4.2 - CASE STUDY: Artic Tundra

Tree Line

The northernmost latitude in the Northern Hemisphere where trees can grow; farther north, it is too cold all year round to sustain trees.

Permafrost

Ground that is permanently frozen. Because the permafrost has no cracks or pores, nothing can penetrate it--neither plant roots nor water. (below 0^oc for 2 or more consecutive years).

Active Layer

The top layer of soil in the tundra that thaws during the summer months, allowing for some plant growth and biological activity. thaws each summer. The more northerly the location, the thinner the active layer is.

Location

Tundra is found in the regions just below the ice caps of the Arctic, extending across North America, to Europe, and Siberia in Asia. Much of Alaska and about half of Canada are in the tundra biome.

Climate

Temperatures are frequently extremely cold but can get warm in the summers. Tundra winters are long, dark, and cold, with mean temperatures below 0°C for six to 10 months of the year.

Why is it so cold in the Artic Tundra

At the Arctic Circle, solar energy strikes the ground at a low angle and is spread over a large area. Each square metre within this solar footprint is heated only gently

Why does it receive limited sunlight

Arctic tundra receives a limited amount of sunlight due to the position of the Sun in the sky.  Due to the high latitudes the Sun can remain below the horizon for up to 2 months, leaving the Arctic tundra in darkness. Even in summer when the sun remains in the sky 24 hours a day, it stays close to the horizon and provides only low intensity sunlight.

Why is it so dry

At the poles, air is cooled and sinks towards the ground forming high pressure, this known as the Polar high. Cool air sinks. As it sinks the molecules move closer together which means more mass and so more pressure. As the air sinks, it warms, condensation is rare and so few clouds and little rain. Little precipitation means it’s dry.

Temperature

An area where the temperatures are incredibly low, this is largely due to the fact that is has a negative heat balance for 8-9 months a year (more heat energy lost to atmosphere than gained from solar radiation). As a result, the temperatures are extremely low, mean temperatures -15^oC (up to -40^oC in deepest winter).

Precipitation

Most of the year (8-9 months) will be below freezing >0^oc. There will be very low annual precipitation between 50-350mm a year on average (10% of what you would get in the Amazon per year) most of which will fall as snow (<100mm in most areas)

Summer

In the summer, temperatures rise above freezing and long hours of daylight which means short growing season for plants. Vegetation has adapted to survive (low lying trees, small leaves, very few trees) so they don’t give of lots of water via transpiration and don’t require water via precipitation (as it is very sparse). In the high artic, conditions are most severe with little vegetation and lots of bare ground.

Climate Change

Climate change due to the enhanced greenhouse effect is leading to high temperatures. Because of these higher temperatures there is potential that more of the artic will become green as growth of more vegetation in Artic areas (e.g. Northern Quebec). 

Humidity

Low temperatures = limited moisture stored in the atmosphere & low absolute humidity (cold air can’t hold water)

Transpiration

Limited transpiration due to limited vegetation

Infiltration

Permafrost is barrier to infiltration and percolation of water. Storage of water in underground stores (i.e. aquifers) and via soil moisture is very limited.

what thaws

Only section that thaws (melts) is the very top later of soil called the active layer in spring/ early summer. 50-60 days a year the active layer thaws and vegetation can grow.

Winter change

temperature < 0^oc. Water is stored as ground ice in permafrost/ snow on surface. No evaporation, very small amount of sublimation. River’s freeze. Sub-zero temperatures prevent evapotranspiration.

summer change

 temperature > 0^oc. Liquid water on the surface (melted active layer). Some evapotranspiration from standing water, saturated soils and vegetation. Infiltration only in the summer because ice is impermeable so no percolation occurs. Rivers will be at peak/ most channel storage in summer.

When temperatures rise in summer -> Snow on surface and ‘active layer’ thaw -> Temporary ponds and lakes appear -> Don’t infiltrate due to permafrost layer.

Low humidity and sparse precipitation because cold air can’t hold as much water.

