Arctic Tundra

• Cultivation


  Drastically reduce deforestation
• Arctic Tundra


  • Occupies 9 million km² northern Canada, Alaska and Siberia
  • Extends from the boreal edge of coniferous forest to the southern limit of the 10°C July isotherm
  • Harshest biosphere in the world
  • Coldest of all biomes
  • Underlain by permafrost
• Tundra


  • Climate limit of tree-lined vegetation
  • Important water cycle
  • Conditions less severe than the High Arctic
  • Continuous ground cover
  • Extensive areas of biodiversity low as ecosystem is treeless
• High Arctic


  • Plant cover is discontinuous with bare ground
• Climate


  • Extreme seasonality
  • Long periods of darkness in winter with temperatures below -40°C
  • Long daylight in summer provides some compensation for the harsh conditions
  • Annual precipitation is low
  • Negative energy balance for 8-9 months with average temperatures below freezing
  • Permafrost is permanently frozen except for the top metre which thaws in summer
• Due to the large distribution of sunlight in the north, the light is less concentrated
• Ocean currents


  Warm currents that keep the environment warmer
• Albedo


  • White surfaces reflect energy so less heat is absorbed
  • Positive feedback - warmer temperatures mean less ice, less reflection, warmer
• Water Cycles


  • Precipitation
  • Evaporation
  • Transpiration
  • Ground water
  • Surface water
• Precipitation


  • Low annual precipitation, mostly falling as snow
  • Due to low humidity and large areas of high pressure, cold air holds less moisture
• Evaporation


  Low rates due to the low temperatures which inhibit convection and the energy expended melting snow, keeping ground temperatures low
• Transpiration


  Limited due to the sparseness of vegetation cover and the short growing season of only 3 months
• Ground water


  Limited due to the permafrost barrier which impedes infiltration, percolation and recharge of groundwater flow
• Surface water


  • Accumulation of melting snow, river and lake ice during winter
  • Sharp increase in river flow during the spring and early summer as the uppermost active layer of permafrost thaws
• The Yukon River has a minimum discharge of 3,400 cumecs in winter and a maximum of 24,600 cumecs
• Liquid water


  Extensive wetlands, ponds and lakes on the tundra in summer, but temporary due to the permafrost which impedes drainage
• Permafrost


  • Frozen ground that remains frozen all year for at least 2 years
  • Found in cold climates at high latitudes and altitudes
  • The active layer freezes and thaws every year, ranging from 30-300 cm
• Permafrost underlies 25% of the exposed land surface in the northern hemisphere
• Carbon Cycle


  • Vegetation - Plants grow rapidly in the short summer with long daylight, but net primary productivity is less than 200 grams/m³/year and biomass is small at 4-29 tonnes
  • Decomposition is slowed by low temperatures and waterlogging, reducing the flow of CO2 into the atmosphere
  • Photosynthesis is limited by the lack of liquid water, daylight and nutrients
  • Respiration is slow due to the little vegetation and low temperatures, but anaerobic respiration can produce methane
• Soils


  • Carbon and nutrients are transferred into the soil during the growing season, with the amount of carbon stored in the soil 5% greater than the above-ground biomass
  • The permafrost acts as a carbon sink, containing 1600 gigatons of carbon in the full dead organic matter
• Higher temperatures


  Permafrost thaws, leading to the decay of organic matter, releasing more CO2 and methane, further increasing temperatures (positive feedback)
• Higher temperatures


  Stimulate plant growth, increasing CO2 uptake and partially offsetting the increased emissions (still in balance)
• Physical Factors


  • Temperatures - 8-9 months below 0°C with water stored as ice in the permafrost layer, then flowing on the surface during the short summer as the shallow active layer thaws
  • Humidity - Low all year round due to the sparse precipitation, with the cool air unable to hold much moisture
  • Permeability - Low due to the impermeable permafrost, leading to standing pools in summer
  • Geology - Precambrian igneous and metamorphic rocks dominate, preventing soil formation and drainage
• The relatively flat landscape is the result of glacial erosion and weathering, with minimal relief and glacial deposits impeding drainage and contributing to waterlogging in summer
• The low relief encourages more infiltration, but the impermeable permafrost means there is little surface runoff
• The mineral composition of the soils exerts little influence on the carbon cycle
• North Slope, Alaska


  • Vast wilderness area between the Brooks Range in the south and the Arctic Ocean in the north
  • Prudhoe Bay is a significant oil and gas production region, first discovered in 1968
  • Development of the oil and gas industry presented major challenges due to the harsh climate, permafrost, and remoteness of the region
• Infrastructure development


  Causes localised melting of permafrost, increasing surface runoff and river discharge, which in turn increases flooding and decomposition, further raising temperatures
• Removal of vegetation


  Reduces transpiration
• Strip mining and water abstraction

  Disrupt drainage and melt permafrost
• There has been a 10% decline in snow cover and 13m of permafrost thaw in the Arctic over the last 50 years
• Arctic warming is occurring 4 times faster than the mid-latitudes
• The North Slope releases between 7.4 million tonnes of CO2 and 24-114 thousand tonnes of methane per year from permafrost melting
• Melting permafrost


  Releases organic material which decomposes, releasing more CO2 and methane, further increasing temperatures (positive feedback)
• Increased vegetation growth


  Increases CO2 uptake, partially offsetting the increased emissions from permafrost thaw
• CO2 emissions from the North Slope are estimated to have increased by 7.3% since 1975
• Management Strategies


  • Emphasize protecting the permafrost and reducing thawing
  • Minimise disruption to water and carbon cycles
  • Use insulated ice and gravel pads to construct infrastructure while protecting permafrost
  • Elevate buildings and pipelines on piles to allow cold air circulation and insulate against heat-generated thaw
  • Use lateral drilling techniques to access resources from fewer sites, reducing impact on vegetation and permafrost
  • Use more powerful computers and seismic data processing to optimise drilling and production, reducing the need for exploration wells
  • Use refrigerated supports to stabilise the temperature of the permafrost beneath infrastructure