Carbon Cycle 1: System concepts Flashcards
What is the carbon cycle?
Biogeochemical cycle in which carbon moves from one part of the global store to another
What kind of system is the carbon cycle at a global scale?
A closed system
The amount of carbon remains constant
There is a mass balance
What kind of system is the carbon cycle on a local scale?
An open system
Mass balance is not constant
Balance changes as carbon enters or leaves the sub-system
Carbon is one of the essential building blocks of what?
Organic life
Carbon is essential due to its unique ability to form what?
Vital different bonds with other elements
What kind of resource is carbon?
Finite
Explain stores
Amounts of carbon held in the global system
e.g. atmosphere, oceans and biosphere, lithosphere
Explain flows
Movements or transfers of carbon between stores
Volcanic activity adds 0.1 gigatons of carbon to the atmosphere annually
What are flows i into stores called?
Inputs
What are flows leaving stores called?
Outputs
What is an example of the sequestration of carbon?
Photosynthesis
What are the 4 processes of carbon pathways from land to the atmosphere?
Photosynthesis
Respiration
Decomposition
Fossil fuel combustion
Explain the process of photosynthesis in carbon pathways
Carbohydrate molecules are produced from CO2 and water using energy from light. Plants ‘fix’ gaseous CO2 into solid form in their living tissues
Net Primary Productivity (NPP) of an ecosystem is the rate at which new organic matter is produced by photosynthesis per unit area per unit time
Explain the process of respiration in carbon pathways
CO2 is released into the atmosphere by organisms by respiration. Plants create energy for respiration by breaking down stored glucose (sugars). CO2 is given off as a by-product
Explain decomposition in carbon pathways
cO2 is returned to the atmosphere when living organisms die: their cells break down as a result of physical (wind and water), chemical (leaching and oxidation) and biological (feeding and digestion) mechanisms (carried out by bacteria and fungi
Explain fossil fuel combustion in carbon pathways
Hydrocarbon (fossil fuel) combustion takes place rapidly in the presence of oxygen and releases CO2
Around 85% of global energy consumption is derived from coal, oil and gas fuels; traditional societies burn biomass on demand
What are the two carbon pathways from the ocean to the atmosphere?
Physical pump
Biological pump
Explain the physical (inorganic) pump
Movement of CO2 from atmosphere to ocean by diffusion
CO2 dissolved in the surface of the ocean can be transferred to the deep ocean in areas where cold dense surface waters sink
Downwelling carries carbon molecules to great depths where they may remain for centuries
CO2 diffusion determines the acidity of the oceans
Explain the biological (organic) pump
Driven by ocean phytoplankton absorbing CO2 via photosynthesis
These organisms form the bottom of the marine food web and live in the oceans surface layer
Phytoplankton are consumed by other organisms and carbon is transferred along food chains
Organic carbon may eventually be transferred to the deep ocean when dead organisms sink towards the ocean floor
What kind of form is carbon held in when in waters and the tissues of ocean dwelling organisms?
Dissolved form
What are the primary inputs and outputs of carbon from the oceans?
Gas exchange with the atmosphere, but there is also significant input of both organic carbon and carbonate ions from continental runoff
What is carbon flux within the oceans controlled by?
Physical, chemical and biological processes
What kind of impact does small changes to the oceanic carbon store have?
Significant global impacts
What proportion of carbon is eventually buried in ocean sediments?
Small proportion
But these sediments are important long term carbon stores
