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M2 internal tide at the seafloor

With its high-resolution ocean model MPIOM TP6M, the Max Planck Institute for Meteorology has simulated how internal tidal waves are generated by the overflow of barotropic tides over topographic obstacles.

We know the tides as a constant rise and fall of the sea level at the coasts, where we experience two high and two low tides per day. This semidiurnal rhythm of the tides is called the M2 tide by scientists. The rise and fall of sea level is caused by the movement of water column induced by the attraction from the moon.  Where this tidal movement hits obstacles like continental shelves, ocean ridges, and sea mounts, it creates internal waves, with the semidiurnal frequency of the tides. These waves are called internal tides and are the waves with the highest energy in the ocean interior. Their breaking provides an important energy source, and strongly contributes to the mixing in the ocean that keeps the ocean currents running. Resolving internal tides thus is crucial for quantifying the oceanic energy pathways and possible future changes in ocean circulation. Modeling the generation of internal tides wave at the ocean bottom requires a high spatial and temporal model resolution.



The animation shows the M2-internal-tide bottom pressure in a simulation performed with the ocean model MPIOM TP6M at a resolution of 0.1° (10 km)forced with the full lunisolar tidal potential and the 6 hourly NCEP/NCAR reanalysis. As the M2 barotropic tide, a strong semi-diurnal tide, flows over underwater ridges and rises, the M2 internal tide is generated and propagates as internal waves away from the generation sites.

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