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D 17 O proxy for atmospheric chemistry: Towards model interpretation of the ice core record

D 17 O proxy for atmospheric chemistry: Towards model interpretation of the ice core record. Becky Alexander NOAA Postdoctoral Fellow Harvard University. March 25, 2005. Outline.

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D 17 O proxy for atmospheric chemistry: Towards model interpretation of the ice core record

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  1. D17O proxy for atmospheric chemistry: Towards model interpretation of the ice core record Becky Alexander NOAA Postdoctoral Fellow Harvard University March 25, 2005

  2. Outline Atmospheric chemistry and the oxidation capacity of the atmosphere: climate ↔ chemistry Sulfate D17O from the Vostok record GEOS-CHEM D17O simulations Future plans Department of Atmospheric Sciences, University of Washington, Seattle

  3. Oxidizing Power of the Atmosphere OH Primary Emissions DMS, SO2, CH4, … Secondary Species CO2, H2SO4, O3, … Climate change hn, H2O Primary Species H S, SO , CH , CO, 2 2 4 DMS, CO , NO, N O, 2 2 particulates Continental Biomass Marine Volcanoes Biogenics burning Biogenics

  4. LGM Relative to preindustrial Holocene Industrial Era Relative to preindustrial Holocene Model Estimates of Past OH and O3 O3 OH Martinerie et al., 1995 Karol et al., 1995 Thompson et al., 1993

  5. Glacial/Interglacial CH4 variations Wetland CH4 emissions Present day Wetland CH4 emissions 24% less in LGM. Not enough to explain glacial/interglacial change (~50%) in atmospheric CH4 concentrations. LGM Kaplan, 2002

  6. The Vostok Ice Core Record: Aerosols dD from Jouzel et al., 1987 [SO42-] from M. Legrand dD (‰) SO42- (ppb) [SO42-] tracks [MSA-] suggesting a predominant DMS (oceanic biogenic) source (Legrand et al., 1991)

  7. CS2 DMS H2S Sulfur Cycle in the Atmosphere OH, NO3 OH SO2 SO42- O3, H2O2 OH MSA Surface

  8. Radiative Forcing: Greenhouse Gases and Aerosols IPCC report, 2001

  9. Effects of Aerosols on Climate l0 Reflection l0 l0 Absorption Refraction Direct Effect Great Smoky Mountains Visibility: 150 miles Visibility: 15 miles Indirect Effect Cloud droplet number density (cm-3) Aerosol number density (cm-3) Ramanathan et al., 2001

  10. CDNC (m-3) nssSO42- (mg m-3) From Boucher and Lohmann, 1995 New Particle Formation SO2 + OH (+O2 + H2O)  H2SO4(g) (+HO2) Water vapor Updraft velocity Aerosol number density Size distribution Chemical composition HSO3- + H2O2/O3  SO42- Condensation Activation NH3 CCN > ~ 0.1 mm ? H2SO4(g) RCOOH H2O

  11. Mass-Independent Fractionation Mass-Dependent Fractionation O + O2 O3* +D17O Mass-dependent fractionation line: d17O/d18O  0.5 -D17O Thiemens and Heidenreich, 1983 d17O/d18O 1 D17O=d17O– 0.5*d18O 0 d17O Basaltic and sedimentary rocks Air O2 SMOW Rain and cloud water d18O Mass-dependent fractionation line: d17O/d18O  0.5

  12. Source ofD17OSulfate Aqueous Gas SO2 in isotopic equilibrium with H2O : D17Oof SO2 = 0 ‰ 1) SO32-+ O3 (D17O=35‰) SO42-D17O = 8.8 ‰ 2) HSO3-+ H2O2(D17O=1.7‰) SO42-D17O= 0.9 ‰ 3) SO2 + OH(D17O=0‰) SO42-D17O= 0 ‰ D17Oof SO42- a function relative amounts of OH, H2O2, and O3 oxidation Savarinoet al., 2000

  13. Analytical Procedure Decontamination Concentrate Ion Chromatograph Ionic separation SO42- Ag2SO4

  14. Ag2SO4  O2 + SO2 He flow Removable quartz tube magnet To vacuum 1050°C SO2 trap SO2 port vent Sample loop 5A mol.sieve O2 port To vacuum GC Analytical Procedure Isotope Ratio Mass Spectrometer

  15. Vostok Ice Core D17O nssSO42- D17O (‰) DTs DTs data: Kuffey and Vimeux, 2001, Vimeux et al., 2002 Alexander et al., 2002

  16. Climate Variations in the Oxidation Pathways of Sulfate Formation DTs % OH Age (kyr) OH (gas-phase) oxidation greater in glacial period compared to interglacial

  17. Vostok sulfate explanation CCN H2SO4 SO42- OH O3 Transport SO2 Wet and dry deposition OH NO3 DMS Antarctica Ocean

  18. Sulfate Formation Pathways in GEOS-CHEM http://www-as.harvard.edu/chemistry/trop/geos/index.html SO42- pH = 4.5 H2O2, O3 Aqueous-phase Park et al., 2004 OH H2SO4 SO2 Gas-phase OH NO3 DMS

