Vertical scales and dynamics of eddies in the Arctic Ocean's Canada Basin

A decade of moored measurements from the Arctic Ocean's northwestern Beaufort Gyre (collected as a component of the Beaufort Gyre Exploration Project) are analyzed to examine the range of mesoscale eddies over the water column and the dynamical processes that set eddy vertical scales. A total of 58 eddies were identified in the moored record, all anticyclones with azimuthal velocities ranging from 10 to 43 cm/s. These are divided into three classes based on core depths. Shallow eddies (core depths around 120 m) are shown to be vertically confined by the strong stratification of the halocline; typical thicknesses are around 100 m. Deep eddies (core depths around 1200 m) are much taller (thicknesses around 1300 m) owing to the weaker stratification at depth, consistent with a previous study. Eddies centered around mid-depths all have two cores (vertically aligned and separated in depth) characterized by velocity maxima and anomalous temperature and salinity properties. One core is located at the base of the halocline (around 200 m depth) and the other at the depth of the Atlantic Water layer (around 400 m depth). These double-core eddies have vertical scales between those of the shallow and deep eddies. The strongly decreasing stratification in their depth range motivates a derivation for the quasi-geostrophic adjustment of a nonuniformly stratified water column to a potential vorticity anomaly. The result aids in interpreting the dynamics and origins of the double-core eddies, providing insight into transport across a major water mass front separating Canadian and Eurasian Water.