Passive acoustic signatures of frontal ablation at tidewater glaciers in the Antarctic Peninsula and Greenland

Tidewater glaciers in the Arctic and the Antarctic Peninsula are undergoing an unprecedented level of retreat owing to rising temperatures, driven by both ocean-induced melting and atmospheric warming of ice-sheets. Frontal ablation at tidewater glaciers occurs primarily through calving and submarine melting, each of which generates distinct sounds that can be detected using acoustic sensing. Calving generates impulsive transient sounds associated with the impact of the ice on the ocean surface, whereas submarine melting generates a more persistent acoustic signal due to release of pressurized bubbles trapped within the ice. These characteristics provide the opportunity to remotely monitor glacier frontal ablation over a long term using passive acoustics, and complement other modalities of glacial remote sensing. To better understand the physical acoustic variability in glacial bays, we undertook acoustic recordings in tidewater glacier bays in Greenland and the Antarctic Peninsula in 2024-2025 using a long vertical hydrophone array, which allows discrimination of sound emanating from glacier terminus melt. These measurements reveal the directionality of the melt-induced sound field, wide variation in acoustic levels and spatial, temporal and spectral characteristics in the acoustic field in the different glacial bays, and significant contributions from melting ice mélange. These were coupled with conductivity-temperature-depth measurements to understand the effect of thermohaline structure on the melt-induced acoustic field. We investigate the acoustic field characteristics including the directionality, spectrum and coherence, potential links with the water temperature in the bay, and place our findings in the context of earlier passive acoustic studies conducted in Svalbard during 2019-2023, drawing comparisons and contrasts across polar regions. Together, these advance the use of passive acoustics as a tool for long-term, remote monitoring of tidewater glacier ablation.