Global M _2 internal tide and its seasonal variability from high resolution ocean circulation and tide modeling

摘要

The present study describes a model simulation, where ocean tide dynamics are simulated simultaneously with the ocean circulation. The model is forced by a lunisolar tidal forcing described by ephemerides and by daily climatological wind stress, heat, and fresh water fluxes. The horizontal resolution is about 0.1 and thus, the model implicitly resolves meso-scale eddies and internal waves. In this model simulation the global M _2 barotropic to baroclinic tidal energy conversion amounts to 1.2 TW. We show global maps of the surface signature of the M _2 baroclinic tide and compare it with an estimate obtained from 19 years of satellite altimeter data. Further, the simulated seasonality in the low mode internal tide field is presented and, as an example, the physical mechanisms causing the non-stationarity of the internal tide generated in Luzon Strait are discussed. In general, this study reveals the impact of inter-annual changes of the solar radiative forcing and wind forced ocean circulation on the generation and propagation of the low mode internal tides. The model is able to simulate non-stationary signals in the internal tide field on global scales which have important implications for future satellite altimeter missions.