²³⁰Th-normalized Fluxes of Biogenic Components from the Central Chilean Margin during the Late Quaternary

• HARADA Naomi

  Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology

• KAWAKAMI Hajime

  Mutsu Institute for Oceanography, Japan Agency for Marine-Earth Science and Technology

• FUKUDA Miho

  Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology Graduate School of Life and Environmental Sciences, University of Tsukuba

• MIYASHITA Wataru

  FBR Technology Engineering Services Company

• MATSUMOTO Takeshi

  Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyu

Bibliographic Information

Other Title

• ²³⁰Thを用いたチリ沖中緯度域における第四紀後期生物起源粒子フラックス変動
• ²³⁰Thを用いたチリ沖中緯度域における第四紀後期生物起源粒子フラックス変動
• ² ³ ⁰ Th オ モチイタ チリオキ チュウ イドイキ ニ オケル ダイシキ コウキ セイブツ キゲン リュウシ フラックス ヘンドウ
• 230Th-normalized Fluxes of Biogenic Components from the Central Chilean Margin during the Late Quaternary

Abstract

 Throughout geologic time, variations of atmospheric CO₂ partial pressures (pCO₂) have been associated with climate change. During glacial periods, increased productivity and an efficient biological pump in the North Pacific, equatorial Pacific, and Southern Oceans may have contributed to low atmospheric pCO₂. Furthermore, changes in global ocean ventilation would have been considered to be among the most effective controllers of variations of atmospheric pCO₂ glacial-interglacial time scale. However, there is still some controversy as to whether ventilation was effective everywhere during glacial periods, and whether intensification of marine productivity resulted in a decrease of atmospheric pCO₂. Resolving this controversy requires more data from many regions regarding temporal changes in past export fluxes of biogenic materials, especially in the upwelling area, where active ocean ventilation and biological production are observed. The aim of this study is to identify changes in the ²³⁰Th-normalized export flux of biogenic components commonly used as proxies for paleoproductivity—namely total organic carbon (TOC), calcium carbonate (CaCO₃), biogenic opal (Si_OPAL), and opal and CaCO₃ ratio (Si_OPAL/CaCO₃)—as recorded in a sediment core from 36°S off the central–south Chilean coast. The ²³⁰Th-normalized fluxes of biogenic components were low from 22,000 to 15,000 calendar years before the present (cal yr BP), indicating reduced primary productivity. From 13,000 to 10,000 cal yr BP, the ²³⁰Th-normalized flux of biogenic components increased, thereafter dropping between 8000 and 5000 cal yr BP, and again increasing slightly in the late Holocene (< 5000 cal yr BP). The changing ²³⁰Th-normalized fluxes of biogenic components are linked to upwelling activity, which was at its maximum during the late deglaciation during the past 22,000 yr. The high fluxes off the central–south Chilean coast might in part be not only due to enhanced coastal upwelling but also related to enhanced upwelling at higher latitudes of the polar frontal zone in the entire Southern Ocean, which would be related to the north-south migration of Southern Westerly Winds.

Journal

• Journal of Geography (Chigaku Zasshi)

  Journal of Geography (Chigaku Zasshi) 121 (3), 555-569, 2012

  Tokyo Geographical Society

Keywords

• central Chilean
• biogenic components
• primary production
• LGM
• last deglaciation
• ²³⁰Th

Details

• CRID: 1390282679213438080
• NII Article ID: 10031146393
• NII Book ID: AN00322536
• DOI: 10.5026/jgeography.121.555
• ISSN: 18840884
• ISSN: 0022135X
• NDL BIB ID: 023869935
• Web Site: https://ndlsearch.ndl.go.jp/books/R000000004-I023869935
• Text Lang: ja
• Data Source:
  • JaLC
  • NDL
  • Crossref
  • CiNii Articles
  • KAKEN
• Abstract License Flag: Disallowed