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MET 112 Global Climate Change - Lecture 8 The Carbon Cycle Eugene Cordero San Jose State University Outline Earth system perspective Carbon: what’s the big deal? Carbon: exchanges Long term carbon exchanges 1 MET 112 Global Climate Change 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 2 MET 112 Global Climate Change 3 MET 112 Global Climate Change An Earth System Perspective Earth composed of: – Atmosphere – Hydrosphere – Cryosphere – Land Surfaces – Biosphere These ‘Machines’ run the Earth Holistic view of planet… 5 MET 112 Global Climate Change The Earth’s history can be characterized by different geologic events or eras. 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 MET 112 Global Climate Change 8 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. 10 MET 112 Global Climate Change 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 14 MET 112 Global Climate Change 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) 16 MET 112 Global Climate Change Interactions Between Components of Earth System Hydrologic Cycle (Hydrosphere, Surface,and Atmosphere) – Evaporation from surface puts water vapor into atmosphere – Precipitation transfers water from atmosphere to surface Cryosphere-Hydrosphere – When glaciers and ice sheets shrink, sea level rises – When glaciers and ice sheets grow, sea level falls 18 MET 112 Global Climate Change When ice sheets melt and thus sea levels rise, which components of the earth system are interacting? H ph e yd io s re -B ro s ph e he re -B io s ry o os p tm e re 0% 2% s. .. ... re -C A yd ro s ph e yd ro p re -H he H os p tm A tm os p he re -C ry os p ... 5% 5% ph er Atmosphere-Cryosphere Atmosphere-Hydropshere Hydrosphere-Cryosphere Atmosphere-Biosphere Hydrosphere-Biosphere A 1. 2. 3. 4. 5. 89% When water from lakes and the ocean evaporates, which components of the earth system are interacting? Land Surface – atmosphere Hydrosphere-atmosphere Hydrosphere-land surface Crysophere-Atmosphere Biosphere-Atmosphere 88% 5% 0% 2% ... -A tm os ph er e .. os p ph er e At m io s B C ry s op he re - re -la nd su . .. m os p. ph e ro s yd H H yd ro s ph e – re -a t at m o. .. 5% Su rf ac e nd La 1. 2. 3. 4. 5. The Earth’s history can be characterized by different geologic events or eras. Interactions (cont) 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 23 MET 112 Global Climate Change 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. MET 112 Global Climate Change 25 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 MET 112 Global Climate Change 27 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. 29 MET 112 Global Climate Change The Carbon Cycle The complex series of reactions by which carbon passes through the Earth's – Atmosphere – – Carbon is exchanged in the earth system at all time scales - Short term cycle (from seconds to a few years) 30 MET 112 Global Climate Change 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) 31 MET 112 Global Climate Change 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 decays, 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) 35 MET 112 Global Climate Change 36 MET 112 Global Climate Change 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 38 MET 112 Global Climate Change Short Term Carbon Exchanges In Class Question Explain why CO2 concentrations goes up and down each year Long Term Carbon Cycle 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 43 MET 112 Global Climate Change 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 44 MET 112 Global Climate Change The Long-Term Carbon Cycle (Diagram) Subduction/ Volcanism Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere (Organic Carbon) Silicate-toCarbonate Conversion Carbonates Organic Carbon Burial Oxidation of Buried Organic Carbon Buried Organic Carbon 45 MET 112 Global Climate Change 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) 47 MET 112 Global Climate Change Silicate to carbonate conversion – chemical weathering One component of the long term carbon cycle Granite (A Silicate Rock) 49 MET 112 Global Climate Change Limestone (A Carbonate Rock) 50 MET 112 Global Climate Change 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 52 MET 112 Global Climate Change Silicate-to-Carbonate Conversion Rain 2. Acid Dissolves Silicates (carbonic acid) Land 1. CO2 Dissolves in Rainwater 3. Dissolved Material Transported to Oceans 4. CaCO3 Forms in Ocean and Settles to the Bottom Calcium carbonate MET 112 Global Climate Change 54 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 56 MET 112 Global Climate Change 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 58 MET 112 Global Climate Change 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 61 MET 112 Global Climate Change Volcanic Eruption 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 Mt. Pinatubo (June 15, 1991) 63 MET 112 Global Climate Change 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 66 MET 112 Global Climate Change Organic Carbon Burial Process O2 CO2 Removed by PhotoSynthesis CO2 Put Into Atmosphere by Decay C C Some Carbon escapes oxidation C Result: Carbon into land 68 MET 112 Global Climate Change Oxidation of Buried Organic Carbon Eventually, buried organic carbon may be exposed by erosion The carbon is then oxidized to CO2 69 MET 112 Global Climate Change Oxidation of Buried Organic Carbon Atmosphere Buried Carbon (e.g., coal) 70 MET 112 Global Climate Change Oxidation of Buried Organic Carbon Atmosphere Erosion Buried Carbon (e.g., coal) 71 MET 112 Global Climate Change Oxidation of Buried Organic Carbon Atmosphere CO2 O2 C Buried Carbon Result: Carbon into atmosphere (CO2) 72 MET 112 Global Climate Change 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 74 MET 112 Global Climate Change The Long-Term Carbon Cycle (Diagram) Subduction/ Volcanism Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere (Organic Carbon) Silicate-toCarbonate Conversion Carbonates Organic Carbon Burial Oxidation of Buried Organic Carbon Buried Organic Carbon 76 MET 112 Global Climate Change 77 MET 112 Global Climate Change Review of Long Term Carbon Cycle 79 MET 112 Global Climate Change If volcanism was to increase over a period of thousands of years, how would this affect atmospheric CO2 levels? Atmospheric CO2 levels would Increase Decrease Stay the same Are not related to volcanism 22% e 4% vo l.. el at ed to th e re no tr St ay A . sa m e ea s ec r D re a se 4% In c 1. 2. 3. 4. 69% If the silicate to carbonate conversion process was to increase over a period of millions of years, how would this affect volcanism? Volcanism would 30% ... e th e d by th e N ot b e af fe ct e St ay D ec r ea s sa m e se 13% 13% re a Increase Decrease Stay the same Not be affected by the silicate to carbonate conversion process In c 1. 2. 3. 4. 43% If the oxidation of organic carbon was to increase, how would global temperatures respond? Global temperatures Would increase Would decrease Would stay the same Are not affected by the oxidation of organic carbon A th . by ct ed ffe re no ta ld W ou .. m e sa th e st ay de ld W ou ld in cr cr ea ea s se e 7% 2% 2% W ou 1. 2. 3. 4. 89% If there was a decline in the silicate to carbonate conversion process, how would global temperatures respond? Global temperatures Would increase Would decrease Would stay the same Are not affected by the silicate to carbonate conversion process 17% 13% th e by ct ed ffe ta ld A re no W ou MET 112 Global Climate Change ... m e sa th e st ay de ld W ou ld in cr cr ea ea s se e 4% W ou 1. 2. 3. 4. 65% 83 Activity (groups of two) Imagine that the global temperature were to increase significantly for some reason. 1. How would the silicate-to-carbonate conversion process change during this warming period. Explain. 2. How would this affect atmospheric CO2 levels and as a result, global temperature? 3. What type of feedback process would this be and why (positive or negative)? 