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Title: A Level geography notes - Arctic tundra, earth's life support systems - OCR B
Description: This 5 page document details everything AS/A Level OCR B geography students would need to know about the water and carbon cycles in the Arctic tundra. Includes case study info and facts, physical and human factors impacting both cycles, management strategies and oil and gas drilling in Alaska.

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CASE STUDY: the Arctic Tundra (the water and carbon cycles in the
Arctic tundra and the physical and human factors that affect them)
Introduction
● The Arctic Tundra occupies 8 million square kilometers in northern Canada,
Alaska and Siberia and it extends from the northern edge of the boreal
coniferous forest to the Arctic Ocean
...
It is classed as a desert
...

● For 8-9 months of the year, the tundra has a negative heat balance, meaning
that there is more outgoing solar radiation than incoming
...
At this time,
average monthly temperatures are below freezing so the ground is permafrost
with only the top metre thawing during the Arctic summer
...

● In winter temperatures can plunge below -40 degrees celsius because the sun
remains below the horizon for several weeks
...
Mean annual precipitation is low
...

The High Arctic is barren but in the Low Arctic (southern areas) vegetation
provides continuous ground cover because conditions are less extreme
...

➔ Small stores of atmospheric moisture (due to low temperatures and
therefore low humidity)
...

➔ Low rates of evaporation (this is because most of the Sun’s energy in
summer is used to melt snow so that ground temperatures remain low
...

➔ Limited groundwater and soil moisture stores (permafrost is a barrier to
infiltration, percolation, recharge and groundwater flow)
...

When some of this melts in spring and early summer, there is a sharp
increase in river flow
...

Carbon cycle in the tundra

● The permafrost is a vast carbon sink, globally containing about 1600 GT of
carbon
...
g
...

● This accumulation of carbon is due to low temperatures which slow
decomposition
...
During the short summer, plants grow rapidly
and long daylight hours allow them to flower and fruit within just a few weeks
...
Therefore the
tundra biomass is small, ranging between 4 and 29 tonnes/ha, depending on
the density of vegetation cover
...
However
carbon dioxide and methane emissions also occur in winter as pockets of
unfrozen soil and water release them
...

● Permafrost used to be considered a carbon sink but due to global warming
has become a carbon source
...
This is because
whilst carbon outputs from the tundra have recently increased, the higher
temperatures have caused more plants to grow (which absorb more carbon
dioxide and eventually decompose)
...

Physical factors, seasonal changes and stores and flows of water
Flows and stores of water in the tundra are influenced by temperature, relief and
rock permeability:
● Average temperatures are below freezing mostly so water is stored as ground
ice in the permafrost layer
...

Drainage is poor because water cannot infiltrate the soil
...

Humidity is low all year round, as is precipitation
...
These rocks
are dominant in the geology of the tundra in the Arctic and sub-Arctic Canada
...
This
minimal relief and chaotic glacial deposits impede drainage and contribute to
waterlogging in the summer months
...
Most of this carbon has been locked away for at least the
past 500,000 years
...
Thus, the total carbon store of the biomass is
small and photosynthesis and NPP are low (because the growing season
barely lasts for 3 months)
...

● Due to the impermeability of the permafrost, rock permeability, porosity and
the mineral composition of rocks exert little influence on the water and carbon
cycles
...

● Oil and gas were discovered there at Prudhoe Bay, Deadhorse in 1968 and
the Dalton Highway was built to facilitate extraction
...

● Despite these challenges, high global energy prices and the US government's
policy to reduce dependency on oil imports forced production ahead
...
By the early 1990s, the North Slope
accounted for nearly a quarter of the USA’s domestic oil production (although
today it is 6%)
...

● Donald Trump is now planning to auction off leases which would allow people
to drill oil/gas in the Arctic National Wildlife Refuge (ANWR)
...
6mil
acre area which has been protected since 1980
...

● Permafrost (land which has been frozen under 0 degrees celsius for 2 or more
consecutive years) is highly sensitive to changes in the thermal balance,
which has been disrupted by oil/gas production
...

➔ Removal of vegetation cover which insulates the permafrost
...
Because the tundra vegetation is so slow
to grow, recovery from this damage could take decades
...

● Permafrost melting releases carbon dioxide and methane (which is 25x
stronger than C02) and on the North Slope, estimated CO2 losses from the
permafrost vary from 7 to 40 million tonnes/year (potential evaluation point…)
...

● The thawing of soil increases decomposer microorganism activity therefore
increasing rates of decomposition so more carbon is released into the
atmosphere
...
Tundra can be a carbon sink AND a carbon source
...
This is bad because ¼
of all land in the northern hemisphere is permafrost and ⅓ of Canada’s land
mass is permafrost
...

Impacts on the water cycle
● Melting of permafrost and snow increase surface run-off and river discharge
making flooding more likely
...
This shows a change in the stores and flows of water - more
water in the atmospheric store/hydrosphere and less found in the cryosphere
...

However, the vault got flooded in 2017
...

● Strip mining of aggregates (sand and gravel) for construction also creates
artificial lakes which disrupt drainage and expose the permafrost to further
melting
...
HOWEVER, it

could be argued that the permafrost is impermeable anyway so drainage was
already poor
...
This makes darker snow surfaces which have a lower
albedo and therefore absorb more sunlight
...

● In Northern Canada a phenomenon called river piracy has occurred
...
Therefore the meltwater from the glacier lowered the
elevation of the river, causing it to disappear
...

● Villages in Siberia also recorded temperatures of 38 degrees celsius for the
first time ever in June 2020
...

➔ Insulated ice and gravel pads
...

➔ Buildings and pipelines elevated on piles
...
This stops the permafrost from melting due to
heat-generating buildings
...
New drilling techniques
mean that oil and gas can be accessed several kilometers from the
drilling site
...

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

➔ Refrigerated supports
...

They also allow caribou to migrate underneath the pipeline, therefore
reducing the environmental impacts on fauna
Title: A Level geography notes - Arctic tundra, earth's life support systems - OCR B
Description: This 5 page document details everything AS/A Level OCR B geography students would need to know about the water and carbon cycles in the Arctic tundra. Includes case study info and facts, physical and human factors impacting both cycles, management strategies and oil and gas drilling in Alaska.