Observations of radiocarbon in CO2 at seven global sampling sites in the Scripps flask network

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Author(s) Graven, Heather D., Guilderson, Thomas P., Keeling, Ralph F.
Publication Type Journal Items, Publication Status: Published
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Title Observations of radiocarbon in CO2 at seven global sampling sites in the Scripps flask network
Subtitle Analysis of spatial gradients and seasonal cycles
Author(s) Graven, Heather D.
Guilderson, Thomas P.
Keeling, Ralph F.
Description 16 p.
Journal or Series Title Journal of geophysical research. D, Atmospheres
Volume Number 117
Start Page ARTN D02303
ISSN 0148-0227
Publisher American Geophysical Union
Publication Place Washington, DC
Publication Date 2012-01-25
Abstract High precision measurements of Delta C-14 were conducted for monthly samples of CO2 from seven global stations over 2- to 16-year periods ending in 2007. Mean Delta C-14 over 2005-07 in the Northern Hemisphere was 5 parts per thousand lower than Delta C-14 in the Southern Hemisphere, similar to recent observations from I. Levin. This is a significant shift from 1988-89 when Delta C-14 in the Northern Hemisphere was slightly higher than the South. The influence of fossil fuel CO2 emission and transport was simulated for each of the observation sites by the TM3 atmospheric transport model and compared to other models that participated in the Transcom 3 Experiment. The simulated interhemispheric gradient caused by fossil fuel CO2 emissions was nearly the same in both 1988-89 and 2005-07, due to compensating effects from rising emissions and decreasing sensitivity of Delta C-14 to fossil fuel CO2. The observed 5 parts per thousand shift must therefore have been caused by non-fossil influences, most likely due to changes in the air-sea C-14 flux in the Southern Ocean. Seasonal cycles with higher Delta C-14 in summer or fall were evident at most stations, with largest amplitudes observed at Point Barrow (71 degrees N) and La Jolla (32 degrees N). Fossil fuel emissions do not account for the seasonal cycles of Delta C-14 in either hemisphere, indicating strong contributions from non-fossil influences, most likely from stratosphere-troposphere exchange.
DOI 10.1029/2011JD016535
Additional Notes Received 11 July 2011, Accepted 16 November 2011
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
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NEBIS System Number 004289357
Source Database ID WOS-000299702000004
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  author = "Graven, Heather D. and Guilderson, Thomas P. and Keeling, Ralph F.",
  title = "{O}bservations of radiocarbon in {C}{O}2 at seven global sampling sites in the {S}cripps flask network: {A}nalysis of spatial gradients and seasonal cycles",
  journal = "Journal of geophysical research. D, Atmospheres",
  year = 2012,
  volume = "117",
  pages = "ARTN D02303--",
  month = jan,

E-Citations record created: Mon, 27 Feb 2012, 11:40:39 CET