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A Study on deep convection related to deep water formation in the Antarctic region

Research Project

Project/Area Number 05402018
Research Category

Grant-in-Aid for General Scientific Research (A)

Allocation TypeSingle-year Grants
Research Field Meteorology/Physical oceanography/Hydrology
Research InstitutionKYOTO UNIVERSITY

Principal Investigator

IMASATO Norihisa  Kyoto Univ., Geophysics, Professor., 大学院・理学研究科, 教授 (40025391)

Co-Investigator(Kenkyū-buntansha) AKITOMO Kazunori  Kyoto Univ., Geophysics, Instructor, 大学院・理学研究科, 助手 (10222530)
AWAJI Toshiyuki  Kyoto Univ., Geophysics, Associate Professor, 大学院・理学研究科, 助教授 (40159512)
Project Period (FY) 1993 – 1995
Project Status Completed (Fiscal Year 1995)
Budget Amount *help
¥24,800,000 (Direct Cost: ¥24,800,000)
Fiscal Year 1995: ¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 1994: ¥5,600,000 (Direct Cost: ¥5,600,000)
Fiscal Year 1993: ¥12,900,000 (Direct Cost: ¥12,900,000)
KeywordsDeep Conuection / Antarctic Ocean / thermobaricity / deep water / Continental shelf slope / Lagrangian transport / 底・深層水形成 / 深い対流(深層対流) / 粘性境界層 / 地衡流調節 / ラグランジュ運動 / 非静水圧モデル / 海水の熱膨張率 / オイラー・ラグランジュの手法 / 非静水圧三次元モデル / ウェッデル海 / 熱膨張率 / ウェッデル深層水
Research Abstract

We have investigated the effect of thermobaricity of sea water on properties of deep convection at high latitudes by the scaling argument and numerical experiments. Thermobaricity is not so effective in a homogeneous ocean. On the contrary, it causes drastic changes in a two-layr ocean which is typical at high latitudes. That is, the water column abruptly overturns when deep convection occurs. The properties of deep convection such as its scale, velocity are proportional to the square root of the difference of potential temperature between the two layrs. From analysis of observatinal data, the two-layr type of deep convection can occur in the Antarctic region whreas the homogeneous-ocean type in the Greenland seas. The effect of wind on the onset of deep convection has been also investigated. The onset is explained by the linear stability theory and after then deep convection occurs intermittently.
Next, we have investigated the other type of deep convection flowing down along a continental shelf slope. Dense water flows maimly in the bottom Ekman layr and its volume transport is determined not only by the pressure gradient due to density deviation but also by the surface pressure gradient induced by the geostrophic adjustment against the depth-mean current flowing along the isobaths. When these two pressure gradients are in opposite direction and comparable to each other, the significant oscillation occurs in the vertical two-dimensional experiment, and the instability in the three-dimensional experiment. Associated with such flow variations, the descending dense water effectively entrains the interior water above the slope to become bottom and deep waters.

Report

(4 results)
  • 1995 Annual Research Report   Final Research Report Summary
  • 1994 Annual Research Report
  • 1993 Annual Research Report
  • Research Products

    (8 results)

All Other

All Publications (8 results)

  • [Publications] 秋友和典: "南極海域におけるDeep convection" 月刊海洋. 25. 555-560 (1993)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] 秋友和典、田中潔、淡路敏之、今里哲久、奥田節夫: "淡水湖における深い対流" 月刊海洋号外. 6. 161-166 (1994)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K., T. Awaji, N. Iwasato: "Opeu-ocean deep convection in the Weddell Sea" Deep-Sea Research. 42. 53-73 (1995)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K., K. Tanaka T. Awaji, N. Imasato: "Deep convection in a lake friggered by wind" Journal of Oceanography. 51. 171-185 (1995)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K.: "Deep convection in the Antarctic region." Monthly Kaiyo. 25 (in Japanese). 555-560 (1993)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K., K.Tanaka, T.Awaji, N.Imasato and S.Okuda: "Deep convection in a lake" Monthly Kaiyo. Special issue, 6 (in Japanese). 161-166 (1994)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K., T.Awaji, and N.Imasato: "Open-ocean deep convection in the Weddell Sea : two-dimensional numerical experiments with a nonhydrostatic model" Deep-Sea Res.42. 53-73 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary
  • [Publications] Akitomo, K., K.Tanaka, T.Awaji and N.Imasato: "Deep convection in a lake triggered by wind : two-dimensional numerical experiments with a nonhydrostatic model" J.Oceanogr.51. 171-185 (1995)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      1995 Final Research Report Summary

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Published: 1993-04-01   Modified: 2016-04-21  

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