Kinetic Energy of Eddy‐Like Features From Sea Surface Altimetry

Josué Martínez‐Moreno,Adele K Morrison,Andrew Mcc Hogg,Andrew E Kiss,Navid C Constantinou

doi:10.1029/2019ms001769

Josué Martínez‐Moreno, Adele K Morrison + Show 3 more

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https://doi.org/10.1029/2019ms001769

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Abstract

AbstractThe mesoscale eddy field plays a key role in the mixing and transport of physical and biological properties and redistribution of energy 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 in the coherent eddy amplitude and the strengthening of wind stress over the last two decades.

Highlights

Ocean variability is composed largely of mesoscale processes, which include coherent eddies, meandering jets, and waves
We present here a new eddy‐reconstruction algorithm to extract the kinetic energy contained in mesoscale coherent eddies
Our synthetic tests show that the transient eddy kinetic energy (TEKE) is well estimated by TrackEddy and the method is sensitive enough to extract the energy signature contained only by coherent eddies

Summary

Introduction

Ocean variability is composed largely of mesoscale processes, which include coherent eddies, meandering jets, and waves. These mesoscale processes mix and transport tracers such as heat, salt, and biochemicals across ocean basins and redistribute momentum, potential vorticity, and energy (Chelton et al, 2007; Foppert et al, 2017; Zhang et al, 2014; Wyrtki et al, 1976). The contribution of each mesoscale process to kinetic energy (KE) has not been fully explored, which is crucial to further understand the ocean circulation and ocean biology and to improve global ocean numerical models (Beal et al, 2011; Farneti & Delworth, 2010). We will use the term transient kinetic energy (TKE) to refer to the KE of the time‐ varying component: Journal of Advances in Modeling Earth Systems

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