Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan

Michinobu Kuwae, Yuichi Hayami, Hirotaka Oda, Azumi Yamashita, Atsuko Amano, Atsushi Kaneda, Minoru Ikehara, Yoshio Inouchi, Koji Omori, Hidetaka Takeoka, Hodaka Kawahata

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    3 Citations (Scopus)

    Abstract

    To assess abnormal warming of temperature in southwest Japan's coastal seas during the twentieth century, we developed a 200 yr interannually resolved record of planktonic and benthic foraminiferal Mg/Ca-based temperature using neritic coastal sediment cores. The winter to late spring bottom temperature (50 m) record, based on benthic foraminiferal (Nonion japonicum) Mg/Ca ratios in the Bungo Channel (BC), showed consistent variation with observed temperatures on a five-year average basis. The BC bottom temperature record showed a significant increasing trend of 1.5°C /100 yr during the twentieth century, which was never apparent in nineteenth century. That result suggests that our Mg/Ca-based thermometry approach using coastal benthic foraminifera can detect abnormally rising temperatures in neritic coastal seas in southwest Japan. The abnormal warming of winter to late spring bottom temperature in the BC contrasts with the lack of an increasing trend in the Globigerinoides ruber-based summer to autumn temperature for the upper 20 m in the slope region of southwest Japan and the lack of an increasing trend in the steric sea level in the region. These results indicate a warming trend of the neritic coastal ocean in southwest Japan, especially in winter to late spring. The timing of the onset of the prolonged abnormal high-temperature stage, which started in the early twentieth century, suggests a link of the neritic coastal ocean in Japan with human-induced global warming.

    Original languageEnglish
    Pages (from-to)285-294
    Number of pages10
    JournalHolocene
    Volume19
    Issue number2
    DOIs
    Publication statusPublished - 2009 Mar

    Keywords

    • Bungo Channel
    • Foraminiferal Mg/Ca
    • Global ocean warming
    • Neritic coastal sediments
    • Southwest Japan.

    ASJC Scopus subject areas

    • Earth-Surface Processes
    • Global and Planetary Change
    • Ecology
    • Palaeontology

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  • Cite this

    Kuwae, M., Hayami, Y., Oda, H., Yamashita, A., Amano, A., Kaneda, A., Ikehara, M., Inouchi, Y., Omori, K., Takeoka, H., & Kawahata, H. (2009). Using foraminiferal Mg/Ca ratios to detect an ocean-warming trend in the twentieth century from coastal shelf sediments in the Bungo Channel, southwest Japan. Holocene, 19(2), 285-294. https://doi.org/10.1177/0959683608100573