ELSS Flashcards
NPP
Net primary Productivity
Positive and negative feedback
Positive feedback puts something out of equilibrium, eg. more accumaltion than melting of a glacier
Negative feedback also known as balancing feedback, puts it back into equilibrium
The Arctic Tundra general
Treeless plain, Occupies 8km2 in Northern Canada, Siberia and Russia
8-9 months a year, active layer is frozen = negative heat balance
Water cycle => Low annual precipitation (50-350mm)
Low evaporation rates (sun energy goes towards melting snow)
Limited groundwater due to permafrost
Extensive wetlands during summer, due to active layer melt (1m)
Summer melt = increase in river flow
global warming = active layer deepening as its warmer, more plant decomposition releasing CO2, therefore enhanced changes and positive feedback
Water cycle effected by => Temperature, rock permeability, porosity, and relief (gravitational energy of the movement of water)
Carbon cycle => NPP = less than 200 grams/m2/year versus NPP of tropical rain forest = 2,200 (biomass TRF = 45, Tundra = 0.6)
permafrost contains around 1600Gt (giga tonnes) of carbon
Soil in tundra is 5x more carbon rich than above ground biomass
arctic used to be carbon sink, however with global warming opposite affect due to melting this results in POSITIVE FEEDBACK
Carbon cycle effected by => temperature, vegetation, organic matter in soil, mineral composition of rocks
warmer temp means more carbon being used from the atmosphere for photosynthesis = NEGATIVE FEEDBACK
30% of all moveable carbon can be found in arctic tundra
Sea ice = protects coastline from erosion, which would cause release of carbon is eroded, climate change impact
Overall system effected by => climate, rock geology and lithology,
The Arctic Tundra anthropogenic activity
Human activity => oil extraction in Alaska - palmer gravel extraction(Lowered water table 2km from the side), gas flaring, urban barrow heat island (urban areas 2.2C warmer then rural surroundings)
Methane release due to anaerobic decomposition (organic material decompose without oxygen)
Carbon cycle =>
- Melting permafrost = CO2 and methane release , North slope loses 7-40 million tonnes of CO2 per year
- Gas flaring + oil spills = CO2 into atmosphere, and urbanisation and industrialisation means regular deforestation, more CO2 release due to reduced photosynthesis
- Soil thawing = more decomp. and CO2 release
Water Cycle =>
- Melting of snow = runoff and more likely flooding
- increased evaporation = wetlands, pools, lakes, drainage networks disrupted by roads from urbanisation
- localised runoff reduced = from water abstraction (extraction from natural source)
The Arctic Tundra Managment
Gravel pads (a layer of washed gravel, few inches thick at the point between contrustion site and ground) - insulates the ice and helps prevent permafrost from melting, infrastructure and roads are also built on pads to help
Elevating buildings pipes - allows cold air to circulate = insulation against heat meeting permafrost
Drilling laterally - can access oil + gas reserves kilometers away from drilling site = reduced number of drilling site = reduced affects of drilling over a wide area (contains the impacts to smaller area)
The carbon cycle processes
Evapotranspiration sequestration photosynthesis respiration sedimentation weathering - of rock = release of CO2 vegetation combustion decomposition - breakdown of organic material release CO2 into atmosphere
The slow carbon cycle
Carbon stored in rocks, sea floor, locked away fossil fuels
total amount of carbon circulated a year = 10-100 million tonnes
Typical residence time for carbon in rocks = 150 million years
Some of those rocks are sub-ducted into upper mantle and erupted in volcanoes into atmosphere
Rock near surface is weathered
The fast carbon cycle
vegetation and trees and living beings
Respiration + photosynthesis, circulates quickest between atmosphere, oceans, soil and living organisms
This process is 100 times faster than slow cycle
Land plants and phytoplankton are the key
The water cycle processes
Evaporation condensation evaporation infiltration / percolation interception runoff through flow groundwater flow precipitation Ablation
Spheres for water cycle
cryosphere atmosphere biosphere hydrosphere geosphere
3% of the earths water is fresh, oceans have 96.5% of all water
2% in ice
Diurnal changes
Changes during 24 hour period (photoperiod during light time of day)
Carbon => more photosynthesis during day, more sequestration of carbon
Water => Lower temps at night means reduced evaporation and transpiration
Seasonal changes
Carbon => photoperiod changes throughout year, therefore amount of photosynthesis
NPP changes
Phytoplankton - in ocean, stimulated into photosynthesis by rising water temps, more intense sunlight and lengthening of photoperiod
Water => summer means most evaporation due to sun and mroe vegetation in summer
soil moisture lowest in summer, evaporation and lower river flow
monsoons => regions of South East Asia receive 80-90% of annual rainfall during 3-4months of monsoon season
snowmelt, river increase in summer
Long term changes (over millions of years)
Carbon => glacial periods, dramatic reduction in CO2 from atmosphere
close correlation between temp and carbon concentration in atmosphere in the past 400,000 years
Excess carbon finds its way deep into ocean
Terrestrial biosphere changes - carbon pool in vegetation shrinks during glacials (ice sheets cover large amounts of land mass)
deserts expand and tundra replaces temperate forests
grasslands takeover forests
Algae photosynthesis more significant, CO2 dissolves better in cold
Water => net transfer of water from ocean reservoir to ice sheet, glaciers and permafrost storage
Due to glacial periods, sea levels fall by 100-130m
Ice and glaciers expand to cover around 1/3 of continental mass
potetriometric surface
the unseen line of the water table above ground surface, potential area for water to fill, wetlands
Human activities
The impact of fossil fuel combustion of flows and stores of carbon
2013 - Fossil fuels account for 87% of global energy consumption, 2% is renewable
Annually releases 10 billion tonnes of CO2, increasing atmospheric CO2 concentration by over 1ppm annually
Estimated that since 1750 increased anthropogenic energy accounts for less than 10% of the natural influx from biosphere etc. , still impacts cycle and size of stores
