Impacts of ocean current\u2013atmosphere interactions on mesoscale eddy energetics in the Kuroshio extension region

Xuan Shan,Bingrong Sun,Lixin Wu,Zhao Jing

doi:10.1186/s40562-020-00152-w

Xuan Shan, Bingrong Sun + Show 2 more

Open Access

https://doi.org/10.1186/s40562-020-00152-w

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Abstract

The surface ocean current’s imprint on the wind stress (known as the current feedback) has a significant influence on the wind power input to the ocean. In this study, we investigate the effect of the current feedback on mesoscale eddy energetics in the Kuroshio extension region using a high-resolution (9 km) coupled regional climate model. We perform three sets of simulations: one calculates the wind stress without the surface current, one includes only the mesoscale eddy’s current and another includes the entire current in the computation. In this way, the mesoscale eddy’s current feedback can be isolated and its contribution to the entire current feedback can be assessed. The simulation results show that the mesoscale eddy’s current feedback results in negative wind power input to mesoscale eddies and reduces the surface eddy kinetic energy (EKE) by ~ 20% in the Kuroshio extension region. This negative wind power is compensated primarily by the enhanced conversion from mean flow kinetic energy (MKE) and eddy potential energy (EPE) to EKE and secondarily by the reduced pressure flux divergence and horizontal dissipation. Compared to the mesoscale eddy’s current feedback, the entire current feedback has a similar impact on EKE and the wind power on mesoscale eddies, while it affects the EKE budget differently. It weakens the MKE to EKE conversion partly due to the reduced kinetic energy input to background flows by wind. Correspondingly, the negative wind power on mesoscale eddies is primarily compensated by the enhanced EPE to EKE conversion.

Highlights

Ocean mesoscale eddies interact strongly with the overlying atmosphere
The simulation results of Coupled Regional Climate Model (CRCM) and ECCO2 are generally consistent with each other. Both are featured by high eddy kinetic energy (EKE) values along the Kuroshio extension, there is an acceptable northward displacement of the Kuroshio extension in CRCM that is a common problem for regional modeling (e.g., Kang 2008; Seo et al 2010)
Consistent with the findings reported by Seo et al (2016), the mesoscale eddy’s current feedback is the main factor resulting in the EKE reduction, as evidenced by the similar EKE values in noUtot and noUe

Summary

Introduction

Ocean mesoscale eddies interact strongly with the overlying atmosphere. The impact of such interactions on eddies themselves has been extensively analyzed in the past decade. Plenty of literatures using both observations and model simulations reveal that the current feedback reduces the wind power input to the ocean by 20–35% (e.g., Dawe and Thompson 2006; Duhaut and Straub 2006; Zhai and Greatbatch 2007; Hughes and Wilson 2008; Xu and Scott 2008). This reduction is attributed to the decreased positive wind power input to large-scale background flows and the negative wind power input to mesoscale eddies, with the latter more dominant (e.g., Xu and Scott 2008; Renault et al 2016; Seo et al 2016)

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