form limestone.
Organic matter from vegetation can be compacted over time to form fossil fuel deposits.
Why is weathering and erosion a slow flow?
(Long Answer)
Inorganic C is released slowly through weathering e.g. solution of alkaline rocks (e.g. chalk) by carbonic acid in rain/river/sea water. The C is moved through the water cycle and enters the oceans. Marine organisms use the C to build their shells – eventually die and sedimentation occurs on the sea floor. Increasing CO2 levels in the atmosphere are accelerating this process.
Why is volcanic outgassing a slow flow?
Pockets of carbon dioxide exist in the Earth’s crust. Volcanic eruptions and earthquakes can release these gas pockets.
Outgassing is the release of gas, previously dissolved, trapped, frozen or absorbed in some material (e.g. rock). It occurs mainly along mid-ocean ridges, subduction zones and at magma hotspots.
How long can carbon remain in different stores? (Residence time)
Lithosphere – from 10,000 – 300,000,000 years (sedimentary rocks)
Hydrosphere – ocean surface – up to 25 years; deep oceans – up to 1250 years
Cryosphere – up to millions of years
Atmosphere – up to 6 years
Biosphere – average is 13 years (but can be much shorter)
How does chemical weathering impact the carbon cycle?
(Long answer)
- Rainwater reacts with atmospheric CO2 to form a weak carbonic acid. The rain reaches the surface and reacts with some surface minerals slowly dissolving them into their component ions.
- Calcium ions are transported by rivers to the ocean. These combine with bicarbonate ions to form CaCO3 and precipitate out as minerals such as calcite.
- Deposition and burial turns the calcite into limestone.
- The ocean floor is eventually subducted under continental plates.
- Some of the C rises up within magma and degassed as CO2 back into the atmosphere.
How does volcanic outgassing impact the carbon cycle?
- Outgassing occurs at subduction zones and spreading ridges; hot springs and geysers and as direct emissions from fractures in the Earth’s crust
- Volcanoes currently emit 0.15-0.26 Gt CO2 annually. In comparison, humans emit about 35 Gt, mainly from fossil fuel use, so volcanic degassing is relatively insignificant
- The CO2 emitted by both active volcanoes and at constructive plate margins is roughly the same
What is oceanic sequestration?
Oceanic sequestration refers to the process by which the ocean absorbs and stores carbon dioxide (CO2) from the atmosphere.
The CO2 gas exchange flux between the oceans and atmosphere operates on a timescale of over several hundred years. There is also a significant input of both organic C and carbonate ions from rivers. Only a small proportion of this will end up buried in sediments, but these are important long-term stores operating over millennia, unlike most terrestrial systems.
The exchange of CO2 between the oceans and atmosphere takes place over hundreds of years. Rivers also contribute organic carbon and carbonate ions, with only a small portion getting buried in sediments. These buried materials act as important long-term carbon stores, lasting thousands of years, unlike most land-based systems. (SIMPLIFIED)
What is the biological pump?
The biological (organic) pump is driven by ocean phytoplankton absorbing CO2 via photosynthesis (carbon fixation)
These organisms form the bottom of the marine food web, and live in the ocean’s surface layer
Phytoplankton are consumed by other organisms and carbon is transferred along food chains
Organic carbon may eventually be transferred to the deep ocean when dead organisms sink towards the ocean floor
What is the physical pump?
The physical (inorganic) pump involves the movement of carbon dioxide from the atmosphere to the ocean by a process called diffusion
CO2 dissolved in the surface of the ocean can be transferred to the deep ocean in areas where cold dense surface waters sink
This downwelling carries carbon molecules to great depths where they may remain for centuries
CO2 diffusion determines the acidity of the oceans
What is the carbonate pump?
Formation of sediment from dead organisms - sedimentation sequesters
What is thermohaline circulation?
Ocean currents circulate C – it takes 1000 years for a cubic metre of water to travel around the system
Warm surface waters are depleted of nutrients and CO2 but are enriched as they sink towards the bottom layers of the ocean
The foundation of the Earth’s food chain depends on the cool, nutrient-rich waters that support algae and seaweed growth. C flows from the carbonate pump cycle in surface waters to the deep ocean
The balance of C uptake (92 PgC) and C loss (90PgC) from the ocean is dependent on organic and inorganic processes acting in both surface water and deep ocean.
Increased ocean acidification, due to Climate Change, means that oceans have less capacity to sequester C than previously – therefore more CO2 in the atmosphere
What is terrestrial sequestration, and how does the process occur?
Terrestrial sequestration is the process by which carbon dioxide (CO2) is captured and stored on land
The fastest part of the C Cycle – seconds, minutes and years
Primary producers (plants) take C out of the atmosphere through photosynthesis and release it back via respiration
When consumers eat plants, C from the plant becomes part of fats and proteins
Micro-organisms and detritus feeders such as beetles feed on waste material from animals – C is transferred to them
Decomposers then take up C from dead plants and animals
C storage is mainly in plants and soils, with smaller amounts in animals and micro-organisms (bacteria and fungi)
The largest store is in trees, which can live hundreds and even thousands of years
Carbon fluxes vary diurnally – during the day positive from atmosphere to the ecosystem and negative at night
Carbon fluxes vary seasonally – in N hemisphere winter atmospheric CO2 rises, but falls again during the spring
What is biological carbon?
