Sea Surface Signature of Internal Tides. Issue 7 (5th April 2019) - Lahaye, Noé
Abstract: The upper ocean is energetic at scales below the Rossby deformation radius owing to the existence of internal waves and submesoscale fronts and vortices. These contribute significantly to energy dissipation, tracer mixing, and exchanges between the ocean surface layer, the ocean interior, and the atmospheric boundary layer. Internal waves and submesoscale motions both undergo strong spatial and seasonal variations, driven by different mechanisms. Here, we investigate the sea surface signature of internal waves and its seasonality using linear wave theory and a high‐resolution realistic simulation. In summer, internal waves are greatly amplified near the surface mostly due to a thin mixed layer bounded by a seasonal pycnocline. This surface amplification is well captured by linear theory, provided that the stratification at the base of the mixed layer is accurately represented. In winter, the superinertial motions are not fully explained by linear theory, reflecting impacts of the more energetic submesoscale motions. Key Points: The sea surface amplification of internal tides and its seasonality are investigated using a high‐resolution realistic model The mechanism is well reproduced by linear theory and exhibits strong sensitivity to stratification at the base of the mixed layer Amplification occurs in summer and has a greater impact on the horizontal kinetic energy than on the sea surface height