ELSS Casestudy: Arctic tundra Flashcards
1
Q
What are the climatic conditions of the Arctic tundra?
A
- Mean temperatures of below -15°C.
- Negative heat balance
- Low annual rainfall of less than 100mm in most places, falling as snow.
2
Q
Outline the water cycle operating in the tundra
A
- There is low annual precipitation flow (less than 100mm), with most precipitation being snow.
- Small atmospheric store as low temperature reduce absolute humidity
- Limited transpiration due to sparseness of vegetation cover and short growing season of 3 months
- Low rates of evaporation flows, as most of the sun’s energy is expended on melting snow so ground temperatures stay low and inhibit convection.
- Surface and soil water stores are frozen for most of the year
- There are limited groundwater and soil moisture stores as permafrost is a barrier to infiltration, percolation, recharge and groundwater flow.
3
Q
What occurs in the summer in the tundra?
A
- There is melting of snow, river and lake ice, as well as the uppermost layer of permafrost.
- This leads to a sharp increase in river flow, such as in the River Yukon
- The Summer introduces temporary stores of extensive wetlands, ponds and lakes. This is temporary as permafrost impedes drainage.
4
Q
How much carbon does the permafrost contain?
A
1600 GT.
5
Q
Outline the tundra’s carbon cycle
A
- Accumulation of carbon is low due to low temperatures slowing decomposition of plant material and biomatter.
- The flux of carbon is concentrated in the summer months when the active layer thaws.
- Carbon flow happens primarily during the rapid growing season, where tundra plants input carbon-rich litter into the soil.
- Activity of micro-organisms also increases, releasing CO2 to the atmosphere through respiration.
- Even in winter, CO2 and CH4 emissions still occur as pockets of unfrozen soil and water act as sources, and snow cover can insulate micro-organisms to allow decomposition even at low temperatures.
6
Q
Discuss the role of the permafrost as a carbon store, and what is happening?
A
- The permafrost functions as a carbon sink
- Despite this, scientists are suggesting that it can transition to be a carbon source due to global warming.
- While outputs of carbon from permafrost have increased in recent decades, higher temperatures have stimulated plant growth in the tundra and greater uptake of CO2 - increasing the amount of plant litter entering store.
- So, therefore, it is possible that despite Alaskan climate warming, the carbon budget is remaining in equilibrium.
7
Q
What physical factors affect the tundra water cycle?
A
- Temperature
- Relief
- Geology (rock permeability and porosity)
8
Q
How does the physical factor of temperature impact the tundra water cycle?
A
- The low temperatures in the tundra (-15°C+) means that water is primarily stored as ground ice in the permafrost layer.
- When temperature slightly fluctuates in the summer the shallow active layer, the top section of permafrost, melts and liquid water flows on the surface.
- Meltwater, caused by the temperature dependent melting of the active layer forms millions of pools and shallow lakes as a seasonal store.
- With this temperature-based store accumulation, drainage is poor so water cannot infiltrate the soil due to the permafrost at depth - causing potential run-off and increased river discharge.
- Evapotranspiration is affected by temperature, in the winter temperatures prevent evapotranspiration. In the summer, some evapotranspiration occurs from standing water, saturated soil and increased vegetation cover.
- As a result of low temperature, humidity is low annually so precipitation as an input is sparse.
9
Q
How does the physical factor of geology (permeability and porosity) impact the tundra water cycle?
A
- Permeability is low due to the permafrost and Precambrian igneous and metamorphic rocks - these dominate the geology of the tundra in Alaska
- This means that, when water is more present on the landscape, run-off or throughflow can occur - increasing river discharge and output.
- River discharge flow names: channel flow, channel capacity
10
Q
How does the physical factor of relief impact the tundra water cycle?
A
- The ancient rock surface underlying the tundra has been reduced to a gently undulating plain from erosion and weathering over millennia.
- From minimal relief and chaotic glacial deposits, drainage is impeded - contributing to waterlogging during the summer months.
11
Q
What are the physical factors that affect the carbon cycle in the tundra?
A
- Temperature
- Vegetation
- Organic matter in the soil
- Geology (mineral composition)
12
Q
How does the physical factor of temperature impact the carbon cycle in the tundra?
A
- Low temperatures means that carbon is mainly stored as partially decomposed plant remains that are frozen in the permafrost.
- Low temperatures limits plant growth, as well as the fact that biodiversity is made scarce by this - there are poor conditions for growth such as parent rocks containing few nutrients. As a result, the total carbon store of the biomass is relatively small.
- Low temperatures and waterlogging slow decomposition and respiration - so inputs of CO2 to the atmosphere are limited.
13
Q
How does the physical factor of geology impact the carbon cycle in the tundra?
