theme c - ecosystem feedbacks on climate change Flashcards
major fluxes of carbon
- atmosphere ocean
- atmosphere biosphere
- natural
- anthropogenic
major processes in the surface carbon cycle
- photosynthesis
- plant respiration
- microbial decomposition
- ocean atmosphere exchange
- fossil fuel combustion
what is the fast carbon cycle
- C on land in vegitation, soils and peat
- C in the atmosphere and surface ocean
- residence time of 10-10000 years
what is the slow carbon cycle
- huge stores of C in rocks and sediments in the lithosphere
- residence time over 10000 years
photosynthesis reaction
6co2 + 6H2O - C6H12O6 +6O2
- removes 120 GT/year of C from the atmosphere
- dependent on water availability, temperature, light and nutrient availability
what is the co2 fertilisation effect
- negative feedback loop
- more co2 in atmosphere (due to anthropogenic activity) = faster plant growth (more photosynthesis) = more co2 used, co2 level reduced = slower plant growth
plant respiration reaction
C6H12O6 + 6O2 - 6CO2 + 6H20 + energy
- represents half the co2 that is returned to the atmosphere in the terrestrial carbon cycle
carbon balance in plant - NPP
NPP = net carbon gains by plants
- balance between carbon gained through photosynthesis and carbon lost by respiration - GPP - R
- measured at the ecosystem scale over a specific time interval
soil respiration reaction
when does it happen and how much carbon is released
C6H12O6 + 602 - 6CO2 + 6H20 + energy
- happens when dead organic matter is decomposed
- average release rate of 90Gt/year
what is the solubility pump in the marine carbon cycle
- ocean atmosphere exchange
- as the atmosphere has a higher concentration of pCO2 that the ocean co2 flows down this gradient into the ocean
- co2 in the water undergoes dissolution and chemical reactions (highly dependent on temp as co2 more soluble in colder waters)
- co2 combined with h20 to make carbonic acid which then turn into bicarbonate then carbonate ions
what is the biological pump in the oceanic carbon cycle
- controlled by co2, nutrients (N,P) and pH
- exports carbon from the surface waters to the deep ocean
- surface waters are depleted in alkalinity and dissolved co2 beacuse of the pump (maintains a conc gradient)
processes involved in the ocean atmosphere exchange
- downwelling - transfer of cold or salty surface waters in to the deep ocean
- upwelling - deep waters rise to the surface bringing carbon, nutrients and alkalinity with them
- sedimentation - some carbon produced by marine biota accumulated at the bottom oft he ocean forms sedimentary rocks
human influence on the carbon cycle - ff
fossil fuel combustion - exponential rise
- 9.4Gt/year released
human influence of the carbon cycle - land use change
- has reduced the size of the land biota reservoir
- deforestation - most of the plant matter is either burnt or left to decompose
- tilling of agriculture soil leads to rapid decomposition and oxidation of soil organic matter
natural sources of methane emissions
- wetlands
- lakes and river
- geological sources
- wild animals
- wildfires
- permafrost
- oceans
anthropogenic sources of methane
- fermentation
- manure
- landfill
- rice cultivation
- coal mining
- oil and gas industry
sinks of methane
- oxidation by bacteria in aerobic soils
- chemical losses due to reactions with OH Cl
roles of remote sensing
- get quantitative information of the earths surface
- specially continuous maps
- get repeatable measurements over time - temporal archive
- detect featured not visible with our eyes
- looks back in time with satellite archive data
principles of remote sensing
remote sensing is the science , technology and art or obtaining information about an object, area or phenomenon by analyzing data acquired by a device this is not in physical direct contact with the object, area or phenomenon under investigation
steps involved in remote sensing
- energy source or illumination
- radiation and the atmosphere
- interaction with the object
- recording of energy by the sensor
- transmission reception and processing
- interpretation and analysis
- application
different types of sensors
- Passive RS - depends on the suns irradiance to provide energy
- active TS - uses an artificial source for energy (for night and through clouds)
- spaceborne or ground based
types of resolution
- spacial - relayed to angle and height to determine size of object - ability to distinguish 2 objects as separate
- temporal - frequency of an image acquisition at a constant location (everyday would be high, low 1 year)
- spectral resolution - width of a spectral waveband (finer has a thinner band)
- radiometric - sensory ability to discriminate slight differences in measured energy (finer more sensitive)
advantages to remote sensing
- Provides data for large areas - Allows collection of data in remote and inaccessible regions
- Increasingly long-time series of data available – temporal archive
- Relatively inexpensive in comparison to field sampling
- Easy and rapid collection of data
- Provides spatially-gridded, geo-referenced digital data
