Observed Tidal Currents in Prydz Bay and Their Contribution to the Amery Ice Shelf Basal Melting

Abstract

Tides play a key role in regulating the circulation and water properties around Antarctica, yet tidal currents and the corresponding influences in Prydz Bay have not been quantified with observational datasets. This study focuses on the observed characteristics of tidal currents and quantifies the tidal contribution to the basal melting of the Amery Ice Shelf (AIS). Long-term hydrography observations are provided by 10 moorings over the continental shelf and 6 borehole sites drilled through the AIS. Based on the mooring observations, we analyze the observed tidal currents, and evident seasonality in the mixed diurnal–semidiurnal tidal currents is identified. Barotropic tides dominate the tidal currents at the AIS front, except at the western corner where the seabed is abruptly deeper. The spatially and temporally averaged magnitude of tidal currents for all the current meter records is only ~3 cm s −1 . However, an observed maximum tidal velocity of ~11 cm s −1 occurs at the AIS front, and the maximal time-averaged tidal kinetic energy reaches ~31% of the total kinetic energy over the outer continental shelf. Based on the borehole observations, tide-like pulsing is identified in the ocean layer adjacent to the AIS basal surface. The maximal tidal contribution of the AIS basal melting is estimated at 69% based on a simple model. Due to the paucity of long-term velocity observations in the sub-ice-shelf cavity, the uncertainties of the estimated tide-induced melting in this study could be attributed to the simulated velocity.