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Atmospheric inversion of CO 2 sources and sinks Northern Hemisphere sink

Atmospheric inversion of CO 2 sources and sinks Northern Hemisphere sink. Jay S. Gregg. Goal. Inverse modeling identifies carbon sources and sinks, and coupled with a planetary transport model, generates predicted CO 2 concentrations.

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Atmospheric inversion of CO 2 sources and sinks Northern Hemisphere sink

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  1. Atmospheric inversion of CO2 sources and sinks Northern Hemisphere sink Jay S. Gregg

  2. Goal Inverse modeling identifies carbon sources and sinks, and coupled with a planetary transport model, generates predicted CO2 concentrations. Ideally, the model is adjusted so that the predicted flux measurements best match those measured at various locations around the globe. Paraphrased from Gurney, 2006, http://www.purdue.edu/eas/carbon/inverse_modeling.html

  3. Components • Observed Atmospheric Concentrations of CO2 • Spatiotemporal concentrations (ppm) of CO2 • Observed Sea Surface Concentrations of CO2 • Partial Pressure of CO2 • General Circulation Model

  4. Sources and Sinks Involved Fossil-Fuel-Based Emissions (Confidence: High) Land Use Change (Confidence: Low) Terrestrial Ecosystem Response to Elevated CO2 (Confidence: Low) Terrestrial Sink (Confidence: Low) Ocean Sink (Confidence: Low) *Confidence refers to amount, temporal pattern, and spatial location

  5. Atmospheric CO2 Observations Geophysical Monitoring for Climate Change (GMCC) Network Based on flask measurements 20 cites since 1980

  6. Atmospheric CO2 Sampling Sites ppm +300 Mountainous Sites (e.g., Mauna Loa) were not used due to difficulty in elevation for the transport models Tans et al., 1990

  7. Atmospheric CO2 Concentration observed concentrations Evidence for missing northern hemisphere sink predicted concentrations from known sources and sinks (b, c, d) Tans et al., 1990

  8. Oceanic Observations Observed pCO2 difference between surface ocean and atmosphere Transect Sampling, some data gaps in Indian and Southern Ocean- extrapolation based on Sea Surface Temperatures Oceans divided into 2o x 2o grids, and mean DpCO2is calculated for the periods (January through April) and (July through October)

  9. Oceanic CO2 Calculations Working Formula for F (CO2 flux across air-sea interface): E: gas transfer coefficient, depends on wind speed Vp: gas transfer piston velocity, depends on turbulence, atmospheric and oceanic S: solubility of CO2 in seawater DpCO2: Sea surface – Atmosphere (>0 is a ocean sink, <0 is an ocean source) Tans et al., 1990

  10. Oceanic CO2 Calculations Transect Samples as of 1972 Tans et al., 1990

  11. Oceanic CO2 Fluxes Largest positive fluxes (sinks) are in the equatorial oceans Largest negative fluxes (sources) are in the Southern gyres Tans et al., 1990

  12. Jan-Apr Oceanic CO2 Fluxes Jul-Oct Tans et al., 1990

  13. Transport Model • 3-D General Circulation Model (GCM) from Goddard Space Flight Center, NASA • Seasonal, diurnal

  14. Transport Model (vs. Observed) Scandinavia Bass Strait observed modeled Tans et al., 1990

  15. Modeled Atmospheric CO2 Concentrations Relative to Global Mean Concentration observed modeled Tans et al., 1990

  16. Modeled Fluxes (C. Roedenbeck et al., 2002)

  17. Modeled Fluxes (C. Roedenbeck et al., 2002)

  18. (C. Roedenbeck et al., 2002)

  19. (C. Roedenbeck et al., 2002)

  20. Modeled NPP arbitrary units (linear) (C. Roedenbeck et al., 2002)

  21. Modeled CO2 Sources and Sinks • Atmospheric CO2 increases about 3 Gt C/yr • Sinks are larger in northern hemisphere than southern • ocean sink is largest at equator • must be a larger northern terrestrial sink • El Nino and La Nina cycles changes fluxes • Still a lot of uncertainty in global carbon cycle

  22. Which Transport Model to Use? • Many different transport models can give different results • Underscores uncertainty in inverse model results • Transcom 3 Project (Gurney, 2002) seeks to compare the outcome from various models

  23. Which Transport Model to Use? Comparison of two transport models, confidence range for all models are in boxes (Gurney et al., 2002)

  24. Which Transport Model to Use? Confidence range for all models based on latitude (Gurney et al., 2002)

  25. Factors in CO2 Flux Variability • El Nino and La Nina (increased biomass burning), changes in NPP • Volcanic Eruptions (e.g., Pinatubo- changes in NPP from sunlight limitations) • Temperature and humidity affect microbial respiration (soil respiration increases at higher temperatures) (C. Roedenbeck et al., 2002)

  26. References I.G. Enting, C.M. Trudinger, R..J.A. Francey (1995) A synthesis inversion of the concentration of d13C of atmospheric CO2. Tellus B47, 35-52. S. Fan, et al., (1998) A large terrestrial carbon sink in North America implied by atmospheric and oceanic carbon dioxide data and models. Science 282, 442-446. K. R. Gurney et al., Towards robust regional estimates of CO2 sources and sinks using atmospheric transport models, Nature 415, 626 (2002). C. Roedenbeck, S. Houweling, M. Gloor, and M. Heimann (2003) CO2 flux history 1982–2001 inferred from atmospheric data using a global inversion of atmospheric transport, Atmos. Chem. Phys., 3, 1919–1964. P. P. Tans, I. Y. Fung, T. Takahashi, (1990) Observational Constraints on the Global Atmospheric CO2 Budget, Science 247, 1431-1438.

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