A
- The permafrost is impermeable, as well as the dominating Precambrian rocks - so rocks exert little influence on the carbon cycle.
14
Q
Where are most oil and gas industries located in Alaska?
A
On the North Slope
15
Q
Where was oil and gas first discovered in Alaska?
A
Prudhoe Bay
16
Q
In the early 1990s, what fraction of American oil was accounted for by the North Slope?
A
- Nearly 1/4
17
Q
How can oil and gas production impact the permafrost in Alaska?
A
- The permafrost is sensitive to thermal changes - so disruptions brought about by activities have caused localized permafrost melt.
- The three significant activities that lead to permafrost melt are:
- installations of infrastructure that diffuse heat directly to the environment
- dust deposition that creates darkened surfaces - increasing the absorption of sunlight
- removal of vegetation cover that insulates the permafrost.
18
Q
How has oil and gas production altered the carbon cycle in the tundra?
A
- Permafrost melting caused by industrial activity releases immense CO2 and CH4.
- On the North Slope, CO2 losses from permafrost are estimated to vary from 7-40 million tonnes per year.
- Gas flaring and oil spillages directly input CO2 to the atmosphere
- Industrial development has degraded tundra vegetation, disrupting the already delicate flows of photosynthesis (uptake of CO2) from the atmosphere
- Thawing of the soil from oil and gas industry increases microbial activity, decomposition and release of CO2.
19
Q
By what percent has CO2 emissions from the North Slope increased by since 1975?
A
- Increased by more than 73%
20
Q
Why is damage inflicted by the oil and gas industries in the North Slope very detrimental to the tundra’s recovery?
A
- The slow-growing nature of tundra vegetation means that regeneration and recovery from damage inflicted takes decades
21
Q
How has oil and gas production impacted the water cycle in the tundra?
A
- Melting of the permafrost and snow cover has increased run-off and river discharge, making flooding more likely.
- This means, in the summer months where this naturally occurs, wetlands, ponds and lakes will become more extensive which increases evaporation and input into the limited atmospheric store.
- Strip-mining of aggregates (sand and gravel) for construction creates artificial lakes which disrupt drainage and expose the permafrost to further melting.
- For example, artificial lakes created at Goldstream near Fairbanks have experienced 15m of permafrost thaw in the last 60 years.
- Drainage networks are disrupted by road construction and seismic explosions used to prospect oil and gas.
22
Q
Why is protecting the permafrost also beneficial for oil and gas companies?
A
- Oil and gas companies will benefit from protecting the permafrost as, when permafrost melts, it can cause widespread damage to road networks and buildings, as well as increasing maintenance costs for pipelines and other infrastructures.
23
Q
List the strategies used to reduce the impact of industrial development on the water and carbon cycles in the tundra
A
- Insulated ice and gravel pads
- Buildings and pipelines elevated on piles
- Drilling laterally beyond drilling platforms
- Using more powerful oil detection technology
- Refrigerated supports
24
Q
How does using insulated ice and gravel pads act as a strategy to reduce the impact of the oil and gas industry on water and carbon cycles?
A
- Roads and other infrastructural features can be constructed on insulating ice or gravel pads, thus protecting the permafrost from melting.
- For example, the Spine Road at Prudhoe Bay lies on a 2m deep pad
25
How does elevating buildings and pipelines on piles act as a strategy to reduce the impact of the oil and gas industry on water and carbon cycles?
- Constructing buildings, oil/gas pipelines and other infrastructure on piles can allow cold air to circulate beneath these structures
- This provides insulation against heat-generating buildings, pipework etc that would otherwise melt the permafrost underneath.
26
How does drilling laterally beyond drilling platforms act as a strategy to reduce the impact of the oil and gas industry on water and carbon cycles?
- Using new drilling techniques such as these allows oil and gas to be accessed several kilometers from the drilling site.
- Shell, for example, has developed a new '*snake drill*', allowing directional drilling across a wide area from a single drilling site.
- As a result, fewer drilling sites are needed so the impact on vegetation and the permafrost due to construction (access roads, pipelines and other facilities) is greatly reduced.
27
How does using advanced technology act as a strategy to reduce the impact of the oil and gas industry on water and carbon cycles?
- More powerful computers that can detect oil and gas bearing geological structures are being used remotely.
- Fewer exploration wells are needed as a result, reducing the impact on the environment.
28
How can using refrigerated supports act as a strategy to reduce the impact of the oil and gas industry on water and carbon cycles?
- Refrigerated supports are used on the Trans-Alaska Pipeline to stabilize the temperature of the permafrost.
- Similar supports are widely used to conserve the permafrost beneath buildings and other infrastructure.
