The carbon cycle and energy security Flashcards
Petagram
A trillion kg
PgC = Petagram of carbon
Anthropogenic
Human influenced
The carbon cycle
Bio-chemical cycle by which carbon fluxes from one sphere to another. It’s a closed system so the total amount of carbon is constant.
Residency time
How long carbon stays in one sphere
Biggest carbon stores (PgC)
Sedimentary rock - 83m
Intermediate & deep ocean - 37,000
Soil - 2,000
Ocean floor ooze - 1,750
Permafrost - 1,700
Biggest carbon fluxes
(PgC)
Photosynthesis - 123
Respiration & fire - 120
Atmosphere to ocean - 80
Ocean to atmosphere - 78
Fossil fuels and cement - 8
Oil and natural gas formation
Phytoplankton and sea plants die and are covered by silt and sand. If organic content >= 2%, then over millions of years, heat, pressure and anaerobic processes creates oil/gas.
Formation of sedimentary rocks
Made of calcium carbonate, formed from shells/skeletons and coral.
How do volcanoes release CO2
CO2 is released from sedimentary rocks and water through subduction
What happens to sedimentary rocks like limestone
Buried
Melted
Pushed up into terrestrial sphere
Biological pump
-Phytoplankton photosynthesise
-Passed through food chain and respired
-Carbon moves through the ocean via feeding, waste and decomposition
Carbonate pump
-Organisms use calcium carbonate to build their shells and create marine snow when they die
-Many shells dissolve, releasing carbon into ocean currents
-Shells that don’t dissolve build up on the sea floor and turn into limestone via high heat and pressure
Thermohaline conveyor
-Primary mechanism for distributing heat globally
-Water heats and rises at equator, releasing CO2
-Travels to poles, where it cools and sinks
-Travels back to equator through deep ocean, CO2 stays here for hundreds of years
Why are warming oceans an issue
-Water absorbs less CO2, enhancing GW
-Marine heatwaves that disrupt carbon cycle and marine life
Why is the thermohaline conveyor failing and why’s it bad
-Water doesn’t sink at the poles as much, so less circulation
-Less oxygen reaches deep sea, marine life at risk
-Less CO2 absorption via biological/carbonate pumps
-Since 1990, circulation has slowed by a third
Net Primary Productivity
The balance between energy captured by photosynthesis and released by respiration
How does permafrost trap carbon
Too cold for microbes to decompose organic matter
Permafrost positive feedback loop
-Climate warms
-Permafrost thaws
-CO2 and CH4 released
-Climate gets warmer
Greenhouse effect
-Incoming short wave radiation from sun
-Some outgoing long wave radiation radiated back to space
-Some heat trapped by GrGases
Natural systems and threshold risk
Stable state
>Positive feedback processes increase risk
>Reaches threshold (irreversible)
>New stable state (more risk)
Formation of peatlands
Decomposing organic matter accumulates in watery environment without oxygen. Temps must be warm enough for plant growth but cold enough so microbes can’t break down plant matter. Takes thousands of years.
Why are peatlands important
-30% of soil carbon store
-Home to endangered species
-Source of 70% of drinking water
Primary energy
Natural resources that haven’t been converted to energy. Fossil fuels, nuclear, renewables
Secondary energy
What primary energy is converted into (electricity)
Problems with fossil fuels
-Environment
-Finite
-Become more expensive to extract
-Most countries must import them, so are less energy secure
Problems with wind and solar energy
-Don’t produce energy 24/7
-Can’t be stored efficiently
-Sudden spikes can’t be met
Pros/cons of nuclear energy
Pros:
-Uranium will last 1000 years
-Less vulnerable
-Low emissions
Cons:
-Chernobyl (public perception)
-Nuclear waste can’t be dealt with long term
-High tech needed
Biomass
Organic matter used as fuel. eg wood or methane
Biofuel
Fuel derived from biological carbon fixations. eg sugar cane
Biomass pros/cons
Pros:
-Renewable
-Not dependant on technology
-Carbon neutral
Cons:
-Takes land away from farming
-Encourages deforestation
-Reduces biodiversity
-Uses fossil fuels in transportation and ‘kick start burning’
Carbon capture and storage (CCS)
-Can capture up to 90% of CO2 from fossil fuels
-Transported by pipeline or ship
-Stored in depleted oil and gas fields or geological rock formations
Decentralisation of energy
Generating electricity where it will be used, avoiding transport and less vulnerable
What is ocean acidification
CO2 dissolving in the ocean, making its pH closer to 7. By 2100, will be 150% more acidic than in 1861.
Impacts of ocean acidification
-Weakens coral
-Loss of pteropods which are the main food source for marine creatures
-Algal blooms
