The Antarctic marginal ice zone (MIZ) is a highly dynamic region where ocean surface waves interact with sea ice, influencing exchanges between the ocean, atmosphere, and ice cover. However, the importance of wave–ice interactions for Antarctic sea ice evolution remains poorly quantified. We combine satellite observations of wave penetration with standalone WaveWatch III simulations to develop an observationally constrained definition of the Antarctic MIZ. This definition is then applied within a newly developed fully coupled wave–ocean–sea ice configuration of ACCESS-OM3, which represents wave-induced sea-ice fracture through a prognostic floe size distribution that feeds back on wave attenuation and upper-ocean mixing. Using this framework, we investigate regional variability in Antarctic MIZ extents and assess the influence of wave–ice interactions on sea-ice evolution. Sea-ice concentration tendency diagnostics are used to examine the relative roles of dynamic and thermodynamic processes in the MIZ, while comparisons between standalone and fully coupled wave simulations isolate the effects of wave coupling. This work provides an observationally constrained framework for investigating the role of wave–ice interactions in Antarctic sea ice evolution.

Observational gaps across the ocean– sea ice– atmosphere system limit our understanding of the rapidly changing dynamics of the East Antarctic Marginal Ice Zone (EAMIZ) and its influence on the Southern Ocean and the wider Earth system. These gaps contribute to the incomplete representation of MIZ processes in climate and Earth system models, leading to large uncertainty in predictions of future sea-ice coverage and conditions, impacts on Southern Ocean properties, ecosystems, weather, and climate, including impacts for Australia. This talk will summarise the objectives and current planning for an Australian-led research voyage to study coupled physical-biological-biogeochemical processes and feedback mechanisms in the EAMIZ during the winter-spring (August to October) transition in 2028. Through coordinated under-, intra-ice and above-ice observations the EAMIZ voyage will help improve the mechanistic understanding needed to explain recent sea ice changes and to anticipate future states of the Southern Ocean system, and their impacts, with greater confidence. The talk will also describe pathways to link the EAMIZ study with the international Antarctica InSync initiative.

In Antarctica, baleen whales feed heavily on swarms of Antarctic krill, however krill swarm behaviour may vary seasonally influencing their availability to krill predators. Swarm behaviour may be driven by abiotic factors such as light penetration to the water column, or sea ice cover, as well as biotic factors such as predator presence, yet the temporal influence of these drivers remains elusive for remote regions such as East Antarctica. Here, we use a time series of active and passive acoustic data from an autonomous platform, to assess the seasonal interactions between krill swarms – observed using active acoustics-, their environment and multiple species of large krill predators: Antarctic blue whales (Balaenoptera musculus intermedia), fin whales (Balaenoptera physalus quoyi) and Antarctic minke whales (Balaenoptera bonaerensis) – observed using passive acoustics. Patterns between different whale calls, krill swarm properties and environmental parameters including light and sea ice cover revealed clear summer and winter regimes demonstrating swarms are not uniformly preyed upon year-round. We suggest the low degree of overlap in different whale calls throughout the year reflects the feeding ecology and morphology of large Antarctic blue whales and smaller Antarctic minke whale species. Krill swarm density and depth were predominantly explained by seasonal and diel timings with some influence from solar irradiance and sea ice cover but were forcings but unaffected by predator vocalisations.

Sea ice thermodynamics is strongly influenced by overlying snow cover, yet this effect is often simplified in climate models, which historically assume a uniform snow distribution in winter and bare ice conditions in summer. Here, using shipborne, high-resolution, close-range imagery of the sea ice surface, visual observations, and concurrent atmospheric data from five expeditions in the Antarctic marginal ice zone (2019--2024), we demonstrate that snow cover persists year-round and exhibits strong heterogeneity. When incorporated into flux calculations, this heterogeneity modifies the effective surface energy exchange, leading to systematic departures from model predictions. The results suggest that representing sub-grid snow distribution is essential to capture Antarctic sea ice evolution and broader polar climate feedback.