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Nitrous Oxide Focus Group Nitrous Oxide Focus Group launch event Friday February 22 nd, 2008 Dr Jan Kaiser Dr Parvadha Suntharalingam The stratospheric.

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Presentation on theme: "Nitrous Oxide Focus Group Nitrous Oxide Focus Group launch event Friday February 22 nd, 2008 Dr Jan Kaiser Dr Parvadha Suntharalingam The stratospheric."— Presentation transcript:

1 Nitrous Oxide Focus Group Nitrous Oxide Focus Group launch event Friday February 22 nd, 2008 Dr Jan Kaiser Dr Parvadha Suntharalingam The stratospheric sink of N 2 O – the impact upon climate change

2 N 2 O mixing ratios in the past Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam N 2 O mixing ratio/parts per billion

3 Atmospheric N 2 O budget: Surface sources (IPCC, 2001) Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

4 photolysis N 2 O + UV light  N 2 + O(90 %) photo-oxidation O 3 + UV light  O 2 + O* N 2 O + O*  2 NO (6 %) N 2 O + O*  N 2 + O 2 (4 %) Atmospheric N 2 O budget: Destruction in the stratosphere Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

5 Catalytic O 3 destruction in the stratosphere Initiation: N 2 O + O*  2 NO Catalytic cycle: NO + O 3  NO 2 + O 2 O 3 + UV light  O 2 + O NO 2 + O  NO + O 2 Net: 2 O 3  3 O 2 Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam N2ON2O UV NO + O3O3 –– – Feedbacks: Catalytic cycle: Cl + O 3  ClO + O 2 O 3 + UV light  O 2 + O ClO + O  Cl + O 2 Net: 2 O 3  3 O 2 Coupling with Cl cycle: NO 2 + ClO  ClNO 3 (WMO, 2007)

6 [ ] Position-dependent N 2 O isotope measurements terminal nitrogen atom: 1  15 N central nitrogen atom: 2  15 N nitrogen average:  15 N oxygen atom:  18 O,  17 O O  NN 1 2 O NN Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

7 Launch of stratospheric balloons Gap, Southern FranceKiruna, Sweden Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

8 Isotope fractionation in the stratosphere Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam (Kaiser et al., 2006) 1  15 N 2  15 N  15 N  18 O ln(remaining N 2 O fraction)

9 Isotope fractionation by N 2 O + O* ln(1+  )/‰ Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam (Kaiser et al., 2002)

10 Contribution of photo-oxidation to total stratospheric N 2 O destruction photolysis photo- oxidation Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam (Kaiser et al., 2006) " 2  15 N/ 1  15 N" N 2 O/ppb

11  15 N/‰  18 O/‰ Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam N 2 O isotope budget (Kaiser, 2002)

12 Oxygen isotope anomalies in atmospheric compounds Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam  N2ON2O

13 O3O3 +UV O*O* O2O2 SO 4 2– CO aerosol NO3NO3 +SO 2 +NO 2 +NO NO2NO2 N2ON2O +NH 2 OHOH +H 2 O H2OH2O +CH 4 CO2CO2 N2O5N2O5 HNO 3 +NO 2 +NO 3 +H 2 O +OH +SO 2 NONO +N 2 O COCO +OH + +C 5 H 8 Spreading of oxygen isotope anomalies in through the atmosphere and climate system Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

14 Summary so far … N 2 O is stable in the lower atmosphere. In the stratosphere, it breaks down to NO and contributes to O 3 destruction. Position-dependent isotope measurements give unique insights into –stratospheric N 2 O loss reactions –N 2 O (isotope) budgets –contributions of different N 2 O sources –mechanisms of enzymatic reactions Oxygen isotope anomalies leave fingerprints of atmospheric processes and indicate, for example, atmospheric nitrate inputs into aqueous and terrestrial ecosystems. Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

15 Numerical modelling of biogeochemical cycles Process-based representation of sources, sinks, cycling CHEMICAL TRANSPORT MODEL Model concentrations Analysis in conjunction with observations IMPROVED KNOWLEDGE OF UNDERLYING PROCESSES Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

16 N 2 O in the surface ocean High concentrations in eastern boundary upwelling regions Arabian Sea Eastern Equatorial Pacific Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam Based on measurements by Weiss et al. 1995

