2.B - the carbon and water cycle in the Arctic Tundra Flashcards
what is the arctic tundra biome like?
- the arctic tundra occupies some 8 million sq kilometres and is located between the arctic ocean and the boreal forest to the south
- they are cold and treeless with very little precipitation
- the landscape is quite bare with vegetation specially adapted to the low temperatures (below 0°C for most of the year)
- consequently, the ground is frozen for much of the year and only surface layers may melt in the summer months
- this is known as permafrost
what is permafrost?
- a vast carbon sink
- it underlies much of the tundra and is an important feature of the region’s water cycle
- globally it is estimated to contain 1600 GT of carbon
- the accumulation of carbon is due to low temps which slow decompostion of dead plant material
- it makes up 25% of exposed surface in the N.hemisphere
how many people live in Tundra areas?
- less than 4 million people live in tundra areas
climate info for Barrow - how cold is it in the winter?
- from december to march its below -20°C
why is biodiversity and NPP going to be low in the Arctic Tundra?
- biodiversity is low as few plants and animals have adapted to this extreme environment
- 80% of water is locked up in permafrost
- water is the limiting factor in growth and for a great proportion of the year it is dark for 24 hrs
- photosynthesis and respiration rates are low
what is found in arctic tundra?
1/3 of global carbon that can be cycled
what are average temperatures like in arctic tundra?
- cold, average temps are well below freezing
- very seasonal in tundra
- climatic conditions are severe and become more extreme w/ latitude (sun rays are diffused and low levels of insolation)
- for 8/9 months out of the year the tundra has a negative heat balance w/ avg montly temps below freezing
- albedo effect
what are average temperatures like in arctic tundra and WHY?
- cold, average temps are well below freezing
- very seasonal in tundra
- climatic conditions are severe and become more extreme w/ latitude (sun rays are diffused and low levels of insolation)
- for 8/9 months out of the year the tundra has a negative heat balance w/ avg monthly temps below freezing
- albedo effect
temperature range varies hugely in tundra (32 degrees) - why?
- tilt of the earth = summer 24hr light winter 24hr dark
- in winter when for several weeks the sun remains below the horizon, temps can plunge below -40°C
- long hours of daylight in summer provide some compensation for the growing season
lower precipitation compared to the amazon in the tundra - why?
- during winter (6-8months), water on the ground is frozen and little plant growth = little evapotranspiration
- small stores of water in the atmosphere owing to low temps
- polar cell of descending air = high pressure (no rainfall)
- most precipitation falls as snow
N.P.P is low in tundra - why?
- due to cold and short growing season, and infertile soils and little liquid water
- lack of sunshine and warmth
roughly 3 months of the year where the temp is above zero - in these months temp and precipitation rates are higher but still low in comparison - why?
- few plants and animals have adapted to this extreme environment
- 24hrs sun = temps go up, water becomes available and flows become faster
what happens in the summer in the tundra?
- temps are above zero
- evapotranspiration can occurs = ↑ flows of water condensation = ↑ precipitation
what won’t you find in the tundra?
- trees
- most plants are less than 15cm tall
- it is very cold
- other than temperature, the amount of sunlight affects growth rates
- plants have to adapt to short winter days and very long summer days
what strategies do plants have to adapt to tundra conditions?
- grow very slowly and conservatively
- die back until correct growing conditions again
what is NPP?
- how much CO2 is being fixed in the stems and leaves
- in the tundra there is only positive NPP for a few months of the year
what is the water cycle like in the tundra?
- low annual precipitation (50-350 mm) with most falling as snow
- extensive wetlands ponds and lakes on the tundra during the summer. temporary store of water impedes drainage as it lays on top of permafrost
- limited transpiration because of the sparseness of the vegetation cover and the short growing season
- small stores of moisture in the atmosphere owing to low temperatures which reduce absolute humidity
- plants are able to grow and flower rapidly in the summer months when the active layer thaws. long hours of daylight allow for rapid photosynthesis
- low rates of evaporation. much of the sun’s energy in summer is spent melting snow so ground temps remain low and surface/soil water are frozen for most of the year
- limited ground water and soil moisture - permafrost is a barrier to infiltration, percolation, recharge and groundwater flow
- accumulation of snow and river/lake ice during the winter. melting of snow and ice and the uppermost active layer of the permafrost in spring and summer results in a sharp increase in river flow
what is the carbon cycle like in the tundra?
