Key Role in Supporting Life (AQA A Level Geography)

Carbon & Water as Life-support

• The water and carbon cycles interact directly

• Volcanic eruptions transfer water and carbon from the lithosphere to the atmosphere

• Water has the ability to absorb and transfer CO₂ 

• Water transports weathered material and organic matter, (containing carbon) from land to the oceans as part of the carbon cycle and ocean acidification  

• Calcium carbonate in the ocean is used for coral, shell and skeletal formation by marine animals

• Changes in atmospheric carbon concentrations affect water cycling and precipitation patterns

• Photosynthesis and respiration transfer carbon and water between the biosphere and the atmosphere

• Evapotranspiration increases with higher levels of CO₂ in the atmosphere 

• Changes in the carbon cycle are melting parts of the cryosphere (permafrost), releasing more carbon dioxide and methane into the atmosphere

• Ecosystems play a key role in carbon cycling and the availability of moisture for plant and animal distribution and growth is important

• Limits of water, reduce plant growth; limited plant growth reduces carbon cycling and transfer of nutrients to the soil; lack of nutrients and water exposes soil erosion; soil erosion can lead to desertification

In the atmosphere

• When CO₂ atmospheric concentration levels increase, air temperature increases too

• This raises ocean temperatures and evaporation rates increase transferring more water vapour into the atmosphere

• This amplifies the greenhouse effect

• Water vapour contributes more to the overall natural greenhouse effect than CO₂ 

• Water vapour in the atmosphere is controlled by levels of atmospheric CO₂ 

• The natural greenhouse effect is generated through concentration levels of:

  • 20% carbon dioxide

  • 8% trace gases and aerosols

  • 17% clouds

  • 55% water vapour

• Hydro and halo carbons are industrial gases and contribute to the enhanced greenhouse effect