- Provides repeated sampling of the same area over time
limitations of remote sensing
- The interpretation of imagery requires experience
- Requires validation with ground data
- Data from multiple sources may create confusion
- Objects can be misclassified
- Can require complex corrections for geometric distortion and atmospheric effects
- Commercial satellites can be costly
- Cloud-cover/missing data
what is a carbon stock
the amount of carbon that is stored within a particular system
what is a carbon pool
a system that has the capacity to store or release carbon
what is a carbon flux
the amount of carbon exchanged between different pools within a given unit of time
carbon flux measurements
- tower based eddy-covariance methods
- in situ atmospheric co2 measurements
- remote sensing based on estimates
Tower based eddy-covariance methods
- micro meteorological method used to calculate vertical turbulent fluxes within the atmospheric boundary
- uses machine learning and satellite data to calculate flux measurements collected
- enables GPP at a global scale to be calculated
in situ atmospheric co2 measurements
Mauna loa
- is the longest continuous record of atmospheric co2 concentrations available
- local influence of vegetation or human activity in minimal here
- methods and equipment have remained constant over the last 50 years
remote sensing based estimates to measure co2 concentration
- chlorophyll fluorescence - proxy for GPP
- how light energy falling on a leaf if portioned
- physiologically related to photosynthesis
- affected by changed in efficiency and APAR
- less affect by atmosphere - Modelling terrestrial carbon fluxes
- done using RS and meteorological data
- light use efficiency models
- terrestrial carbon models
- can make future predictions
remote sensing techniques for monitoring carbon stocks
- active microwave - RADAR
- LiDAR
- optical
how does active microwave remote sensing techniques monitor carbon stocks
- a directed beam of microwave pulses are transmitted from an antenna
- energy interacts with the terrain and is scattered
- the backscattered microwave energy is measured by the antenna
- radar determines the direction and distance of the target from the instrument and its properties
- different vegetation structures have different scattering
how does LiDAR monitor carbon stocks
- laser generates an optical pulse
- high speed counter measures the time of flight from the start pulse to the return pulse
- time measurement is converted to distance - used to determine the elevation and location
- multiple returns can be measured for each pulse
traditional measurement techniques for carbon stocks
- local scale
- discrete measurements
- labour intensive
- allometric equations (only one that can do bellow ground)
how are organic soil carbon stocks measured
C density = bulk density x %C
- multiply carbon density of each soil samples to the volume of soil it represents per ha
challenges in global ecology
questions
- what is PP globally and what controls it
- how much carbon does the biosphere store and how it could change
- how does direct human exploitation of the biosphere affect productivity and carbon storage
- can the future of terrestrial carbon storage be predicted
definition inorganic carbon
carbon extracted from ores and minerals
definition of organic carbon
carbon found in nature from plants and living things
inorganic carbon cycle
- has always happened
- carbon leaves the atmosphere by dissolving in rainwater as carbonic acid or by reacting with silicate rocks forming limestone
- carbonate ions enter ocean can can be buried by tectonic movements - co2 enters mantle
- co2 released by volcanic eruptions
geological impacts of oxygen
- iron pyrite oxidises to iron oxides
- this produces sulphates which react with water to make sulphuric acid
- sulphuric acid reacts with other carbon containing rocks to produce more co2 and carbonate ions
what caused oxygen levels to rise 1000 million years ago
- burial of carbon from organic matter that did not decompose
- burial of pyrite
why was there low decomposition in the past = ff formation
- carboniferous - large plants fell into swamps (lack of microbes and anaerobic) and were buried before they could decompose = fossil fuel formation
- oceanic - organic matter ends up n ocean sediments and is buried before decomposition under high pressure
why has the carbon cycle changed over time
- major evolutionary steps
- mass extinctions
- changes in volcanic activity
humans: - increased speed of geological cycle as more weathering (more evaporation = more clouds = more carbonic acid)
- plants increase biological weathering
- leaf litter decomposes by fungi and microbes in soil - organic acids and co2 released which lower soil pH = increased weathering
how have humans changed the carbon cycle
specific examples
- deforestation - reduced photosynthesis and decomposition
- mining - exposes pyrite to oxygen and water producing sulphuric acid which weathers limestone and carbonate rocks (released co2 and bicarbonate ions) - AMD
- ff combustion - anthropogenic co2 - carbon moved from the slow to fast cycle
