The Three-Dimensional Structure of the Mesoscale Eddy in the Kuroshio Extension Region Obtained from Three Datasets

Abstract

The high-resolution observation data from June 2019, Argo data from 1997 to 2019, and the multi-observation ARMOR 3D dataset from 1993 to 2019 were used to study the three-dimensional (3D) structural characteristics of the mesoscale cyclonic eddy (CE) in the Kuroshio Extension region (KER). The observed eddy has a typical 3D structure of the KER CE, which was a longer lifespan eddy in this KER. The maximum anomalies of temperature and salinity were −7.69 °C and −0.71 PSU, which were located at the 350 m depth. In the vertical, the observed and composite eddy had a dipole structure, while ARMOR 3D had a monopole. The study of the velocity fields indicate that ARMOR 3D underestimates the velocity below 500 m. The 3D structures of the CE composite eddy of Argo were comparable to the observations, whereas the temperature and salinity anomalies were weaker than the observation. The surface of the Argo composite eddy shows a positive temperature anomaly within 50 m, which used to be opposite to the observation. This phenomenon was due to the limited Argo data of the composite eddy, and most of them were the observed profiles of winter CE in the weak years of EKE in the KER. We tried using ARMOR 3D to explore the reliability of ARMOR 3D composite eddy and compared the seasonal variations of temperature/salinity anomalies of the cyclonic and anticyclonic eddy. The anomalies of temperature and salinity caused by CE have seasonal variations: the anomalies have been strong in summer and weak in winter. This is consistent with the variant of eddy kinetic energy (EKE), but AE has no seasonal variation.