Soils store 20-30% of global C – although location is important when considering whether it is a sink or a source of C
There are 2 sources of C in soils. Arid and semi-arid soils contain inorganic C (very little plant life)
The most important store is from organic sources through plant photosynthesis and decomposition. C can be stored as dead organic matter in soils for years, decades or centuries in colder climates and wetlands
Humus is the dark layer in a soil where decomposition is taking place.
Humus soils are 60% C and are important for sequestration
What does the capacity of soil to store carbon depends on?
Climate – rapid decomposition occurs at higher temperatures or under waterlogged conditions. Places with higher rainfall have increased potential C storage
Soil type – clay soils have higher C content than sandy soils
Management and use of soils – soils lose C through cultivation and disturbance – a huge factor on intensively farmed grasslands (US/Russia)
What role does C play in regulating the Earth’s average temperature?
Green house effect, fossil fuel combustion
What does NPP refer to?
Net primary producer - amounts of energy or biomass produced by plants through photosynthesis
Which ecosystems have the highest NPP?
Rainforests, estuaries and corals = high rates of sunlight
What does the concept of ‘fertilisation’ mean?
human activity speeds up rates of photosynthesis, however plant growth is limited by nutrient and water availability needed in order to utilise CO2
What does soil health depend on?
depends on the amount of organic carbon stored in the soil, this depends on its inputs and outputs
What is meant by the term ‘soil carbon balance’?
if plant residue is added to the soil at a faster rate than soil organisms covert it to CO2, carbon will gradually be removed from the atmosphere and sequestered in the soil
Why does the selva-tropic rainforest have the highest nutrient cycling
warm, humid, moist condition
Why does the tundra (permafrost) ecosystem have the highest density of carbon storage?
slow decomposition rates
How does fossil fuel combustion lead to ‘climate forcing and what are the global and regional implications of this?
increase co2, enhance greenhouse effect, increase global warming
Why is the concept of ‘positive feedback’ actually negative for the global climate, in reality?
positive feedback accelerates temperature rise which is bad for the environment
Are there any potential positive aspects of global climate change?
crops and other plants grow better in the presence of higher carbon dioxide levels and seem to be more drought-tolerant
What are the implications of global warming for the hydrological cycle? Give specific examples.
speeds the processes up, enhances evapotranspiration, precipitation, and intense precipitation
What is energy security?
Is the uninterrupted availability of energy sources at an affordable price
What is long term energy security?
Long-term security mainly deals with timely investments to supply energy in line with economic developments and environmental needs
What is short term energy security?
Short-term energy security focuses on the ability of the energy system to react promptly to sudden changes in the balance between energy demand and energy supply
What is energy insecurity?
A measure of how efficiently a country is using its energy and is calculated as units of energy used per unit of GDP
High intensity = high price
Energy intensity decreases with economic development (service sector economies use less energy than manufacturing economies)
What is primary energy?
Primary energy is the energy found in nature that has not been subjected to any human engineered conversion process. It encompasses energy contained in raw fuels and other forms of energy, including waste, received as input to a system. Primary energy can be non-renewable or renewable.
What is secondary energy?
Secondary energy: When we convert primary energy into a transportable form we speak of secondary energy. For example, when we burn coal in a power plant to produce electricity, electricity is a form of secondary energy. Secondary energy includes liquid fuels (such as petrol and diesel – which are refined oil), electricity, and heat.
What is biomass?
Biomass uses waste from plants or animals that can be converted to energy. Examples of biomass are plant matter, food waste and human and animal waste. Biomass can be gassy and smelly
What are the factors affecting energy consumption?
Physical availability - having access within country is cheaper than imports. Accessibility is also important - surface coal mining is much easier and cheaper than deep coal mining
Technology - particularly important in coal/gas/oil exploration, although uses a lot of energy
Cost - includes physical exploitation of resources (e.g oil/gas); processing (converting primary energy to secondary) and delivery to the consumer
Economic development– developed countries have relatively high
energy consumption (see previous graph)
Climate– places with temperature extremes (e.g. Canada/Saudi
Arabia) need more energy to provide a more comfortable living
environment
Environmental priorities– countries with ‘greener’ energy policies
will prioritise renewable energy use. The population will be more
aware of the environmental impact and consumption may also fall
What was Britain’s 2024 energy mix?
Gas = 26.6%
Wind = 34.8%
Nuclear = 11.1%
Biomass = 6.6%
Coal = 0.9%
Solar = 2.1%
Imports = 13.9%
Hydro = 2.9%
Storage = 1%
What is the difference between slow and fast flows?
The fast carbon cycle moves carbon through life forms, while the slow carbon cycle moves carbon through rocks, soil, oceans, and the atmosphere. The fast cycle is faster, and it’s measured in a lifespan. The slow cycle is slower, and it can take millions of years.
