Seafloor deposits and deformations in shallow marine areas of a paleo-glacial area revealed by side-scan sonar data: a case study from Horseshoe Island, Western Antarctica

Abstract Advances in marine geophysical imaging, including high-resolution side-scan sonar and multibeam bathymetry integrated with ground-truthing methods (e.g., sediment sampling and underwater video observations), have substantially enhanced our ability to map submerged glacial landforms and reconstruct past ice-sheet dynamics. These techniques provide critical insights into ice-flow patterns, subglacial erosion, and sediment deposition—key processes for understanding both paleo-glaciation and the response of modern ice sheets to climate change. Despite these advances, nearshore environments, which preserve key evidence of past ice-sheet and ice-marginal processes, remain understudied in many regions of Antarctica. To address this gap, we present the first high-resolution geophysical and ground-truthing dataset from the western coast of Horseshoe Island (Western Antarctic Peninsula). This dataset integrates side-scan sonar imagery with underwater video observations to map nearshore erosional and depositional landforms at unprecedented resolution. The identified landforms provide new insights into past ice-flow dynamics and subglacial processes, thereby helping to constrain ice-sheet reconstructions and improve predictions of future change. Distinct morphological boundaries and erosion patterns indicate that meltwater streams have significantly influenced the seafloor, particularly at depths greater than 10 m, reflecting glacial–marine and ice-marginal environmental conditions in the recent past. Within a limited area, geophysical evidence reveals subglacially formed seafloor features, including remnants of a paleo-lake and its associated paleoshoreline, pointing to former subglacial hydrological activity. The orientation of meltwater channels and streamlined glacial landforms indicates a dominant southward paleo–ice flow. This interpretation is supported by greater seafloor incision and deeper bathymetry in the southern sector of the island compared to its western margin. Collectively, these observations advance reconstructions of ice-sheet dynamics by elucidating the role of subglacial and ice-marginal processes in shaping nearshore submarine geomorphology. The integration of high-resolution marine geophysical data with ground-truthing observations provides critical empirical constraints for numerical ice-sheet models and contributes to refining projections of Antarctica’s future contribution to global sea-level rise.