Kinetic energy of eddy-like features from sea surface altimetry

TL;DR

This paper introduces a new method, TrackEddy, to specifically quantify the kinetic energy of coherent mesoscale eddies from sea surface height data, revealing an increasing trend in the Southern Ocean linked to climate factors.

Contribution

The paper presents a novel eddy-identification algorithm that isolates eddy kinetic energy from other oceanic processes, improving understanding of mesoscale eddy dynamics.

Findings

Detected an increasing trend of eddy kinetic energy in the Southern Ocean.

Linked eddy energy increase to stronger wind stress and eddy amplitude growth.

Validated the method with synthetic data and applied it to satellite observations.

Abstract

The mesoscale eddy field plays a key role in the mixing and transport of physical and biological properties and redistribute energy budgets in the ocean. Eddy kinetic energy is commonly defined as the kinetic energy of the time-varying component of the velocity field. However, this definition contains all processes that vary in time, including coherent mesoscale eddies, jets, waves, and large-scale motions. The focus of this paper is on the eddy kinetic energy contained in coherent mesoscale eddies. We present a new method to decompose eddy kinetic energy into oceanic processes. The proposed method uses a new eddy-identification algorithm (TrackEddy). This algorithm is based on the premise that the sea level signature of a coherent eddy can be approximated as a Gaussian feature. The eddy Gaussian signature then allows for the calculation of kinetic energy of the eddy field through the geostrophic approximation. TrackEddy has been validated using synthetic sea surface height data, and then used to investigate trends of eddy kinetic energy in the Southern Ocean using Satellite Sea Surface Height anomaly (AVISO+). We detect an increasing trend of eddy kinetic energy associated with mesoscale eddies in the Southern Ocean. This trend is correlated with an increase of the coherent eddy amplitude and the strengthening of wind stress over the last two decades.