Alaska: Human activity - periglacial landscape

• What human activity is taking place?

  • Oil extraction from the Alaskan oil fields which reserves 3 billion barrels
  • 1300 km Trans-Alaskan pipeline transports 1.4 million barrels per day from Prudhoe Bay to the ice-free port of Valdez
  • Exploration of potential oil fields in Arctic National Wildlife Refuge ( ANWR ) - potentially contains up to 16 billion barrels of which 6 billion could be extracted > creates employment opportunities
• Why is this human activity taking place?

  • 40% of UK oil consumption comes from imports
  • To ensure energy security, the USA wants to reduce this reliance on imported oil - may be a threat of political implications
  • In order to meet as much demand from domestic sources as possible, exploration of potential oil fields in Alaska has been permitted
• Barrow

  • Barrow is the largest city on the North Slope of Alaska and provides support services to oil operations
  • From 1900 to present day, its population has increased from 300 to 4600 people > increase in settlements > buildings produce the urban heat island effect > average temperature is 2.2° higher than the surrounding rural area
• How has this activity Impacted Energy flows

  1. Release and burning of gas during drilling > a process called flaring releases C02 into the atmosphere > enhanced greenhouse effect > long term global impact
  2. Urban heat island effect > heat from domestic heating systems and poorly insulated buildings increases temperatures > 2.2° higher in Barrow than the surrounding rural environment > localised melting of permafrost
• How has this activity Impacted material flows

  1. Gravel pads used as an insulating base layer for roads constructions to prevent the melting of permafrost > removal of gravel from river beds > decreases river levels by up to 2 m > alters the rate at which material is transported and deposited downstream > groundwater levels fell more than 1 m over a 2 km area from gravel extraction sites
• How has this activity changed the landforms?

  1. Melting permafrost

  Heat is released by buildings / infrastructure > leads to thawing of permafrost and longer periods of the active layer melting > causes subsidence - buildings sinking into the active layer

  2. Solifluction lobes

  Increased temperatures > increased melting of the active layer > increased mobility of the active layer > causes solifluction > downslope movement of the active layer ( up to 1 m per year ) > solifluction lobes - tongues of debris at the base of slopes when the moving material loses energy on a lower gradient
• What consequences are there for the landscape?

  Development of a Thermokarst landscapes:

  
  

  Landscape has surface depressions due to thawing of ground ice > hummocky ground ( uneven ) interspersed with water-logged hollows > depressions fill with water to form shallow thaw lakes > widespread thawing of ground ice > large scale subsidence > formation of Alases
• Consequences: Long term positive feedback loops

  • Melting permafrost > low albedo > increased insolation absorbed > increased temperatures > further increased melting of permafrost
  • Melting permafrost > release of methane and CO2 > enhanced greenhouse effect > increased temperatures > further increased melting of permafrost