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Title: Measurements and modeling of contemporary radiocarbon in the stratosphere

Measurements of the 14C content of carbon dioxide in air collected by high-altitude balloon flights in 2003–2005 reveal the contemporary radiocarbon distribution in the northern midlatitude stratosphere, four decades after the Limited Test Ban Treaty restricted atmospheric testing of nuclear weapons. Comparisons with results from a 3-D chemical-transport model show that the 14CO 2 distribution is now largely governed by the altitude/latitude dependence of the natural cosmogenic production rate, stratospheric transport, and propagation into the stratosphere of the decreasing radiocarbon trend in tropospheric CO 2 due to fossil fuel combustion. From the observed correlation of 14CO 2 with N 2O mixing ratios, an annual global mean net flux of 14CO 2 to the troposphere of 1.6(±0.4) × 10 17‰ mol CO 2 yr –1 and a global production rate of 2.2(±0.6) × 10 26 atoms 14C yr –1 are empirically derived. Furthermore, the results also indicate that contemporary 14CO 2 observations provide highly sensitive diagnostics for stratospheric transport and residence times in models.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4] ;  [5] ;  [2]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Univ. of California, Berkeley, CA (United States)
  3. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  4. Univ. of Miami, Miami, FL (United States)
  5. National Center for Atmospheric Research, Boulder, CO (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-677786
Journal ID: ISSN 0094-8276
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 43; Journal Issue: 3; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES
OSTI Identifier:
1357349