Earths support system Flashcards
Importance of water for the planet
key to understanding evolution of life on earth as provides medium that allows organic molecules to mix and form more complex structures, helps create benign thermal conditions on earth- oceans moderate temps by absorbing heat storing it and releasing it slowly, clouds reflect 1/5 incoming solar radiation and lower surface temps, water vapour absorbs long wave radiation to maintain avg global temps
Uses of water
makes up 65-95% of all living organisms and is crucial for growth reproduction and other metabolic functions
Plants- photosynthesis (takes place in leaves), respiration and transpiration
respiration converts glucose to energy through its reaction with O, releasing water and CO2, also need water for rigidity (plants wilt when they run out of water) and to transport mineral nutrients from the soil
People & animals- medium used for all chemical reactions in body like circulation of oxygen and nutrients, sweating is evaporative cooling, essential for economic activity- generates electricity, irrigates crops, receation, public demand, paper making, food manafacturing
Importance of carbon for the planet
stored in carbonate rocks like limestone, sea floor sediments, ocean water, the atmosphere and biosphere. life is carbon based-built on large molecules of carbon atoms like proteins
used as economic resource, fossil fuels power global economy, oil is used as raw material in manufacturing products
agricultural crops and forest trees store large amounts of carbon available for human use like food and timber
Water and carbon cycles
global scale- flow in closed systems between atmosphere, oceans, land and biosphere. cycling of individual water and carbon atoms occurs from days to millions of yrs- water- atmos 10 days oceans 3000 yrs
macro scale- water cycle has three main stores: atmos, oceans and land, atmos smallest oceans biggest, moves between through precip, evapotrans, run off and groundwater flow
carbon- long term storage in sedimentary rocks holds 99.9% of all carbon on earth, most carbon in circulation moves rapidly between the atmos, oceans, soil and bios, moved through photosynthesis, resp, decomp, combust, weathering
Water and carbon cycle as open and closed systems
global- closed systems driven by suns energy, only energy cross the boundaries of the global water and carbon cycles hence why its closed
smaller- eg drainage basin, materials and suns energy crosses system boundaries so it is open
Global water cycle
stores:
oceans- 1.37m km³x10³, 97% of global water
polar ice- 29,000, 2%
groundwater- 9,500, 0.7%
fresh water is only tiny amount of water in store and 3/4 is frozen in ice in antarctica, water stored in permeable rocks is 1/5 of fresh water
inputs of water: water evaporated from oceans soils lakes and rivers and vapour transpired through the leaves of plants-evapotranspiration
moisture leaves atmos as precip and condensation, ice sheets release water as ablation
precip and meltwater drain from land as surface run off into rivers and most flow to oceans, large part of water falling as precip reaches rivers after infiltrating and flowing through soil
Global carbon cycle
stores:
atmosphere- 600b tonnes
oceans- 38,700
sedimentary rocks- 60,000-100,000,000
carbonate rocks like limestone are biggest stores and most not stored are dissolved into oceans as co2
Slow carbon cycle
carbon in rocks, sea floor sediments and fossil fuels are locked away for millions of yrs, total amount of carbon circulated by slow cycle is 10-100 million tonnes a year
CO2 diffuses from atmos into oceans where marine organisms like clams make their shells and skeletons by fixing dissolved carbon together w calcium to form calcium carbonate. on death they sink to floor and heat pressure and time makes them sedimentary rocks
some carbon rich rocks, subducted into upper mantle at plate boundaries are vented to atmos in volcanic eruptions. others at surface are attacked by chemical weathering
Fast carbon cycle
circulates rapidly between atmos, oceans, soils and organisms. 10-1000 times faster than slow cycle
land plants and phytoplankton are key components, absorb co2 from atmos through photosynthesis and combine it with water to make carbs, fundamental for food chain
respiration is opposite and releases co2 as well as decomp
atmospheric co2 dissolves in ocean surface waters while oceans ventilate co2 back to atmos, through this exchange carbon atoms are stored in oceans for around 350 yrs
Water balance
summarises flows of water in a drainage basin over time
precipitation= evapotranspiration + streamflow +/- water entering or leaving storage
Flows in the water cycle- precipitation
water and ice that falls to ground from clouds, forms when vapour in atmosphere cools to dew point (critical temp when air becomes saturated and can hold no more vapour) and condenses into tiny water droplets or ice particles to form clouds, droplets aggregate, reach a critical size and leave cloud
intensity- amount of precip falling in a given time, high intensity moves quick overland into streams as falling at a rate exceeding the infiltration capacity of soil
duration- length of time that precip event lasts
causes: condensation in saturated air grow until they are heavy enough to fall to ground through any rising air currents beneath, happens through process of droplets coalescing as they collide w each other in turbulent air
Flows in the water cycle- transpiration
diffusion of water vapour to atmos from leaf pores (stomata) of plants. responsible for 10% moisture in atmos, influenced by temp and wind speed and water availability to plants- deciduous trees lose leaves to reduce moisture loss through transpiration
Flows in the water cycle- condensation
change of vapour to liquid water, occurs when air is cooled to its dew point, at this temp the air becomes saturated w vapour resulting in condensation
Flows in the water cycle- evaporation and interception
evaporation- phase change of liquid water to vapour and main way water enters atmos, heat needed to bring about evaporation and break molecular bonds of water, energy input does not produce rise of temp in water but energy is absorbed as latent heat and released later in condensation, allows huge amounts of heat to be transferred around planet
