サンゴ骨格年輪の<sup>14</sup>C分析による海洋環境研究  [in Japanese] Study of ocean environment by <sup>14</sup>C analysis of annually-banded coral skeletons  [in Japanese]

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Author(s)

    • 三ツ口 丈裕 MITSUGUCHI Takehiro
    • 日本学術振興会科学技術特別研究員|独立行政法人国立環境研究所化学環境研究領域動態化学研究室 Japan Society for the Promotion of Science|National Institute for Environmental Studies

Abstract

Radiocarbon (<sup>14</sup>C) is one of the most important tracers for the global ocean circulation because of its half-life (5,730 years) comparable to the time span taken by surface-ocean water to circulate to the ocean bottom and back (1,000-2,000 years). <sup>14</sup>C is produced naturally in the upper atmosphere, quickly combined with oxygen to form radioactive carbon dioxide (<sup>14</sup>CO<sub>2</sub>), and incorporated into the ocean, soil, vegetation, etc. Since the atmosphere circulates very rapidly, the global distribution of atmospheric <sup>14</sup>C is almost uniform. On the other hand, <sup>14</sup>C concentration in the ocean varies markedly according to depth, region, and water mass because of the timescale of the global ocean circulation (1,000-2,000 years), local water-mass movements, etc. Atmospheric testing of nuclear bombs performed in the latter 1950s and early 1960s increased atmospheric <sup>14</sup>C concentration by 70-100%. The bomb-produced <sup>14</sup>C was incorporated into the surface ocean via air-sea CO<sub>2</sub> exchange, and surface water was greatly enriched in <sup>14</sup>C relative to deeper water. This provided a favorable opportunity to investigate the vertical mixing between surface water and deeper water. Hermatypic corals secrete CaCO<sub>3</sub> skeletons in the tropical/subtropical surface ocean, with some species forming annual growth bands in their skeletons and occasionally growing to form gigantic colonies containing hundreds of years of coral growth. <sup>14</sup>C analysis of annually-banded coral skeletons, which started in the 1970s, has provided a lot of information about past sea-surface <sup>14</sup>C concentration in the tropics and subtropics, contributing to our understanding of vertical mixing and horizontal advection in the ocean. Here, I enunciate the rationale for <sup>14</sup>C analysis of coral annual bands, review the results obtained so far, and discuss the usefulness of this method for the study of ocean environment.

Journal

  • Chikyukagaku

    Chikyukagaku 38(4), 287-301, 2004

    The Geochemical Society of Japan

References:  56

Codes

  • NII Article ID (NAID)
    110008680086
  • NII NACSIS-CAT ID (NCID)
    AN00141280
  • Text Lang
    JPN
  • Article Type
    REV
  • ISSN
    0386-4073
  • NDL Article ID
    7213040
  • NDL Source Classification
    ZM41(科学技術--地球科学)
  • NDL Call No.
    Z15-645
  • Data Source
    CJP  NDL  NII-ELS  J-STAGE 
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