Observations of radiocarbon in CO2 at La Jolla, California, USA 1992-2007

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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 La Jolla, California, USA 1992-2007
Subtitle Analysis of the long-term trend
Author(s) Graven, Heather D.
Guilderson, Thomas P.
Keeling, Ralph F.
Description 14 p.
Journal or Series Title Journal of geophysical research. D, Atmospheres
Volume Number 117
Issue Number 2
Start Page ARTN D02302
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 performed on CO2 sampled at La Jolla, California, USA over 1992-2007. A decreasing trend in Delta C-14 was observed, which averaged -5.5 parts per thousand yr(-1) yet showed significant interannual variability. Contributions to the trend in global tropospheric Delta C-14 by exchanges with the ocean, terrestrial biosphere and stratosphere, by natural and anthropogenic C-14 production and by C-14-free fossil fuel CO2 emissions were estimated using simple models. Dilution by fossil fuel emissions made the strongest contribution to the Delta C-14 trend while oceanic C-14 uptake showed the most significant change between 1992 and 2007, weakening by 70%. Relatively steady positive influences from the stratosphere, terrestrial biosphere and C-14 production moderated the decreasing trend. The most prominent excursion from the average trend occurred when Delta C-14 decreased rapidly in 2000. The rapid decline in Delta C-14 was concurrent with a rapid decline in atmospheric O-2, suggesting a possible cause may be the anomalous ventilation of deep C-14-poor water in the North Pacific Ocean. We additionally find the presence of a 28-month period of oscillation in the Delta C-14 record at La Jolla.
DOI 10.1029/2011JD016533
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-000299702000003
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@article{Grvn2012,
  author = "Graven, Heather D. and Guilderson, Thomas P. and Keeling, Ralph F.",
  title = "{O}bservations of radiocarbon in {C}{O}2 at {L}a {J}olla, {C}alifornia, {U}{S}{A} 1992-2007: {A}nalysis of the long-term trend",
  journal = "Journal of geophysical research. D, Atmospheres",
  year = 2012,
  volume = "117",
  number = "2",
  pages = "ARTN D02302--",
  month = jan,
}


E-Citations record created: Mon, 27 Feb 2012, 11:40:42 CET