Influence of tides and tidal current on Mertz Glacier, Antarctica

Abstract

Abstract Mertz Glacier, East Antarctica, is characterized by a 140 km long, 25 km wide floating ice tongue. In this paper, we combine a large number of remotely sensed datasets, including in situ global positioning system measurements, satellite radar altimetry, airborne radio-echo sounding and satellite synthetic aperture radar imagery and interferometry. These various datasets allow us to study the interaction of the ice tongue with the tides and currents. However, the inverse barometer effect needs to be applied to sea-level variations affecting the tongue. We find that the tide-induced currents exert a small lateral pressure on the tongue which, when integrated over the large surface of the tongue, induce a flexure of up to 2 m amplitude per day. Simple elastic modelling of the flexure confirms the observations and helps validate the boundary conditions necessary to explain different eastward and westward tongue deflections. In addition, the along-flow velocity of the tongue does vary daily from 1.9 to 6.8 md -1 depending on the tidal current. When the current pushes the tongue toward the eastern boundary of the fjord, the tongue is retarded by the drag and the velocity decreases. The accumulated stress is released, allowing the tongue to flow very rapidly when the current pushes the tongue westward. These forcing and boundary conditions on the floating ice flow are important and must be taken into account when studying glacier discharge and calving.