interception- vegetation intercepts proportion of rain storing it temp on branches leaves and stems, moisture eventually evaporates or falls to ground, rainwater briefly intercepted before dripping to ground is throughfall, during long periods it may flow to ground along branches as stemflow
Flows in the carbon cycle- precipitation
atmos co2 dissolved in rainwater to form weak carboic acid, anthropogenic emissions increased acidity of rainfall so ocean surface waters more acidic and harms marine life
Flows in the carbon cycle- photosynthesis
using suns energy, co2 from atmos and water, plants and phytoplankton convert light energy to chemical energy, used for growth and reproduction, release co2 from respiration
Flows in the carbon cycle- weathering
rainwater dissolves limestone and chalk through carbonation, releases carbon to streams rivers and oceans, most effective beneath soil cover bc higher conc of co2 in soil makes rainwater more acidic
chelation- rainwater + deacaying organic material in soil forms humid acids that attack rock minerals
Flows in the carbon cycle- respiration and decomposition
respiration-absorb o2 which burns carbs and provides energy for growth, releases c02
decomp- organisms like bacteria and fungi break down dead organic matter, extracting energy and releasing co2 to atmos and mineral nutrients soil, rates depend on climate
Flows in the carbon cycle- combustion
occurs when organic material reacts or burns in presence of oxygen, releases co2
natural fuel used in many ecosystems- wildfire from lightning important for coniferous forests of rocky mountains, long cold winters slow decomposition of forest litter and it builds up, fire shifts this freeing carbon and and nutrients that were inaccessible to forest trees, opens up canopy and increases biodiversity
also results from humans from burning forests for land and combustion of fossil fuels
Flows in the carbon cycle- carbon sequestration
physical pump- mixing of surface and deep ocean waters by vertical currents, creating more even distribution of carbon, co2 enters ocean from atmos by diffusion and surface ocean currents transport the water polewards where it cools, becomes more dense and sinks, this downwelling only occurs in handful of places- carried dissolved carbon to ocean depth where individual molecules may remain for centuries, eventually deep ocean currents transport it to areas of upwelling and co2 diffuses back to atmos
biological pump- marine organisms, half of all carbon fixation by photosynthesis occurs in oceans, phytoplankton near surface combine sunlight water and dissolved co2 to produce organic material, whether consumed or natural death carbon locked in PP accumulates in sediment on ocean floor or decomposed and released into ocean as co2, can also be lithified and form chalk and limestone
Amazon rainforest- water cycle
high average temps, small seasonal variation in temp, high rainfall
high temps due to intense insolation through the year but signif cloud cover ensure max temps do not reach desert temps
50-60% of precip in rainforest is recycled by evapotranspiration, water losses from amazon basin result from river flow and export of atmospheric vapour to other regions, made good by inward flux of moisture from atlantic ocean
precip- high intensity, interception high and intercepted rainfall accounts for 20-25% of all evaporation
ET- high rates due to high temps, abundant moisture and dense vegetation, strong et-precip feedback loops sustain high rainfall totals, half of incoming rainfall is returned to atmos through et, most evaporation from intercepted moisture from leaf surfaces, moisture lost in transpiration is derived from soil via tree roots
run off-rapid due to high rainfall and well drained soils
Amazon rainforest- carbon cycle
ideal conditions for plant growth
NPP is 2500grams/m2/year and bio mass is 400-700 tonnes/ha
large forest trees store 180tonnes c/ha above ground and 40 tonnes c/ha in roots
major global reservoir of carbon absorbing 2.4b tonnes a year, exchanges between atmos bios and soil are rapid, warm humid conditions ensure quick decomposition and rates of carbon fixation through photosynthesis is high
leached and acidic soils only have limited carbon and nutrients, poor soils yet highest npp shows the speed that matter is broken down and recycled
Amazon rainforest- physical factors affecting water cycle
geology- impermeable catchments (large parts of basin composed of impermeable crystalline rocks) have minimal water storage capacity leading to rapid run off, porous rocks store lots and have slow runoff
relief- most of basin comprises in low lands, in areas of gentle relief, water moves across surface (overland flow) or horizontally through soil (throughflow) to streams and rivers, in west the Andes has steep catchments with rapid run off, widespread inundation across floodplains occurs annually storing water for several months and slowing its movement to rivers
temp- high temps so high et, strong convection leading to high atmospheric humidity, development of thunderstorm clouds and intense precipitation
Amazon rainforest- physical factors affecting carbon cycle
60% of rainforest carbon stored in above ground biomass
temps- high temps rainfall and sunlight stimulate primary production
vegetation- leaf litter and dead matter decomposed quick due to high temps and humidity so emits more co2
geology- igneous and metamorphic rocks, carbonated in western part of basin so signif stores for slow carbon cycle
Amazon rainforest- human factors affecting water cycle
since 1970 1/5 primary forest destroyed
large flood on largest tributary of river and vast floodplains were inundated, 60 ppl died and 68,000 were evacuated
deforestation reduced water storage in forest trees,soils (eroded) permeable rocks (more rapid run off)
less trees- less et- less precip
run off increased so flood risk increased
cleared for farming and cattle ranching- 30,000km2 of bolivian rainforest gone in 2012
changes climate at local and global scale, extracts and intecepts moisture and maintains forest albedo and ground temps, sustains high humidity responsilbe for cloud formation and heavy convectional rainfall
predicted 20% decline in regional rainfall and forest dries out
