Changing controls on oceanic radiocarbon

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Author(s) Graven, H. D., Gruber, N., Key, R., Khatiwala, S., Giraud, X.
Publication Type Journal Items, Publication Status: Published
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Title Changing controls on oceanic radiocarbon
Subtitle New insights on shallow-to-deep ocean exchange and anthropogenic CO2 uptake
Author(s) Graven, H. D.
Gruber, N.
Key, R.
Khatiwala, S.
Giraud, X.
Description 16 p.
Journal or Series Title Journal of Geophysical Research-Oceans
Volume Number 117
Start Page C10005
ISSN 0148-0227
Publisher American Geophysical Union
Publication Place Washington, DC
Publication Date 2012-10
Abstract The injection of radiocarbon (C-14) into the atmosphere by nuclear weapons testing in the 1950s and 1960s has provided a powerful tracer to investigate ocean physical and chemical processes. While the oceanic uptake of bomb-derived C-14 was primarily controlled by air-sea exchange in the early decades after the bomb spike, we demonstrate that changes in oceanic C-14 are now primarily controlled by shallow-to-deep ocean exchange, i.e., the same mechanism that governs anthropogenic CO2 uptake. This is a result of accumulated bomb C-14 uptake that has rapidly decreased the air-sea gradient of C-14/C (Delta C-14) and shifted the main reservoir of bomb C-14 from the atmosphere to the upper ocean. The air-sea Delta C-14 gradient, reduced further by fossil fuel dilution, is now weaker than before weapons testing in most regions. Oceanic C-14, and particularly its temporal change, can now be used to study the oceanic uptake of anthropogenic CO2. We examine observed changes in oceanic Delta C-14 between the WOCE/SAVE (1988-1995) and the CLIVAR (2001-2007) eras and simulations with two ocean general circulation models, the Community Climate System Model (CCSM) and the Estimating the Circulation and Climate of the Ocean Model (ECCO). Observed oceanic Delta C-14 and its changes between the 1980s-90s and 2000s indicate that shallow-to-deep exchange is too efficient in ECCO and too sluggish in CCSM. These findings suggest that mean global oceanic uptake of anthropogenic CO2 between 1990 and 2007 is bounded by the ECCO-based estimate of 2.3 Pg C yr(-1) and the CCSM-based estimate of 1.7 Pg C yr(-1)
DOI 10.1029/2012JC008074
Additional Notes Received 20 March 2012, Accepted 22 August 2012, Published 4 October 2012
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
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NEBIS System Number 004289352
Source Database ID WOS-000309613900001
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@article{Grvn2012,
  author = "Graven, H. D. and Gruber, N. and Key, R. and Khatiwala, S. and Giraud, X.",
  title = "{C}hanging controls on oceanic radiocarbon: {N}ew insights on shallow-to-deep ocean exchange and anthropogenic {C}{O}2 uptake",
  journal = "Journal of Geophysical Research-Oceans",
  year = 2012,
  volume = "117",
  pages = "C10005--",
  month = oct,
}


E-Citations record created: Mon, 12 Nov 2012, 06:39:15 CET