Seasonal and Interannual Variability of EAPE in the South China Sea Derived from ECCO2 Data from 1997 to 2019

Qiang Li,Lei Zhou,Lingling Xie

doi:10.3390/w13070926

Abstract

Using Estimating the Circulation and Climate of the Ocean (phase 2, ECCO2) reanalysis products from 1997 to 2019, this study analyzes the spatiotemporal features of the eddy available gravitational potential energy (EAPE) in the South China Sea (SCS). The results indicate that the EAPE accounts for 64% of the total APE in the SCS with the climatological mean. The 2D EAPE distribution images manifest show high-value regions which are generally consistent with the eddy distributions. One region is located around 21° N and west of the Luzon Strait, the second around 17° N and near Luzon Island, and the third off the Vietnam coast. In the region around 21° N and 17° N, both the seasonal variability and the interannual variability associated with the El Niño–Southern Oscillation (ENSO) are significant. Off the Vietnam coast, the EAPE is closely associated with coastal processes which heavily depend on the seasonal monsoon, the El Nino/La Nina events, and the Indian Ocean Dipole (IOD). The results provide new insights into SCS dynamics from the point of view of ocean energy sources.

Highlights

Conservation of energy is a basic physical law that controls ocean circulation
Off the Vietnam coast, the eddy available gravitational potential energy (EAPE) is closely associated with coastal processes which heavily depend on the seasonal monsoon, the El Nino/La Nina events, and the Indian Ocean Dipole (IOD)
This study aims to investigate the spatiotemporal variations of the EAPE in the South China Sea (SCS) using the long-term and high-resolution reanalysis products

Summary

Introduction

Conservation of energy is a basic physical law that controls ocean circulation. Lorenz was a pioneer and established a four-box diagram for the energy budget in the atmosphere which is commonly known as the Lorenz energy cycle. A lot of studies examined energy budgets in ocean contexts [1,2,3,4,5,6,7]; unlike the atmosphere, accumulating evidence indicates that the ocean is not a heat engine [8], i.e., the amplitude of ocean circulation is controlled by the mechanical energy, which is smaller than the surface heat flux into the ocean by a few order of magnitudes. Eddy contribution to the APE, i.e., the eddy APE (EAPE), in open ocean areas has been investigated [12,13,14,15], while estimates of the EAPE are not widespread for marginal seas such as the South China Sea (SCS). This study aims to investigate the spatiotemporal variations of the EAPE in the SCS using the long-term and high-resolution reanalysis products

Objectives

Methods

Results

Discussion

Conclusion