  Eddy detection is a critical task for ocean scientists to understand and
analyze ocean circulation. In this paper, we introduce a hybrid eddy detection
approach that combines sea surface height (SSH) and velocity fields with
geometric criteria defining eddy behavior. Our approach searches for SSH minima
and maxima, which oceanographers expect to find at the center of eddies.
Geometric criteria are used to verify expected velocity field properties, such
as net rotation and symmetry, by tracing velocity components along a circular
path surrounding each eddy center. Progressive searches outward and into deeper
layers yield each eddy's 3D region of influence. Isolation of each eddy
structure from the dataset, using it's cylindrical footprint, facilitates
visualization of internal eddy structures using horizontal velocity, vertical
velocity, temperature and salinity. A quantitative comparison of Okubo-Weiss
vorticity (OW) thresholding, the standard winding angle, and this new
SSH-velocity hybrid methods of eddy detection as applied to the Red Sea dataset
suggests that detection results are highly dependent on the choices of method,
thresholds, and criteria. Our new SSH-velocity hybrid detection approach has
the advantages of providing eddy structures with verified rotation properties,
3D visualization of the internal structure of physical properties, and rapid
efficient estimations of eddy footprints without calculating streamlines. Our
approach combines visualization of internal structure and tracking overall
movement to support the study of the transport mechanisms key to understanding
the interaction of nutrient distribution and ocean circulation. Our method is
applied to three different datasets to showcase the generality of its
application.
