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ARCTIC TUNDRA (Background (Permafrost (Traps methane (Methane is product…

- - - - Methane is product of anaerobic decay of plants in peat
- - - - Clouds only reflect light when sun is scarce
  - - - Records of increasing temps.
      - Melting glaciers
      - Reductions in extent + thickness of sea ice
      - Thawing permafrost
      - Winter temps. rising more rapidly than in summer
      - Regional variations due to atmospheric wind + currents
- - - - The active layer - thaws in summer and refreezes in winter
      - Subsurface - newly thawed C becomes available for decomposition
    - - Plant inputs
      - Soil environment
      - Soil depth
      - Water saturation
    - - Top-down thawing of permafrost (increasing the thickness of active layer)
      - Lake draining
      - Erosion
      - Leaching from upland soils into aquatic systems/sediments
    - - Ground surface subsides, attracting local water
  - - - Low BD
      - Small veg. store
  - - - Will release huge amounts of CO2 stored as methane hydrates
      - Increases global warming as methane is 20-30 times more potent that CO2
      - Positive Feedback
    - - Will be stimulated by increase in CO2 + warming temps.
      - Means Arctic will be a C sink
      - Much plant growth needed to counter-act the methane released from permafrost melting
- - - - Less deep at poles
      - Warm atmopshere holds more moisture
      - Water vapour is v effective greenhouse gass
    - - V. cold so more CO2 dissolves into it in Arctic regions
      - Arctic ocean is 3% of E's oceans but removes 10% of E's carbon uptake
      - As oceans warm, they are less able to dissolve CO2 from the atmosphere
    - - Boreal forests store C as plant mat. in the low arctic
    - - Arctic tundra stores C as soil C in nothern permafrost areas
      - The C is stored in the permafrost as dead organic matter
      - Permafrost melts = more CO2 released
- - - - Winter: No evap.; ground ice in permafrost = poor drainage
      - Summer: Some evap. from standing water; shallow active alyer melts = runoff + wetlands
    - - Minimal relief + glacial deposits impede drainage = waterlogging in summer
    - - Limited - low temps, lack of freshwater, few nutrients
      - Small total C store of biomass due to limited veg.
    - - Where most C is stored for past 5,000 years
      - Low temps. + water logging = decreased decomposition rates
    - - Permafrost = low permeability
      - Permeability + porosity has little effect on water + C cycles coz of permafrost
  - - - Moves living biomass in oceans to land - affects local C cycle
      - Transport of fish relies on air freight + shipping - fossil fuels
    - - Warmer Arctic = increased fire risk
      - May 2016, Canada
        
        Drought + tar sands under soil = uncontrollable fire; 88,000 evacuated
      - Fires release C suddenly in fast cycle
    - - These extractions move C from slow to fast cycle as they are burnt as in combustion engines + power stations
    - - Tourism in White Mts. of Alaska affects soil store of C
      - ATVs driver over permafrost = melting + release methane
      - Pressure from vehicle tyres moves water from its store in peaty wastes to lakes.runoff into oceans