Assumptions related to the feasibility of ocean acoustic tomography are investigated utilizing range-dependent sound-speed profiles. The models include a warm midocean eddy and a cold core Gulf Stream ring superposed on a latitudinal geographic variation covering 1000 km. The results show that changes in the acoustic travel times produced by mesoscale features can be nonlinear, that the ray paths are substantially displaced by a mesoscale eddy, and that information from a single source and receiver can be used to infer the distance to a mesoscale disturbance.