17 Marine N 2 O production Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam NH 4 + NO 3 - N2ON2O N2ON2O Nitrification Denitrification OXYGENATED OCEAN Organic matter oxidation SUB-OXIC OCEAN 1.7 Tg N yr -1 Open Ocean 3.8 Tg N yr –1 Coastal, Rivers, Estuaries IPCC,2007 ATMOSPHERE

18 Marine N 2 O formation depends on oxygen level Anoxic zones Ocean Oxygen Saturation N2O Production Sub-oxic zones Oxic zones Dominant Formation Processes Oxic Zones: Nitrification Sub-oxic Zones: Denitrification Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

19 Modelling the marine nitrous oxide cycle A Global Model of Oceanic N 2 O What are the main factors governing oceanic N 2 O cycling and sea-air flux ? N 2 O production in the oxygenated open ocean (Suntharalingam and Sarmiento, 2000) N 2 O cycling in oceanic sub-oxic zones (Suntharalingam et al. 2000 ) Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

20 Atmospheric N 2 O variations from ice cores Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam NGRIP Ice-core Measurements (Flückiger et al. 2004)  18 O/ ‰ N2ON2O Atmospheric N 2 O varies with climate on a range of timescales (interannual to millenial) These variations result from changes in ocean and land N 2 O fluxes Proxy for Temperature 10,000 years

21 N 2 O fluxes and global change What are the impacts of global change on N 2 O fluxes? Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam SOILS OCEAN N2ON2O N2ON2O CLIMATE CHANGE Changes in : Temperature, Moisture, Meteorology and Ocean circulation ANTHROPOGENIC NITROGEN INPUT Fertiliser, Fossil fuels ? ?

22 N 2 O fluxes and climate feedbacks Are feedbacks between the N 2 O cycle and climate positive or negative ? Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam CLIMATE CHANGE N2ON2O N2ON2O Feedbacks ? Increase ? SOILS OCEAN Reduce ?

23 Climate feedbacks: Soil N 2 O Fluxes CLIMATE + SOILS N 2 O emissions depend on local conditions temperature, soil moisture, organic matter, acidity, oxygen level A POSITIVE feedback suggested by some experimental and model studies Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

24 Climate feedbacks: Ocean N 2 O fluxes CLIMATE ? OCEANS N 2 O fluxes depend on local conditions productivity, oxygen level, temperature INFLUENTIAL FACTORS Changes in Nutrient Supply (e.g., coastal runoff, nitrogen deposition) Changes in Ocean Circulation (e.g., stratification, monsoonal upwelling ) Feedbacks unresolved Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam Affect biological productivity, extent of sub-oxic zones and N 2 O source

25 Impact on marine N 2 O: Nutrient runoff in coastal zones ‘ Dead zones’ of low oxygen Runoff from nitrate and ammonium fertilisers Projections of increasing fertiliser use Implications for global N 2 O fluxes not well quantified Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam Gulf of Mexico

26 Impact on marine N 2 O: Anthropogenic nitrogen deposition Increasing deposition of anthropogenic nitrogen on oceans Stimulates increases in marine productivity Estimated impact on ocean N 2 O fluxes by 2030: Increase of 0.3 Tg N yr –1 Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam Dentener et al. 2006 Yr 2000 Duce et al., Science, in press Anthropogenic Nitrogen Deposition

27 Impact on marine N 2 O: Atmospheric CO 2 induced warming Atm. CO 2 Productivity Ocean N 2 O Flux RESULT FROM A GLOBAL EARTH SYSTEM MODEL L. Bopp, CEA, France CO 2 induced temperature increase Change in ocean circulation (stratification) Decrease in ocean productivity and sub-oxic zones DECREASE in ocean N 2 O emissions 18602060 Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

28 Summary Marine N 2 O formation is sensitive to local environmental conditions, in particular, oxygen concentration and biological productivity. Anthropogenic nitrogen input to the open and coastal ocean is predicted to increase; the implications for the global marine N 2 O source are not well quantified. The overall climate-oceanic N 2 O flux feedback depends on several competing factors. Our present understanding of the net feedback is low. Nitrous Oxide Focus Group: Dr Jan Kaiser, Dr Parvadha Suntharalingam

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