Study on circulation and water mass formation in the intermediate and deep layers of the Okinawa Trough

2013 Fiscal Year Final Research Report

• Project/Area Number: 23540516
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Meteorology/Physical oceanography/Hydrology
• Research Institution: Kagoshima University
• Principal Investigator: NAKAMURA Hirohiko 鹿児島大学, 水産学部, 准教授 (50284914)
• Co-Investigator(Kenkyū-buntansha): NISHINA Ayako 鹿児島大学, 水産学部, 助教 (80311885) ; YAMASHIERO Toru 鹿児島大学, 理工学研究科, 教授 (20158174)
• Project Period (FY): 2011 – 2013
• Keywords: 沖縄トラフ / ケラマギャップ / 北太平洋中層水 / 琉球海流系 / ハイドロリック・コントロール / 鉛直拡散係数 / 湧昇流 / 深層循環

Research Abstract

Circulation and water mass formation in the intermediate and deep layers of the Okinawa Trough were investigated using comprehensive datasets for 1) water properties on the minimum salinity surface mainly derived from Argo float profiles, 2) velocity data in the Kerama Gap measured by moored current-meters from 2009 to 2011, and 3) CTD/LADCP data over the southern Okinawa Trough measured in Junes 2011 and 2013.
Intermediate-water properties are largely modified in the Okinawa Trough due to strong diapycnal diffusion (6.8-21.5 cm2/s based on an advection-diffusion equation). Deep water below the sill depth of the Kerama Gap (~1100 m), is ventilated by the bottom-overflow in the Kerama Gap down to the deepest layer (~2000 m) in the southern Okinawa Trough. A box model predicts that this bottom-overflow (0.18-0.35 Sv) causes strong upwelling in the southern Okinawa Trough, which must be maintained by buoyancy gain of the deep water due to strong diapycnal diffusion (4.8-9.5 cm2/s).

Research Products

• [Journal Article] Observations of flow variability through the Kerama Gap between the East China Sea and the Northwestern Pacific (2014)
  • Author(s): Na, H., M. Wimbush, J.-H. Park, H. Nakamura, and A. Nishina
  • Journal Title: J. Geophys. Res Volume: 119 Pages: 689-703
  • Peer Reviewed
• [Journal Article] Intermediate and Deep Water Formation in the Okinawa Trough (2013)
  • Author(s): Nakamura, H., A. Nishina, Z. Liu, F. Tanaka, M. Wimbush and J.-H. Park
  • Journal Title: J. Geophys. Res Volume: 118 Pages: 6881-6893
  • Peer Reviewed
• [Journal Article] 沖縄トラフの海水循環の物理プロセス研究 (2012)
  • Author(s): 中村啓彦・仁科文子・東政能・内山正樹・幅野明正・市川洋
  • Journal Title: 月刊海洋 Volume: Vol.44, No.12 Pages: 642-647
• [Presentation] 沖縄トラフ南部中深層水塊の形成過程 (2014)
  • Author(s): 仁科文子, 中村啓彦, 朴在勲, 長谷川大介, 日比谷紀之, 田中祐希
  • Organizer: 日本海洋学会春季大会
  • Place of Presentation: 東京海洋大学
  • Year and Date: 2014-03-28
• [Presentation] Deep water formation process in the Okinawa Trough (2014)
  • Author(s): Nishina, A., H. Nakamura, J.-H. Park, D. Hasegawa, T. Hibiya
  • Organizer: The 2014 Ocean Science Meeting
  • Place of Presentation: Honolulu, USA
  • Year and Date: 2014-02-26
• [Presentation] Formation processes of intermediate and deep waters in the Okinawa trough (2013)
  • Author(s): Nakamura, H., A. Nishina, F. Tanaka, Z. Liu, M. Wimbush, and J.-H. Park
  • Organizer: The 17th PAMS (Pacific-Asian Marginal Seas) Meeting
  • Place of Presentation: Hangzhou, China
  • Year and Date: 2013-04-22
• [Presentation] フィリピン海から東シナ海へ流入する中層水の移流経路と変質過程 (2013)
  • Author(s): 田中史代, 中村啓彦, 仁科文子
  • Organizer: 日本海洋学会春季大会
  • Place of Presentation: 東京海洋大学
  • Year and Date: 2013-03-22
• [Presentation] The Influence of Topographic Control on Deep Overflow of the Kerama Gap (2012)
  • Author(s): Liu, Z., H. Nakamura, A. Nishina, J.-H. Park, and, M. Wimbush
  • Organizer: the AGU 2012 Fall Meeting
  • Place of Presentation: San Francisco, USA
  • Year and Date: 2012-12-04
• [Presentation] The Influence of Topographic Control on Deep Overflow of the Kerama Gap (2012)
  • Author(s): Liu, Z., H. Nakamura, A. Nishina, J.-H. Park, and M. Wimbush
  • Organizer: 日本海洋学秋季大会
  • Place of Presentation: 東海大学/清水校舎
  • Year and Date: 2012-09-14
• [Presentation] 沖縄トラフの海洋物理プロセス研究の紹介と将来展開 (2012)
  • Author(s): 中村啓彦, 仁科文子
  • Organizer: 東京大学海洋研究所共同利用研究集会 「アルゴ時代の海洋物理船舶観測」
  • Place of Presentation: 東京大学大気海洋研究所/柏キャンパス
  • Year and Date: 2012-08-02
• [Presentation] Deep Overflow Through the Kerama Gap Connecting the East China Sea and the Philippine Sea (2012)
  • Author(s): Nakamura, H., Z. Liu, A. Nishina, M. Wimbush and J.-H. Park
  • Organizer: The 2012 Ocean Science Meeting
  • Place of Presentation: Salt Lake City, Utah, USA
  • Year and Date: 2012-02-22
• [Presentation] ケラマギャップ通過流の観測 (2011)
  • Author(s): 中村啓彦, 劉昭君, 仁科文子, Mark Wimbush, Jae-Hun Park
  • Organizer: 日本海洋学会秋季大会
  • Place of Presentation: 九州大学/筑紫キャンパス
  • Year and Date: 2011-09-28
• [Remarks]
  • URL: http://www.fish.kagoshima-u.ac.jp/fish/academic/homepage/toppage.html