  19. pH dependency of O3 oxidation and its effect on D17O of SO42- H2O2 O3 Lee et al., 2001

  20. GEOS-CHEM D17O Sulfate Simulation Assume constant, global D17O value for oxidants SO2 + OH (gas-phase) D17O=0‰ S(IV) + H2O2 (in-cloud) D17O=0.9‰ S(IV) + O3 (in-cloud) D17O=8.8‰

  21. HSO3-, H2O2, O3 0.0‰ 2.3‰ 4.6‰ D17O sulfate: GEOS-CHEM 8 6 D17O sulfate (‰) 4 January 2001 2 0 0 1 2 3 4 H2O2 (ppbv) July 2001

  22. D17O sulfate: GEOS-CHEM and measurements Whiteface Mtn, NY fogwater 0.3 ‰ Davis, CA fogwater 4.3 ‰ Site A, Greenland ice core 0.5-3‰ La Jolla aerosol 0.2-1.4‰ White Mtn, CA aerosol 1-1.7‰ La Jolla rainwater 1.1 ‰ INDOEX aerosol 0.5-3‰ Desert dust traps 0.3-3.5‰ South Pole aerosol 0.8-2‰ Vostok & Dome C ice cores 1.3-4.8‰ 0.0‰ 2.3‰ 4.6‰ Alert 1.0‰ January 2001 July 2001

  23. H+ + HCO3- H2O•CO2 Acids: H2SO4(g) HNO3(g) RCOOH(g) SO2(g)  SO42- Na+, Cl-, HCO3-/CO32- pH=8 O3 CO2(g) Alkalinity in the Marine Boundary Layer

  24. Subsidence other aerosols (acid or neutral) NH3(g) RCOOH(g) HNO3(g) Sea-salt aerosol HCO3-/CO32- O3 Deposition CO2(g) Emission GEOS-CHEM Sea-salt Alkalinity http://www-as.harvard.edu/chemistry/trop/geos/index.html Free troposphere Marine Boundary Layer Subsidence Cloud SO42- H2O2 H2SO4(g) OH SO2 OH NO3 DMS Emission

  25. January 1997 March 1998 High volume air sampler Na+ [mg m-3] 0 1 3 5 7 9 11 13 INDOEX Cruises GEOS-CHEM Sea-Salt Pre-INDOEX Jan. 1997 INDOEX March 1998

  26. Pre-INDOEX Cruise January 1997 Alexander et al., 2005

  27. INDOEX Cruise March 1998 Alexander et al., 2005

  28. fSO2 fHNO3 fexcess 0.1 0.3 0.5 0.7 GEOS-CHEM Alkalinity Budget

  29. [SO2] % decrease [SO42-] % increase SO2 + OH % decrease 10 30 50 70 5 GEOS-CHEM Sulfur Budget Marine DMS and Climate Charleson et al., 1987; Shaw 1985

  30. 6.3 ‰ 1.6 3.2 4.7 0.0 GEOS-CHEM: Seasonal Variability in D17O Sulfate Alert aerosol 1‰ January July South Pole aerosol 0.8-2‰

  31. Sulfate ng m-3 Arctic Haze Formation Sirois et al., 1999 Picture from L. Barrie

  32. Arctic Measurements Alert (82°N, 85°W) Measurements GEOS-CHEM Measurements: Justin McCabe, UCSD, personal communication

  33. ?? Mn2+, Fe3+ SIV + ½ O2 SVI D17O = 0‰ Arctic Night-time Chemistry From Sirois and Barrie, 1999 xV (ng m-3)

  34. GEOS-CHEM [Fe(III)] = 0.5 mmol/l [Mn(II)] = 0.05 mm/l Measurements GEOS-CHEM [Fe(III)] = 0.5 mmol/l [Mn(II)] = 0.05 mm/l [Fe(III)] = 5.0 mmol/l [Mn(II)] = 0.5 mm/l Measurements Alert: Metal Catalysis? GEOS-CHEM Measurements

  35. Metals: Greenland ice core record GRIP Summit 1773 1992 Candelone et al., 1995 Hong et al., 1996

  36. Conclusions “Minor” oxidants significant in polar regions during winter. Important for interpreting ice core records. Alkaline sea-salt aerosols impact sulfate formation and hence radiative properties of sulfate aerosols.

  37. Oceanic Phytoplankton CO2(g) From Meskhidze et al., 2005 Some Future Directions Dust (Fe) Acids: H2SO4(g) HNO3(g) RCOOH(g) SO2(g)  SO42- Fe, Si, … CaCO3

  38. Some Future Directions NASA GISS general circulation model (GCM) Wetland CH4 emissions (BIOME4) David Rind (Columbia/NASA) Loretta Mickley Shiliang Wu Present day GEOS-CHEM chemical transport model (CTM) LGM Jed Kaplan

  39. Acknowledgements Daniel Jacob Rokjin Park Loretta Mickley Bob Yantosca Mark H. Thiemens Charles C.W. Lee Justin McCabe Joël Savarino Robert Delmas Daly Postdoctoral Fellowship (EPS)

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