The mean age of ocean waters inferred from radiocarbon observations : sensitivity to surface sources and accounting for mixing histories


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dc.contributor.author Gebbie, Geoffrey A.
dc.contributor.author Huybers, Peter
dc.date.accessioned 2012-03-26T17:49:27Z
dc.date.issued 2012-02
dc.identifier.citation Journal of Physical Oceanography 42 (2012): 291–305 en_US
dc.identifier.uri http://hdl.handle.net/1912/5098
dc.description Author Posting. © American Meteorological Society, 2012. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 42 (2012): 291–305, doi:10.1175/JPO-D-11-043.1. en_US
dc.description.abstract A number of previous observational studies have found that the waters of the deep Pacific Ocean have an age, or elapsed time since contact with the surface, of 700–1000 yr. Numerical models suggest ages twice as old. Here, the authors present an inverse framework to determine the mean age and its upper and lower bounds given Global Ocean Data Analysis Project (GLODAP) radiocarbon observations, and they show that the potential range of ages increases with the number of constituents or sources that are included in the analysis. The inversion requires decomposing the World Ocean into source waters, which is obtained here using the total matrix intercomparison (TMI) method at up to 2° × 2° horizontal resolution with 11 113 surface sources. The authors find that the North Pacific at 2500-m depth can be no younger than 1100 yr old, which is older than some previous observational estimates. Accounting for the broadness of surface regions where waters originate leads to a reservoir-age correction of almost 100 yr smaller than would be estimated with a two or three water-mass decomposition and explains some of the discrepancy with previous observational studies. A best estimate of mean age is also presented using the mixing history along circulation pathways. Subject to the caveats that inference of the mixing history would benefit from further observations and that radiocarbon cannot rule out the presence of extremely old waters from exotic sources, the deep North Pacific waters are 1200–1500 yr old, which is more in line with existing numerical model results. en_US
dc.description.sponsorship GG is supported by the J. Lamar Worzel Assistant Scientist Fund and the Penzance Endowed Fund in Support of Assistant Scientists. PJH is supported by NSF Award 0960787. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Meteorological Society en_US
dc.relation.uri http://dx.doi.org/10.1175/JPO-D-11-043.1
dc.subject North Pacific Ocean en_US
dc.subject Mass fluxes/transport en_US
dc.subject Ocean circulation en_US
dc.subject Tracers en_US
dc.subject Optimization en_US
dc.subject Variational analysis en_US
dc.title The mean age of ocean waters inferred from radiocarbon observations : sensitivity to surface sources and accounting for mixing histories en_US
dc.type Article en_US
dc.description.embargo 2012-08-01
dc.identifier.doi 10.1175/JPO-D-11-043.1

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