Near-inertial wave propagation between stratified and homogeneous layers: Discussion

22 May 2024


(1) Hans van Haren, NIOZ Royal Netherlands Institute for Sea Research, P.O. Box 59, 1790 AB Den Burg, the Netherlands.

Abstract and Intro



Simulating Transition


Conclusions and References

5 Discussion

As a result, inertial motions, the dominant propagating motions, may initiate similar convective mixing in stratified layers, which is equivalent to slantwise homogeneous, and vertically homogeneous layers, resulting in continuous T-S property variations across the stratification interface (e.g., van Haren and Millot (2009). By the same token, the difference in f-motions in the different layers will be differently polarized, and hence shear will change.

To complicate things further, indications like variations in horizontal current polarization, changing from near-circular to increasingly elliptic, may vary strongly in the vertical, as has been shown in a numerical model (Gerkema and Exarchou, 2008). This may ‘explain’ the observed z,t-variable polarization for near-inertial horizontal motions (Fig. 9). Generally, near-f motions generate most shear because of their short vertical scales in stratified waters, especially in the Mediterranean where tides are also weak, resulting in generation of diapycnal turbulent overturning and mixing. Needless to say that the complex inertial internal wave propagation which is capable of un-attenuated border-crossing between homogeneous and stratified layers, will influence turbulent mixing in the deep. However, more future observational and modelling studies, also from other weakly stratified basins, are wanted for the precise mechanisms of deep-sea mixing that is so relevant for life in the abyss.

This paper is available on arxiv under CC 4.0 license.