Validation of Spatial Boundary of the Ulleung Warm Eddy Using Altimetry

Ocean eddies play an important role in transferring and releasing thermal energy and momentum through horizontal and vertical advections.In order to understand their motions, the spatial boundaries are important to determine.Thus, this study validated the spatial boundaries of intrathermocline Ulleung Warm Eddy (UWE) as a case study.The surface spatial boundary was determined based on the Lagrangian Particle Tracking (LPT) method, which was evaluated based on subsurface thermal profile measurements collected by the National Institute of Fisheries Science (NIFS).We found that first, the surface spatial boundary was well determined by LPT when compared with the subsurface eddy shape determined by the isothermal 10C.The mean and standard deviation of the differences between surface and subsurface-based UWE boundaries are 7.70?4.71 km.Second, when there are some non-uniform thermal structures in the upper layer, it is difficult to determine the spatial boundary based on LPT.Third, potential capabilities to validate UWE boundary based on Surface Water Ocean Topography (SWOT) were examined.Since the Sea Surface Height Anomaly (SSHA) Level 4 data and SWOT are not comparable yet due to being non-fully calibrated up to now, it is difficult to confirm the spatial boundary of UWE using SWOT.?Overall, this study can suggest how the altimetry to detect ocean eddies using LPT may need subsurface thermal structures to determine eddy shape.