Compact, intrathermocline eddies in the Sargasso Sea

We report observations of isolated lenses of constant‐temperature water embedded in the permanent thermocline in the Sargasso Sea. These features are observed to have vertical extents of ≲220 m, horizontal dimensions of ≲65 km, and residence depths near 700 m. A dynamic model is constructed which permits a balance among the pressure gradient, Coriolis, and cyclostrophic forces and maintains the lens against gravitational collapse. A result is that anticyclonic rim velocities approaching 20 cm s −1 are permitted and that these eddies have finite radii of the order of 50 km, at which their thicknesses fall to zero.