Forecast of paths of lenslike eddies in the ocean

There is increased interest in a specific type of mesoscale coherent ocean eddies in which velocity is maximum at depth, whereas no dynamic signal is measured on the ocean surface. These eddies are inseparably linked with lenses of anomalous water and are usually called intrathermocline eddies or, more broadly, lens-like eddies (LE). The analysis of lens transport by currents is complicated by the fact that there is little information on current velocities and directions at the depth of occurrence of the lenses. The authors propose the method of Lagrange invariants for a long-time forecasting of paths of lenslike eddies. A Lagrange invariant is a quantity which retains its value during the motion of a fluid parcel. At depths at which diffusive fluxes of heat, salt and momentum are, low, motion can be treated as adiabatic. Data on the distribution of most lenses in the North Atlantic is in good agreement with the predictions of their paths by the method of Lagrange invariants.