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Seasonal and Secular Variations of Atmospheric 14Co2 Over the Western Pacific Since 1994

Published online by Cambridge University Press:  18 July 2016

H Kitagawa ,
Hitoshi Mukai ,
Yukihiro Nojiri ,
Yasuyuki Shibata ,
Toshiyuki Kobayashi  and
Tomoko Nojiri
H Kitagawa
Affiliation:
Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8601, Japan. Corresponding author. Email: kitagawa@ihas.nagoya-u.ac.jp
Hitoshi Mukai
Affiliation:
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Yukihiro Nojiri
Affiliation:
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Yasuyuki Shibata
Affiliation:
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Toshiyuki Kobayashi
Affiliation:
National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
Tomoko Nojiri
Affiliation:
Global Environmental Forum, c/o National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
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Abstract

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Air sample collections over the western Pacific have continued since 1992 as a part of Center for Global Environmental Research, National Institute for Environmental Studies (CGER-NIES) global environmental monitoring program. The air samples collected on the Japan-Australia transect made it possible to trace the seasonal and secular 14CO2 variations, as well as an increasing trend of greenhouse gases over the western Pacific. A subset of CO2 samples from latitudes of 10–15°N and 23–28°S were chosen for accelerator mass spectrometry (AMS) 14C analysis using a NIES-TERRA AMS with a 0.3–0.4% precision. These 14CO2 records in maritime air show seasonal variations superimposed on normal exponential decreasing trends with a time constant of about 16 yr. The Δ14C values in the Northern Hemisphere are lower those in the Southern Hemisphere by 3–4 during 1994–2002. The Northern Hemisphere record shows relatively high seasonality (2.3 ± 1.5) as compared with the Southern Hemisphere (1.3 ± 1.2). The maximum values of seasonal cycles appear in late autumn and early winter in the Northern and Southern Hemispheres, respectively. Oscillations of 1–10 yr over the western Pacific are found to correlate possibly with the El Niño/Southern Oscillation (ENSO) events.

Type
Part II
Information
Radiocarbon , Volume 46 , Issue 2: Proceedings of the 18th International Radiocarbon Conference (Part 2 of 2), Conference Editors: Nancy Beavan Athfield, Rodger J Sparks , 2004 , pp. 901 - 910
Copyright
Copyright © The Arizona Board of Regents on behalf of the University of Arizona 

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