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Early Bomb Radiocarbon Detected in Palau Archipelago Corals

Published online by Cambridge University Press:  09 February 2016

Danielle Glynn*
Affiliation:
Earth System Science Department, University of California, Irvine, Irvine, California 92697-3100, USA
Ellen Druffel
Affiliation:
Earth System Science Department, University of California, Irvine, Irvine, California 92697-3100, USA
Sheila Griffin
Affiliation:
Earth System Science Department, University of California, Irvine, Irvine, California 92697-3100, USA
Robert Dunbar
Affiliation:
Department of Environmental Earth System Science, Stanford University, Stanford, California 94305-2115, USA
Michael Osborne
Affiliation:
Department of Environmental Earth System Science, Stanford University, Stanford, California 94305-2115, USA
Joan Albert Sanchez-Cabeza
Affiliation:
Instituto de Ciencias del Mar y Limnologia, Universidad Nacional Autónoma de México, 04510 Ciudad de Mexico, Mexico
*
2Corresponding author. Email: dglynn@uci.edu.

Abstract

In order to evaluate the variability in surface water masses in the Western Pacific Warm Pool, we report high-precision radiocarbon measurements in annual and seasonal bands from Pontes lutea corals collected from the Palau Archipelago (7°N, 134°E). Annual coral bands from 1945 to 2008 and seasonal samples from 1953 to 1957 were analyzed to capture the initial early input of bomb 14C from surface thermonuclear weapons testing in the Marshall Islands. Results show a pre-bomb average δ14C value of-54.9% between 1945 and early 1953. Beginning early in 1954, there is a rapid increase to a maximum of-23.1% at the start of 1955. Values continued to rise after 1957 to a post-bomb peak of 141% by 1976. The large initial rise in δ14C cannot be accounted for by air-sea CO2 exchange. Results therefore suggest that the primary cause of this increase is the lateral advection of fallout-contaminated water from the Marshall Islands to Palau via the North Equatorial Current and then to the North Equatorial Countercurrent.

Type
Oceanic Carbon Cycle
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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