The tidal spectrum underneath Antarctic ice shelves

Abstract

A year‐long tidal record has been obtained from beneath the George VI Ice Shelf, Antarctica. An unusual feature of the record is a significant response in tidal species 3 to 7. These harmonics are practically absent from records further north on the west coast of the Antarctic Peninsula but are present in all tidal height records from George VI Sound. A strong ter‐diurnal signal also exists in the tidal currents under the ice shelf. Nonlinearity also occurs in the tidal motion of the Ronne and Ekström ice shelves but has not been reported from the Ross Ice Shelf. The tidal dynamics of several Antarctic ice shelves have therefore been modified by a region of strong nonlinear response to tidal forcing. If nonlinear tides in the semidiurnal band are present on the Ross Ice Shelf, they could account for difficulties in modeling the area's weak semidiurnal tides. An anelastic component in the deformation of the ice at the grounding line is tentatively proposed as the mechanism responsible. The positioning of recording pressure sensors in pairs on the seafloor and at the ice shelf base will allow this hypothesis to be tested and also provide a value for the power dissipated by tidally induced flexure at the grounding line.