Asymmetric vertical structure of mesoscale eddies in the Kuroshio Extension region

Abstract:

The Kuroshio Extension (KE) region in the Northwestern Pacific Ocean is one of the most eddy-energetic regions of the global ocean. In the past decades, much has been investigated about surface eddy characteristics, propagation properties, and horizontal kinematic structures in the KE region by in situ observations, satellite altimetry measurements, and infrared imagery. With more and more observation data accumulated in recent years, many studies apply composite analyses to multi-platform observations to construct eddy structure and associated heat and salt transports. Some recent studies reported different vertical structures of mesoscale eddies on each side of the KE. Eddies south of the KE tend to be subsurface intensified, while eddies north of the KE are surface intensified. This asymmetry of eddy vertical structure across the KE is not expected from the classical baroclinic instability theory. Based on a composite analysis of 20 years of satellite altimetry data and Argo profile data, as well as 4 years of eddy-resolving Community Earth System Model (CESM) simulation, we attempt to probe some of the reasons for the asymmetry of eddy vertical structure.