Formation conditions for "abyssal oasis" east of Ogasawara Islands

2016 Fiscal Year Final Research Report

• Project/Area Number: 26400468
• 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: Kyushu University
• Principal Investigator: Ichikawa Kaoru 九州大学, 応用力学研究所, 准教授 (40263959)
• Research Collaborator: TANAKA Yuhei 東京都小笠原水産センター, 研究員 ; KOYAMA Yasuhiro NHK, エンタープライズ深海プロジェクト, ディレクター
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 深海漁場 / 内部潮汐 / メカジキ / 漁獲位置分布 / 高分解能数値モデル / 潮流の収束・発散 / 深部音響反射層 / 小笠原諸島

Outline of Final Research Achievements

Biological activities are generally low in the center of the Pacific subtropical gyre where Ogasawara islands locate. But abyssal fishing there is locally quite active, as an "oasis".　Exact abyssal fishing points are newly recorded, and they are found to locate at the edge of propagation areas of internal tides. Significant divergence/convergence of horizontal internal tidal currents are recognized in these areas, and they are confirmed to be related with disappearance/appearance of the deep scattering layers of sound echos. These suggests that zooplankton sinking in the daytime are accumulated at a place by convergence of horizontal internal tidal currents, so that an abyssal fishing point is formed at the point.

Free Research Field

海洋物理学