Ship Routing Through Altimetry-Derived Ocean Currents

We investigate the potential of strategic ship routing through dynamic currents derived from satellite altimetry by simulating current patterns in a dynamic Gulf Stream region to reflect present and improved current estimation capabilities, using dynamic programming to determine approximately 3-day routes through the current patterns, and estimating relative fuel savings that would be obtained if a 16-knot ship followed these rather than great circle routes. When simulating the use of a modified hydrographic approach to derive directly-gridded current velocities from an orbiting altimeter, reflective of present capabilities, an average fuel savings of 2.5% is calculated over 486 simulated voyages. A 5.8% average fuel savings is calculated when the bias associated with the modified hydrographic estimation approach is eliminated but the spatial–temporal sampling limitation associated with satellite orbits remains. Eliminating both the bias and the sampling limitation, which could be achieved with a current nowcasting model, produces 11.1% average fuel savings. Error-free forecasts lead to only slight marginal improvements over error-free nowcasts. Analysis by route characteristics indicates that the contribution of strategic routing is much better on with-current voyages— when the ship is traveling in the general direction of the primary current flow—than on counter-current voyages. We conclude that beneficial strategic routing through altimetry-derived current patterns is feasible using present capabilities on with-current voyages, but that overall performance and applicability would be substantially improved with the development of a current nowcasting model.