Slowly drifting sea ice with a corrugated underside

The oceanic mass transport induced by wind-driven sea ire with a corrugated bottom is investigated theoretically by using a Lagrangian description of motion. The bottom corrugations are sinusoidal with infinitely long crests and small amplitudes. The ice drift is rectilinear and slow enough fur a su itably defined fluid Reynolds number R to be small. The solutions are writt en as a 2-parameter expansion in R and the nondimensional corrugation ampli tude epsilon. The solutions to O(R(1)epsilon(2)) yield the interaction betw een the basic Ekman current and the nonlinear displacement field due to the corrugations. The steady mean solution to this order is obtained, and the results are discussed for various angles between the ice-drift velocity vec tor and the bottom striations as well as for various ratios between the cor rugation wavelength and the Ekman depth. The deflection angle alpha between the ice-drift direction and the wind stress that drives the ice is compare d to the corresponding angle alpha(0) for flat-bottomed ice. For thin ice w ith negligible internal friction, it is found that alpha > alpha(0) for non dimensional corrugation wave numbers larger than 2.23. In this case alpha h as a maximum when the drift vector is 22.5 degrees to the left of the stria tions (in the Northern Hemisphere). For smaller wave numbers one may have a lpha < alpha(0), with a minimum value for alpha when the motion of the ice is 22.5 degrees to the left of the cross-striation direction. For thicker i ce and nonnegligible internal friction, maximum and minimum deflection angl es are still related to drift directions that are 90 degrees out of phase, but maximum deflection angles now occur for drift directions somewhat large r than 22.5 degrees to the left of the striations.