CASE STUDY: The Arctic Tundra Flashcards
background facts on AT
- AT occupies some 8,000,000km2 in northern Canada, Alaska + Siberia
- av. monthly temps =regularly below freezing
- few flora + fauna have adapted to these conditions so biodiversity is low
- permafrost underlies much of the tundra
main features of the AT water cycle
- low annual precipitation: 50-350mm/year
- low rates of evaporation as Sun’s energy used for melting snow + surface/soil waters are mostly frozen
- limited groundwater + soil moisture as permafrost blocks infiltration, percolation + groundwater flow, so extensive wetland, ponds + lakes during summer due to permafrost preventing drainage
- limited transpiration due to sparseness of vegetation + short growing season
- accumulation of snow + river/lake ice during winter - melts in spring + summer = rapid increase in river flow
the permafrost in the AT is a vast…
carbon sink
how much greater is the amount of carbon in tundra soils than in above-ground biomass
the amount of carbon in tundra soils is 5x greater than in above-ground biomass
why is the flux of carbon concentrated in the summer months in the AT
- flux of carbon is concentrated in summer months, when active layer of permafrost thaws
- during summer growing seasons, tundra plants input carbon-rich litter to soil. activity of micro-organisms increases, releasing CO2 to the atmos. through respiration
how are CO2 and CH4 emissions not limited to summer months alone
- even in winter, small pockets of unfrozen soil + water in permafrost act as a source of CO2 + CH4
- meanwhile, snow cover insulates some microbes, allowing decomposition to continue even at very low winter temperatures
what concerns surrounding global warming and permafrost exist?
in the past, permafrost functioned as a carbon sink; but today, global warming has raised concerns that permafrost is becoming a carbon source
why is the release of methane particularly worrying, but how can this be countered and how can it be possible that the AT’s carbon budget is balanced
- the release of methane is particularly worrying as it can trap 30x as much heat as CO2
- however, higher temperatures have also stimulated plant growth = increased uptake of CO2 for photosynthesis as well as increasing the carbon store of plant litter
- It is thus possible that AT’s carbon budget remains balanced
what is carbon mainly stored as, where and for how long (in AT)
- carbon is mainly stored as partly decomposed plant matter frozen in the permafrost
- most of this carbon has been locked away for the past 500,000 years
what is carbon flux
the amount of carbon exchanged between Earth’s carbon sinks (eg. atmosphere, oceans)
what is biomass
the total quantity or weight of organisms in a given area or volume
when were oil + gas discovered in the North Slope of Alaska
oil + gas were discovered in the North Slope of Alaska in 1968
What did the USA do in the 1970s + 80s with ref. to the North Slope and why
- in the 1970s + 80s, massive investments went ahead (into oil pipelines, production plants, gas processing facilities, etc.)
- this was driven by high global energy prices + the USA’s attempt to become more oil independent
How much of the USA’s domestic oil production did the North Slope account for by the early 1990s (+ today?)
By the early 1990s, the North Slope accounted for nearly 1/4 of the USA’s domestic oil production (today still around 6%)
what significant impact on permafrost has the oil + gas exploitation of Alaska’s North Slope had and what has caused this impact specifically
- oil + gas exploitation on Alaska’s North Slope has had a significant impact on permafrost
- localised melting of permafrost has been caused due to:
- construction of oil + gas installations diffusing heat directly to environment
- dust deposition on roadsides creating darkened snow surfaces, thus low albedo (poor ability to reflect sunlight) increasing sunlight absorption
- removal of vegetation cover which insulates permafrost
