Summary OCR A-level Geography ELSS Case Study - Arctic Tundra
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Course
Earth\\\'s Life Support Systems
Institution
OCR
Book
OCR A Level Geography Second Edition
Highly detailed case study of the carbon and water cycles in the Arctic Tundra, including the features of these cycles, human and physical factors that impact them, future changes and management strategies
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Summary notes OCR A Level Geography Earth's life support systems
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Features of the Water Cycle in the Artic Tundra Features of the Carbon Cycle in the Arctic Tundra
Low annual precipitation, mostly snow, 50-350mm/yr Low NPP due to short growing season
Extensive wetlands/ponds/lakes during summer = temporary stores of water (no infiltration Input of rich litter into soil & decomp. increases during growing season = increased
into permafrost) = active layer becomes waterlogged (see image)
CO2 released into atmosphere by R
Sparse vegetation & short growing season = limited transpiration
Low absolute humidity due to low temps. Rapid growth during short summer growing season as long hours of daylight &
Most of Sun’s energy used to melt snow in summer = low ground temps. & water remains thawed soil = rapid PS
frozen = low evapouration Permafrost = low temps. = low decomp. levels = carbon sink holding 1600GT carbon
Limited groundwater & permafrost = infiltration/percolation/recharge/groundwater flow 5x greater carbon in tundra soils than above ground biomass
barrier Unfrozen pockets of soil & water release CO2 & CH4 throughout winter
Accumulation of snow & ice during winter months; melting of this in summer causes sharp Snow insulates microbes = slower decomp.
increase in river flow
Physical Factors affecting Stores & Flows of Carbon Cycle
Physical Factors affecting Stores & Flows of Water Cycle
1. Temperature
1. Temperature
- Average below freezing = water stored as ground ice in permafrost layer - Low temp = lack of liquid water available for most of year
- Shallow 1m active layer thaws in summer = liquid water flows on surface - Waterlogging & low temps. slow decomp. & R = slowed flow of CO2 to atmosphere
- Meltwater forms millions of pools & shallow lakes 2. Vegetation
- Poor drainage as limited infiltration due to permafrost layer - Total carbon stored in biomass is relatively small
- No evapotran. in winter but some from standing water/saturated soils/vegetation in - Low photosynthesis and NPP
summer - Only 3 month growing season but with constant daylight
- Sparse precipitation & low humidity
3. Soil Organic Matter
2. Rock Permeability & Porosity
- Carbon mainly stored as partly decomposed plant remains frozen in permafrost
- Low permeability due to permafrost and crystalline rocks that dominate Arctic tundra
geology (+ also sub-Arctic Canada) - Remained locked away for last 500,000yrs
3. Relief 4. Mineral Composition of Rocks
Key Idea 2a: Case Study of Arctic
- Gently undulating plain of ancient rock surface underlying tundra due to millions of - Parent rocks contain few nutrients
Tundra
years of denudation - Impermeability of permafrost = rock permeability/porosity/mineral composition exert little
- Minimal relief & chaotic glacial deposits = impeded drainage + waterlogging during Fact file: influence on water/carbon cycles
summer months 5. Seasonal Changes: higher rates of flows in summer, little change in carbon storage
4. Seasonal Changes: more stores in winter, more flows in summer Severe climatic conditions: higher
latitude = more extreme over shorter periods of time
Impacts of Oil & Gas Industry on Tundra Water Cycle Negative heat balance
(8-9months/yr Impacts of Oil & Gas Industry on Tundra Carbon Cycle (mostly due to melting of
o Melting permafrost = increased run-off & river discharge = increased flood risk <-40°C in winter during 'Polar Night' permafrost)
o More extensive ponds/lakes/etc. in summer = more evapouration Permanent sunlight for around 2
o Strip mining of aggregates (sand & gravel) = artificial lakes = disrupts drainage & exposes months in summer = Polar Day o Heat diffusion from oil & gas installations, settlements & infrastructure
Extends from northern edge of o Darkening of snow surfaces along roadsides = reduced albedo effect
permafrost to further melting
boreal coniferous forest to Arctic
o Drainage networks also disrupted by road construction & prospecting seismic blasts o Removal of insulating vegetation from permafrost = reduced CO 2 uptake by PS
Ocean (southern climatic limit of the
o Abstracted water = less localised run-off Artic Tree Line = 10°C July isotherm) o North Slope: 7-40mil tonnes of CO2 & 24,000-114,000 tonnes of CH4 lost from
o Oil installations (Eg: Deadhorse) = heat transmitted directly into permafrost from 8mil km2 (Siberia, Canada, Alaska) permafrost each year
foundations = melting & methane release Low biodiversity = difficult to adapt o CO2 emissions due to gas flaring, oil spillages & increased decomp. rate
to such an extreme environment
o Regeneration & recovery will take decades/centuries as tundra veg. is slow-growing
Lower latitude = less extreme
conditions = more continuous
vegetation cover
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