- NPP is low due to the short growing season. typically less than 200 g/m2/yr
- during the growing season, plants input their carbon rich litter to the soil and decomposition increases releasing CO2 into the atmosphere through respiration
- the permafrost is a vast carbon sink estimated to hold 1600GT of carbon
- this is due to the low temperatures which slow the decomposition of dead plant material
- the amount of carbon in tundra soils is 5x greater than in the above ground biomass
- even in the winter, there are pockets of unfrozen soil and water, which release CO2 and CH4. snow covers can insulate microbes, which allows slow decomposition
- the tundra biomass is small, ranging between 4 and 29 tonnes/hectare.
what is permafrost?
- permafrost is permanently frozen ground
- for 8 months of the year, the tundra’s water isnt going anywhere because it is frozen
- in the winter, almost all precipitation falls as snow
- in more northerly latitudes, permafrost is found everywhere, known as continuous permafrost
- this permafrost means that when summer rains come, the water stays on the surface of the land
- there is often little infiltration because the permafrost is impermeable and so is the ice beneath it
what happens in the permafrost when there is a slope?
- in areas where there is a slope, river flows can erode the landscape and can carry vast quantities of sediment downstream
what happens in the permafrost when it is flat?
- water pools on the surface
- there is often little infiltration because the permafrost is impermeable and so is the ice beneath it
what happens to waterlogged soil in the tundra?
- when the soil is waterlogged, the decomposition is anaerobic, meaning no oxygen is available
- this means that carbon gets broken down into methane (CH4), not CO2, (a more potent GHG)
why is precipitation low in the tundra?
- there is low annual precipitation (50-350mm) w/ most precipitation falling as snow
- high pressure = air is sinking = clouds can’t form = no precipitation
- small stores of moisture in the atmosphere owing to low temps = ↓ absolute humidity
what are transpiration rates like in the tundra?
- limited transpiration because of the sparseness of the vegetation cover and the short growing season
- movement of water in the drainage basin means ↑ evaporation and transpiration
- ↑ storage of moisture = more humid tundra
what are evaporation rates like in the tundra?
- low rates of evaporation
- much of the sun’s energy (insolation) in the summer is expended melting snow so that ground temperatures remain low and inhibit convection
- also, surface and soil water are frozen for most of the year
what is insolation?
the amount of solar radiation reaching a given area
what is the active layer and how does it change?
the near surface layer in a periglacial environment which SEASONALLY freezes and thaws
how does the active layer varying seasonally affect infiltration rates?
- melting of snow, river and lake ice, and the uppermost active layer of the permafrost in spring and early summer results in a sharp increase
what are water stores like in the tundra?
- accumulation of snow and river/lake ice during the winter months
- extensive wetlands, ponds and lakes on the tundra during the summer
- this temporary stores of liquid water is due to permafrost which impedes drainage
how does PERMEABILITY/GEOLOGY affect the flows and stores of the water cycle in the tundra?
- historically, permeability is very important as it allowed permafrost to form (now its not as sig)
- permeability is low owing to the permafrost and the crystalline rocks which dominate the geology of the tundra in the arctic and sub-arctic canada
- the geology of North Slope, which is the northern most region of Alaska consists of Triassic shales as cretaceous metamorphic rocks
- these are mainly impermeable to water
- geology makes very little difference as permafrost is impermeable anyway
how does TEMPERATURE affect the flows and stores of the water cycle in the tundra?
- temp remains below freezing for most of the year
- e.g. in BArrow it is only above freezing in June, July and August
- NO FLOWS CAN HAPPEN (no precipitation and no decomposition)
- this means that water is stored as ground ice in the permafrost
- during the short summer the active layer thaws and liquid flows on the surface
- 4 months of cool long summer days allow flowers and fruit.
- drainage is poor: water can’t infiltrate the soil because of the permafrost at depth
- in winter, sub-zero temps prevent evapotranspiration
- in summer, some evapotranspiration occurs from standing water, saturated soils and vegetation
- humidity is low all year and precipitation is sparse
what is the geology of North slope like?
- the geology of North Slope
- which is the northern most region of Alaska
- consists of Triassic shales as cretaceous metamorphic rocks
how does RELIEF affect the flows and stores of the water cycle in the tundra?
- gently rolling tundra in the north slope
- the ancient rock surface which underlies the tundra has been reduced to a gently undulating plane by hundred of millions of years of erosion and weathering
- minimal relief means drainage is poor.
why is the tundra important?
