MET 112 Global Climate Change - Lecture 9 The Carbon Cycle Dr. Craig Clements San José State...
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Transcript of MET 112 Global Climate Change - Lecture 9 The Carbon Cycle Dr. Craig Clements San José State...
MET 112 Global Climate Change - Lecture 9
The Carbon CycleDr. Craig Clements
San José State University
Goals
We want to understand the difference between short term and long term carbon cycle
We want to understand the main components of the long term carbon cycle
The Earth’s history can be characterized by different geologic events or eras.
An Earth System Perspective
Earth composed of:– Atmosphere– Hydrosphere– Cryosphere– Land Surfaces– Biosphere
These ‘Machines’ run the Earth
Hydrosphere
Component comprising all liquid water– Surface and subterranean (ground water)
Fresh/Salt water Thus…lakes, streams, rivers, oceans…
Oceans:– Oceans currently cover ~ 70% of earth– Average depth of oceans: 3.5 km– Oceans store large amount of energy– Oceans dissolve carbon dioxide (more later)– Circulation driven by wind systems– Sea Level has varied significantly over Earth’s history– Slow to heat up and cool down
Land Surfaces
Continents Soils surfaces and vegetation Volcanoes
Climate:– Location of continents controls
ocean/atmosphere circulations
– Volcanoes return CO2 to atmosphere
– Volcanic aerosols affect climate
Biosphere
All living organisms; (Biota) Biota- "The living plants and animals of a
region.“ or "The sum total of all organisms alive today”– Marine– Terrestrial
Climate: Photosynthetic process store significant amount
of carbon (from CO2)
The Earth’s history can be characterized by different geologic events or eras.
Interactions
Components of the Earth System are linked by various exchanges including
Energy Water (previous example) Carbon
In this lecture, we are going to focus on the exchange of Carbon within the Earth System
Carbon: what is it?
Carbon (C), the fourth most abundant element in the Universe,
Building block of life. – from fossil fuels and DNA – Carbon cycles through the land (bioshpere),
ocean, atmosphere, and the Earth’s interior Carbon found
– in all living things – in the atmosphere – in the layers of limestone sediment on the
ocean floor– in fossil fuels like coal
Carbon: where is it?
Exists:– Atmosphere:
–CO2 and CH4 (to lesser extent)– Living biota (plants/animals)
–Carbon– Soils and Detritus
–Carbon–Methane
– Oceans–Dissolved CO2
–Most carbon in the deep ocean
Carbon conservation
Initial carbon present during Earth’s formation
Carbon doesn’t increase or decrease globally
Carbon is exchanged between different components of Earth System.
The Carbon Cycle
The complex series of reactions by which carbon passes through the Earth's
– Atmosphere – Land (biosphere and Earth’s crust)– Oceans
Carbon is exchanged in the earth system at all time scales
- Long term cycle (hundreds to millions of years)- Short term cycle (from seconds to a few years)
The carbon cycle has different speeds
Short Term Carbon Cycle
Long Term Carbon Cycle
Short Term Carbon Cycle
One example of the short term carbon cycle involves plants Photosynthesis: is the conversion of carbon dioxide and
water into a sugar called glucose (carbohydrate) using sunlight energy. Oxygen is produced as a waste product.
Plants require Sunlight, water and carbon, (from CO2 in atmosphere or
ocean) to produce carbohydrates (food) to grow. When plants decay, carbon is mostly returned to the
atmosphere (respiration)
Global CO2
Short Term Carbon Cycle
One example of the short term carbon cycle involves plants Photosynthesis: is the conversion of carbon dioxide and
water into a sugar called glucose (carbohydrate) using sunlight energy. Oxygen is produced as a waste product.
Plants require Sunlight, water and carbon, (from CO2 in atmosphere or
ocean) to produce carbohydrates (food) to grow. When plants decay, carbon is mostly returned to the
atmosphere (respiration)
During spring: (more photosynthesis) atmospheric CO2 levels go down (slightly)
During fall: (more respiration) atmospheric CO2 levels go up (slightly)
Carbon exchange (short term)
Other examples of short term carbon exchanges include:
Soils and Detritus: - organic matter decays and releases carbon
Surface Oceans– absorb CO2 via photosynthesis– also release CO2
Short Term Carbon Exchanges
How do we measure the short-term CO2 cycle?
– To determine the ecosystem exchange of CO2 we must measure the flux of CO2 between the biosphere and atmosphere.
– These measurements are routine and there is a network of stations that measure CO2 fluxes around the world.
How do we measure the short-term CO2 cycle?
