The Carbon Cycle as a System
- Carbon is an essential building block for all life on Earth
- It plays a major role in regulating global climate, particularly temperature and the acidity of rain, rivers, and oceans
- The key carbon cycles operate at a global 'sphere' level - lithosphere, hydrosphere, biosphere etc.
- Carbon cycles have inputs, stores, fluxes/flows and outputs that transfer carbon from one place to another and either deplete or build carbon stores
- Carbon is found in many forms (it bonds easily with other molecules) and the major compounds are;
- Carbon dioxide (CO₂) is a gas found in oceans, soils and the atmosphere and as a waste product in respiration (animal and human)
- Methane (CH₄) is a greenhouse gas found in rocks, oceans, permafrost, soils, etc.
- Hydrocarbons (fossil fuels) found in sedimentary rocks in gas, liquid, or solid form
- Calcium carbonate (CaCO₃) common substance found in limestone rock, shells, eggs, etc.
- Carbon biomolecules are organic molecules including carbohydrates, fats, proteins etc., and form 50% of the total dry mass of living things
- The global carbon system can be subdivided into systems operating on land, oceans and atmosphere, which are inter-related through fluxes/flows, but also as distinct sub-systems in their own right
Diagram of a very simple carbon cycle showing interaction between terrestrial, atmospheric and oceanic sub-systems
- Carbon flows/fluxes between the major stores as two systems:
- Long-term or slow carbon cycle: The movement of carbon between the atmospheric, oceanic and lithospheric stores
- Short-term or fast carbon cycle: The movement of carbon from living things to the atmosphere and oceans
- The atmosphere, oceans and land are linked together transferring carbon in a giant slow-moving system which takes between 100 and 200 million years for carbon to flow through it
- The short-term or fast cycle through the biosphere moves up to a thousand times more carbon in a shorter space of time