Geography Physical

• Carbon mitigation strategies

  • Growing seagrass/ kelp: captures CO2 35x faster than forests
  • Afforestation
• Carbon stores

  1. Largest store = terrestrial, sedimentary rocks and ocean sediments
  2. Geological carbon = from formation of sedimentary carbonate rocks (limestone and chalk)
  3. Biologically derived carbon = shale, coal
• How much carbon is there?

  Measure in gigatonnes (Gt) or petagrams (Pg).

  Each Gt or Pg = 1 billion tonnes, 180Gt has been added to atmosphere as a result of burning fossil fuels
• Forms of carbon

  1. Inorganic - found in rocks as bicarbonates and carbonate (Earth's largest carbon store)
  2. Organic - plant material
  3. Gaseous - CO2, CH4, CO
• Fluxes


  movement or transfer of carbon between stores
• Variations in carbon fluxes:

  Fast - seconds, photosynthesis, respiration - sunlight, moisture and temperature all control the speed

  Slow - dead organic material, decomposition, can become sedimentary rocks (limestone, coal) or hydrocarbons (oil, natural gas)
• Sinks - places that absorb more carbon than they release
• Sources - places that release more carbon than they absorb
• The global carbon cycle involves the movement of carbon through different reservoirs on Earth.
• The carbon cycle involves both physical processes such as weathering and chemical reactions like combustion.
• Carbon is transferred from one reservoir to another by various processes such as weathering, erosion, deposition, volcanism, combustion, and photosynthesis.
• The ocean acts as a major sink for carbon dioxide due to its large volume and ability to dissolve CO2.
• Biological carbon pump: The process by which carbon is transferred between the atmosphere and the oceans.
• Process of biological carbon pump:

  • Phytoplankton sequester CO2 through photosynthesis, creating calcium carbonate as their shells develop.
  • Die, sink to ocean floor, accumulate as sediment
  • = carbonate pump, pumps CO2 out of atmosphere into oceans
• Biological carbon pump influences:

  Fragile, phytoplankton require vast nutrients

  Thermohaline circulation maintains the pump
• Thermohaline circulation

  Colder denser water in the far north atlantic sinks, draws warmer ocean water in from ocean surface above, draws water from tropics region.

  Movement from tropics draws cold water from ocean bottom, ready to be warmed again
• Terrestrial stores


  sequester carbon through photosynthesis

  • Primary producers, rapid, use solar energy to produce biomass
  • biological decomposers (insects)
• carbon fixation; gaseous carbon into living organic carbons that grow
• tundra soils: soil permanently frozen, contains ancient carbon.

  Microbe activity is only active in the surface layer of the soil

  other carbon, locked in
• Mangroves and carbon:

  sequester almost 1.5 metric tonnes of carbon per hectare every year

  m soils = thick organic layers of litter, humus and peat, high levels of carbon (over 10%).

  anaerobic soils, decomposition is slow, little of the carbon can be respired, remains intact

  if 2% of world's mangroves are lost, amount of carbon released will be 50x the natural sequestration rate
• Greenhouse gases (ghg) :

  CO2: 0.04% of Earth's atmosphere, 89% of ghg produced, highest radiative forcing effect

  CH4: 21X more powerful than CO2, 250% increase since 1850

  N2O: traps infared radiation changing to nitric oxide that destroys ozone

  Halocarbons: 3000 more powerful, 1% of ghg produced
• Carbon capture and storage (CCS)


  This involves capturing CO2 emissions from power plants and industrial processes and storing them underground in rock formations or other geological structures.
• Soil carbon sequestration

  Certain farming practices, such as reducing tillage and incorporating cover crops, can increase the amount of carbon stored in soil, helping to mitigate climate change.
• Methane and nitrous oxide reduction

  Reducing emissions of these potent greenhouse gases through various strategies, such as improving manure management, reducing food waste, and promoting sustainable agriculture, can help to slow down climate change.
• Energy efficiency


  Improving energy efficiency in buildings, transportation, and industrial processes can help to reduce CO2 emissions by using less energy to perform the same tasks.
• Reducing fossil fuel use

  Transitioning to cleaner, renewable energy sources can help to reduce CO2 emissions from burning fossil fuels.
• Coast


  An open system that receives inputs from outside the system and transfers outputs away from the coast into other systems (terrestrial, atmospheric or oceanic)
• Sediment cell


  A section of coast that is typically considered a closed-system in terms of sediment
• Components of a sediment cell


  • Sources (where sediment originates from)
  • Through flows (movement of sediment along the shore through longshore drift)
  • Sinks (locations where deposition of sediment dominates)
• Dynamic equilibrium


  A state where the input and outputs of sediment in a coastal system are in a constant state of change but remain in balance
• Sediment cells


  • Not fully closed systems, so actions within one cell may affect another
• Negative feedback loop


  A mechanism that balances changes, taking the coastal system back towards dynamic equilibrium
• Positive feedback


  A mechanism that exaggerates change, taking the coastal system away from dynamic equilibrium
• Littoral zone


  The area of the coast where land is subject to wave action, constantly changing due to short-term factors like tides and storm surges, and long-term factors like changes in sea level and climate change
• Subzones of the littoral zone


  • Backshore (area above high tide level)
  • Foreshore (land where most wave processes occur)
  • Offshore (the open sea)

  
• Advancing coastline


  Coastline may be due to the land emerging or deposition being the prominent process

  
• Retreating coastline


  Coastline may be due to the land submerging or erosion becoming the prominent process

  
• Emergent or submergent coastlines


  May be due to post-glacial adjustment (the land 'wobbles' as the glacier above it melts, causing isostatic sea level change)
• Corrasion


  Sand and pebbles are picked up by the sea from an offshore sediment sink or temporal store and hurled against the cliffs at high tide, causing the cliffs to be eroded

  
• Abrasion


  Sediment is moved along the shoreline, causing it to be worn down over time