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A numerical study of island wakes in the Xisha Archipelago associated with mesoscale eddies in the spring
Zhao, Zhuangming; Li, Junmin1; Zhao, Wenjing; Yang, Jing; Qi, Shibin; Xu, Min
2019
Source PublicationOCEAN MODELLING
ISSN1463-5003
Volume139Pages:UNSP 101406
AbstractEddies caused by island wakes often appear downstream of an island where upwelling currents are coupled with nutrient transport. Several island wake eddies downstream of the Yongle atoll (YA), Huaguang Reef (HR) and Yuzhuo Reef (YR) in the Xisha Archipelago (XA) are found based on SAR and GF-1 satellite images taken on April 14, 2009 and May 30, 2014, respectively. The present study aims to explore the features and mechanisms of spring island wakes based on a high-resolution numerical model as well as satellite data. Our results are: 1) The cyclonic wake eddies (CWEs) are surface-intensified, and introduce a 20 - 40 m uplift of the isopycnal for the most intense eddies; While the anticyclonic wake eddies (AWEs) reach a subsurface maximum at a depth of 25 - 50 m, which leads to the weak isopycnal downwelling. The CWEs are generally more abundant than the AWEs in different radius classes under different incoming flows, which is due to the inertial-centrifugal instability (ICI) of the AWEs. 2) In the XA, lower SST features observed in the downstream side of the reefs demonstrate the presence of current-induced island wakes. In the near wakes of YA, HR and YR, the periodic vorticity generation is mainly caused by shear flow instabilities arising from the side boundaries of the reefs. Anticyclonic vorticity generation is slightly larger than that of the cyclonic for these three reefs. 3) For the submesoscale wake dynamics, the barotropic instability is more significant than the baroclinic in the XA. Strong toroidal vortices of alternating sign, which strongly perturb the density, were observed as the existence of the ICI in the transects of an unstable intense AWE. But these could hardly be found in a weak AWE. The unstable AWEs may have a larger decay of the velocity at their eddy edges and large persistent vorticities at their cores, which lead to an increase of the ratio between the core vorticity and the Rossby number Gamma. While stable AWEs have longer lifetimes with nearly constant Gamma values that are similar to those of the stable CWEs.
DepartmentLTO
KeywordIsland wake Numerical simulation Sub-mesoscale Inertial-centrifugal instability (ICI) Xisha Archipelago (XA)
DOI10.1016/j.ocemod.2019.101406
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Document Type期刊论文
Identifierhttp://ir.scsio.ac.cn/handle/344004/17705
Collection热带海洋环境国家重点实验室(LTO)
Affiliation1.Minist Ecol & Environm PRC, South China Inst Environm Sci, Guangzhou 510655, Guangdong, Peoples R China
2.Chinese Acad Sci, South China Sea Inst Oceanol, State Key Lab Trop Oceanog, Guangzhou 510301, Guangdong, Peoples R China
Recommended Citation
GB/T 7714
Zhao, Zhuangming,Li, Junmin,Zhao, Wenjing,et al. A numerical study of island wakes in the Xisha Archipelago associated with mesoscale eddies in the spring[J]. OCEAN MODELLING,2019,139:UNSP 101406.
APA Zhao, Zhuangming,Li, Junmin,Zhao, Wenjing,Yang, Jing,Qi, Shibin,&Xu, Min.(2019).A numerical study of island wakes in the Xisha Archipelago associated with mesoscale eddies in the spring.OCEAN MODELLING,139,UNSP 101406.
MLA Zhao, Zhuangming,et al."A numerical study of island wakes in the Xisha Archipelago associated with mesoscale eddies in the spring".OCEAN MODELLING 139(2019):UNSP 101406.
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