2.2.b Arctic Tundra

• 8 million km squared in Northern Canada, Russia and Alaska
• The climate becomes more sever the higher the latitude
• Negative heat balance for 8/9 months a year
• Ground is permanantly frozen, only the top metre thaws in the summer
• Permafrost underlies the majority of the Arctic
• Temperatures plumet to under -40 degrees Celcius
• For parts of the year the Arctic is in complete darkness for the whole day as the sunrise is below the horizon

• Low annual prcipitation at under 350mm with most falling as snow
• Small store of moisture in the atmosphere
• Limited transpiration due to limited vegetation and short growing season
• Cold temperature limits evaporation
• Permafrost barrier prevents percolation and infiltration so there is a limited groundwater store
• The active layer consisting of rivers, lakes and snow during the winter melts during the summer causing a peak in river flow
• Temporary wetlands during the summer cannot be drained due to this reason

• Permafrost is a vast carbon sink with 1600GT of carbon globally
• Cold temperatures slow deposition storing the carbon in the permafrost
• The largest fluxes of carbon happen in the summer when the active layer melts
• Plants grow rapidly in the summer due to long hours of sunlight
• Tundra biomass is low at 200g per metre sqyared per year
• Tundra used to be a carbon sink
• In recent times it has become a carbon source
• This is due to global warming increasing methane being released and more decomposition

Temperature

• Well below freezing for most of the year
• Water is stored in the permafrost
• Active layer thaws in the summer creating surface water
• Low humidity all year round
• Sparse precipitation

Permeability

• Meltwater creates small pools of water
• Poor drainage due to no percolation or permeability of the permafrost
• Crystalline rocks determine the geology of the tundra which isn't permeable

Relief

• Minimal relief
• Causes chaotic glacial deposits
• Waterlogging in summer months

• Most carbon is locked in the permafrost as dead organisms for over 500,000 years
• Low temperatures and limited water availability limits plant growth
• Total carbon store in biomass is low
• Low temperatures and waterlogging prevents decomposition slowing the rate of carbon being released into the atmosphere

Prudhoe Bay

• Oil and gas was discovred here in 1968
• The harsh climate posed problems for the extraction due to the cold and long hours of darkness along with the melting of the active layer in the summer causing flooding
• Drilling was needed due to the rising demand for oil and gas and the US wanted to be less dependant on other countries for their oil and gas
• they made pipelines, roads, oil producion plants, power lines and gravel quarries in the 70s and 80s
• By the 90s, the North Slope accounted for 25% of the USA's oil however it s now just 6% due to the high prices of extraction in Alaska

• Localised melting of the permafrost due to
  • Construction and operation of installations diffusing hesat into the environment
  • Dust deposition causing the albedo affect
  • Removal of vegetation cover which insulates the permafrost
• Increased run-off
• Decreased lag-time
• Increased risk of flooding
• More extensive wetlands in the summer

• Balance of carbon in the permafrost is changing due to the permafrost being extremely sensitive to changes in temperature
• Permafrost melting releases carbon dioxide and methane causing a positive feedback loop
• This is at 7-40 million tonnes per year
• Gas flaring and oil spillages release more carbon dioxide into the atmosphere
• Vegetation removal causes less carbon fixation by photosynthesis

Insulated ice and gravel pads

• Roads and other infrastructure is built on top of insulating ice or gravel so the transfer of heat decreases so less permafrost is melted

Elevated buildings and pipelines

• By elevating pipelines that contain oil at 65-85 degrees Celcius, less heat is transferred to the permafrost so less permafrost is melted

Drilling laterally

• New technology and techniques allow construction to dill sideways
• By drilling sideways from the same drilling point on the surface, fewer drilling sites are required greatly reducing the impact on the permafrost on the top of the Tundra

More powerful computers for detection of oil

• This allows less exploration wells to be constructed so less of the permafrost is melted locally as the technology doesn't directly melt the permafrost

Refrigerated supports

• The Trans-Alaska pipeline uses supports that are refrigerated to reduce the transfer of heat to the permafrost
• Can also be used around buildings protecting the frozen environment from the hot oil