1. Chemistry of polar ice (part II) S & N cycles from ice core studies Robert DELMAS

2. YESTERDAY Chemical information is located in the ice matrix itself Basic features of glaciochemistry -soluble vs insoluble -ion balance Primary aerosol species -Sea salt. May be modified in ice records. Strong interaction with secondary sulfate aerosol -Continental dust: very high in glacial conditions

3. Sulfur cycle at high southern latitudes

4. SULFATE MAJOR COMPONENT OF THE GLOBAL AEROSOL LOAD CLIMATIC ROLE: Direct & indirect DEPOSITED AS AN AEROSOL AFFECTED BY « DRY DEPOSITION » EFFECT Excess-sulfate or nssSO 4 : [nssSO 4 ] = [SO 4 ] - 0.25 [Na]

5. nssSULFATE ORIGINS FOR CENTRAL ANTARCTICA MARINE BIOGENIC ACTIVITY (gaseous DMS emission) together with MSA VOLCANIC ACTIVITY Continuous or sporadic Stratospheric pathway Tropospheric pathway (South America) Antarctic volcanoes In glacial conditions: an additional source (e.g. gypsum: CaSO 4 )? A tool to differentiate origins: S & O isotope measurements

6. About Antarctic nsssulfate… H 2 SO 4 is formed from SO 2 in gaseous or in liquid phase (see next) H 2 SO 4 may be scavenged by sea salt aerosol Are sea salt and sulfate aerosol transported separately or internally mixed?

7. Oxidation ways of SO 2 (investigated by O isotope measurements) 2 Gas-phase: SO 2 + OH  new aerosol particle 1 Heterogeneous phase: SO 2 + O 3 /H 2 O 2  growth of existing aerosol particle, in particular sea salt Alexander, B., J. Savarino, N.I. Barkov, R.J. Delmas, and M.H. Thiemens, 2002 Alexander, B., M.H. Thiemens, J. Farquhar, A.J. Kaufman, J. Savarino, and R.J. Delmas, 2003

8. Two kinds of sulfate in the Antarctic 10 Be is attached to background aerosol

9. Methanesulfonic acid (HCH 3 SO 3 ) Directly derived from DMS Aerosol or gas? Specific tracer of marine biogenic activity (from DMS) Tracer of El Niño events? Ratio MSA/nssSO 4 commonly used Strong post-deposition effect Concentrations generally high in glacial conditions

10. Volcanic sulfate

11. ECM: ElectroConductometric Measurement Sulfuric acid peaks Tambora period (1800-1820) Sulfuric acid peaks

12. Volcanic eruptions recorded at various Antarctic sites South Pole 1964-65 1259 AD

13. Volcanism recorded at Vostok Ash layers 1259 AD eruption: sulfate and fluoride

14. Sulfate in Antarctica

15. Sulfate in Greenland

16. The turn of the century in Greenland

18. Volcanic eruptions in the Northern Hemisphere

19. Sulfate and MSA in Antarctic coastal regions In James Ross Island snow Antarctic Peninsula

20. Seasonal variations in South Pole snow MSA is labile in the upper firn layers

21. MSA at South Pole El Niño events ?

22. MSA: important loss in the upper firn layers VOSTOK

23. MSA is released to the interstitial air but remains stored in the firn layers It is then entrapped again by ice below close-off

24. MSA in Antarctic ice cores Are this data reliable?

25. In Greenland

26. Isotope measurements related to the sulfur cycle S-isotopes in SO 4 O isotopes in SO 4

27. Dronning Maud Land (german core) Depth Years AD

28. Fluctuation of S-isotopic composition over 2 centuries Annual mean

29. Dronning Maud Land Continental source only volcanic A continental source + a volcanic source 18001990

30. NITROGEN CYCLE UP TO NOW, NOT UNDERSTOOD There are two major species in polar ice related to this cycle: NO 3 and NH 4 MAY EXIST in the ATMOSPHERE as a GAS (HNO 3 ) or an AEROSOL VERY COMPLEX TRANSFER FUNCTION for HNO 3 IMPORTANT ENVIRONMENTAL ISSUES like O 3 hole, biomass burning or photochemistry (in-situ production)

31. Strong decrease in upper firn layers

32. During ice ages, nitrate is attached to dust

33. EPICA Dome F Biomass burning? NITRATE IN ANTARCTIC CORES

34. Anthropogenic pollution in Greenland

35. Lead pollution in Greenland

36. N-isotope measurements in NO 3 -

37. Ammonium Samples easily contaminated Extremely weak in central Antarctic snow (<1 ppb) In coastal regions higher concentrations linked to penguins Greenland

38. Carboxylic acids at Summit

39. Conclusions (1) Glaciochemical work is much more sophisticated and difficult than water stable isotope measurements and gas measurements Prioritiy recently given to aerosol research could give a boost to glaciochemistry It can be envisaged to investigate in the future viruses, bacteria, microorganisms … which are attached to aerosol particles, in particular in non- polar regions More ice cores in tropical and mid-latitude mountains to understand continental aerosol and source regions of polar dust

40. Conclusions (2) Glaciochemistry is still a very open domain Processes occurring in firn have to be confirmed in particular for NO 3, Cl and MSA The interaction between sea salt and sulfate aerosol has to be taken into account The role of glacial dust on atmospheric chemistry has to be investigated Na as an indicator of sea ice extent in the past CaNO 3 as a tracer of biomass burning in Antarctica