Earths Life Support System 3. How much change occurs over time in the water and carbon cycles?

  • Created by: DanBish
  • Created on: 05-05-22 16:38
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  • How much change occurs over time in the water and carbon cycles?
    • Human factors can disturb and enhance the natural processes and stores in the water and carbon cycles.
      • Fossil Fuels
        • The combustion of fossil fuels for energy generation purposes releases carbon dioxide into the atmosphere removing it from the lithosphere.
        • Since the industrial revolution fossil fuels have been the main primary energy source for agriculture, industry, domestic use and transport. Combustion of fossil fuels has increased the flow of carbon from the lithosphere to the atmosphere.
        • In 2017 the atmospheric CO2 level was 409 ppm, which can be compared to 277 ppm in preindustrial times.
          • Around 75% of this carbon dioxide comes from the burning of fossil fuels for energy production.
      • Carbon Sequestration
        • The sequestration (removal and storage) of carbon from the atmosphere via artificial or natural means
          • Natural - Trees take in CO2 from atmosphere and convert into carbohydrates in tissues. Planting more trees will increase flow of carbon from atmosphere to biosphere. 
          • Artifical - Carbon capture + storage is industrial process where CO2 removed post-combustion of fossil fuels - passing flue gases through chemical solvent. CO2 transported + stored underground in old oil and gas fields
        • To mitigate against the effects of global climate change international agreements have been put in place to reduce the amount of carbon dioxide in the atmosphere by sequestering (storing) it elsewhere. Very little atmospheric carbon is currently sequestered due to human action.
    • The pathways and processes which control the cycling of water and carbon vary over time.
      • Short term change
        • Water
          • 24 hour period (diurnally)
            • Clouds form, precipitation starts; rising air cools and water vapour condenses; warm air less dense so rises; earths surface heats air cool air
          • Annual period
            • More precipitation + less evapo-transpiration in winter than summer
        • Carbon
          • 24 hour period (diurnally)
            • During the day, plants photo-synthesise, taking in carbon, so CO2 levels fall during the day, and rise at night
          • Annually
            • Plants - Phytoplankton bloom when seas and oceans warm (summer) and temperate forests photo-syntheses more, leading to less carbon
            • Decomposers - De-composition is lower in winter, as the ground is frozen, leading to less carbon in winter, and more in summer
      • Long term change
        • Water
          • During glacial periods the amount of water stored as ice on the land increases. The amount of water stored in oceans and seas decreases. ET rates decrease as plants don’t transpire as much when it is colder and evaporation rates will be low due to the colder temperatures.
          • The last 2.6 million years of Earth’s history is called the Quaternary. It's characterised by series of cold periods (glacials) and warmer periods (inter-glacials). Cold periods see the Earth’s mean temperature fall by 2C.
            • Over geological timescales (millions of years, changes in Earth's temperature have caused significant changes in the water cycle
        • Carbon
          • Photo-synthesis - In glacial periods, less forests and grasslands, and less organisms, so much less photo-synthesis
            • In glacial periods, more ocean nutrients so more phytoplankton
          • Diffusion - Oceans and seas are colder, and so carbon is more easily dissolved into the ocean
          • De-composition - In glacial periods, ground is frozen so de-composition is stopped - more carbon stored in soil.


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