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Seawater Radiocarbon Evolution in the Gulf of Alaska: 2002 Observations

Published online by Cambridge University Press:  18 July 2016

Thomas P Guilderson ,
E Brendan Roark ,
Paul D Quay ,
Sarah R Flood Page  and
Christopher Moy
Thomas P Guilderson*
Affiliation:
Center for Accelerator Mass Spectrometry, LLNL, Livermore, California 94551, USA Department of Ocean Sciences, University of California-Santa Cruz, Santa Cruz, California 94056, USA
E Brendan Roark
Affiliation:
Department of Geography, University of California-Berkeley, Berkeley, California 94720, USA Now at Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
Paul D Quay
Affiliation:
School of Oceanography, University of Washington, Seattle, Washington 98195, USA
Sarah R Flood Page
Affiliation:
Department of Biological Sciences, University of California-Santa Cruz, Santa Cruz, California 94056, USA Now at Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
Christopher Moy
Affiliation:
Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305, USA
*
Corresponding author. Email: [email protected]
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Abstract

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Oceanic uptake and transport of bomb radiocarbon as 14CO2 created by atmospheric nuclear weapons testing in the 1950s and 1960s has been a useful diagnostic for determining the carbon transfer between the ocean and atmosphere. In addition, the distribution of 14C in the ocean can be used as a tracer of oceanic circulation. Results obtained on samples collected in the Gulf of Alaska in the summer of 2002 provide a direct comparison with results in the 1970s during GEOSECS and in the early 1990s during WOCE. The open gyre values are 20–40% lower than those documented in 1991 and 1993 (WOCE), although the general trends as a function of latitude are reproduced. Surface values are still significantly higher than pre-bomb levels (∼ −105% or lower). In the central gyre, we observe Δ14C values that are lower in comparison to GEOSECS (stn 218) and WOCE P16/P17 to a density of ∼26.8 σt. This observation is consistent with the overall decrease in surface Δ14C values and reflects the erosion of the bomb-14C transient. We propose that erosion of the bomb-14C transient is accomplished by entrainment of low-14C water via vertical exchange within the Gulf of Alaska and replenishment of surface and subther-mocline waters with waters derived from the far northwest Pacific.

Type
Articles
Information
Radiocarbon , Volume 48 , Issue 1 , 2006 , pp. 1 - 15
Copyright
Copyright © 2006 by the Arizona Board of Regents on behalf of the University of Arizona 

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