Dynamics of polar outlet glaciers vary with ocean tides, providing a natural laboratory to understand basal processes and ice rheology. We apply Terrestrial Radar Interferometry to close the spatiotemporal gap between GNSS and satellite observations. Three-hour flowfields collected over an eight day period at Priestley Glacier, Antarctica, validate and provide the spatial context for concurrent GNSS measurements. Ice flow is fastest during falling tides and slowest during rising tides. Principal components of the timeseries prove upstream propagation of tidal signatures $>$ 10 km away from the grounding line. Hourly, cm-scale horizontal and vertical flexure patterns occur $>$6 km upstream of the grounding line. Vertical uplift upstream of the grounding line is consistent with ephemeral re-grounding during low-tide impacting grounding-zone stability. Taken together, these observations identify tidal imprints on ice-stream dynamics on new temporal and spatial scales providing constraints for models designed to isolate dominating processes in ice-stream mechanics.

The full length of Parker Ice Tongue on the Victoria Land Coast, Antarctica, calved in March 2020. Calving of this magnitude (18 km) is not previously seen for this location. The mean growth rate (189 m yr-1) indicates that it is now at a historic minimum for at least the last 165 years. The 2020 calving occurred during a complete breakout of the land-fast sea ice. Here we link seasonal changes in ice velocity to the land-fast sea ice extent. With Summer/winter increase/decrease in velocity correlates with decrease/increase in land-fast sea ice extent (-0.62 with R-squared of -0.39). Although Parker Ice Tongue was relatively small compared to other ice tongues in the region, its sensitive behaviour highlights the vulnerability of ice tongues to a changing ocean environment, and poses questions about the future stability of larger floating ice masses if land-fast sea ice extent decreases more broadly in the future.