4.a. human activity causes change within periglacial landscape systems (Case study)

What is the case study for a periglacial landscape being used by people

Alaska

Describe Prudhoe Bay

It used to be a small inuit settlement but is now a town with an economy based on oil extraction

Describe the Trans-Alaskan pipeline

It is 1300km long, running from Prudhoe Bay to Valdez
Transports up to 1.4 million barrels of oil each day
Over 600km is built on stilts to prevent permafrost from melting
Finished in 1977

What human activity is taking place in Alaska

Gravel extraction, oil extraction, and mining

What are the reasons behind the resource extraction in Alaska

In 1968, vast deposits of oil were found in Prudhoe Bay, leading to the Trans-Alaskan pipeline being built
Additionally, the USA wants to become self-sufficient and not rely on importing from other countries, hence why there is pressure to drill in Alaska
Due to conflict in Russia and the middle east, the US prefers to harness their own oil and sell it rather than importing it

How much gas is in Alaska/Arctic circle

The USGS estimated 30% of the world's undiscovered gas is waiting to be found in the Arctic circle
It is believed that Area 1002 in Alaska could contain over 16 billion barrels of oil

Name three landscape impacts of the Trans-Alaskan pipeline

Solifluction, organic matter, plant growth

Explain the impacts of the Trans-Alaskan pipeline (solifluction)

Buildings and infrastructure release heat, leading to thawing of permafrost and a longer period of melting for the active layer
When construction takes place directly onto the ground, heat and the melting of the active layer causes subsidence
This means there is an increase in the mobility of the active layer, causing solifluction
Solifluction lobes may then form

Explain the impacts of the Trans-Alaskan pipeline (organic matter)

Organic matter frozen in the permafrost is a major source of methane in the Arctic
It consists of dead plants and animals frozen deep within the permafrost, containing large amounts of carbon
As permafrost thaws, the organic matter decays, releasing CO2 and methane into the atmosphere

Explain the impacts of the Trans-Alaskan pipeline (plant growth)

When permafrost melts, there is more water available so plants grow rapidly.
However, thawing removes the impermeable barrier provided by frozen ground. This increases drainage.
This leads to drier soils over time, reducing vegetation growth
This impacts animal habitats and food supply, disrupting local ecosystems.

What is area 1002

An area of 6070 km2 in the northwest part of the Arctic
It is not protected by wilderness designation
Could hold large petroleum deposits
It is the core calving ground for the Porcupine caribou
It is inside the ANWR

US government plans with area 1002

In Jan 2021, Trump approved plans for oil and gas extraction in the ANWR
In June 20221, Biden halted this extraction

How were problems associated with building the Trans-Alaskan pipeline solved?

Pipeline was raised above the ground and supported by refrigerants to ensure heat is not conducted into the ground, also allowing animals to move below it (prevents migration routes from being blocked)
Pipeline takes a zigzag route across the surface to be able to adjust to ground movements

What are the effects of permafrost thawing

Large scale thawing of permafrost leads to waterlogged soil (thermokarst)
This forms alases
Pingos collapse and become ognips
There will be more solifluction and more solifluction lobes will form

How has construction reduced the risk of permafrost melting

Careful engineering has been done to avoid altering the thermal balance of the ground, which would result in thawing of permafrost and ground subsidence
Homes and buildings are built above the surface to allow air to circulate and to remove heat
Large structures and roads are built on gravel bads

What are gravel pads

A 1-2 metre thick layer of sand and gravel that acts as a substitute for the insulating effect of vegetation

What is the aim of gravel pads

The aim is to maintain thermal balance of the ground in it snatural state, to reduce permafrost thaw

What to gravel pads do

They are a substitute for the insulating effect of vegetation and they reduce transfer of heat from the structure to the ground

Drawbacks of gravel pads

The loss of gravel from river systems (to be used in the pads) alters the rate at which gravel is transported and deposited further downstream. This can impact erosional and depositional processes in the river system, thus affecting the river's equilibrium.
Hydrological processes are also impacted - gravel extraction from a glacial outwash aquifer near Palmer, Alaska, found that groundwater levels fell by more than 1m in an area near the construction site

What flow do gravel pads impact?

Material flows

What is gas flaring and what is its purpose

During oil drilling, the release and burning of gases occurs
Some gases are burnt by 'flaring', which is used to protect against the dangers of over-pressurising industrial plant equipment

Effects of gas flaring

It releases large amounts of CO2 and often methane too
These higher levels of carbon dioxide and methane contribute to global warming through enhancing the greenhouse effect, further raising temps
This can lead to a positive feedback mechanism

What flow does gas flaring impact?

Energy flows

Describe Barrow

Barrow is the northernmost settlement in the USA
It is underlain by permafrost
The buildings have produced an urban heat island effect

Describe urban heat island effect

In barrow, temps are 2.2 deg higher than in rural areas
The urban heat island effect is generally caused by concrete/asphalt that absorbs heat, reduced vegetation, and vehicles producing heat

What contributes to Barrow's urban heat island effect

Heat from domestic heating and poorly insulated buildings contributes to the urban heat island effect

What causes thermokarst to form

Permafrost thaw
Increase in depth of the active layer
Accumulation of water on soil surface
Retreat of permafrost table

What is thermokarst

A typical thermokarst landscape is dominated by extensive areas of hummocky ground with surface depressions which may be water-logged

What are alases

Large scale, flat floored, steep sided depressions

How do alases form

Large scale thawing of ground ice results in large-scale subsidence

How does human interference change the landscape

Ground ice may thaw because the insulating effects of vegetation are reduced when humans remove vegetation for resource extraction or construction
This leads to active layer depth increasing + more subsidence
Deepening the active layer causes a large volume of ground ice to melt, relative to original frozen volume of ice

Human impacts of permafrost thaw

Sinking of the ground due to permafrost thaw is adding significant costs to the maintenance and repair of transportation infrastructure as many of Alaska's highways are built in permafrost areas

Inputs to periglacial system

Increased inputs of heat due to urban heat island effect
Additional input of gravel to periglacial system as it is removed from local river systems

Processes in periglacial system

Increased thawing
Reduction in the number of freeze-thaw cycles
Increased levels of erosion in coastal areas
Greater rates of solifluction
Overall reduction in periglacial processes
Falling water table
Reduced vegetative cover and therefore more erosion of surface soils

Outputs in periglacial system

Greater levels of meltwater lost
Carbon stored released as methane and carbon dioxide
More sediment mobilised

Impact of human activities on drainage patterns

permafrost restricts water drainage, keeping the soil moist during the short summer growing season
Road construction and break the permafrost layer, changing water drainage patterns and moisture retention.

Impact of human activities on vegetation and the ecosystem

The boreal forest will advance northward into present coastal plain tundra, altering plant communities and use by wildlife.
Once destroyed, the permafrost takes years to resume. The water is used up and drains away without the restrictive layer. After a few months, water becomes deficient, and no plants can grow well even in summer.