The shape of ice-shelf cavities are a major source of uncertainty in understanding ice-ocean interactions. This limits assessments of the response of the Antarctic ice sheets to climate change. Here we use vibroseis seismic reflection surveys to map the bathymetry beneath the Ekström Ice Shelf, Dronning Maud Land. The new bathymetry reveals an inland-sloping trough, reaching depths of 1100 m below sea level, near the current grounding line, which we attribute to erosion by palaeo-ice streams. The trough does not cross-cut the outer parts of the continental shelf. Conductivity-temperature-depth profiles within the ice-shelf cavity reveal the presence of cold water at shallower depths and tidal mixing at the ice-shelf margins. It is unknown if warm water can access the trough. The new bathymetry is thought to be representative of many ice shelves in Dronning Maud Land, which together regulate the ice loss from a substantial area of East Antarctica.

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 Qaidam Basin (QB) in the northeastern Tibetan Plateau held a mega-lake system during the Pliocene. Today, the lower elevations in the basin are hyperarid. To understand the mechanisms behind this system change, we applied the Weather Research and Forecasting model for dynamical downscaling of ECHAM5 global climate simulations for present-day (PD) and mid-Pliocene (PLIO) conditions. In PLIO, the annual water balance (∆S) of the QB is higher than that in PD, resulting from a stronger moisture influx across the western border in winter, spring, and autumn and a weaker moisture outflux across the eastern border in summer. The atmospheric water transport across both borders is influenced by the mid-latitude westerlies throughout the year. The jet stream over the QB is stronger in PLIO in winter, spring, and autumn, causing stronger moisture input at the basin’s western border in these seasons. In summer, the jet strength over the QB decreases in PLIO. Meanwhile, the East Asian Summer Monsoon (EASM) intensifies and migrates to the Northwest, transporting moisture into the QB. Thus, the weaker moisture output through the eastern border in summer is a combined result of weakened jet strength and the strengthening of the EASM. Therefore, the differences in ∆S between PLIO and PD are coupled with changes in the mid-latitude westerlies and the EASM. Given that the mid-Pliocene climate is an analog of the projected warm climate of the near future, our study contributes to a better understanding of the impacts of climate change in Central Asia.

Improving constraints on the basal ice/bed properties is essential for accurate prediction of ice-sheet grounding-line positions and stability. Furthermore, the history of grounding-line positions since the Last Glacial Maximum has proven challenging to understand due to uncertainties in bed conditions. Here we use a 3D full-Stokes ice-sheet model to investigate the effect of differing ocean bed properties on ice-sheet advance and retreat over a glacial cycle. We do this for the Ekström Ice Shelf catchment, East Antarctica. We find that predicted ice volumes differ by >50%, resulting in two entirely different catchment geometries triggered exclusively by variable ocean bed properties. Grounding-line positions between simulations differ by >100% (49 km), show significant hysteresis, and migrate non-steadily with long quiescent phases disrupted by leaps of rapid migration. These results highlight that constraints for both bathymetry and substrate geologic properties are urgently needed for predicting ice-sheet evolution and sea-level change.