Meridional motion driven by kinematic viscosity &ngr; and thermal diffusivity &kgr; within a warm-core ring is examined. An analytic quasi-geostropic model is constructed that shows that the vertical mixing of heat or momentum is ineffective in driving secondary motion. Single-celled meridional flows will occur within the ring whenever the Prandtl number Pr=&ngr;h/&kgr;h is not equal to 1. When Pr is greater than 1, the flow is up in the ring core, while Pr less than 1 causes downward motion at ring center. A numerical primitive equation model leads to qualitatively identical results but shows that the secondary flow is not long-lived when Pr is less than 1, decaying within 2 months, while in the Pr greater than 1 case the flows are still vigorous at the end of the experiment (90 days).