[A-OS21] Coastal ocean circulation and material cycle

[AOS21-P01] Numerical simulations of internal tides off the Boso and Joban regions

*Eiji Masunaga¹, Shogo Urakawa², Kei Sakamoto³, Anne Takahashi⁴, Eisuke Tsutsumi⁵, Toshimi Nakajima⁴, Sachihiko Itoh⁴ (1.Ibaraki University, 2.Meteorological Research Institute, 3.Japan Meteorological Agency, 4.The University of Tokyo, 5.Kagoshima University)

Keywords:Internal tides, Numerical simulation, Mixing

This study presents numerical simulations of internal tides in coastal regions off the Boso and Joban areas using a downscaled high-resolution oceanic simulator, MRI.COM. The horizontal resolution is 400 m in the model through double nesting. In order to validate numerical results, we compared model results with mooring data and UCTD observations. Kinetic energy spectrum from the model well agrees with that from the mooring observations in frequency bands around semidiurnal and diurnal. In addition, spatial structures are consistent between the model and the UCTD observations. Internal tide energy budget analysis reveals that internal tide dynamics are different between in the two adjacent regions, the Boso (south) and Joban (north) regions. In the Boso region, internal tides are enhanced by locally generated internal tides (BT-BC conversion) and remotely generated internal tides from the Izu-Ogasawara Ridge. Especially, internal tide energy converges into shelf break (depth ~ 100 – several hundred meters), which results in a band-like energy hotspot region along shelf break isobath. On the other hand, in the north Joban region, local internal tide generation is weak and internal tide energy budgets are explained by remotely generated internal tides propagating into the Joban region. The difference in internal tide generation in the north and south regions is owing to a difference in barotropic tidal currents.