- the tundra is important as a global carbon store
- the tundra contains 1600 gigatonnes of carbon, and 5/6 of this is in the SOIL (a very significant global store of carbon)
why is the tundra SOIL important?
- the tundra contains 1600 gigatonnes of carbon, and 5/6 of this is in the SOIL (a very significant global store of carbon)
why is the accumulation of carbon so slow in the tundra?
- due to low temps
- which slow decomposition of dead plant material
why does photosynthesis only occur in the summer in the tundra?
- the flux of carbon is concentrated in the summer months when the active layer thaws
- plants grow rapidly in the short summer
- long hours of daylight allow them to flower and fruit within just a few weeks
what is the tundra NPP like? and what is the carbon per hectare?
- less than 200g/m2/yr
- consequently the tundra biomass is small, ranging between 4 and 29 tonnes/ha depending on the density of vegetation cover
in the summer, what happens to tundra soil and with microorganisms?
- durign the growing season, tundra plants input carbon rich litter to the soil
- the activity of microorganisms ↑, releasing CO2 to the atmosphere through respiration
- however, CO2 and methane emissions are not confined to the summer
- even in the winter, pockets of unfrozen soil and water in the permafrost act as sources of CO2 and CH4
- meanwhile, snow cover may insulate microbial organisms and allow some decomposition, despite low temps
what isn’t confined to the summer in the tunda?
- CO2 and methane emissions are not confined to the summer
- even in the winter, pockets of unfrozen soil and water in the permafrost act as sources of CO2 and CH4
- meanwhile, snow cover may insulate microbial organisms and allow some decomposition, despite low temps
what are the thoughts on the tundra as a carbon sink or source?
- in the past, permafrost has functioned as a carbon sink
- but today, global warming has raised concerns that it is becoming a carbon source
- at the moment the evidence is unclear
- while outputs of carbon from the permafrost have ↑ in recent decades, higher temps have stimulated plant growth in the tundra and greater uptake of CO2
- this in turn has ↑ the amount of plant litter entering storage
- it is possible that despite the warming arctic climate, the carbon budget in the tundra today remains in balance
how long has carbon been locked away in the soil and why?
- locked away for at least the last 500,000 years
- mainly stored as partly decomposed plant
how does TEMPERATURE influence the flows and stores of the carbon cycle in the tundra?
- low temps, the unavailabilty of liquid water for most of the year and parent rocks containing few nutrients all limit plant growtj
- thus, the total carbon store of the biomass is RELATIVELY SMALL (AO2)
- averaged over the year, photosynthesis and NPP are low, w/ the growing season lasting for barely 3 months
- however, there is some compensation for the short growing season in the long hours of daylight in the summer
- low temps and waterlogging slow decompostition and respiration and the flow of CO2 to the atmosphere
how does GEOLOGY influence the flows and stores of the carbon cycle in the tundra?
- owing to the impermeability of the permafrost:
- rock permeability, porosity and the mineral composition of rocks exert little influence on the water and carbon cycle
what is a thaw slump?
- when melting permafrost releases the sediments locked in the ice, resulting in rock and mud slides
- this means that carbon locked in the ground gets washed out to sea
what happens as temps rise in the tundra?
- as average temperatures in the tundra rise, the depth of ground that melts in the summer is becoming greater
- this makes the active layer become deeper, which can increase the fluxes of carbon from the soil (lithosphere) to the atmosphere
what is stored in tundra soils?
- about half of the world’s soil carbon is stored in tundra soils
- about 1/3 of the world’s movable carbon, which is found in the active layer.
what is the tundra POSITIVE FEEDBACK LOOP?
- the positive feedback loop is where the warmer temperatures mean that the active layer becomes deeper, this leads to greater carbon fluxes (more GHGs released into the atmosphere), leading to greater rates of global warming
- this feedback loop is known as ARCTIC AMPLIFICATION
- this could raise global temps by several degrees
what could happen as the tundra warms?
- as the tundra warms, decomposition rates will increase
- but also the biomass will change because plants can grow bigger and taller, and take on more biomass (thus fixing more carbon)
what is the tundra NEGATIVE FEEDBACK LOOP?
(not as sig as positive FL!!)
- the negative feedback loop is where due to warming, plants grow more, thus removing more CO2, which can slow or reverse climate change
will the tundra POSITIVE or NEGATIVE feedback loop be more significant?
