This thesis examines the factors and mechanisms contributing to ice tongue persistence and stability in the western Ross Sea and investigates whether ice tongues can be used as sentinels of change. Concluding that fast ice persistence enhances ice tongue growth, delays ice tongue calving and acts as a protective mantle against ocean erosion and tidal forcing. Ice tongues at the fringes of the Antarctic Ice Sheet lose mass primarily through basal melting and calving, and they are found sporadically around the Antarctic coast but are ubiquitous in the western Ross Sea. They are sensitive to ocean conditions that can weaken the ice mechanically or through thinning. Ice tongues, which are laterally unconfined, are likely to be particularly sensitive to ocean-induced stresses.

Using novel satellite remote sensing methods, the basal mass balance of the ice tongues in the region was calculated, and the effect that fast ice has over ice tongue dynamics and mechanics is shown using two case studies. The basal mass change of twelve Antarctic ice tongues is calculated using a flux gate approach, deriving thickness from ICESat-2 height measurements and ice surface velocities from Sentinel-1 feature-tracking over the same time period (October 2018 to December 2021). The basal mass balance of ice tongues in the region was found to be between 􀀀0.14
0.07myr₋¹ and 􀀀1.50 1.2myr₋¹. The average basal mass change for all the ice tongues is 􀀀0.82 0.68mof ice yr₋¹. Low values of basal melt suggest a stable mass balance condition in this region, with low thermal ocean forcing. A heterogeneous basal melt pattern with no latitudinal gradient and no clear driver in basal melt was found, indicating that that a cold coastal current is most likely the cause for the ice tongue persistence in the region and that local processes are crucial for their stability.

The fast ice influence on ice tongues was investigated in two studies: (i) the unprecedented calving event of the Parker Ice Tongue, and (ii) a three-year time series (2017-2020) of interferometric synthetic aperture radar (InSAR) and differential InSAR, which was used to study the lateral flexure of the 10 km long Erebus Ice Tongue as a result of ocean currents. It was found that fast ice can influence the dynamics and mechanics of ice tongues, promoting growth and hindering calving when present. Before the Parker Ice Tongue calving, the observations showed that during the short summer period, characterised by decreased fast ice extent, the ice tongue showed around 11% higher velocities than in winter. While the lateral flexure study done over the Erebus Ice Tongue indicated that the average flexure of the ice tongue was two times higher when fast ice was absent, than when embedded in fast ice. It also presented a significant correlation between flexure and tidal currents found when fast ice was absent. An analytical model tuned to observations suggests that even without sea ice for stabilisation, the lateral bending stresses induced by the ocean are insufficient to cause calving without additional amplifying factors.

Due to the unconfined nature of ice tongues, they are subject to the mercy of oceanographic processes and changes in ocean water properties. This research highlights the vulnerability of ice tongues once exposed to ocean currents, which poses the following question: what will be the fate of such magnificent glaciological features with future changes in fast ice cover and ocean conditions?