Remote internal wave forcing of regional ocean simulations near the US West Coast

Low mode internal waves are able to propagate across ocean basins and modulate ocean dynamics thousands of kilometers away from their generation sites. In this study, the impact of remotely generated internal waves on the internal wave energetics near the U.S. West Coast is investigated with realistically forced regional ocean simulations. At the open boundaries, we impose high-frequency oceanic state variables obtained from a global ocean simulation with realistic atmospheric and astronomical tidal forcing. We use the Discrete Fourier Transform (DFT) technique in separating ingoing and outgoing internal tide energy fluxes at the open boundaries in order to quantify internal tide reflections. Although internal tide reflections are reduced with increasing sponge viscosity and/or sponge layer width, reflection coefficients (lambda) can be as high as 73%. In the presence of remote internal waves, the model variance and spatial correlations become more in agreement with both mooring and altimetry datasets. The results confirm that an improved internal wave continuum can be achieved in regional models with remote internal wave forcing at the open boundaries. However, care should be taken to avoid excessive reflections of internal waves from the interior at these boundaries.

Automated summary

This study investigates the impact of remotely generated internal waves on the internal wave energetics near the U.S. West Coast using realistic regional ocean simulations. The results show that internal tide reflections can be as high as 73%, although they are reduced with increased sponge viscosity and/or sponge layer width. The presence of remote internal waves improves the model's variance and spatial correlations, making it more consistent with mooring and altimetry datasets. However, excessive reflections of internal waves from the interior should be avoided at the open boundaries.