Geology

Much of Artic Tundra is made from Precambrian Igneous Rock. Very impermeable. Permeability is therefore low so leads to standing pools of water in warmer summer periods (prevents water going down or percolating to any aquifers.

 But often the type of rock doesn’t have an impact because the permafrost is impermeable so water can’t even reach the rock.

Canadian Shield

geology eg. the ‘Canadian Shield’ (igneous) shows how much of Canadian Tundra is similar geology. Uniform geology.

Relief

Much of the Tundra is typically flat, with gentle slopes. Uniform relief. Some areas with gentle slopes. The extensive low relief (along with the permafrost layer) means that there is very little infiltration.

Winter Relief

snow stays on surface

Summer Relief

Flat relief means pools of water appear on surface, rather than drain away.

NPP of the Artic Tundra

200 g/m²/Yr

Comparison of Artic V Amazon: NPP

Amazon-    NPP 2500 grams m²/year

Artic -   NPP less than 200 grams m²/year

Artic V Amazon: Carbon stored in Biomass

Amazon - between 400 and 700 tonnes/ha

Artic - less than 30 tonnes/ha

Artic V Amazon: carbon stored above ground

Amazon: 60%

Artic: 5x underground than above ground

Artic V Amazon: Gigagtonnes of Carbon

Amazon: 150-200

Artic: 1600 in permafrost

Why so much carbon in the permafrost

1600 GT of carbon is stored in the Permafrost. It is so large because decomposition is so limited and there is very little carbon being released.

Why is the biomass carbon store so low

conditions are poor for plant growth – low temperatures, low sunlight in winter, lack of liquid water. NPP is under 200 m²/Yr 

Permafrost feedback loop

1.     Increase in greenhouse gases = global temperature increases.

2.     Increase temperature causes permafrost to thaw.

3.     Frozen organic matter thaws and starts to decay.

4.     Decomposition of organic matter release CO² and Methane (pockets of methane get stuck)

5.     More CO² & Methane released into atmosphere store.

Impact on water and Carbon cycle: Trans-Alaska Pipeline

·       Loss of vegetation

·       Permafrost damaged during construction

·       Heat from oil melts ice and snow

·       Roads and machinery melt permafrost and disrupt albedo as the roads are dark ground

Impact on carbon and water cycle: Prudhoe Bay

·       Loss of vegetation

·       Permafrost damaged during construction

·       Heat from machinery

·       Roads, buildings and machinery melt permafrost and disrupt albedo

·       Drainage disrupted.  More flooding

·       Water pollution, oil spills

Impact on Carbon and water cycles: Gravel Pits near Fairbanks, Alaska

·       Loss of vegetation

·       Permafrost damaged during mining

·       Heat from machinery

·       Roads, buildings and machinery melt permafrost (15M) and disrupt albedo

·       Artificial lakes cause thawing and disrupt albedo

Stategies

insulated ice and gravel pads

buildings and pipelines elevated on piles

drilling laterally beyond drilling platforms

More powerful computers can detect oil- and gas bearing geological structures remotely

refrigerated supports

Insulated ice and gravel pads

Roads and other infrastructural features can be constructed on insulating ice or gravel pads, thus protecting the permafrost from melting. The Spine Road at Prudhoe Bay lies on a 2m deep pad.

Buildings and pipelines elevated on piles

Constructing buildings, oil/gas pipelines and other infrastructure on piles allows cold air to circulate beneath these structures. This provides insulation against heat-generating buildings, pipework, etc. which would otherwise melt the permafrost.

Drilling laterally beyond drilling platforms

New drilling techniques allow oil and gas to be accessed several kilometres from the drilling site. Shell has developed the 'snake drill', which allows directional drilling across a wide area from a single drilling site. With fewer sites needed for drilling rigs, the impact on vegetation and the permafrost due to construction (access roads, pipelines, production facilities, etc.) is greatly reduced.

