Transcript CarbonCycle
Carbon Cycle Also see Chapter 6 of IPCC 2013 http://www.climatechange2013.org/report/full-report/ Carbon Cycle Carbon Cycle 0.2 Gtonne/year goes into solid earth 0.2 Gt/yr goes into atmosphere from outgassing Today 2012 approximately 10 Gt/yr are put into the atomosphere from Fossil fuel emission Thus natural fluxes from volcanoes and outgassing account for about 2% of the anthropogenic sources. Carbon Cycle 1.6 Gt/yr from deforestation 6.4 Gt/yr from fossil fuel emission (1994) 1.6/8.0=0.20=20% (deforestation accounts for 20 % of total Carbon flux into atmosphere) Biosphere takes up (2.6 Gt /yr more ) carbon than it did in preindustrial times. Biosphere takes up (2.6 Gt /yr more ) carbon than it did in preindustrial times. Preindustrial RR=120 GT/yr Now it is 122.6 Gt/yr RR=Content/lifetime Preindustrial content =597 Gt Now(1994)= 763 Gt 2000-2009 mean land use changes account for about 1.1/8.9=12 % of anthropogenic carbon emissiosn Figure 6.1 IPCC 2013 WG1AR5 The atmosphere contains the least amount of carbon and sediments and rocks contain the most. The ultimate removal of carbon from the climate system is an extremely slow process. In nature this is balanced by the slow injection of carbon into the atmosphere by volcanoes and outgassing near mid ocean ridges. When humans bring carbon in the form of fossil fuels (coal, natural gas, oil) to the surface they rapidly disrupt this balance. The annual cycle of vegetation is dominated by flucuations in the Northern hemisphere. Short Term Carbon Cycle Short Term Carbon Cycle As atmospheric CO2 increases from photosynthesis or combustion, O2 decreases. O2 is presently decreasing faster than atmospheric CO2 is increasing. This indicates the importance of the oceans in removing CO2 from the atmosphere. 13C/12C ratios in atmospheric CO2 are lower for human activity than for natural processes. Seasonal Cycle is driven by Northern Hemisphere Vegetation When the atmospheric carbon dioxide increases plants are growing or decaying? Circle one. When the atmospheric carbon dioxide decreases plants are growing or decaying? Circle one. Seasonal Cycle is driven by Northern Hemisphere Vegetation When the atmospheric carbon dioxide increases plants are growing or decaying? Circle one. When the atmospheric carbon dioxide decreases plants are growing or decaying? Circle one. From www.learner.org/courses/envsci/ Unit 12 Atmospheric carbon dioxide concentrations are strongly correlated with surface temperatures on most time scales. +sunlight The solubility of water increases with decreasing temperature. Positive climate feedback Phytoplankton shell: Diatom (SiO2) Phytoplankton Shell: coccolithophorid (CaCO3 Zooplankton shell: Foraminifer (CaCO3) Zooplankton shell: Radiolarian SiO2 More Ice on continents leaves more 18O in oceans Ocean Biological Pump. Slowly taking Carbon to the seafloor for ultimate burial. Most of this carbon is recycled back to the surface a very small fraction is removed from the ocean into the deep earth. Coastal Zone Color scanner http://earthobservatory.nasa.gov/IOTD/view.php?id=1297 pH 7.0 is neutral (not acidic not alkaline) less than 7.0 is acidic greater than 7.0 is alkaline. pH of 2.0 is highly acidic. Normal rainwater from pristine environments has a pH of around 5.6, acid rain would have a pH of 5.0 or less. Long term Carbon Cycle Draw a causal loop diagram Describing the feedback structure at left. Is this a positive or negative feedback structure? All loops are negative feedbacks It appears that weathering of carbonate rock does not remove CO2 from the climate system. However some of the newly formed CaCO3 IS incorporated into shells and fall to the bottom of the ocean Weather of silicate rock also removes CO2 from the climate system. Outgassing is the release of CO2 via volcanic activity and seafloor spreading. Over the long term (millions of years) the CO2 flux from outgassing is in near balance with the removal of carbon from the subduction of carbonate sediments. CO2 from outgassing and volcanoes contributes about 2% to the total global emissions in 2010. Global temperatures would increase with fast sea floor spreading and decrease with slow sea floor spreading. Small fragmented rocks have much more surface area compared to large rocks and hence weather more easily. 80 % of chemically weathered ions in Amazon come from the Andes. The Andes have been uplifted in the past 20 Million years. Most uplift in the western US region occurred 70 to 45 Myr ago Biomass growth (Lichen) on rocks can enhance the weathering process. The end Ignore the following slides Residence Time Residence Time Source=inflow Removal Rate= outflow Content Content Content Content RR Resident Time lifetime ResponseTime Time Constant Residence Time Source=inflow Removal Rate= outflow At equilibrium (steady state) inflow = outflow Equilibriu m Content Source Resident Time Equilibriu m Content Source* Residence time A lake has an annual average outflow of 5 Mgallons per year (5,000,000 gal/yr) and an annual average content of 10 Mgallons. From this information estimate the residence time for the lake. If the annual mean inflow into the lake increased to 20 Mgallons/yr what would be the new steady state content of the lake? A lake has an annual average outflow of 5 Mgallons per year (5,000,000 gal/yr) and an annual average content of 10 Mgallons. From this information estimate the residence time for the lake. Content RR Resident Time or 10 5 Resident Time 10 Mgal Resident Time 2 yr 5 Mgal/yr If the annual mean inflow into the lake increased to 20 Mgallons/yr what would be the new steady state content of the lake? Steady State Content Source* Residence time =20 Mgal/yr*2 yr=40 Mgal CFC-12 has an atmospheric lifetime of 100 yrs. In the 1980s the emission rate of CFC-12 was 22 ppt/yr. What is the corresponding equilibrium concentration of CFC-12? CFC-12 has an atmospheric lifetime of 100 yrs. In the 1980s the emission rate of CFC-12 was 22 ppt/yr. What is the corresponding equilibrium concentration of CFC-12? Steady State Content Source* Residence time =22 ppt/yr*100yr=2200 ppt Note: the highest CFC -12 concentration level reached was 540 ppt. International agreements to phase out production and use of CFC-12 ( reduce emissions) were able to keep levels down. CFC-12 has an atmospheric lifetime of 100 yrs. In the 1980s the emission rate of CFC-12 was 22 ppt/yr. What emission rate (source) would limit the steady state atmospheric concentration of CFC-12 to 500 ppt? =22 ppt/yr*100yr=2200 ppt CFC-12 has an atmospheric lifetime of 100 yrs. In the 1980s the emission rate of CFC-12 was 22 ppt/yr. What emission rate (source) would limit the steady state atmospheric concentration of CFC-12 to 500 ppt? Steady State Content Source * Residence time or Steady State Concentration 500 ppt Emission source 5 ppt/yr Residence time 100 yr This is less than 25% of the 1980s emission rate. water Porosity: the fraction of rock that is pore space Permeability: the ability of a fluid to be able to flow through a rock formation. Gas, oil, and water are often trapped in porous rock with an impermeable cap. Gas on top, then oil, then water From www.learner.org/courses/envsci/ Unit 1 http://en.wikipedia.org/wiki/File:Hubbert_peak_oil_plot.svg