AbstractAn Ocean Tidal Inverse Model for Antarctic Ice Shelves: Application to Amery Ice ShelfLaurie Padman, Helen Fricker, and Richard Coleman. We describe an inverse model for ocean tides around Antarctica including the ocean water cavities beneath the large ice shelves. The model uses assimilation of surface height data (TOPEX/Poseidon satellite altimetry over open water; coastal and benthic tide gauges; 3-D GPS on the ice shelves) to improve the tidal solution relative to existing global models. Non-assimilated data, including short GPS records and differential SAR interferometry on ice shelves, are used to assess model performance. We examine the tides of the Amery Ice Shelf (AIS) to illustrate the effect of data assimilation on the tidal solutions. The peak-to-peak tidal elevation change for the AIS is 1-2 m, although it can exceed 5 m during spring tides on the Filchner-Ronne and Larsen ice shelves in the Weddell Sea. The new model provides a tool for removal of these tidal signals from estimates of shelf ice displacements using SAR interferometry and satellite laser altimetry. We also obtain estimates of tidal currents that contribute to shelf ice melt, marine ice deposition, and iceberg calving and motion. While the data assimilation method helps overcome some of the difficulties that make tides difficult to predict near the Antarctic coast, two significant obstacles remain to a reliable circum-Antarctic tidal model: poor-quality model grids of bathymetry, including water column thickness under ice shelves; and lack of sufficient GPS data from ice shelves. We see the continued improvement of the BEDMAP water column thickness grid as an essential tool for tidal modeling. We also propose to develop and maintain a database of GPS records from all Antarctic ice shelves, that can be used in data assimilation and model validation studies. |