Revisit the vertical structure of the eddies and eddy‐induced transport in the Leeuwin Current system
|Author(s)||He Yinghui1, 2, Feng Ming3, Xie Jieshuo1, 2, He Qingyou1, 2, Liu Junliang1, 2, Xu Jiexin1, 2, Chen Zhiwu1, 2, Zhang Ying1, 2, Cai Shuqun1, 2, 4|
|Affiliation(s)||1 : State Key Laboratory of Tropical Oceanography South China Sea Institute of Oceanology CAS 164 West Xingang Road Guangzhou 510301, China
2 : Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou) Guangzhou, 511458 ,China
3 : CSIRO Oceans and Atmosphere Crawley Western Australia ,Australia
4 : University of Chinese Academy of Sciences Beijing100049, China
|Source||Journal of Geophysical Research: Oceans (2169-9275) (American Geophysical Union (AGU)), 2021-04 , Vol. 126 , N. 4 , P. e2020JC016556 (27p.)|
|Keyword(s)||Mesoscale eddy, Eddy vertical structure, Leeuwin Current, Eddy‐induced transport, Indian Ocean|
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 transports 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.