- POSITIVE
- at least in the short term
- dangerous, could end up with a runaway process
what is the trans-alaskan pipeline?
- the trans-alaskan pipeline is taking oil from the oilfields in the north of the state (in places such as Prudhoe bay) to the port of Valdez in the south
- the pipeline was built between 1974 and 1977 after the 1973 Oil crisis caused a sharp rise in oil prices in the united states
- this rise made exploration of the prudhoe bay oil field economically feasible
- the pipeline has a max daily throughput of 1.4 mill barrels a day
how does the trans-alaskan pipeline link to the water cycle?
- the pipeline requires hot water to maintain high temps in order to prevent oil from freezing
- construction and function = melting permafrost
how does the trans-alaskan pipeline link to the carbon cycle?
- the pipeline transmits 1.4 million barrels of oil/day
- ↓ the need for tankers to transmit oil and consequently has ↓ the risk of oil spills in the arctic ocean
what are the drilling platforms in Alaska?
- a BP drilling platform in Prudhoe Bay
- this area produces around 55% of Alaska’s oil and gas, and in 2015 it averaged 281,000 barrels of oil equiv each day
how do the drilling platforms link to the water cycle?
- construction and operation can lead to localised melting of permafrost
- can increase river discharge and make flooding more likely
how do the drilling platforms link to the carbon cycle?
- permafrost melting due to construction of drilling platforms will input both CO2 and methane to atmosphere, while gas flaring will input carbon dioxide
- north slope area = 40 million tonnes CO2 and 114,000 tonnes CH4 released from melting permafrost /year
how are homes in Barrow constructed?
- the houses are built on stilts in order to preseve the permafrost underneath
- heating would otherwise melt permafrost and create unstable foundations
how do homes in Barrow affect the carbon cycle?
- if the permafrost melts due to heat from houses, it can release CO2 and methane that has been trapped until now
- promotes global warming and further melting of the permafrost
what is the natural tundra biome like?
- white mountains
- caribou grazing on mosses and lichen that grow in the tundra soils
how does the natural tundra biome impact the water cycle?
- the ground is frozen for most of the year = infiltration is limited
- plants have to be highly adapted to harsh climatic conditions and little liquid water
- dried sedges, lichen and small shrubs are the only vegetation able to grow so far north.
how does the natural tundra biome impact the carbon cycle?
- NPP is low and this is shown as there is limited plant growth
- this results from a short growing season of only 3 months/yr
- caribou have to migrate across Alaska in order to get enough food to sustain them
what is albedo effect?
- a measurement of how well a surface, e.g. snow/ice, bounecs sunlight back into space
how much faster is the arctic melting and why?
- up to 3x as much as average elsewhere
- as albedo effect in Arctic is decreasing, there is a positive feedback effect, because as the region warms more ice cover is lost
- as a result more dark areas are left exposed to sunlight etc
- ARCTIC AMPLIFICATION
what 3 things determine the albedo in the Arctic?
- sea ice
- snow on top of sea ice
- ice on land
how has warming affected the local weather?
- warming has lead to an increase in precipitation levels around the globe and in the arctic
- mainly rain as snowfall has ↓
why has the recent ECONOMIC DEVELOPMENT of Alaska occured?
- areas such as Siberia and Alaska have huge reserves of raw materials such as oil
- however, because they are periglacial environments certain challenges must be overcome
- for example, the major oilfields in Alaska are north of the state in the Prudhoe Bay area
- the area has been estimated to contain 25 million barrels of oil
- however the oilfield is located 250 miles north of the Arctic Circle
- the problem is how do you get the oil to the US markets and beyond?
where is the North Slope?
- the north slope represents the area between the Brooks range of mountains and the Arctic Ocean
- it is a vast area of Arctic tundra
- however, there os a huge reserve of oil and gas and the USA has been keen to utilise this in recent years
what is the main impact of drilling for oil in the North slope?
IT MELTS THE PERMAFROSTTTTTTTT
HUMAN ACTIVITY - 1
construction of oil and gas infrastructure including settlements, oil drilling rigs, houses etc.
HUMAN ACTIVITY - 2
dust deposition by the side of the road creating darkened surfaces, changing the amount of absorbtion of light (albedo effect)
HUMAN ACTIVITY - 3
removal of vegetation
HUMAN ACTIVITY - 4
strip mining of aggregates (sand and gravel) for construction
what impact does construction of oil and gas infrastructure have on the carbon cycle?
