The ocean tide and waves beneath the Ross ice shelf, Antarctica

Widely spaced tidal gravity records have been used to determine the spatial and temporal variation of the ocean tide beneath the Ross Ice Shelf. Cotidal-coamplitude maps have been drawn for the six greatest harmonic constituents of the tide. These are K₁, P₁, O₁, M₂, S₂, and N₂. The tide is principally diurnal, the diurnal amplitudes being roughly 3 times longer than the semidiurnals. The range of the tropic tide is about 1 m at the northern extremity of the ice shelf, and can be as great as 2 m in the southeastern part of the region. The diurnal constituents can each be viewed as a wave that propagates towards the southwest across the sea, having an amplitude that is closely related to the thickness of the water-layer beneath the ice. For each of the semidiurnal constituents there is an amphidromic region located within the Ross 5ea near 80° S latitude, 1900 W longitude, and having a clockwise sense of rotation.

Theoretical calculations of the tidal current indicate that the semidiurnal and diurnal current constituents have roughly the same amplitude. The semidiurnal current is magnified by near resonance with the inertia current due to the high latitude of the sea. Because of the resonance, calculations of the semidiurnal components of the tidal current are sensitive to the treatment of the retarding effects of the ice shelf and sea floor.

Waves having periods shorter than 20 min were observed in the ice shelf. These have been identified as flexural waves that are generated by the action of the ocean swell on the northern edge of the shelf. The observed speed of these waves was predicted within the uncertainty of the measurement by the classical flexural wave theory.