Tidal dynamics of the Filchner-Ronne and Larsen C ice shelves from GPS observations and model assimilation

Some of the largest ocean tides in the world are found along the eastern coast of the Antarctic Peninsula and southern extent of the Filchner-Ronne ice shelf (FRIS) where the peak-to-peak tidal range can exceed 7 m. At present, however, our knowledge of the tides under these ice shelves is the most limited of any comparably-sized region on Earth. Mismodelled ocean tides and ocean tide loading propagate into satellite based measurements such as time-variable gravimetry (GRACE) and altimetry (e.g., ICESat), with present tide model uncertainties suggesting possible biases well above the measurement noise of these instruments. Recent exciting measurements have also demonstrated large tidally-driven modulations of ice shelf flow near the Rutford Ice Stream similar in appearance to those previously identified on the Brunt Ice Shelf over 1000 km away, suggesting such modulations may be widespread features and that ice shelves may play a larger role in ice stream flow modulation than previously thought. We propose to study the three dimensional tidal dynamics of the major Weddell Sea ice shelves, namely the FRIS and Larsen C ice shelves, through direct GPS measurements and assimilation into an Antarctic numerical tide model. Regional-scale validation of the improved numerical tide model will be undertaken using onshore GPS measurements of tidal loading. Our results will significantly reduce the systematic error component in geodetic data (e.g., GRACE, CryoSat, GPS) used for key studies in post-glacial rebound, ice shelf thinning and ice sheet mass balance, and improve understanding of the intriguing tidal modulations of ice flow and their driving mechanism(s).