Carbon Stores and Fluxes
Carbon Stores & Fluxes
- Carbon is considered to the the ‘building block of life’ as it can be found in all of the earth’s spheres
- It plays a major role in regulating global climate, particularly temperature and the acidity of rain, rivers and oceans
- Atmosphere - as carbon dioxide and compounds such as methane
- Hydrosphere - as dissolved carbon dioxide
- Lithosphere - as carbonates in limestone and fossil fuels (e.g. coal, oil and gas)
- Biosphere - in living and dead organisms
- Cryosphere - biological carbon is stored in permafrost, which prevents bacterial decay
The carbon cycle
- Carbon moves between these spheres as part of the biogeochemical carbon cycle
- The carbon cycle is a closed system so the amount of carbon is constant and finite and it has three components:
- Stores - where carbon is held
- Fluxes (transfers) - the flows which move carbon between stores (from one sphere to another) measured in petagrams or gigatonnes of carbon per year
- Processes - the physical mechanisms which drive the fluxes between stores e.g. photosynthesis and diffusion
- Carbon stores operate as sources (adding carbon to the atmosphere) and sinks (removing carbon from the atmosphere)
- The carbon cycle is balanced (or in equilibrium) when the sources equal the sinks
- When plants and animals die, the carbon they were storing is released back into the atmosphere and the cycle continues
- An undisturbed carbon cycle maintains carbon dioxide levels in the atmosphere and keeps global temperatures steady so Earth can sustain life
- However, when huge amounts of carbon dioxide are released into the atmosphere in a short period of time, the whole cycle can become unbalanced
Geological Carbon Cycle
- This slow part of the cycle is focused on the huge carbon stores in rocks and sediments with reservoir turnover rates of at least 100,000 years
- Organic matter buried deep in sediments are protected from decay which means it takes millions of years to turn into fossil fuels
- Carbon flows through volcanic eruptions, chemical weathering, erosion and sediment formation on the ocean floor
Bio-geochemical Carbon Cycle
- This fast part of the carbon cycle has large fluxes and rapid reservoir turnovers of a few years up to a thousand years
- Carbon is sequestered in and flows between the atmosphere, oceans, ocean sediments, vegetation, soils and freshwater
Exam Tip
Make sure you know the four earth spheres and how they store carbon
Earth’s spheres:
- Atmosphere
- Hydrosphere
- Lithosphere
- Biosphere