Effect of landfast sea ice on coastal currents driven by the wind

The present study examines the effects of landfast sea ice on the response of a homogeneous coastal ocean to wind forcings under the longwave approximation. For a fluctuating wind, continental shelf waves are induced by an infinite stress curl due to the existense of the ice edge as well as by the torque due to the topographic change. The amplitude and sign of each shelf wave mode excited by the forcing depend strongly on the ice edge location. The alongshore velocity field, which can be represented as the sum of all the shelf wave modes, has a maximum in amplitude at the ice edge with a strong lateral shear, which is a result of the infinite stress curl. The amplitudes of alongshore velocity and sea level near the coast are greatly reduced as the ice edge advances. The response to a steady wind is also examined, and it is found that even for the same wind, the velocity distributions depend strongly on the ice edge location. For instance, the current direction near the coast is the same as that of the wind stress in the case of no fast ice, whereas it is opposite in the case where the ice edge is located at the shelf break. The present theory is applied to the continental shelf off Enderby Land, Antarctica, and it gives the possible explanation for the observed features that the current variability its coherence with the wind, and the prevailing current direction depend much on the extent of landfast sea ice.