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The Arctic Tundra Case Study (Climate (Winter temperatures are very cold -…
The Arctic Tundra
Case Study
Climate
Negative heat balance for most of year
Less heat coming in than out
Winter temperatures are very cold - low as -40C
slows process of decompostition
prevents growth of many plants and limits animals able to inhabit the area
5x more carbon stored in soil than above ground biomass
Clear seasonal changes, unlike TRF
Very long daylight hours in Summer
High photosynthesis levels from plants
lots of carbon taken in
increased evaporation
more interception, initial increase in run-off due to snowmelt
In winter most water remains locked up in ice stores
Precipitation in Sept-Oct
increased summer evaporation is released in autumn
low annual precipitation, 50-350 mm per year
Permafrost acts as large carbon store
1600 GT of carbon
Very low NPP due to short growing season, almost permanent dark in winter, which prevents photosynthesis, as well as freezing temperatures
Human Impacts
Oil
discovered in Prudhoe Bay in 1968
Fixed investments made in 1970s/80s: pipelines, roads, gas processing facilities, power lines and generators
By early 1990s North Slope accounted for nearly 1/4 of all US domestic oil production
Trans- Alaskan Pipeline = 1,300km long and is used to transport oil at temperatures of 65-85C, which melts the ice
Management Strategies
Insulated ice and gravel pads
Insulate the permafrost in the summer
Refrigerated supports
oil pipes surrounded by refrigerated brine to prevent heat transfer to the environment and consequent melting of permafrost
More powerful computers detect oil and gas bearing geological structures remotely
reduces need for exploration wells
Drilling laterally beyond drilling platforms
reduces no. of drilling sites required
Buildings and pipelines elevated on poles
allow cold air to circulate beneath, protecting permafrost
Physical Impacts
Temperature
Humidity is low all year
Sparse precipitation
In winter, temperatures prevent evapotranspiration and in summer, some occurs form standing water, saturated soils and vegetation
Rock Permeability and Porosity
Permeability is low due to permafrost and crystalline rocks
This low permeability means that rock permeability, porosity and mineral composition has little effect on the cycles
Relief and Drainage
Minimal relief due to erosion and weathering and chaotic glacial deposits obstruct drainage and contribute to waterlogging in Summer
Drainage is poor as water can't infiltrate soil because of permafrost
During short summer, meltwater forms millions of pools and shallow lakes as the active layer thaws and liquid water flows on surface
Vegetation and Organic Matter in Soil
Waterlogging and low temperatures slow decomposition, respiration and the flow of CO2 to atmosphere
Carbon is mainly stored as decomposed plant remains in the permafrost, locked away for over 500,000 years
Relatively small biomass carbon store due to lack of water and nutrients, NPP and photosynthesis are low on average
Permafrost is a major carbon
store and is highly sensitive to thermal balance
This balance is disrupted by oil and gas companies
construction and operation diffuses heat directly to the environment
dust deposition darkens snow to increase sunlight absorption
albedo - positive feedback
removal of vegetation cover which acts as insulation to permafrost
This melting leads to 7-40 million tonnes of C02/carbon storage lost per year
Destruction of vegetation
Destruction and degradation of vegetation reduces photosynthesis and uptake of CO2 from atmosphere
Tundra vegetation takes decades to recover due to its slow growing nature
Gas flaring and spillages also release CO2