Rough critical topography intensifies internal wave beams

Oceanic internal gravity waves are often generated due to the interaction between barotropic tidal flow with submarine topography. These waves play key roles in ocean mixing and nutrient transport. To understand and estimate the amount of energy converted from barotropic tide to internal gravity waves, previous studies have mainly focused on spatially uniform oscillatory mean flow over smooth, idealized topographies. Subsequently, the dependence of internal wave generation with parameters like criticality, topography height, etc. were investigated. However, the smooth topography assumption may not be very realistic since the ocean's bottom surface is expected to be rough or undulated. Some researchers have reported that the resolution of topography in numerical experiments can impact the generation process and affect the conversion rates. Thus, to study the effects of roughness, we superimpose various small amplitude, sinusoidal wave-like structures on idealized topographies, and quantify the effect of roughness on conversion rates. For example, on superimposing a sinusoidal wave on a model continental shelf with a linear critical slope, the maximum baroclinic horizontal velocity of the internal wave beam was 40% more than the case where undulations were absent.