The Carbon Cycle and Energy Security – Physical Geography Notes
Paper 1
Biogeochemical Cycles
• This is a cycle in natural processes that recycle nutrients in various chemical forms
from the environment, to organisms, and then back to the environment
The 3 main biogeochemical cycles:
• Carbon cycle
• Water cycle (hydrological cycle)
• Nitrogen cycle
Systems
• A system is a set of interrelated components which are connected together to form a
working unit or unified whole
• Inputs: addition of maker or energy out of a system
• Outputs: movement of matter or energy out of a system
• Throughputs: the transfer of matter or energy through a system
• Feedback: a way of changing the input or process as a result of what happens at the
output
Ø Positive feedback: process that can amplify a small change and make it bigger
(this will shift the system away from its old state towards a new one)
Ø Negative feedback: process that diminishes change and make it smaller
• Dynamic equilibrium: although there are changes in the system, the overall system is
balanced – positive feedback may disrupt this state
2 types of system:
• A closed system – there is a transfer of energy but not matter between the system
and its surrounding
• An open system – when systems receive inputs and transfer outputs of energy/matter
across the boundary between them
Stores, fluxes and processes:
• Stores or stocks are the total amount of the material of interest held within a part of
the system
• Fluxes are measurements of the rate of flow of material between the stores
• Processes are the physical mechanisms that drive the flux of material between stores
1
,Within a system:
• Reservoirs – stores of materials such as carbon in a system (e.g. the atmosphere),
these reservoirs can act as sources or sink
• Fluxes – transfers of materials such as carbon between different stores in the system
(e.g. respiration)
The Carbon Cycle
• This is the biogeochemical cycle by which carbon moves from one sphere to another
• It acts as a closed system made up of linked subsystems that have inputs, throughputs
and outputs
Stores of carbon:
• The atmosphere, e.g. CO2, CH4
• The hydrosphere, e.g. CaCO3, calcium in coral
• The lithosphere, e.g. fossil fuels, limestone, slate
• The biosphere, e.g. plants, animals and soil
Units used to measure carbon:
2
, • Petagrams (Pg) or Gigatonnes (Gt) are the units used to measure carbon
• One petagrams is equal to one trillion kilograms or one billion tonnes
Carbon stores:
Long term stores (hundreds of years to millennia):
Store Store type PgC (average)
Crustal/terrestrial/geological Sedimentary rocks, very slow cycling 100,000,000
over millennia
Oceanic (deep) Most carbon is dissolved inorganic 38,000
carbon stored at great depths, very
slowly cycled
Short term stores (seconds to decades):
Store Store type PgC (average)
Terrestrial soil From plant materials; micro-organisms 1,500
break most organic matter down to CO2
by decomposition
Oceanic (surface) Exchanges are rapid with the 1,000
atmosphere through:
• Physical processes (CO2 gas
dissolving into the water)
• Biological processes (plankton)
Atmospheric CO2 and CH4 store carbon as greenhouse 560
gases with a lifetime of up to 100 years
Terrestrial ecosystems CO2 is taken from the atmosphere by 560
plant photosynthesis; carbon is stored
organically, especially in trees; rapid
interchange with the atmosphere
3
, Carbon fluxes and stores:
4
Paper 1
Biogeochemical Cycles
• This is a cycle in natural processes that recycle nutrients in various chemical forms
from the environment, to organisms, and then back to the environment
The 3 main biogeochemical cycles:
• Carbon cycle
• Water cycle (hydrological cycle)
• Nitrogen cycle
Systems
• A system is a set of interrelated components which are connected together to form a
working unit or unified whole
• Inputs: addition of maker or energy out of a system
• Outputs: movement of matter or energy out of a system
• Throughputs: the transfer of matter or energy through a system
• Feedback: a way of changing the input or process as a result of what happens at the
output
Ø Positive feedback: process that can amplify a small change and make it bigger
(this will shift the system away from its old state towards a new one)
Ø Negative feedback: process that diminishes change and make it smaller
• Dynamic equilibrium: although there are changes in the system, the overall system is
balanced – positive feedback may disrupt this state
2 types of system:
• A closed system – there is a transfer of energy but not matter between the system
and its surrounding
• An open system – when systems receive inputs and transfer outputs of energy/matter
across the boundary between them
Stores, fluxes and processes:
• Stores or stocks are the total amount of the material of interest held within a part of
the system
• Fluxes are measurements of the rate of flow of material between the stores
• Processes are the physical mechanisms that drive the flux of material between stores
1
,Within a system:
• Reservoirs – stores of materials such as carbon in a system (e.g. the atmosphere),
these reservoirs can act as sources or sink
• Fluxes – transfers of materials such as carbon between different stores in the system
(e.g. respiration)
The Carbon Cycle
• This is the biogeochemical cycle by which carbon moves from one sphere to another
• It acts as a closed system made up of linked subsystems that have inputs, throughputs
and outputs
Stores of carbon:
• The atmosphere, e.g. CO2, CH4
• The hydrosphere, e.g. CaCO3, calcium in coral
• The lithosphere, e.g. fossil fuels, limestone, slate
• The biosphere, e.g. plants, animals and soil
Units used to measure carbon:
2
, • Petagrams (Pg) or Gigatonnes (Gt) are the units used to measure carbon
• One petagrams is equal to one trillion kilograms or one billion tonnes
Carbon stores:
Long term stores (hundreds of years to millennia):
Store Store type PgC (average)
Crustal/terrestrial/geological Sedimentary rocks, very slow cycling 100,000,000
over millennia
Oceanic (deep) Most carbon is dissolved inorganic 38,000
carbon stored at great depths, very
slowly cycled
Short term stores (seconds to decades):
Store Store type PgC (average)
Terrestrial soil From plant materials; micro-organisms 1,500
break most organic matter down to CO2
by decomposition
Oceanic (surface) Exchanges are rapid with the 1,000
atmosphere through:
• Physical processes (CO2 gas
dissolving into the water)
• Biological processes (plankton)
Atmospheric CO2 and CH4 store carbon as greenhouse 560
gases with a lifetime of up to 100 years
Terrestrial ecosystems CO2 is taken from the atmosphere by 560
plant photosynthesis; carbon is stored
organically, especially in trees; rapid
interchange with the atmosphere
3
, Carbon fluxes and stores:
4
