Low carbon intensity routes via ocean currents and waves

The VISIR ship routing model is augmented with the capability to employ, on top of waves, also ocean currents for optimising vessel routes. A case study for a cargo vessel sailing between the Chesapeake Bay (USA) and Lisbon (Portugal) is considered. The seasonal variability of the route pattern is visualised, with the major ocean boundary current impacting in a specific way, depending on the prevailing sailing direction. In the approximation of CO2 emissions proportional to sailing time, the impact on the Energy Efficiency Operational Indicator (EEOI) proposed by the International Maritime Organization is also computed. The seasonal variability of EEOI demonstrates, for a given parametrisation of vessel energy loss in waves, potential savings in the 3-12% range, with respect to navigation along a least-distance route, and in the 1-5% range, with respect to navigation along a least-time route which neglects the role of ocean currents. These figures refer to monthly mean values, while individual routes may exhibit EEOI savings up to 20% and 6%, respectively.