Why are forests important to us?
Forests functions and threats:
- 1.1% of the global economy income
- 13.2 million ‘formal’ and 41 million ‘informal’ jobs
- Improve food and nutrition security
- Source of livestock fodder in arid and semi-arid areas
- Fuelwood source for one in three people globally for cooking and boiling drinking water
- A genetic pool: a source for improving plant strains and medicine
Regulation of Earth Systems:
- Earth’s ‘green lungs’ regulating climate, floods, disease
- Water purification
Cultural Value:
- Aesthetic
- Spiritual
- Educational
- Recreational
Supporting functions:
- Nutrient cycling
- Soil formation
- Primary production
Provision of goods:
- Food
- Freshwater
- Wood and fibre
- Fuel
What is the environment Kuznet’s curve?
Measures the correlation between environmental degradation and economic growth (GDP per capita)
- Pre industrial economies = environment worsens
- Industrial economies = turning point
- Post-industrial economies = environment improves
Societies reach a ‘tipping point’ where exploitation changes to protection because?
Countries become wealthier and move towards service - sector economies
Education about the importance of protecting the environment increases - awareness increases participation
Aid given to poorer countries can reduce environmental exploitation
Political systems can change in a country and environmental laws will be enforced more strictly - TNC’s may also be
forced to comply with environmental regulations too
Kuznet’s curve - Uk v China case study research
Uk = post industrial society and according to the model the environment should be improving
China = just before the ‘tipping point’ as they have a mixture of an industrial economy and national parks
Deforestation creates
- Water-related risks (landslides, local floods and droughts)
- An ongoing loss of biodiversity
- Loss of direct reliance by many indigenous people
- Some cultures and religions see forests as sacred
- Leisure and tourism
What are carbon stores?
Where carbon is held
What are sources?
adding carbon to the atmosphere
What are sinks?
removing carbon from the atmosphere
How does chemical weathering impact the carbon cycle?
(Summarised)
Rainwater reacts with CO2 to form carbonic acid, which dissolves surface minerals into ions.
Calcium ions are carried by rivers to the ocean, where they combine with bicarbonate to form calcium carbonate (CaCO3), which precipitates as calcite.
Over time, this calcite becomes limestone through deposition and burial.
Eventually, the ocean floor is subducted, and some carbon is released as CO2 from magma back into the atmosphere.
Why are weathering and erosion a slow flow?
(Summarised Answer)
Inorganic carbon is released through weathering, such as the dissolution of alkaline rocks like chalk by carbonic acid in water.
This carbon moves through the water cycle and enters the oceans, where marine organisms use it to build shells.
When these organisms die, their remains are deposited on the sea floor.
Rising CO2 levels are accelerating this process.
What is Sedimentation?
Sedimentation is the process where particles, like sand, mud, or the remains of organisms, settle and build up at the bottom of a body of water, forming layers over time.
What is Lithification?
Lithification is the process by which sediments are compacted and cemented together over time to form solid rock.
It happens when layers of sediment build up, and pressure from above squeezes the particles together while minerals in the water act as glue, binding them into rock (limestone).
What is a carbon sink?
A carbon sink is any reservoir that absorbs more carbon than it releases.
What is a carbon store?
A carbon store e.g. lithosphere maintains a constant amount of carbon
How much greater is the ocean as a carbon sink compared to the atmosphere?
The oceans are the Earth’s largest C sink (50x greater than in the atmosphere.)
Where is 93% of carbon stored?
In undersea algae, plants and coral, with the remainder in dissolved form
What are the most productive biomes?
Tropical rainforests, savannah and grasslands which account for half of global net primary producers
Is carbon most active in top soil or lower soil?
C cycling and formation is most active in topsoil
In permafrost regions how much C is stored deeper than 30cm?
Over 61% of C is stored deeper than 30cm
What is pyrogenic carbonaceous matter?
Matter produced during wildfires is resistant to microbial decomposition and can remain in soils for long periods
What is renewable energy?
Renewable energy comes from naturally replenished sources like solar, wind, and hydro, and is sustainable over time.
What is recyclable energy?
Recyclable energy refers to the reuse or recovery of energy, often from waste or industrial byproducts.
What does anthropogenic mean?
Human induced
What are the two types of feedback loops?
Positive = bad
Negative = good
When talking about ocean warming which part is affected?
Top sea layer/surface
Why are countries still buying fossil fuels from Russia in 2023?
They cannot afford to not purchase from Russia die to dependence/reliance
What are types of conventional fossil fuel energy resources?
Gas, Coal, Oil
What is the difference between recyclable and renewable energy?
The main difference is that renewable energy is naturally replenishing, while recyclable energy focuses on reusing or recovering energy that would otherwise be wasted.
What are the key factors driving anthropogenic (human induced) greenhouse gas emissions?
Demographic change - population increase
Economic change - increased globalisation and movement of goods, rapid industrialisation of NIC’s, new resource finds, less desire for TNC’s to ‘go green’ due to the recent economic downturn
Other factors - cultural and attitudinal factors, changing lifestyles as countries develop, globalisation of consumerism
