2.b. It is possible to identify the physical and human factors that affect the water and carbon cycles in an Arctic tundra area

Question 1

Key facts about the Arctic Tundra

Answer 1

• occupies 8 milliom km² in nothern Canada, Alaska and Siberia
• climatic conditions are severe and become more extreme with latitude
• permofrost underlies most of the tundra and is an important feature in the water cycle
• biodiversity is low and but in the low Arctic, conditions are less severe with vegetation providing a continuous ground cover

Question 2

Water cycle in the tundra

Answer 2

• low annual precipitation with most preci falling as snow
• limited transpiration because of the spareseness of the vegetation cover
• limited groundwater annd soil moisture stores- permaforst is a barrier to infiltration, percolation, recharge and groundwater flow
• accumulation of snow and river/lake ice during winter months. Melting of the uppermost active layer of permafrost in spring and early summer results in a sharp increase in river flow
• small stores of moisture in atmosphere owing to low temperatures which reduce humidity

Question 3

Carbon cycle in tundra

Answer 3

• permafrost is a vast carbon sink- globally estimated to contain 1600 GT of carbon
• the accumulation of carbon is due to low temperatures which slow decomposition of dead plan material
• the flux of carbon is concentrated in the summer months where plants grow rapidly due to long hours of daylight. But Net primary producitity is low and so the tundra biomass is low
• during the growing season, tundra plants input carbon rich litter to soil by respiration. CO2 emissions also happen in winter- pockets of unfrozen soil/water act as sources of CO2
• in past, permofrost functioned as carbon sink but global warming has raised concerns that it is becoming a carbon source. A greater uptake of CO2 has increased plant litter entering store so the carbon budget remains in balance

Question 4

Physical factors, seasonal changes and stores and flows of water

Answer 4

Stores and flows are influenced by temperature, relief and rock permeability

• average temperatures are well below freezing so water is stored as ground ice. During the summer, the shallow active layer thaws and liquid water flows on the surface. Meltwater forms millions of pools and shallow lakes. Drainage is poor as water cannot infiltrate the soil. Humidity is low all uear round and prec. is sparse
• permeability is low owing to the permafrost and the crystalline rocks
• acient rock surface redued to a gently underlating plain by erosion and weathering

Question 5

Physical factors, seasonal changes and stores and flows of carbon

Answer 5

• carbon stored as partly decomposed plant remains frozen in permafrost
• low temperatures, the unavilability of liquid water for most of the year and parent rocks containing a few nutrients limit plant growth- so total carbon store of biomass is small
• low temperatures and waterlogging slow decomposition and respiration and the flow of CO2 to the atmosphere
• because of the imperability of permafrost, rock permeability, porosity and the mineral composition of rocks exert little influence on water and carbon cycle

Question 6

Oil and gas production in Alaska

Answer 6

• oil and gas was discovered in Prudhoe Bay in 1986
• the development of oil and gas industries on the North Slope presented major challenegs e.g. harsh climate with extreme cold and long periods of darkness in winter
• production still went ahead and was drived by high global energy prices and the US government’s policy to reduce dependence on oil imports. Massive fixed investmentd in pipelines, roads, oil production plants etc were completed in 1970/80s
• early 1990s- North Slope accounted for nearly a quater of USAs domestic oil production
• now 6% and decline due to high production costs and growth of oil shale industry

Question 7

Impact of oil and gas on carbon cycle

Answer 7

• permafrost , the major carbon store in the tundra, is highly sensitive to changes in the thermal balance- this balance has been disrupted by activities by oil and gas companies, causing melting. Melting associated with construction and operation of oil and gas instillations, dust deposition along roadsides and removal of vegetation cover
• permafrost melting releases CO2 and methane. North Slope CO2 losses vary from 7-40 million/tonnes/year. CH4 is 24,000-114,000. Gas flaring input CO2
• changes to carbon cycle linked to industrial development e.g. destruction or degrading of tundra vegegtation reduces photosynthesis and uptake of CO2 from atmosphere. The slow growing nature of tundra vegetation means regeneration/recovery takes decades

Question 8

Impact of oil and gas on water cycle

Answer 8

• melting of permafrost and snow cover incresses run off and river dishcarge making flooding more likely. In summer, wetlands, ponds, lankes become more extensive, increasing evaporation
• strip mining of aggregates for construction creates artificial lakes which disrupt drainage and expose permafrost to further melting. Drainage networks disrupted by road construction and seismic explosions
• water abstracted from creeks and rivers for industrial use and for building of ice roads reduce localised run off

Question 9

Management strategies to moderate the impact on water and carbon cycle

Answer 9

• emphasis to protect the permafrost to minimise disruption to water/carbon cycle
• insulated ice and gravel pads- roads and infrastructure features constructed on insulating ice or gravel pads
• more powerful computers to detect oil and gas bearing geological structures remotely- fewer exploration wells needed reducing impact on environment
• buildings/pipelines elevated on piles- allows cold air to circulate beneath structures to provide insulation against heat generating buildings