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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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Presentation Transcript

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


30km

ATMOSPHERE

21km

15km

9km

0km

90°S

60°S

30°S

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


Transfer of bomb 14C from atmosphere to ocean and biosphere


Transfer of bomb 14C from atmosphere to ocean and biosphere


Transfer of bomb 14C from atmosphere to ocean and biosphere


Transfer of bomb 14C from atmosphere to ocean and biosphere


Transfer of bomb 14C from atmosphere to ocean and biosphere


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



Observation-based bomb 14C inventories


Observed zonal profiles of ocean surface D14C

data from Broecker et al., Key et al., Levin & Hesshaimer


Ocean surface D14C zonal profile


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%


Tritium nowhere
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



Example: CFC simulations in a ¼ degree model

Integrated CFC content below 2000m

Year = 1980

PhD project: Alex Sen Gupta


Integrated CFC content below 2000m

Year = 2000

PhD project: Alex Sen Gupta


Integrated CFC content below 2000m

Year = 2020

PhD project: Alex Sen Gupta


Integrated CFC content below 2000m

Year = 2040

PhD project: Alex Sen Gupta



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