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1 MET 12 Global Climate Change - Lecture 7 The Carbon Cycle Shaun Tanner San Jose State University Outline  Earth system perspective  Carbon: what’s.

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Presentation on theme: "1 MET 12 Global Climate Change - Lecture 7 The Carbon Cycle Shaun Tanner San Jose State University Outline  Earth system perspective  Carbon: what’s."— Presentation transcript:

1 1 MET 12 Global Climate Change - Lecture 7 The Carbon Cycle Shaun Tanner San Jose State University Outline  Earth system perspective  Carbon: what’s the big deal?  Carbon: exchanges  Long term carbon exchanges

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9 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 10 An Earth System Perspective  Earth composed of: –Atmosphere –Hydrosphere –Cryosphere –Land Surfaces –Biosphere  These ‘Machines’ run the Earth

11 The Earth’s history can be characterized by different geologic events or eras.

12 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.

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16 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 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

18 18 Carbon conservation  Initial carbon present during Earth’s formation   Carbon is exchanged between different components of Earth System.

19 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 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)

21 Figure 4.13 Global carbon cycle

22 The carbon cycle has different speeds Short Term Carbon Cycle Long Term Carbon Cycle

23 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 CO 2 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 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 CO 2 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 CO 2 levels start to go down (slightly)  During fall: (more respiration)  atmospheric CO 2 levels start to go up (slightly)

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27 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?)

28 CO2 levels are largest in this month 1.Jan 2.May 3.August 4.October

29 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 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

31 Short Term Carbon Exchanges

32 Long Term Carbon Cycle

33 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/Subduction 3.Organic carbon burial 4.Oxidation of organic carbon

34 34 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 (CaCO 3 )  Carbonates are formed by a complex geochemical process called: –Silicate-to-Carbonate Conversion (long term carbon cycle)

35 Silicate to carbonate conversion – chemical weathering One component of the long term carbon cycle

36 36 Granite (A Silicate Rock)

37 37 Limestone (A Carbonate Rock)

38 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 rivers 3.Formation Phase In oceans, calcium carbonate precipitates out of solution and settles to the bottom

39 39 Silicate-to-Carbonate Conversion Rain 1. CO 2 Dissolves in Rainwater 2. Acid Dissolves Silicates 3. Dissolved Material Transported to Oceans 4. Land

40 40 Silicate-to-Carbonate Conversion Rain 1. CO 2 Dissolves in Rainwater 2. Acid Dissolves Silicates ( carbonic acid) 3. Dissolved Material Transported to Oceans 4. CaCO 3 Forms in Ocean and Settles to the Bottom Calcium carbonate Land

41 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 CO 2 in the atmosphere rises, the planet warms. Evaporation increases, thus the flow of carbon into the rock cycle increases removing CO 2 from the atmosphere and lowering the planet’s temperature –Negative feedback

42 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 CO 2 produced is –now “locked up” in the carbonates  On Venus, the silicate-to-carbonate conversion process apparently never took place

43 Subduction/Volcanism Another Component of the Long-Term Carbon Cycle

44 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 CO 2

45 45 Volcanic Eruption Mt. Pinatubo (June 15, 1991) Eruption injected (Mt – megatons) 17 Mt SO 2, 42 Mt CO 2, 3 Mt Cl, 491 Mt H 2 O Can inject large amounts of CO 2 into the atmosphere

46 Organic Carbon Burial/Oxidation of Buried Carbon Another Component of the Long-Term Carbon Cycle

47 47 Buried organic carbon (1)  Living plants remove CO 2 from the atmosphere by the process of –photosynthesis  When dead plants decay, the CO 2 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

48 48 Organic Carbon Burial Process C C O2O2 Some Carbon escapes oxidation C

49 49 Organic Carbon Burial Process CO 2 Removed by Photo- Synthesis CO 2 Put Into Atmosphere by Decay C C O2O2 Some Carbon escapes oxidation C Result: Carbon into land

50 50 Oxidation of Buried Organic Carbon  Eventually, buried organic carbon may be exposed by erosion  The carbon is then oxidized to CO 2

51 51 Oxidation of Buried Organic Carbon Atmosphere Buried Carbon (e.g., coal)

52 52 Oxidation of Buried Organic Carbon Atmosphere Buried Carbon (e.g., coal) Erosion

53 53 Oxidation of Buried Organic Carbon Atmosphere Buried Carbon O2O2 CO 2 C Result: Carbon into atmosphere (CO2)

54 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 55 The Long-Term Carbon Cycle (Diagram) Atmosphere (CO 2 ) Ocean (Dissolved CO 2 ) Biosphere (Organic Carbon) Carbonates Buried Organic Carbon Subduction/ Volcanism Silicate-to- Carbonate Conversion Organic Carbon Burial Oxidation of Buried Organic Carbon

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58 58 Review of Long Term Carbon Cycle

59 59 Activity Answer the following questions 1.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?

60 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

61 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 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

63 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 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 65 How would atmospheric CO2 levels change? 1.Increase 2.Decrease 3.Stay the same 4.Impossible to tell

66 66 What type of feedback process would this be 1.Positive 2.Negative 3.Neither 4.Both


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