carbon cycle

• carbon cycle

  closed system w/ no inputs or outputs

  consists of 3 parts

  • stores = where carbon is found
  • fluxes = flows of carbon between stores and can differ in size
  • processes = physical ways carbon fluxes happen
• carbon cycle

  roles

  • balancing earths systems
  • stored in atmosphere, on land and in oceans and moved between these various processes
• carbon stores

  measured in petagrams of carbon (PgC)

  • hydrosphere (38000 PgC) = dissolved carbon in bodies of water
  • lithosphere (100000PgC) = rocks like calcium carbonate and fossil fuels
  • biosphere (2000 PgC) = animals and plants dead or living
  • atmosphere (750 PgC) = gases like carbon dioxide
• biochemical carbon stores

  terrestrial

  • carbon found in every living organism on planet so they are stores of carbon
  • when they decay it can be converted into other carbon stores by going into the soil
  • other terrestrial carbon is stored within mantle and can be converted into atmospheric carbon via the process of 'out gassing' by volcanoes where they let out carbon dioxide during eruptions
• biochemical carbon stores

  role of organisms

  • photosynthesis = plants remove co2 from atmosphere to produce energy for plant growth
  • respiration = all living organisms releases co2 as they breath and grow
  • decomposition = living organisms dieing they are broken down which releases co2 into the soil
  • combustion - burning of biomass or fossil fuels both by man and in natural wildfires it releases co2 back into atmosphere
• biochemical carbon stores

  oceans

  • aquatic plants and animals (organic matter) fall to ocean bed after death
  • due to compression and cementation they form into sedimentary rock
  • during these processes crude oil and natural gas can form
• biochemical carbon stores

  atmosphere

  • co2 stored as a gas in the atmosphere
  • carbon can leave atmosphere when mixing with water vapour so when precipitation happens it falls as carbonic acid aka ACID RAIN
• biochemical carbon stores

  fluxes varying in size

  • carbon cycle can happen at different scales and timeframes
  • quickest happens in seconds = photosynthesis
  • longest can take years eg dead organic matter returning to soil
  • some organic material will be buried in the sea and form into sedimentary rock = veryyyy slow process
• geological carbon stores

  formation of crude oil

  • starts with the settling of fine grained sediments and biologically degraded materials and a minimum of 2% organic carbon
  • serieis of anaerobic reactions (reactions happening without o2) turn majority of organic carbon into a liquid ->crude oil
  • bc its light not dense, crude oil may migrate up thro layers of permeable or porous rocks but if it reaches impermeable rock it will become trapped
• geological carbon stores

  formation of natural gas

  • methane (CH4) = natural gas created as a by product during formation of coal and crude oil
  • natural gas is trapped within same sedimentary layers that coal and crude oil are found in
• geological carbon stores

  formation of coal

  • formed on land not in the oceans like sedimentary rocks
  • when land bases plants die and enter into swamps they slowly settle and compact to form peat and coal
  • coal takes millions of years to form depending om the temp and pressures
• geological carbon stores

  formation of limestone

  • phytoplankton have carbon based shells and other marine organisms also have shells or skeletons formed from calcium carbonate
  • when they die they sink to the bottom of the ocean
  • as more sediment falls on top of them they are comapcted so when its reached around 100m in depth the pressure and chemical reactions cause cementation to take place leading to formation of limestone
• geological processes releasing carbon

  chemical weathering of rocks

  • wearing away rocks by chemical reactions causing material to dissolve thro solution, hydrolusis and oxidation
  • slightly acidic rain (carbonic acid) forms co2 in the atmosphere being dissovled into rainwater
  • when acidic rain hits carbon rich rocks eg limestone it can dissovle the material and form calcium carbonate
  • these dissovled materials are then transported down rivers and deposited into the sea forming sedimentary rock
• geological processes releasing carbon

  volcanic out gassing

  • extreme heat from tectonic processes leads to sedimentary rocks undergoing chemical changes causing co2 to be released into atmosphere
  • volcanic activity happens at constructive and destructive plate boundaries which causes co2 to be released in out gassing which is common in geo thermal locations eg new zealand
• carbon in the food chain

  terrestrial primary consumers

  • primary producers (~plants) = first organisms in food chain
  • they can make their own energy from sunlight and co2 thro photosynthesis ( green plants sequester co2 thro chloroplasts in their leaves to produce energy
• carbon in the food chain

  respiration

  • all living organisms respire and contain carbon
  • by respiring = release co2 into atmosphere
• carbon in the food chain

  consumers

  • eat other organisms below them in the food chain
  • primary consumers - first organims to eat plants eg rabbits eating bugs
  • then return carbon that the primary producer sequestered back into the atmosphere thro process of respiration
• carbon in the food chain

  decomposers

  • biological decomposers consume dead organic matter and return the carbon to the atmosphere thro respiration
• sequestion by phytoplankton

  photosynthesis in surface waters

  • phytoplankton take co2 out of atmosphere thro photosynthesis
  • all these organisms sequester (take up) co2 and build their shells from calcium carbonate transforming carbon=in in atmosphere to their bio carbon
  • these organisms are consumed by other organisms eg zooplankton which also respire returning some of the carbon into atmosphere
• sequestration by phytoplankton

  carbonate shells sink

  • phytoplankton and other aquatic organisms die they sink to ocean floor
  • these organims can accumualte as sediment then eventually transformed to sedimentary rock
  • can also be decomposed (broken down) by bacteria which can return carbon into the ocean in the form of dissovled organic carbon
• sequestration by phytoplankton

  carbonate pump

  • process of carbon entering and moving around ocean = carbonate pump
  • w/o oceans acting as a store for carbon levels of atmospheric co2 conc would be significantly higher
• sequestration by phytoplankton

