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Article contents

Radiocarbon in the Maritime Air and Sea Surface Water of the South China Sea

Published online by Cambridge University Press:  05 December 2018

Pan Gao*
Affiliation:
Key Laboratory for Earth Surface Processes, Department of Geography, Peking University, Beijing 100871, China
Liping Zhou*
Affiliation:
Key Laboratory for Earth Surface Processes, Department of Geography, Peking University, Beijing 100871, China Institute of Ocean Research, Peking University, Beijing 100871, China Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266071, China
Kexin Liu
Affiliation:
Institute of Heavy Ion Physics & State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
Xiaomei Xu
Affiliation:
Keck Carbon Cycle AMS Laboratory, Department of Earth System Science, University of California, Irvine, CA 92697-3100, USA
*
*Corresponding authors. Emails: pangao@pku.edu.cn; lpzhou@pku.edu.cn.
*Corresponding authors. Emails: pangao@pku.edu.cn; lpzhou@pku.edu.cn.

Abstract

Radiocarbon (14C) generated by the thermonuclear tests in the late 1950s to early 1960s has been used as a tracer to study atmospheric and oceanic circulations, carbon exchange between different reservoirs, and fossil fuel emissions. Here we report the first measurements of 14C in atmospheric CO2 of maritime air collected over the South China Sea (SCS) during July 2014. We also present 14C of the dissolved inorganic carbon (DIC) in the sea surface water in the same region. Most of the Δ14C values of the atmospheric CO2 vary in the range of 15.6±1.6‰– 22.0±1.6‰, indicating that the central SCS maritime air is well-mixed and consistent with the clean background air in the Northern Hemisphere. The 14C values of the DIC (DI14C) in the surface seawater vary between 28.3±2.5‰ and 40.6±2.7‰, mainly due to the lateral mixing between the SCS and western Pacific. The average surface seawater DI14C is 15.4 ± 5.1‰ higher than that of the maritime air 14CO2. The reversal of the sea–air Δ14C gradient occurred at ∼2000, marking the start of the upper ocean transferring bomb 14C back to the atmosphere in the SCS.

Type
Research Article
Copyright
© 2018 by the Arizona Board of Regents on behalf of the University of Arizona 

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