Arctic Tundra case study

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  • The Arctic Tundra
    • Basics:
      • location: across northern Canada, Alaska and Siberia
      • size: 8 million Km2
    • Characteristics:
      • permafrost: the layer of topsoil that thaws during the short summer months, but beneath is completely frozen. It is hard to build upon, hence why very few people inhabit the Tundra.
      • soil: tundra soil becomes waterlogged because the active layer cannot drain downwards due to the beneath being frozen.
      • barren landscape: the tundra can be described as barren because the ground is frozen, meaning most plants are not able to grow their roots beneath the top layer of soil or receive enough nutrients to sustain their growth = plants which do exist there are small in height + sprawl across the ground
      • few plants due to the extreme environment, other than lichens which are ideal as they can withstand freezing temps + grow on rocks.
      • around 50 species in the Arctic; such as the polar bear or the arctic fox.
      • 8-9 months of the year is winter. the tundra has a negative heat balance = ground is permanently frozen. temperatures can plunge below -40.
      • summer: very short, but temperatures do rise to around 3-12 degrees. the growing season only lasts 45-90 days though
    • water cycle in the tundra:
      • low annual precipitation - around 50-350mm. most falls as snow - 10 inches/year.
      • small stores of moisture in the atmosphere due to the low temps = reduce the absolute humidity.
      • limited transpiration due to the sparseness of vegetation + short growing seasons.
      • low evaporation rates.
      • limited groundwater and soil moisture stores. the permafrost is a barrier to infiltration.
      • physical factors affecting the water cycle
        • average temps below freezing = water is stored as ice. in the summer, the shallow active layer thaws = many small and shallow lakes!
        • poor drainage: water cannot infiltrate the soil because the deep permafrost = prevents evapotranspiration.
        • low humidity all year round.
        • ancient rock surface underlies the tundra has been reduced by erosion and weathering.
    • carbon cycle
      • permafrost = vast carbon sink! 1600GT of carbon.
      • carbon accumulates due to low temp = decomposition is slow.
      • plants do grow rapidly in the summer due to long daylight hours. nonetheless, the biomass is small.
      • co2 and methane emissions accumulate in the winter due to pockets of unfrozen soil acting as a source of the greenhouse gases.
      • physical factors affecting the carbon cycle
        • carbon is mainly stored in decomposed plant remains frozen in the permafrost and locked away for half a mill years.
        • low temps, limited liquid water + rocks containing limited nutrients all limit plant growth = carbon store of the biomass is low.
        • low temps + water logging slow release of co2 to the atmosphere
    • human impacts on the carbon and water cycle in Alaska
      • oil and gas production
        • between the Brooks Range (south) and the Arctic Ocean (north), oil and gas has been discovered here in 1968 at Prudhoe Bay. = massive pipelines, roads, oil production plants, power lines were created in the 70s/80s.
          • by 1990, the north slope accounted for nearly 1/4 of the USA's domestic oil production.
        • arctic oil race
          • offshore drilling in Alaska since the 50s.
          • obama banned new oil drilling in the Arctic Ocean in november 2016.
          • Little Red Services produce oil for companies such as BP
          • indigenous people (iñupait) in the city of Barrow are under threat from their homes being destroyed.
        • impact on the carbon and water cycle
          • permafrost is highly sensitive to changes in the thermal balance.
          • melting of the permafrost is associated with construction of oil + gas installations, settlements and infrastructure diffusing heat directly to the environment
          • removal of vegetation causes melting of the permafrost.
          • melting releases co2 and methane
          • increased runoff + river discharge increasing flood risks
          • oil spill at the Exxon Valdez in 1989
    • management strategies
      • insulated ice + gravel pads
        • roads and other infrastructure can be constructed on insulating ice/gravel pads to protect the permafrost.
      • building + elevating pipelines
        • allows cold air to circulate beneath = prevents melting
      • drilling laterally
        • new techniques such as accessing it away from sites.
      • refrigerated supports
        • used on the Trans-Alaska Pipeline to stabilise the temp of the permafrost

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