glaciated landscapes 4a CASE STUDY- ALASKA, human activity within a periglacial landscape

Human activity taking place in Alaska

• Prudhoe Bay- Northern Alaska- gone from a small Inuit settlement to a wealthy town with an economy based on oil extraction

• 1968 vast deposits of oil found in Prudhoe Bay

• Trans Alaskan pipeline (1300km) built from Prudhoe Bay to ice free port of Valdez. Pipeline runs north to south parallel to the border to Canada. Crosses 3 mountain ranges, over 600km built on stilts

• Pipeline finished in 1977, up to 1.4million barrels of oil transported per day

Reasons for human activity taking place such as resource extraction

• Alaska has huge oil fields, around 3000 million barrels

• Area 1002 is the only area in the ANWR (arctic national wildlife refuge) not protected, and it is believed to contain over 16billion barrels of oil.

• Area is key calving ground for caribou, ANWR home to indigenous people too. Concerns for environmentalists on impact of drilling on fragile tundra soils + vegetation

• Key issue- permafrost (underlies 80% of Alaska) permafrost will melt due to this pipeline- thermal energy

• Trump wanted oil and gas extraction to go ahead in ANWR in Jan 2021

• Biden halted extraction in June 2021

How have they made the pipeline more sustainable

• raised above ground- ensure heat not conducted into ground, doesn’t thaw permafrost

• Animals move below pipeline- prevent blocking caribou migration routes

• Pipeline across rivers (above), not buried in river bed

• Takes zigzag route across surface- adjust to tectonic ground movements

• Oil storage tanks raised up, built to withstand seismic movements

Impacts on processes and flows of material, energy, through periglacial system such as increased heat produced by buildings

Impact on material flows

• establishing permanent settlement, buildings and infrastructure required for oil industry required careful engineering as conventional construction methods easily alter thermal balance of the ground- thawing permafrost and ground subsidence, particularly as vegetation is cleared from surface

• Building houses elevated above surface- air can circulate, remove heat

• Larger structures and many roads, railway tracks, airstrips built on gravel pads. Early 1960s all new buildings in settlement of Dawson constructed on wooden piles or gravel pads

Gravel pads:

• get them from nearby rivers

• 1-2km thick layer of sand and gravel- acts as substitute for insulating effect of vegetation, reduces heat transfer from structures to ground, maintain thermal balance of ground, reducing thaw of permafrost, reduce subsidence

• Loss of gravel from river systems alter rate at which gravel is transported and deposited further downstream—> impact erosional and depositional processes in river system—> alters geomorphologic equilibrium.

• Hydrological processes (water cycle) impacted—> gravel extraction from glacial outwash near Palmer (Alaska) found that ground water levels fell by more than 1m in area

Impact on energy flows

• release and burning of gas during drilling

• Gases burnt in ‘flaring’- used to protect against dangers of over pressurising industrial plant equipment by burning off flammable gas released by pressure relief valves

• Releases lots of CO2 + heat into atmosphere- positive feedback loop, heat melts permafrost, permafrost releases co2

• Contribute to global warming through enhancing the greenhouse effect- further raise temperatures

Impacts on energy flows

• production of heat form extraction and transportation processes associated with infrastructure

• Barrow in Alaska- buildings produced urban heat island effect, mean temperatures 2.2 degrees higher than surrounding rural areas

• Heat from domestic heating from poorly insulated buildings- energy released by human activities affects geomorphic processes

• Barrow Alaska northernmost settlement, population grown from 300 to 4600 in a century

Effect of these impacts in changing periglacial landforms such as thawing permafrost

Thermal energy (heat) from pipeline

• Permafrost becomes thicker active layer which becomes thermokarst landscapes- waterlogged depressions, can form alases (large scale thermokarst)

• Pingos collapse- ognips

• Waterlogged soil- more solifluction lobes

Impact on landforms

• permafrost warmed up by 2 degrees since early 1980s, active layer thaws in summer and freezes in winter thickened by 90cm

• Permafrost overlain by shallow active layer- thaws in summer, freezes in winter, insulates permafrost below which is not directly exposed to seasonal air temperature differences- experiences less temperature variations

• However buildings release heat- thaw permafrost, longer melting period for active layer

• Construction takes place directly onto ground- heat, melting of active layer causes subsidence and more mobility of active layer, results in solifluction (mass movement)

• Solifluction lobes- distinctive feature may form

Methane problem:

• Large amount of carbon in permafrost

• When frozen, matter is inert but when it thaws it decays so co2 + methane released into atmosphere

• Lots of organic matter stored in permafrost like dead plants and animals

Inputs outputs and processes on periglacial system

Inputs

• increased inputs of heat around settlements and buildings

• Input of gravel to periglacial system (removed from local river systems)

Outputs

• more meltwater loss

• Carbon stores released- methane, co2

• More sediment mobilised which can be removed from system by river or coastal erosion

Processes

• more thawing, reduction in number of freeze-thaw cycles

• Increased erosion levels in coastal areas, increased thawing

• More solifluction, sediment moving through system

• Overall reduction in periglacial processes

• Reduced vegetation cover= more erosion on surface soils

Consequence of these changes on the landscape such as development of Thermokarst

Thermokarst landscape:

• permafrost thaw and degradation causes thermokarst- waterlogged depressions

• Increase in active layer depth

• Accumulation of water on soil surface

• Alases large scale steep sided depressions

• Large scale thawing of ground ice results in alases

Causes of thawing ground ice

• climate change

• Human interference in landscape system

• Ground ice thaws as insulating effects of vegetation are reduced as humans remove vegetation for resource extraction/ construction—> increase in active layer depth, greater subsidence.

• Vegetation removed- more erosion of surface soils

• Buildings or pipelines transmit heat, speeds up formation of thermokarst landscape

Impacts on landscape (buildings) of thawing ground ice

• Early settlements built in permafrost areas before special engineering designs show effect of ground subsidence

• Uneven sinking of ground adding costs to maintenance, repair of transportation infrastructure as well, as many of Alaskas highways built in permafrost areas