  thermohaline circulation

  • refers to global movement of water
  • cold water sinks to the bottom of the ocean while warm water rises to the surface (Moving towards cooler water)
  • process is the reason for the UKs relative warmth in compariosn to other locations at the same latitude
  • bc warm caribbean water passes the UK as it moves northward towards the poles
  • slight changes in temp can change the operation of both the thermohaline circulation and carbonate pump
• dead organic matter

  soils

  • dead organic matter found in the ground or in the soil still contains biological carbon
  • bio carbon can be returned to atmosphere when decomposed by bio decomposers
  • rate bio carbon is returned to atmosphere is dependant on temp and climate
  • human activity eg deforestation and land use change can speed it up
• dead organic matter

  mangroves

  • found at tropical coastlines and sequester 1.5 metric tonnes of carbon per hectare every year
  • mangrove soil consist of layers of litter humus and peat which contain >10% carbon
  • due to being submerged beneath the tidal water twice a day the soils are anaerobic (w/o o2)
  • bio decomposers cannot survive w/o o2 so breakdown of bio material takes a lot longer
• dead organic matter

  tundra soil

  • permanently low temps
  • soil contains ancient carbon = permanently frozen stopping microbe activity that decays the material
  • microbe activity only happens once the surface layer thaws
  • tundra is a massive carbon store holding carbon for 100s of thousands of years
• greenhouse effect

  greenhouse gases

  • gases that lead to ghe
  • inc methane (CH4) and carbon dioxide (co2)
  • naturally emitted thro respiration and outgassing
• greenhouse effect

  natural greenhouse effect

  • solar radiation enters earths atmosphere it passes thro the green gases layer
  • solar radiation is mostly absorbed by earths surfave whilst some is reflected
  • some of this reflected radiation will pass back into space
  • gg layer acts as a blankey which stops the majority of reflected radiation leaving the earths atmosphere again
  • allows earth to be at a high enough temp to support life
• greenhouse effect

  enhanced greenhouse effect

  • human activity causes there to be an increase in greenhouse gases in atmosphere eg burning of fossil fuels in vehicles
  • these ghg add to the natural blanket layer in the atmosphere resulting in a larger amount of reflected radiation being retianed in the earths atmospehre than normal leading tp warmer temps
• impacts of the ghe

  temp distribution

  • diff locations recieve diff levels of solar energy
  • angle of suns rays result in equator recieving most conc radiation whilst at the poles the saem radiation is dispersed over a greater distance
• impacts of the greenhouse effect

  albedo effect

  • colour of surface of the earth impacts how much radiation is absorbed= albedo effect
  • white snow of glacierrs and ice caps reflects majority of heat while dark oceans and forests absorb heat
  • heat is then redistubuted via air circulation
• impacts of ghe

  precipitation distribution

  • heating of the eaths surfave leads to warm air rising cooling and condensing to form clouds
  • intense solar radiation at equator leads to warm air rising causing high levels of rainfall all year
  • at 30N and 30S air cools and sinks again resulting in high pressure where rainfall is rare
  • at 60N and S diff air masses meet resulting i frontal rainfall
  • poles are cold resulting in air sinking causing little rainfall
• atmospheric regulation

  soil health

  • amount of carbon stored in soil depends on

  1. size of store in diff biomes
  2. total input (amount of plant litter animal waste)
  3. total output (amount of decomposition erosion and uptake by plant growth)

  • stored carbon is important for soil health, healthy soil will be dark in colour contain worms and organisms and have good infiltration rates
• atmospheric regulation

  photosynthesis role

  • marine phytoplankton sequesters around 5-15Gt of carbon a year
  • terrestrial primary producers sequester around 100-120 Gt of carbon a year
  • tropical rainforests can sequester 2200g of carbon per m^2 a year which is significantly larger than oceans
  • arctic sea ice melt is increasing leading to greater areas of oceans being exposed to sunlight for longer causing algal bloom
  • algae sequesters co2 but alters marine ecosystmes
• atmospheric regulation

  seasonal change

  • cooler weather and reduced sunlight = less photosynthesis occuring = less co2 taken up by plants
  • diff in global atmospheric carbon is therefore higher in the winter than summer
  • climate change = winters could be shorter = less co2 released
• fossil fuel combustion

  when?

  • oil in petrol form is combusted (burned) in cars
  • natural gas used to heat our stoves when cooking
  • all types of fossil fuels combustion release co2 as a by product
• fossil fuel combustion

  balance

  • carbon cycle is in 'equilibruim' between stores and sinks
  • since industrialisation combustion of FF has increases
  • resulting in conc of atmospheric co2 to increase linked to increases in global temps due to enhancing the ghe
• fossil fuel combustion

  impact on climate

  • globally = higher levels of atmospheric co2 increase global temps
  • locally impacts vary
  • eastern and northen eu = warmer winters
  • southern EU = warmer summers
  • n eu = increase in precipitation
  • southern eu = less rain
  • decreases water availibility and increase likelihood of drought and forest fires in s eu
• fossil fuel combustion

  extreme weather events

  • with the changes in temp and precipitation = likely extreme weather events will increase too
  • areas hit by tropical storms will increase as will their intensity
• impact on the arctic

  effect on permafrost

  • warmer temp = more permeable frost to thaw while releases the stored co2 and CH4
  • leads to more ghg impacting ghe causing more permafrost to thaw
  • carbon msy remain in new vegetation that is able to grow now permafrost hsd thawed which may allow carbon to be stored via photosynthesis
• impact on the arctic

  snow and ice changes

  • sea ice melts and snow cover is reduced with increasing temp
  • reduces albedo effect = more solar radiation to be absorbed by the earth resutling in an even greater increases in temp
  • Change in habitat is devasting for ecosystem depending on it