me carbon

• geological carbon cycle -

  • natural cycle
  • moves between land, oceans and atmosphere
  • movement involves number of chemical reactions that create new stores which trap carbon for significant periods of time
  • natural balance between carbon production and absorption
  • disruptions for short periods before equilibrium is restores - eg volcanic eruptions emit large quantities of carbon into atmosphere - or natural climate changes
• geological carbon cycle: natural stores and fluxes -

  • terrestrial carbon - held within the mantle - released into atmosphere as CO2 when volcanoes erupt
  • acid rain (chemical weathering) - CO2 within atmosphere combines with rainfall to produce weak carbonic acid - dissolves carbon-rich rocks, releasing bicarbonates
  • rivers transport weathered carbon and calcium sediments to the oceans where they're deposited
  • organic matter - carbon in plants and animal shells and skeletons - sinks to ocean bed when they die - building up strata of coal, chalk and limestone
• geological carbon cycle: natural stores and fluxes -

  • carbon-rich rocks are subducted along plate boundaries and eventually emerge again when volcanoes erupt
  • metamorphic rocks - presence of intense heating along subduction plate boundaries metamorphoses sedimentary rocks by baking - CO2 is released by the metamorphism of rocks rich in carbonates during this process
• Iceland volcano (2010) -

  • emitted 150,000 - 300,000 tonnes of CO2 per day
  • placing it in same emissions league as small-medium sized European countries (eg Portugal, Ireland)
  • contributed less than 0.3% of global emissions of greenhouse gases in 2010
• bio-geochemical carbon cycle -

  • photosynthesis - removing CO2 from the atmosphere to promote plant growth
  • respiration - releasing CO2 into the atmosphere as animals consume plant growth and breathe
  • decomposition - breaking down organic matter and releasing CO2 into soils
  • combustion - biomass and fossil fuels - releasing CO2 and other greenhouse gases into atmosphere
• carbon measures -

  • gigatonnes (Gt)
  • petagrams (Pg)
  • each Gt or Pg = 1 billion tonnes of carbon
• flux = 


  movement or transfer of carbon between stores - create cycles and feedbacks
• forms of carbon -

  • inorganic - found in rocks as bicarbonates and carbonate - earths biggest carbon store
  • organic - found in plant material
  • gaseous - found as CO2, CH4 and CO
• • can take millions of years for carbon to move through carbon cycle between rocks, soil, rivers, ocean and atmosphere
  • each year no more than 100 million tonnes move through this slow cycle
• biological carbon pump -

  • at the surface of the ocean there's always an exchange of CO2 - some dissolves into water and some vented out into air above
• process of biological carbon pump -

  • oceans surface layer contains tiny pytoplankton - have shells and sequester CO2 through photosynthesis creating calcium carbonate as their shells develop - when they die these carbon-rich micro-organisms sink to the ocean floor and remain there accumulating as sediment
  • this is the carbonate pump - pumps CO2 out of atmosphere and into ocean store
• factors effecting biological carbon pump -

  • naturally efficient system but also fragile
  • phytoplankton require nutrients in vast quantities
  • global movement of of water through the thermohaline circulation maintains the pump
  • slight changes in water temp can alter the flow
  • pollution and turbulence also reduce light penetration and slow pump down
  • each of these factors id vulnerable to climate change - making risk of the pump breaking down
• thermohaline circualtion -

  • water in far North Atlantic is cold and very saline - makes it denser and heavier causing it to sink
  • by sinking - it draws warmer water in from the ocean surface above - this in turn draws water across the ocean surface from the tropics/equatorial region
  • eventually this movement from the tropic draws cold water up from ocean bottom ready to be warmed
• carbon sequestration - 


  the removal and storage of carbon from the atmosphere - usually occurs in oceans forests and soils through photosynthesis
• Gulf Stream -

  • northeasternly Atlantic current
  • 2004 - stalled for 10 days
  • current slowing - speed of ocean circulation slowed by 30% since 2000
  • cause: melting arctic ice was increasing the amount of freshwater entering the north Atlantic
  • the oceans salinity was declining as a result, preventing cold water from sinking there
  • this meant that there was nowhere for the warm waters of the Gulf Stream to go - the North Atlantic with losing its pulling effect
  • gulf stream slowed by 6 million tonnes of water per second over 12 years
• terrestrial stores -

  • terrestrial primary produces sequester carbon through the process of photosynthesis