– Ecosystems ‘breathe’ CO2 in and out.
– To determine the ecosystem exchange of CO2 we must measure the flux of CO2 between the biosphere and atmosphere.
– These measurements are routine and there is a network of stations that measure CO2 fluxes around the world.
CO2 Flux: Ecosystem ‘Breathing’
CO2 Exchange
CO2 Flux: Ecosystem ‘Breathing’
Fast, 3-D Anemometer
Fast, CO2 sensor(ms-1)
(mg m-3)
CO2 Flux: Ecosystem ‘Breathing’
CO2 Flux:
CO2 (ρ)concentration
Vertical Velocity perturbation (w’)
2COcF w
Flux = Eddy Covariance
To measure: Need fast velocity and CO2 measurements!
=(ms-1) x (mg m-3) =mg m-2 s-1
CO2 Flux: Ecosystem ‘Breathing’
H.P. Schmid (2000)
Long Term Carbon Cycle
Carbon is slowly and continuously being transported around our earth system.– Between atmosphere/ocean/biosphere – And the Earth’s crust (rocks like limestone)
The main components to the long term carbon cycle:
Where is most of the carbon today?
Most Carbon is ‘locked’ away in the earth’s crust (i.e. rocks) as – Carbonates (containing carbon)
Limestone is mainly made of calcium carbonate (CaCO3)
Carbonates are formed by a complex geochemical process called:– Silicate-to-Carbonate Conversion (long term carbon
cycle)
Silicate to carbonate conversion – chemical
weathering
One component of the long term carbon cycle
Granite (A Silicate Rock)
Limestone (A Carbonate Rock)
Silicate-to-Carbonate Conversion
1. Chemical Weathering Phase
• CO2 + rainwater carbonic acid
• Carbonic acid dissolves silicate rock2. Transport Phase
• Solution products transported to ocean by rivers
3. Formation Phase• In oceans, calcium carbonate precipitates
out of solution and settles to the bottom
Silicate-to-Carbonate Conversion
Rain1. CO2 Dissolves in Rainwater
2. Acid Dissolves Silicates (carbonic acid)
3. Dissolved Material Transported to Oceans
4. CaCO3 Forms in Ocean and Settles to the Bottom
Calcium carbonate
Land
Changes in chemical weathering
The process is temperature dependant: – rate of evaporation of water is temperature
dependant– so, increasing temperature increases weathering
(more water vapor, more clouds, more rain)
Thus as CO2 in the atmosphere rises, the planet warms. Evaporation increases, thus the flow of carbon into the rock cycle increases removing CO2 from the atmosphere and lowering the planet’s temperature– Negative feedback
Earth vs. Venus
The amount of carbon in carbonate minerals (e.g., limestone) is approximately– the same as the amount of carbon in Venus’
atmosphere
On Earth, most of the CO2 produced is
– now “locked up” in the carbonates
On Venus, the silicate-to-carbonate conversion process apparently never took place
Subjuction/Volcanism
Another Component of the Long-Term Carbon Cycle
Subduction
Definition: The process of the ocean plate descending beneath the continental plate.
During this processes, extreme heat and pressure convert carbonate rocks eventually into CO2
Volcanic Eruption
Mt. Pinatubo (June 15, 1991)
Eruption injected (Mt – megatons)
17 Mt SO2, 42 Mt CO2,
3 Mt Cl, 491 Mt H2O
Can inject large amounts of CO2 into the atmosphere
Organic Carbon Burial/Oxidation of Buried Carbon
Another Component of the Long-Term Carbon Cycle
Buried organic carbon (1)
Living plants remove CO2 from the atmosphere by the process of – photosynthesis
When dead plants decay, the CO2 is put back into the atmosphere – fairly quickly when the carbon in the plants is
oxidized However, some carbon escapes oxidation
when it is covered up by sediments
Organic Carbon Burial Process
CO2 Removed by Photo-Synthesis
CO2 Put Into Atmosphere by Decay
CC
O2
Some Carbon escapes oxidation
C
Result: Carbon into land
Oxidation of Buried Organic Carbon
Eventually, buried organic carbon may be exposed by erosion
The carbon is then oxidized to CO2
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon (e.g., coal)
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon (e.g., coal)
Erosion
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon
O2
CO2
C
Result: Carbon into atmosphere (CO2)
The (Almost) Complete Long-Term Carbon Cycle
Inorganic Component– Silicate-to-Carbonate Conversion – Subduction/Volcanism
Organic Component– Organic Carbon Burial– Oxidation of Buried Organic Carbon