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Stratosphere

The global bomb 14 C cycle. Stratosphere. nuclear bombs. nuclear bombs. stratosphere-troposphere exchange (STE). Troposphere. air-sea gas exchange. carbon exchange biosphere-atmosphere. Ocean. Biosphere. 30km. ATMOSPHERE. 21km. 15km. 9km. 0km. 90°S. 60°S. 30°S. 0°.

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Stratosphere

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  1. The global bomb 14C cycle Stratosphere nuclear bombs nuclear bombs stratosphere-troposphere exchange (STE) Troposphere air-sea gas exchange carbon exchange biosphere-atmosphere Ocean Biosphere

  2. 30km ATMOSPHERE 21km 15km 9km 0km 90°S 60°S 30°S 0° 30°N 60°N 90°N BIOSPHERE OCEAN Leaves Twigs Wood Soil Setup of the 14C model bomb 14C 14C from nuclear industry natural 14C Land use change CO2 Fossil fuel & cement production CO2

  3. Transfer of bomb 14C from atmosphere to ocean and biosphere

  4. Transfer of bomb 14C from atmosphere to ocean and biosphere

  5. Transfer of bomb 14C from atmosphere to ocean and biosphere

  6. Transfer of bomb 14C from atmosphere to ocean and biosphere

  7. Transfer of bomb 14C from atmosphere to ocean and biosphere

  8. Closing the global bomb 14C budget: difficulties to face (until ~2000) • bomb 14C production: large uncertainties • atmospheric models: not calibrated, • low resolution • observed bomb 14C inventories: • stratosphere (1955-1970) biased? • ocean (GEOSECS in 1970s) large spread • biosphere not available

  9. Global bomb radiocarbon budget

  10. Observation-based bomb 14C inventories

  11. Observed zonal profiles of ocean surface D14C data from Broecker et al., Key et al., Levin & Hesshaimer

  12. Ocean surface D14C zonal profile

  13. Tritium 1 Tritium Unit (TU) = [T/H] = 10-18 Natural production of tritium is 5 TU/yr from interaction of cosmic rays in upper atmosphere with N: 14N + n → 15N → 12C + 3H, 3H → 3He + -β Human production: nuclear bomb testing 1952- 1970s Peak in 1963 with highest monthly of 10,000 TU Half life of 12.3 years so for 1963 Ottawa 2900 TU 1963 - 100; 1975 - 50%; 1988 - 25%; 2000 - 12.5%; 2012 - 6.3%

  14. Tritium nowhere • Tritium is unstable, with half-life of 12.32 years • thus none naturally available • Can make it by bombarding 6Li with neutrons • extra n in D-T reaction can be used for this, if reaction core is surrounded by “lithium blanket” • Lithium on land in U.S. would limit D-T to a hundred years or so • maybe a few thousand if we get lithium from ocean • D-D reaction requires higher temperature, but could be sustained for many millennia

  15. Chlorofluorocarbons

  16. Example: CFC simulations in a ¼ degree model Integrated CFC content below 2000m Year = 1980 PhD project: Alex Sen Gupta

  17. Integrated CFC content below 2000m Year = 2000 PhD project: Alex Sen Gupta

  18. Integrated CFC content below 2000m Year = 2020 PhD project: Alex Sen Gupta

  19. Integrated CFC content below 2000m Year = 2040 PhD project: Alex Sen Gupta

  20. THE END

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