84 MET 112 Global Climate Change The silicate to carbonate conversion processes would Increase Decrease Remain unchanged Impossible to tell ll to ge e si bl po s Im un ai n MET 112 Global Climate Change 0% te e ea s ec r R em 0 of 5 0% d 0% D In c re a se 0% ch an 1. 2. 3. 4. Imagine that the global temperature were to increase significantly for some reason. 85 How would atmospheric CO2 levels change? Increase Decrease Stay the same Impossible to tell ll te e si bl po s Im MET 112 Global Climate Change 0% to sa m e ea s St ay 0 of 5 0% e 0% ec r D In c re a se 0% th e 1. 2. 3. 4. 86 How would this affect global temps? Increase Decrease Stay the same Impossible to tell ll te e si bl po s Im MET 112 Global Climate Change 0% to sa m e ea s St ay 0 of 5 0% e 0% ec r D In c re a se 0% th e 1. 2. 3. 4. 87 What type of feedback process would this be Positive Negative Neither Both N MET 112 Global Climate Change ot h er 0% B 0% ei th eg a tiv tiv e Po si 0 of 5 0% e 0% N 1. 2. 3. 4. 88 Effect of Imbalances Imbalances in the long-term carbon cycle can cause slow, but sizeable changes in atmospheric CO2 What would happen? Atmosphere-Ocean-Biosphere Earth’s Crust 91 MET 112 Global Climate Change Consider the long term carbon cycle as seen below Suppose the Atmosphere-Ocean-Biosphere has 40,000 Gt* of carbon and the earth’s crust has 40,000,000 Gt of carbon Atmosphere-Ocean-Biosphere *1 Gt = 1015 grams Earth’s Crust 92 MET 112 Global Climate Change Suppose that an imbalance developed in which the amount leaving the Atm/Ocean/Biosphere was to decrease by 1%. If the arrows represent flux (carbon moving), and flux from the Earth’s crust to the atm/ocean/bio (labeled B) is 0.03Gt/year, what would the flux be for arrow A? Atmosphere-Ocean-Biosphere 40,000 Gt *1 Gt = 1015 grams A B 0.0300 Gt./yr Earth’s Crust 40,000,000 Gt Arrow A would be 0.03 Gt/yr 0.3 Gt/yr 0.0297 Gt/yr 0.0303 Gt/yr r G t/y 03 0. 03 97 0. MET 112 Global Climate Change 0% G t/y t/y r G 3 0. G t/y 03 0. 0 of 5 0% r 0% r 0% 02 1. 2. 3. 4. 94 For such an imbalance as shown below, what is the net carbon flux and in what direction? Atmosphere-Ocean-Biosphere 40,000 Gt 0.0297 Gt./yr A *1 Gt = 1015 grams B 0.0300 Gt./yr Earth’s Crust 40,000,000 Gt 95 MET 112 Global Climate Change For such an imbalance as shown below, what is the net carbon flux and in what direction? 0.033 - up 0.033 down 0.0003 up 0.0003 down MET 112 Global Climate Change 0% w n 0. 00 03 do 03 w n do 0. 03 3 3 03 0. 0 of 5 0% up 0% -u p 0% 0. 00 1. 2. 3. 4. 96 Based on the below Carbon Flux information, how many years will it take for the carbon in the atm/ocean/bio to double? *1 Gt = 1015 grams Atmosphere-Ocean-Biosphere 40,000 Gt Net Carbon Flux 0.0297 Gt./yr A B 0.0300 Gt./yr Earth’s Crust 40,000,000 Gt 0.0003 Gt./yr How many years will it take for the carbon in the atm/ocean/bio to double? 0.03 years 12 years 100,000 years 133 million years ar s ye io n 0 m ill 3 13 10 MET 112 Global Climate Change 0% ye ar s ye 12 ye a 0. 03 0 of 5 0% ar s 0% rs 0% 0, 00 1. 2. 3. 4. 98 Based on the below Carbon Flux information, how many years will it take for the carbon in the atm/ocean/bio to double? Answer: 40, 000/.0003 years = 133 million years *1 Gt = 1015 grams Net Carbon Flux Atmosphere-Ocean-Biosphere 0.0297 Gt./yr A B 0.0300 Gt./yr Earth’s Crust 0.0003 Gt./yr Long-Term CO2 Changes Source: Berner, R. A., The rise of plants and their effect on weathering and atmospheric CO . Science, 276, 544-546. MET 112 Global2Climate Change 100 Time Scale (Continued) The preceding operation would remove 40, 000 Gt. of carbon from the crust; This is only 0.1% of the carbon in the crust Thus, it is perfectly plausible that such an imbalance could be sustained 101 MET 112 Global Climate Change 102 MET 112 Global Climate Change Long-Term Carbon Cycle (Quantitative Assessment) AtmosphereOceanBiosphere Carbon Content: 40, 000 Gt*. Carbon Flux: 0.03 Gt/yr Earth’s Crust Carbon Flux: 0.03 Gt/yr Carbon Content: 40, 000, 000 Gt. *1 Gt = 1015 grams MET 112 Global Climate Change 108