On the connection between intermittency and dissipation in ocean turbulence

TL;DR

This paper applies multifractal turbulence theory to ocean data, revealing how energy cascade characteristics vary with depth and linking intermittency to dissipation through a log-Poisson model.

Contribution

It introduces an asymmetric log-Poisson model to connect intermittency and dissipation in ocean turbulence, based on in situ measurements.

Findings

Linear dependence of anomalous scaling on velocity gradient exponent varies with depth

Asymmetry in the distribution of singularity exponents is observed at all depths

The energy cascade changes with depth, as interpreted through the model

Abstract

The multifractal theory of turbulence is used to investigate the energy cascade in the Northwestern Atlantic ocean. The statistics of singularity exponents of velocity gradients computed from in situ measurements are used to show that the anomalous scaling of the velocity structure functions at depths between 50 ad 500 m has a linear dependence on the exponent characterizing the strongest velocity gradient, with a slope that decreases with depth. Since the distribution of exponents is asymmetric about the mode at all depths, we use an infinitely divisible asymmetric model of the energy cascade, the log-Poisson model, to derive the functional dependence of the anomalous scaling with dissipation. Using this model we can interpret the vertical change of the linear slope as a change in the energy cascade.