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Δ14C and Δ13C of Seawater DIC as Tracers of Coastal Upwelling: A 5-Year Time Series from Southern California

Published online by Cambridge University Press:  18 July 2016

Guaciara M Santos ,
Julie Ferguson ,
Karla Acaylar ,
Kathleen R Johnson ,
Sheila Griffin  and
Ellen Druffel
Guaciara M Santos*
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
Julie Ferguson
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
Karla Acaylar
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
Kathleen R Johnson
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
Sheila Griffin
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
Ellen Druffel
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, California 92697-3100, USA.
*
Corresponding author. Email: [email protected].
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Abstract

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Marine radiocarbon (14C) is a widely used tracer of past ocean circulation, but very few high-resolution records have been obtained. Here, we report a time series of carbon isotope abundances of dissolved inorganic carbon (DIC) in surface seawater collected from the Newport Beach pier in Orange County, within the Southern California Bight, from 2005 to 2010. Surface seawater was collected bimonthly and analyzed for Δ14C, δ13C, and salinity. Results from May 2005 to November 2010 show no long-term changes in δ13C DIC values and no consistent variability that can be attributed to upwelling. Δ14C DIC values have lowered from ∼34‰ to about ∼16‰, an 18‰ decrease from the beginning of this project in 2005, and is consistent with the overall 14C depletion from the atmospheric thermonuclear bomb pulse at the end of the 1950s. Δ14C DIC values, paired with salinity, do appear to be suitable indicators of upwelling strength with periods of upwelling characterized by more saline and lower DIC Δ14C values. However, a similar signal was not observed during the strong upwelling event of 2010. These results were obtained in the Southern California Bight where upwelling is fairly weak and there is a complex occanographic circulation in comparison with the remaining western USA coastline. It is therefore likely that the link between DIC Δ14C, salinity, and upwelling would be even stronger at other sites. These data represent the longest time series of Δ14C data from a coastal Southern California site performed to date.

Type
Articles
Information
Radiocarbon , Volume 53 , Issue 4 , 2011 , pp. 669 - 677
Copyright
Copyright © The Arizona Board of Regents on behalf of the University of Arizona 

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