Vertical Eddy Structure

Understanding the role of ocean eddies in the global climate system is one of the most important problems in physical oceanography. A landmark study by Chelton et al. (2011), investigated in detail the properties and propagation characteristics of nonlinear mesoscale eddies using satellite altimetry. Since that time, research has increasingly focused on understanding the internal structures of these ubiquitous features. An accurate knowledge of internal structure is crucial for understanding the impacts of these eddies on heat and volume transport, as well as clarifying their role in the bio-geo-chemical cycling. Several recent studies have focused on collocating altimetric observations with in situ measurements from Argo float profiles, leading to distinct empirical models for the idealized eddy structure.

Despite this observational progress, the dynamics governing these eddy features are almost completely unexplored. Theoretical models for deducing the interior structure from surface signals have not been compared to these empirical descriptions of eddies. Nor, for example, is it yet known whether the proposed empirical models will lead to eddies that propagate and evolve, according to the equations of motion, in a way that matches the altimetric observations. In particular, the ability of the eddy to trap fluid—both in the horizontal and in the vertical — is a dynamical property that depends on the degree of nonlinearity, propagation speed, vertical structure, and the background flow field. We builds on recent works by combining, for the first time, an enhanced observational analysis of three-dimensional eddy structures with a detailed investigation into their dynamics.