Seismic oceanography reveals water column structure offshore East Antarctica

Abstract Seismic oceanography provides high-resolution imaging of thermohaline structure in the ocean interior, yet its application remains limited in the Southern Ocean, where direct oceanographic observations are sparse despite the region’s importance for ice-sheet stability and global overturning circulation. Here we integrate approximately 230 km of multichannel seismic reflection data acquired during the 2022 COLLAPSE expedition offshore George V Land (East Antarctica) with XBT/XCTD observations, vessel-mounted ADCP measurements, Argo profiles and the GLORYS ocean reanalysis to investigate the upper-ocean structure across the continental rise in East Antarctica. Seismic processing optimized for water-column imaging reveals laterally coherent reflections associated with thermohaline interfaces and delineates a sharp frontal transition corresponding to the southern boundary of the Antarctic Circumpolar Current (ACC). Quantitative comparison demonstrates that the reconstructed temperature field is consistent with the available oceanographic observations. The study identifies an energetically active frontal environment characterized by strong lateral thermohaline gradients, coherent undulating reflectors consistent with internal-wave-like deformation, and steeply inclined thermohaline interfaces associated with frontal strain and shear. This study provides the first integrated seismic and oceanographic characterization of the southern ACC boundary offshore George V Land and demonstrates how multichannel seismic reflection data can bridge the spatial limitations of conventional oceanographic sampling. These results establish seismic oceanography as an effective tool for investigating frontal structure and water-mass variability in data-sparse Antarctic regions and provide a new regional perspective on upper-ocean dynamics relevant to ocean heat transport toward the East Antarctic margin.