Notes on translatory movement of rings of current with application to Gulf Stream eddies

Abstract

Cyclonic eddies detached from the Gulf Stream are much like rings of current encircling central regions with small relative velocity. Such rings have a tendency to move through an environment at rest on account of (1) meridional variation in Coriolis parameter, (2) unevenness in width or velocity profile around the ring, and (3) slope in the bottom. First-order formulas are developed for displacement speeds and eddy shapes constant in time (circles) through elementary but not fully rigorous calculations. Baroclinicity is included in the sense that large vertical shear in the basic horizontal velocity is emphasized, but thermal-wind effects arising from the required vertical motions are ignored. Some tenuous comparisons are made with observations of the behaviour of eddies detached from the Stream.