Marine Hydrology

Analysis of horizontal stirring in the South China Sea derived from satellite altimeter data

  • LI Wei-jie ,
  • ZHAN Hai-gang
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  • 1. State Key Laboratory of Tropical Oceanography (South China Sea Institute of Oceanology, Chinese Academy of Sciences), Guangzhou 510301, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China;

Received date: 2013-04-15

  Revised date: 2013-05-28

  Online published: 2014-04-02

Abstract

Stirring is an important part of mixing, which can be quantified using Finite Time Lyapunov Exponents (FTLE) based on Lagrangian view. In this paper, we calculated the FTLE of surface ocean derived from satellite altimeter from 2002 to 2011, and then analyzed spatial and temporal variation of horizontal stirring in the South China Sea (SCS). Results show that FTLE in the SCS is not uniform, with high values southeast of Vietnam indicating strong stirring, and low values in the northwest and southeast of the SCS. A slowly increasing trend of stirring in the SCS is observed during the 10 year period. FTLE also displays a seasonal fluctuation, strong in summer but weak in winter. Furthermore, we found that FTLE has a similar spatial distribution with Euler-based eddy kinetic energy (EKE) and strain rate, with high and low values of these three quantities locating roughly in the same areas. A comparison with Okubo-Weiss parameter reveals a strong relationship between vortices and FTLE ridges, referred to as Lagrangian Coherent Structures (LCS). Low values of FTLE are mainly present inside rotation-dominated vortices, while high values occur in strain-dominated regions surrounding the vortices.

Cite this article

LI Wei-jie , ZHAN Hai-gang . Analysis of horizontal stirring in the South China Sea derived from satellite altimeter data[J]. Journal of Tropical Oceanography, 2014 , 33(2) : 10 -16 . DOI: 10.11978/j.issn.1009-5470.2014.02.002

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