More powerful computers can detect oil- and gas bearing geological structures remotely

Fewer exploration wells are needed thus reducing the impact on the environment. About 10% of all 'supercomputers' have been delivered to the oil industry. Its two big computational tasks are seismic data processing (to deduce underground geological structures), and reservoir modelling (to simulate the flows within a producing field, in order to optimise the amount of oil that can be recovered).

Refrigerated Supports

Refrigerated supports are used on the Trans-Alaska Pipeline to stabilise the temperature of the permafrost. Similar supports are widely used to conserve the permafrost beneath buildings and other infrastructure.

Trans-Alaska Pipe Line travel

Prudhoe Bay to Valdez (ice-free port)

Trans-Alaska Pipeline when and why

It was built from 1974 to 1977 after the oil crisis in 1973 caused a sharp rise in oil prices. Ultimately the government realised they needed to take action during this crisis so they decided to go ahead and construct the pipeline in order to resolve the crisis; now riches oil field in USA.

Trans-Alaska Pipeline how big

-       It is 800 miles long and 48 inches in diameter with a 12 million barrel daily capacity. 35,000 gallons of oil can flow every minute.

Trans-Alaska Pipeline how much and how long

-       It took $8 billion; 20,000 workers; 12-hour days; 7-day weeks to finish in 3 years.

Trans-Alaska Pipeline process

First, they built the road, 360 miles long, supplying 30 construction camps, using extra gravel to insulate the permafrost. Then the pipe, 70,000 sections joined and laid, then buried or raised crossing three mountain ranges, 800 riverbeds, tundra, forests and lakes.

Trans-Alaska Pipeline - pumping stations

The pipeline has 11 pumping stations and has shipped almost 16 billion barrels of oil.

Trans-Alaska Pipeline - below and above ground

Approximately 600km of the pipeline is buried while about 675km is above ground to avoid burning the pipe in permafrost. The pipeline buried is either insulated or refrigerated to keep permafrost from thawing.

Trans-Alaska Pipeline - refrigerated points

There are refrigeration points throughout the pipeline that circulate chilled brine to maintain the soil in a stable frozen condition.

Trans-Alaska Pipeline - VSMs

The above ground proportions of the pipeline sit on vertical support systems also known as VSMs. The pipeline has 78,000 VSMs 60 feet apart that are equipped with heat transfer pipes and radiators that keep the permafrost beneath the supports frozen.

Pipeline design

  It’s a new design for constructing so caribou can march under it also allows the pipeline to move a certain amount both vertically and horizontally in case of an earthquake.

Pipeline configuration

The pipeline is configured in a zigzag formation to allow for expansion and contraction due to temperature.

Pipeline cost now v then

Today the pipeline would cost about $31 billion to build, whereas in 1977 it cost only $8 billion. That’s an inflation rate of 292.50%.

Trans-Alaska pipeline - pros

it can transport large amounts of oil in a small amount of time and it creates more places to drill from while lowering oil costs.

Trans-Alaska Pipeline - cons

there are several native species in Alaska that have the potential to suffer. It can also affect plant life as well as landscapes like rivers and streams due to pollution.

Trans-Alaska Pipeline - help families

The pipeline lowered the cost of oil and created many construction jobs in the United States – this helped many families with financial problems.

Trans-Alaska Pipeline - deaths

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Impacts of the Oil and Gas Industry on the Water Cycle

-       Melting of permafrost and snow cover = increasing runoff and river discharge.

-       More extensive wetlands and lakes = more evaporation.

-       Artificial lakes from gravel pits = more permafrost melting.

-       Building ice roads and industry increases water abstraction = reduced river flow.

-       Artificial lakes near Fairbanks have seen 15m of permafrost to melt in the last 60 years.

Impacts of the Oil and Gas Industry on the Carbon Cycle

-       Reduction in vegetation – decades to recover & reduce photosynthesis  less CO² absorbed

-       Impact of Albedo effect

-       Melting permafrost – release of CO² and CH⁴.

-       Increasing decomposition as active layer thaws.

-       North Slope CO² emissions are estimated to have increased by 73% since 1975.