- construcion and operation of oil and gas installations, settlements and infrastructure diffuses heat directly to the environment
- gas flaring and oil spillages input CO2 to the atmosphere
- tundra vegetation destroyed by industrial development
what impact does construction of oil and gas infrastructure have on the water cycle?
- melting of the permafrost and snow cover ↑ run off and river discharge making flooding more likely
- draingage networks are disrupted by road construction and by seismic explosions to prospect for oil and gas
what impact does dust deposition have on the carbon cycle?
- dust deposition along the roadsides creates darkened snow surfaces
- thus ↑ the absorption of sunlight
what impact does dust deposition have on the water cycle?
- in summer, wetlands, ponds and lakes have become more extensive
(↑ evaporation)
what impact does removal of vegetation have on the carbon cycle?
- photosynthesis and the uptake of CO2 from the atmosphere is reduced
- ↑ in microbial activity, decomposition and emissions of CO2
what impact does removal of vegetation have on the water cycle?
- removal of vegetation cover which insulates the permafrost
- the slow growing nature of tundra vegetation means that regeneration and recovery from damage takes decades
what impact does strip mining of agregates have on the carbon cycle?
- release of CO2 and CH4
- estimated at the Nroth Slope, CO2 losses from permafrost vary from 7-40m tonnes per year
- CH4 losses range from 24,000-114,000 tonnes/yr
what impact does strip mining of agregates have on the water cycle?
- strip mining of agregates (sand and gravel)
for construction creates artificial lakes which disrupt drainage and also expose the permafrost to the sun - water abstracted from creeks and rivers for industrial use and for the building of ice roads in winter reduce localised run off
how much have temps increased?
- mean temperatures in the western arctic have increased by 3.4 degrees C since the 1960s
how is the changing climate impacting people and how are they adapting?
- forced to move inland
- cooling systems under new houses
what management strategies have been put in place to minimise the impacts of drilling for oil in the arctic?
- insulated ice and gravel pads (protects permafrost from melting)
- buildings and pipelines elevated on piles = insulation against heat generating infrastructure
- drilling laterally beyond drilling platforms - fewer sites needed = ↓ construction impacts
- refrigerated supports = stabilise the temp of the permafrost and conserves it
how might the pipeline interfere with caribou migration?
- pipeline crosses caribou migration route and may stop movement and affect breeding patterns
how can offshore oil exploration be harmful?
- offshore oil exploration, drilling and production can disturb the fish and animals that are integral to the livelihoods of Indigenous people in the arctic
- seismic noises like the air gun used by oil and gas companies to explore for oil offshore can be deafening for whales and other marine mammals who use sound to navigate
how do insulated ice and gravel pads reduce the impacts of oil and gas exploration?
- roads constructed on insulating ice/gravel pads protect permafrost from melting
how does building and pipelines on elevated stilts reduce the impacts of oil and gas exploration?
- the buildings and pipelines are placed on stilts and this slows down the melting of the permafrost
- it allows cold air to circulate beneath structures
- this means the permafrost remains intact and frozen, thus preserving the water cycle
- if this doesn’t happen then the ground becomes saturated and because evaporation is so limited there will be lots of surface water
- by preserving the permafrost there will also be slow rates of decomposition and so carbon remains in the soil
how does drilling laterally beyond drilling platforms reduce the impacts of oil and gas exploration?
- new techniques to access oil/gas kilometres away from drilling sites
- ↓ sites needed for drilling rigs = ↓ impact on vegetation due to construction
how do more powerful computers reduce the impacts of oil and gas exploration?
- less exploration wells necessary (it costs more money to drill these) = ↓ impact on environment
- economic incentive
how do refrigerated supports reduce the impacts of oil and gas exploration?
- used on Trans-Alaskan pipeline to stabilise temp of permafrost or conserve it beneath infrastructure
why are oil companies trying to preserve the permafrost?
- its in their economic interest to protect the permafrost
- if it melts it will affect their machinery
what impacts of oil and gas exploration are more significant?
- GLOBAL IMPACTS = more than local impacts
- they can manage local impacts more effectively
- globally, they are indirectly causing permafrost to melt = arctic amplification and global warming
how do the management strategies compare in effectiveness to the amazon basin?
- affected by level of development
- can’t reverse effects as easily as its so fragile
- amazon is easier to afforest
- scale of impacts is worse in Amazon
