Revisit the Vertical Structure of the Eddies and Eddy‐Induced Transport in the Leeuwin Current System

The vertical structure of eddies in the Leeuwin Current system affects the eddy volume, heat, and salt transport, even the ecosystem. However, the understanding of eddy vertical structure and eddy‐induced transport here are still very limited. In this study, satellite observed sea surface heights we...

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Bibliographic Details
Published in:Journal of geophysical research. Oceans 2021-04, Vol.126 (4), p.n/a
Main Authors: He, Yinghui, Feng, Ming, Xie, Jieshuo, He, Qingyou, Liu, Junliang, Xu, Jiexin, Chen, Zhiwu, Zhang, Ying, Cai, Shuqun
Format: Article
Language:English
Subjects:
Altimeters
Current rings
Density
Drift
Drifters
Eddies
Eddy currents
Eddy kinetic energy
eddy vertical structure
eddyy‐induced transport
Floats
Geophysics
Heat
Heat transport
In situ measurement
Indian Ocean
Induction heating
Kinetic energy
Leeuwin Current
Life span
Mesoscale eddies
mesoscale eddy
Mesoscale phenomena
Mixed layer
Ocean circulation
Oceanographers
Oceans
Offshore
Potential energy
Salt advection
Salts
Satellite altimetry
Satellite observation
Satellites
Sea surface
Surface properties
Vertical profiles
Volume transport
Water masses
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Summary:The vertical structure of eddies in the Leeuwin Current system affects the eddy volume, heat, and salt transport, even the ecosystem. However, the understanding of eddy vertical structure and eddy‐induced transport here are still very limited. In this study, satellite observed sea surface heights were combined with decade‐long in situ measurements of Argo floats to study the vertical structure of mesoscale eddies in the LC system and their volume, heat, and salt transport. A novel eddy reconstruction method, which considers the influences of both the eddy and background flow, is devised to study the three‐dimensional structure of eddies. Result shows that, in LC system, anticyclonic eddies (AEs) are usually surface‐intensified, with the geostrophic velocity decreasing sharply below the mixed layer, while cyclonic eddies (CEs) are subsurface‐intensified, with a maximum speed at 240 m. The density anomaly core of the average AE (CE) is at a depth of 130 m (650 m) with a density anomaly of −0.51 (0.24) kg/m3. The volume‐integrated eddy kinetic energy and available potential energy of the average CE are much larger than those of the average AE. The average lifespan of CEs is significantly longer than that of AEs, which can be explained by the deeper vertical scale of CEs. The offshore volume transport by eddy drift across the coastal (107°E) section is 9.05 Sv (12.5 Sv). The heat and salt onshore transport by eddy drift across the coastal (107°E) section are, respectively, 10.6 Tw and 143.1 ton/s (17.1 Tw and 241.0 ton/s). Plain Language Summary Mesoscale eddies are ubiquitous in the ocean; their surface characteristics can be well observed by satellite altimetry, but most of their interior information is currently unclear. To understand the vertical structure of an eddy, previously, oceanographers have composited eddies based on satellite altimeter and Argo profile data. The present work has improved upon this method and associates the interior anomaly of an eddy with its surface amplitude and edge height. When we applied this method to the study of eddies off Western Australia, we found that the vertical structures of cyclonic eddies (CEs) and anticyclonic eddies (AEs) in this region are very different. In general, CEs are more energetic, have longer lifespans, and propagate farther than AEs, which could play a more important role in water mass redistribution and heat transport in the southeastern Indian Ocean. Key Points A new method for eddy reconstruction
ISSN:2169-9275
2169-9291
DOI:10.1029/2020JC016556