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THE ARCTIC TUNDRA (Background (Climatic Conditions (For 8-9 months of the…

- - - - Ground is therefore permanently frozen with only the top metre thawing during the Arctic summer
- - - - Tundra biomass is v. small - ranges between 4 - 29 tonnes/ha depending on density of vegetation cover
  - - - Plants grow rapidly in short summer
      - During growing season, tundra plants input C-rich litter into soil
      - Activity of microorgs. increases in growing season, releasing Co2 to atmosphere thru respiration
      - Long hours of daylight allow them to flower and fruit within just a few weeks
    - - In winter, pockets of unfrozen soil and water in the permafrost act as sources of CO2 and methane
      - Snow cover may insulate microbial organisms and allow some decomposition despite the low temperatres
      - Concerns that permafrost is becoming a C source
        
        Outputs of C from permafrost have increased in recent decades; higher temps. have stimulated plant growth in the tundra and greater uptake of CO2
        
        In turn this has increased the amount of plant litter entering store
        
        So perhaps the C budget in the tundra remains in balance today despite carbon warming
  - - - Most of this C has been locked away for the past 500,000 years
    - - Low temps.
      - Unavailability of liquid water for most of the year
      - Parent rocks with few nutrients
      - So total C store of the biomass is relatively small
      - Low NPP and photosynthesis
      - Long hours of daylight in summer = short growing season
    - - Slows decomposition and respiration and the flow of CO2 to the atmosphere
    - - Exerts little influence on water + C cycles
- - - - Harsh climate - extreme cold + long hours of darkness in winter
      - Permafrost and melting of active layer in summer
      - Remoteness + poor accessibility
      - Fragile wilderness of great ecological value
    - - High global energy prices
      - US gov. policy to reduce dependence on oil imports
      - Massive fixed investments in infrastructure, power stations and gravel quarries in the early 70s and 80s
    - - High production costs on the N Slope
      - Massive growth of the oil shale industry in the USA
  - - - Permafrost
        
        Major C store in the tundra
        
        High sensitive to change sin the thermal balance
        
        Thermal balance has been disrupted in many areas by activities of oil and has companies
        
        = localised melting of permafrost
        
        Release CO2 + ch4
        
        7-40 million tonnes/ year of CO2 lost on N Slope; 24,000-114,000 tonnes of CH4
        
        Melting of permafrost is associated with:
        
        Construction adn operation of oil + gas installations, settlements and infrastructure diffusing heat directly to the environment
        
        Dust deposition along roadsifes = darkened snow surfaces = increased light absorption
        
        Removal of vegetation cover than insulates the permfrost
      - Gas flaring + oil spillages release CO2 into atmosphere
      - Industrial development
        
        Destruction/degradation of tundra vegetation reduces photosyn. + uptake of CO2 from atmosphere
        
        Thawing of soil increase microbial activity, decomposition + CO2 emissions
        
        Slow-growing nature of tundra vegetation means the regeneration adn recovery from damage takes decades
    - - Melting of permafrost + snow cover increases run-off + river discharge = flooding
      - More extensive wetlands, ponds + lakes in summer = increased evap.
      - Strip-mining of aggregates for construction = artificial lake
        
        Disrupt drainage
        
        Expose permafrost to additional melting
      - Road construction and seismic explosions for oil + gas exploration
        
        Disrupts driange entworks
      - Water abstracted from creeks + rivers for industrial use and for the building of ice roads in winter reduc elocalised runoff
  - - - Development on NB Slope had often involved deliberate destruction of permafrost
      - To minimise disruption to water + C cycles + wildlife
      - Purpose of strategies is pragmatic:
        
        Melting permafrost = widespread damage to roads + buildings + increased maintenance costs for pipelines + other infrastructure
    - - Insulated ice + gravel pads
        
        Roads + other infrastructural features can be constructed on insulating ice/gravel pads - thus protecting the permafrost from melting
      - Buildings + pipelines elevated on pads
        
        Allows cold air to circulate beneath these structures
        
        Provides insulation against heat-generating buildings, pipework etc. which would otherwise melt the permafrost
      - More powerful computers to detect oil-and-gas-bearing geological structures remotely
        
        Fewer exploration wells nedded, thus reducing environmental impact
      - Refrigerated supports
        
        Are used on the Trans-Alaska Pipeline to stabalise the temp. of the permafrost
        
        Similar supports used widely to conserve the permafrost beneath buildings + other infrastructure
- - - - Much of sun's energy is used to melt snow so that ground temperature remain low and inhibit convection
      - Surface and soil waters are frozen most of the year
    - - Permafrost is is a barrier to infiltration, percolation, recharge and groundwater flow
    - - Melting of snow and river ice, and the uppermost active layer of other permafrost in spring/summer = sharp increase in river flow
    - - This temporary store of liquid water is due to permafrost which impedes drainage
  - - - Avg. temps. are below freezing for most of the year
        
        So water is stored as ice in the permafrsot layer
        
        Prevents evapotransp. at winter
      - During summer the active layer (top metre) thaws and liquid water flows on the surface
      - Poor draiange
        
        Water cannot infiltrate the soil bc of the permafrost at depth
      - Meltwater forms millions of pools and shallow lakes
      - Some evapotransp. during summer from standing water, saturated soils and vegetation
      - Humidity is low year-round and precip. is sparse
    - - Permeability is low owing to the permafrost and crystalline rocks that dominate the tundra and sub-Arctic Canada
    - - Ancient rock surface which underlines the tundra has been reduced to a gradually undulating plan
        
        Hundreds of million of years of erosion and weathering
      - Minimal relief and chaotic deposits impede drainage = waterlogging during summer