Sensitivity of Internal Wave Energy Distribution over Seabed Corrugations to Adjacent Seabed Features

TL;DR

This paper investigates how the energy distribution of internal gravity waves over seabed ripples is affected by the proximity of adjacent seabed features, revealing complex reflection and interference patterns that influence wave behavior and ocean mixing.

Contribution

It introduces a detailed analysis of internal wave interactions with seabed features considering the effects of neighboring topographies and their impact on energy distribution and wave dynamics.

Findings

Reflections from downstream features cause complex wave interactions.

Energy density can vary by an order of magnitude due to topography placement.

Certain configurations can eliminate seabed ripple signatures in wave fields.

Abstract

Here we show that the distribution of internal gravity waves energy over a patch of seabed corrugations strongly depends on the "distance" of the patch to adjacent seafloor features. Specifically, we consider the energy distribution over a patch of seabed ripples neighbored to i. another patch of ripples, and ii. a vertical wall. Seabed undulations with dominant wavenumber twice as large as overpassing internal waves reflect back part of the energy of the internal waves (Bragg reflection), let the rest of the energy to transmit or to be transferred to higher and lower modes. In the presence of a neighboring topography on the downstream side, the transmitted energy from the patch may reflect back, e.g. partially if the downstream topography is another set of seabed ripples, or fully if it is a vertical wall. The reflected wave from downstream topography is again reflected back by the patch of ripples through the same mechanism. This consecutive reflection goes on indefinitely leading to a complex interaction pattern including constructive and destructive interference of multiply reflected waves as well as an interplay between higher modes internal waves resonated over the topography. We show here that when steady state is reached both the qualitative and quantitative behavior of energy distribution over the patch is a strong function of the "distance" between the patch and the downstream topography. As a result, for instance, the local energy density in the water column can become an order of magnitude larger in certain areas merely based on where the downstream topography is. This may result in the formation of steep waves in specific areas of the ocean, leading to breaking and enhanced mixing. At a right distance, the wall or the second patch may also result in a complete disappearance of the trace of the seabed undulations on the upstream and the downstream wave field.