1 MET 12 Global Climate Change - Lecture 7 The Carbon Cycle Shaun Tanner San Jose State University...
-
Upload
toby-jaggars -
Category
Documents
-
view
216 -
download
2
Transcript of 1 MET 12 Global Climate Change - Lecture 7 The Carbon Cycle Shaun Tanner San Jose State University...
1
MET 12 Global Climate Change - Lecture 7
The Carbon CycleShaun Tanner
San Jose State University
Outline Earth system perspective Carbon: what’s the big deal? Carbon: exchanges Long term carbon exchanges
2
3
4
5
6
7
8
9
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
10
An Earth System Perspective
Earth composed of:– Atmosphere– Hydrosphere– Cryosphere– Land Surfaces– Biosphere
These ‘Machines’ run the Earth
The Earth’s history can be characterized by different geologic events or eras.
12
Cryosphere
Component comprising all ice– Glaciers, – Ice sheets:
Antarctica, Greenland, Patagonia– Sea Ice, Snow Fields
Climate:– Typically high albedo surface– Positive feedback possibility store large amounts of
water; sea level variations.
16
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 (biosphere),
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.
17
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
19
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.
20
The Carbon Cycle
The complex series of reactions by which carbon passes through the Earth's
– Atmosphere,Land (biosphere and Earth’s crust) and 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)
Figure 4.13 Global carbon cycle
The carbon cycle has different speeds
Short Term Carbon Cycle
Long Term Carbon Cycle
23
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 decays, carbon is mostly returned to the
atmosphere (respiration) During spring: (more photosynthesis)
During fall: (more respiration)
24
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 decays, carbon is mostly returned to the
atmosphere (respiration) During spring: (more photosynthesis)
atmospheric CO2 levels start to go down (slightly) During fall: (more respiration)
atmospheric CO2 levels start to go up (slightly)
25
26
27
Question
What months are CO2 highest and lowest? Explain the factors that contribute to the annual cycle in CO2
emissions. (Why do CO2 levels go up and down?)
CO2 levels are largest in this month
1. Jan
2. May
3. August
4. October
CO2 levels are lowest when
1. Plants are growing and take up more CO2
2. Plants are decaying and take up more CO2
3. Plants are growing and give off more CO2
4. Plants are decaying and give off more CO2
30
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
Long Term Carbon Cycle
33
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:
1. Chemical weathering (or called: “silicate to carbonate conversion process”)
2. Volcanism/Subduction3. Organic carbon burial4. Oxidation of organic carbon
Silicate to carbonate conversion – chemical
weathering
One component of the long term carbon cycle
36
Granite (A Silicate Rock)
37
Limestone (A Carbonate Rock)
38
Silicate-to-Carbonate Conversion
1. Chemical Weathering Phase• CO2 + rainwater carbonic acid• Carbonic acid dissolves silicate rock
2. Transport Phase• Solution products transported to ocean by
rivers3. Formation Phase
• In oceans, calcium carbonate precipitates out of solution and settles to the bottom
40
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
41
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
42
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
Subduction/Volcanism
Another Component of the Long-Term Carbon Cycle
44
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
45
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
47
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
49
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
50
Oxidation of Buried Organic Carbon
Eventually, buried organic carbon may be exposed by erosion
The carbon is then oxidized to CO2
51
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon (e.g., coal)
52
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon (e.g., coal)
Erosion
53
Oxidation of Buried Organic Carbon
Atmosphere
Buried Carbon
O2
CO2
C
Result: Carbon into atmosphere (CO2)
54
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
55
The Long-Term Carbon Cycle (Diagram)
Atmosphere (CO2)
Ocean (Dissolved CO2)
Biosphere (Organic Carbon)
Carbonates Buried Organic Carbon
Subduction/Volcanism
Silicate-to-Carbonate Conversion
Organic Carbon Burial
Oxidation of Buried Organic Carbon
56
58
Review of Long Term Carbon Cycle
59
Activity
Answer the following questions1. If volcanism was to increase, how would that affect
global temperatures?2. If oxidation of organic carbon was to increase, how
would that affect global temperatures?3. If there was a decline in the silicate to carbonate
process, how would that affect global temps?4. If volcanism was to increase, how would that affect
the rate of oxidation of buried carbon?5. If the earth warmed, how would that affect the
silicate to carbonate conversion process? What kind of feedback would this produce?
If volcanism was to increase over a period of thousands of years, how would this affect atmospheric CO2 levels?
Atmospheric CO2 levels would
1. Increase
2. Decrease
3. Stay the same
4. Are not related to volcanism
If the oxidation of organic carbon was to increase, how would global temperatures respond?
Global temperatures
1. Would increase
2. Would decrease
3. Would stay the same
4. Are not affected by the oxidation of organic carbon
62
If there was a decline in the silicate to carbonate conversion process, how would global temperatures respond?
Global temperatures
1. Would increase
2. Would decrease
3. Would stay the same
4. Are not affected by the silicate to carbonate conversion process
If the silicate to carbonate conversion process was to increase over a period of millions of years, how would this affect volcanism?
Volcanism would
1. Increase
2. Decrease
3. Stay the same
4. Not be affected by the silicate to carbonate conversion process
64
The silicate to carbonate conversion processes would
1. Increase
2. Decrease
3. Remain unchanged
4. Impossible to tell
Imagine that the global temperature were to increase significantly for some reason.
65
How would atmospheric CO2 levels change?
1. Increase
2. Decrease
3. Stay the same
4. Impossible to tell
66
What type of feedback process would this be
1. Positive
2. Negative
3. Neither
4. Both