Spatial variations of eddy vertical structure and energy in the southeastern Indian Ocean

Satellite observations demonstrate that mesoscale eddies are active and show significant spatial variability of surface features in the southeastern Indian Ocean (SEIO). Combining the satellite observation and Argo floats data, this study reveals the spatial variation of eddy vertical structure and volume-integrated energy in the SEIO. The sources of surface-intensified and subsurface-intensified eddies correspond well to the mean current systems. The surface-intensified cyclonic eddies (CEs) mainly originate from the South Indian Countercurrent system, whose density core is at a depth of ≈70 m, and subsurface-intensified CEs mainly originate from the Leeuwin Current system (LCS, ≈10° longitude off the eastern boundary of south Indian Ocean) and the SEIO interior south of 30°S, whose density core and maximum velocity are at depths of ≈750 m and ≈290 m, respectively. The surface-intensified anti-cyclonic eddies (AEs) widely originate from the entire region of SEIO, whose density core is at a depth of ≈110 m, while the sources of subsurface-intensified AEs only scatter in a few regions. The eddy lifespan in the SEIO is significantly correlated with the eddy volume-integrated energy. The most important factor affecting the spatial variability of eddy energy in the SEIO is eddy vertical structure, followed by the eddy amplitude. Finally, by investigating the performance of two reanalysis data in eddy statistical properties, we find that the biases of eddy lifespan and movement distance in the LCS is caused by the bias of eddy vertical structure. This further confirms the impact of the eddy vertical structure on the eddy evolution.