Alaskan tundra

• Water cycle

  -low annual precipitation most falling as snow

  -small stores of moisture in the atmosphere owing to Low temperatures which result in absolute humidity

  -limited transpiration because of low vegetation cover

  -limited groundwater and soil moisture stores, permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
• Carbon cycle in the tundra

  -the permafrost is a vast carbon sink, the accumulation of carbon is due to low temperatures which slow decomposition of dead plant material

  -the flux of carbon is concentrated in the summer months when the active layer thaws

  -during growing season tundra plants input carbon-rich litter to the soil

  -snow cover may insulate microbial organisms and allow some decomposition despite the low temperatures

  -global warming has raised concerns that Alaska is becoming a carbon source
• water cycle

  -temperatures are well below freezing for most of the year so that water is stored as ground ice in the permafrost layer

  -during short summer the shallow active layer thaws and liquid water flows on the surface

  -permeability is low because of the permafrost

  -the ancient rock surface which underlies the tundra has been reduced because of erosion and weathering
• oil and gas production and the impact on carbon and water cycles

  -The north slope of Alaska is a vast wilderness and oil and gas was discovered there

  they were presented with major challenges

  -a harsh climate

  -long periods of darkness in winter

  -permfrost

  -melting of active layer in summer

  -remoteness and poor accessibility

  the production went ahead and there was investment in pipelines, roads, oil production plant, power lines etc..
• impact of oil on the permafrost

  permafrost has been melted because

  -the construction and operation of oil and gas installations diffusing heat into the environment

  -dust deposition creating darkened snow surfaces, increasing absorption of sunlight

  -removal of vegetation cover insulates the permafrost
• impact of oil on carbon cycle

  -gas flaring and oil spillages also input co2 to the atmosphere

  -the destruction or degrading of tundra vegetation reduces photosynthesis and the uptake of co2
• impact of oil on the water cycle

  -melting of the permafrost and snow cover increases run of and river discharge making flooding more likely

  -strip mining for construction creates artificial lakes which disrupt drainage and expose permafrost to further melting

  -drainage networks are disrupted by road construction and explosions used for the oil and gas production
• management strategies to moderate the impact

  insulated ice and gravel pads

  -roads and other infrastructural features can be constructed to protect the permafrost

  buildings and pipelines elevated on piles

  -constructions buildings on piles allows cold air to circulate beneath these structures

  refrigerated supports

  -refrigerated supports are used on the trans Alaska pipeline to stabilise the temperature of the permafrost