Alaskan Tundra Flashcards
what are the mean temperatures?
below -15°C
how many months is the tundra in a negative heat balance?
8 to 9
mean annual precipitation is
low
describe the biodiversity and ecosystem
biodiversity is low and apart from a few dwarf species, the ecosystem is treeless
Are the conditions in the lower arctic similar to the northern arctic
Conditions are less severe In the lower arctic
describe annual precipitation pattern
low annual precipitation, with less than 100mm in some locations, mostly falling as snow
Describe and explain the atmospheric moisture store.
small moisture owing to lower temperatures which reduce absolute humidity
Give 2 reasons why the transpiration rates are low
limited due to sparsness of vegetation and short growing season of only 3 months
why are there low rates of evaporation?
This is because the solar energy is concentrated on melting ice so ground temperatures remain low and inhibit convention.
why are there limited groundwater and soil moisture stores?
Permafrost is a barrier to infiltration, percolation and groundwater flow
Why does river flow increase In the tundra? Give an example of this
Accumulations river and lake ice and melting during spring and summer increases river flow. The Yukon river has a minimum discharge of 340 cumecs in the winter and maximum of 24,600 in the summer
How many lake and wetlands are found in Alaska? Give a reasoning behind this figure.
over 3 million, there are so many owing to impermeability of permafrost
How much carbon is held in the permafrost?
over 1600GT, it’s a global carbon sink.
overall carbon held in tundra soils is … greater than the above ground biomass
5x
What time is flux of carbon concentrated? what is the NPP?
During the summer, when the long daylight hours allow plants such as crowberry to flower within just a few weeks. But average NPP is still low, at less than 200 grams/m^2/year
Describe the flux of carbon to the atmosphere during summer and winter months.
Activity of micro organisms release carbon dioxide and methane to the atmosphere. Whilst, pockets of unfrozen soil and water in the winter release the 2, also snow cover insulates microbial organisms and can allow some decomposition to take place.
Explain why the permafrost may become a carbon source rather than sink and why some believe it will remain at balance.
Thawing of permafrost may lead to increased carbon dioxide in the atmosphere. It will also stimulate plant growth and greater uptake of Carbon dioxide. This will increase plant litter.It is therefore possible that the tundra today remains at balance
Name 3 factors influencing flows and stores of water in the tundra
- Temperature
- Relief
- Rock permeability
Explain the impact of temperature on flows and stores of water
- Average temperatures are well below freezing so most water is stored as ground ice in the permafrost
- shallow active layer thaws in the summer, forming millions of pools, with poor drainage
- Sub zero temperatures in the winter prevent evapotranspiration
- In the summer some evapotranspiration can occur
Explain the effects of permeability on flows and stores in the Tundra
Low permeability owing to the permafrost and precambrian igneous and metamorphic rocks which dominate the geology
Explain the geological structure impacts water flows and stores
The underlying rock structure has been reduced to gently undulating plain, the minimal relief impedes drainage and has led to waterlogged conditions
What is most carbon stored as In the tundra?
partly decomposed plants remains
Explain the effect of low temperatures on the flows of carbon in the tundra.
low temperatures, lack of liquid water and few nutrients within the rock structure limit plant growth. Total carbon stored in biomass Is low as well as NPP. However there is compensation for the short growing season of 3 months with long daylight hours.
What 2 factors reduce flow of carbon dioxide to the atmosphere?
owning to waterlogged conditions and low temperatures which slow decomposition
Impact of geology on water and carbon cycle?
It’s very limited owing to impermeable permafrost with the mineral composition exerting little pressure
where was oil and gas discovered in Alaska at 1968?
Prudhoe bay
What were the challenges of oil and gas drilling in the Alaska?
- Fragile wilderness of great ecological value
- Poor accessibility
- Remoteness
- Extreme weather conditions with long daylight hours
Give 2 reasons why drilling of oil went ahead despite the immense challenges.
High global energy prices and the US’s desire to reduce dependence on oil imports
By early 1990, how much of the USs oil production was from Alaska and how much has this changed by?
Was previously 1/4 but now less than 4%
Give 2 reasons why oil production has declined in Alaska.
- High production costs
- Massive growth of USs oil shale industry
Give 3 reasons for localised melting on the Alaskan tundra, caused by oil and gas companies
- construction of infrastructure and settlements has led to heat diffusion
- Dust deposition along roadsides has created darkened surfaces, which absorb more light
- removal of vegetation which insulates the permafrost
what are the estimated carbon dioxide on the North slope?
7 - 40 million tonnes/year
give 3 ways atmospheric carbon dioxide store is increasing?
- destruction and degrading of tundra vegetation means less uptake of carbon dioxide
- thawing of permafrost increases microbial activity and therefore decomposition
- oil spillages and gas flarings
carbon dioxide emissions on the tundra have increased by … since 1975 as an estimate
75%
why has flood risk increased due to oil and gas production
increased melting of permafrost and snow cover leads to more run off and river discharge, making flooding more likely
Explain the effect of strip mining for aggregates. Give an example.
Create artificial lakes which disrupt drainage and expose land to further melting. Artificial lake at goldstream has led to around 15m thawing in the last 60 years
What is the effect of water abstraction?
reduce localised run-off
give 5 management strategies and briefly explain there role in reducing impact on the W and C cycles
- Insulated gravel ice and gravel pads- roads an infrastructure can be built upon these to reduce melting, Spine Road at Prudhoe bay lies on a 2m gravel pad
- building and pipelines elevated on piles- construction on piles allows air to cooler air to circulate underneath and limit the impact of ice melt from heat generating buildings
- Lateral drilling- impact on vegetation is significantly reduced, as you can access areas from a single site, e.g. Shells snake drill
- Powerful computers- fewer exploration wells are needed, 10% of super computers are delivered to oil industry on average, 2 main tasks are seismic data processing and reservoir modelling
- Refrigerated supports- used on trans-Alaska pipeline to stabilise temperatures
