case study of a periglacial landscape being used by people - Alaska

background to Human Activity in Alaska (resource extraction)

• 1968: Vast deposits of oil found in Prudhoe Bay on the North Slope of Alaska.

• 1968 (Post-Discovery): Prudhoe Bay transitioned from a small Inuit settlement to a wealthy town with an economy based on oil extraction.

• Pipeline Construction: The Trans-Alaska Pipeline, 1,300 km long, was built from Prudhoe Bay to the ice port of Valdez. It took 3 years to construct.

• Oil Transportation: The pipeline transports up to 1.4 million barrels of oil per day. It crosses 3 mountain ranges, 600 streams and rivers, and over 600 km is built on stilts.

• Jan 2008: Proposals were presented to the US to open the 1002 lands of the Arctic National Wildlife Refuge (ANWR) for petroleum exploration and development.

present context of to Human Activity in Alaska (resource extraction)

Present Context:

• Less conflict than the Middle East, crucial for energy security and self-sufficiency.

• Demand for oil increased after the global economic recession.

• USGS estimates 30% of the world’s undiscovered gas and 13% of oil are in the Arctic Circle.

• Proven reserves in Alaska around 3,000 million barrels.

• Area 1002 in the ANWR could contain 16 billion barrels of oil.

• Environmental concerns about the impact of drilling on fragile tundra soils and vegetation.

• The area is key for the Porcupine caribou herd's calving ground and home to Alaska’s Gwinch’in Indians and abundant wildlife.

• Permafrost, which underlies 80% of Alaska, and the implications of oil extraction for this permafrost and the subsequent impacts.

impact of human activity on processes and flows - material flows

Material Flows:

• Permanent settlements and infrastructure for the oil industry require careful engineering to avoid altering the thermal balance, which can thaw permafrost and cause ground subsidence.

• Buildings and larger structures elevated on stilts or gravel pads to reduce heat transfer.

• Roads, railway tracks, and airstrips built on gravel pads since the early 1960s.

impact of human activity on processes and flows - Palmer Gravel Extraction

• Gravel pads: Substitute for vegetation's insulating effect, reducing permafrost thaw and subsidence.

• Alteration of gravel transportation: Gravel extraction from streams/river beds changes depositional processes, affecting geomorphic equilibrium.

• Hydrological impact: Groundwater levels fell by over 1m within a 2km radius of the construction site near Palmer, Alaska.

impact of human activity on processes and flows - flaring of gas

• Burning of gas during oil drilling, known as 'flaring', releases large amounts of CO2 and methane.

• Greenhouse effect: Increased CO2 and methane levels enhance global warming, affecting permafrost which contains carbon-rich frozen plants and animals.

impact of human activity on processes and flows - Barrow Urban Heat Island

• Barrow in Alaska is a town where numerous businesses provide support services to oil field operations and the village has grown due to the oil industry

• Heat production from extraction and transportation processes.

• Barrow's growth due to the oil industry has led to an urban heat island effect, with temperatures 2.2°C higher than surrounding rural areas.

impact of human activity on processes and flows - heat released by buildings and infrastructure

• Poorly insulated buildings contribute to heat release, affecting geomorphic processes.

• Barrow's population growth from 300 (1900) to over 4600 (2000).

• Concerns: Early snowmelt due to increased temperatures could destabilize roads, buildings, and pipelines built on permafrost.

impacts on the thermokast landscape (including alases)

• Thermokarst Formation: Caused by warming and thawing permafrost in the Northern Hemisphere, leading to landscape instability.

• Factors Contributing to Thermokarst:

  • Permafrost thaw and degradation.

  • Increase in active layer depth.

  • Accumulation of water on the soil surface.

  • Retreat of the permafrost table.

• Alases:

  • Large-scale, flat-floored, steep-sided depressions (5-50m deep, 100m-15km long).

  • Formed by large-scale thawing of ground ice, leading to subsidence.

  • Can combine to form Alas valleys.

  • May contain shallow thaw lakes (less than 5m deep, 1-2km wide) formed by depressions filled with water.

impacts - changing landforms (e.g. solifluction)

•   Since the early 1980s, permafrost has warmed by up to 2^oC and the active layer that thaws in summer and freezes in winder has thickened by up to 90cm.

• However – buildings and infrastructure release heat – this can lead to thawing of permafrost and mean a longer period of melting of the active layer in the summer months.

• This is particularly the case where construction takes place directly onto the ground which means that heat and subsequent melting of the active layer causes subsidence and an increase in the mobility of the active layer – this results in solifluction (a form of mass movement).

Distinctive features such as solifluction lobes may then form.

 

causes of thawing of ground ice

Climate change and human interference reduce the insulating effects of vegetation.

1. Human activities such as resource extraction or construction increase the active layer depth, leading to greater subsidence.

2. Subsidence is significant in fine-grained sediment with high porosity due to a large volume of ground ice melting.

3. Human Impact:

   • Buildings and pipelines transmit additional heat to the ground, accelerating the formation of thermokarst landscapes beyond the natural rate.

permafrost thaw costs

uneven sinking of the ground due to permafrost thaw is adding significant costs to the maintenance and repair of transportation infrastructure as well - many of Alaska’s highways are built in permafrost areas.