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A LEVEL GEO Arctic Tundra P2 (MANAGEMENT STRATEGIES TO MODERATE IMPACTS…
A LEVEL GEO
Arctic Tundra P2
PHYSICAL FACTORS, SEASONAL CHANGES AND STORES & FLOWS OF WATER & CARBON
water cycle
influenced by temperature,
relief & rock permeability
average temperatures
well below freezing
water is stored as ground ice in the permafrost layer
[short summer] -> shallow active layer thaws and liquid water flows on the surface
meltwater forms millions of pools and shallow lakes which stud the tundra landscape
drainage is poor -> water cannot infiltrate the soil due to the permafrost at depth
[winter] -> sub-zero temperatures prevent evapotranspiration
[summer] -> some evapotranspiration occurs from standing water, saturated soils and vegetation
humidity is low all year round
precipitation is sparse
permeability
is low owing to the permafrost and the crystalline rocks
crystalline rocks -> dominate the geology of the tundra in Arctic & sub-Arctic Canada
ancient rock surface
underlies the tundra
has been reduced to a gently undulating plain by hundreds of millions of years of erosion and weathering
minimal relief & chaotic glacial deposits impede drainage & contribute to waterlogging [summer months]
carbon cycle
main storage
stored as partly decomposed plant remains frozen in permafrost
most of the carbon has been locked away for at least the past 500,000 years
low temperatures &
waterlogging
slow decomposition & respiration
slows the flow of CO2 to the atmosphere
impermeability of permafrost
rock permeability, porosity & mineral composition of rocks exert little influence on the water & carbon cycles
low temperatures &
unavailability of water
parent rocks contains few nutrients
limit plant growth
total carbon store of the biomass is relatively small
[average over the year] -> photosynthesis and NPP are low -> growing season lasting barely 3 months
some compensation for short growing season in the long hours of daylight in summer
OIL & GAS PRODUCTION
LINKING TO CARBON & WATER CYCLES
Alaska
North Slope of Alaska between the Brooks Range [south] & Arctic Ocean [north]
vast wilderness of Arctic tundra
oil and gas were first discovered at Prudhoe Bay in 1968
production went ahead by high global energy prices and the US government's policy to reduce dependence on oil imports
[1970-1980] massive fixed investments in pipelines, roads, oil production plants, gas processing facilities, power lines & generators and gravel quarries were completed
[early 1990s] North Slope accounted for nearly 1/4 of the USA's domestic oil production
[today] proportion is 6%
Alaska remains an important oil and gas province
decline in recent years -> high production costs - North Slope and massive growth of the oil shale industry - USA
the development of oil & gas
industries presented
major challenges
fragile wilderness of great ecological value
remoteness and poor accessibility
permafrost + melting of the active layer [summer]
long periods of darkness [winter]
harsh climate - extreme cold
impact on water & carbon cycles
significant impacts on the permafrost and on local water & carbon cycles
permafrost
highly sensitive to changes in the thermal balance
activities of oil & gas companies have caused localised melting of the permafrost
associated with
construction and operation = oil & gas installations, settlements & infrastructure -> diffusing heat directly to the environment
dust deposition = creating darkened snow surfaces -> increasing absorption of sunlight
removal of vegetation = insulates the permafrost
melting releases
releases CO2 and methane CH4
CO2 losses vary from 7 -> 40 million tonnes /year
CH4 losses vary from 24,000 -> 114,000 tonnes /year
gas flaring and oil spillages input CO2 to the atmosphere
destruction & degrading of tundra vegetation = reduces photosynthesis, uptake of CO2
thawing of soil = increases microbial activity, decomposition & emissions of CO2
slow growing nature of tundra vegetation -> regeneration & recovery from damage takes decades
water cycle
melting = increases run-off and river discharge -> higher risk of flooding
[summer] wetlands, ponds & lakes become more extensive -> increasing evaporation
strip mining of aggregates (sand & gravel) for construction -> creates artificial lakes -> disrupt drainage, expose the permafrost to further melting
road construction & seismic explosions = used to prospect for oil & gas -> disrupt drainage networks
water abstracted from creeks & rivers = industrial use / building of ice roads -> reduce localised run-off
MANAGEMENT STRATEGIES TO MODERATE IMPACTS ON WATER & CARBON CYCLES
development of the North Slope has often involved the deliberate destruction of the permafrost
minimising disruption to the
water & carbon cycles
the strategies are pragmatic
melting permafrost = widespread damage to buildings and roads, increased maintenance costs for pipelines & other infrastructure
strategies
insulated ice & gravel pads
= roads & other infrastructural features can be constructed
-> insulating ice / gravel pads
-> protecting the permafrost from melting
buildings & pipelines elevated on piles
= constructing buildings, oil/gas pipelines & other infrastructure on piles
-> allows cold air to circulate beneath these structures
-> provides insulation against heat-generating buildings, pipelines etc.
-> which would otherwise melt the permafrost
drilling laterally beyond drilling platforms
= new drilling techniques allow oil & gas to be accessed several km from the drilling site
-> fewer sites needed for drilling rigs
-> impact on vegetation & the permafrost due to construction is reduced
-> construction = access roads, pipelines, production facilities etc.
more powerful computers can detect oil- & gas- bearing geological structures remotely
= fewer exploration wells are needed
-> reduces the impact on the environment
refrigerated supports
= used on the Trans-Alaska Pipeline
-> stabilises the temperature of the permafrost
-> similar supports are widely used to conserve the permafrost beneath buildings & other infrastructure