[A-CG44] 黒潮大蛇行

[ACG44-03] 大蛇行期に黒潮前線域で生成した微細スケール内部擾乱の検出

*小松 幸生^1,2、吉田 聡³、有吉 慶介⁴ (1.東京大学大学院新領域創成科学研究科、2.東京大学大気海洋研究所、3.京都大学防災研究所、4.海洋研究開発機構)

キーワード：内部擾乱、黒潮前線、紀伊半島沖、DONET

The Kuroshio is accompanied by plentiful internal disturbances, which have significant influences on marine productivity through enhancement of both horizontal and vertical mixings. However, generation and development processes of the internal disturbances in the western boundary currents remain to be fully elucidated because of resolution limit of conventional observation methods. Therefore we tried to detect the internal disturbances by using 49 bottom pressure gauges distributed at the sea floor originally for monitoring the hydraulic pressure fluctuations due to submarine earthquakes. In this study, we focused on the region south of Kii Peninsula, Japan, where several oceanic events frequently occur under influences of the Kuroshio and the Dense Ocean floor Network system for Earthquakes and Tsunamis (DONET) has been arranged widely by JAMSTEC. The pressure gauges of DONET can measure fine fluctuations of water pressure at the bottom with an accuracy of 0.01 db, hence in some cases it has a potential to detect signals attributed to disturbances generated in the ocean interior. The trials were conducted in October 2018 and June 2021, when the Kuroshio had continued to take a large meander path since August 2017. Timeseries of the bottom pressure at 0.1 s intervals presented temporal variation identical within the range of 0.16 db to the barotropic fluctuation of the external tide estimated from an astronomical tide model. Cross-spectral analysis of the bottom pressure fluctuations revealed that oceanic disturbances with the period of one hour propagated northeastward from the front of the Kuroshio to the slope water region southeast of Kii P.