Damping and Phase Advance of the Tide in Western Hudson Bay by the Annual Ice Cover

Abstract

Abstract Admittance analysts of yearlong current meter records and tidal height data shows that the annual ice cover affects the tidal currents and heights in Hudson Bay. Along the west coast of the bay, the semidiurnal tidal current and height are reduced by 10% and arrive twenty minutes earlier in winter than in summer. The diurnal tide shows similar characteristics but its weaker signal does not produce as reliable and consistent results. A simple theory of a rejecting Kelvin wave in a rectangular bay predicts that the extra damping by the ice cover causes the amphidromic points to move towards the shore along which the reflecting wave travels. Thus during the winter one sees relatively more of the incident wave than the reflected wave which causes a phase advance while the sum of their amplitudes decreases. Although further numerical modeling is required to determine the exact increase in linear damping coefficient caused by the ice cover, the simple analytical theory estimates it to be of the same order of magnitude as that caused by bottom friction.