Variability in spatial patterns of long nonlinear waves from fast ferries in Tallinn Bay
- 1Bergen Center for Computational Science, UNIFOB, University of Bergen, Thormøhlensgate 55, 5008 Bergen, Norway
- 2Center for Nonlinear Studies, Institute of Cybernetics, Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn, Estonia
- 3Department of Nonlinear Geophysical Processes, Institute of Applied Physics, Russian Academy of Sciences, 46 Uljanov Street, Nizhny Novgorod, 603950, Russia
- 4School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland 4811, Australia
Abstract. High-speed ferries are known to generate wakes with unusually long periods, and occasionally large amplitudes which may serve as a qualitatively new forcing factor in coastal regions that are not exposed to a sea swell. An intrinsic feature of such wakes is their large spatial variation. We analyze the variability of wake conditions for the coasts of Tallinn Bay, the Baltic Sea, a sea area with very intense fast ferry traffic. The modelled ship wave properties for several GPS-recorded ship tracks reasonably match the measured waves in terms of both wave heights and periods. It is shown that the spatial extent of the wake patterns is very sensitive to small variations in sailing conditions. This feature leads to large variations of ship wave loads at different coastal sections with several locations regularly receiving high ship wave energy. The runup of the largest ship wakes on the beach increases significantly with an increase in wave height whereas shorter (period <2–5 s) waves merge into longer waves in the shoaling and runup process.