1.4- Water, Carbon, Climate And Life On Earth

Question 1

Explain the importance of carbon

Answer 1

• carbon is one of 6 crucially important elements in humans
• stored in the form of glucose (monosaccharide) which is a vital respiratory substrate to synthesis ATP, the body’s energy currency
• in trees, the carbon content of leaves and woody matter is approximately 50% of their biomass
• through the food chain, this carbon is ‘passed on’ to animals where it provides much needed energy again
• carbon in the atmosphere is needed for photosynthesis to create carbohydrates needed for plant growth
• also one of the most important greenhouse that controls the Earth’s temperature

Question 2

The atmosphere is an important store of both carbon and water. All organisms need water to

Answer 2

Survive, albeit in different amounts but vital nonetheless

Question 3

An important link between the water and the carbon cycle is

Answer 3

The ability of water to absorb and transfer carbon dioxide- after all, the oceans cover 72% of the Earth’s surface

Question 4

The water and carbon cycle do not act completely independently within the atmosphere- give an example

Answer 4

• the increased emissions of carbon dioxide in the atmosphere is warming the atmosphere
• the increased temperature results in higher evaporation rates and a wetter atmosphere which leads to a positive feedback situation of further warming
• when carbon dioxide concentrations rise, temperatures go up
• the oceans warm up more and more water vapour evaporates into the atmosphere which amplifies the greenhouse heating
• although carbon dioxide contributes less to the overall greenhouse effect than water vapour, scientists have found that that it is carbon dioxide that sets the temperature

Question 5

Give a positive feedback loop regarding the water cycle

Answer 5

• ice reflects radiation (high albedo) from the sun so less heat is absorbed by the surface
• the extent of the Arctic ice has been shrinking alarmingly in recent years, exposing more water with subsequently less reflection (low albedo) and more absorption of heat from the sun
• this warms the water and further melts and reduces ice coverage
• this affects the type and magnitude of water transfers between land, ocean and the atmosphere

Question 6

Explain the local and regional impacts of the positive feedback loop regarding the water cycle

Answer 6

• local and regional impacts of these changes could have profound effects on life on Earth by affecting patterns of precipitation and the availability of freshwater
• political and economic implications are also considerable- no Arctic sea ice for example will affect trading routes, the exploitation of resources and the development of settlements

Question 7

Give a positive feedback loop regarding the carbon cycle

Answer 7

• warmer temperatures in the Arctic are having two opposite effects on the carbon cycle:
  1- higher temperatures have increased the growing season for plants and this has increased the absorption of carbon from the atmosphere (sequestration of carbon dioxide for photosynthesis)

2- higher temperatures however have started to melt the permafrost, particularly in parts of Siberia

• organic matter e.g. plant roots trapped in the frozen ground act as an important carbon store
• it is estimated that there is more carbon currently stored in the permafrost than exists in the atmosphere
• on keying, the organic matter in the permafrost starts to decompose as oxygen is introduced
• the bacteria involved in decomposition produce carbon dioxide and methane as a waste product which bubble to the surface and are released into the atmosphere

CURRENTLY, the Arctic acts as a net carbon store. However, scientists are concerned that if the scale of permafrost melting increases, the balance might tip such, that the Arctic becomes a net carbon sourcing
- in this scenario, this higher temperature and melting permafrost will become part of a highly destructive positive feedback

Question 8

Give an example of a water cycle/ carbon cycle feedback loop

Answer 8

• phytoplankton are microscopic plant-like organisms that live in water
• in common with terrestrial plants, they use the energy of the sun, together with carbon dioxide dissolved in water to photosynthesise, live and grow
• they are primary producers in aquatic ecosystems sustaining the food web with important stores of carbon
• marine phytoplankton release a chemical substance dimethylsulphide (DMS) that may promote the formation of clouds (condensation)over the oceans
• increase in phytoplankton populations associated with warmer temperatures and more sunshine could lead to an increase in cloudiness and global cooling (clouds reduce amount of solar energy reaching the earth’s surface)
• of course, less sunshine might lead to a reduction in the amount of phytoplankton, thereby reducing this cooling effect = EXAMPLE OF NEGATIVE FEEDBACK