Recent findings underscore the significant role of submesoscale stirring in driving lateral leakage and vertical transport within mesoscale eddies. This study combines in-situ observations with submesoscale-permitting model data to analyze water mass variations along isopycnals, revealing distinct leakage patterns across various depth layers. Submesoscale stirring is identified as a primary driver of enhanced horizontal diffusivity, surpassing 100 m² s⁻¹ in the subsurface, as indicated by temperature-salinity analyses . Particle tracking experiments trace the pathways of lateral dispersion and vertical penetration, showing that submesoscale stirring promotes efficient lateral leakage in the mixed layer, while intensifying vertical transport in the subsurface. Our results suggest that submesoscale instabilities significantly impact along-isopycnal eddy leakage in the mixed layer. In contrast, mesoscale coherence persists in the subsurface, where internal-wave shear is the dominant mechanism for isopycnal stirring, leading to eddy disruption and enhanced vertical exchange. These findings highlight the distinct roles of submesoscale processes both within and below the mixed layer, emphasizing their critical influence on lateral and vertical tracer dispersion and the eddy’s overall capacity for water mass retention.

submesoscale stirring; vertical exchange; eddy leaking