CASTE STUDY - ARCTIC TUNDRA Flashcards
(10 cards)
water cycle in arctic tundra
- low precipitation (less than 100mm a year) - mostly as snow
- permafrost stores water for long periods –> acts as barrier to infiltration, percolation, groundwater flow
- summer thaw of the active layer allows surface flow and evaporation
- high snow accumulation in winter - melt water and river flow peak in spring/summer e.g. Yukon River: winter = 340 cumecs; summer = 24,600 cumecs).
- wetlands and lakes form temporarily in summer - more evaporation
carbon cycle in arctic tundra
- carbon stored in decomposed plant remains frozen in permafrost
- Global estimate: 1600 GT of carbon locked in permafrost soils.
- low NPP <200 g/m²/year.
- total biomass carbon: 4–29 tC/ha (small due to sparse vegetation)
- summer thaw allows plant litter input –> microbial activity –> co2 emissions
- winter microbial activity low but pockets of unfrozen water allow slow decomposition
Physical factors affecting flows and stores in the water cycle
- TEMP
- long cold winters (mean < –15°C) - most water stay frozen - low rates of evapotranspiration
- very short summers - but in summer active layer thaws and allows flow of liquid water
PERMEABILITY
- very low due to permafrost and impermeable igneous rocks
- prevents infiltration and slow drainage
RELIEF
- flat due to ancient glacial erosion –> poor drainage and waterlogged in summer
LITHOLOGY
- ancient, impermeable crystalline rocks dominate
- very little percolation or groundwater storage
Physical factors affecting flows and stores in the carbon cycle
TEMP
- low temps reduce decomposition –> slow carbon cycling
- short summer (2-3 months) allows plant growth and c02 release
VEGITATION
- infrequent and short (dwarf species, moss)
- inputs little organic matter
- most carbon stored in soil not biomass
ORGANIC MATTER IN SOIL
- permafrost locks organic atter away for 1000s of yrs
- decomposition only happens in brief thaw periods
MINERAL COMPOSITION
- igneous rocks contain few nutrients
- this low fertility limits plants growth and NPP
seasonal changes in water and carbon cycle - WHAT HAPPENS IN SUMMER
SUMMER
- active layer melts –> more surface water, run-off, river flow, evaporation
- short plant growing season (2-3 months) –> NPP slightly increases, more carbon absorbed and respired
- wetlands, ponds, lakes expand with melt water
- carbon fluxes increase the microbial activity
seasonal changes in water and carbon cycle - WHAT HAPPENS IN WINTER
WINTER
- water store in snow/ ice –> minimal flow
- soil/air temps drop to < –40°C.
- little microbial activity - plant growth and decomposition nearly stop
- frozen active layer prevents any further significant infiltration or flow
what oil and gas industries have been added to the arctic tundra?
- Oil/gas discovered at Prudhoe Bay (1968).
- Extensive infrastructure: pipelines, roads, production sites, gravel quarries, power plants.
what are the impacts of the oil and gas industry on the water cycle
- permafrost melts due to: roads + buildings increase heat, dust on snow darkens it - lowers albedo
- meltwater increases run-off and river discharge - flood risk
- construction destroys vegetation
- aggregates used for roads disrupt drainage patterns eg Goldstream artificial lakes
what are the impacts of the oil and gas industry on the carbon cycle
- Permafrost thaw → release of CO₂ (↑ 7 to 40 million tonnes/yr) and CH₄ (↑ 24,000 to 114,000 tonnes/yr).
- Gas and oil spills emit c02
- veg loss reduces photosynthesis and CO₂ absorption
- decomposition and emissions from microbes increased by 73% since 1975.
Management strategies to moderate the impacts of the oil and gas industry
- roads constructed on ice to prevent permafrost thawing
- elevated buildings - allow cold air to circulate, preventing ground heat transfer - used on Trans-Alaska pipeline
- drilling laterally - fewer surface disturbances hen accessing oil
- powerful computers which model the geology and seismic risk - reduce number of rigs needed
