Observational study of small low-salinity water masses appearing in the sub-surface layer of the East China Sea off the southwest of Kyushu.

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04063
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 17020:Atmospheric and hydrospheric sciences-related
• Research Institution: Kagoshima University
• Principal Investigator: Nishina Ayako 鹿児島大学, 農水産獣医学域水産学系, 助教 (80311885)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 低塩分水 / 大陸棚 / 黒潮 / 物質循環

Outline of Final Research Achievements

In the sub-surface layer of the northern East China Sea, low-salinity water masses with small spatial scales have occasionally been observed around the Kuroshio front and warm water eddies. Because of their small size, these low-salinity water masses have received little attention until now. In this study, the low-salinity water masses were analyzed using the reanalysis dataset. In addition, oceanographic observations were conducted in the continental shelf slope area southwest of Kyushu. The results showed that there were seasonal and interannual variations in the number of low-salinity water masses and that there were two advection pathways: one along the Kuroshio front and the other along the outer edge of the warm water tongue that developed on the north side of the Kuroshio. The observed low-salinity water masses have an ellipsoid structure with cyclonic rotation, suggesting that careful analysis is necessary to determine the low-salinity water transport.

Free Research Field

海洋物理学

Academic Significance and Societal Importance of the Research Achievements

九州周辺海域は様々な魚種の産卵・育成場となっており，海域の一次生産を支える栄養塩供給の物理プロセスとして乱流鉛直混合が近年注目されているが，水平的に輸送された低塩分水塊による栄養塩供給も考える必要がある。本研究では，再解析データの解析と観測から低塩分水塊の実態を示し，東シナ海大陸棚から九州南方への低塩分水塊の輸送量の見積を試みたものである。