Toward Regional Characterizations of the Oceanic Internal Wavefield

TL;DR

This paper reanalyzes four decades of oceanographic internal wave data to evaluate the Garrett and Munk spectral model's applicability across different regions and conditions, revealing significant deviations and geographic patterns.

Contribution

It provides a comprehensive regional analysis of the internal wave spectrum, highlighting deviations from the Garrett and Munk model and proposing a framework to interpret variability through generation, propagation, and nonlinearity.

Findings

The Garrett and Munk model describes winter conditions well at Site-D.

Significant deviations from the model are observed elsewhere and at other times.

Geographic patterns influence spectral deviations and their co-variations.

Abstract

Many major oceanographic internal wave observational programs of the last 4 decades are reanalyzed in order to characterize variability of the deep ocean internal wavefield. The observations are discussed in the context of the universal spectral model proposed by Garrett and Munk. The Garrett and Munk model is a good description of wintertime conditions at Site-D on the continental rise north of the Gulf Stream. Elsewhere and at other times, significant deviations in terms of amplitude, separability of the 2-D vertical wavenumber - frequency spectrum, and departure from the model's functional form are noted. Subtle geographic patterns are apparent in deviations from the high frequency and high vertical wavenumber power laws of the Garrett and Munk spectrum. Moreover, such deviations tend to co-vary: whiter frequency spectra are partnered with redder vertical wavenumber spectra. Attempts are made to interpret the variability in terms of the interplay between generation, propagation and nonlinearity using a statistical radiative balance equation. This process frames major questions for future research with the insight that such integrative studies could constrain both observationally and theoretically based interpretations.