why have oxygen levels decreased recently
- combustion of ff uses oxygen
- deforestation reduces oxygen production as less photosynthesis
- more co2 = less o2 proportionally
how can the geological cycle be used to help the climate situation
enhances rock weathering (ERW)
- physically break up and spread out silicate rocks (higher SA)
- when weathering occurs co2 will be taken up by soil
- over time runoff will transfer carbon to ocean where it can be stores up to 10000 years
benefits of enhanced rock weathering
- can use industrial waste from mining
- can be used on agriculture land - no competition for land use as can do both
- can fertilize agricultural land as it contains phosphate and potassium
how much stronger is methane than co2
high GWP - 30x stronger
anthropogenic GHG emissions by economic sector
- electricity production (25%)
- food, agri, land use (24%)
- industry (21%)
what controls GHG in the atmosphere
- sources from human activity (land use, deforestation, ff)
- anthropogenic sinks (land, ocean, machines)
- natural background sinks (forests, oceans)
when should net 0 be reached by
Paris agreement
- 2C warmer (max) by 2100
- would have to have achieved a reduction of 20% from 2010 levels by 2030 to be achievable
- has been a large increase in pledges and agreements in Europe since 2019
how could net 0 be achieved
- reduce sources
- phase out coal plants
- invest in renewable energy - improve society
- invest in energy efficient tech
- increase public transport
- reduce food waste - improve sinks
- afforestation
- CCS
government must - provide clear plans and build confidence among investors, industry and citizens
net 0 commitment in the UK
- legislation and targets
- net 0 by 2050 - carbon budget periods
- climate change act legally binding - international commitment
- Paris agreement - cut emissions by 72% - progress and challenges
what is the UK doing to reduce emissions
- energy white paper
- transport decarbonization plan
- industry decarbonization plan
- hydrogen strategy
- reduce demand
- improve efficiency
- electrification
geoengineering solution to CC
deliberate large scale intervention in the earths natural systems to distress cc
1. SRM - solar radiation management ( reducing the amount of heat the reaches the earths surface thus reducing the temperature
- aerosol injection
- high albedo crops and buildings
- marine cloud brightening (increased clouds=reflected more)
- ocean mirrors
2. GGR and CDR
challenges to geoengineering solutions to fix CC
- unintended consequences
- ozone depletion
- cost
- reduced solar power (have to now pick a target so money is not wasted in production of solar energy plants)
- danger of rapid climate change if we stop doing them
what processes does CDR involve
- intentional capture and removal of a GHG from the atmosphere
- storage and capture of the GHG in a form that prevents their release into the atmosphere for a prolonged period of time
how can CDR methods be classified by
- GHG removal method
- biological uptake
- inorganic reactions
- engineering capture - storage location
- geological reservoir
- built environment
- land store
- ocean store
what is CCS
carbon capture and sequestration
- technology capture co2 from a large point of source
- captured co2 is stored in underground geological formations
what is DACCS
direct air capture and carbon storage
- comprises of various technology using chemical bonding to extract atmospheric co2 and subsequently store it
- co2 is captured into a separating agent which is later regenerated using heat or water - this processes releases co2 as a high purity stream that can be geologically stored, or mineralised or utilised
natured bases CDR strategies
strategies that increase carbon storage in living plants, soil or sediments
- coastal blue carbon
- peatland restoration
- afforestation
- enhanced rock weathering
- biochar
- soil management
what is coastal blue carbon
- coastal wetlands store large amounts of carbon despite their relatively small size
- 30M ha could be restored
- could lead to an increased sequestration of 200MtCo2e/yr
international wetland restoration projects
- Apple, conservation international and Goldman Sachs launched a $200 million restoration fund for mangroves in the Philippines, Columbia and Honduras
- 100 million mangroves are targeted to be planted by 2030 - would offset 96M tons of carbon and stabilise coastline ecosystems
- Hoverton Norfolk wetland restoration project - reverse decades worth of pollution - soft sediment was removed and biomanipulation is occurring
what is BECCS
bioenergy with carbon storage and sequestration
- biomass combustion (of waster and crops)
to generate energy with CCS
what is ocean fertilisation
adding nutrients (P and Fe) to increase the biological pumps
- increases carbon removal from the surface and facilitates its transfer to the deep ocean
- addition uptake of co2 from the atmosphere occurs to compensate from the loss as concentration gradient got steeper
figures of global carbon stocks
- living vegetation - 550Gt
- soils - 2300Gt
- oceans - 380000Gt
