MET 112 Global Climate Change - Lecture 6 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 MET 112 Global Climate Change

Why are automakers suing California? For regulating emissions of CFCs For limiting number of SUV sales emissions of nitrogen For limiting number of minivan sales. For regulating GHG emissions 41 of 70 MET 112 Global Climate Change

Why is California suing automakers For suing California in the first place For violating emission standards For producing autos that contribute to global warming For producing ozone depleting gases 44 of 70 MET 112 Global Climate Change

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 MET 112 Global Climate Change

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… MET 112 Global Climate Change

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

MET 112 Global Climate Change 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

MET 112 Global Climate Change 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. MET 112 Global Climate Change

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 MET 112 Global Climate Change

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) 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 MET 112 Global Climate Change

45 of 70 When ice sheets melt and thus sea levels rise, which components of the earth system are interacting? Atmosphere-Cryosphere Atmosphere-Hydropshere Hydrosphere-Cryosphere Atmosphere-Biosphere Hydrosphere-Biosphere

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 46 of 70

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

MET 112 Global Climate Change 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 MET 112 Global Climate Change

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

MET 112 Global Climate Change Carbon: where is it? Exists: Atmosphere: CO2 and CH4 (to lesser extent) Living biota (plants/animals) Carbon Soils and Detritus Methane Oceans Dissolved CO2 Most carbon in the deep ocean MET 112 Global Climate Change

MET 112 Global Climate Change 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. MET 112 Global Climate Change

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) MET 112 Global Climate Change

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) 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) Global CO2 MET 112 Global Climate Change

MET 112 Global Climate Change

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) 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 MET 112 Global Climate Change

Short Term Carbon Exchanges

Explain why CO2 concentrations goes up and down each year In Class Question Explain why CO2 concentrations goes up and down each year

Long Term Carbon Cycle

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: MET 112 Global Climate Change

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: Chemical weathering (or called: “silicate to carbonate conversion process”) Volcanism/Subduction Organic carbon burial Oxidation of organic carbon MET 112 Global Climate Change

The Long-Term Carbon Cycle (Diagram) Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere (Organic Carbon) Subduction/Volcanism Oxidation of Buried Organic Carbon Silicate-to-Carbonate Conversion Organic Carbon Burial Carbonates Buried Organic Carbon 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) MET 112 Global Climate Change

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

Granite (A Silicate Rock) MET 112 Global Climate Change

Limestone (A Carbonate Rock) MET 112 Global Climate Change

Silicate-to-Carbonate Conversion Chemical Weathering Phase CO2 + rainwater  carbonic acid Carbonic acid dissolves silicate rock Transport Phase Solution products transported to ocean by rivers Formation Phase In oceans, calcium carbonate precipitates out of solution and settles to the bottom MET 112 Global Climate Change

Silicate-to-Carbonate Conversion Rain 1. 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 Land Calcium carbonate MET 112 Global Climate Change

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 MET 112 Global Climate Change

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 MET 112 Global Climate Change

Subjuction/Volcanism Another Component of the Long-Term Carbon Cycle

MET 112 Global Climate Change 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 MET 112 Global Climate Change

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) 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 MET 112 Global Climate Change

Organic Carbon Burial Process CO2 Removed by Photo-Synthesis CO2 Put Into Atmosphere by Decay C C Some Carbon escapes oxidation C Result: Carbon into land 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 MET 112 Global Climate Change

Oxidation of Buried Organic Carbon Atmosphere Buried Carbon (e.g., coal) MET 112 Global Climate Change

Oxidation of Buried Organic Carbon Atmosphere Erosion Buried Carbon (e.g., coal) MET 112 Global Climate Change

Oxidation of Buried Organic Carbon Atmosphere CO2 O2 C Buried Carbon Result: Carbon into atmosphere (CO2) 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 MET 112 Global Climate Change

The Long-Term Carbon Cycle (Diagram) Atmosphere (CO2) Ocean (Dissolved CO2) Biosphere (Organic Carbon) Subduction/Volcanism Oxidation of Buried Organic Carbon Silicate-to-Carbonate Conversion Organic Carbon Burial Carbonates Buried Organic Carbon MET 112 Global Climate Change

MET 112 Global Climate Change

Review of Long Term Carbon Cycle MET 112 Global Climate Change

Atmospheric CO2 levels would 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 49 of 70

Not be 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 Increase Decrease Stay the same Not be affected by the silicate to carbonate conversion process 49 of 70

Are not affected by the oxidation of organic carbon 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 49 of 70

MET 112 Global Climate Change 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 48 of 70 MET 112 Global Climate Change

Activity (groups of two) Imagine that the global temperature were to increase significantly for some reason. How would the silicate-to-carbonate conversion process change during this warming period. Explain. How would this affect atmospheric CO2 levels and as a result, global temperature? What type of feedback process would this be and why (positive or negative)? Three points for MET 112 Global Climate Change

The silicate to carbonate conversion processes would Imagine that the global temperature were to increase significantly for some reason. Increase Decrease Remain unchanged Impossible to tell 44 of 70 MET 112 Global Climate Change

How would atmospheric CO2 levels change? Increase Decrease Stay the same Impossible to tell 47 of 70 MET 112 Global Climate Change

How would this affect global temps? Increase Decrease Stay the same Impossible to tell 44 of 70 MET 112 Global Climate Change

What type of feedback process would this be Positive Negative Neither Both 49 of 70 MET 112 Global Climate Change

MET 112 Global Climate Change End MET 112 Global Climate Change

Effect of Imbalances Atmosphere-Ocean-Biosphere What would happen? Imbalances in the long-term carbon cycle can cause slow, but sizeable changes in atmospheric CO2 Atmosphere-Ocean-Biosphere What would happen? Earth’s Crust 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 MET 112 Global Climate Change

Atmosphere-Ocean-Biosphere 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 0.0300 Gt./yr A B Earth’s Crust 40,000,000 Gt

MET 112 Global Climate Change Arrow A would be 0.03 Gt/yr 0.3 Gt/yr 0.0297 Gt/yr 0.0303 Gt/yr 0 of 5 MET 112 Global Climate Change

Atmosphere-Ocean-Biosphere 40,000 Gt For such an imbalance as shown below, what is the net carbon flux and in what direction? Atmosphere-Ocean-Biosphere 40,000 Gt *1 Gt = 1015 grams 0.0297 Gt./yr 0.0300 Gt./yr A B Earth’s Crust 40,000,000 Gt MET 112 Global Climate Change

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 0 of 5 MET 112 Global Climate Change

Atmosphere-Ocean-Biosphere 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 0.0300 Gt./yr 0.0003 Gt./yr A B Earth’s Crust 40,000,000 Gt

MET 112 Global Climate Change 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 0 of 5 MET 112 Global Climate Change

Atmosphere-Ocean-Biosphere 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 Atmosphere-Ocean-Biosphere Net Carbon Flux 0.0297 Gt./yr 0.0300 Gt./yr 0.0003 Gt./yr A B Earth’s Crust

MET 112 Global Climate Change Long-Term CO2 Changes Source: Berner, R. A., The rise of plants and their effect on weathering and atmospheric CO2. Science, 276, 544-546. MET 112 Global Climate Change

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 MET 112 Global Climate Change

MET 112 Global Climate Change

Long-Term Carbon Cycle (Quantitative Assessment) Carbon Content: 40, 000 Gt*. Atmosphere-Ocean-Biosphere Carbon Flux: 0.03 Gt/yr Carbon Flux: 0.03 Gt/yr Carbon Content: 40, 000, 000 Gt. Earth’s Crust *1 Gt = 1015 grams MET 112 Global Climate Change